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[SOURCE: https://en.wikipedia.org/wiki/Computer_sciences] | [TOKENS: 4631] |
Contents Computer science Computer science is the study of computation, information, and automation. Included broadly in the sciences, computer science spans theoretical disciplines (such as algorithms, theory of computation, and information theory) to applied disciplines (including the design and implementation of hardware and software). An expert in the field is known as a computer scientist. Algorithms and data structures are central to computer science. The theory of computation concerns abstract models of computation and general classes of problems that can be solved using them. The fields of cryptography and computer security involve studying the means for secure communication and preventing security vulnerabilities. Computer graphics and computational geometry address the generation of images. Programming language theory considers different ways to describe computational processes, and database theory concerns the management of repositories of data. Human–computer interaction investigates the interfaces through which humans and computers interact, and software engineering focuses on the design and principles behind developing software. Areas such as operating systems, networks and embedded systems investigate the principles and design behind complex systems. Computer architecture describes the construction of computer components and computer-operated equipment. Artificial intelligence and machine learning aim to synthesize goal-orientated processes such as problem-solving, decision-making, environmental adaptation, planning and learning found in humans and animals. Within artificial intelligence, computer vision aims to understand and process image and video data, while natural language processing aims to understand and process textual and linguistic data. The fundamental concern of computer science is determining what can and cannot be automated. The Turing Award is generally recognized as the highest distinction in computer science. History The earliest foundations of what would become computer science predate the invention of the modern digital computer. Machines for calculating fixed numerical tasks such as the abacus have existed since antiquity, aiding in computations such as multiplication and division. Algorithms for performing computations have existed since antiquity, even before the development of sophisticated computing equipment. Wilhelm Schickard designed and constructed the first working mechanical calculator in 1623. In 1673, Gottfried Leibniz demonstrated a digital mechanical calculator, called the Stepped Reckoner.[failed verification] Leibniz may be considered the first computer scientist and information theorist, because of various reasons, including the fact that he documented the binary number system. In 1820, Thomas de Colmar launched the mechanical calculator industry[note 1] when he invented his simplified arithmometer, the first calculating machine strong enough and reliable enough to be used daily in an office environment. Charles Babbage started the design of the first automatic mechanical calculator, his Difference Engine, in 1822, which eventually gave him the idea of the first programmable mechanical calculator, his Analytical Engine. He started developing this machine in 1834, and "in less than two years, he had sketched out many of the salient features of the modern computer". "A crucial step was the adoption of a punched card system derived from the Jacquard loom" making it infinitely programmable.[note 2] In 1843, during the translation of a French article on the Analytical Engine, Ada Lovelace wrote, in one of the many notes she included, an algorithm to compute the Bernoulli numbers, which is considered to be the first published algorithm ever specifically tailored for implementation on a computer. Around 1885, Herman Hollerith invented the tabulator, which used punched cards to process statistical information; eventually his company became part of IBM. Following Babbage, although unaware of his earlier work, Percy Ludgate in 1909 published the 2nd of the only two designs for mechanical analytical engines in history. In 1914, the Spanish engineer Leonardo Torres Quevedo published his Essays on Automatics, and designed, inspired by Babbage, a theoretical electromechanical calculating machine which was to be controlled by a read-only program. The paper 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, a prototype that demonstrated the feasibility of an electromechanical analytical engine, on which commands could be typed and the results printed automatically. In 1937, one hundred years after Babbage's impossible dream, Howard Aiken convinced IBM, which was making all kinds of punched card equipment and was also in the calculator business to develop his giant programmable calculator, the ASCC/Harvard Mark I, based on Babbage's Analytical Engine, which itself used punched cards and a central processing unit. When the machine was finished, some hailed it as "Babbage's dream come true". During the 1940s, with the development of new and more powerful computing machines such as the Atanasoff–Berry computer and ENIAC, the term computer came to refer to the machines rather than their human predecessors. As it became clear that computers could be used for more than just mathematical calculations, the field of computer science broadened to study computation in general. In 1945, IBM founded the Watson Scientific Computing Laboratory at Columbia University in New York City. The renovated fraternity house on Manhattan's West Side was IBM's first laboratory devoted to pure science. The lab is the forerunner of IBM's Research Division, which today operates research facilities around the world. Ultimately, the close relationship between IBM and Columbia University was instrumental in the emergence of a new scientific discipline, with Columbia offering one of the first academic-credit courses in computer science in 1946. Computer science began to be established as a distinct academic discipline in the 1950s and early 1960s. The world's first computer science degree program, the Cambridge Diploma in Computer Science, began at the University of Cambridge Computer Laboratory in 1953. The first computer science department in the United States was formed at Purdue University in 1962. Since practical computers became available, many applications of computing have become distinct areas of study in their own rights. Etymology and scope Although first proposed in 1956, the term "computer science" appears in a 1959 article in Communications of the ACM, in which Louis Fein argues for the creation of a Graduate School in Computer Sciences analogous to the creation of Harvard Business School in 1921. Louis justifies the name by arguing that, like management science, the subject is applied and interdisciplinary in nature, while having the characteristics typical of an academic discipline. This effort, and those of others such as numerical analyst George Forsythe, were successful, and universities went on to create such departments, starting with Purdue in 1962. Despite its name, a significant amount of computer science does not involve the study of computers themselves. Because of this, several alternative names have been proposed. Certain departments of major universities prefer the term computing science, to emphasize precisely that difference. Danish scientist Peter Naur suggested the term datalogy, to reflect the fact that the scientific discipline revolves around data and data treatment, while not necessarily involving computers. The first scientific institution to use the term was the Department of Datalogy at the University of Copenhagen, founded in 1969, with Peter Naur being the first professor in datalogy. The term is used mainly in the Scandinavian countries. An alternative term, also proposed by Naur, is data science; this is now used for a multi-disciplinary field of data analysis, including statistics and databases. In the early days of computing, a number of terms for the practitioners of the field of computing were suggested (albeit facetiously) in the Communications of the ACM—turingineer, turologist, flow-charts-man, applied meta-mathematician, and applied epistemologist. Three months later in the same journal, comptologist was suggested, followed next year by hypologist. The term computics has also been suggested. In Europe, terms derived from contracted translations of the expression "automatic information" (e.g. "informazione automatica" in Italian) or "information and mathematics" are often used, e.g. informatique (French), Informatik (German), informatica (Italian, Dutch), informática (Spanish, Portuguese), informatika (Slavic languages and Hungarian) or pliroforiki (πληροφορική, which means informatics) in Greek. Similar words have also been adopted in the UK (as in the School of Informatics, University of Edinburgh). "In the U.S., however, informatics is linked with applied computing, or computing in the context of another domain." A folkloric quotation, often attributed to—but almost certainly not first formulated by—Edsger Dijkstra, states that "computer science is no more about computers than astronomy is about telescopes."[note 3] The design and deployment of computers and computer systems is generally considered the province of disciplines other than computer science. For example, the study of computer hardware is usually considered part of computer engineering, while the study of commercial computer systems and their deployment is often called information technology or information systems. However, there has been exchange of ideas between the various computer-related disciplines. Computer science research also often intersects other disciplines, such as cognitive science, linguistics, mathematics, physics, biology, Earth science, statistics, philosophy, and logic. Computer science is considered by some to have a much closer relationship with mathematics than many scientific disciplines, with some observers saying that computing is a mathematical science. Early computer science was strongly influenced by the work of mathematicians such as Kurt Gödel, Alan Turing, John von Neumann, Rózsa Péter, Stephen Kleene, and Alonzo Church and there continues to be a useful interchange of ideas between the two fields in areas such as mathematical logic, category theory, domain theory, and algebra. The relationship between computer science and software engineering is a contentious issue, which is further muddied by disputes over what the term "software engineering" means, and how computer science is defined. David Parnas, taking a cue from the relationship between other engineering and science disciplines, has claimed that the principal focus of computer science is studying the properties of computation in general, while the principal focus of software engineering is the design of specific computations to achieve practical goals, making the two separate but complementary disciplines. The academic, political, and funding aspects of computer science tend to depend on whether a department is formed with a mathematical emphasis or with an engineering emphasis. Computer science departments with a mathematics emphasis and with a numerical orientation consider alignment with computational science. Both types of departments tend to make efforts to bridge the field educationally if not across all research. Philosophy Despite the word science in its name, there is debate over whether or not computer science is a discipline of science, mathematics, or engineering. Allen Newell and Herbert A. Simon argued in 1975, Computer science is an empirical discipline. We would have called it an experimental science, but like astronomy, economics, and geology, some of its unique forms of observation and experience do not fit a narrow stereotype of the experimental method. Nonetheless, they are experiments. Each new machine that is built is an experiment. Actually constructing the machine poses a question to nature; and we listen for the answer by observing the machine in operation and analyzing it by all analytical and measurement means available. It has since been argued that computer science can be classified as an empirical science since it makes use of empirical testing to evaluate the correctness of programs, but a problem remains in defining the laws and theorems of computer science (if any exist) and defining the nature of experiments in computer science. Proponents of classifying computer science as an engineering discipline argue that the reliability of computational systems is investigated in the same way as bridges in civil engineering and airplanes in aerospace engineering. They also argue that while empirical sciences observe what presently exists, computer science observes what is possible to exist and while scientists discover laws from observation, no proper laws have been found in computer science and it is instead concerned with creating phenomena. Proponents of classifying computer science as a mathematical discipline argue that computer programs are physical realizations of mathematical entities and programs that can be deductively reasoned through mathematical formal methods. Computer scientists Edsger W. Dijkstra and Tony Hoare regard instructions for computer programs as mathematical sentences and interpret formal semantics for programming languages as mathematical axiomatic systems. A number of computer scientists have argued for the distinction of three separate paradigms in computer science. Peter Wegner argued that those paradigms are science, technology, and mathematics. Peter Denning's working group argued that they are theory, abstraction (modeling), and design. Amnon H. Eden described them as the "rationalist paradigm" (which treats computer science as a branch of mathematics, which is prevalent in theoretical computer science, and mainly employs deductive reasoning), the "technocratic paradigm" (which might be found in engineering approaches, most prominently in software engineering), and the "scientific paradigm" (which approaches computer-related artifacts from the empirical perspective of natural sciences, identifiable in some branches of artificial intelligence). Computer science focuses on methods involved in design, specification, programming, verification, implementation and testing of human-made computing systems. Fields As a discipline, computer science spans a range of topics from theoretical studies of algorithms and the limits of computation to the practical issues of implementing computing systems in hardware and software. CSAB, formerly called Computing Sciences Accreditation Board—which is made up of representatives of the Association for Computing Machinery (ACM), and the IEEE Computer Society (IEEE CS)—identifies four areas that it considers crucial to the discipline of computer science: theory of computation, algorithms and data structures, programming methodology and languages, and computer elements and architecture. In addition to these four areas, CSAB also identifies fields such as software engineering, artificial intelligence, computer networking and communication, database systems, parallel computation, distributed computation, human–computer interaction, computer graphics, operating systems, and numerical and symbolic computation as being important areas of computer science. Theoretical computer science is mathematical and abstract in spirit, but it derives its motivation from practical and everyday computation. It aims to understand the nature of computation and, as a consequence of this understanding, provide more efficient methodologies. According to Peter Denning, the fundamental question underlying computer science is, "What can be automated?" Theory of computation is focused on answering fundamental questions about what can be computed and what amount of resources are required to perform those computations. In an effort to answer the first question, computability theory examines which computational problems are solvable on various theoretical models of computation. The second question is addressed by computational complexity theory, which studies the time and space costs associated with different approaches to solving a multitude of computational problems. The famous P = NP? problem, one of the Millennium Prize Problems, is an open problem in the theory of computation. Information theory, closely related to probability and statistics, is related to the quantification of information. This was developed by Claude Shannon to find fundamental limits on signal processing operations such as compressing data and on reliably storing and communicating data. Coding theory is the study of the properties of codes (systems for converting information from one form to another) and their fitness for a specific application. Codes are used for data compression, cryptography, error detection and correction, and more recently also for network coding. Codes are studied for the purpose of designing efficient and reliable data transmission methods. Data structures and algorithms are the studies of commonly used computational methods and their computational efficiency. Programming language theory is a branch of computer science that deals with the design, implementation, analysis, characterization, and classification of programming languages and their individual features. It falls within the discipline of computer science, both depending on and affecting mathematics, software engineering, and linguistics. It is an active research area, with numerous dedicated academic journals. Formal methods are a particular kind of mathematically based technique for the specification, development and verification of software and hardware systems. The use of formal methods for software and hardware design is motivated by the expectation that, as in other engineering disciplines, performing appropriate mathematical analysis can contribute to the reliability and robustness of a design. They form an important theoretical underpinning for software engineering, especially where safety or security is involved. Formal methods are a useful adjunct to software testing since they help avoid errors and can also give a framework for testing. For industrial use, tool support is required. However, the high cost of using formal methods means that they are usually only used in the development of high-integrity and life-critical systems, where safety or security is of utmost importance. Formal methods are best described as the application of a fairly broad variety of theoretical computer science fundamentals, in particular logic calculi, formal languages, automata theory, and program semantics, but also type systems and algebraic data types to problems in software and hardware specification and verification. Computer graphics is the study of digital visual contents and involves the synthesis and manipulation of image data. The study is connected to many other fields in computer science, including computer vision, image processing, and computational geometry, and is heavily applied in the fields of special effects and video games. Information can take the form of images, sound, video or other multimedia. Bits of information can be streamed via signals. Its processing is the central notion of informatics, the European view on computing, which studies information processing algorithms independently of the type of information carrier – whether it is electrical, mechanical or biological. This field plays important role in information theory, telecommunications, information engineering and has applications in medical image computing and speech synthesis, among others. What is the lower bound on the complexity of fast Fourier transform algorithms? is one of the unsolved problems in theoretical computer science. Scientific computing (or computational science) is the field of study concerned with constructing mathematical models and quantitative analysis techniques and using computers to analyze and solve scientific problems. A major usage of scientific computing is simulation of various processes, including computational fluid dynamics, physical, electrical, and electronic systems and circuits, societies and social situations (notably war games) along with their habitats, and interactions among biological cells. Modern computers enable optimization of such designs as complete aircraft. Notable in electrical and electronic circuit design are SPICE, as well as software for physical realization of new (or modified) designs. The latter includes essential design software for integrated circuits. Human–computer interaction (HCI) is the field of study and research concerned with the design and use of computer systems, mainly based on the analysis of the interaction between humans and computer interfaces. HCI has several subfields that focus on the relationship between emotions, social behavior and brain activity with computers. Software engineering is the study of designing, implementing, and modifying the software in order to ensure it is of high quality, affordable, maintainable, and fast to build. It is a systematic approach to software design, involving the application of engineering practices to software. Software engineering deals with the organizing and analyzing of software—it does not just deal with the creation or manufacture of new software, but its internal arrangement and maintenance. For example software testing, systems engineering, technical debt and software development processes. Artificial intelligence (AI) aims to or is required to synthesize goal-orientated processes such as problem-solving, decision-making, environmental adaptation, learning, and communication found in humans and animals. From its origins in cybernetics and in the Dartmouth Conference (1956), artificial intelligence research has been necessarily cross-disciplinary, drawing on areas of expertise such as applied mathematics, symbolic logic, semiotics, electrical engineering, philosophy of mind, neurophysiology, and social intelligence. AI is associated in the popular mind with robotic development, but the main field of practical application has been as an embedded component in areas of software development, which require computational understanding. The starting point in the late 1940s was Alan Turing's question "Can computers think?", and the question remains effectively unanswered, although the Turing test is still used to assess computer output on the scale of human intelligence. But the automation of evaluative and predictive tasks has been increasingly successful as a substitute for human monitoring and intervention in domains of computer application involving complex real-world data. Computer architecture, or digital computer organization, is the conceptual design and fundamental operational structure of a computer system. It focuses largely on the way by which the central processing unit performs internally and accesses addresses in memory. Computer engineers study computational logic and design of computer hardware, from individual processor components, microcontrollers, personal computers to supercomputers and embedded systems. The term "architecture" in computer literature can be traced to the work of Lyle R. Johnson and Frederick P. Brooks Jr., members of the Machine Organization department in IBM's main research center in 1959. Concurrency is a property of systems in which several computations are executing simultaneously, and potentially interacting with each other. A number of mathematical models have been developed for general concurrent computation including Petri nets, process calculi and the parallel random access machine model. When multiple computers are connected in a network while using concurrency, this is known as a distributed system. Computers within that distributed system have their own private memory, and information can be exchanged to achieve common goals. This branch of computer science aims studies the construction and behavior of computer networks. It addresses their performance, resilience, security, scalability, and cost-effectiveness, along with the variety of services they can provide. Computer security is a branch of computer technology with the objective of protecting information from unauthorized access, disruption, or modification while maintaining the accessibility and usability of the system for its intended users. Historical cryptography is the art of writing and deciphering secret messages. Modern cryptography is the scientific study of problems relating to distributed computations that can be attacked. Technologies studied in modern cryptography include symmetric and asymmetric encryption, digital signatures, cryptographic hash functions, key-agreement protocols, blockchain, zero-knowledge proofs, and garbled circuits. A database is intended to organize, store, and retrieve large amounts of data easily. Digital databases are managed using database management systems to store, create, maintain, and search data, through database models and query languages. Data mining is a process of discovering patterns in large data sets. Discoveries The philosopher of computing Bill Rapaport noted three Great Insights of Computer Science: Programming paradigms Programming languages can be used to accomplish different tasks in different ways. Common programming paradigms include: Many languages offer support for multiple paradigms, making the distinction more a matter of style than of technical capabilities. Research Conferences are important events for computer science research. During these conferences, researchers from the public and private sectors present their recent work and meet. Unlike in most other academic fields, in computer science, the prestige of conference papers is greater than that of journal publications. One proposed explanation for this is the quick development of this relatively new field requires rapid review and distribution of results, a task better handled by conferences than by journals. See also Notes References Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/Optical_depth] | [TOKENS: 1841] |
Contents Optical depth In physics, optical depth or optical thickness is the natural logarithm of the ratio of incident to transmitted radiant power through a material. Thus, the larger the optical depth, the smaller the amount of transmitted radiant power through the material. Spectral optical depth or spectral optical thickness is the natural logarithm of the ratio of incident to transmitted spectral radiant power through a material. Optical depth is dimensionless, and in particular is not a length, though it is a monotonically increasing function of optical path length, and approaches zero as the path length approaches zero. The use of the term "optical density" for optical depth is discouraged. In chemistry, a closely related quantity called "absorbance" or "decadic absorbance" is used instead of optical depth: the common logarithm of the ratio of incident to transmitted radiant power through a material. It is the optical depth divided by loge(10), because of the different logarithm bases used. Mathematical definitions The optical depth of a material, denoted τ {\textstyle \tau } , is given by: τ = ln ( Φ e i Φ e t ) = − ln T {\displaystyle \tau =\ln \!\left({\frac {\Phi _{\mathrm {e} }^{\mathrm {i} }}{\Phi _{\mathrm {e} }^{\mathrm {t} }}}\right)=-\ln T} where The absorbance A {\textstyle A} is related to optical depth by: τ = A ln 10 {\displaystyle \tau =A\ln {10}} The spectral optical depth in frequency (denoted τ ν {\displaystyle \tau _{\nu }} ) or in wavelength ( τ λ {\displaystyle \tau _{\lambda }} ) of a material is given by: τ ν = ln ( Φ e , ν i Φ e , ν t ) = − ln T ν {\displaystyle \tau _{\nu }=\ln \!\left({\frac {\Phi _{\mathrm {e} ,\nu }^{\mathrm {i} }}{\Phi _{\mathrm {e} ,\nu }^{\mathrm {t} }}}\right)=-\ln T_{\nu }} τ λ = ln ( Φ e , λ i Φ e , λ t ) = − ln T λ , {\displaystyle \tau _{\lambda }=\ln \!\left({\frac {\Phi _{\mathrm {e} ,\lambda }^{\mathrm {i} }}{\Phi _{\mathrm {e} ,\lambda }^{\mathrm {t} }}}\right)=-\ln T_{\lambda },} where Spectral absorbance is related to spectral optical depth by: τ ν = A ν ln 10 , {\displaystyle \tau _{\nu }=A_{\nu }\ln 10,} τ λ = A λ ln 10 , {\displaystyle \tau _{\lambda }=A_{\lambda }\ln 10,} where Relationship with attenuation Optical depth measures the attenuation of the transmitted radiant power in a material. Attenuation can be caused by absorption, but also reflection, scattering, and other physical processes. Optical depth of a material is approximately equal to its attenuation when both the absorbance is much less than 1 and the emittance of that material (not to be confused with radiant exitance or emissivity) is much less than the optical depth: Φ e t + Φ e a t t = Φ e i + Φ e e , {\displaystyle \Phi _{\mathrm {e} }^{\mathrm {t} }+\Phi _{\mathrm {e} }^{\mathrm {att} }=\Phi _{\mathrm {e} }^{\mathrm {i} }+\Phi _{\mathrm {e} }^{\mathrm {e} },} T + A T T = 1 + E , {\displaystyle T+ATT=1+E,} where and according to the Beer–Lambert law, T = e − τ , {\displaystyle T=e^{-\tau },} so: A T T = 1 − e − τ + E ≈ τ + E ≈ τ , if τ ≪ 1 and E ≪ τ . {\displaystyle ATT=1-e^{-\tau }+E\approx \tau +E\approx \tau ,\quad {\text{if}}\ \tau \ll 1\ {\text{and}}\ E\ll \tau .} Optical depth of a material is also related to its attenuation coefficient by: τ = ∫ 0 l α ( z ) d z , {\displaystyle \tau =\int _{0}^{l}\alpha (z)\,\mathrm {d} z,} where and if α(z) is uniform along the path, the attenuation is said to be a linear attenuation and the relation becomes: τ = α l {\displaystyle \tau =\alpha l} Sometimes the relation is given using the attenuation cross section of the material, that is its attenuation coefficient divided by its number density: τ = ∫ 0 l σ n ( z ) d z , {\displaystyle \tau =\int _{0}^{l}\sigma n(z)\,\mathrm {d} z,} where and if n {\displaystyle n} is uniform along the path, i.e., n ( z ) ≡ N {\displaystyle n(z)\equiv N} , the relation becomes: τ = σ N l {\displaystyle \tau =\sigma Nl} Applications In atomic physics, the spectral optical depth of a cloud of atoms can be calculated from the quantum-mechanical properties of the atoms. It is given by τ ν = d 2 n ν 2 c ℏ ε 0 σ γ {\displaystyle \tau _{\nu }={\frac {d^{2}n\nu }{2\mathrm {c} \hbar \varepsilon _{0}\sigma \gamma }}} where In atmospheric sciences, one often refers to the optical depth of the atmosphere as corresponding to the vertical path from Earth's surface to outer space; at other times the optical path is from the observer's altitude to outer space. The optical depth for a slant path is τ = mτ′, where τ′ refers to a vertical path, m is called the relative airmass, and for a plane-parallel atmosphere it is determined as m = sec θ where θ is the zenith angle corresponding to the given path. Therefore, T = e − τ = e − m τ ′ {\displaystyle T=e^{-\tau }=e^{-m\tau '}} The optical depth of the atmosphere can be divided into several components, ascribed to Rayleigh scattering, aerosols, and gaseous absorption. The optical depth of the atmosphere can be measured with a Sun photometer. The optical depth with respect to the height within the atmosphere is given by τ ( z ) = k a w 1 ρ 0 H e − z / H {\displaystyle \tau (z)=k_{\text{a}}w_{1}\rho _{0}He^{-z/H}} and it follows that the total atmospheric optical depth is given by τ ( 0 ) = k a w 1 ρ 0 H {\displaystyle \tau (0)=k_{\text{a}}w_{1}\rho _{0}H} In both equations: The optical depth of a plane parallel cloud layer is given by τ = Q e [ 9 π L 2 H N 16 ρ l 2 ] 1 / 3 {\displaystyle \tau =Q_{\text{e}}\left[{\frac {9\pi L^{2}HN}{16\rho _{l}^{2}}}\right]^{1/3}} where: So, with a fixed depth and total liquid water path, τ ∝ N 1 / 3 {\textstyle \tau \propto N^{1/3}} . In astronomy, the photosphere of a star is defined as the surface where its optical depth is 2/3. This means that each photon emitted at the photosphere suffers an average of less than one scattering before it reaches the observer. At the temperature at optical depth 2/3, the energy emitted by the star (the original derivation is for the Sun) matches the observed total energy emitted.[citation needed][clarification needed] Note that the optical depth of a given medium will be different for different colors (wavelengths) of light. For planetary rings, the optical depth is the (negative logarithm of the) proportion of light blocked by the ring when it lies between the source and the observer. This is usually obtained by observation of stellar occultations. See also References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Choanoflagellate] | [TOKENS: 3525] |
Contents Choanoflagellate Choanoflagellates are a group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of animals. The name refers to the characteristic funnel-shaped "collar" of interconnected microvilli and the presence of a flagellum. Choanoflagellates are found globally in aquatic environments, and they are of particular interest to evolutionary biologists studying the origins of multicellularity in animals. The flagellum of choanoflagellates is surrounded by microvilli at its base. Movement of the flagellum creates water currents that can propel free-swimming choanoflagellates through the water column and trap bacteria and detritus against the microvilli, where these foodstuffs are engulfed. This feeding plays an ecological role in the carbon cycle by linking different trophic levels. Choanoflagellates bear morphological similarities to the choanocyte, a type of cell in sponges. As the proposed sister group to Animalia, choanoflagellates serve as a useful model for reconstructions of the last unicellular ancestor of animals. According to a 2021 study, crown group craspedids (and perhaps crown group choanoflagellates if Acanthoecida arose within Craspedida) appeared 422.78 million years ago, although a previous study from 2017 recovered the divergence of the crown group choanoflagellates (craspedids) at 786.62 million years. Etymology Choanoflagellate is a hybrid word from Greek χοάνη khoánē meaning "funnel" (due to the shape of the collar) and the Latin word flagellum (whence English flagellum). Appearance Each choanoflagellate has a single flagellum, surrounded by a ring of actin-filled protrusions called microvilli, forming a cylindrical or conical "collar" (choanos in Greek). Movement of the flagellum draws water through the collar, and bacteria and detritus are captured by the microvilli and ingested. Water currents generated by the flagellum also push free-swimming cells along, as in animal sperm. In contrast, most other flagellates are pulled by their flagella. In addition to the single apical flagellum surrounded by actin-filled microvilli that characterizes choanoflagellates, the internal organization of organelles in the cytoplasm is constant. A flagellar basal body sits at the base of the apical flagellum, and a second, non-flagellar basal body rests at a right angle to the flagellar base. The nucleus occupies an apical-to-central position in the cell, and food vacuoles are positioned in the basal region of the cytoplasm. Additionally, the cell body of many choanoflagellates is surrounded by a distinguishing extracellular matrix or periplast. These cell coverings vary greatly in structure and composition and are used by taxonomists for classification purposes. Many choanoflagellates build complex basket-shaped "houses", called lorica, from several silica strips cemented together. The functional significance of the periplast is unknown, but in sessile organisms, it is thought to aid attachment to the substrate. In planktonic organisms, there is speculation that the periplast increases drag, thereby counteracting the force generated by the flagellum and increasing feeding efficiency. Choanoflagellates are either free-swimming in the water column or sessile, adhering to the substrate directly or through either the periplast or a thin pedicel. Although choanoflagellates are thought to be strictly free-living and heterotrophic, several choanoflagellate relatives, such as members of Ichthyosporea or Mesomycetozoa, follow a parasitic or pathogenic lifestyle. The life histories of choanoflagellates are poorly understood. Many species are thought to be solitary; however, coloniality seems to have arisen independently several times within the group, and colonial species still retain a solitary stage. Ecology Over 125 extant species of choanoflagellates are known, distributed globally in marine, brackish and freshwater environments from the Arctic to the tropics, occupying both pelagic and benthic zones. Although most sampling of choanoflagellates has occurred between 0 and 25 m (0 and 82 ft), they have been recovered from as deep as 300 m (980 ft) in open water and 100 m (330 ft) under Antarctic ice sheets. Many species are hypothesized to be cosmopolitan on a global scale [e.g., Diaphanoeca grandis has been reported from North America, Europe and Australia (OBIS)], while other species are reported to have restricted regional distributions. Co-distributed choanoflagellate species can occupy quite different microenvironments, but in general, the factors that influence the distribution and dispersion of choanoflagellates remain to be elucidated. A number of species, such as those in the genus Proterospongia, form simple colonies, planktonic clumps that resemble a miniature cluster of grapes in which each cell in the colony is flagellated or clusters of cells on a single stalk. A colonial species from Mono Lake, Barroeca monosierra, forms spheres filled with a branched network of an extracellular matrix where a microbiome of different species of symbiotic bacteria live. In October 2019, scientists found a new band behaviour of choanoflagellates: they apparently can coordinate to respond to light. The choanoflagellates feed on bacteria and link otherwise inaccessible forms of carbon to organisms higher in the trophic chain. Even today, they are important in the carbon cycle and microbial food web. There is some evidence that choanoflagellates feast on viruses as well. Life cycle Choanoflagellates grow vegetatively, with multiple species undergoing longitudinal fission; however, the reproductive life cycle of choanoflagellates remains to be elucidated. A paper released in August 2017 showed that environmental changes, including the presence of certain bacteria, trigger the swarming and subsequent sexual reproduction of choanoflagellates. The ploidy level is unknown; however, the discovery of both retrotransposons and key genes involved in meiosis previously suggested that they used sexual reproduction as part of their life cycle. Some choanoflagellates can undergo encystment, which involves the retraction of the flagellum and collar and encasement in an electron dense fibrillar wall. On transfer to fresh media, excystment occurs; though it remains to be directly observed. Evidence for sexual reproduction has been reported in the choanoflagellate species Salpingoeca rosetta. Evidence has also been reported for the presence of conserved meiotic genes in the choanoflagellates Monosiga brevicollis and Monosiga ovata. Silicon biomineralization The Acanthoecid choanoflagellates produce an extracellular basket structure known as a lorica. The lorica is composed of individual costal strips, made of a silica-protein biocomposite. Each costal strip is formed within the choanoflagellate cell and is then secreted to the cell surface. In nudiform choanoflagellates, lorica assembly takes place using a number of tentacles once sufficient costal strips have been produced to comprise a full lorica. In tectiform choanoflagellates, costal strips are accumulated in a set arrangement below the collar. During cell division, the new cell takes these costal strips as part of cytokinesis and assembles its own lorica using only these previously produced strips. Choanoflagellate biosilicification requires the concentration of silicic acid within the cell. This is carried out by silicon transporter (SiT) proteins. Analysis of choanoflagellate SiTs shows that they are similar to the SiT-type silicon transporters of diatoms and other silica-forming stramenopiles. The SiT gene family shows little or no homology to any other genes, even to genes in non-siliceous choanoflagellates or stramenopiles. This suggests that the SiT gene family evolved via a lateral gene transfer event between Acanthoecids and Stramenopiles. This is a remarkable case of horizontal gene transfer between two distantly related eukaryotic groups, and has provided clues to the biochemistry and silicon-protein interactions of the unique SiT gene family. Classification Félix Dujardin, a French biologist interested in protozoan evolution, recorded the morphological similarities of choanoflagellates and sponge choanocytes and proposed the possibility of a close relationship as early as 1841. Over the past decade, this hypothesized relationship between choanoflagellates and animals has been upheld by independent analyses of multiple unlinked genetic sequences: 18S rDNA, nuclear protein-coding genes, and mitochondrial genomes (Steenkamp, et al., 2006; Burger, et al., 2003; Wainright, et al., 1993). Importantly, comparisons of mitochondrial genome sequences from a choanoflagellate and three sponges confirm the placement of choanoflagellates as an outgroup to Metazoa (animals, also known as Animalia) and negate the possibility that choanoflagellates evolved from metazoans (Lavrov, et al., 2005). Finally, a 2001 study of genes expressed in choanoflagellates has revealed that choanoflagellates synthesize homologues of metazoan cell signaling and adhesion genes. Genome sequencing shows that, among living organisms, the choanoflagellates are most closely related to animals. Because choanoflagellates and metazoans are closely related, comparisons between the two groups promise to provide insights into the biology of their last common ancestor and the earliest events in metazoan evolution. The choanocytes (also known as "collared cells") of sponges (considered among the most basal metazoa) have the same basic structure as choanoflagellates. Collared cells are found in other animal groups, such as ribbon worms, suggesting this was the morphology of their last common ancestor. The last common ancestor of animals and choanoflagellates was unicellular, perhaps forming simple colonies; in contrast, the last common ancestor of all eumetazoan animals was a multicellular organism, with differentiated tissues, a definite "body plan", and embryonic development (including gastrulation). The timing of the splitting of these lineages is difficult to constrain, but was probably in the late Precambrian, >600 million years ago. External relationships of Choanoflagellatea. Cristidiscoidea Fungi Ichthyosporea Corallochytrea Filasterea Animalia (Metazoa) Choanoflagellatea The choanoflagellates were included in Chrysophyceae until Hibberd, 1975. Recent molecular phylogenetic reconstruction of the internal relationships of choanoflagellates allows the polarization of character evolution within the clade. Large fragments of the nuclear SSU and LSU ribosomal RNA, alpha tubulin, and heat-shock protein 90 coding genes were used to resolve the internal relationships and character polarity within choanoflagellates. Each of the four genes showed similar results independently and analysis of the combined data set (concatenated) along with sequences from other closely related species (animals and fungi) demonstrate that choanoflagellates are strongly supported as monophyletic and confirm their position as the closest known unicellular living relative of animals. Previously, Choanoflagellida was divided into these three families based on the composition and structure of their periplast: Codonosigidae, Salpingoecidae and Acanthoecidae. Members of the family Codonosigidae appear to lack a periplast when examined by light microscopy, but may have a fine outer coat visible only by electron microscopy. The family Salpingoecidae consists of species whose cells are encased in a firm theca that is visible by both light and electron microscopy. The theca is a secreted covering predominately composed of cellulose or other polysaccharides. These divisions are now known to be paraphyletic, with convergent evolution of these forms widespread. The third family of choanoflagellates, the Acanthoecidae, has been supported as a monophyletic group. This clade possess a synapomorphy of the cells being found within a basket-like lorica, providing the alternative name of "Loricate Choanoflagellates". The Acanthoecid lorica is composed of a series of siliceous costal strips arranged into a species-specific lorica pattern." The choanoflagellate tree based on molecular phylogenetics divides into three well supported clades. Clade 1 and Clade 2 each consist of a combination of species traditionally attributed to the Codonosigidae and Salpingoecidae, while Clade 3 comprises species from the group taxonomically classified as Acanthoecidae. The mapping of character traits on to this phylogeny indicates that the last common ancestor of choanoflagellates was a marine organism with a differentiated life cycle with sedentary and motile stages. Choanoflagellates; Genomes and transcriptomes The genome of Monosiga brevicollis, with 41.6 million base pairs, is similar in size to filamentous fungi and other free-living unicellular eukaryotes, but far smaller than that of typical animals. In 2010, a phylogenomic study revealed that several algal genes are present in the genome of Monosiga brevicollis. This could be due to the fact that, in early evolutionary history, choanoflagellates consumed algae as food through phagocytosis. Carr et al. (2010) screened the M. brevicollis genome for known eukaryotic meiosis genes. Of 19 known eukaryotic meiotic genes tested (including 8 that function in no other process than meiosis), 18 were identified in M. brevicollis. The presence of meiotic genes, including meiosis specific genes, indicates that meiosis, and by implication, sex is present within the choanoflagellates. The genome of Salpingoeca rosetta is 55 megabases in size. Homologs of cell adhesion, neuropeptide and glycosphingolipid metabolism genes are present in the genome. S. rosetta has a sexual life cycle and transitions between haploid and diploid stages. In response to nutrient limitation, haploid cultures of S. rosetta become diploid. This ploidy shift coincides with mating during which small, flagellated cells fuse with larger flagellated cells. There is also evidence of historical mating and recombination in S. rosetta. S. rosetta is induced to undergo sexual reproduction by the marine bacterium Vibrio fischeri. A single V. fischeri protein, EroS fully recapitulates the aphrodisiac-like activity of live V. fisheri. The single-cell amplified genomes of four uncultured marine choanoflagellates, tentatively called UC1–UC4, were sequenced in 2019. The genomes of UC1 and UC4 are relatively complete. An EST dataset from Monosiga ovata was published in 2006. The major finding of this transcriptome was the choanoflagellate Hoglet domain and shed light on the role of domain shuffling in the evolution of the Hedgehog signaling pathway. M. ovata has at least four eukaryotic meiotic genes. The transcriptome of Stephanoeca diplocostata was published in 2013. This first transcriptome of a loricate choanoflagellate led to the discovery of choanoflagellate silicon transporters. Subsequently, similar genes were identified in a second loricate species, Diaphanoeca grandis. Analysis of these genes found that the choanoflagellate silicon transporters show homology to the SIT-type silicon transporters of diatoms and have evolved through horizontal gene transfer. An additional 19 transcriptomes were published in 2018. A large number of gene families previously thought to be animal-only were found. References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Full_motion_video] | [TOKENS: 3396] |
Contents Full-motion video Full-motion video (FMV) is a video game narration technique that relies upon pre-recorded video files (rather than sprites, vectors, or 3D models) to display action in the game. While many games feature FMVs as a way to present information during cutscenes, games that are primarily presented through FMVs are referred to as full-motion video games or interactive movies. Recent full motion video games often combine the use of CGI/green screens and in-game graphics for immersion. The early 1980s saw almost exclusive use of the LaserDisc for FMV games. Many arcade games used the technology but it was ultimately considered to be a fad and fell out of use. In the early 1990s FMV games had a resurgence of interest, the proliferation of optical discs gave rise to a slew of original FMV-based computer games such as Night Trap (1992), The 7th Guest (1993), Voyeur (1993), Phantasmagoria (1995), and Daryl F. Gates' Police Quest: SWAT (1995). The introduction of CD-based consoles like 3DO, CD-i, and Sega CD brought the concept of interactive FMV gameplay. Companies such as Digital Pictures and American Laser Games were formed to produce full-motion video games. As the video game industry was emerging from its niche status into the mainstream—by 1994 it was two-and-a-half times larger than Hollywood by revenue[citation needed]—Hollywood began to make inroads into the growing market. In 1994, Sony's Johnny Mnemonic became the first video game title produced by a film studio. Soon thereafter, video game heavyweight Electronic Arts featured well-known Hollywood talent such as Mark Hamill, Tom Wilson and John Spencer in their critically acclaimed titles Wing Commander III and IV, setting the stage for a more expansive tie-up between the movie and video game industries. With the continual improvement of in-game CGI, FMV as a major gameplay component had eventually disappeared because of the limited gameplay options it allowed. Arcades The first wave of FMV games originated in arcades in 1983 with laserdisc video games, notably Astron Belt from Sega and Dragon's Lair from Cinematronics. They used Laserdiscs to store the video used in the game, which allowed for very high quality visuals compared to contemporary arcade games of the era. A number of arcade games using FMV with Laserdiscs were released over the next three years and the technology was touted as the future of video games. Some games released in this era reused video footage from other sources while others had it purpose made. Bega's Battle, Cliff Hanger and Firefox reused footage, while titles like Space Ace, Time Gal, Thayer's Quest, Super Don Quix-ote and Cobra Command were entirely original. The use of pre-rendered 3D computer graphics for video sequences also date back to two arcade laserdisc games introduced in 1983: Interstellar, introduced by Funai at the AM Show in September, and Star Rider, introduced by Williams Electronics at the AMOA show in October. The limited nature of FMV, high price to play (50 cents in an era where 25 cents was standard), high cost of the hardware and problems with reliability quickly took its toll on the buzz surrounding these games and their popularity diminished. By 1985, the allure of FMV and the Laserdisc had worn off, and the technology had disappeared from arcades by the end of 1987. RDI Video Systems (Thayer's Quest) had branched out into making a home console called the Halcyon, but it failed and they went bankrupt. Cinematronics's fortunes fared little better and they were bought out by Tradewest in 1987. Companies such as Atari canceled more prototype Laserdisc games than they released. Others, like Universal, stopped development on games after only one release despite announcing several titles. After only a few years, the technology had improved and Laserdisc players were more reliable. In addition, costs had come down and the average price to play a game had gone up. These factors caused a resurgence of the popularity of Laserdiscs games in the arcade. American Laser Games released a light gun shooting game called Mad Dog McCree in 1990, which was an instant hit. Then, in 1991 with Who Shot Johnny Rock?, American Laser alone would go on to lease almost a dozen Laserdisc games over the next few years and many other companies again rushed to release titles using the technology. Dragon's Lair II, a title which had been shelved years earlier, was released by Leland to strong sales. Time Traveler further pushed the technology by using special projection technology to give the appearance of 3D visuals. Again, the fad passed quickly. The limited nature of the Laserdisc hampered interactivity and limited replayability, a key weakness in arcade games. American Laser, the chief producer of Laserdisc games during this era, had stopped making arcade games in 1994 and most other companies switched over to newer technologies around the same time. With the rise of 3D graphics and the introduction of hard drives and CD-ROMs to arcades, the large, expensive and small-capacity Laserdisc could not compete and disappeared. While CDs would see some use in the mid and late 1990s, it was hard drives, GD-ROMs and DVD-ROMs that caused the largest jump in FMV use in the arcade. Their very large capacities and mature, reliable technology allowed for much cheaper hardware than traditional hardware systems, and FMV cut-scenes became commonplace. FMV as a major gameplay component had disappeared by this time because of the limited gameplay options it allowed. Home systems In 1984, a home console system called the Halcyon was released by RDI Video Systems that used Laserdiscs for its games and was to feature ports of several popular Laserdisc arcade games of the day. It used FMV exclusively, but the company folded after releasing only two titles for the system. The LaserActive from Pioneer would try the technology again in 1994, but it too failed. By the early 1990s when PCs and consoles moved to creating games on a CD, they became technically capable of utilizing more than a few minutes' worth of movies in a game. This gave rise to a slew of original FMV-based computer games such as Night Trap (1992), The 7th Guest (1993), Voyeur (1993), Phantasmagoria (1995), and Daryl F. Gates' Police Quest: SWAT (1995). Other titles were simply scaled down ports of Laserdisc arcade games, some of them a decade old by this time. Regardless of their sources, these FMV games frequently used B-movie and TV actors and promised to create the experience of playing an interactive movie or animation. However, production values were quite low with amateurish sets, lighting, costumes, and special effects. Animated titles either cobbled together footage from old anime or used cheaper overseas animation producers to create their footage. In addition, the video quality in these early games was low, and the gameplay frequently did not live up to the hype becoming well-known failures in video gaming. At this time, consoles like 3DO, CD-i, and Sega CD borrowed this concept for several low-quality interactive games. Companies such as Digital Pictures and American Laser Games were formed to produce full-motion video games. Also, the "multimedia" phenomenon that was exploding in popularity at the time increased the popularity of FMV because consumers were excited by this new emerging interactive technology. The personal computer was rapidly evolving during the early-to-mid 1990s from a simple text-based productivity device into a home entertainment machine. Gaming itself was also emerging from its niche market into the mainstream with the release of easier-to-use and more powerful operating systems, such as Microsoft's Windows 95, that leveraged continually evolving processing capabilities. Some games like the Tex Murphy series combined FMV cutscenes with a virtual world to explore. Video game consoles too saw incredible gains in presentation quality and contributed to the mass market's growth in awareness of gaming. It was during the 1990s that the video/computer game industry first beat Hollywood in earnings. Sony made its debut in the console market with the release of the 32-bit PlayStation. The PlayStation was probably the first console to popularize FMVs (as opposed to earlier usage of FMV which was seen as a passing fad). A part of the machine's hardware was a dedicated M-JPEG processing unit which enabled far superior quality relative to other platforms of the time. The FMVs in Final Fantasy VIII, for example, were marketed as movie-quality at the time. FMVs in games today typically consist of high-quality pre-rendered video sequences (CGI). These sequences are created in similar ways as computer generated effects in movies. Use of FMV as a selling point or focus has diminished in modern times. This is primarily due to graphical advancements in modern video game systems making it possible for in-game cinematics to have just as impressive visual quality. Digitized video footage of real actors in games generally ended for mainstream games in the early 2000s with a few exceptions such as Ace Combat Zero: The Belkan War released in 2006, Command & Conquer 3: Tiberium Wars released in 2007, Tesla Effect: A Tex Murphy Adventure released in 2014, Her Story and Guitar Hero Live released in 2015, the 2015 reboot of Need for Speed, and Obduction released in 2016. Formats The early 1980s saw the almost exclusive use of the Laserdisc for FMV games. Many arcade games used the technology but it was ultimately considered a fad and fell out of use. At least one arcade game, NFL Football from Bally/Midway, used CEDs to play its video. Some 1970s era Nintendo games used film and projectors. formats had the advantage of offering full frame video and sound without the quality problems of compressed video that would plague later formats like CDs. With the re-popularization of FMV games in the early 1990s following the advent of CD-ROM, higher-end developers usually created their own custom FMV formats to suit their needs. Early FMV titles used game-specific proprietary video renderers optimized for the content of the video (e.g., live-action vs. animated), because CPUs of the day were incapable of playing back real-time MPEG-1 until the fastest 486 and Pentium CPUs arrived. Consoles, on the other hand, either used a third-party codec (e.g., Cinepak for Sega CD games) or used their own proprietary format (e.g. the Philips CD-i). Video quality steadily increased as CPUs became more powerful to support higher quality video compression and decompression. The 7th Guest, one of the first megahit multiple-CD-ROM games, was one of the first games to feature transparent quality 640x320 FMV at 15 frames per second in a custom format designed by programmer Graeme Devine. Other examples of this would be Sierra's VMD (Video and Music Data) format, used in games like Gabriel Knight 2 and Phantasmagoria, or Westwood Studios' VQA format, used in most Westwood games made from the mid-1990s up until 2000s Command & Conquer: Tiberian Sun Firestorm. These video formats initially offered very limited video quality, due to the limitations of the machines the games needed to run on. Ghosting and distortion of high-motion scenes, heavy pixelization, and limited color palettes were prominent visual problems. However, each game pushed the technological envelope and was typically seen as impressive even with quality issues. Johnny Mnemonic: The Interactive Action Movie, was the first FMV title made by a Hollywood studio. Sony Imagesoft spent over $3 million on the title. Instead of piecing together the title with filmed assets from their movie (directed by Robert Longo) of the same name, Sony hired Propaganda Code director Douglas Gayeton to write and film an entirely new storyline for the property. The CD-ROM's interactivity was made possible with the Cine-Active engine, based on the QuickTime 2.0 codec. Wing Commander III: Heart of the Tiger was one of the most significant FMV titles made in 1994, featuring big-name Hollywood actors. The video quality in the game suffered significantly from the aforementioned problems and was almost visually indecipherable in parts; however, this did not stop the title from earning significant praise for its innovative gameplay/FMV combination. Its sequel, Wing Commander IV: The Price of Freedom, used a similar custom movie codec in its CD-ROM release, but a later limited-volume DVD-ROM release saw MPEG-2 DVD-quality movies that far exceeded the original CD release in quality. A hardware decoder card was required at the time to play back the DVD-quality video on a PC. Wing Commander IV was also the first game to have used actual film (rather than video tape) to record the FMV scenes which attributed to the ability to create a DVD-quality transfer. An exception to the rule was The 11th Hour, the sequel to The 7th Guest. 11th Hour featured 640×480 FMV at 30 frames-per-second on 4 CDs. The development team had worked for three years on developing a format that could handle the video, as the director of the live-action sequences had not shot the FMV sequences in a way that could be easily compressed. However, this proved to be the game's downfall, as most computers of the day could not play the full-resolution video. Users were usually forced to select an option which played the videos at a quarter-size resolution in black-and-white. As FMV established itself in the market as a growing game technology, a small company called RAD Game Tools appeared on the market with their 256-color FMV format Smacker. Developers took to the format, and the format ended up being used in over 3,000, largely PC-based games. With the launch of consoles with built-in optical storage (the Sega Saturn and Sony's PlayStation) console manufacturers began more actively taking it upon themselves to provide higher quality FMV capabilities to developers. Sony included optimizations in their hardware for their MDEC (motion decompression) technology, and Sega chose the software route. Sega worked both internally on optimizing technology such as Cinepak, and externally by licensing video decompression technology from the New York-based Duck Corporation. While Duck's offering won praise for its quality (showcased in games like Enemy Zero, major Launch titles in the US and the Saturn adaptations of console hits from the Sega AM2 arcade group) the opaque licensing and royalty structure impeded widespread adoption outside of Japanese and larger US developers. Duck's TrueMotion technology was extended to the PC and Macintosh as well, showcased in the high-profile Star Trek: Borg and Star Trek: Klingon, The X-Files Game, Final Fantasy VII, and the highly anticipated sequel to Phantasmagoria, Phantasmagoria: A Puzzle of Flesh and other titles. It was reported that versions for PlayStation and GameCube were developed, but the last console version released was for Sega's short-lived Dreamcast. As the popularity of games loaded with live-action and FMV faded out in the late 1990s, and with Smacker becoming outdated in the world of 16-bit color games, RAD introduced a new true-color format, Bink video. Developers quickly took to the format because of its high compression ratios and videogame-tailored features. The format is still one of the most popular FMV formats used in games today. 4,000 games have used Bink, and the number is still growing. In the late '90s, Duck largely shelved its support for the console market (likely fueled by the direct support for DVD support in newer generation consoles) and focused its formats instead on internet delivered video. Duck went public as On2 Technologies and later generations of its technology was licensed by Adobe, Skype and was eventually bought (along with the company) by Google as the foundation for WebM. An early open source version of that work also appears as the renamed Theora codec of the Xiph Project. Windows Media Video, DivX, Flash Video, Theora and WebM are also now major players in the market. DivX is used in several GameCube games, including Star Wars Rogue Squadron III: Rebel Strike. See also References External links |
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[SOURCE: https://en.wikipedia.org/w/index.php?title=Special:CiteThisPage&page=Weak_artificial_intelligence&id=1339329794&wpFormIdentifier=titleform] | [TOKENS: 588] |
Contents Cite This Page IMPORTANT NOTE: Most educators and professionals do not consider it appropriate to use tertiary sources such as encyclopedias as a sole source for any information—citing an encyclopedia as an important reference in footnotes or bibliographies may result in censure or a failing grade. Wikipedia articles should be used for background information, as a reference for correct terminology and search terms, and as a starting point for further research. As with any community-built reference, there is a possibility for error in Wikipedia's content—please check your facts against multiple sources and read our disclaimers for more information. Bibliographic details for "Weak artificial intelligence" Please remember to check your manual of style, standards guide or instructor's guidelines for the exact syntax to suit your needs. For more detailed advice, see Citing Wikipedia. Citation styles for "Weak artificial intelligence" Wikipedia contributors. (2026, February 20). Weak artificial intelligence. In Wikipedia, The Free Encyclopedia. Retrieved 10:28, February 21, 2026, from https://en.wikipedia.org/w/index.php?title=Weak_artificial_intelligence&oldid=1339329794 Wikipedia contributors. "Weak artificial intelligence." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 20 Feb. 2026. Web. 21 Feb. 2026. Wikipedia contributors, 'Weak artificial intelligence', Wikipedia, The Free Encyclopedia, 20 February 2026, 00:31 UTC, <https://en.wikipedia.org/w/index.php?title=Weak_artificial_intelligence&oldid=1339329794> [accessed 21 February 2026] Wikipedia contributors, "Weak artificial intelligence," Wikipedia, The Free Encyclopedia, https://en.wikipedia.org/w/index.php?title=Weak_artificial_intelligence&oldid=1339329794 (accessed February 21, 2026). Wikipedia contributors. Weak artificial intelligence [Internet]. Wikipedia, The Free Encyclopedia; 2026 Feb 20, 00:31 UTC [cited 2026 Feb 21]. Available from: https://en.wikipedia.org/w/index.php?title=Weak_artificial_intelligence&oldid=1339329794. Weak artificial intelligence, https://en.wikipedia.org/w/index.php?title=Weak_artificial_intelligence&oldid=1339329794 (last visited Feb. 21, 2026). Wikipedia contributors. Weak artificial intelligence. Wikipedia, The Free Encyclopedia. February 20, 2026, 00:31 UTC. Available at: https://en.wikipedia.org/w/index.php?title=Weak_artificial_intelligence&oldid=1339329794. Accessed February 21, 2026. When using the LaTeX package url (\usepackage{url} somewhere in the preamble), which tends to give much more nicely formatted web addresses, the following may be preferred: |
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[SOURCE: https://en.wikipedia.org/wiki/Network_mapping#Large-scale_mapping_project] | [TOKENS: 1249] |
Contents Network mapping Network mapping is the study of the physical connectivity of networks e.g. the Internet. Network mapping discovers the devices on the network and their connectivity. It is not to be confused with network discovery or network enumeration which discovers devices on the network and their characteristics such as operating system, open ports, listening network services, etc. The field of automated network mapping has taken on greater importance as networks become more dynamic and complex in nature. Large-scale mapping project Images of some of the first attempts at a large scale map of the internet were produced by the Internet Mapping Project and appeared in Wired magazine. The maps produced by this project were based on the layer 3 or IP level connectivity of the Internet (see OSI model), but there are different aspects of internet structure that have also been mapped. More recent efforts to map the internet have been improved by more sophisticated methods, allowing them to make faster and more sensible maps. An example of such an effort is the OPTE project, which is attempting to develop a system capable of mapping the internet in a single day. The "Map of the Internet Project" maps over 4 billion internet locations as cubes in 3D cyberspace. Users can add URLs as cubes and re-arrange objects on the map. In early 2011 Canadian based Internet service provider (ISP) PEER 1 Hosting created their own Map of the Internet that depicts a graph of 19,869 autonomous system nodes connected by 44,344 connections. The sizing and layout of the autonomous systems was calculated based on their eigenvector centrality, which is a measure of how central to the network each autonomous system is. Graph theory can be used to better understand maps of the internet and to help choose between the many ways to visualize internet maps. Some projects have attempted to incorporate geographical data into their internet maps (for example, to draw locations of routers and nodes on a map of the world), but others are only concerned with representing the more abstract structures of the internet, such as the allocation, structure, and purpose of IP space. Enterprise network mapping Many organizations create network maps of their network system. These maps can be made manually using simple tools such as Microsoft Visio, or the mapping process can be simplified by using tools that integrate auto network discovery with Network mapping, one such example being the Fabric platform. Many of the vendors from the Notable network mappers list enable you to customize the maps and include your own labels, add un-discoverable items and background images. Sophisticated mapping is used to help visualize the network and understand relationships between end devices and the transport layers that provide service. Mostly, network scanners detect the network with all its components and deliver a list which is used for creating charts and maps using network mapping software. Items such as bottlenecks and root cause analysis can be easier to spot using these tools. There are three main techniques used for network mapping: SNMP based approaches, active probing and route analytics. The SNMP based approach retrieves data from Router and Switch MIBs in order to build the network map. The active probing approach relies on a series of traceroute-like probe packets in order to build the network map. The route analytics approach relies on information from the routing protocols to build the network map. Each of the three approaches have advantages and disadvantages in the methods that they use. Internet mapping techniques There are two prominent techniques used today to create Internet maps. The first works on the data plane of the Internet and is called active probing. It is used to infer Internet topology based on router adjacencies. The second works on the control plane and infers autonomous system connectivity based on BGP data. A BGP speaker sends 19-byte keep-alive messages every 60 seconds to maintain the connection. This technique relies on traceroute-like probing on the IP address space. These probes report back IP forwarding paths to the destination address. By combining these paths one can infer router level topology for a given POP. Active probing is advantageous in that the paths returned by probes constitute the actual forwarding path that data takes through networks. It is also more likely to find peering links between ISPs. However, active probing requires massive amounts of probes to map the entire Internet. It is more likely to infer false topologies due to load balancing routers and routers with multiple IP address aliases. Decreased global support for enhanced probing mechanisms such as source-route probing, ICMP Echo Broadcasting, and IP Address Resolution techniques leaves this type of probing in the realm of network diagnosis. This technique relies on various BGP collectors who collect routing updates and tables and provide this information publicly. Each BGP entry contains a Path Vector attribute called the AS Path. This path represents an autonomous system forwarding path from a given origin for a given set of prefixes. These paths can be used to infer AS-level connectivity and in turn be used to build AS topology graphs. However, these paths do not necessarily reflect how data is actually forwarded and adjacencies between AS nodes only represent a policy relationship between them. A single AS link can in reality be several router links. It is also much harder to infer peerings between two AS nodes as these peering relationships are only propagated to an ISP's customer networks. Nevertheless, support for this type of mapping is increasing as more and more ISP's offer to peer with public route collectors such as Route-Views and RIPE. New toolsets are emerging such as Cyclops and NetViews that take advantage of a new experimental BGP collector BGPMon. NetViews can not only build topology maps in seconds but visualize topology changes moments after occurring at the actual router. Hence, routing dynamics can be visualized in real time. In comparison to what the tools using BGPMon does there is another tool netTransformer able to discover and generate BGP peering maps either through SNMP polling or by converting MRT dumps to a graphml file format. netTransformer allows us also to perform network diffs between any two dumps and thus to reason how does the BGP peering has evolved through the years. WhatsUp Gold, an IT monitoring tool, tracks networks, servers, applications, storage devices, virtual devices and incorporates infrastructure management, application performance management. See also Notes External links |
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[SOURCE: https://en.wikipedia.org/wiki/Free_software_movement] | [TOKENS: 2800] |
Contents Free software movement The free software movement is a social movement with the goal of obtaining and guaranteeing certain freedoms for software users, namely the freedoms to run, study, modify, and share copies of software. Software which meets these requirements, The Four Essential Freedoms of Free Software, is termed free software. Although drawing on traditions and philosophies among members of the 1970s hacker culture and academia, Richard Stallman formally founded the movement in 1983 by launching the GNU Project. Stallman later established the Free Software Foundation in 1985 to support the movement. Philosophy The philosophy of the Free Software Movement is based on promoting collaboration between programmers and computer users. This process necessitates the rejection of proprietary software and the promotion of free software. Stallman notes that this action would not hinder the progression of technology, as he states, "Wasteful duplication of system programming effort will be avoided. This effort can go instead into advancing the state of the art." Members of the Free Software Movement believe that all software users should have the freedoms listed in The Free Software Definition. Members hold the belief that it is immoral to prohibit or prevent people from exercising these freedoms, and that they are required in creating a community where software users can help each other and have control over their technology. Regarding proprietary software, some believe that it is not strictly immoral, citing increased profitability in the business models available for proprietary software, along with technical features and convenience. The Free Software Foundation espouses the principle that all software needs free documentation, as programmers should have the ability to update manuals to reflect modifications made to the software. Within the movement, the FLOSS Manuals foundation specializes in providing such documentation. Actions The core work of the free software movement is focused on software development. The free software movement also rejects proprietary software, refusing to install software that does not give them the freedoms of free software. According to Stallman, "The only thing in the software field that is worse than an unauthorised copy of a proprietary program, is an authorised copy of the proprietary program because this does the same harm to its whole community of users, and in addition, usually the developer, the perpetrator of this evil, profits from it." Some supporters of the free software movement take up public speaking, or host a stall at software-related conferences to raise awareness of software freedom. This is seen as important since people who receive free software, but who are not aware that it is free software, will later accept a non-free replacement or will add software that is not free software. Free software movement The free software community is an informal term referring to users and developers of free software, as well as supporters of the free software movement. The movement sometimes refers to the open-source software community or a subset thereof. The Linux community is a subset of the free software community. The free software communities are characterized by the values, practices and principles that differ from other models of development and collaboration. Organisations Legislation and government A lot of lobbying work has been done against software patents and expansions of copyright law. Other lobbying focuses directly on the use of free software by government agencies and government-funded projects. In June 1997, the Society for Study, Application, and Development of Free Software was established under the China Software Industry Association in Beijing. Through this organization, the website freesoft.cei.gov.cn was developed, though the website is currently inaccessible on IP addresses located in the United States. The use of open-source software Linux in China has moved beyond government and educational institutions and has extended to other organizations such as financial institutions, telecommunications, and public security. Several Chinese researchers and scholars have claimed that the existence of FOSS in China has been important in challenging the presence of Microsoft, which Guangnan Ni, a member of the Chinese Academy of Engineering stated, "The monopoly of (Microsoft Windows) is even more powerful in China than other places in the world". Yi Zhou, a professor of mathematics at Fudan University, has also alleged that, "Government procurement of FLOSS for a number of years in China has compelled Microsoft to cut its prices of Office software substantially" Government of India had issued Policy on Adoption of Open Source Software for Government of India in 2015 to drive uptake within the government. With the vision to transform India as a Software Product Nation, National Policy on Software Products-2019 was approved by the Government. Free and Open Source Software (FOSS) is set up by[clarification needed] Union of Information Technology. For the case of Pakistan, Pakistan Software Export Board (PSEB) aids in the creation and advocate of FOSS usage in various government departments in addition to curbing illegality of copying that is software piracy. Promotion of adoption of FOSS is essential however it comes with problems of proprietary anti competition software practices including indulging in bribing and corruption by government departments. Pakistan works on the introduction of usage of open type basis of source Solutions in the curricula in schools and colleges. This is because of FOSS uniqueness in terms of political, democratic and social varieties of aspect regarding information communication and technology. In the United States, there have been efforts to pass legislation at the state level encouraging the use of free software by state government agencies. On January 11, 2022, two bills were shown on the New Hampshire legislating floor. The first bill called "HB 1273" was introduced by Democratic New Hampshire representative Eric Gallager, the bill prioritized "replacing proprietary software used by state agencies with free software." Gallager stated that to an extent, the proposed legislation will help distinguish "free software" and "open-source software", this will also put these two into state regulation. The second bill called "HB 1581" was proposed by Grafton Republican representative Lex Berezhny. The bill would've restored a requisite forcing "state agencies to use proprietary software" and as Lex put it, "when it is the most effective solution." He also said that requisite was happening between 2012 and 2018. According to the Concord Monitor, the state of New Hampshire had an already "thriving open source software community" with a view of "live free or die" but they had difficulty getting that notion with the state. Congressmen Edgar David Villanueva and Jacques Rodrich Ackerman have been instrumental in introducing free software in Peru, with bill 1609 on "Free Software in Public Administration". The incident invited the attention of Microsoft, Peru, whose general manager wrote a letter to Villanueva. His response received worldwide attention and is seen as a classic piece of argumentation favouring use of free software in governments. Uruguay has a sanctioned law requiring that the state give priority to free software. It also requires that information be exchanged in open formats. The Government of Venezuela implemented a free software law in January 2006. Decree No. 3,390 mandated all government agencies to migrate to free software over a two-year period. Publiccode.eu is a campaign launched demanding a legislation requiring that publicly financed software developed for the public sector be made publicly available under a Free and Open Source Software licence. If it is public money, it should be public code as well. The French Gendarmerie and the French National Assembly utilize the open source operating system Linux. Gov.uk keeps a list of "key components, tools and services that have gone into the construction of GOV.UK". Events Free Software events happening all around the world connects people to increase visibility for Free software projects and foster collaborations. Economics The free software movement has been extensively analyzed using economic methodologies, including perspectives from heterodox economics. Of particular interest to economists[who?] is the willingness of programmers in the free software movement to work, often producing higher-quality than proprietary programmers, without financial compensation. Studies comparing defect density in FLOSS projects and proprietary projects, shows that in all code size ranges open source code was of higher quality. In his 1998 article "The High-Tech Gift Economy", Richard Barbrook suggested that the then-nascent free software movement represented a return to the gift economy building on hobbyism and the absence of economic scarcity on the Internet. Gabriella Coleman has emphasized the importance of accreditation, respect, and honour within the free software community as a form of compensation for contributions to projects, over and against financial motivations. The Swedish Marxian economist Johan Söderberg has argued that the free software movement represents a complete alternative to capitalism that may be expanded to create a post-work society. He argues that the combination of a manipulation of intellectual property law and private property to make goods available to the public and a thorough blend between labor and fun make the free software movement a communist economy. Subgroups and schisms Since its inception, there is an ongoing contention between the many FLOSS organizations (FSF, OSI, Debian, Mozilla Foundation, Apache Foundation, etc.) within the free software movement, with the main conflicts centered around the organization's needs for compromise and pragmatism rather than adhering to founding values and philosophies. The Open Source Initiative (OSI) was founded in February 1998 by Eric Raymond and Bruce Perens to promote the term "open-source software" as an alternative term for free software. The OSI aimed to address the perceived shortcomings and ambiguity of the term "free software", as well as shifting the focus of free software from a social and ethical issue to instead emphasize open source as a superior model for software development. The latter became the view of Eric Raymond and Linus Torvalds, while Bruce Perens argued that open source was meant to popularize free software under a new brand and called for a return to basic ethical principles. Some free software advocates use the terms "Free and Open-Source Software" (FOSS) or "Free/Libre and Open-Source Software" (FLOSS) as a form of inclusive compromise, which brings free and open-source software advocates together to work on projects cohesively. Some users believe this is an ideal solution in order to promote both the user's freedom with the software and the pragmatic efficiency of an open-source development model. This view is reinforced by fact that majority of OSI-approved licenses and self-avowed open-source programs are also compatible with the free software formalisms and vice versa. While free and open source software are often linked together, they offer two separate ideas and values. Richard Stallman has referred to open source as "a non-movement", as it "does not campaign for anything". "Open source" addresses software being open as a practical question rather than an ethical dilemma – non-free software is not the best solution but nonetheless a solution. The free software movement views free software as a moral imperative: that proprietary software should be rejected, and that only free software should be developed and taught in order to make computing technology beneficial to the general public. Although the movements have differing values and goals, collaborations between the Free Software Movement and Open Source Initiative have taken place when it comes to practical projects. By 2005, Richard Glass considered the differences to be a "serious fracture" but "vitally important to those on both sides of the fracture" and "of little importance to anyone else studying the movement from a software engineering perspective" since they have had "little effect on the field". Criticism and controversy Eric Raymond criticises the speed at which the free software movement is progressing, suggesting that temporary compromises should be made for long-term gains. Raymond argues that this could raise awareness of the software and thus increase the free software movement's influence on relevant standards and legislation. Richard Stallman, on the other hand, sees the current level of compromise as a greater cause for worry. Stallman said that this is where people get the misconception of "free": there is no wrong in programmers' requesting payment for a proposed project, or charging for copies of free software. Restricting and controlling the user's decisions on use is the actual violation of freedom. Stallman defends that in some cases, monetary incentive is not necessary for motivation since the pleasure in expressing creativity is a reward in itself. Conversely, Stallman admits that it is not easy to raise money for free software projects. The free software movement champions copyleft licensing schema (often pejoratively called "viral licenses"). In its strongest form, copyleft mandates that any works derived from copyleft-licensed software must also carry a copyleft license, so the license spreads from work to work like a computer virus might spread from machine to machine. Stallman has previously stated his opposition to describing the GNU GPL as "viral". These licensing terms can only be enforced through asserting copyrights. Critics of copyleft licensing challenge the idea that restricting modifications is in line with the free software movement's emphasis on various "freedoms", especially when alternatives like MIT, BSD, and Apache licenses are more permissive. Proponents enjoy the assurance that copylefted work cannot usually be incorporated into non-free software projects. They emphasize that copyleft licenses may not attach for all uses and that in any case, developers can simply choose not to use copyleft-licensed software. FLOSS license proliferation is a serious concern in the FLOSS domain due to increased complexity of license compatibility considerations which limits and complicates source code reuse between FLOSS projects. The OSI and the FSF maintain their own lists of dozens of existing and acceptable FLOSS licenses. There is an agreement among most that the creation of new licenses should be minimized and those created should be made compatible with the major existing FLOSS licenses. Therefore, there was a strong controversy around the update of the GNU GPLv2 to the GNU GPLv3 in 2007, as the updated license is not compatible with the previous version. Several projects (mostly of the open source faction like the Linux kernel) decided to not adopt the GPLv3 while almost all of the GNU project's packages adopted it. See also References Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/Judeo-Malayalam] | [TOKENS: 900] |
Contents Judeo-Malayalam Judeo-Malayalam (Malayalam: യെഹൂദ്യമലയാളം, yehūdyamalayāḷaṃ; Hebrew: מלאיאלאם יהודית, malayalam yəhūḏīṯ) is the traditional language of the Cochin Jews (also called Malabar Jews), from Kerala, in southern India, spoken today by a few dozen people in Israel and by fewer than 25 people in India. Judeo-Malayalam is the only known Dravidian Jewish language. (There is another Dravidian language spoken regularly by a Jewish community, Telugu. Spoken by the small and only very newly observant Jewish community of east-central Andhra Pradesh, because of the long period in which the people were not practicing Judaism, they did not develop any distinctly identifiable Judeo-Telugu language or the dialect. See main article: Telugu Jews.) Since it does not differ substantially in grammar or syntax from other colloquial Malayalam dialects, it is not considered by many linguists to be a language in its own right, but rather a dialect, or simply a language variation. Judeo-Malayalam shares common features with other Jewish languages like Ladino, Judeo-Arabic and Yiddish. For example, verbatim translations from Hebrew to Malayalam, archaic features of Old Malayalam, Hebrew components agglutinated to Dravidian verb and noun formations and special idiomatic usages based on its Hebrew loanwords. Due to the lack of long-term scholarship on this language variation, there is no separate designation for the language (if it can be so considered), for it to have its own language code (see also SIL and ISO 639). Unlike many Jewish languages, Judeo-Malayalam is not written using the Hebrew alphabet. It does, however, like most Jewish languages, contain many Hebrew loanwords, which are regularly transliterated, as much as possible, using the Malayalam script. Like many other Jewish languages, Judeo-Malayalam also contains a number of lexical, phonological and syntactic archaisms, in this case, from the days before Malayalam became fully distinguished from Tamil. In spite of claims by some Paradesi Jews that their ancestors' Ladino influenced the development of Judeo-Malayalam, so far no such influence, not even on the superficial lexical level, is found. There is, however, affiliation with Mappila Malayalam, especially of North Malabar, in words such as khabar or khabura (grave), and formations such as mayyattŭ āyi (മയ്യത്ത് ആയി) used by Muslims and śālōṃ āyi (ശാലോം ആയി) used by Jews for died (മരിച്ചു പോയി, mariccu pōyi in standard Malayalam). As with the parent language, Judeo-Malayalam also contains loanwords from Sanskrit and Pali as a result of the long-term affiliation of Malayalam, like all the other Dravidian languages, with Pali and Sanskrit through sacred and secular Buddhist and Hindu texts. Because the vast majority of scholarship regarding the Cochin Jews has concentrated on the ethnographic accounts in English provided by Paradesi Jews (sometimes also called White Jews), who immigrated to Kerala from Europe in the sixteenth century and later, the study of the status and role of Judeo-Malayalam has suffered neglect. Since their emigration to Israel, Cochin Jewish immigrants have participated in documenting and studying the last speakers of Judeo-Malayalam, mostly in Israel. In 2009, a documentation project was launched under the auspices of the Ben-Zvi Institute in Jerusalem. Digital copies can be obtained for any scholar who wishes to study Judeo-Malayalam. Features Loanwords Over the centuries, Malayalam borrowed Hebrew words. A few of them are given below: See also References Bibliography External links |
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[SOURCE: https://en.wikipedia.org/wiki/PlayStation_(console)#cite_note-FOOTNOTEAnderson199756-158] | [TOKENS: 10728] |
Contents PlayStation (console) The PlayStation[a] (codenamed PSX, abbreviated as PS, and retroactively PS1 or PS one) is a home video game console developed and marketed by Sony Computer Entertainment. It was released in Japan on 3 December 1994, followed by North America on 9 September 1995, Europe on 29 September 1995, and other regions following thereafter. As a fifth-generation console, the PlayStation primarily competed with the Nintendo 64 and the Sega Saturn. Sony began developing the PlayStation after a failed venture with Nintendo to create a CD-ROM peripheral for the Super Nintendo Entertainment System in the early 1990s. The console was primarily designed by Ken Kutaragi and Sony Computer Entertainment in Japan, while additional development was outsourced in the United Kingdom. An emphasis on 3D polygon graphics was placed at the forefront of the console's design. PlayStation game production was designed to be streamlined and inclusive, enticing the support of many third party developers. The console proved popular for its extensive game library, popular franchises, low retail price, and aggressive youth marketing which advertised it as the preferable console for adolescents and adults. Critically acclaimed games that defined the console include Gran Turismo, Crash Bandicoot, Spyro the Dragon, Tomb Raider, Resident Evil, Metal Gear Solid, Tekken 3, and Final Fantasy VII. Sony ceased production of the PlayStation on 23 March 2006—over eleven years after it had been released, and in the same year the PlayStation 3 debuted. More than 4,000 PlayStation games were released, with cumulative sales of 962 million units. The PlayStation signaled Sony's rise to power in the video game industry. It received acclaim and sold strongly; in less than a decade, it became the first computer entertainment platform to ship over 100 million units. Its use of compact discs heralded the game industry's transition from cartridges. The PlayStation's success led to a line of successors, beginning with the PlayStation 2 in 2000. In the same year, Sony released a smaller and cheaper model, the PS one. History The PlayStation was conceived by Ken Kutaragi, a Sony executive who managed a hardware engineering division and was later dubbed "the Father of the PlayStation". Kutaragi's interest in working with video games stemmed from seeing his daughter play games on Nintendo's Famicom. Kutaragi convinced Nintendo to use his SPC-700 sound processor in the Super Nintendo Entertainment System (SNES) through a demonstration of the processor's capabilities. His willingness to work with Nintendo was derived from both his admiration of the Famicom and conviction in video game consoles becoming the main home-use entertainment systems. Although Kutaragi was nearly fired because he worked with Nintendo without Sony's knowledge, president Norio Ohga recognised the potential in Kutaragi's chip and decided to keep him as a protégé. The inception of the PlayStation dates back to a 1988 joint venture between Nintendo and Sony. Nintendo had produced floppy disk technology to complement cartridges in the form of the Family Computer Disk System, and wanted to continue this complementary storage strategy for the SNES. Since Sony was already contracted to produce the SPC-700 sound processor for the SNES, Nintendo contracted Sony to develop a CD-ROM add-on, tentatively titled the "Play Station" or "SNES-CD". The PlayStation name had already been trademarked by Yamaha, but Nobuyuki Idei liked it so much that he agreed to acquire it for an undisclosed sum rather than search for an alternative. Sony was keen to obtain a foothold in the rapidly expanding video game market. Having been the primary manufacturer of the MSX home computer format, Sony had wanted to use their experience in consumer electronics to produce their own video game hardware. Although the initial agreement between Nintendo and Sony was about producing a CD-ROM drive add-on, Sony had also planned to develop a SNES-compatible Sony-branded console. This iteration was intended to be more of a home entertainment system, playing both SNES cartridges and a new CD format named the "Super Disc", which Sony would design. Under the agreement, Sony would retain sole international rights to every Super Disc game, giving them a large degree of control despite Nintendo's leading position in the video game market. Furthermore, Sony would also be the sole benefactor of licensing related to music and film software that it had been aggressively pursuing as a secondary application. The Play Station was to be announced at the 1991 Consumer Electronics Show (CES) in Las Vegas. However, Nintendo president Hiroshi Yamauchi was wary of Sony's increasing leverage at this point and deemed the original 1988 contract unacceptable upon realising it essentially handed Sony control over all games written on the SNES CD-ROM format. Although Nintendo was dominant in the video game market, Sony possessed a superior research and development department. Wanting to protect Nintendo's existing licensing structure, Yamauchi cancelled all plans for the joint Nintendo–Sony SNES CD attachment without telling Sony. He sent Nintendo of America president Minoru Arakawa (his son-in-law) and chairman Howard Lincoln to Amsterdam to form a more favourable contract with Dutch conglomerate Philips, Sony's rival. This contract would give Nintendo total control over their licences on all Philips-produced machines. Kutaragi and Nobuyuki Idei, Sony's director of public relations at the time, learned of Nintendo's actions two days before the CES was due to begin. Kutaragi telephoned numerous contacts, including Philips, to no avail. On the first day of the CES, Sony announced their partnership with Nintendo and their new console, the Play Station. At 9 am on the next day, in what has been called "the greatest ever betrayal" in the industry, Howard Lincoln stepped onto the stage and revealed that Nintendo was now allied with Philips and would abandon their work with Sony. Incensed by Nintendo's renouncement, Ohga and Kutaragi decided that Sony would develop their own console. Nintendo's contract-breaking was met with consternation in the Japanese business community, as they had broken an "unwritten law" of native companies not turning against each other in favour of foreign ones. Sony's American branch considered allying with Sega to produce a CD-ROM-based machine called the Sega Multimedia Entertainment System, but the Sega board of directors in Tokyo vetoed the idea when Sega of America CEO Tom Kalinske presented them the proposal. Kalinske recalled them saying: "That's a stupid idea, Sony doesn't know how to make hardware. They don't know how to make software either. Why would we want to do this?" Sony halted their research, but decided to develop what it had developed with Nintendo and Sega into a console based on the SNES. Despite the tumultuous events at the 1991 CES, negotiations between Nintendo and Sony were still ongoing. A deal was proposed: the Play Station would still have a port for SNES games, on the condition that it would still use Kutaragi's audio chip and that Nintendo would own the rights and receive the bulk of the profits. Roughly two hundred prototype machines were created, and some software entered development. Many within Sony were still opposed to their involvement in the video game industry, with some resenting Kutaragi for jeopardising the company. Kutaragi remained adamant that Sony not retreat from the growing industry and that a deal with Nintendo would never work. Knowing that they had to take decisive action, Sony severed all ties with Nintendo on 4 May 1992. To determine the fate of the PlayStation project, Ohga chaired a meeting in June 1992, consisting of Kutaragi and several senior Sony board members. Kutaragi unveiled a proprietary CD-ROM-based system he had been secretly working on which played games with immersive 3D graphics. Kutaragi was confident that his LSI chip could accommodate one million logic gates, which exceeded the capabilities of Sony's semiconductor division at the time. Despite gaining Ohga's enthusiasm, there remained opposition from a majority present at the meeting. Older Sony executives also opposed it, who saw Nintendo and Sega as "toy" manufacturers. The opposers felt the game industry was too culturally offbeat and asserted that Sony should remain a central player in the audiovisual industry, where companies were familiar with one another and could conduct "civili[s]ed" business negotiations. After Kutaragi reminded him of the humiliation he suffered from Nintendo, Ohga retained the project and became one of Kutaragi's most staunch supporters. Ohga shifted Kutaragi and nine of his team from Sony's main headquarters to Sony Music Entertainment Japan (SMEJ), a subsidiary of the main Sony group, so as to retain the project and maintain relationships with Philips for the MMCD development project. The involvement of SMEJ proved crucial to the PlayStation's early development as the process of manufacturing games on CD-ROM format was similar to that used for audio CDs, with which Sony's music division had considerable experience. While at SMEJ, Kutaragi worked with Epic/Sony Records founder Shigeo Maruyama and Akira Sato; both later became vice-presidents of the division that ran the PlayStation business. Sony Computer Entertainment (SCE) was jointly established by Sony and SMEJ to handle the company's ventures into the video game industry. On 27 October 1993, Sony publicly announced that it was entering the game console market with the PlayStation. According to Maruyama, there was uncertainty over whether the console should primarily focus on 2D, sprite-based graphics or 3D polygon graphics. After Sony witnessed the success of Sega's Virtua Fighter (1993) in Japanese arcades, the direction of the PlayStation became "instantly clear" and 3D polygon graphics became the console's primary focus. SCE president Teruhisa Tokunaka expressed gratitude for Sega's timely release of Virtua Fighter as it proved "just at the right time" that making games with 3D imagery was possible. Maruyama claimed that Sony further wanted to emphasise the new console's ability to utilise redbook audio from the CD-ROM format in its games alongside high quality visuals and gameplay. Wishing to distance the project from the failed enterprise with Nintendo, Sony initially branded the PlayStation the "PlayStation X" (PSX). Sony formed their European division and North American division, known as Sony Computer Entertainment Europe (SCEE) and Sony Computer Entertainment America (SCEA), in January and May 1995. The divisions planned to market the new console under the alternative branding "PSX" following the negative feedback regarding "PlayStation" in focus group studies. Early advertising prior to the console's launch in North America referenced PSX, but the term was scrapped before launch. The console was not marketed with Sony's name in contrast to Nintendo's consoles. According to Phil Harrison, much of Sony's upper management feared that the Sony brand would be tarnished if associated with the console, which they considered a "toy". Since Sony had no experience in game development, it had to rely on the support of third-party game developers. This was in contrast to Sega and Nintendo, which had versatile and well-equipped in-house software divisions for their arcade games and could easily port successful games to their home consoles. Recent consoles like the Atari Jaguar and 3DO suffered low sales due to a lack of developer support, prompting Sony to redouble their efforts in gaining the endorsement of arcade-savvy developers. A team from Epic Sony visited more than a hundred companies throughout Japan in May 1993 in hopes of attracting game creators with the PlayStation's technological appeal. Sony found that many disliked Nintendo's practices, such as favouring their own games over others. Through a series of negotiations, Sony acquired initial support from Namco, Konami, and Williams Entertainment, as well as 250 other development teams in Japan alone. Namco in particular was interested in developing for PlayStation since Namco rivalled Sega in the arcade market. Attaining these companies secured influential games such as Ridge Racer (1993) and Mortal Kombat 3 (1995), Ridge Racer being one of the most popular arcade games at the time, and it was already confirmed behind closed doors that it would be the PlayStation's first game by December 1993, despite Namco being a longstanding Nintendo developer. Namco's research managing director Shegeichi Nakamura met with Kutaragi in 1993 to discuss the preliminary PlayStation specifications, with Namco subsequently basing the Namco System 11 arcade board on PlayStation hardware and developing Tekken to compete with Virtua Fighter. The System 11 launched in arcades several months before the PlayStation's release, with the arcade release of Tekken in September 1994. Despite securing the support of various Japanese studios, Sony had no developers of their own by the time the PlayStation was in development. This changed in 1993 when Sony acquired the Liverpudlian company Psygnosis (later renamed SCE Liverpool) for US$48 million, securing their first in-house development team. The acquisition meant that Sony could have more launch games ready for the PlayStation's release in Europe and North America. Ian Hetherington, Psygnosis' co-founder, was disappointed after receiving early builds of the PlayStation and recalled that the console "was not fit for purpose" until his team got involved with it. Hetherington frequently clashed with Sony executives over broader ideas; at one point it was suggested that a television with a built-in PlayStation be produced. In the months leading up to the PlayStation's launch, Psygnosis had around 500 full-time staff working on games and assisting with software development. The purchase of Psygnosis marked another turning point for the PlayStation as it played a vital role in creating the console's development kits. While Sony had provided MIPS R4000-based Sony NEWS workstations for PlayStation development, Psygnosis employees disliked the thought of developing on these expensive workstations and asked Bristol-based SN Systems to create an alternative PC-based development system. Andy Beveridge and Martin Day, owners of SN Systems, had previously supplied development hardware for other consoles such as the Mega Drive, Atari ST, and the SNES. When Psygnosis arranged an audience for SN Systems with Sony's Japanese executives at the January 1994 CES in Las Vegas, Beveridge and Day presented their prototype of the condensed development kit, which could run on an ordinary personal computer with two extension boards. Impressed, Sony decided to abandon their plans for a workstation-based development system in favour of SN Systems's, thus securing a cheaper and more efficient method for designing software. An order of over 600 systems followed, and SN Systems supplied Sony with additional software such as an assembler, linker, and a debugger. SN Systems produced development kits for future PlayStation systems, including the PlayStation 2 and was bought out by Sony in 2005. Sony strived to make game production as streamlined and inclusive as possible, in contrast to the relatively isolated approach of Sega and Nintendo. Phil Harrison, representative director of SCEE, believed that Sony's emphasis on developer assistance reduced most time-consuming aspects of development. As well as providing programming libraries, SCE headquarters in London, California, and Tokyo housed technical support teams that could work closely with third-party developers if needed. Sony did not favour their own over non-Sony products, unlike Nintendo; Peter Molyneux of Bullfrog Productions admired Sony's open-handed approach to software developers and lauded their decision to use PCs as a development platform, remarking that "[it was] like being released from jail in terms of the freedom you have". Another strategy that helped attract software developers was the PlayStation's use of the CD-ROM format instead of traditional cartridges. Nintendo cartridges were expensive to manufacture, and the company controlled all production, prioritising their own games, while inexpensive compact disc manufacturing occurred at dozens of locations around the world. The PlayStation's architecture and interconnectability with PCs was beneficial to many software developers. The use of the programming language C proved useful, as it safeguarded future compatibility of the machine should developers decide to make further hardware revisions. Despite the inherent flexibility, some developers found themselves restricted due to the console's lack of RAM. While working on beta builds of the PlayStation, Molyneux observed that its MIPS processor was not "quite as bullish" compared to that of a fast PC and said that it took his team two weeks to port their PC code to the PlayStation development kits and another fortnight to achieve a four-fold speed increase. An engineer from Ocean Software, one of Europe's largest game developers at the time, thought that allocating RAM was a challenging aspect given the 3.5 megabyte restriction. Kutaragi said that while it would have been easy to double the amount of RAM for the PlayStation, the development team refrained from doing so to keep the retail cost down. Kutaragi saw the biggest challenge in developing the system to be balancing the conflicting goals of high performance, low cost, and being easy to program for, and felt he and his team were successful in this regard. Its technical specifications were finalised in 1993 and its design during 1994. The PlayStation name and its final design were confirmed during a press conference on May 10, 1994, although the price and release dates had not been disclosed yet. Sony released the PlayStation in Japan on 3 December 1994, a week after the release of the Sega Saturn, at a price of ¥39,800. Sales in Japan began with a "stunning" success with long queues in shops. Ohga later recalled that he realised how important PlayStation had become for Sony when friends and relatives begged for consoles for their children. PlayStation sold 100,000 units on the first day and two million units within six months, although the Saturn outsold the PlayStation in the first few weeks due to the success of Virtua Fighter. By the end of 1994, 300,000 PlayStation units were sold in Japan compared to 500,000 Saturn units. A grey market emerged for PlayStations shipped from Japan to North America and Europe, with buyers of such consoles paying up to £700. "When September 1995 arrived and Sony's Playstation roared out of the gate, things immediately felt different than [sic] they did with the Saturn launch earlier that year. Sega dropped the Saturn $100 to match the Playstation's $299 debut price, but sales weren't even close—Playstations flew out the door as fast as we could get them in stock. Before the release in North America, Sega and Sony presented their consoles at the first Electronic Entertainment Expo (E3) in Los Angeles on 11 May 1995. At their keynote presentation, Sega of America CEO Tom Kalinske revealed that their Saturn console would be released immediately to select retailers at a price of $399. Next came Sony's turn: Olaf Olafsson, the head of SCEA, summoned Steve Race, the head of development, to the conference stage, who said "$299" and left the audience with a round of applause. The attention to the Sony conference was further bolstered by the surprise appearance of Michael Jackson and the showcase of highly anticipated games, including Wipeout (1995), Ridge Racer and Tekken (1994). In addition, Sony announced that no games would be bundled with the console. Although the Saturn had released early in the United States to gain an advantage over the PlayStation, the surprise launch upset many retailers who were not informed in time, harming sales. Some retailers such as KB Toys responded by dropping the Saturn entirely. The PlayStation went on sale in North America on 9 September 1995. It sold more units within two days than the Saturn had in five months, with almost all of the initial shipment of 100,000 units sold in advance and shops across the country running out of consoles and accessories. The well-received Ridge Racer contributed to the PlayStation's early success, — with some critics considering it superior to Sega's arcade counterpart Daytona USA (1994) — as did Battle Arena Toshinden (1995). There were over 100,000 pre-orders placed and 17 games available on the market by the time of the PlayStation's American launch, in comparison to the Saturn's six launch games. The PlayStation released in Europe on 29 September 1995 and in Australia on 15 November 1995. By November it had already outsold the Saturn by three to one in the United Kingdom, where Sony had allocated a £20 million marketing budget during the Christmas season compared to Sega's £4 million. Sony found early success in the United Kingdom by securing listings with independent shop owners as well as prominent High Street chains such as Comet and Argos. Within its first year, the PlayStation secured over 20% of the entire American video game market. From September to the end of 1995, sales in the United States amounted to 800,000 units, giving the PlayStation a commanding lead over the other fifth-generation consoles,[b] though the SNES and Mega Drive from the fourth generation still outsold it. Sony reported that the attach rate of sold games and consoles was four to one. To meet increasing demand, Sony chartered jumbo jets and ramped up production in Europe and North America. By early 1996, the PlayStation had grossed $2 billion (equivalent to $4.106 billion 2025) from worldwide hardware and software sales. By late 1996, sales in Europe totalled 2.2 million units, including 700,000 in the UK. Approximately 400 PlayStation games were in development, compared to around 200 games being developed for the Saturn and 60 for the Nintendo 64. In India, the PlayStation was launched in test market during 1999–2000 across Sony showrooms, selling 100 units. Sony finally launched the console (PS One model) countrywide on 24 January 2002 with the price of Rs 7,990 and 26 games available from start. PlayStation was also doing well in markets where it was never officially released. For example, in Brazil, due to the registration of the trademark by a third company, the console could not be released, which was why the market was taken over by the officially distributed Sega Saturn during the first period, but as the Sega console withdraws, PlayStation imports and large piracy increased. In another market, China, the most popular 32-bit console was Sega Saturn, but after leaving the market, PlayStation grown with a base of 300,000 users until January 2000, although Sony China did not have plans to release it. The PlayStation was backed by a successful marketing campaign, allowing Sony to gain an early foothold in Europe and North America. Initially, PlayStation demographics were skewed towards adults, but the audience broadened after the first price drop. While the Saturn was positioned towards 18- to 34-year-olds, the PlayStation was initially marketed exclusively towards teenagers. Executives from both Sony and Sega reasoned that because younger players typically looked up to older, more experienced players, advertising targeted at teens and adults would draw them in too. Additionally, Sony found that adults reacted best to advertising aimed at teenagers; Lee Clow surmised that people who started to grow into adulthood regressed and became "17 again" when they played video games. The console was marketed with advertising slogans stylised as "LIVE IN YUR WRLD. PLY IN URS" (Live in Your World. Play in Ours.) and "U R NOT E" (red E). The four geometric shapes were derived from the symbols for the four buttons on the controller. Clow thought that by invoking such provocative statements, gamers would respond to the contrary and say "'Bullshit. Let me show you how ready I am.'" As the console's appeal enlarged, Sony's marketing efforts broadened from their earlier focus on mature players to specifically target younger children as well. Shortly after the PlayStation's release in Europe, Sony tasked marketing manager Geoff Glendenning with assessing the desires of a new target audience. Sceptical over Nintendo and Sega's reliance on television campaigns, Glendenning theorised that young adults transitioning from fourth-generation consoles would feel neglected by marketing directed at children and teenagers. Recognising the influence early 1990s underground clubbing and rave culture had on young people, especially in the United Kingdom, Glendenning felt that the culture had become mainstream enough to help cultivate PlayStation's emerging identity. Sony partnered with prominent nightclub owners such as Ministry of Sound and festival promoters to organise dedicated PlayStation areas where demonstrations of select games could be tested. Sheffield-based graphic design studio The Designers Republic was contracted by Sony to produce promotional materials aimed at a fashionable, club-going audience. Psygnosis' Wipeout in particular became associated with nightclub culture as it was widely featured in venues. By 1997, there were 52 nightclubs in the United Kingdom with dedicated PlayStation rooms. Glendenning recalled that he had discreetly used at least £100,000 a year in slush fund money to invest in impromptu marketing. In 1996, Sony expanded their CD production facilities in the United States due to the high demand for PlayStation games, increasing their monthly output from 4 million discs to 6.5 million discs. This was necessary because PlayStation sales were running at twice the rate of Saturn sales, and its lead dramatically increased when both consoles dropped in price to $199 that year. The PlayStation also outsold the Saturn at a similar ratio in Europe during 1996, with 2.2 million consoles sold in the region by the end of the year. Sales figures for PlayStation hardware and software only increased following the launch of the Nintendo 64. Tokunaka speculated that the Nintendo 64 launch had actually helped PlayStation sales by raising public awareness of the gaming market through Nintendo's added marketing efforts. Despite this, the PlayStation took longer to achieve dominance in Japan. Tokunaka said that, even after the PlayStation and Saturn had been on the market for nearly two years, the competition between them was still "very close", and neither console had led in sales for any meaningful length of time. By 1998, Sega, encouraged by their declining market share and significant financial losses, launched the Dreamcast as a last-ditch attempt to stay in the industry. Although its launch was successful, the technically superior 128-bit console was unable to subdue Sony's dominance in the industry. Sony still held 60% of the overall video game market share in North America at the end of 1999. Sega's initial confidence in their new console was undermined when Japanese sales were lower than expected, with disgruntled Japanese consumers reportedly returning their Dreamcasts in exchange for PlayStation software. On 2 March 1999, Sony officially revealed details of the PlayStation 2, which Kutaragi announced would feature a graphics processor designed to push more raw polygons than any console in history, effectively rivalling most supercomputers. The PlayStation continued to sell strongly at the turn of the new millennium: in June 2000, Sony released the PSOne, a smaller, redesigned variant which went on to outsell all other consoles in that year, including the PlayStation 2. In 2005, PlayStation became the first console to ship 100 million units with the PlayStation 2 later achieving this faster than its predecessor. The combined successes of both PlayStation consoles led to Sega retiring the Dreamcast in 2001, and abandoning the console business entirely. The PlayStation was eventually discontinued on 23 March 2006—over eleven years after its release, and less than a year before the debut of the PlayStation 3. Hardware The main microprocessor is a R3000 CPU made by LSI Logic operating at a clock rate of 33.8688 MHz and 30 MIPS. This 32-bit CPU relies heavily on the "cop2" 3D and matrix math coprocessor on the same die to provide the necessary speed to render complex 3D graphics. The role of the separate GPU chip is to draw 2D polygons and apply shading and textures to them: the rasterisation stage of the graphics pipeline. Sony's custom 16-bit sound chip supports ADPCM sources with up to 24 sound channels and offers a sampling rate of up to 44.1 kHz and music sequencing. It features 2 MB of main RAM, with an additional 1 MB of video RAM. The PlayStation has a maximum colour depth of 16.7 million true colours with 32 levels of transparency and unlimited colour look-up tables. The PlayStation can output composite, S-Video or RGB video signals through its AV Multi connector (with older models also having RCA connectors for composite), displaying resolutions from 256×224 to 640×480 pixels. Different games can use different resolutions. Earlier models also had proprietary parallel and serial ports that could be used to connect accessories or multiple consoles together; these were later removed due to a lack of usage. The PlayStation uses a proprietary video compression unit, MDEC, which is integrated into the CPU and allows for the presentation of full motion video at a higher quality than other consoles of its generation. Unusual for the time, the PlayStation lacks a dedicated 2D graphics processor; 2D elements are instead calculated as polygons by the Geometry Transfer Engine (GTE) so that they can be processed and displayed on screen by the GPU. While running, the GPU can also generate a total of 4,000 sprites and 180,000 polygons per second, in addition to 360,000 per second flat-shaded. The PlayStation went through a number of variants during its production run. Externally, the most notable change was the gradual reduction in the number of external connectors from the rear of the unit. This started with the original Japanese launch units; the SCPH-1000, released on 3 December 1994, was the only model that had an S-Video port, as it was removed from the next model. Subsequent models saw a reduction in number of parallel ports, with the final version only retaining one serial port. Sony marketed a development kit for amateur developers known as the Net Yaroze (meaning "Let's do it together" in Japanese). It was launched in June 1996 in Japan, and following public interest, was released the next year in other countries. The Net Yaroze allowed hobbyists to create their own games and upload them via an online forum run by Sony. The console was only available to buy through an ordering service and with the necessary documentation and software to program PlayStation games and applications through C programming compilers. On 7 July 2000, Sony released the PS One (stylised as "PS one" or "PSone"), a smaller, redesigned version of the original PlayStation. It was the highest-selling console through the end of the year, outselling all other consoles—including the PlayStation 2. In 2002, Sony released a 5-inch (130 mm) LCD screen add-on for the PS One, referred to as the "Combo pack". It also included a car cigarette lighter adaptor adding an extra layer of portability. Production of the LCD "Combo Pack" ceased in 2004, when the popularity of the PlayStation began to wane in markets outside Japan. A total of 28.15 million PS One units had been sold by the time it was discontinued in March 2006. Three iterations of the PlayStation's controller were released over the console's lifespan. The first controller, the PlayStation controller, was released alongside the PlayStation in December 1994. It features four individual directional buttons (as opposed to a conventional D-pad), a pair of shoulder buttons on both sides, Start and Select buttons in the centre, and four face buttons consisting of simple geometric shapes: a green triangle, red circle, blue cross, and a pink square (, , , ). Rather than depicting traditionally used letters or numbers onto its buttons, the PlayStation controller established a trademark which would be incorporated heavily into the PlayStation brand. Teiyu Goto, the designer of the original PlayStation controller, said that the circle and cross represent "yes" and "no", respectively (though this layout is reversed in Western versions); the triangle symbolises a point of view and the square is equated to a sheet of paper to be used to access menus. The European and North American models of the original PlayStation controllers are roughly 10% larger than its Japanese variant, to account for the fact the average person in those regions has larger hands than the average Japanese person. Sony's first analogue gamepad, the PlayStation Analog Joystick (often erroneously referred to as the "Sony Flightstick"), was first released in Japan in April 1996. Featuring two parallel joysticks, it uses potentiometer technology previously used on consoles such as the Vectrex; instead of relying on binary eight-way switches, the controller detects minute angular changes through the entire range of motion. The stick also features a thumb-operated digital hat switch on the right joystick, corresponding to the traditional D-pad, and used for instances when simple digital movements were necessary. The Analog Joystick sold poorly in Japan due to its high cost and cumbersome size. The increasing popularity of 3D games prompted Sony to add analogue sticks to its controller design to give users more freedom over their movements in virtual 3D environments. The first official analogue controller, the Dual Analog Controller, was revealed to the public in a small glass booth at the 1996 PlayStation Expo in Japan, and released in April 1997 to coincide with the Japanese releases of analogue-capable games Tobal 2 and Bushido Blade. In addition to the two analogue sticks (which also introduced two new buttons mapped to clicking in the analogue sticks), the Dual Analog controller features an "Analog" button and LED beneath the "Start" and "Select" buttons which toggles analogue functionality on or off. The controller also features rumble support, though Sony decided that haptic feedback would be removed from all overseas iterations before the United States release. A Sony spokesman stated that the feature was removed for "manufacturing reasons", although rumours circulated that Nintendo had attempted to legally block the release of the controller outside Japan due to similarities with the Nintendo 64 controller's Rumble Pak. However, a Nintendo spokesman denied that Nintendo took legal action. Next Generation's Chris Charla theorised that Sony dropped vibration feedback to keep the price of the controller down. In November 1997, Sony introduced the DualShock controller. Its name derives from its use of two (dual) vibration motors (shock). Unlike its predecessor, its analogue sticks feature textured rubber grips, longer handles, slightly different shoulder buttons and has rumble feedback included as standard on all versions. The DualShock later replaced its predecessors as the default controller. Sony released a series of peripherals to add extra layers of functionality to the PlayStation. Such peripherals include memory cards, the PlayStation Mouse, the PlayStation Link Cable, the Multiplayer Adapter (a four-player multitap), the Memory Drive (a disk drive for 3.5-inch floppy disks), the GunCon (a light gun), and the Glasstron (a monoscopic head-mounted display). Released exclusively in Japan, the PocketStation is a memory card peripheral which acts as a miniature personal digital assistant. The device features a monochrome liquid crystal display (LCD), infrared communication capability, a real-time clock, built-in flash memory, and sound capability. Sharing similarities with the Dreamcast's VMU peripheral, the PocketStation was typically distributed with certain PlayStation games, enhancing them with added features. The PocketStation proved popular in Japan, selling over five million units. Sony planned to release the peripheral outside Japan but the release was cancelled, despite receiving promotion in Europe and North America. In addition to playing games, most PlayStation models are equipped to play CD-Audio. The Asian model SCPH-5903 can also play Video CDs. Like most CD players, the PlayStation can play songs in a programmed order, shuffle the playback order of the disc and repeat one song or the entire disc. Later PlayStation models use a music visualisation function called SoundScope. This function, as well as a memory card manager, is accessed by starting the console without either inserting a game or closing the CD tray, thereby accessing a graphical user interface (GUI) for the PlayStation BIOS. The GUI for the PS One and PlayStation differ depending on the firmware version: the original PlayStation GUI had a dark blue background with rainbow graffiti used as buttons, while the early PAL PlayStation and PS One GUI had a grey blocked background with two icons in the middle. PlayStation emulation is versatile and can be run on numerous modern devices. Bleem! was a commercial emulator which was released for IBM-compatible PCs and the Dreamcast in 1999. It was notable for being aggressively marketed during the PlayStation's lifetime, and was the centre of multiple controversial lawsuits filed by Sony. Bleem! was programmed in assembly language, which allowed it to emulate PlayStation games with improved visual fidelity, enhanced resolutions, and filtered textures that was not possible on original hardware. Sony sued Bleem! two days after its release, citing copyright infringement and accusing the company of engaging in unfair competition and patent infringement by allowing use of PlayStation BIOSs on a Sega console. Bleem! were subsequently forced to shut down in November 2001. Sony was aware that using CDs for game distribution could have left games vulnerable to piracy, due to the growing popularity of CD-R and optical disc drives with burning capability. To preclude illegal copying, a proprietary process for PlayStation disc manufacturing was developed that, in conjunction with an augmented optical drive in Tiger H/E assembly, prevented burned copies of games from booting on an unmodified console. Specifically, all genuine PlayStation discs were printed with a small section of deliberate irregular data, which the PlayStation's optical pick-up was capable of detecting and decoding. Consoles would not boot game discs without a specific wobble frequency contained in the data of the disc pregap sector (the same system was also used to encode discs' regional lockouts). This signal was within Red Book CD tolerances, so PlayStation discs' actual content could still be read by a conventional disc drive; however, the disc drive could not detect the wobble frequency (therefore duplicating the discs omitting it), since the laser pick-up system of any optical disc drive would interpret this wobble as an oscillation of the disc surface and compensate for it in the reading process. Early PlayStations, particularly early 1000 models, experience skipping full-motion video or physical "ticking" noises from the unit. The problems stem from poorly placed vents leading to overheating in some environments, causing the plastic mouldings inside the console to warp slightly and create knock-on effects with the laser assembly. The solution is to sit the console on a surface which dissipates heat efficiently in a well vented area or raise the unit up slightly from its resting surface. Sony representatives also recommended unplugging the PlayStation when it is not in use, as the system draws in a small amount of power (and therefore heat) even when turned off. The first batch of PlayStations use a KSM-440AAM laser unit, whose case and movable parts are all built out of plastic. Over time, the plastic lens sled rail wears out—usually unevenly—due to friction. The placement of the laser unit close to the power supply accelerates wear, due to the additional heat, which makes the plastic more vulnerable to friction. Eventually, one side of the lens sled will become so worn that the laser can tilt, no longer pointing directly at the CD; after this, games will no longer load due to data read errors. Sony fixed the problem by making the sled out of die-cast metal and placing the laser unit further away from the power supply on later PlayStation models. Due to an engineering oversight, the PlayStation does not produce a proper signal on several older models of televisions, causing the display to flicker or bounce around the screen. Sony decided not to change the console design, since only a small percentage of PlayStation owners used such televisions, and instead gave consumers the option of sending their PlayStation unit to a Sony service centre to have an official modchip installed, allowing play on older televisions. Game library The PlayStation featured a diverse game library which grew to appeal to all types of players. Critically acclaimed PlayStation games included Final Fantasy VII (1997), Crash Bandicoot (1996), Spyro the Dragon (1998), Metal Gear Solid (1998), all of which became established franchises. Final Fantasy VII is credited with allowing role-playing games to gain mass-market appeal outside Japan, and is considered one of the most influential and greatest video games ever made. The PlayStation's bestselling game is Gran Turismo (1997), which sold 10.85 million units. After the PlayStation's discontinuation in 2006, the cumulative software shipment was 962 million units. Following its 1994 launch in Japan, early games included Ridge Racer, Crime Crackers, King's Field, Motor Toon Grand Prix, Toh Shin Den (i.e. Battle Arena Toshinden), and Kileak: The Blood. The first two games available at its later North American launch were Jumping Flash! (1995) and Ridge Racer, with Jumping Flash! heralded as an ancestor for 3D graphics in console gaming. Wipeout, Air Combat, Twisted Metal, Warhawk and Destruction Derby were among the popular first-year games, and the first to be reissued as part of Sony's Greatest Hits or Platinum range. At the time of the PlayStation's first Christmas season, Psygnosis had produced around 70% of its launch catalogue; their breakthrough racing game Wipeout was acclaimed for its techno soundtrack and helped raise awareness of Britain's underground music community. Eidos Interactive's action-adventure game Tomb Raider contributed substantially to the success of the console in 1996, with its main protagonist Lara Croft becoming an early gaming icon and garnering unprecedented media promotion. Licensed tie-in video games of popular films were also prevalent; Argonaut Games' 2001 adaptation of Harry Potter and the Philosopher's Stone went on to sell over eight million copies late in the console's lifespan. Third-party developers committed largely to the console's wide-ranging game catalogue even after the launch of the PlayStation 2; some of the notable exclusives in this era include Harry Potter and the Philosopher's Stone, Fear Effect 2: Retro Helix, Syphon Filter 3, C-12: Final Resistance, Dance Dance Revolution Konamix and Digimon World 3.[c] Sony assisted with game reprints as late as 2008 with Metal Gear Solid: The Essential Collection, this being the last PlayStation game officially released and licensed by Sony. Initially, in the United States, PlayStation games were packaged in long cardboard boxes, similar to non-Japanese 3DO and Saturn games. Sony later switched to the jewel case format typically used for audio CDs and Japanese video games, as this format took up less retailer shelf space (which was at a premium due to the large number of PlayStation games being released), and focus testing showed that most consumers preferred this format. Reception The PlayStation was mostly well received upon release. Critics in the west generally welcomed the new console; the staff of Next Generation reviewed the PlayStation a few weeks after its North American launch, where they commented that, while the CPU is "fairly average", the supplementary custom hardware, such as the GPU and sound processor, is stunningly powerful. They praised the PlayStation's focus on 3D, and complemented the comfort of its controller and the convenience of its memory cards. Giving the system 41⁄2 out of 5 stars, they concluded, "To succeed in this extremely cut-throat market, you need a combination of great hardware, great games, and great marketing. Whether by skill, luck, or just deep pockets, Sony has scored three out of three in the first salvo of this war." Albert Kim from Entertainment Weekly praised the PlayStation as a technological marvel, rivalling that of Sega and Nintendo. Famicom Tsūshin scored the console a 19 out of 40, lower than the Saturn's 24 out of 40, in May 1995. In a 1997 year-end review, a team of five Electronic Gaming Monthly editors gave the PlayStation scores of 9.5, 8.5, 9.0, 9.0, and 9.5—for all five editors, the highest score they gave to any of the five consoles reviewed in the issue. They lauded the breadth and quality of the games library, saying it had vastly improved over previous years due to developers mastering the system's capabilities in addition to Sony revising their stance on 2D and role playing games. They also complimented the low price point of the games compared to the Nintendo 64's, and noted that it was the only console on the market that could be relied upon to deliver a solid stream of games for the coming year, primarily due to third party developers almost unanimously favouring it over its competitors. Legacy SCE was an upstart in the video game industry in late 1994, as the video game market in the early 1990s was dominated by Nintendo and Sega. Nintendo had been the clear leader in the industry since the introduction of the Nintendo Entertainment System in 1985 and the Nintendo 64 was initially expected to maintain this position. The PlayStation's target audience included the generation which was the first to grow up with mainstream video games, along with 18- to 29-year-olds who were not the primary focus of Nintendo. By the late 1990s, Sony became a highly regarded console brand due to the PlayStation, with a significant lead over second-place Nintendo, while Sega was relegated to a distant third. The PlayStation became the first "computer entertainment platform" to ship over 100 million units worldwide, with many critics attributing the console's success to third-party developers. It remains the sixth best-selling console of all time as of 2025[update], with a total of 102.49 million units sold. Around 7,900 individual games were published for the console during its 11-year life span, the second-most games ever produced for a console. Its success resulted in a significant financial boon for Sony as profits from their video game division contributed to 23%. Sony's next-generation PlayStation 2, which is backward compatible with the PlayStation's DualShock controller and games, was announced in 1999 and launched in 2000. The PlayStation's lead in installed base and developer support paved the way for the success of its successor, which overcame the earlier launch of the Sega's Dreamcast and then fended off competition from Microsoft's newcomer Xbox and Nintendo's GameCube. The PlayStation 2's immense success and failure of the Dreamcast were among the main factors which led to Sega abandoning the console market. To date, five PlayStation home consoles have been released, which have continued the same numbering scheme, as well as two portable systems. The PlayStation 3 also maintained backward compatibility with original PlayStation discs. Hundreds of PlayStation games have been digitally re-released on the PlayStation Portable, PlayStation 3, PlayStation Vita, PlayStation 4, and PlayStation 5. The PlayStation has often ranked among the best video game consoles. In 2018, Retro Gamer named it the third best console, crediting its sophisticated 3D capabilities as one of its key factors in gaining mass success, and lauding it as a "game-changer in every sense possible". In 2009, IGN ranked the PlayStation the seventh best console in their list, noting its appeal towards older audiences to be a crucial factor in propelling the video game industry, as well as its assistance in transitioning game industry to use the CD-ROM format. Keith Stuart from The Guardian likewise named it as the seventh best console in 2020, declaring that its success was so profound it "ruled the 1990s". In January 2025, Lorentio Brodesco announced the nsOne project, attempting to reverse engineer PlayStation's motherboard. Brodesco stated that "detailed documentation on the original motherboard was either incomplete or entirely unavailable". The project was successfully crowdfunded via Kickstarter. In June, Brodesco manufactured the first working motherboard, promising to bring a fully rooted version with multilayer routing as well as documentation and design files in the near future. The success of the PlayStation contributed to the demise of cartridge-based home consoles. While not the first system to use an optical disc format, it was the first highly successful one, and ended up going head-to-head with the proprietary cartridge-relying Nintendo 64,[d] which the industry had expected to use CDs like PlayStation. After the demise of the Sega Saturn, Nintendo was left as Sony's main competitor in Western markets. Nintendo chose not to use CDs for the Nintendo 64; they were likely concerned with the proprietary cartridge format's ability to help enforce copy protection, given their substantial reliance on licensing and exclusive games for their revenue. Besides their larger capacity, CD-ROMs could be produced in bulk quantities at a much faster rate than ROM cartridges, a week compared to two to three months. Further, the cost of production per unit was far cheaper, allowing Sony to offer games about 40% lower cost to the user compared to ROM cartridges while still making the same amount of net revenue. In Japan, Sony published fewer copies of a wide variety of games for the PlayStation as a risk-limiting step, a model that had been used by Sony Music for CD audio discs. The production flexibility of CD-ROMs meant that Sony could produce larger volumes of popular games to get onto the market quickly, something that could not be done with cartridges due to their manufacturing lead time. The lower production costs of CD-ROMs also allowed publishers an additional source of profit: budget-priced reissues of games which had already recouped their development costs. Tokunaka remarked in 1996: Choosing CD-ROM is one of the most important decisions that we made. As I'm sure you understand, PlayStation could just as easily have worked with masked ROM [cartridges]. The 3D engine and everything—the whole PlayStation format—is independent of the media. But for various reasons (including the economies for the consumer, the ease of the manufacturing, inventory control for the trade, and also the software publishers) we deduced that CD-ROM would be the best media for PlayStation. The increasing complexity of developing games pushed cartridges to their storage limits and gradually discouraged some third-party developers. Part of the CD format's appeal to publishers was that they could be produced at a significantly lower cost and offered more production flexibility to meet demand. As a result, some third-party developers switched to the PlayStation, including Square and Enix, whose Final Fantasy VII and Dragon Quest VII respectively had been planned for the Nintendo 64 (both companies later merged to form Square Enix). Other developers released fewer games for the Nintendo 64 (Konami, releasing only thirteen N64 games but over fifty on the PlayStation). Nintendo 64 game releases were less frequent than the PlayStation's, with many being developed by either Nintendo themselves or second-parties such as Rare. The PlayStation Classic is a dedicated video game console made by Sony Interactive Entertainment that emulates PlayStation games. It was announced in September 2018 at the Tokyo Game Show, and released on 3 December 2018, the 24th anniversary of the release of the original console. As a dedicated console, the PlayStation Classic features 20 pre-installed games; the games run off the open source emulator PCSX. The console is bundled with two replica wired PlayStation controllers (those without analogue sticks), an HDMI cable, and a USB-Type A cable. Internally, the console uses a MediaTek MT8167a Quad A35 system on a chip with four central processing cores clocked at @ 1.5 GHz and a Power VR GE8300 graphics processing unit. It includes 16 GB of eMMC flash storage and 1 Gigabyte of DDR3 SDRAM. The PlayStation Classic is 45% smaller than the original console. The PlayStation Classic received negative reviews from critics and was compared unfavorably to Nintendo's rival Nintendo Entertainment System Classic Edition and Super Nintendo Entertainment System Classic Edition. Criticism was directed at its meagre game library, user interface, emulation quality, use of PAL versions for certain games, use of the original controller, and high retail price, though the console's design received praise. The console sold poorly. See also Notes References |
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Contents Lod Lod (Hebrew: לוד, fully vocalized: לֹד), also known as Lydda (Ancient Greek: Λύδδα) and Lidd (Arabic: اللِّدّ, romanized: al-Lidd, or اللُّدّ, al-Ludd), is a city 15 km (9+1⁄2 mi) southeast of Tel Aviv and 40 km (25 mi) northwest of Jerusalem in the Central District of Israel. It is situated between the lower Shephelah on the east and the coastal plain on the west. The city had a population of 90,814 in 2023. Lod has been inhabited since at least the Neolithic period. It is mentioned a few times in the Hebrew Bible and in the New Testament. Between the 5th century BCE and up until the late Roman period, it was a prominent center for Jewish scholarship and trade. Around 200 CE, the city became a Roman colony and was renamed Diospolis (Ancient Greek: Διόσπολις, lit. 'city of Zeus'). Tradition identifies Lod as the 4th century martyrdom site of Saint George; the Church of Saint George and Mosque of Al-Khadr located in the city is believed to have housed his remains. Following the Arab conquest of the Levant, Lod served as the capital of Jund Filastin; however, a few decades later, the seat of power was transferred to Ramla, and Lod slipped in importance. Under Crusader rule, the city was a Catholic diocese of the Latin Church and it remains a titular see to this day.[citation needed] Lod underwent a major change in its population in the mid-20th century. Exclusively Palestinian Arab in 1947, Lod was part of the area designated for an Arab state in the United Nations Partition Plan for Palestine; however, in July 1948, the city was occupied by the Israel Defense Forces, and most of its Arab inhabitants were expelled in the Palestinian expulsion from Lydda and Ramle. The city was largely resettled by Jewish immigrants, most of them expelled from Arab countries. Today, Lod is one of Israel's mixed cities, with an Arab population of 30%. Lod is one of Israel's major transportation hubs. The main international airport, Ben Gurion Airport, is located 8 km (5 miles) north of the city. The city is also a major railway and road junction. Religious references The Hebrew name Lod appears in the Hebrew Bible as a town of Benjamin, founded along with Ono by Shamed or Shamer (1 Chronicles 8:12; Ezra 2:33; Nehemiah 7:37; 11:35). In Ezra 2:33, it is mentioned as one of the cities whose inhabitants returned after the Babylonian captivity. Lod is not mentioned among the towns allocated to the tribe of Benjamin in Joshua 18:11–28. The name Lod derives from a tri-consonantal root not extant in Northwest Semitic, but only in Arabic (“to quarrel; withhold, hinder”). An Arabic etymology of such an ancient name is unlikely (the earliest attestation is from the Achaemenid period). In the New Testament, the town appears in its Greek form, Lydda, as the site of Peter's healing of Aeneas in Acts 9:32–38. The city is also mentioned in an Islamic hadith as the location of the battlefield where the false messiah (al-Masih ad-Dajjal) will be slain before the Day of Judgment. History The first occupation dates to the Neolithic in the Near East and is associated with the Lodian culture. Occupation continued in the Levant Chalcolithic. Pottery finds have dated the initial settlement in the area now occupied by the town to 5600–5250 BCE. In the Early Bronze, it was an important settlement in the central coastal plain between the Judean Shephelah and the Mediterranean coast, along Nahal Ayalon. Other important nearby sites were Tel Dalit, Tel Bareqet, Khirbat Abu Hamid (Shoham North), Tel Afeq, Azor and Jaffa. Two architectural phases belong to the late EB I in Area B. The first phase had a mudbrick wall, while the late phase included a circulat stone structure. Later excavations have produced an occupation later, Stratum IV. It consists of two phases, Stratum IVb with mudbrick wall on stone foundations and rounded exterior corners. In Stratum IVa there was a mudbrick wall with no stone foundations, with imported Egyptian potter and local pottery imitations. Another excavations revealed nine occupation strata. Strata VI-III belonged to Early Bronze IB. The material culture showed Egyptian imports in strata V and IV. Occupation continued into Early Bronze II with four strata (V-II). There was continuity in the material culture and indications of centralized urban planning. North to the tell were scattered MB II burials. The earliest written record is in a list of Canaanite towns drawn up by the Egyptian pharaoh Thutmose III at Karnak in 1465 BCE. From the fifth century BCE until the Roman period, the city was a centre of Jewish scholarship and commerce. According to British historian Martin Gilbert, during the Hasmonean period, Jonathan Maccabee and his brother, Simon Maccabaeus, enlarged the area under Jewish control, which included conquering the city. The Jewish community in Lod during the Mishnah and Talmud era is described in a significant number of sources, including information on its institutions, demographics, and way of life. The city reached its height as a Jewish center between the First Jewish-Roman War and the Bar Kokhba revolt, and again in the days of Judah ha-Nasi and the start of the Amoraim period. The city was then the site of numerous public institutions, including schools, study houses, and synagogues. In 43 BC, Cassius, the Roman governor of Syria, sold the inhabitants of Lod into slavery, but they were set free two years later by Mark Antony. During the First Jewish–Roman War, the Roman proconsul of Syria, Cestius Gallus, razed the town on his way to Jerusalem in Tishrei 66 CE. According to Josephus, "[he] found the city deserted, for the entire population had gone up to Jerusalem for the Feast of Tabernacles. He killed fifty people whom he found, burned the town and marched on". Lydda was occupied by Emperor Vespasian in 68 CE. In the period following the destruction of Jerusalem in 70 CE, Rabbi Tarfon, who appears in many Tannaitic and Jewish legal discussions, served as a rabbinic authority in Lod. During the Kitos War, 115–117 CE, the Roman army laid siege to Lod, where the rebel Jews had gathered under the leadership of Julian and Pappos. Torah study was outlawed by the Romans and pursued mostly in the underground. The distress became so great, the patriarch Rabban Gamaliel II, who was shut up there and died soon afterwards, permitted fasting on Ḥanukkah. Other rabbis disagreed with this ruling. Lydda was next taken and many of the Jews were executed; the "slain of Lydda" are often mentioned in words of reverential praise in the Talmud. In 200 CE, emperor Septimius Severus elevated the town to the status of a city, calling it Colonia Lucia Septimia Severa Diospolis. The name Diospolis ("City of Zeus") may have been bestowed earlier, possibly by Hadrian. At that point, most of its inhabitants were Christian. The earliest known bishop is Aëtius, a friend of Arius. During the following century (200-300CE), it's said that Joshua ben Levi founded a yeshiva in Lod. In December 415, the Council of Diospolis was held here to try Pelagius; he was acquitted. In the sixth century, the city was renamed Georgiopolis after St. George, a soldier in the guard of the emperor Diocletian, who was born there between 256 and 285 CE. The Church of Saint George and Mosque of Al-Khadr is named for him. The 6th-century Madaba map shows Lydda as an unwalled city with a cluster of buildings under a black inscription reading "Lod, also Lydea, also Diospolis". An isolated large building with a semicircular colonnaded plaza in front of it might represent the St George shrine. After the Muslim conquest of Palestine by Amr ibn al-'As in 636 CE, Lod which was referred to as "al-Ludd" in Arabic served as the capital of Jund Filastin ("Military District of Palaestina") before the seat of power was moved to nearby Ramla during the reign of the Umayyad Caliph Suleiman ibn Abd al-Malik in 715–716. The population of al-Ludd was relocated to Ramla, as well. With the relocation of its inhabitants and the construction of the White Mosque in Ramla, al-Ludd lost its importance and fell into decay. The city was visited by the local Arab geographer al-Muqaddasi in 985, when it was under the Fatimid Caliphate, and was noted for its Great Mosque which served the residents of al-Ludd, Ramla, and the nearby villages. He also wrote of the city's "wonderful church (of St. George) at the gate of which Christ will slay the Antichrist." The Crusaders occupied the city in 1099 and named it St Jorge de Lidde. It was briefly conquered by Saladin, but retaken by the Crusaders in 1191. For the English Crusaders, it was a place of great significance as the birthplace of Saint George. The Crusaders made it the seat of a Latin Church diocese, and it remains a titular see. It owed the service of 10 knights and 20 sergeants, and it had its own burgess court during this era. In 1226, Ayyubid Syrian geographer Yaqut al-Hamawi visited al-Ludd and stated it was part of the Jerusalem District during Ayyubid rule. Sultan Baybars brought Lydda again under Muslim control by 1267–8. According to Qalqashandi, Lydda was an administrative centre of a wilaya during the fourteenth and fifteenth century in the Mamluk empire. Mujir al-Din described it as a pleasant village with an active Friday mosque. During this time, Lydda was a station on the postal route between Cairo and Damascus. In 1517, Lydda was incorporated into the Ottoman Empire as part of the Damascus Eyalet, and in the 1550s, the revenues of Lydda were designated for the new waqf of Hasseki Sultan Imaret in Jerusalem, established by Hasseki Hurrem Sultan (Roxelana), the wife of Suleiman the Magnificent. By 1596 Lydda was a part of the nahiya ("subdistrict") of Ramla, which was under the administration of the liwa ("district") of Gaza. It had a population of 241 households and 14 bachelors who were all Muslims, and 233 households who were Christians. They paid a fixed tax-rate of 33,3 % on agricultural products, including wheat, barley, summer crops, vineyards, fruit trees, sesame, special product ("dawalib" =spinning wheels), goats and beehives, in addition to occasional revenues and market toll, a total of 45,000 Akçe. All of the revenue went to the Waqf. In 1051 AH/1641/2, the Bedouin tribe of al-Sawālima from around Jaffa attacked the villages of Subṭāra, Bayt Dajan, al-Sāfiriya, Jindās, Lydda and Yāzūr belonging to Waqf Haseki Sultan. The village appeared as Lydda, though misplaced, on the map of Pierre Jacotin compiled in 1799. Missionary William M. Thomson visited Lydda in the mid-19th century, describing it as a "flourishing village of some 2,000 inhabitants, imbosomed in noble orchards of olive, fig, pomegranate, mulberry, sycamore, and other trees, surrounded every way by a very fertile neighbourhood. The inhabitants are evidently industrious and thriving, and the whole country between this and Ramleh is fast being filled up with their flourishing orchards. Rarely have I beheld a rural scene more delightful than this presented in early harvest ... It must be seen, heard, and enjoyed to be appreciated." In 1869, the population of Ludd was given as: 55 Catholics, 1,940 "Greeks", 5 Protestants and 4,850 Muslims. In 1870, the Church of Saint George was rebuilt. In 1892, the first railway station in the entire region was established in the city. In the second half of the 19th century, Jewish merchants migrated to the city, but left after the 1921 Jaffa riots. In 1882, the Palestine Exploration Fund's Survey of Western Palestine described Lod as "A small town, standing among enclosure of prickly pear, and having fine olive groves around it, especially to the south. The minaret of the mosque is a very conspicuous object over the whole of the plain. The inhabitants are principally Moslim, though the place is the seat of a Greek bishop resident of Jerusalem. The Crusading church has lately been restored, and is used by the Greeks. Wells are found in the gardens...." From 1918, Lydda was under the administration of the British Mandate in Palestine, as per a League of Nations decree that followed the Great War. During the Second World War, the British set up supply posts in and around Lydda and its railway station, also building an airport that was renamed Ben Gurion Airport after the death of Israel's first prime minister in 1973. At the time of the 1922 census of Palestine, Lydda had a population of 8,103 inhabitants (7,166 Muslims, 926 Christians, and 11 Jews), the Christians were 921 Orthodox, 4 Roman Catholics and 1 Melkite. This had increased by the 1931 census to 11,250 (10,002 Muslims, 1,210 Christians, 28 Jews, and 10 Bahai), in a total of 2475 residential houses. In 1938, Lydda had a population of 12,750. In 1945, Lydda had a population of 16,780 (14,910 Muslims, 1,840 Christians, 20 Jews and 10 "other"). Until 1948, Lydda was an Arab town with a population of around 20,000—18,500 Muslims and 1,500 Christians. In 1947, the United Nations proposed dividing Mandatory Palestine into two states, one Jewish state and one Arab; Lydda was to form part of the proposed Arab state. In the ensuing war, Israel captured Arab towns outside the area the UN had allotted it, including Lydda. In December 1947, thirteen Jewish passengers in a seven-car convoy to Ben Shemen Youth Village were ambushed and murdered.In a separate incident, three Jewish youths, two men and a woman were captured, then raped and murdered in a neighbouring village. Their bodies were paraded in Lydda’s principal street. The Israel Defense Forces entered Lydda on 11 July 1948. The following day, under the impression that it was under attack, the 3rd Battalion was ordered to shoot anyone "seen on the streets". According to Israel, 250 Arabs were killed. Other estimates are higher: Arab historian Aref al Aref estimated 400, and Nimr al Khatib 1,700. In 1948, the population rose to 50,000 during the Nakba, as Arab refugees fleeing other areas made their way there. A key event was the Palestinian expulsion from Lydda and Ramle, with the expulsion of 50,000-70,000 Palestinians from Lydda and Ramle by the Israel Defense Forces. All but 700 to 1,056 were expelled by order of the Israeli high command, and forced to walk 17 km (10+1⁄2 mi) to the Jordanian Arab Legion lines. Estimates of those who died from exhaustion and dehydration vary from a handful to 355. The town was subsequently sacked by the Israeli army. Some scholars, including Ilan Pappé, characterize this as ethnic cleansing. The few hundred Arabs who remained in the city were soon outnumbered by the influx of Jews who immigrated to Lod from August 1948 onward, most of them from Arab countries. As a result, Lod became a predominantly Jewish town. After the establishment of the state, the biblical name Lod was readopted. The Jewish immigrants who settled Lod came in waves, first from Morocco and Tunisia, later from Ethiopia, and then from the former Soviet Union. Since 2008, many urban development projects have been undertaken to improve the image of the city. Upscale neighbourhoods have been built, among them Ganei Ya'ar and Ahisemah, expanding the city to the east. According to a 2010 report in the Economist, a three-meter-high wall was built between Jewish and Arab neighbourhoods and construction in Jewish areas was given priority over construction in Arab neighborhoods. The newspaper says that violent crime in the Arab sector revolves mainly around family feuds over turf and honour crimes. In 2010, the Lod Community Foundation organised an event for representatives of bicultural youth movements, volunteer aid organisations, educational start-ups, businessmen, sports organizations, and conservationists working on programmes to better the city. In the 2021 Israel–Palestine crisis, a state of emergency was declared in Lod after Arab rioting led to the death of an Israeli Jew. The Mayor of Lod, Yair Revivio, urged Prime Minister of Israel Benjamin Netanyahu to deploy Israel Border Police to restore order in the city. This was the first time since 1966 that Israel had declared this kind of emergency lockdown. International media noted that both Jewish and Palestinian mobs were active in Lod, but the "crackdown came for one side" only. Demographics In the 19th century and until the Lydda Death March, Lod was an exclusively Muslim-Christian town, with an estimated 6,850 inhabitants, of whom approximately 2,000 (29%) were Christian. According to the Israel Central Bureau of Statistics (CBS), the population of Lod in 2010 was 69,500 people. According to the 2019 census, the population of Lod was 77,223, of which 53,581 people, comprising 69.4% of the city's population, were classified as "Jews and Others", and 23,642 people, comprising 30.6% as "Arab". Education According to CBS, 38 schools and 13,188 pupils are in the city. They are spread out as 26 elementary schools and 8,325 elementary school pupils, and 13 high schools and 4,863 high school pupils. About 52.5% of 12th-grade pupils were entitled to a matriculation certificate in 2001.[citation needed] Economy The airport and related industries are a major source of employment for the residents of Lod. Other important factories in the city are the communication equipment company "Talard", "Cafe-Co" - a subsidiary of the Strauss Group and "Kashev" - the computer center of Bank Leumi. A Jewish Agency Absorption Centre is also located in Lod. According to CBS figures for 2000, 23,032 people were salaried workers and 1,405 were self-employed. The mean monthly wage for a salaried worker was NIS 4,754, a real change of 2.9% over the course of 2000. Salaried men had a mean monthly wage of NIS 5,821 (a real change of 1.4%) versus NIS 3,547 for women (a real change of 4.6%). The mean income for the self-employed was NIS 4,991. About 1,275 people were receiving unemployment benefits and 7,145 were receiving an income supplement. Art and culture In 2009-2010, Dor Guez held an exhibit, Georgeopolis, at the Petach Tikva art museum that focuses on Lod. Archaeology A well-preserved mosaic floor dating to the Roman period was excavated in 1996 as part of a salvage dig conducted on behalf of the Israel Antiquities Authority and the Municipality of Lod, prior to widening HeHalutz Street. According to Jacob Fisch, executive director of the Friends of the Israel Antiquities Authority, a worker at the construction site noticed the tail of a tiger and halted work. The mosaic was initially covered over with soil at the conclusion of the excavation for lack of funds to conserve and develop the site. The mosaic is now part of the Lod Mosaic Archaeological Center. The floor, with its colorful display of birds, fish, exotic animals and merchant ships, is believed to have been commissioned by a wealthy resident of the city for his private home. The Lod Community Archaeology Program, which operates in ten Lod schools, five Jewish and five Israeli Arab, combines archaeological studies with participation in digs in Lod. Sports The city's major football club, Hapoel Bnei Lod, plays in Liga Leumit (the second division). Its home is at the Lod Municipal Stadium. The club was formed by a merger of Bnei Lod and Rakevet Lod in the 1980s. Two other clubs in the city play in the regional leagues: Hapoel MS Ortodoxim Lod in Liga Bet and Maccabi Lod in Liga Gimel. Hapoel Lod played in the top division during the 1960s and 1980s, and won the State Cup in 1984. The club folded in 2002. A new club, Hapoel Maxim Lod (named after former mayor Maxim Levy) was established soon after, but folded in 2007. Notable people Twin towns-sister cities Lod is twinned with: See also References Bibliography External links |
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Contents Twitch (service) Twitch is an American video live-streaming service popular in video games, including broadcasts of esports competitions. It also offers music broadcasts, creative content, and "in real life" streams. Twitch is operated by Twitch Interactive, a subsidiary of Amazon. It was introduced in June 2011 as a spin-off of the general-interest streaming platform Justin.tv. Content on the site can be viewed either live or via video on demand. The games shown on Twitch's current[update] homepage are listed according to audience preference and include genres such as real-time strategy games, fighting games, racing games, and first-person shooters. The popularity of Twitch eclipsed that of Justin.tv. In October 2013, the website had 45 million unique viewers, and by February 2014, it was considered the fourth-largest source of peak Internet traffic in the United States. At the same time, Justin.tv's parent company was re-branded as Twitch Interactive to represent the shift in focus when Justin.tv was getting shut down in August 2014. The same month, the service was acquired by Amazon for US$970 million, which later led to the introduction of synergies with the company's subscription service Amazon Prime. By 2015, Twitch had more than 100 million viewers per month. In 2017, Twitch remained the leading live-streaming video service for video games in the US, and had an advantage over YouTube Gaming, which shut down its standalone app in May 2019. As of February 2020,[update] it had three million broadcasters monthly and 15 million active users daily, with 1.4 million average concurrent users. As of May 2018,[update] Twitch had over 27,000 partner channels. As of January 2025,[update] Twitch was the 30th-most-visited website in the world with 23.46% of its traffic coming from the United States, followed by Russia with 8.87%, Germany with 7.08% and France with 6.26%. In late 2023, Twitch announced that they would stop operating in South Korea in 2024 because of its network fee policy, citing prohibitive costs. History When Justin.tv was launched in 2007 by Justin Kan and Emmett Shear, two recent Yale graduates, the site was divided into several content categories. The gaming category grew especially fast, and became the most popular content on the site. In June 2011,: 40 the company decided to spin off the gaming content as TwitchTV, inspired by the term twitch gameplay. It launched officially in public beta on June 6, 2011. Since then, Twitch has attracted more than 35 million unique visitors a month. Twitch had about 80 employees in June 2013, which increased to 100 by December 2013. The company was headquartered in San Francisco's Financial District. Twitch has been supported by significant investments of venture capital, with US$15 million in 2012 (on top of US$7 million originally raised for Justin.tv), and US$20 million in 2013. Investors during three rounds of fund raising leading up to the end of 2013 included Draper Associates, Bessemer Venture Partners and Thrive Capital.: 40 In addition to the influx of venture funding, it was believed in 2013 that the company had become profitable.: 40 Especially since the shutdown of its direct competitor Own3d.tv in early 2013, Twitch has become the most popular e-sports streaming service by a large margin, leading some to conclude that the website has a "near monopoly on the market". Competing video services, such as YouTube and Dailymotion, began to increase the prominence of their gaming content to compete, but have had a much smaller impact so far. As of mid-2013, there were over 43 million viewers on Twitch monthly, with the average viewer watching an hour and a half a day. By February 2014, Twitch was the fourth largest source of Internet traffic during peak times in the United States, behind Netflix, Google, and Apple. Twitch made up 1.8% of total US Internet traffic during peak periods. In late 2013, particularly due to increasing viewership, Twitch had issues with lag and low frame rates in Europe. Twitch has subsequently added new servers in the region. Also in order to address these problems, Twitch implemented a new video system shown to be more efficient than the previous system. Initially, the new video system was criticized by users because it caused a significant stream delay, interfering with broadcaster–viewer interaction.[citation needed] Twitch staff said that the increased delay was likely temporary and at the time, was an acceptable trade-off for the decrease in buffering. On February 10, 2014, Twitch's parent company (Justin.tv, Inc.) was renamed Twitch Interactive, reflecting the increased prominence of the service over Justin.tv as the company's main business. That same month, a stream known as Twitch Plays Pokémon, a crowdsourced attempt to play Pokémon Red using a system translating chat commands into game controls, went viral. By February 17, the channel reached over 6.5 million total views and averaged concurrent viewership between 60 and 70,000 viewers with at least 10% participating. Vice President of Marketing Matthew DiPietro praised the stream as "one more example of how video games have become a platform for entertainment and creativity that extends WAY beyond the original intent of the game creator. By merging a video game, live video and a participatory experience, the broadcaster has created an entertainment hybrid custom made for the Twitch community. This is a wonderful proof of concept that we hope to see more of in the future." Beginning with its 2014 edition, Twitch was made the official live-streaming platform of the Electronic Entertainment Expo. On May 18, 2014, Variety first reported that Google had reached a preliminary deal to acquire Twitch through its YouTube subsidiary for approximately US$1 billion. On August 5, 2014, the original Justin.tv site suddenly ceased operations, citing a need to focus resources entirely on Twitch. On August 6, 2014, Twitch introduced an updated archive system, with multi-platform access to highlights from past broadcasts by a channel, higher quality video, increased server backups, and a new Video Manager interface for managing past broadcasts and compiling "highlights" from broadcasts that can also be exported to YouTube. Due to technological limitations and resource requirements, the new system contained several regressions; the option to archive complete broadcasts on an indefinite basis ("save forever") was removed, meaning that they can only be retained for a maximum of 14 days, or 60 for partners and Turbo subscribers. While compiled highlights can be archived indefinitely, they were limited to two hours in length. In addition, Twitch introduced a copyright fingerprinting system that would mute audio in archived clips if it detected a copyrighted song in the stream. On August 25, 2014, Amazon acquired Twitch Interactive for US$970 million in an all-cash deal. Sources reported that the rumoured Google deal had fallen through and allowed Amazon to make the bid, with Forbes reporting that Google had backed out of the deal due to potential antitrust concerns surrounding it and its existing ownership of YouTube. The acquisition closed on September 25, 2014. Take-Two Interactive, which owned a 2% stake at the time of the acquisition, made a windfall of $22 million. Under Amazon, Shear continued as chief executive officer of Twitch Interactive, with Sara Clemens added to the executive team as chief operating officer in January 2018. Shear touted the Amazon Web Services platform as an "attractive" aspect of the deal, and that Amazon had "built relationships with the big players in media", which could be used to the service's advantage—particularly in the realm of content licensing. The purchase of Twitch marked the third recent video gaming–oriented acquisition by Amazon, which had previously acquired the developers Reflexive Entertainment and Double Helix Games. On December 9, 2014, Twitch announced it had acquired GoodGame Agency, an organisation that owns the esports teams Evil Geniuses and Alliance. In March 2015, Twitch reset all user passwords and disabled all connections to external Twitter and YouTube accounts after the service reported that someone had gained "unauthorised access" to the user information of some Twitch users. In June 2016, Twitch added a new feature known as "Cheering", a special form of emoticon purchased as a microtransaction using an in-site currency known as "Bits". Bits are bought using Amazon Payments, and cheers act as donations to the channel. Users also earn badges within a channel based on how much they have cheered. On August 1, 2016, it was reported that Twitch had signed a lease for 185,000 square feet (17,187 m2) in a new office tower to be constructed at 350 Bush Street in San Francisco. On August 16, 2016, Twitch acquired Curse LLC, an operator of online video gaming communities and gaming-oriented VoIP software. In December 2016, GoodGame Agency was divested by Amazon to their respective members due to conflict of interest concerns. On September 30, 2016, Twitch announced Twitch Prime, a service which provides premium features that are exclusive to users who have an active Amazon Prime subscription. This included advertising-free streaming, monthly offers of free add-on content ("Game Loot"), and game discounts. Games included with the game loot rewards were Apex Legends, Legends of Runeterra, FIFA Ultimate Team, Teamfight Tactics, Mobile Legends: Bang Bang, Doom Eternal, and more. In December 2016, Twitch announced a semi-automated chat moderation tool (AutoMod), which uses natural language processing and machine learning to set aside potentially unwanted content for human review. In February 2017, Twitch announced the Twitch Game Store, a digital distribution platform that would expose digital purchases of games within the site's browsing interface. When streaming games available on the store, partnered channels could display a referral link to purchase the game—receiving a 5% commission. Users also received a "Twitch Crate" on every purchase, which included Bits and a collection of random chat emotes. In August 2017, Twitch announced it had acquired video indexing platform ClipMine. On August 20, 2018, Twitch announced that it will no longer offer advertising-free access to the entire service to Amazon Prime subscribers, with this privilege requiring the separate "Twitch Turbo" subscription or an individual channel subscription. This privilege ended for new customers effective September 14, 2018, and for existing customers October 2018. In October 2018, Twitch announced Amazon Blacksmith, a new extension allowing broadcasters to configure displays of products associated with their streams with Amazon affiliate links. On November 27, 2018, Twitch discontinued the Game Store service, citing that it did not generate as much additional revenue for partners as they hoped, and new revenue opportunities such as Amazon Blacksmith. Users retain access to their purchased games. On December 12, 2018, Fandom, Inc. had reached an agreement to acquire Curse Media, a spin-off of Curse, from Twitch Interactive for an undisclosed amount. Curse was dissolved and its assets were moved under Twitch Interactive. Twitch's new headquarters at 350 Bush Street opened in August 2019. To comply with historic preservation requirements, the developer kept the front facade of the San Francisco Curb Exchange, but tore down everything behind the facade, and built a reconstruction of the old trading hall through which visitors must walk to reach the modern high-rise office tower behind it. Twitch acquired the Internet Games Database (IGDb), a user-driven website similar in functionality to Internet Movie Database (IMDb) to catalog details of video games in September 2019. Twitch plans to use the database service to improve its own internal search features and help users find games they are interested in. On September 26, 2019, Twitch unveiled a new logo and updated site design. The design is accompanied by a new advertising campaign, "You're already one of us", which will seek to promote the platform's community members. Twitch began signing exclusivity deals with high-profile streamers in December 2019. Twitch introduced a Safety Advisory Council in May 2020, made up from streamers, academics, and think tanks, with a goal to develop guidelines for moderation, work-life balance, and safeguarding the interests of marginalized communities for the platform. The announcement attracted controversy, and CEO Emmett Shear later clarified that the role of the council was purely advisory. On June 22, 2020, Twitch Interactive sold CurseForge to Overwolf for an undisclosed sum. In August 2020, Twitch Prime was renamed Prime Gaming, aligning it closer with the Amazon Prime family of services. In 2020, Twitch sold Union For Gamers to Magic Find. In May 2021, Twitch announced that it would introduce over 350 new tags to categorize streams, including finer tags for gender identity, sexual identity, and disabilities, as well as tags for other types of themes (such as virtual streamers). The disability and LGBT-oriented tags were developed in consultation with the video game accessibility charities AbleGamers and SpecialEffect, and the LGBT organizations GLAAD and The Trevor Project. On October 6, 2021, an anonymous hacker reportedly leaked "the entirety" of Twitch, including its source code of the Twitch client and APIs, and details of the payouts made to almost 2.4 million streamers since August 2019. The user posted a 128GB torrent link to 4chan and said that the leak, which includes source code from almost 6,000 internal Git repositories, is also "part one" of a larger release. The leak also included details of plans for a digital storefront under the codename of "Vapor" meant to be a competitor to Steam along with details on payment received by streamers for their work on Twitch. Twitch verified they had suffered a data leak which they attributed to a server misconfiguration used by a "malicious third party". While Twitch found no indication of login credentials or credit card information to have been taken in the breach, the company reset all stream keys as a precaution. On August 23, 2022, Twitch announced that it would no longer enforce its exclusivity agreement, allowing Twitch streamers to livestream on other streaming platforms. The announcement noted that simulcasting on Twitch and other "Twitch-like" streaming platforms was still prohibited; however, an exemption to the simulcasting restriction was applied to short-form streaming platforms such as Instagram and TikTok. Despite the specific mention of restrictions on simulcasting, former Twitch employees noted that Twitch would likely not enforce the restriction, as doing so would be very difficult, and they had not been enforcing it for several months prior to the announcement. After the announcement, many high-profile streamers who were limited by exclusivity, such as Ninja and Pokimane, started streaming on other platforms. On September 21, 2022, Twitch announced it would be reducing the subscription revenue earned by large streamers. Though most streamers get a 50% of revenue from subscriptions, some larger streamers have premium subscription terms, which give them 70% of subscription revenue. The new change, set to take effect on June 1, 2023, would mean premium streamers would keep 70% of the first $100,000 earned from subscriptions, after which their cut would be lowered to 50%. The announcement came after Twitch declined a popular request for all streamers to have 70% subscription revenue, which many noted is the same revenue already offered by YouTube. Twitch President Dan Clancy justified the change in a statement issued on Twitch's blog, stating it was done to cover Twitch's operating costs, noting the premium 70% split stopped being offered to new streamers over a year prior, and pointing to alternate streamer revenue sources that would not be affected by the subscription revenue reductions, such as Prime Subs or advertisement breaks. Though Clancy claimed 90% of streamers would not be affected by the revenue reduction, the change drew criticism from many streamers, who viewed it as harmful to the security of streaming careers and more beneficial to Twitch and its advertisers than their users, with several streamers expressing doubt at Clancy's claims of Twitch's high operating costs, and noting that Twitch already has alternative revenue sources that make reducing streamer revenue unnecessary. The announcement led to some streamers considering leaving Twitch or organizing boycotts. In December 2022, Amazon Senior Vice President Jeff Blackburn retired and was replaced by Steve Boom as Vice President of Audio, Twitch, and Games. Twitch CEO Dan Clancy reports directly to Boom. In March 2023, Clancy became CEO of Twitch, after previous CEO and Justin.tv co-founder Emmett Shear announced he would step down after 16 years at the company. Both Shear and Clancy have been described as "more product-focused than creator-focused". On March 20, Clancy announced that Twitch would be laying off 400 employees, as part of Amazon-wide layoffs affecting 9,000 workers across the company. On June 6, 2023, Twitch announced restrictions on third-party sponsor placements in streams, including restricting the size of sponsor logos, and prohibiting "burned-in" audio, video, or display advertising. The changes were met with criticism from major streamers such as Asmongold (who threatened to leave the service), Cr1TiKaL, and Zentreya due to their broad wording, concerns that it would impact streamers' existing relationships with advertisers, and their impact on charity and esports events that rely extensively on sponsorship. The service quickly retracted the new branded content policy and announced that it would be clarified, stating that it was intended to "clarify our existing ads policy that was intended to prohibit third party ad networks from selling burned in video and display ads on Twitch, which is consistent with other services", and that Twitch "[does] not intend to limit streamers' ability to enter into direct relationships with sponsors." In August 2023, Twitch began to trial a "Discovery Feed" feature in its mobile apps, populated by "featured" clips from followed users. In October 2023, Twitch began to implement stories. At TwitchCon 2023, Twitch announced upcoming updates to its Guest Star feature (concurrently renamed "Stream Together") to allow for merged chat rooms, and that streamers under an affiliation or partnership agreement with the service (unless contractually required) would be allowed to simulcast their streams on competing platforms such as YouTube, as opposed to only mobile-centric video platforms. On December 6, 2023, Twitch announced that it would exit the South Korea market effective February 27, 2024, citing the prohibitive costs of offering the service in the country. Due to demands from internet service providers that Twitch pay network access fees, Twitch restricted streams to 720p quality in September 2022, and blocked access to video-on-demand (VOD) content (including archived broadcasts and clips) in February 2023. Users in South Korea will no longer be allowed to monetize their streams, and will be offboarded from the affiliate and partnership programs. In February 2024, Twitch was additionally fined ₩435 million ($327,067) by the Korea Telecommunications Commission, deeming Twitch's degradation of service in the country to be unjustified and undermining the interests of users. In January 2024, Twitch announced another mass layoff, affecting 500 employees or 35% of total staff, after previous layoffs in early 2023. The announcement came amid ongoing struggles and ensuing layoffs across the tech and digital media sectors. In October 2024, Twitch's longtime head of music Cindy Charles died. Content Twitch is designed to be a platform for content, including esports tournaments, personal streams of individual players, and gaming-related talk shows. A number of channels do live speedrunning. The Twitch homepage currently displays games based on viewership. As of June 2018,[update] some of the most popular games streamed on Twitch are Fortnite, Grand Theft Auto V, League of Legends, Dota 2, PlayerUnknown's Battlegrounds, Hearthstone, Overwatch and Counter-Strike: Global Offensive with a combined total of over 356 million hours watched.[citation needed] Twitch has also made expansions into non-gaming content; such as in July 2013, the site streamed a performance of 'Fester's Feast' from San Diego Comic-Con, and on July 30, 2014, electronic dance music act Steve Aoki broadcast a live performance from a nightclub in Ibiza. In January 2015, Twitch introduced an official category for music streams, such as radio shows and music production activities, and in March 2015, announced that it would become the new official live-streaming partner of the Ultra Music Festival, an electronic music festival in Miami. On October 28, 2015, Twitch launched a second non-gaming category, "Creative", which is intended for streams showcasing the creation of artistic and creative works. To promote the launch, the service also streamed an eight-day marathon of Bob Ross' The Joy of Painting. In July 2016, Twitch launched "Social eating" as a beta; it was inspired by the Korean phenomenon of mukbang and Korean players having engaged in the practice as intermissions on their gaming streams. In March 2017, Twitch added an "IRL" category, which is designed for content within Twitch guidelines that does not fall within any of the other established categories on the site (such as lifelogs). GeekWire reported that "while gameplay still makes up the vast majority of the content broadcast via Twitch, the 'Just Chatting' category—a catch-all term that encompasses anything from candid conversation to reality programming—took the top spot by a comfortable margin overall in December . While the category has been on the rise for the last couple of months, this was the first time that it's actually achieved No. 1 overall for a tracked period on the platform". In 2020, Thrillist described Twitch as "talk radio for the extremely online". Michael Espinosa, for Business Insider in 2021, highlighted that "Twitch dominates the live content space, with 17 billion hours watched last year (per StreamElements), compared to YouTube Gaming Live's 10 billion (per the company). But the vast majority of gaming content is still consumed on-demand, where YouTube is the clear leader with over 100 billion hours watched last year". Twitch is often used for video game tutorials; the nature of Twitch allows mass numbers of learners to interact with each other and the instructor in real time. Twitch is also used for software development learning, with communities of users streaming programming projects and talking through their work. Broadcasters on Twitch often host streams promoting and raising money towards charity. By 2013, the website has hosted events which, in total, raised over US$8 million in donations for charitable causes, such as Extra Life 2013. As of 2017,[update] Twitch has raised over US$75 million in donations for charitable causes. The biggest charity event of Twitch is ZEvent, a French project created by Adrien Nougaret and Alexandre Dachary, with more than US$10 million raised for Action Contre la Faim in October 2021. ESL tournaments have aired on Justin.tv and later Twitch.tv since 2009. The platform has also been a longtime broadcaster of the Evolution Championship Series. Twitch has been the official broadcaster of the League of Legends World Championship since 2012, as well as other League of Legends tournaments organized by Riot Games. Dota 2's premier tournament The International has been livestreamed on Twitch since 2013. The platform airs Rocket League tournaments organized by Psyonix since 2016. The ELeague also broadcasts events on Twitch since 2016. Twitch and Blizzard Entertainment signed a two-year deal in June 2017 to make Twitch be the exclusive streaming broadcaster of select Blizzard esports championship events, with viewers under Twitch Prime earning special rewards in various Blizzard games. Twitch also reached a deal in 2018 to be the streaming partner of the Overwatch League, with the site also offering an "All-Access Pass" with exclusive content, emotes, and in-game items for Overwatch. Blizzard switched to rival platform YouTube in 2020. Fortnite Battle Royale competitions have aired on Twitch since its launch in 2017, including the E3 2018 Fortnite Pro-Am and the 2019 Fortnite World Cup. The NBA 2K League has been livestreamed on Twitch since its inception in 2018. As the COVID-19 pandemic suspended motorsports competitions around the world, several series launched sim racing competitions with real-life professional drivers. Some series had official broadcasts on Twitch, such as Formula One and IMSA. Many drivers also had their personal live streams on Twitch, as was the case of several eNASCAR iRacing Pro Invitational Series and INDYCAR iRacing Challenge drivers. In December 2017, the National Basketball Association (NBA) announced that it would stream NBA G League games on Twitch starting on December 15; the broadcasts also include interactive statistics overlays, as well as additional streams of the games with commentary by Twitch personalities. In April 2018, it was announced that Twitch would carry eleven National Football League (NFL) Thursday Night Football games from 2018 to 2021 in simulcast with Fox, as part of the league's renewed streaming deal with Amazon Prime Video. During the 2017 season, these streams had been exclusive to Amazon Prime subscribers. As part of the broadcasts, Twitch would also offer alternate broadcasts, including broadcasts hosted by Twitch personalities, and NFL Next Live—an interactive broadcast hosted by Andrew Hawkins and Cari Champion. With Thursday Night Football moving exclusively to Amazon Prime Video for the 2022 NFL season, Twitch will continue to carry simulcasts of all games, while the site will also carry alternate broadcasts (such as one featuring Dude Perfect). In January 2019, professional wrestling promotion Impact Wrestling announced that it would stream its weekly show Impact! on Twitch, in simulcast with the television airing on the US cable network Pursuit Channel (co-owned with the promotion's parent company Anthem Sports & Entertainment). On September 5, 2019, the Premier Hockey Federation announced a three-year broadcast rights deal with Twitch, covering all games and league events. The deal also contained an agreement with the Premier Hockey Federation Players' Association for revenue sharing with players, and marked the first time that the NWHL had ever received a rights fee. The National Women's Soccer League announced a three-year deal in March 2020 for Twitch to stream 24 matches per season in the United States and Canada, collaborate on original content, and serve as the rightsholder for all matches outside of the United States and Canada. On June 20, 2020, as an extension of Prime Video's local rights to the league, a plan to air all of the remaining matches of the 2019–20 season (for the resumption of play due to the COVID-19 pandemic and matches being played behind closed doors), and a plan for some of these matches to be carried free-to-air, it was announced that Twitch would stream a package of four Premier League soccer matches within the United Kingdom. On July 16, 2020, US radio broadcaster Entercom announced a partnership to stream video simulcasts of programs from some of their major-market sports talk stations on Twitch channels. On July 22, 2020, Twitch officially launched a Sports category, primarily playing host to content streamed by sports leagues and teams on the platform. The 2021 Copa América association football tournament aired in Spain on Twitch, under a partnership with Gerard Piqué's media company Kosmos and streamer Ibai Llanos. Twitch features a large number of emotes. There are emotes free for all users, emotes for Turbo users, emotes for Twitch Prime users, and emotes for users who are subscribed to Twitch partners or affiliates. As of May 2024,[update] the most used emote is "x0pashL" with 8.85 billion uses, and the most used global emote is "TriHard" with 4.39 billion uses. Twitch partnered broadcasters unlock more "emote slots" as they gain more subscribers up to a maximum of 50 emotes per channel. On January 6, 2021, Twitch announced that they had removed the PogChamp emote, the third most-used emote on the platform in 2018, typically used to express excitement, joy or shock. The decision was made in response to comments from the streamer Ryan "Gootecks" Gutierrez, the face of the emote, supporting civil unrest during the 2021 storming of the United States Capitol for the death of a protestor. Twitch said it would work with the community for a suitable replacement for the emoticon. Twitch later announced that there would be a new PogChamp emote every 24 hours. On February 12, Twitch viewers elected KomodoHype as the new permanent PogChamp emote. Creators and audience Streamer Ninja had been among Twitch's top personalities, with over 14 million followers. In August 2019, however, Ninja announced that he would move exclusively to a Microsoft-owned competitor, Mixer. After Ninja left, the top three streamers in October 2019 based on follower count were Tfue (7.01 million followers), Shroud (6.45 million followers) and TSM Myth (5.1 million followers). Twitch began signing exclusivity deals with high-profile streamers in December 2019, starting with DrLupo, TimTheTatman, and Lirik, who had a combined 10.36 million followers at the time. Dr DisRespect signed a multi-year deal in March 2020. In May 2020, Twitch signed popular streamers Summit1g, dakotaz and JoshOG to multi-year exclusive deals. On June 26, 2020, Dr DisRespect was banned from Twitch for unexplained reasons and his channel was removed from the site. Following the discontinuation of Mixer in late-July 2020, both Ninja and Shroud (who had also defected to the service) re-signed exclusively with Twitch. As of August 2022,[update] there have been eight streamers to have reached over 100,000 concurrent subscribers. These streamers are Ninja, Shroud, Ranboo, Ludwig, Casimiro, Ironmouse, Gaules and Ibai. In April 2021, Business Insider reported that "over the past 31 days, Ahgren has streamed non-stop in an attempt to break the record of 269,154 subscribers held by gaming personality Tyler 'Ninja' Blevins. By the end of the month-long stream, Ahgren had over 282,000 subscribers on his channel. [...] At one point during his sleep cycle, his channel had the most concurrent viewers of any on the platform". In analysis of the October 2021 data leak, multiple news outlets reported that the three top-earning Twitch content creators are Critical Role ($9,626,712), xQc ($8,454,427), and Summit1g ($5,847,541). Sisi Jiang, for Kotaku, reported that "excluding streams that are run by multiple people (such as Critical Role), there are no women in the top third of top-earning Twitch content creators"; in total, there are only three women in the top 100 and only one is a woman of color. Jiang highlighted that these streamers are "Valorant streamer Pokimane at 39th place, cosplayer Amouranth at 48th, and music streamer Sintica at 71st" and commented that "in spite of the complaints about the 'hot tub meta,' 'titty streamers,' and how some male streamers perceive that female streamers are stealing views from men, the numbers show that only a small percentage of women are among the ranks of Twitch's highest-earning content creators". In August 2021, DrLupo left Twitch for an exclusivity deal with YouTube; TimTheTatman followed in September 2021, as did Ludwig Ahgren in November 2021. Nathan Grayson, for The Washington Post, commented that when streamers moved to Mixer in 2019, Twitch quickly locked down multiple streamers in exclusivity deals; however, streamers who moved to Mixer saw their audiences undergo "a marked downsizing. [...] It demonstrated that many viewers within Twitch's ecosystem, when deprived of their favorite big streamers, will just find other Twitch streamers to take their place. [...] Now Twitch is bargaining from a place of confidence. That allows it to reevaluate previous deals made when streamers had more leverage". Grayson reported that lower offers from Twitch coupled with Twitch's higher streaming hour requirement ("YouTube's contracts start at 100 hours of streaming time per month while Twitch's start at 200") has made YouTube's exclusivity deals "tantalizing" to some Twitch streamers. Grayson wrote that "Ryan Wyatt, head of YouTube Gaming, said that allowing streamers to have a better work–life balance is a big priority for him"; DrLupo cited work–life balance as part of his decision to leave Twitch. It was reported in the early 2010s that the typical Twitch viewer is male and aged between 18 and 34 years of age, although the site has also made attempts at pursuing other demographics, including women. By 2015, Twitch had more than 100 million viewers per month. In 2017, Twitch remained the leading live-streaming video service for video games in the US. GeekWire reported that "while Twitch's overall share of the streaming market has been steadily diminishing over the course of the year, from 67.1 percent in December 2018 to 61 percent at the end of the 2019, the steady growth of the overall market means that the overall amount of content watched on the service has done nothing but increase". The journal article World of Streaming. Motivation and Gratification on Twitch reported the results of a Twitch user survey in 2017. In ranking user motivations on the use of Twitch, users were motivated (in descending order) to watch Twitch: "to be entertained", "to follow gaming events", and to "have an alternative for television". Motivations classified as "socialization" and "information" ranked lower than motivations classified as "entertainment". As of February 2020,[update] it had 3 million broadcasters monthly and 15 million daily active users, with 1.4 million average concurrent users. Statista, a company specializing in market and consumer data, reported that "as of May 2020, users in their teens and twenties accounted for more than three-quarters of Twitch's active app user accounts in the United States. According to recent data users aged 20 to 29 years, accounted for 40.6 percent of the video streaming app's user base on the Android platform". They also reported that the "distribution of Twitch users in the United States as of 2nd quarter 2021" was 75% male and 25% female. As of 2022, the countries with the most Twitch users were the United States (93 million), Brazil (16.9 million), Germany (16.8 million), France (15.4 million), the United Kingdom (13.4 million), Russia (10.5 million), Spain (10.5 million), Argentina (10 million), Mexico (9.2 million), and Italy (8.3 million users). The United States accounts for roughly 36% of all Twitch users. Twitch allows anyone to watch a live broadcast and does not require viewers to log in. Users also have the option to follow and subscribe (also known as subbing) to streamers. Following is a free option, similar to other platforms such as Instagram and Twitter, where the user will see their followed streamers on the front page of Twitch when signed in and can receive notifications of specific broadcasts. Subscribing is a way for users to financially support streamers in exchange for exclusive benefits determined by the individual streamer. Users who link their Twitch account to their Amazon Prime account gain access to Prime Gaming which includes one complimentary Twitch subscription per month that the user can assign to the streamer of their choice. The aforementioned 2017 academic survey stated that 31.5% of users "spent money on Twitch"; of those users, 22.6% "donated to a streamer", 31.6% subscribed to a streamer and 45.8% "did both". The majority of these users stated the "main motivation is to support a streamer financially". Twitch's Terms of Service does not allow people under 13 years of age to use its services. Additionally, people who are at least 13 years old but below the age of majority in their jurisdiction (18 in most jurisdictions), may only use the services under the supervision or permission of a parent or other legal guardian who agrees to abide to the Terms of Service. In July 2011, Twitch launched its Partner Program, which reached over 11,000 members by August 2015. Similar to the Partner Program of other video sites like YouTube, the Partner Program allows popular content producers to share in the advertisement revenue generated from their streams. Additionally, Twitch users can subscribe to partnered streamers' channels for US$4.99 a month, often granting the user access to unique emoticons, live chat privileges, and other various perks. Twitch retains US$2.49 of every US$4.99 channel subscription, with the remaining US$2.50 going directly to the partnered streamer. Although exceptions were made, Twitch previously required that prospective partners have an "average concurrent viewership of 500+", as well as a consistent streaming schedule of at least three days a week. However, since the launch of the 'Achievements' feature, there is a clearer "Path to Partnership" with trackable goals for concurrent viewership, duration and frequency of streams. In April 2017, Twitch launched its "Affiliate Program" that allows smaller channels to generate revenue as well, also announcing that it would allow channels access to multi-priced subscription tiers. The participants of this program get some but not all of the benefits of the Twitch Partners. Streamers can make profit from cheering with Bits which are purchasable from Twitch directly. Affiliates are also able to access the Twitch Subscriptions feature, with all the same functionality that Partners have access to, with a maximum of five subscriber emotes.[citation needed] In September 2019, the service announced that Affiliates would now receive a share of ad revenue. Additionally, in June 2023, Twitch introduced the Partner Plus Program. This program was designed to recognize Twitch partners who consistently bring a large audience and engagement to the platform. Streamers in this program receive a 70/30 revenue share on subscription revenue. To qualify for the program, creators had to maintain a sub count of at least 350 subscribers for three consecutive months. Once that is complete, qualifying members will be enrolled for the next 12 months. The program was officially launched on October 1, 2023. This enabled partners to earn more as they continue to grow their community. However, a number of streamers were not happy with the program. Streamers argued that it excluded certain creators because of the criteria and that creators would burn themselves out by trying to achieve 350 monthly subscribers. In January 2024, Twitch made some changes to the program. The platform announced that it would be introducing a new tier to its revenue share program that would grant a 60/40 revenue split and has lower requirements. In addition, the program would also become open to affiliates, expanding access to smaller creators. The program is now known as the "Plus Program." When the program was first launched the year prior, Twitch would only pay out the 70/30 revenue split until streamers made $100,000. Along with expanding the Partner Plus Program and adding a new revenue level, Twitch also announced that it would be eliminating the $100,000 cap for the 70/30 revenue share for all streamers. This was part of Twitch's strategy to provide more earning opportunities for streamers. The program uses a points system to determine which revenue split a streamer qualifies for. Each monthly subscription counts towards the points total. However, some subscriptions have higher point values. One tier 1 subscription is one point, one tier 2 subscription is two points, and one tier 3 subscription equals six points. To qualify for the 60/40 revenue split, streamers must maintain 100 Plus Points for three consecutive months. For the 70/30 revenue split, streamers must maintain 300 Plus Points. Advertising on the site has been handled by a number of partners. In 2011, Twitch had an exclusive deal with Future US.[citation needed] On April 17, 2012, Twitch announced a deal to give CBS Interactive the rights to exclusively sell advertising, promotions and sponsorships for the community. On June 5, 2013, Twitch announced the formation of the Twitch Media Group, a new in-house advertisement sales team which has taken over CBS Interactive's role of selling advertisements. For users who do not have ad-free access to a channel or Twitch Turbo, pre-roll advertising, and mid-roll commercial breaks that are manually triggered by the streamer, are displayed on streams. In September 2020, Twitch announced that it would test automated mid-roll advertising on streams, which cannot be controlled by the streamer. Content moderation and restrictions On August 6, 2014, Twitch announced that all on-demand videos on Twitch became subject to acoustic fingerprinting using software provided by content protection company Audible Magic; if copyrighted music (particularly, songs played by users from outside of the game they are playing) is detected, the 30-minute portion of the video which contains the music will be muted. Live broadcasts were not subject to these filters. A system was available for those who believed they were inappropriately affected and had rights to the music they used to challenge the filtering. Twitch offered a selection of royalty-free music for streamers to use, which was expanded upon later in January 2015. The audio filtering system, along with the lack of communication surrounding the changes in general, proved to be controversial among users. In a Reddit AMA, co-founder Emmett Shear admitted that his staff had "screwed up" and should have provided advance warning of the changes, and promised that Twitch had "absolutely no intention" of implementing audio filtering on live broadcasts. In June 2020, Twitch received a large wave of DMCA takedown notices aimed at year-old VODs and "clips" (short segments of streams that can be captured by users) that contain copyrighted music from 2017 to 2019. Twitch complied with the takedowns and also issued a number of copyright strikes against viewers. Concerned streamers were notified that they should remove all VODs and clips if not certain they did not contain copyrighted material. This provoked major backlash, both at the loss of prior content but also based on viability concerns due to an inability to review or even rapidly delete content. There were also complaints based that strikes were being issued on viewer-created clips, even where the streamer-created content was deleted. On September 15, 2020, Twitch signed a licensing agreement with the French performance society SACEM, allowing composers and publishers to collect royalties whenever their music is streamed in France. Twitch already had licensing deals with the American societies ASCAP, BMI, SESAC and Global Music Rights. To address these issues and also build upon the growth of music-based content on Twitch, Twitch introduced an extension known as "Soundtrack" in September 2020, which plays rights-cleared music with curated genre-based playlists. It is contained within a separate audio track that is not recorded with VODs, and had agreements with 24 music distributors and independent record labels at launch. A group of US performance rights and music associations accused Twitch of designing Soundtrack in such a way as to avoid payment of mechanical and synchronization licenses—claims which Twitch has defended. In September 2021, Twitch and the National Music Publishers' Association signed a creative partnership. In September 2024, Twitch introduced a new program for DJs on the platform, allowing them access to a new stream category for DJ mixes where music from participating labels may be streamed without the risk of a DMCA takedown, with a share of revenue being used to pay royalties (for affiliates and partners, this is deducted from the channel's existing split). This program has limitations: features such as VODs and clips are disabled on any channel enrolled in the DJ program, even if streaming non-DJ content (with Twitch officially recommending the use of a separate account for non-DJ streams), and DJs are restricted to playing music from certain labels and publishers that have reached agreements with the service (potentially restricting the ability to play unofficial remixes). Twitch users are not allowed to stream any game that is rated "Adults Only" (AO) in the United States by the Entertainment Software Rating Board (ESRB), regardless of its rating in any other geographical region, and any game that contains "overtly sexual content" or "gratuitous violence", or content which violates the terms of use of third-party services. Twitch has also explicitly banned specific games from streaming, regardless of rating; this includes games such as BMX XXX, eroge visual novel games (such as Dramatical Murder), HuniePop, Rinse and Repeat, Second Life, and Yandere Simulator. The banning of Yandere Simulator was criticized by YandereDev, the developer of the game. He believed that the game was being arbitrarily singled out with no explanation, as Twitch has not banned other games with sexual or violent content such as Mortal Kombat X, Grand Theft Auto, or The Witcher 3. Twitch took temporary action in May 2019 after channels related to the video game Artifact began to be used for inappropriate content. Artifact, a major game by Valve, had lost most of its audience in just months from its release, and by late May 2019, several popular livestreamers commented that the total viewership for Artifact streams had dropped to near zero. In the days that followed, several streamers started to make streams purporting to be Artifact gameplay but was trolling or other off-topic content. Initially these new streams were playing with the viewers or were jokes, such as showing animal videos or League of Legends matches. After a few days, other Artifact channel streams appeared containing content that was against the terms of Twitch's use policy, including full copyrighted movies, pornography, Nazi propaganda, and at least one stream that showed the entirety of the shooter's video from the Christchurch mosque shootings. The titles of such streams were usually presented to imply they were showing other content while waiting in queue for Artifact matches as to appear legitimate. As word of these streams in the Artifact section grew, Twitch took action, deleting the account that streamed the Christchurch shooting. Twitch then took steps to temporarily ban new accounts from streaming until they can resolve the issue. By June 2019, Twitch started taking legal actions against one hundred "John Doe" streamers in a California court, accusing them of trademark infringement, breach of contract, fraud, and unlawful use of the service that was harming and scaring away users of the service. In early 2021, some streams began to use their Twitch channel to broadcast themselves from hot tubs while wearing swimsuits. Twitch considered these streams to be "not advertiser friendly", banning some of the more predominant channels that had taken this route. In May 2021, Twitch clarified in a "Pools, Hot Tubs, and Beaches" post that it was not trying to discriminate against women or others through this action, but through content that they deemed to be "sexually suggestive". In June that year, Twitch also took similar action against users that performed yoga while at the same time made autonomous sensory meridian response (ASMR) sounds via their microphones, which Twitch also stated was approaching sexual content. In December 2023, the platform introduced a new policy that relaxed prohibitions on certain adult content, given that said content would be appropriately labeled. This came amidst the popularity of supposedly "topless" videos on the platform. Popularized by streamer Morgpie, the genre saw creators push the previous boundaries of Twitch's guidelines by implying but not explicitly showing nudity. Twitch's new policy also allowed depictions of "fictionalized nudity". However, Twitch rescinded its policy very shortly after, following backlash from users and streamers. Twitch CEO Dan Clancy acknowledged that the new policy was a step too far, and that distinguishing between digital art and photography was challenging. As a result, Twitch will no longer permit depictions of real or fictional nudity, regardless of the medium. The company also removed content that violated the updated policy and issued channel enforcements. While some changes to Twitch's Sexual Content Policy remain in effect, such as allowing content that highlights certain body parts and specific dances without a label, games featuring nudity or sexual violence as a core focus are still prohibited. In February 2018, Twitch updated its acceptable content policies to direct that any content that it deemed hateful be suspended from its platform. In June 2020, a number of women stepped forward with accusations towards several streamers on Twitch and other services related to sexual misconduct and harassment claims. Twitch stated it would review all reported incidents and comply with law enforcement in any investigative efforts. However, several popular streamers on Twitch's service believed that the platform could do more to evaluate the accused individuals, prevent incidents, and protect others in the future, and used June 24, 2020, as a Twitch blackout day, not streaming any content through Twitch to show their support. By the evening of June 24, 2020, Twitch had placed several bans on the accounts of those accused after completing their investigation, and stated in a blog post they would be forwarding additional details to law enforcement. Twitch temporarily suspended an account belonging to then US President Donald Trump's campaign on June 29, 2020. Twitch stated that "hateful conduct is not allowed" as the reason for the suspension. Twitch announced a new policy towards harassment and hateful content in December 2020 that would take effect on January 22, 2021, aimed to better protect marginalized users of the service. While the new policy is more strict, Twitch said that this also includes a larger sliding scale of remedies or punishments to better deal with edge cases, such as temporarily blocking one's channel for a short time rather than a full ban. The new rules include a ban on imagery containing the Confederate Flag, and 'racist emotes', though the list of such emotes has not been clarified yet. The new policy included banning words that were considered sexual insults, such as "incel" and "virgin" when used for harassment. The banned words included "simp", which raised criticism by streamers and long-time viewers. While its slang origins have defined "simp" derogatorily as "a man who invests a lot of time and energy into women who don't want him", the term had become common on Twitch as an insult related to men being nice to women on the service or simply to refer to a person with loyalty to another. Twitch, in response, clarified that penalties for using these terms would only be enforced if they were being used in harassment of other users. On December 4, 2020, Twitch removed the "blind playthrough" tag due to concerns of ableism that it may be offensive to those who are visually impaired. Suggestions for non-offensive and more neutral labels include "first playthrough", "undiscovered," and "no spoilers." A popular feature of Twitch is the ability to "raid" another channel, where multiple users, coordinated from a different Twitch channel or another social media service, all join a target channel to provide support and encouragement. This is typically used to help boost the popularity of the target channel, particularly if the raid is organized by a popular streamer. Twitch had officially supported this type of activity since 2017 with the ability for a streamer to send all of their viewers to another channel as a raid. However, around mid-2021, new types of "hate raids" began to occur with increasing frequency on Twitch. In these cases, numerous users would flood a channel and its chat with messages of harassment and hate towards the streamer as a form of cyberbullying. Most of these users are typically from automated bots, which made it difficult for channel moderators to deal with the amount of messages. Despite warning Twitch about these hate raids, Twitch had shown little action towards stopping them, leading numerous streams to organize a "#ADayOffTwitch" on September 1, 2021, as a form of protest in anticipation that Twitch will find ways to take action against them. After acknowledging a problem with dealing with hate raids, Twitch launched a lawsuit in early September 2021 against two individuals they had determined to be responsible for managing several hate raids after permanently banning their accounts. At the end of September 2021, Twitch introduced tools for streamers to be able to limit who may participate in their chat as to prevent hate raids. These tools allow streamers to limit chat to those that have verified their phone number or email with Twitch, as well as to those that have followed their channel for a minimum amount of time. In May 2022, following the mass shooting in Buffalo, the New York state attorney general's office announced an investigation into multiple online platforms, including Twitch, to determine their part in platforming or promoting hateful content. The investigation will also focus on the platforms' moderation efforts. A spokesperson for Twitch stated that the service would comply with the investigation. In November 2024, Twitch banned the use of "Zionist" as a slur. Twitch specified that the rule was conditional, saying, "You're allowed to discuss the political movement of that name, but not attack or demean another individual or group of people on the basis of their background or religious belief." The Anti-Defamation League, non-governmental organization that was founded to combat antisemitism, took credit for the change. The move was condemned by pro-Palestinian activists, such as Omar Zahzah, in the Palestine Chronicle, said it would ultimately lead to the ban of Palestine from the platform.[failed verification] In April 2021, it was reported that Twitch was providing a financial lifeline to extremists such as QAnon adherents and far-right influencers. Another report in August and September 2021, by the Institute of Strategic Dialogue also identified Twitch as a platform where far right extremists run rampant. Clips from far-right extremists, such as 'Omegle Redpilling' become quite popular before they are removed from the platform and in some cases, are not removed at all according to ISD. In 2024, it was reported that new Twitch account sign‑ups from Israeli IP addresses had been blocked for an extended period. In public posts that month, Twitch claimed it had temporarily disabled email‑verified sign‑ups in Israel after the October 7, 2023 attacks to prevent graphic content, and further stated the block was inadvertently left in place, calling this an "unacceptable miss." Twitch also asserted phone verification remained available, a point disputed by many users. The restriction was lifted in October 2024. On September 20, 2022, Twitch announced that beginning October 18, it would prohibit the streaming of slots, roulette and dice games on gambling websites not licensed in the US or "other jurisdictions that provide sufficient consumer protection". The policy change does not affect sports betting, fantasy sports, and poker. Gambling has been extremely popular on Twitch for years, being one of the most popular types of content on the platform, with many streamers being sponsored by online gambling services; however, it has also been controversial, with prominent streamers such as Mizkif and Pokimane speaking out against the negative effects of gambling streams. The announcement came shortly after a popular streamer admitted he spent $200,000 in donations on CS:GO skin gambling. Internet censorship As of September 20, 2018,[update] the Twitch website is blocked and the app is blocked from the Apple App Store in China. In India, Twitch was reportedly blocked by Reliance-owned telecommunication company Jio as well as internet service providers JioFiber and Hathway in September 2020 as some users were illegally streaming Indian Premier League cricket matches on the platform. Later it was unblocked.[citation needed] Slovakia's government reportedly blocked Twitch in June 2021 after a streamer in the country with around 35,000 followers was found streaming poker, which was in violation of local gambling laws. On July 4, 2022, the Iranian government blocked access to Twitch for Iranian Internet users. On February 23, 2024, Twitch was blocked in Turkey per a complaint by the country's lotteries commission. Service was restored in the country six days later on February 29.[citation needed] Platform support Twitch CEO Emmett Shear has stated a desire to support a wide variety of platforms, stating that they wanted to be on "every platform where people watch video". Users can watch Twitch streams via Twitch's website in a web browser and via dedicated streaming apps for mobile devices, digital media players and video game consoles. This includes: Users can broadcast to Twitch from the following platforms: After acquiring Curse LLC, Twitch Interactive rebranded the Curse app as the Twitch Desktop App in March 2017. It kept features for mod installation and management for supported games via CurseForge; kept Curse Voice features such as screen sharing, text chat, voice chat, video chat and community server creation; added a dedicated browser for the Twitch website; added Twitch's friends system; and added activity sharing. This update also redesigned the application. The software also served as the client for the former Twitch Game Store. The Curse mobile app was subsequently rebranded as Twitch Messenger[citation needed] which was later shut down.[citation needed] Twitch removed the app's servers, group messaging, voice chat and video chat functionality in February 2019. On June 22, 2020, Twitch Interactive sold CurseForge to Overwolf for an undisclosed sum. On December 2, 2020, mod management functionality was removed from the Twitch Desktop App.[citation needed] The mod management functionality previously found in the Twitch app can since be found in Overwolf's CurseForge app. On March 30, 2022, Twitch announced that it would officially end support for the Twitch Desktop App on April 30, 2022, opting users of the desktop app to use a web browser to interact with Twitch on desktop platforms. The Creator Dashboard on Twitch is a tool that helps streamers manage and optimize their channels. In 2019, the platform announced a new set of features to make streaming more accessible and interactive. This new Creator Dashboard introduced features such as Stream Manager, Quick Actions, Creator Updates, and Assistant. These features were introduced so that creators could set subscriber goals, analyze engagement trends, and simplify streaming tasks. The Stream Manager allows streamers to view various aspects of their livestream such as their live chat, recent followers and subscribers, and a playback of the stream to see what the viewers are seeing. The Quick Actions panel on the Creator Dashboard allows streamers to perform actions such as running ads, enabling followers-only or emote-only chat, and creating clips. The Creator Updates section is a dedicated space for streamers to learn about important product updates and feature changes. The Assistant section provides creators with resources to help them grow their channel and become an affiliate or partner. TwitchCon TwitchCon is a biannual fan convention devoted to Twitch and the culture of video game streaming. The inaugural event was held at the Moscone Center in San Francisco from September 25 to 26, 2015. Since its inception TwitchCon has been an annual event. The second TwitchCon was held in San Diego at the San Diego Convention Center from September 30 to October 2, 2016. The third annual TwitchCon was held in Long Beach at the Long Beach Convention and Entertainment Center from October 20 to 22, 2017. The fourth annual TwitchCon was held at the San Jose McEnery Convention Center in San Jose, California, from October 26 to 28, 2018. In 2019, Twitchcon expanded overseas and hosted their first ever European event in Berlin in April 2019, alongside a North American event later in November 2019 in San Diego. TwitchCon had planned to host an event in Amsterdam in May 2020, but this was cancelled due to the COVID-19 pandemic. Another TwitchCon event was planned in San Diego in September 2020, but was also cancelled due to COVID-19. See also References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Uber_(company)] | [TOKENS: 4395] |
Contents Uber Page version status This is an accepted version of this page Uber Technologies, Inc. is an American multinational transportation company that provides ride-hailing services, courier services, food delivery, and freight transport. It is headquartered in San Francisco, California, and operates in approximately 70 countries and 15,000 cities worldwide. It is the largest ridesharing company worldwide with over 180 million monthly active users and 6 million active drivers and couriers. It coordinates an average of 36 million trips and delivery orders per day, and has coordinated 64 billion trips and delivery orders since its inception in 2010. In the second quarter of 2025, the company had a take rate (revenue as a percentage of gross bookings) of 30.6% for mobility services and 18.8% for food delivery. The company is also in the process of developing robotaxi services in partnership with Lucid Motors, Nuro, and Baidu. History In 2009, Garrett Camp, a co-founder of StumbleUpon, came up with the idea to create Uber to make it easier and cheaper to procure direct transportation. Camp and Travis Kalanick had spent $800 hiring a private driver on New Year's Eve, which they deemed excessive, and Camp was also inspired by his difficulty in finding a taxi on a snowy night in Paris. The prototype of the mobile app was built by Camp and his friends, Oscar Salazar and Conrad Whelan, with Kalanick as the "mega advisor" to the company. In February 2010, Ryan Graves became the first Uber employee; he was named chief executive officer (CEO) in May 2010. In December 2010, Kalanick succeeded Graves as CEO and Graves became the chief operating officer. Following a beta launch in May 2010, Uber's services and mobile app launched publicly in San Francisco in 2011. Originally, the application only allowed users to hail a black luxury car and the price was approximately 1.5 times that of a taxi. In 2011, the company changed its name from UberCab to Uber after complaints from San Francisco taxicab operators. Kalanick believed that in addition to efficiency, Uber offered elegance because all drivers had fancy black cars. He did not feel that regular cars driven by non-professional drivers would be attractive. Kalanick and his angel investor Jason Calacanis publicly stated in podcasts that the world's first rideshare company (Wingz) was illegal and would not work. The company's early hires included a nuclear physicist, a computational neuroscientist, and a machinery expert who worked on predicting arrival times for Uber's cars more accurately than Google APIs. In April 2012, Uber launched a service in Chicago, whereby users were able to request a regular taxi or an Uber driver via its mobile app. In July 2012, Uber introduced UberX, a cheaper option that allowed drivers to use non-luxury vehicles, but still subject to having commercial licenses. On April 1, 2013, after Wingz obtained the first legal rideshare license in the world, followed by Lyft and Sidecar, Uber announced in a white paper penned by Travis Kalanick that Uber was going to copy this model and add regular drivers with personal vehicles to the UberX platform instead of only commercially-licensed vehicles, subject to a background check, insurance, registration, and vehicle standards. By December 2013, the service operated in 65 cities. In December 2013, USA Today named Uber its tech company of the year. In August 2014, Uber launched a shared transport service in the San Francisco Bay Area and launched Uber Eats, a food delivery service. While it was expanding, Uber generally commenced operations in a city without regard for local regulations. If faced with regulatory opposition, Uber called for public support for its service and mounted a political campaign, supported by lobbying, to change regulations. Uber argued that it is "a technology company" and not a taxi company, and therefore it was not subject to regulations affecting taxi companies. Uber's strategy was generally to "seek forgiveness rather than permission". In 2014, with regards to airport pickups without a permit in California, drivers were actually told to ignore local regulations and that the company would pay for any citations. In August 2016, facing tough competition, Uber sold its operations in China to DiDi in exchange for an 18% stake in DiDi. DiDi agreed to invest $1 billion in Uber. Uber had started operations in China in 2014, under the name 优步 (Yōubù). In 2016, Uber acquired Ottomotto, a self-driving truck company founded by Anthony Levandowski, for $625 million. Levandowski, previously employed by Waymo, allegedly founded Ottomotto using trade secrets he stole from Waymo. Uber settled a lawsuit regarding the use of such intellectual property and reached a deal to use Waymo's technology for its freight transport operations. In December 2016, Uber acquired Geometric Intelligence and its 15-person staff, which became "Uber AI", a division for researching artificial intelligence and machine learning. Uber AI was shut down in May 2020. In August 2017, Dara Khosrowshahi, the former CEO of Expedia Group, replaced Kalanick as CEO. Earlier in March 2015, as CEO of Expedia Group, Khosrowshahi had led a multimillion equity investment in Wingz, Inc., the first ridesharing company in the world. In July 2017, Uber received a five-star privacy rating from the Electronic Frontier Foundation, but was harshly criticized by the group in September 2017 for a controversial policy of tracking customers' locations even after a ride ended, forcing the company to reverse its policy. In February 2018, Uber combined its operations in Russia, Armenia, Azerbaijan, Belarus, Georgia and Kazakhstan with those of Yandex Taxi and invested $225 million in the venture. In March 2018, Uber merged its services in Southeast Asia with those of Grab in exchange for a 27.5% ownership stake in Grab. Between May 2018 and November 2018, Uber offered Uber Rent powered by Getaround, a peer-to-peer carsharing service available to some users in San Francisco. In November 2018, Uber became a gold member of the Linux Foundation. In 2018, Uber formed a partnership with Autzu, a San Francisco-based ridesharing company. This collaboration provides Uber drivers with the opportunity to rent electric Tesla on an hourly basis. On May 10, 2019, Uber became a public company via an initial public offering. In March and May 2019, the 2019 Lyft and Uber drivers' strikes led by Rideshare Drivers United were in protest of low wages, long hours, working conditions, and lack of benefits. In the summer of 2019, Uber announced layoffs of 8% of its staff and eliminated the position of COO Barney Harford. In October 2019, Uber acquired 53% of Cornershop, a provider of grocery delivery services primarily in Latin America. In June 2021, it acquired the remaining 47% interest in Cornershop for 29 million shares of Uber. After California Assembly Bill 5 (2019) was introduced, Uber announced that it would not comply with the law, then engaged lobbyists and mounted a public opinion campaign to overturn it via a ballot. Between October 2019 and May 2020, Uber offered Uber Works, a mobile app connecting workers who wanted temporary jobs with businesses in Chicago and Miami. In January 2020, Uber acquired Careem for $3.1 billion and sold its Indian Uber Eats operations to Zomato. Also in January 2020, Uber tested a feature that enabled drivers at the Santa Barbara, Sacramento, and Palm Springs airports to set fares based on a multiple of Uber's rates. In May 2020, during the COVID-19 pandemic, Uber announced layoffs of over 14% of its workforce. In June 2020, in its first software as a service partnership, Uber announced that it would manage the on-demand high-occupancy vehicle fleet for Marin Transit, a public bus agency in Marin County, California. In September 2020, Uber committed to carbon neutrality globally by 2040, and required that, by 2030, in most countries, rides must be offered exclusively in electric vehicles. In December 2020, Uber acquired Postmates for $2.65 billion. Also in December 2020, Uber sold its Elevate division, which was developing short flights using VTOL aircraft, to Joby Aviation. In January 2021, Uber Advanced Technologies Group (ATG), a joint venture minority-owned by SoftBank Vision Fund, Toyota, and Denso that was developing self-driving cars, was sold to Aurora Innovation for $4 billion in equity and Uber invested $400 million into Aurora. In March 2021, the company moved to a new headquarters on Third Street in Mission Bay, San Francisco, consisting of several 6- and 11-story buildings connected by bridges and walkways. In October 2021, Uber acquired Drizly, an alcohol delivery service, for $1.1 billion in cash and stock; it was shut down in early 2024. On January 20, 2022, Uber acquired Australian car-sharing company Car Next Door. In 2022, more than 124,000 internal documents covering the five-year period from 2012 to 2017 when Uber was run by Travis Kalanick were leaked by Mark MacGann, a lobbyist who "led Uber's efforts to win over governments across Europe, the Middle East and Africa". The documents were leaked to The Guardian and first printed on 10 July 2022 by its Sunday sister The Observer. The documents revealed attempts to lobby Joe Biden, Olaf Scholz and George Osborne; how Emmanuel Macron secretly aided Uber lobbying in France, and use of a kill switch during police raids to conceal data. The documents also revealed that Travis Kalanick dismissed concerns from other executives regarding possible violence from taxi drivers after sending Uber drivers to a protest in France, saying "I think it's worth it, violence guarantees success". In February 2023, Uber drivers went on strike in the US and UK to protest wages and fees. They were joined by drivers from Lyft and DoorDash delivery workers. The company posted its first operating profit in 2023. In March 2024, The Wall Street Journal reported a trend of popular service apps such as Uber increasing use of in-app advertising, including higher margin personalized content, to increase profits. Uber was showing customers one ad per trip and tried to implement push alerts but changed its strategy after criticism from customers. In July 2025, Uber partnered with Baidu to deploy Baidu's self-driving cars on its platform outside of the U.S. and mainland China. Also in July 2025, Uber invested over $300 million in Lucid Motors and Nuro and announced the purchase of Lucid Gravity vehicles to develop a robotaxi service. In November 2025, Uber launched the driverless robotaxis in Abu Dhabi in partnership with WeRide, an autonomous driving technology company. This allows passengers who book an UberX or Uber Comfort ride to be matched with a WeRide robotaxi. On February 27, 2015, Uber admitted that it had suffered a data breach more than nine months prior. Names and license plate information from approximately 50,000 drivers were inadvertently disclosed. Uber discovered this leak in September 2014, but waited more than five months to notify the affected individuals. An announcement in November 2017 revealed that in 2016, a separate data breach had disclosed the personal information of 600,000 drivers and 57 million customers. This data included names, email addresses, phone numbers, and drivers' license information. Hackers used employees' usernames and passwords that had been compromised in previous breaches (a "credential stuffing" method) to gain access to a private GitHub repository used by Uber's developers. The hackers located credentials for the company's Amazon Web Services datastore in the repository files, and were able to obtain access to the account records of users and drivers, as well as other data contained in over 100 Amazon S3 buckets. Uber paid a $100,000 ransom to the hackers on the promise they would delete the stolen data. Uber was subsequently criticized for concealing this data breach. Dara Khosrowshahi publicly apologized. In September 2018, in the largest multi-state settlement of a data breach, Uber paid $148 million to the Federal Trade Commission, and admitted that internal access to consumers' personal information was closely monitored on an ongoing basis was false, and stated that it had failed to live up to its promise to provide reasonable security for consumer data. In November 2018, Uber's British divisions were fined £385,000 (reduced to £308,000) by the Information Commissioner's Office. On September 15, 2022, Uber discovered a security breach of its internal network by a hacker that utilized social engineering to obtain an employee's credentials and gain access to the company's VPN and intranet. The company said that no sensitive data had been compromised. On 4 February 2026, Uber announced that it would expand its robotaxi services, with plans to make driverless cars one of its key growth areas and aims to offer driverless vehicles in more than 10 markets globally by the end of 2026. Uber’s partners include Baidu, which has a license to run small-scale driverless trials in Hong Kong, as well as WeRide, which has an autonomous-driving license in parts of Switzerland. Uber also offers driverless rides in Dubai, Abu Dhabi and Riyadh with WeRide, and with Avride in Dallas. Legal issues Uber classifies its drivers as gig workers or independent contractors, which has drawn criticism and legal challenges because it allows the company to withhold worker protections that it would have been required to provide to employees. In New Zealand, four Uber drivers took the company to the Employment Court in 2022, arguing that they should be treated as employees rather than contractors. The Employment Court ruled in favor of the four drivers. Uber filed unsuccessful appeals with the Court of Appeal and subsequently New Zealand's Supreme Court. In November 2025, the Supreme Court dismissed Uber's appeal, thereby upholding the original ruling in favor of the four drivers. In April 2021, an arbitrator ruled against Uber in a case involving Lisa Irving, a blind American customer with a guide dog who was denied rides on 14 separate occasions. Uber was ordered to pay US$1.1 million, reflecting $324,000 in damages and more than $800,000 in attorney fees and court costs. Taxi companies sued Uber, alleging that Uber's policy of violating taxi regulations was a form of unfair competition or a violation of antitrust law. In the U.S., although some courts did find that Uber intentionally violated the taxi rules, Uber prevailed in every case, including the only case to proceed to trial. In Australia, the company agreed to pay $178 million to settle allegations by taxi drivers. In March 2017, an investigation by The New York Times revealed that Uber developed a software tool called "Greyball" to avoid giving rides to known law enforcement officers in areas where its service was illegal such as in Portland, Oregon, Australia, South Korea, and China, leading to government inquiries. The tool identified government officials using geofencing, mining credit card databases, identifying devices, and searches of social media. While at first, Uber stated that it only used the tool to identify riders that violated its terms of service, after investigations by Portland, Oregon, and the United States Department of Justice, Uber admitted to using the tool to skirt local regulations and promised not to use the tool for that purpose. The use of Greyball in London was cited by Transport for London as one of the reasons for its decision not to renew Uber's private hire operator licence in September 2017. A January 2018 report by Bloomberg News stated that Uber routinely used a "panic button" system, codenamed "Ripley", that locked, powered off and changed passwords on staff computers when those offices were subjected to government raids. Uber allegedly used this button at least 24 times, from spring 2015 until late 2016. The company claimed the kill switches were not intended to obstruct justice, but rather to protect intellectual property, customer privacy, and due process and that no data was permanently deleted, and was available for authorities to obtain later. In 2016, Uber hired Ergo, a global security consulting firm, to secretly investigate plaintiffs involved in a class action lawsuit. Ergo operatives posed as acquaintances of the plaintiff's counsel and tried to contact their associates to obtain information. As a result, the judge threw out evidence that was obtained in a fraudulent manner. On February 19, 2017, former Uber engineer Susan Fowler published on her website that she was propositioned for sex by a manager and subsequently threatened with termination of employment by another manager if she continued to report the incident. Travis Kalanick, the CEO at the time, was allegedly aware of the complaint. On February 27, 2017, Amit Singhal, Uber's Senior Vice President of Engineering, was forced to resign after he failed to disclose a sexual harassment claim against him that occurred while he served as Vice President of Google Search. After investigations led by former attorney general Eric Holder and Arianna Huffington, a member of Uber's board of directors, in June 2017, Uber fired over 20 employees. Kalanick took an indefinite leave of absence but, under pressure from investors, he resigned as CEO a week later. Also departing the company in June 2017 was Emil Michael, a senior vice president who suggested that Uber hire a team of opposition researchers and journalists, with a million-dollar budget, to "dig up dirt" on the personal lives and backgrounds of journalists who reported negatively on Uber, specifically targeting Sarah Lacy, editor of PandoDaily, who, in an article published in October 2014, accused Uber of sexism and misogyny in its advertising. In August 2018, Uber agreed to pay a total of $7 million to settle claims of gender discrimination, harassment, and hostile work environment, with 480 employees and former employees receiving $10,700 each and 56 of those employees and former employees receiving an additional $33,900 each. In December 2019, Kalanick resigned from the board of directors of the company and sold his shares. In 2020, the US Department of Justice announced criminal charges against former Chief Security Officer Joe Sullivan for obstruction of justice. The criminal complaint said Joe Sullivan arranged with Travis Kalanick's knowledge, to pay a ransom for the 2016 data breach as a "bug bounty" to conceal its true nature, and for the hackers to falsify non-disclosure agreements to say they had not obtained any data. In January 2024, Uber was fined €10 million by the Dutch Data Protection Authority for violating privacy regulations pertaining to the personal data of its drivers. The authority determined that Uber had failed to provide clear information in its terms and conditions regarding the duration for which it retained drivers' personal data, as well as the measures taken to secure this data when transmitting it to undisclosed entities outside the European Economic Area. In August 2024, Uber was fined €290 million by the Dutch Data Protection Authority for transferring the personal data of European drivers to US servers in breach of the GDPR. In April 2025, the Federal Trade Commission (FTC) sued Uber, alleging that it enrolled some of its customers in the $9.99 monthly Uber One service without their consent, and used unlawful tactics to make cancellation difficult for consumers. In December 2025, 21 US states and Washington, D.C. joined the FTC in filing an amended complaint seeking civil penalties against Uber for allegedly violating both state laws and the federal Restore Online Shoppers' Confidence Act. In February 2024, a multidistrict litigation (MDL) was established in the Northern District of California against Uber Technologies, Inc., consolidating numerous claims from among the more than 3,000 sexual assault lawsuits filed against the company in state and federal courts. These lawsuits allege Uber prioritized growth over safety by using inadequate background checks, skipping in-person driver vetting, and failing to invest in preventive measures such as cameras or monitoring systems. It also claims Uber knowingly put vulnerable passengers, such as intoxicated women, at risk through its marketing and business practices. The litigation seeks injunctive relief, damages and changes to Uber's safety policies. Some survivors have chosen to pursue justice in state courts outside of the MDL, seeking faster resolutions and a more individualized approach. In 2020, 5,000 drivers filed wage and hour claims with the California labour commission office against Uber and Lyft, alleging they were misclassified as independent contractors. Rideshare Drivers United in California claimed that at least 250,000 individual rideshare drivers in California who drove for the apps between 2016 and 2020 are estimated to be eligible for the settlement for wage theft claims of tens of billions of dollars. Corporate affairs Gallery References Further reading Scholarly papers Books Articles External links |
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[SOURCE: https://en.wikipedia.org/wiki/Mars_Climate_Sounder] | [TOKENS: 7484] |
Contents Mars Reconnaissance Orbiter The Mars Reconnaissance Orbiter (MRO) is a spacecraft designed to search for the existence of water on Mars and provide support for missions to Mars, as part of NASA's Mars Exploration Program. It was launched from Cape Canaveral on August 12, 2005, at 11:43 UTC and reached Mars on March 10, 2006, at 21:24 UTC. In November 2006, after six months of aerobraking, it entered its final science orbit and began its primary science phase. Mission objectives include observing the climate of Mars, investigating geologic forces, providing reconnaissance of future landing sites, and relaying data from surface missions back to Earth. To support these objectives, the MRO carries different scientific instruments, including three cameras, two spectrometers and a subsurface radar. As of July 29, 2023, the MRO has returned over 450 terabits of data, helped choose safe landing sites for NASA's Mars landers, discovered pure water ice in new craters and further evidence that water once flowed on the surface on Mars. The spacecraft continues to operate at Mars, far beyond its intended design life. Due to its critical role as a high-speed data-relay for ground missions, NASA intends to continue the mission as long as possible, at least through the late 2020s. As of February 21, 2026, the MRO has been active at Mars for 7093 sols, or 19 years, 11 months and 11 days, and is the third longest-lived spacecraft to orbit Mars, after 2001 Mars Odyssey and Mars Express. Pre-launch After the failures of the Mars Climate Orbiter and the Mars Polar Lander missions in 1999, NASA reorganized and replanned its Mars Exploration Program. In October 2000, NASA announced its reformulated Mars plans, which reduced the number of planned missions and introduced a new theme, "follow the water". The plans included the Mars Reconnaissance Orbiter (MRO), to be launched in 2005. On October 3, 2001, NASA chose Lockheed Martin as the primary contractor for the spacecraft's fabrication. By the end of 2001 all of the mission's instruments were selected. There were no major setbacks during the MRO's construction, and the spacecraft arrived at John F. Kennedy Space Center on April 30, 2005, for launch preparations. Mission objectives MRO has both scientific and "mission support" objectives which were carried out during the mission's phases. The Primary Science Phase lasted until November 2008, at which time NASA declared the mission a success.: 18 The Extended Science Phase, lasting from 2008 to 2010, was initially planned to support the Phoenix lander and the Mars Science Laboratory, but they were uncontactable and delayed respectively, freeing up the MRO to further study Mars.: 19–20 After 2010, the mission consisted of Extended Mission (EM) phases, each lasting two years up to EM4, and three years from then on.: 28 As of 2024, the MRO is on its 6th extended mission.: 13 The formal science objectives of MRO are to observe the present climate, particularly its atmospheric circulation and seasonal variations; search for signs of water, both past and present, and understand how it altered the planet's surface; map and characterize the geological forces that shaped the surface. To support other missions to Mars, the MRO also has mission support objectives. They are to provide data relay services from ground missions back to Earth, characterize the safety and feasibility of potential future landing sites and Mars rover traverses, and capture data from the entry, descent and landing phase of rovers.: 12 MRO played a key role in choosing safe landing sites for the Phoenix lander in 2008, Mars Science Laboratory / Curiosity rover in 2012, InSight lander in 2018, and the Mars 2020 / Perseverance rover in 2021. Launch and orbital insertion On August 12, 2005, MRO was launched aboard an Atlas V-401 rocket from Space Launch Complex 41 at Cape Canaveral Air Force Station. The Centaur upper stage of the rocket completed its burns over a 56-minute period and placed MRO into an interplanetary transfer orbit towards Mars. MRO cruised through interplanetary space for seven and a half months before reaching Mars. While en route, most of the scientific instruments and experiments were tested and calibrated. To ensure proper orbital insertion upon reaching Mars, four trajectory correction maneuvers were planned and a fifth emergency maneuver was discussed. However, only three trajectory correction maneuvers were necessary, which saved 27 kilograms (60 lb) of fuel that would be usable during MRO's extended mission. MRO began orbital insertion by approaching Mars on March 10, 2006, and passing above its southern hemisphere at an altitude of 370–400 kilometers (230–250 miles). All six of MRO's main engines burned for 27 minutes to slow the probe by 1,000 meters per second (3,300 ft/s). The burn was remarkably accurate, as the insertion route had been designed more than three months prior, with the achieved change in speed only 0.01% short from the design, necessitating an additional 35-second burn time. Completion of the orbital insertion placed the orbiter in a highly elliptical polar orbit with a period of approximately 35.5 hours. Shortly after insertion, the periapsis – the point in the orbit closest to Mars – was 426 km (265 mi) from the surface (3,806 km (2,365 mi) from the planet's center). The apoapsis – the point in the orbit farthest from Mars – was 44,500 km (27,700 mi) from the surface (47,972 km (29,808 mi) from the planet's center). When MRO entered orbit, it joined five other active spacecraft that were either in orbit or on the planet's surface: Mars Global Surveyor, Mars Express, 2001 Mars Odyssey, and the two Mars Exploration Rovers (Spirit and Opportunity). This set a new record for the most operational spacecraft in the immediate vicinity of Mars. On March 30, 2006, MRO began the process of aerobraking, a three-step procedure that halved the fuel needed to achieve a lower, more circular orbit with a shorter period. First, during its first five orbits of the planet (one Earth week), MRO used its thrusters to drop the periapsis of its orbit into aerobraking altitude. Second, while using its thrusters to make minor corrections to its periapsis altitude, MRO maintained aerobraking altitude for 445 planetary orbits (about five Earth months) to reduce the apoapsis of the orbit to 450 kilometers (280 mi). This was done in such a way so as to not heat the spacecraft too much, but also dip enough into the atmosphere to slow the spacecraft down. Third, after the process was complete, MRO used its thrusters to move its periapsis out of the edge of the atmosphere on August 30, 2006. In September 2006, MRO fired its thrusters twice more to adjust its final, nearly circular orbit to approximately 250 to 316 km (155 to 196 mi) above the surface, with a period of about 112 minutes and a polar inclination of around 93°.: 6 The SHARAD radar antennas were deployed on September 16. All of the scientific instruments were tested and most were turned off prior to the solar conjunction that occurred from October 7 to November 6, 2006. This was done to prevent charged particles from the Sun from interfering with signals and potentially endangering the spacecraft. After the conjunction ended the "primary science phase" began. Timeline On September 29, 2006 (sol 402), MRO took its first high resolution image from its science orbit. This image is said to resolve items as small as 90 cm (3 feet) in diameter. On October 6, NASA released detailed pictures from the MRO of Victoria crater along with the Opportunity rover on the rim above it. In November, problems began to surface in the operation of two MRO spacecraft instruments. A stepping mechanism in the Mars Climate Sounder (MCS) skipped on multiple occasions resulting in a field of view that was slightly out of position. By December, normal operations of the instrument had been suspended, although a mitigation strategy allows the instrument to continue making most of its intended observations. Also, an increase in noise and resulting bad pixels has been observed in several CCDs of the High Resolution Imaging Science Experiment (HiRISE). Operation of this camera with a longer warm-up time[a] has alleviated the issue. However, the cause is still unknown and may return. On November 17, 2006, NASA announced the successful test of the MRO as an orbital communications relay. Using the NASA rover Spirit as the point of origin for the transmission, the MRO acted as a relay for transmitting data back to Earth. HiRISE was able to photograph the Phoenix lander during its parachuted descent to Vastitas Borealis on May 25, 2008 (sol 990). The orbiter continued to experience recurring problems in 2009, including four spontaneous resets, culminating in a four-month shut-down of the spacecraft from August to December. Though engineers were not able to determine the cause of the recurrent resets, they suspected a piece of electronics had been affected by radiation. While investigating, the engineers discovered and fixed a flaw that could have deleted all critical information onboard the MRO.: 7 Another spontaneous reset occurred in September 2010. On March 3, 2010, the MRO passed another significant milestone, having transmitted over 100 terabits of data back to Earth, which was more than all other interplanetary probes sent from Earth combined. In December 2010, the first Extended Mission began. Goals included exploring seasonal processes, searching for surface changes, and providing support for other Martian spacecraft. This lasted until October 2012, after which NASA started the MRO's second Extended Mission, which lasted until October 2014. As of 2023, the MRO has completed five missions, and is currently on its sixth. On August 6, 2012 (sol 2483), the orbiter passed over Gale crater, the landing site of the Mars Science Laboratory mission, during its EDL phase. It captured an image via the HiRISE camera of the Curiosity rover descending with its backshell and supersonic parachute. In December 2014 and April 2015, Curiosity was photographed again by HiRISE inside Gale Crater. Another computer anomaly occurred on March 9, 2014, when the MRO put itself into safe mode after an unscheduled swap from one computer to another. The MRO resumed normal science operations four days later. This occurred again on April 11, 2015, after which the MRO returned to full operational capabilities a week later. NASA reported that the MRO, as well as the Mars Odyssey Orbiter and MAVEN orbiter had a chance to study the Comet Siding Spring flyby on October 19, 2014. To minimize risk of damage from the material shed by the comet, the MRO made orbital adjustments on July 2, 2014, and August 27, 2014. During the flyby, the MRO took the best ever pictures of a comet from the Oort cloud and was not damaged. In January 2015, the MRO discovered and identified the wreckage of Britain's Beagle 2, which was lost during its landing phase in 2003 and was thought to have crashed. The images revealed that Beagle 2 had actually landed safely, but one or two of its solar panels had failed to fully deploy, which blocked the radio antenna. In October 2016, the crash site of another lost spacecraft, Schiaparelli EDM, was photographed by the MRO, using both the CTX and HiRISE cameras. On July 29, 2015, the MRO was placed into a new orbit to provide communications support during the anticipated arrival of the InSight Mars lander mission in September 2016. The maneuver's engine burn lasted for 75 seconds. InSight was delayed and missed the 2016 launch window, but was successfully launched during the next window on May 5, 2018, and landed on November 26, 2018. Due to the longevity of the mission, a number of MRO components have started deteriorating. From the start of the mission in 2005 to 2017, the MRO had used a miniature inertial measurement unit (MIMU) for altitude and orientation control. After 58,000 hours of use, and limited signs of life, the orbiter switched over to a backup, which, as of 2018, has reached 52,000 hours of use. To conserve the life of the backup, NASA switched from MIMUs to an "all-stellar" mode for routine operations in 2018. The "all-stellar" mode uses cameras and pattern recognition software to determine the location of stars, which can then be used to identify the MRO's orientation. Problems with blurring in pictures from HiRISE and battery degradation also arose in 2017 but have since been resolved. In August 2023, electronic units within the HiRISE's CCD RED4 sensor began to fail as well, and are causing visual artifacts in pictures taken. In 2017, the cryocoolers used by CRISM completed their lifecycle, limiting the instrument's capabilities to visible wavelengths, instead of its full wavelength range. In 2022, NASA announced the shutdown of CRISM in its entirety, and the instrument was formally retired on April 3, 2023, after creating two final, near global, maps using prior data and a more limited second spectrometer that did not require cryocoolers. As of January 2024[update], the MRO has around 132 kg of fuel remaining, enough to support operations until 2035.: 3 Instruments Three cameras, two spectrometers and a radar are included on the orbiter along with three engineering instruments and two "science-facility experiments", which use data from engineering subsystems to collect science data. Two of the engineering instruments are being used to test and demonstrate new equipment for future missions. The MRO takes around 29,000 images per year. The High Resolution Imaging Science Experiment (HiRISE) camera is a 0.5 m (1 ft 8 in) reflecting telescope, the largest ever carried on a deep space mission, and has a resolution of 1 microradian, or 0.3 m (1 ft 0 in) from an altitude of 300 km (190 mi). In comparison, satellite images of Earth are generally available with a resolution of 0.5 m (1 ft 8 in). HiRISE collects images in three color bands, 400 to 600 nm (blue–green or B–G), 550 to 850 nm (red) and 800 to 1,000 nm (near infrared). Red color images are 20,264 pixels across (6 km (3.7 mi) wide), and B–G and NIR are 4,048 pixels across (1.2 km (0.75 mi) wide). HiRISE's onboard computer reads these lines in time with the orbiter's ground speed, and images are potentially unlimited in length. Practically however, their length is limited by the computer's 28 Gb memory capacity, and the nominal maximum size is 20,000 × 40,000 pixels (800 megapixels) and 4,000 × 40,000 pixels (160 megapixels) for B–G and NIR images. Each 16.4 Gb image is compressed to 5 Gb before transmission and release to the general public on the HiRISE website in JPEG 2000 format. To facilitate the mapping of potential landing sites, HiRISE can produce stereo pairs of images from which topography can be calculated to an accuracy of 0.25 m (9.8 in). HiRISE was built by Ball Aerospace & Technologies Corp. The Context Camera (CTX) provides grayscale images (500 to 800 nm) with a pixel resolution up to about 6 m (20 ft). CTX is designed to provide context maps for the targeted observations of HiRISE and CRISM, and is also used to mosaic large areas of Mars, monitor a number of locations for changes over time, and to acquire stereo (3D) coverage of key regions and potential future landing sites. The optics of CTX consist of a 350 mm (14 in) focal length Maksutov Cassegrain telescope with a 5,064 pixel wide line array CCD. The instrument takes pictures 30 km (19 mi) wide and has enough internal memory to store an image 160 km (99 mi) long before loading it into the main computer. The camera was built, and is operated by Malin Space Science Systems. CTX had mapped more than 99% of Mars by March 2017 and helped create an interactive map of Mars in 2023. The Mars Color Imager (MARCI) is a wide-angle, relatively low-resolution camera that views the surface of Mars in five visible and two ultraviolet bands. Each day, MARCI collects about 84 images and produces a global map with pixel resolutions of 1 to 10 km (0.62 to 6.21 mi). This map provides a weekly weather report for Mars, helps to characterize its seasonal and annual variations, and maps the presence of water vapor and ozone in its atmosphere. The camera was built and is operated by Malin Space Science Systems. It has a 180-degree fisheye lens with the seven color filters bonded directly on a single CCD sensor. The same MARCI camera was onboard Mars Climate Orbiter launched in 1998. The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument is a visible and near infrared spectrometer that is used to produce detailed maps of the surface mineralogy of Mars. It operates from 362 to 3920 nm, measures the spectrum in 544 channels (each 6.55 nm wide), and has a resolution of 18 m (59 ft) at an altitude of 300 km (190 mi). CRISM is being used to identify minerals and chemicals indicative of the past or present existence of water on the surface of Mars. These materials include iron oxides, phyllosilicates, and carbonates, which have characteristic patterns in their visible-infrared energy. The CRISM instrument was shut down on April 3, 2023. The Mars Climate Sounder (MCS) is a radiometer that looks both down and horizontally through the atmosphere in order to quantify the atmosphere's vertical variations. It has one visible/near infrared channel (0.3 to 3.0 μm) and eight far infrared (12 to 50 μm) channels selected for the purpose. MCS observes the atmosphere on the horizon of Mars (as viewed from MRO) by breaking it up into vertical slices and taking measurements within each slice in 5 km (3.1 mi) increments. These measurements are assembled into daily global weather maps to show the basic variables of Martian weather: temperature, pressure, humidity, and dust density. The MCS weighs roughly 9 kg (20 lb) and began operation in November 2006. Since beginning operation, it has helped create maps of mesospheric clouds, study and categorize dust storms, and provide direct evidence of carbon dioxide snow on Mars. This instrument, supplied by NASA's Jet Propulsion Laboratory (JPL), is an updated version of a heavier, larger instrument originally developed at JPL for the 1992 Mars Observer and 1998 Mars Climate Orbiter missions, which both failed. The Shallow Radar (SHARAD) sounder experiment onboard MRO is designed to probe the internal structure of the Martian polar ice caps. It also gathers planet-wide information about underground layers of regolith, rock, and ice that might be accessible from the surface. SHARAD emits HF radio waves between 15 and 25 MHz, a range that allows it to resolve layers as thin as 7 m (23 ft) to a maximum depth of 3 km (1.864 mi). It has a horizontal resolution of 0.3 to 3 km (0.2 to 1.9 mi). SHARAD is designed to complement the Mars Express MARSIS instrument, which has coarser resolution but penetrates to a much greater depth. Both SHARAD and MARSIS were made by the Italian Space Agency. In addition to its imaging equipment, MRO carries three engineering instruments. The Electra communications package is a UHF software-defined radio that provides a flexible platform for evolving relay capabilities. It is designed to communicate with other spacecraft as they approach, land, and operate on Mars. In addition to protocol controlled inter-spacecraft data links of 1 kbit/s to 2 Mbit/s, Electra also provides Doppler data collection, open loop recording and a highly accurate timing service based on an ultra-stable oscillator. Doppler information for approaching vehicles can be used for final descent targeting or descent and landing trajectory recreation. Doppler information on landed vehicles allows scientists to accurately determine the surface location of Mars landers and rovers. The two Mars Exploration Rover (MER) spacecraft utilized an earlier generation UHF relay radio providing similar functions through the Mars Odyssey orbiter. The Electra radio has relayed information to and from the MER spacecraft, Phoenix lander and Curiosity rover. During the cruise phase, the MRO also used the Ka band Telecommunications Experiment Package to demonstrate a less power-intensive way to communicate with Earth. The Optical Navigation Camera images the Martian moons, Phobos and Deimos, against background stars to precisely determine MRO's orbit. Although this is not critical, it was included as a technology test for future orbiting and landing of spacecraft. The Optical Navigation Camera was tested successfully in February and March 2006. It was subsequently turned off, but was turned back on in 2022 to collect data for a potential NASA-ESA Mars Sample Return mission.: 11 Two additional science investigations are also on the spacecraft. The Gravity Field Investigation Package measures variations in the Martian gravitational field through variations in the spacecraft's speed. Speed changes are detected by measuring doppler shifts in MRO's radio signals received on Earth. Data from this investigation can be used to understand the subsurface geology of Mars, determine the density of the atmosphere and track seasonal changes in the location of carbon dioxide deposited on the surface. Due to decreased budgets, data collection ended in 2022.: 8 The Atmospheric Structure Investigation used sensitive onboard accelerometers to deduce the in situ atmospheric density of Mars during aerobraking. The measurements helped provide greater understanding of seasonal wind variations, the effects of dust storms, and the structure of the atmosphere. Spacecraft systems Workers at Lockheed Martin Space Systems in Denver assembled the spacecraft structure and attached the instruments. Instruments were constructed at the Jet Propulsion Laboratory, the University of Arizona Lunar and Planetary Laboratory in Tucson, Arizona, Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, the Italian Space Agency in Rome, and Malin Space Science Systems in San Diego. The structure is made mostly of carbon composites and aluminum-honeycombed plates. The titanium fuel tank takes up most of the volume and mass of the spacecraft and provides most of its structural integrity. The spacecraft's total mass is less than 2,180 kg (4,810 lb) with an unfueled dry mass less than 1,031 kg (2,273 lb). MRO gets all of its electrical power from two solar panels, each of which can move independently around two axes (up-down, or left-right rotation). Each solar panel measures 5.35 m × 2.53 m (17.6 ft × 8.3 ft) and has 9.5 m2 (102 sq ft) covered with 3,744 individual photovoltaic cells. Its high-efficiency solar cells are able to convert more than 26% of the energy it receives from the Sun directly into electricity and are connected together to produce a total output of 32 volts. Whilst orbiting Mars, the panels together produce 600–2000[b] watts of power; in contrast, the panels would generate 6,000 watts in a comparable Earth orbit by being closer to the Sun. MRO has two rechargeable nickel-hydrogen batteries used to power the spacecraft when it is not facing the Sun. Each battery has an energy storage capacity of 50 ampere hours (180 kC). The full range of the batteries cannot be used due to voltage constraints on the spacecraft, but allows the operators to extend the battery life—a valuable capability, given that battery drain is one of the most common causes of long-term satellite failure. Planners anticipate that only 40% of the batteries' capacities will be required during the lifetime of the spacecraft. MRO's main computer is a 133 MHz, 10.4 million transistor, 32-bit, RAD750 processor, a radiation-hardened version of a PowerPC 750 or G3 processor with a purpose-built motherboard. The operating system software is VxWorks and has extensive fault protection protocols and monitoring. Data is stored in a 160 Gbit (20 GB) flash memory module consisting of over 700 memory chips, each with a 256 Mbit capacity. This memory capacity is not actually that large considering the amount of data to be acquired; for example, a single image from the HiRISE camera can be as large as 28 Gb. When it was launched, the Telecom Subsystem on MRO was the best digital communication system sent into deep space, and for the first time used capacity-approaching turbo-codes. It was more powerful than any previous deep space mission, and is able to transmit data more than ten times faster than previous Mars missions. Along with the Electra communications package, the system consists of a very large (3 m (9.8 ft)) High Gain Antenna, which is used to transmit data to the Deep Space Network on Earth via X-band frequencies at 8.41 GHz. It also demonstrates the use of the Ka band at 32 GHz for higher data rates. Maximum transmission speed from Mars can be as high as 6 Mbit/s, but averages between 0.5 and 4 Mbit/s. The spacecraft carries two 100-watt X-band Travelling Wave Tube Amplifiers (TWTA) (one of which is a backup), one 35-watt Ka-band amplifier, and two Small Deep Space Transponders (SDSTs). Two smaller low-gain antennas are also present for lower-rate communication during emergencies and special events. These antennas do not have focusing dishes and can transmit and receive from any direction. They are an important backup system to ensure that MRO can always be reached, even if its main antenna is pointed away from the Earth. The Ka band subsystem was used to show how such a system could be used by spacecraft in the future. Due to lack of spectrum at 8.41 GHz X-band, future high-rate deep space missions will use 32 GHz Ka-band. NASA Deep Space Network (DSN) implemented Ka-band receiving capabilities at all three of its complexes (Goldstone, Canberra and Madrid) over its 34-m beam-waveguide (BWG) antenna subnet. Ka-band tests were also planned during the science phase, but during aerobraking a switch failed, limiting the X-band high gain antenna to a single amplifier. If this amplifier fails all high-speed X-band communications will be lost. The Ka downlink is the only remaining backup for this functionality, and since the Ka-band capability of one of the SDST transponders has already failed, (and the other might have the same problem) JPL decided to halt all Ka-band demonstrations and hold the remaining capability in reserve. By November 2013, the MRO had passed 200 terabits in the amount of science data returned. The data returned by the mission is more than three times the total data returned via NASA's Deep Space Network for all the other missions managed by NASA's Jet Propulsion Laboratory over the past 10 years. The spacecraft uses a 1,175 L (258 imp gal; 310 US gal) fuel tank filled with 1,187 kg (2,617 lb) of hydrazine monopropellant. Fuel pressure is regulated by adding pressurized helium gas from an external tank. Seventy percent of the propellant was used for orbital insertion, and it has enough propellant to keep functioning into the 2030s. MRO has 20 rocket engine thrusters on board. Six large thrusters each produce 170 N (38 lbf) of thrust for a total of 1,020 N (230 lbf) meant mainly for orbital insertion. These thrusters were originally designed for the Mars Surveyor 2001 Lander. Six medium thrusters each produce 22 N (4.9 lbf) of thrust for trajectory correction maneuvers and attitude control during orbit insertion. Finally, eight small thrusters each produce 0.9 N (0.20 lbf) of thrust for attitude control during normal operations. Four reaction wheels are also used for precise attitude control during activities requiring a highly stable platform, such as high-resolution imaging, in which even small motions can cause blurring of the image. Each wheel is used for one axis of motion. The fourth wheel is a backup in case one of the other three wheels fails. Each wheel weighs 10 kg (22 lb) and can be spun as fast as 100 Hz or 6,000 rpm. In order to determine the spacecraft's orbit and facilitate maneuvers, 16 Sun sensors – eight primaries and eight backups – are placed around the spacecraft to calibrate solar direction relative to the orbiter's frame. Two star trackers, digital cameras used to map the position of catalogued stars, provide NASA with full, three-axis knowledge of the spacecraft orientation and attitude. A primary and backup Miniature Inertial Measurement Unit (MIMU), provided by Honeywell, measures changes to the spacecraft attitude as well as any non-gravitationally induced changes to its linear velocity. Each MIMU is a combination of three accelerometers and three ring-laser gyroscopes. These systems are all critically important to MRO, as it must be able to point its camera to a very high precision in order to take the high-quality pictures that the mission requires. It has also been specifically designed to minimize any vibrations on the spacecraft, so as to allow its instruments to take images without any distortions caused by vibrations. Cost The total cost of the MRO through the end of its prime mission was $716.6 million. Of this amount, $416.6 million was spent on spacecraft development, approximately $90 million for its launch, and $210 million for 5 years of mission operations. Since 2011, MRO's annual operations costs are, on average, $31 million per year, when adjusted for inflation. The MRO's science budget has, like other long term missions, been declining, leading to reduced science activity.: 44 Discoveries An article in the journal Science in September 2009, reported that some new craters on Mars have excavated relatively pure water ice. After being exposed, the ice gradually fades as it sublimates away. These new craters were found and dated by the CTX camera, and the identification of the ice was confirmed using CRISM. The ice was found in a five locations, three of which were in the Cebrenia quadrangle. These locations are 55°34′N 150°37′E / 55.57°N 150.62°E / 55.57; 150.62; 43°17′N 176°54′E / 43.28°N 176.9°E / 43.28; 176.9; and 45°00′N 164°30′E / 45°N 164.5°E / 45; 164.5. Two others are in the Diacria quadrangle: 46°42′N 176°48′E / 46.7°N 176.8°E / 46.7; 176.8 and 46°20′N 176°54′E / 46.33°N 176.9°E / 46.33; 176.9. Radar results from SHARAD suggested that features termed lobate debris aprons (LDAs) contain large amounts of water ice. Of interest from the days of the Viking Orbiters, these LDA are aprons of material surrounding cliffs. They have a convex topography and a gentle slope; this suggests flow away from the steep source cliff. In addition, lobate debris aprons can show surface lineations just as rock glaciers on the Earth. SHARAD has provided strong evidence that the LDAs in Hellas Planitia are glaciers that are covered with a thin layer of debris (i.e. rocks and dust); a strong reflection from the top and base of LDAs was observed, suggesting that pure water ice makes up the bulk of the formation (between the two reflections). Based on the experiments of the Phoenix lander and the studies of the Mars Odyssey from orbit, water ice is known to exist just under the surface of Mars in the far north and south (high latitudes). Using data from Mars Global Surveyor, Mars Odyssey, and the MRO, scientists have found widespread deposits of chloride minerals. Evidence suggests that the deposits were formed from the evaporation of mineral enriched waters. The research suggests that lakes may have been scattered over large areas of the Martian surface. Usually, chlorides are the last minerals to come out of solution. Carbonates, sulfates, and silica should precipitate out ahead of them. Sulfates and silica have been found by the Mars rovers on the surface. Places with chloride minerals may have once held various life forms. Furthermore, such areas could preserve traces of ancient life. In 2009, a group of scientists from the CRISM team reported on nine to ten different classes of minerals formed in the presence of water. Different types of clays (also called phyllosilicates) were found in many locations. The phyllosilicates identified included aluminum smectite, iron/magnesium smectite, kaolinite, prehnite, and chlorite. Rocks containing carbonate were found around the Isidis basin. Carbonates belong to one class in which life could have developed. Areas around Valles Marineris were found to contain hydrated silica and hydrated sulfates. The researchers identified hydrated sulfates and ferric minerals in Terra Meridiani and in Valles Marineris. Other minerals found on Mars were jarosite, alunite, hematite, opal, and gypsum. Two to five of the mineral classes were formed with the right pH and sufficient water to permit life to grow. On August 4, 2011 (sol 2125), NASA announced that MRO had detected dark streaks on slopes, known as recurring slope lineae caused by what appeared to be flowing salty water on the surface or subsurface of Mars. On September 28, 2015, this finding was confirmed at a special NASA news conference. In 2017, however, further research suggested that the dark streaks were created by grains of sand and dust slipping down slopes, and not water darkening the ground. See also Notes References This article incorporates public domain material from websites or documents of the National Aeronautics and Space Administration. Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/Animal#cite_note-Budd2015-111] | [TOKENS: 6011] |
Contents Animal Animals are multicellular, eukaryotic organisms belonging to the biological kingdom Animalia (/ˌænɪˈmeɪliə/). With few exceptions, animals consume organic material, breathe oxygen, have myocytes and are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. Animals form a clade, meaning that they arose from a single common ancestor. Over 1.5 million living animal species have been described, of which around 1.05 million are insects, over 85,000 are molluscs, and around 65,000 are vertebrates. It has been estimated there are as many as 7.77 million animal species on Earth. Animal body lengths range from 8.5 μm (0.00033 in) to 33.6 m (110 ft). They have complex ecologies and interactions with each other and their environments, forming intricate food webs. The scientific study of animals is known as zoology, and the study of animal behaviour is known as ethology. The animal kingdom is divided into five major clades, namely Porifera, Ctenophora, Placozoa, Cnidaria and Bilateria. Most living animal species belong to the clade Bilateria, a highly proliferative clade whose members have a bilaterally symmetric and significantly cephalised body plan, and the vast majority of bilaterians belong to two large clades: the protostomes, which includes organisms such as arthropods, molluscs, flatworms, annelids and nematodes; and the deuterostomes, which include echinoderms, hemichordates and chordates, the latter of which contains the vertebrates. The much smaller basal phylum Xenacoelomorpha have an uncertain position within Bilateria. Animals first appeared in the fossil record in the late Cryogenian period and diversified in the subsequent Ediacaran period in what is known as the Avalon explosion. Nearly all modern animal phyla first appeared in the fossil record as marine species during the Cambrian explosion, which began around 539 million years ago (Mya), and most classes during the Ordovician radiation 485.4 Mya. Common to all living animals, 6,331 groups of genes have been identified that may have arisen from a single common ancestor that lived about 650 Mya during the Cryogenian period. Historically, Aristotle divided animals into those with blood and those without. Carl Linnaeus created the first hierarchical biological classification for animals in 1758 with his Systema Naturae, which Jean-Baptiste Lamarck expanded into 14 phyla by 1809. In 1874, Ernst Haeckel divided the animal kingdom into the multicellular Metazoa (now synonymous with Animalia) and the Protozoa, single-celled organisms no longer considered animals. In modern times, the biological classification of animals relies on advanced techniques, such as molecular phylogenetics, which are effective at demonstrating the evolutionary relationships between taxa. Humans make use of many other animal species for food (including meat, eggs, and dairy products), for materials (such as leather, fur, and wool), as pets and as working animals for transportation, and services. Dogs, the first domesticated animal, have been used in hunting, in security and in warfare, as have horses, pigeons and birds of prey; while other terrestrial and aquatic animals are hunted for sports, trophies or profits. Non-human animals are also an important cultural element of human evolution, having appeared in cave arts and totems since the earliest times, and are frequently featured in mythology, religion, arts, literature, heraldry, politics, and sports. Etymology The word animal comes from the Latin noun animal of the same meaning, which is itself derived from Latin animalis 'having breath or soul'. The biological definition includes all members of the kingdom Animalia. In colloquial usage, the term animal is often used to refer only to nonhuman animals. The term metazoa is derived from Ancient Greek μετα meta 'after' (in biology, the prefix meta- stands for 'later') and ζῷᾰ zōia 'animals', plural of ζῷον zōion 'animal'. A metazoan is any member of the group Metazoa. Characteristics Animals have several characteristics that they share with other living things. Animals are eukaryotic, multicellular, and aerobic, as are plants and fungi. Unlike plants and algae, which produce their own food, animals cannot produce their own food, a feature they share with fungi. Animals ingest organic material and digest it internally. Animals have structural characteristics that set them apart from all other living things: Typically, there is an internal digestive chamber with either one opening (in Ctenophora, Cnidaria, and flatworms) or two openings (in most bilaterians). Animal development is controlled by Hox genes, which signal the times and places to develop structures such as body segments and limbs. During development, the animal extracellular matrix forms a relatively flexible framework upon which cells can move about and be reorganised into specialised tissues and organs, making the formation of complex structures possible, and allowing cells to be differentiated. The extracellular matrix may be calcified, forming structures such as shells, bones, and spicules. In contrast, the cells of other multicellular organisms (primarily algae, plants, and fungi) are held in place by cell walls, and so develop by progressive growth. Nearly all animals make use of some form of sexual reproduction. They produce haploid gametes by meiosis; the smaller, motile gametes are spermatozoa and the larger, non-motile gametes are ova. These fuse to form zygotes, which develop via mitosis into a hollow sphere, called a blastula. In sponges, blastula larvae swim to a new location, attach to the seabed, and develop into a new sponge. In most other groups, the blastula undergoes more complicated rearrangement. It first invaginates to form a gastrula with a digestive chamber and two separate germ layers, an external ectoderm and an internal endoderm. In most cases, a third germ layer, the mesoderm, also develops between them. These germ layers then differentiate to form tissues and organs. Repeated instances of mating with a close relative during sexual reproduction generally leads to inbreeding depression within a population due to the increased prevalence of harmful recessive traits. Animals have evolved numerous mechanisms for avoiding close inbreeding. Some animals are capable of asexual reproduction, which often results in a genetic clone of the parent. This may take place through fragmentation; budding, such as in Hydra and other cnidarians; or parthenogenesis, where fertile eggs are produced without mating, such as in aphids. Ecology Animals are categorised into ecological groups depending on their trophic levels and how they consume organic material. Such groupings include carnivores (further divided into subcategories such as piscivores, insectivores, ovivores, etc.), herbivores (subcategorised into folivores, graminivores, frugivores, granivores, nectarivores, algivores, etc.), omnivores, fungivores, scavengers/detritivores, and parasites. Interactions between animals of each biome form complex food webs within that ecosystem. In carnivorous or omnivorous species, predation is a consumer–resource interaction where the predator feeds on another organism, its prey, who often evolves anti-predator adaptations to avoid being fed upon. Selective pressures imposed on one another lead to an evolutionary arms race between predator and prey, resulting in various antagonistic/competitive coevolutions. Almost all multicellular predators are animals. Some consumers use multiple methods; for example, in parasitoid wasps, the larvae feed on the hosts' living tissues, killing them in the process, but the adults primarily consume nectar from flowers. Other animals may have very specific feeding behaviours, such as hawksbill sea turtles which mainly eat sponges. Most animals rely on biomass and bioenergy produced by plants and phytoplanktons (collectively called producers) through photosynthesis. Herbivores, as primary consumers, eat the plant material directly to digest and absorb the nutrients, while carnivores and other animals on higher trophic levels indirectly acquire the nutrients by eating the herbivores or other animals that have eaten the herbivores. Animals oxidise carbohydrates, lipids, proteins and other biomolecules in cellular respiration, which allows the animal to grow and to sustain basal metabolism and fuel other biological processes such as locomotion. Some benthic animals living close to hydrothermal vents and cold seeps on the dark sea floor consume organic matter produced through chemosynthesis (via oxidising inorganic compounds such as hydrogen sulfide) by archaea and bacteria. Animals originated in the ocean; all extant animal phyla, except for Micrognathozoa and Onychophora, feature at least some marine species. However, several lineages of arthropods begun to colonise land around the same time as land plants, probably between 510 and 471 million years ago, during the Late Cambrian or Early Ordovician. Vertebrates such as the lobe-finned fish Tiktaalik started to move on to land in the late Devonian, about 375 million years ago. Other notable animal groups that colonized land environments are Mollusca, Platyhelmintha, Annelida, Tardigrada, Onychophora, Rotifera, Nematoda. Animals occupy virtually all of earth's habitats and microhabitats, with faunas adapted to salt water, hydrothermal vents, fresh water, hot springs, swamps, forests, pastures, deserts, air, and the interiors of other organisms. Animals are however not particularly heat tolerant; very few of them can survive at constant temperatures above 50 °C (122 °F) or in the most extreme cold deserts of continental Antarctica. The collective global geomorphic influence of animals on the processes shaping the Earth's surface remains largely understudied, with most studies limited to individual species and well-known exemplars. Diversity The blue whale (Balaenoptera musculus) is the largest animal that has ever lived, weighing up to 190 tonnes and measuring up to 33.6 metres (110 ft) long. The largest extant terrestrial animal is the African bush elephant (Loxodonta africana), weighing up to 12.25 tonnes and measuring up to 10.67 metres (35.0 ft) long. The largest terrestrial animals that ever lived were titanosaur sauropod dinosaurs such as Argentinosaurus, which may have weighed as much as 73 tonnes, and Supersaurus which may have reached 39 metres. Several animals are microscopic; some Myxozoa (obligate parasites within the Cnidaria) never grow larger than 20 μm, and one of the smallest species (Myxobolus shekel) is no more than 8.5 μm when fully grown. The following table lists estimated numbers of described extant species for the major animal phyla, along with their principal habitats (terrestrial, fresh water, and marine), and free-living or parasitic ways of life. Species estimates shown here are based on numbers described scientifically; much larger estimates have been calculated based on various means of prediction, and these can vary wildly. For instance, around 25,000–27,000 species of nematodes have been described, while published estimates of the total number of nematode species include 10,000–20,000; 500,000; 10 million; and 100 million. Using patterns within the taxonomic hierarchy, the total number of animal species—including those not yet described—was calculated to be about 7.77 million in 2011.[a] 3,000–6,500 4,000–25,000 Evolutionary origin Evidence of animals is found as long ago as the Cryogenian period. 24-Isopropylcholestane (24-ipc) has been found in rocks from roughly 650 million years ago; it is only produced by sponges and pelagophyte algae. Its likely origin is from sponges based on molecular clock estimates for the origin of 24-ipc production in both groups. Analyses of pelagophyte algae consistently recover a Phanerozoic origin, while analyses of sponges recover a Neoproterozoic origin, consistent with the appearance of 24-ipc in the fossil record. The first body fossils of animals appear in the Ediacaran, represented by forms such as Charnia and Spriggina. It had long been doubted whether these fossils truly represented animals, but the discovery of the animal lipid cholesterol in fossils of Dickinsonia establishes their nature. Animals are thought to have originated under low-oxygen conditions, suggesting that they were capable of living entirely by anaerobic respiration, but as they became specialised for aerobic metabolism they became fully dependent on oxygen in their environments. Many animal phyla first appear in the fossil record during the Cambrian explosion, starting about 539 million years ago, in beds such as the Burgess Shale. Extant phyla in these rocks include molluscs, brachiopods, onychophorans, tardigrades, arthropods, echinoderms and hemichordates, along with numerous now-extinct forms such as the predatory Anomalocaris. The apparent suddenness of the event may however be an artefact of the fossil record, rather than showing that all these animals appeared simultaneously. That view is supported by the discovery of Auroralumina attenboroughii, the earliest known Ediacaran crown-group cnidarian (557–562 mya, some 20 million years before the Cambrian explosion) from Charnwood Forest, England. It is thought to be one of the earliest predators, catching small prey with its nematocysts as modern cnidarians do. Some palaeontologists have suggested that animals appeared much earlier than the Cambrian explosion, possibly as early as 1 billion years ago. Early fossils that might represent animals appear for example in the 665-million-year-old rocks of the Trezona Formation of South Australia. These fossils are interpreted as most probably being early sponges. Trace fossils such as tracks and burrows found in the Tonian period (from 1 gya) may indicate the presence of triploblastic worm-like animals, roughly as large (about 5 mm wide) and complex as earthworms. However, similar tracks are produced by the giant single-celled protist Gromia sphaerica, so the Tonian trace fossils may not indicate early animal evolution. Around the same time, the layered mats of microorganisms called stromatolites decreased in diversity, perhaps due to grazing by newly evolved animals. Objects such as sediment-filled tubes that resemble trace fossils of the burrows of wormlike animals have been found in 1.2 gya rocks in North America, in 1.5 gya rocks in Australia and North America, and in 1.7 gya rocks in Australia. Their interpretation as having an animal origin is disputed, as they might be water-escape or other structures. Phylogeny Animals are monophyletic, meaning they are derived from a common ancestor. Animals are the sister group to the choanoflagellates, with which they form the Choanozoa. Ros-Rocher and colleagues (2021) trace the origins of animals to unicellular ancestors, providing the external phylogeny shown in the cladogram. Uncertainty of relationships is indicated with dashed lines. The animal clade had certainly originated by 650 mya, and may have come into being as much as 800 mya, based on molecular clock evidence for different phyla. Holomycota (inc. fungi) Ichthyosporea Pluriformea Filasterea The relationships at the base of the animal tree have been debated. Other than Ctenophora, the Bilateria and Cnidaria are the only groups with symmetry, and other evidence shows they are closely related. In addition to sponges, Placozoa has no symmetry and was often considered a "missing link" between protists and multicellular animals. The presence of hox genes in Placozoa shows that they were once more complex. The Porifera (sponges) have long been assumed to be sister to the rest of the animals, but there is evidence that the Ctenophora may be in that position. Molecular phylogenetics has supported both the sponge-sister and ctenophore-sister hypotheses. In 2017, Roberto Feuda and colleagues, using amino acid differences, presented both, with the following cladogram for the sponge-sister view that they supported (their ctenophore-sister tree simply interchanging the places of ctenophores and sponges): Porifera Ctenophora Placozoa Cnidaria Bilateria Conversely, a 2023 study by Darrin Schultz and colleagues uses ancient gene linkages to construct the following ctenophore-sister phylogeny: Ctenophora Porifera Placozoa Cnidaria Bilateria Sponges are physically very distinct from other animals, and were long thought to have diverged first, representing the oldest animal phylum and forming a sister clade to all other animals. Despite their morphological dissimilarity with all other animals, genetic evidence suggests sponges may be more closely related to other animals than the comb jellies are. Sponges lack the complex organisation found in most other animal phyla; their cells are differentiated, but in most cases not organised into distinct tissues, unlike all other animals. They typically feed by drawing in water through pores, filtering out small particles of food. The Ctenophora and Cnidaria are radially symmetric and have digestive chambers with a single opening, which serves as both mouth and anus. Animals in both phyla have distinct tissues, but these are not organised into discrete organs. They are diploblastic, having only two main germ layers, ectoderm and endoderm. The tiny placozoans have no permanent digestive chamber and no symmetry; they superficially resemble amoebae. Their phylogeny is poorly defined, and under active research. The remaining animals, the great majority—comprising some 29 phyla and over a million species—form the Bilateria clade, which have a bilaterally symmetric body plan. The Bilateria are triploblastic, with three well-developed germ layers, and their tissues form distinct organs. The digestive chamber has two openings, a mouth and an anus, and in the Nephrozoa there is an internal body cavity, a coelom or pseudocoelom. These animals have a head end (anterior) and a tail end (posterior), a back (dorsal) surface and a belly (ventral) surface, and a left and a right side. A modern consensus phylogenetic tree for the Bilateria is shown below. Xenacoelomorpha Ambulacraria Chordata Ecdysozoa Spiralia Having a front end means that this part of the body encounters stimuli, such as food, favouring cephalisation, the development of a head with sense organs and a mouth. Many bilaterians have a combination of circular muscles that constrict the body, making it longer, and an opposing set of longitudinal muscles, that shorten the body; these enable soft-bodied animals with a hydrostatic skeleton to move by peristalsis. They also have a gut that extends through the basically cylindrical body from mouth to anus. Many bilaterian phyla have primary larvae which swim with cilia and have an apical organ containing sensory cells. However, over evolutionary time, descendant spaces have evolved which have lost one or more of each of these characteristics. For example, adult echinoderms are radially symmetric (unlike their larvae), while some parasitic worms have extremely simplified body structures. Genetic studies have considerably changed zoologists' understanding of the relationships within the Bilateria. Most appear to belong to two major lineages, the protostomes and the deuterostomes. It is often suggested that the basalmost bilaterians are the Xenacoelomorpha, with all other bilaterians belonging to the subclade Nephrozoa. However, this suggestion has been contested, with other studies finding that xenacoelomorphs are more closely related to Ambulacraria than to other bilaterians. Protostomes and deuterostomes differ in several ways. Early in development, deuterostome embryos undergo radial cleavage during cell division, while many protostomes (the Spiralia) undergo spiral cleavage. Animals from both groups possess a complete digestive tract, but in protostomes the first opening of the embryonic gut develops into the mouth, and the anus forms secondarily. In deuterostomes, the anus forms first while the mouth develops secondarily. Most protostomes have schizocoelous development, where cells simply fill in the interior of the gastrula to form the mesoderm. In deuterostomes, the mesoderm forms by enterocoelic pouching, through invagination of the endoderm. The main deuterostome taxa are the Ambulacraria and the Chordata. Ambulacraria are exclusively marine and include acorn worms, starfish, sea urchins, and sea cucumbers. The chordates are dominated by the vertebrates (animals with backbones), which consist of fishes, amphibians, reptiles, birds, and mammals. The protostomes include the Ecdysozoa, named after their shared trait of ecdysis, growth by moulting, Among the largest ecdysozoan phyla are the arthropods and the nematodes. The rest of the protostomes are in the Spiralia, named for their pattern of developing by spiral cleavage in the early embryo. Major spiralian phyla include the annelids and molluscs. History of classification In the classical era, Aristotle divided animals,[d] based on his own observations, into those with blood (roughly, the vertebrates) and those without. The animals were then arranged on a scale from man (with blood, two legs, rational soul) down through the live-bearing tetrapods (with blood, four legs, sensitive soul) and other groups such as crustaceans (no blood, many legs, sensitive soul) down to spontaneously generating creatures like sponges (no blood, no legs, vegetable soul). Aristotle was uncertain whether sponges were animals, which in his system ought to have sensation, appetite, and locomotion, or plants, which did not: he knew that sponges could sense touch and would contract if about to be pulled off their rocks, but that they were rooted like plants and never moved about. In 1758, Carl Linnaeus created the first hierarchical classification in his Systema Naturae. In his original scheme, the animals were one of three kingdoms, divided into the classes of Vermes, Insecta, Pisces, Amphibia, Aves, and Mammalia. Since then, the last four have all been subsumed into a single phylum, the Chordata, while his Insecta (which included the crustaceans and arachnids) and Vermes have been renamed or broken up. The process was begun in 1793 by Jean-Baptiste de Lamarck, who called the Vermes une espèce de chaos ('a chaotic mess')[e] and split the group into three new phyla: worms, echinoderms, and polyps (which contained corals and jellyfish). By 1809, in his Philosophie Zoologique, Lamarck had created nine phyla apart from vertebrates (where he still had four phyla: mammals, birds, reptiles, and fish) and molluscs, namely cirripedes, annelids, crustaceans, arachnids, insects, worms, radiates, polyps, and infusorians. In his 1817 Le Règne Animal, Georges Cuvier used comparative anatomy to group the animals into four embranchements ('branches' with different body plans, roughly corresponding to phyla), namely vertebrates, molluscs, articulated animals (arthropods and annelids), and zoophytes (radiata) (echinoderms, cnidaria and other forms). This division into four was followed by the embryologist Karl Ernst von Baer in 1828, the zoologist Louis Agassiz in 1857, and the comparative anatomist Richard Owen in 1860. In 1874, Ernst Haeckel divided the animal kingdom into two subkingdoms: Metazoa (multicellular animals, with five phyla: coelenterates, echinoderms, articulates, molluscs, and vertebrates) and Protozoa (single-celled animals), including a sixth animal phylum, sponges. The protozoa were later moved to the former kingdom Protista, leaving only the Metazoa as a synonym of Animalia. In human culture The human population exploits a large number of other animal species for food, both of domesticated livestock species in animal husbandry and, mainly at sea, by hunting wild species. Marine fish of many species are caught commercially for food. A smaller number of species are farmed commercially. Humans and their livestock make up more than 90% of the biomass of all terrestrial vertebrates, and almost as much as all insects combined. Invertebrates including cephalopods, crustaceans, insects—principally bees and silkworms—and bivalve or gastropod molluscs are hunted or farmed for food, fibres. Chickens, cattle, sheep, pigs, and other animals are raised as livestock for meat across the world. Animal fibres such as wool and silk are used to make textiles, while animal sinews have been used as lashings and bindings, and leather is widely used to make shoes and other items. Animals have been hunted and farmed for their fur to make items such as coats and hats. Dyestuffs including carmine (cochineal), shellac, and kermes have been made from the bodies of insects. Working animals including cattle and horses have been used for work and transport from the first days of agriculture. Animals such as the fruit fly Drosophila melanogaster serve a major role in science as experimental models. Animals have been used to create vaccines since their discovery in the 18th century. Some medicines such as the cancer drug trabectedin are based on toxins or other molecules of animal origin. People have used hunting dogs to help chase down and retrieve animals, and birds of prey to catch birds and mammals, while tethered cormorants have been used to catch fish. Poison dart frogs have been used to poison the tips of blowpipe darts. A wide variety of animals are kept as pets, from invertebrates such as tarantulas, octopuses, and praying mantises, reptiles such as snakes and chameleons, and birds including canaries, parakeets, and parrots all finding a place. However, the most kept pet species are mammals, namely dogs, cats, and rabbits. There is a tension between the role of animals as companions to humans, and their existence as individuals with rights of their own. A wide variety of terrestrial and aquatic animals are hunted for sport. The signs of the Western and Chinese zodiacs are based on animals. In China and Japan, the butterfly has been seen as the personification of a person's soul, and in classical representation the butterfly is also the symbol of the soul. Animals have been the subjects of art from the earliest times, both historical, as in ancient Egypt, and prehistoric, as in the cave paintings at Lascaux. Major animal paintings include Albrecht Dürer's 1515 The Rhinoceros, and George Stubbs's c. 1762 horse portrait Whistlejacket. Insects, birds and mammals play roles in literature and film, such as in giant bug movies. Animals including insects and mammals feature in mythology and religion. The scarab beetle was sacred in ancient Egypt, and the cow is sacred in Hinduism. Among other mammals, deer, horses, lions, bats, bears, and wolves are the subjects of myths and worship. See also Notes References External links |
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Contents New Horizons New Horizons is an interplanetary space probe launched as a part of NASA's New Frontiers program. It was launched in 2006, becoming the first spacecraft to perform a flyby study of the Pluto system in 2015. A secondary mission contained a flyby and study of one or more other Kuiper belt objects (KBOs) in the decade to follow, where it flew past 486958 Arrokoth in 2019. It was the first space probe to ever take high-resolution photographs of Pluto, in 2015. It was engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institute (SwRI), with a team led by Alan Stern. New Horizons is the fifth space probe to achieve the escape velocity needed to leave the Solar System. On January 19, 2006, New Horizons was launched from Cape Canaveral Space Force Station by an Atlas V rocket directly into an Earth-and-solar escape trajectory with a speed of about 16.26 km/s (10.10 mi/s; 58,500 km/h; 36,400 mph). It was the fastest (average speed with respect to Earth) human-made object ever launched from Earth. It is not the fastest speed recorded for a spacecraft, which, as of 2023, is that of the Parker Solar Probe. After a brief encounter with asteroid 132524 APL, New Horizons proceeded to Jupiter, making its closest approach on February 28, 2007, at a distance of 2.3 million kilometers (1.4 million miles). The Jupiter flyby provided a gravity assist that increased New Horizons' speed; the flyby also enabled a general test of New Horizons' scientific capabilities, returning data about the planet's atmosphere, moons, and magnetosphere. Most of the post-Jupiter voyage was spent in hibernation mode to preserve onboard systems, except for brief annual checkouts. On December 6, 2014, New Horizons was brought back online for the Pluto encounter, and instrument check-out began. On January 15, 2015, the spacecraft began its approach phase to Pluto. On July 14, 2015, at 11:49 UTC, it flew 12,500 km (7,800 mi) above the surface of Pluto, which at the time was 34 AU from the Sun, making it the first spacecraft to explore the dwarf planet. In August 2016, New Horizons was reported to have traveled at speeds of more than 84,000 km/h (52,000 mph). On October 25, 2016, at 21:48 UTC, the last recorded data from the Pluto flyby was received from New Horizons. Having completed its flyby of Pluto, New Horizons then maneuvered for a flyby of Kuiper belt object 486958 Arrokoth (then nicknamed Ultima Thule), which occurred on January 1, 2019, when it was 43.4 AU (6.49 billion km; 4.03 billion mi) from the Sun. In August 2018, NASA cited results by Alice on New Horizons to confirm the existence of a "hydrogen wall" at the outer edges of the Solar System. This "wall" was first detected in 1992 by the two Voyager spacecraft. New Horizons is traveling through the Kuiper belt; it is 62.23 AU (9.31 billion km; 5.78 billion mi) from Earth and 62.71 AU (9.38 billion km; 5.83 billion mi) from the Sun as of September 2025. NASA has announced its plan to extend operations for New Horizons until the spacecraft exits the Kuiper belt, which is expected to occur in either 2028 or 2029. The White House's proposed budget for FY2026 would have cut funding for New Horizons, however the continued funding of the mission was heavily debated in the United States Congress and a final budget of 24.44 billion guaranteed the mission continuation. History In August 1992, JPL scientist Robert Staehle called Pluto discoverer Clyde Tombaugh, requesting permission to visit his planet. "I told him he was welcome to it," Tombaugh later remembered, "though he's got to go one long, cold trip." The call eventually led to a series of proposed Pluto missions leading up to New Horizons. Stamatios "Tom" Krimigis, head of the Applied Physics Laboratory's space division, one of many entrants in the New Frontiers Program competition, formed the New Horizons team with Alan Stern in December 2000. Appointed as the project's principal investigator, Stern was described by Krimigis as "the personification of the Pluto mission". New Horizons was based largely on Stern's work since Pluto 350 and involved most of the team from Pluto Kuiper Express. The New Horizons proposal was one of five that were officially submitted to NASA. It was later selected as one of two finalists to be subject to a three-month concept study in June 2001. The other finalist, POSSE (Pluto and Outer Solar System Explorer), was a separate but similar Pluto mission concept by the University of Colorado Boulder, led by principal investigator Larry W. Esposito, and supported by the JPL, Lockheed Martin and the University of California. However, the APL, in addition to being supported by Pluto Kuiper Express developers at the Goddard Space Flight Center and Stanford University were at an advantage; they had recently developed NEAR Shoemaker for NASA, which had successfully entered orbit around 433 Eros earlier that year, and would later land on the asteroid to scientific and engineering fanfare. In November 2001, New Horizons was officially selected for funding as part of the New Frontiers program. However, the new NASA Administrator appointed by the Bush administration, Sean O'Keefe, was not supportive of New Horizons and effectively canceled it by not including it in NASA's budget for 2003. NASA's Associate Administrator for the Science Mission Directorate, Ed Weiler, prompted Stern to lobby for the funding of New Horizons in hopes of the mission appearing in the Planetary Science Decadal Survey, a prioritized "wish list", compiled by the United States National Research Council, that reflects the opinions of the scientific community. After an intense campaign to gain support for New Horizons, the Planetary Science Decadal Survey of 2003–2013 was published in the summer of 2002. New Horizons topped the list of projects considered the highest priority among the scientific community in the medium-size category; ahead of missions to the Moon, and even Jupiter. Weiler stated that it was a result that "[his] administration was not going to fight". Funding for the mission was finally secured following the publication of the report. Stern's team was finally able to start building the spacecraft and its instruments, with a planned launch in January 2006 and arrival at Pluto in 2015. Alice Bowman became Mission Operations Manager (MOM). Mission profile New Horizons is the first mission in NASA's New Frontiers mission category, larger and more expensive than the Discovery missions but smaller than the missions of the Flagship Program. The cost of the mission, including spacecraft and instrument development, launch vehicle, mission operations, data analysis, and education/public outreach, is approximately $700 million over 15 years (2001–2016). The spacecraft was built primarily by Southwest Research Institute (SwRI) and the Johns Hopkins Applied Physics Laboratory. The mission's principal investigator is Alan Stern of the Southwest Research Institute (formerly NASA Associate Administrator). After separation from the launch vehicle, overall control was taken by Mission Operations Center (MOC) at the Applied Physics Laboratory in Howard County, Maryland. The science instruments are operated at Clyde Tombaugh Science Operations Center (T-SOC) in Boulder, Colorado. Navigation is performed at various contractor facilities, whereas the navigational positional data and related celestial reference frames are provided by the Naval Observatory Flagstaff Station through Headquarters NASA and JPL. KinetX is the lead on the New Horizons navigation team and is responsible for planning trajectory adjustments as the spacecraft speeds toward the outer Solar System. Coincidentally the Naval Observatory Flagstaff Station was where the photographic plates were taken for the discovery of Pluto's moon Charon. The Naval Observatory itself is not far from the Lowell Observatory where Pluto was discovered. New Horizons was originally planned as a voyage to the only unexplored planet in the Solar System. When the spacecraft was launched, Pluto was still classified as a planet, later to be reclassified as a dwarf planet by the International Astronomical Union (IAU). Some members of the New Horizons team, including Alan Stern, disagree with the IAU definition and still describe Pluto as the ninth planet. Pluto's satellites Nix and Hydra also have a connection with the spacecraft: the first letters of their names (N and H) are the initials of New Horizons. The moons' discoverers chose these names for this reason, plus Nix and Hydra's relationship to the mythological Pluto. In addition to the science equipment, there are nine cultural artifacts traveling with the spacecraft. These include a collection of 434,738 names stored on a compact disc, a collection of images of New Horizons project personnel on another CD, a piece of Scaled Composites's SpaceShipOne, a "Not Yet Explored" USPS stamp, and two copies of the Flag of the United States. About 30 grams (1 oz) of Clyde Tombaugh's ashes are aboard the spacecraft, to commemorate his discovery of Pluto in 1930. A Florida state quarter coin, whose design commemorates human exploration, is included, officially as a trim weight, as is a Maryland state quarter to honor the probe's builders. One of the science packages (a dust counter) is named after Venetia Burney, who, as a child, suggested the name "Pluto" after its discovery. Goal The goal of the mission is to understand the formation of the Plutonian system, the Kuiper belt, and the transformation of the early Solar System. The spacecraft collected data on the atmospheres, surfaces, interiors, and environments of Pluto and its moons. It will also study other objects in the Kuiper belt. "By way of comparison, New Horizons gathered 5,000 times as much data at Pluto as Mariner did at the Red Planet." Some of the questions the mission attempts to answer are: What is Pluto's atmosphere made of and how does it behave? What does its surface look like? Are there large geological structures? How do solar wind particles interact with Pluto's atmosphere? Specifically, the mission's science objectives are to: Design and construction The spacecraft is comparable in size and general shape to a grand piano and has been compared to a piano glued to a cocktail bar-sized satellite dish. As a point of departure, the team took inspiration from the Ulysses spacecraft, which also carried a radioisotope thermoelectric generator (RTG) and dish on a box-in-box structure through the outer Solar System. Many subsystems and components have flight heritage from APL's CONTOUR spacecraft, which in turn had heritage from APL's TIMED spacecraft. New Horizons' body forms a triangle, almost 0.76 m (2.5 ft) thick. (The Pioneers have hexagonal bodies, whereas the Voyagers have decagonal bodies, Galileo an octagonal prism body, and Cassini–Huygens a dodecagonal prism body.) A 7075 aluminium alloy tube forms the main structural column, between the launch vehicle adapter ring at the "rear", and the 2.1 m (6 ft 11 in) radio dish antenna affixed to the "front" flat side. The titanium fuel tank is in this tube. The RTG attaches with a 4-sided titanium mount resembling a gray pyramid or stepstool. Titanium provides strength and thermal isolation. The rest of the triangle is primarily sandwich panels of thin aluminum face sheet (less than 1⁄64 in or 0.40 mm) bonded to aluminum honeycomb core. The structure is larger than strictly necessary, with empty space inside. The structure is designed to act as shielding, reducing electronics errors caused by radiation from the RTG. Also, the mass distribution required for a spinning spacecraft demands a wider triangle. The interior structure is painted black to equalize temperature by radiative heat transfer. Overall, the spacecraft is thoroughly blanketed to retain heat. Unlike the Pioneers and Voyagers, the radio dish is also enclosed in blankets that extend to the body. The heat from the RTG adds warmth to the spacecraft while it is in the outer Solar System. While in the inner Solar System, the spacecraft must prevent overheating, hence electronic activity is limited, power is diverted to shunts with attached radiators, and louvers are opened to radiate excess heat. While the spacecraft is cruising inactively in the cold outer Solar System, the louvers are closed, and the shunt regulator reroutes power to electric heaters. New Horizons has both spin-stabilized (cruise) and three-axis stabilized (science) modes controlled entirely with hydrazine monopropellant. Additional post launch delta-v of over 290 m/s (1,000 km/h; 650 mph) is provided by a 77 kg (170 lb) internal tank. Helium is used as a pressurant, with an elastomeric diaphragm assisting expulsion. The spacecraft's on-orbit mass including fuel is over 470 kg (1,040 lb) on the Jupiter flyby trajectory, but would have been only 445 kg (981 lb) for the backup direct flight option to Pluto. Significantly, had the backup option been taken, this would have meant less fuel for later Kuiper belt operations. There are 16 thrusters on New Horizons: four 4.4 N (1.0 lbf) and twelve 0.9 N (0.2 lbf) plumbed into redundant branches. The larger thrusters are used primarily for trajectory corrections, and the small ones (previously used on Cassini and the Voyager spacecraft) are used primarily for attitude control and spinup/spindown maneuvers. Two star cameras are used to measure the spacecraft attitude. They are mounted on the face of the spacecraft and provide attitude information while in spin-stabilized or 3-axis mode. In between the time of star camera readings, spacecraft orientation is provided by dual redundant miniature inertial measurement units. Each unit contains three solid-state gyroscopes and three accelerometers. Two Adcole Sun sensors provide attitude determination. One detects the angle to the Sun, whereas the other measures spin rate and clocking. A cylindrical radioisotope thermoelectric generator (RTG) protrudes in the plane of the triangle from one vertex of the triangle. The RTG provided 245.7 W of power at launch, and was predicted to drop approximately 3.5 W every year, decaying to 202 W by the time of its encounter with the Plutonian system in 2015 and will decay too far to power the transmitters in the 2030s. There are no onboard batteries since RTG output is predictable, and load transients are handled by a capacitor bank and fast circuit breakers. As of January 2019, the power output of the RTG is about 190 W. The RTG, model "GPHS-RTG", was originally a spare from the Cassini mission. The RTG contains 9.75 kg (21.5 lb) of plutonium-238 oxide pellets. Each pellet is clad in iridium, then encased in a graphite shell. It was developed by the U.S. Department of Energy at the Materials and Fuels Complex, a part of the Idaho National Laboratory. The original RTG design called for 10.9 kg (24 lb) of plutonium, but a unit less powerful than the original design goal was produced because of delays at the United States Department of Energy, including security activities, that delayed plutonium production. The mission parameters and observation sequence had to be modified for the reduced wattage; still, not all instruments can operate simultaneously. The Department of Energy transferred the space battery program from Ohio to Argonne in 2002 because of security concerns. The amount of radioactive plutonium in the RTG is about one-third the amount on board the Cassini–Huygens probe when it launched in 1997. The Cassini launch had been protested by multiple organizations, due to the risk of such a large amount of plutonium being released into the atmosphere in case of an accident. The United States Department of Energy estimated the chances of a launch accident that would release radiation into the atmosphere at 1 in 350, and monitored the launch because of the inclusion of an RTG on board. It was estimated that a worst-case scenario of total dispersal of on-board plutonium would spread the equivalent radiation of 80% the average annual dosage in North America from background radiation over an area with a radius of 105 km (65 mi). The spacecraft carries two computer systems: the Command and Data Handling system and the Guidance and Control processor. Each of the two systems is duplicated for redundancy, for a total of four computers. The processor used for its flight computers is the Mongoose-V, a 12 MHz radiation-hardened version of the MIPS R3000 CPU. Multiple redundant clocks and timing routines are implemented in hardware and software to help prevent faults and downtime. To conserve heat and mass, spacecraft and instrument electronics are housed together in IEMs (integrated electronics modules). There are two redundant IEMs. Including other functions such as instrument and radio electronics, each IEM contains 9 boards. The software of the probe runs on Nucleus RTOS operating system. There have been two "safing" events, that sent the spacecraft into safe mode: Communication with the spacecraft is via X band. The craft had a communication rate of 38 kbit/s at Jupiter; at Pluto's distance, a rate of approximately 1 kbit/s per transmitter was expected. Besides the low data rate, Pluto's distance also causes a latency of about 4.5 hours (one-way). The 70 m (230 ft) NASA Deep Space Network (DSN) dishes are used to relay commands once the spacecraft is beyond Jupiter. The spacecraft uses dual modular redundancy transmitters and receivers, and either right- or left-hand circular polarization. The downlink signal is amplified by dual redundant 12-watt traveling-wave tube amplifiers (TWTAs) mounted on the body under the dish. The receivers are low-power designs. The system can be controlled to power both TWTAs at the same time, and transmit a dual-polarized downlink signal to the DSN that nearly doubles the downlink rate. DSN tests early in the mission with this dual polarization combining technique were successful, and the capability was declared to be operational (when the spacecraft power budget permits both TWTAs to be powered). In addition to the high-gain antenna, there are two backup low-gain antennas and a medium-gain dish. The high-gain dish has a Cassegrain reflector layout, composite construction, of 2.1-meter (7 ft) diameter providing over 42 dBi of gain and a half-power beam width of about a degree. The prime-focus medium-gain antenna, with a 0.3-meter (1 ft) aperture and 10° half-power beam width, is mounted to the forward-facing side of the high-gain antenna's secondary reflector. The forward low-gain antenna is stacked atop the feed of the medium-gain antenna. The aft low-gain antenna is mounted within the launch adapter at the rear of the spacecraft. This antenna was used only for early mission phases near Earth, just after launch and for emergencies if the spacecraft had lost attitude control. New Horizons recorded scientific instrument data to its solid-state memory buffer at each encounter, then transmitted the data to Earth. Data storage is done on two low-power solid-state recorders (one primary, one backup) holding up to 8 gigabytes each. Because of the extreme distance from Pluto and the Kuiper belt, only one buffer load at those encounters can be saved. This is because New Horizons would require approximately 16 months after leaving the vicinity of Pluto to transmit the buffer load back to Earth. At Pluto's distance, radio signals from the space probe back to Earth took four hours and 25 minutes to traverse 4.7 billion km of space. Part of the reason for the delay between the gathering of and transmission of data is that all of the New Horizons instrumentation is body-mounted. In order for the cameras to record data, the entire probe must turn, and the one-degree-wide beam of the high-gain antenna was not pointing toward Earth. Previous spacecraft, such as the Voyager program probes, had a rotatable instrumentation platform (a "scan platform") that could take measurements from virtually any angle without losing radio contact with Earth. New Horizons was mechanically simplified to save weight, shorten the schedule, and improve reliability during its 15-year designed lifetime. Instruments New Horizons carries seven instruments: three optical instruments, two plasma instruments, a dust sensor and a radio science receiver/radiometer. The instruments are to be used to investigate the global geology, surface composition, surface temperature, atmospheric pressure, atmospheric temperature and escape rate of Pluto and its moons. The rated power is 21 watts, though not all instruments operate simultaneously. In addition, New Horizons has an Ultrastable Oscillator subsystem, which may be used to study and test the Pioneer anomaly towards the end of the spacecraft's life. The Long-Range Reconnaissance Imager (LORRI) is a long-focal-length imager designed for high resolution and responsivity at visible wavelengths. The instrument is equipped with a 1024×1024 pixel by 12-bits-per-pixel monochromatic CCD imager giving a resolution of 5 μrad (~1 arcsec). The CCD is chilled far below freezing by a passive radiator on the antisolar face of the spacecraft. This temperature differential requires insulation and isolation from the rest of the structure. The 208.3 mm (8.20 in) aperture Ritchey–Chretien mirrors and metering structure are made of silicon carbide to boost stiffness, reduce weight and prevent warping at low temperatures. The optical elements sit in a composite light shield and mount with titanium and fiberglass for thermal isolation. Overall mass is 8.6 kg (19 lb), with the optical tube assembly (OTA) weighing about 5.6 kg (12 lb), for one of the largest silicon-carbide telescopes flown at the time (now surpassed by Herschel). For viewing on public web sites the 12-bit per pixel LORRI images are converted to 8-bit per pixel JPEG images. These public images do not contain the full dynamic range of brightness information available from the raw LORRI images files. Solar Wind Around Pluto (SWAP) is a toroidal electrostatic analyzer and retarding potential analyzer (RPA), that makes up one of the two instruments comprising New Horizons' Plasma and high-energy particle spectrometer suite (PAM), the other being PEPSSI. SWAP measures particles of up to 6.5 keV and, because of the tenuous solar wind at Pluto's distance, the instrument is designed with the largest aperture of any such instrument ever flown. Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) is a time of flight ion and electron sensor that makes up one of the two instruments comprising New Horizons' plasma and high-energy particle spectrometer suite (PAM), the other being SWAP. Unlike SWAP, which measures particles of up to 6.5 keV, PEPSSI goes up to 1 MeV. The PEPSSI sensor has been designed to measure the mass, energy and distribution of charged particles around Pluto, and is also able to differentiate between protons, electrons, and other heavy ions. Alice is an ultraviolet imaging spectrometer that is one of two photographic instruments comprising New Horizons' Pluto Exploration Remote Sensing Investigation (PERSI); the other being the Ralph telescope. It resolves 1,024 wavelength bands in the far and extreme ultraviolet (from 50–180 nm), over 32 view fields. Its goal is to determine the composition of Pluto's atmosphere. This Alice instrument is derived from another Alice aboard ESA's Rosetta spacecraft. The instrument has a mass of 4.4 kg and draws 4.4 watts of power. Its primary role is to determine the relative concentrations of various elements and isotopes in Pluto's atmosphere. In August 2018, NASA confirmed, based on results by Alice on the New Horizons spacecraft, a "hydrogen wall" at the outer edges of the Solar System that was first detected in 1992 by the two Voyager spacecraft. The Ralph telescope, 75 mm in aperture, is one of two photographic instruments that make up New Horizons' Pluto Exploration Remote Sensing Investigation (PERSI), with the other being the Alice instrument. Ralph has two separate channels: MVIC (Multispectral Visible Imaging Camera), a visible-light CCD imager with broadband and color channels; and LEISA (Linear Etalon Imaging Spectral Array), a near-infrared imaging spectrometer. LEISA is derived from a similar instrument on the Earth Observing-1 spacecraft. Ralph was named after Alice's husband on The Honeymooners, and was designed after Alice. On June 23, 2017, NASA announced that it has renamed the LEISA instrument to the "Lisa Hardaway Infrared Mapping Spectrometer" in honor of Lisa Hardaway, the Ralph program manager at Ball Aerospace, who died in January 2017 at age 50. The Venetia Burney Student Dust Counter (VBSDC), built by students at the University of Colorado Boulder, is operating periodically to make dust measurements. It consists of a detector panel, about 460 mm × 300 mm (18 in × 12 in), mounted on the anti-solar face of the spacecraft (the ram direction), and an electronics box within the spacecraft. The detector contains fourteen polyvinylidene difluoride (PVDF) panels, twelve science and two reference, which generate voltage when impacted. Effective collecting area is 0.125 m2 (1.35 sq ft). No dust counter has operated past the orbit of Uranus; models of dust in the outer Solar System, especially the Kuiper belt, are speculative. The VBSDC is always turned on measuring the masses of the interplanetary and interstellar dust particles (in the range of nano- and picograms) as they collide with the PVDF panels mounted on the New Horizons spacecraft. The measured data is expected to greatly contribute to the understanding of the dust spectra of the Solar System. The dust spectra can then be compared with those from observations of other stars, giving new clues as to where Earth-like planets can be found in the universe. The dust counter is named for Venetia Burney, who first suggested the name "Pluto" at the age of 11. A thirteen-minute short film about the VBSDC garnered an Emmy Award for student achievement in 2006. The Radio Science Experiment (REX) used an ultrastable crystal oscillator (essentially a calibrated crystal in a miniature oven) and some additional electronics to conduct radio science investigations using the communications channels. These are small enough to fit on a single card. Because there are two redundant communications subsystems, there are two, identical REX circuit boards. Journey to Pluto On September 24, 2005, the spacecraft arrived at the Kennedy Space Center on board a C-17 Globemaster III for launch preparations. The launch of New Horizons was originally scheduled for January 11, 2006, but was initially delayed until January 17, 2006, to allow for borescope inspections of the Atlas V's kerosene tank. Further delays related to low cloud ceiling conditions downrange, and high winds and technical difficulties—unrelated to the rocket itself—prevented launch for a further two days. The probe finally lifted off from Pad 41 at Cape Canaveral Air Force Station, Florida, directly south of Space Shuttle Launch Complex 39, at 19:00 UTC on January 19, 2006. The Centaur second stage ignited at 19:04:43 UTC and burned for 5 minutes 25 seconds. It reignited at 19:32 UTC and burned for 9 minutes 47 seconds. The ATK Star 48B third stage ignited at 19:42:37 UTC and burned for 1 minute 28 seconds. Combined, these burns successfully sent the probe on a solar-escape trajectory at 16.26 kilometers per second (58,536 km/h; 36,373 mph). New Horizons took only nine hours to pass the Moon's orbit. Although there were backup launch opportunities in February 2006 and February 2007, only the first twenty-three days of the 2006 window permitted the Jupiter flyby. Any launch outside that period would have forced the spacecraft to fly a slower trajectory directly to Pluto, delaying its encounter by five to six years. The probe was launched by a Lockheed Martin Atlas V 551 rocket, with a third stage added to increase the heliocentric (escape) speed. This was the first launch of the Atlas V 551 configuration, which uses five solid rocket boosters, and the first Atlas V with a third stage. Previous flights had used zero, two, or three solid boosters, but never five. The vehicle, AV-010, weighed 573,160 kilograms (1,263,600 lb) at lift-off, and had earlier been slightly damaged when Hurricane Wilma swept across Florida on October 24, 2005. One of the solid rocket boosters was hit by a door. The booster was replaced with an identical unit, rather than inspecting and requalifying the original. The launch was dedicated to the memory of launch conductor Daniel Sarokon, who was described by space program officials as one of the most influential people in the history of space travel. On January 28 and 30, 2006, mission controllers guided the probe through its first trajectory-correction maneuver (TCM), which was divided into two parts (TCM-1A and TCM-1B). The total velocity change of these two corrections was about 18 meters per second (65 km/h; 40 mph). TCM-1 was accurate enough to permit the cancellation of TCM-2, the second of three originally scheduled corrections. On March 9, 2006, controllers performed TCM-3, the last of three scheduled course corrections. The engines burned for 76 seconds, adjusting the spacecraft's velocity by about 1.16 m/s (4.2 km/h; 2.6 mph). Further trajectory maneuvers were not needed until September 25, 2007 (seven months after the Jupiter flyby), when the engines were fired for 15 minutes and 37 seconds, changing the spacecraft's velocity by 2.37 m/s (8.5 km/h; 5.3 mph), followed by another TCM, almost three years later on June 30, 2010, that lasted 35.6 seconds, when New Horizons had already reached the halfway point (in time traveled) to Pluto. During the week of February 20, 2006, controllers conducted initial in-flight tests of three onboard science instruments, the Alice ultraviolet imaging spectrometer, the PEPSSI plasma-sensor, and the LORRI long-range visible-spectrum camera. No scientific measurements or images were taken, but instrument electronics, and in the case of Alice, some electromechanical systems were shown to be functioning correctly. On April 7, 2006, the spacecraft passed the orbit of Mars, moving at roughly 21 km/s (76,000 km/h; 47,000 mph) away from the Sun at a solar distance of 243 million kilometers. Because of the need to conserve fuel for possible encounters with Kuiper belt objects subsequent to the Pluto flyby, intentional encounters with objects in the asteroid belt were not planned. After launch, the New Horizons team scanned the spacecraft's trajectory to determine if any asteroids would, by chance, be close enough for observation. In May 2006 it was discovered that New Horizons would pass close to the tiny asteroid 132524 APL on June 13, 2006. Closest approach occurred at 4:05 UTC at a distance of 101,867 km (63,297 mi) (around one quarter of the average Earth-Moon distance). The asteroid was imaged by Ralph (use of LORRI was not possible because of proximity to the Sun), which gave the team a chance to test Ralph's capabilities, and make observations of the asteroid's composition as well as light and phase curves. The asteroid was estimated to be 2.5 km (1.6 mi) in diameter. The spacecraft successfully tracked the rapidly moving asteroid over June 10–12, 2006. The first images of Pluto from New Horizons were acquired September 21–24, 2006, during a test of LORRI. They were released on November 28, 2006. The images, taken from a distance of approximately 4.2 billion km (2.6 billion mi; 28 AU), confirmed the spacecraft's ability to track distant targets, critical for maneuvering toward Pluto and other Kuiper belt objects. New Horizons used LORRI to take its first photographs of Jupiter on September 4, 2006, from a distance of 291 million kilometers (181 million miles). More detailed exploration of the system began in January 2007 with an infrared image of the moon Callisto, as well as several black-and-white images of Jupiter itself. New Horizons received a gravity assist from Jupiter, with its closest approach at 05:43:40 UTC on February 28, 2007, when it was 2.3 million kilometers (1.4 million miles) from Jupiter. The flyby increased New Horizons' speed by 4 km/s (14,000 km/h; 9,000 mph), accelerating the probe to a velocity of 23 km/s (83,000 km/h; 51,000 mph) relative to the Sun and shortening its voyage to Pluto by three years. The flyby was the center of a four-month intensive observation campaign lasting from January to June. Being an ever-changing scientific target, Jupiter has been observed intermittently since the end of the Galileo mission in September 2003. Knowledge about Jupiter benefited from the fact that New Horizons' instruments were built using the latest technology, especially in the area of cameras, representing a significant improvement over Galileo's cameras, which were modified versions of Voyager cameras, which, in turn, were modified Mariner cameras. The Jupiter encounter also served as a shakedown and dress rehearsal for the Pluto encounter. Because Jupiter is much closer to Earth than Pluto, the communications link can transmit multiple loadings of the memory buffer; thus the mission returned more data from the Jovian system than it was expected to transmit from Pluto. One of the main goals during the Jupiter encounter was observing its atmospheric conditions and analyzing the structure and composition of its clouds. Heat-induced lightning strikes in the polar regions and "waves" that indicate violent storm activity were observed and measured. The Little Red Spot, spanning up to 70% of Earth's diameter, was imaged from up close for the first time. Recording from different angles and illumination conditions, New Horizons took detailed images of Jupiter's faint ring system, discovering debris left over from recent collisions within the rings or from other unexplained phenomena. The search for undiscovered moons within the rings showed no results. Travelling through Jupiter's magnetosphere, New Horizons collected valuable particle readings. "Bubbles" of plasma that are thought to be formed from material ejected by the moon Io were noticed in the magnetotail. The four largest moons of Jupiter were in poor positions for observation; the necessary path of the gravity-assist maneuver meant that New Horizons passed millions of kilometers from any of the Galilean moons. Still, its instruments were intended for small, dim targets, so they were scientifically useful on large, distant moons. Emphasis was put on Jupiter's innermost Galilean moon, Io, whose active volcanoes shoot out tons of material into Jupiter's magnetosphere, and further. Out of eleven observed eruptions, three were seen for the first time. That of Tvashtar reached an altitude of up to 330 km (210 mi). The event gave scientists an unprecedented look into the structure and motion of the rising plume and its subsequent fall back to the surface. Infrared signatures of a further 36 volcanoes were noticed. Callisto's surface was analyzed with LEISA, revealing how lighting and viewing conditions affect infrared spectrum readings of its surface water ice. Minor moons such as Amalthea had their orbit solutions refined. The cameras determined their positions, acting as "reverse optical navigation". After passing Jupiter, New Horizons spent most of its journey towards Pluto in hibernation mode. Redundant components as well as guidance and control systems were shut down to extend their life cycle, decrease operation costs and free the Deep Space Network for other missions. During hibernation mode, the onboard computer monitored the probe's systems and transmitted a signal back to Earth; a "green" code if everything was functioning as expected or a "red" code if mission control's assistance was needed. The probe was activated for about two months a year so that the instruments could be calibrated and the systems checked. The first hibernation mode cycle started on June 28, 2007, the second cycle began on December 16, 2008, the third cycle on August 27, 2009, and the fourth cycle on August 29, 2014, after a 10-week test. New Horizons crossed the orbit of Saturn on June 8, 2008, and Uranus on March 18, 2011. After astronomers announced the discovery of two new moons in the Pluto system, Kerberos and Styx, mission planners started contemplating the possibility of the probe running into unseen debris and dust left over from ancient collisions between the moons. A study based on 18 months of computer simulations, Earth-based telescope observations and occultations of the Pluto system revealed that the possibility of a catastrophic collision with debris or dust was less than 0.3% on the probe's scheduled course. If the hazard increased, New Horizons could have used one of two possible contingency plans, the so-called SHBOTs (Safe Haven by Other Trajectories). Either the probe could have continued on its present trajectory with the antenna facing the incoming particles so the more vital systems would be protected, or it could have positioned its antenna to make a course correction that would take it just 3,000 km (1,900 mi) from the surface of Pluto where it was expected that the atmospheric drag would have cleaned the surrounding space of possible debris. While in hibernation mode in July 2012, New Horizons started gathering scientific data with SWAP, PEPSSI and VBSDC. Although it was originally planned to activate just the VBSDC, other instruments were powered on in order to collect valuable heliospheric data. Before activating the other two instruments, ground tests were conducted to make sure that the expanded data gathering in this phase of the mission would not limit available energy, memory and fuel in the future and that all systems were functioning during the flyby. The first set of data was transmitted in January 2013 during a three-week activation from hibernation. The command and data handling software was updated to address the problem of computer resets. Other possible targets were Neptune trojans. The probe's trajectory to Pluto passed near Neptune's trailing Lagrange point ("L5"), which may host hundreds of bodies in 1:1 resonance. In late 2013, New Horizons passed within 1.2 AU (180 million km; 110 million mi) of the high-inclination L5 Neptune trojan 2011 HM102, which was discovered shortly before by the New Horizons KBO Search task, a survey to find additional distant objects for New Horizons to fly by after its 2015 encounter with Pluto. At that range, 2011 HM102 would have been bright enough to be detectable by New Horizons' LORRI instrument; however, the New Horizons team eventually decided that they would not target 2011 HM102 for observations because the preparations for the Pluto approach took precedence. On August 25, 2014, New Horizons crossed the orbit of Neptune, exactly 25 years after the planet was visited by the Voyager 2 probe. This was the last major planet orbit crossing before the Pluto flyby. At the time, the spacecraft was 3.99 billion km (2.48 billion mi; 26.7 AU) away from Neptune and 4.51 billion km (2.80 billion mi; 30.1 AU) from the Sun. Images from July 1 to 3, 2013, by LORRI were the first by the probe to resolve Pluto and Charon as separate objects. On July 14, 2014, mission controllers performed a sixth trajectory-correction maneuver (TCM) since its launch to enable the craft to reach Pluto. Between July 19–24, 2014, New Horizons' LORRI snapped 12 images of Charon revolving around Pluto, covering almost one full rotation at distances ranging from about 429 to 422 million km (267 to 262 million mi). In August 2014, astronomers made high-precision measurements of Pluto's location and orbit around the Sun using the Atacama Large Millimeter/submillimeter Array (ALMA), an array of radio telescopes located in Chile, to help NASA's New Horizons spacecraft accurately home in on Pluto. On December 6, 2014, mission controllers sent a signal for the craft to "wake up" from its final Pluto-approach hibernation and begin regular operations. The craft's response that it was "awake" reached Earth on December 7, 2014, at 02:30 UTC. Distant-encounter operations at Pluto began on January 4, 2015. On this date, images of the targets with the onboard LORRI imager plus the Ralph telescope were only a few pixels in width. Investigators began taking Pluto images and background starfield images to assist mission navigators in the design of course-correcting engine maneuvers that would precisely modify the trajectory of New Horizons to aim the approach. On February 12, 2015, NASA released new images of Pluto (taken from January 25 to 31) from the approaching probe. New Horizons was more than 203 million km (126 million mi) away from Pluto when it began taking the photos, which showed Pluto and its largest moon, Charon. The exposure time was too short to see Pluto's smaller, much fainter moons. Investigators compiled a series of images of the moons Nix and Hydra taken from January 27 through February 8, 2015, beginning at a range of 201 million km (125 million mi). Pluto and Charon appear as a single overexposed object at the center. The right side image has been processed to remove the background starfield. The other two, even smaller moons—Kerberos and Styx—were seen on photos taken on April 25. Starting on May 11, a hazard search was performed, looking for unknown objects that could be a danger to the spacecraft, such as rings or hitherto undiscovered moons, which could then possibly be avoided by a course change. No rings or additional moons were found. Also in regard to the approach phase during January 2015, on August 21, 2012, the team announced that they would spend mission time attempting long-range observations of the Kuiper belt object temporarily designated VNH0004 (now designated 2011 KW48), when the object was at a distance of 75 million km (0.50 AU; 47 million mi) from New Horizons. The object would be too distant to resolve surface features or take spectroscopy, but it would be able to make observations that cannot be made from Earth, namely a phase curve and a search for small moons. A second object was planned to be observed in June 2015, and a third in September after the flyby; the team hoped to observe a dozen such objects through 2018. On April 15, 2015, Pluto was imaged showing a possible polar cap. On July 4, 2015, New Horizons experienced a software anomaly and went into safe mode, preventing the spacecraft from performing scientific observations until engineers could resolve the problem. On July 5, NASA announced that the problem was determined to be a timing flaw in a command sequence used to prepare the spacecraft for its flyby, and the spacecraft would resume scheduled science operations on July 7. The science observations lost because of the anomaly were judged to have no impact on the mission's main objectives and minimal impact on other objectives. The timing flaw consisted of performing two tasks simultaneously—compressing previously acquired data to release space for more data, and making a second copy of the approach command sequence—that together overloaded the spacecraft's primary computer. After the overload was detected, the spacecraft performed as designed: it switched from the primary computer to the backup computer, entered safe mode, and sent a distress call back to Earth. The distress call was received the afternoon of July 4 and alerted engineers that they needed to contact the spacecraft to get more information and resolve the issue. The resolution was that the problem happened as part of preparations for the approach, and was not expected to happen again because no similar tasks were planned for the remainder of the encounter. Pluto system encounter The closest approach of the New Horizons spacecraft to Pluto occurred at 11:49 UTC on July 14, 2015, at a range of 12,472 km (7,750 mi) from the surface and 13,658 km (8,487 mi) from the center of Pluto. Telemetry data confirming a successful flyby and a healthy spacecraft was received on Earth from the vicinity of the Pluto system on July 15, 2015, 00:52:37 UTC, after 22 hours of planned radio silence due to the spacecraft being pointed towards the Pluto system. Mission managers estimated a one in 10,000 chance that debris could have destroyed the probe or its communication-systems during the flyby, preventing it from sending data to Earth. The first details of the encounter were received the next day, but the download of the complete data set through the 2 kbps data downlink took just over 15 months. The mission's science objectives were grouped in three distinct priorities. The "primary objectives" were required. The "secondary objectives" were expected to be met but were not demanded. The "tertiary objectives" were desired. These objectives could have been skipped in favor of the above objectives. An objective to measure any magnetic field of Pluto was dropped, due to mass and the expense associated with including a magnetometer on the spacecraft. Instead, SWAP and PEPSSI could indirectly detect magnetic fields around Pluto. "The New Horizons flyby of the Pluto system was fully successful, meeting and in many cases exceeding, the Pluto objectives set out for it by NASA and the National Academy of Sciences." On July 14, 2015, at 11:50 UTC, New Horizons made its closest approach to Pluto, passing within 12,500 km (7,800 mi) at a speed of 13.78 km/s (49,600 km/h; 30,800 mph), while also coming as close as 28,800 km (17,900 mi) to Charon. Starting 3.2 days prior, the spacecraft mapped Pluto and Charon with 40 km (25 mi) resolution, enabling coverage of all sides. Close-range imaging was conducted twice daily to monitor for surface changes, such as snowfall or cryovolcanism. During the flyby, LORRI captured images with up to 50 m (160 ft) resolution, MVIC created four-color global maps at 1.6 km (1 mi) resolution, and LEISA obtained near-infrared hyperspectral maps at resolutions ranging from 7 km/px (4.3 mi/px) globally to 0.6 km/px (0.37 mi/px) for selected areas. Meanwhile, Alice characterized the atmosphere, both by emissions of atmospheric molecules (airglow), and by dimming of background stars as they pass behind Pluto (occultation). During and after closest approach, SWAP and PEPSSI sampled the high atmosphere and its effects on the solar wind. VBSDC searched for dust, inferring meteoroid collision rates and any invisible rings. REX performed active and passive radio science. The communications dish on Earth measured the disappearance and reappearance of the radio occultation signal as the probe flew by behind Pluto. The results resolved Pluto's diameter (by their timing) and atmospheric density and composition (by their weakening and strengthening pattern). (Alice can perform similar occultations, using sunlight instead of radio beacons.) Previous missions had the spacecraft transmit through the atmosphere, to Earth ("downlink"). Pluto's mass and mass distribution were evaluated by the gravitational tug on the spacecraft. As the spacecraft speeds up and slows down, the radio signal exhibited a Doppler shift. The Doppler shift was measured by comparison with the ultrastable oscillator in the communications electronics. Reflected sunlight from Charon allowed some imaging observations of the nightside. Backlighting by the Sun gave an opportunity to highlight any rings or atmospheric hazes. REX performed radiometry of the nightside. New Horizons' best spatial resolution of the small satellites is 330 m per pixel (1,080 ft/px) at Nix, 780 m/px (2,560 ft/px) at Hydra, and approximately 1.8 km/px (1.1 mi/px) at Kerberos and Styx. Estimates for the dimensions of these bodies are: Nix at 49.8 × 33.2 × 31.1 km (30.9 × 20.6 × 19.3 mi); Hydra at 50.9 × 36.1 × 30.9 km (31.6 × 22.4 × 19.2 mi); Kerberos at 19 × 10 × 9 km (11.8 × 6.2 × 5.6 mi); and Styx at 16 × 9 × 8 km (9.9 × 5.6 × 5.0 mi). Initial predictions envisioned Kerberos as a relatively large and massive object whose dark surface led to it having a faint reflection. This proved to be wrong as images obtained by New Horizons on July 14 and sent back to Earth in October 2015 revealed that Kerberos was smaller in size, 19 km (12 mi) across with a highly reflective surface suggesting the presence of relatively clean water ice similarly to the rest of Pluto's smaller moons. Post-Pluto events Soon after the Pluto flyby, in July 2015, New Horizons reported that the spacecraft was healthy, its flight path was within the margins, and science data of the Pluto–Charon system had been recorded. The spacecraft's immediate task was to begin returning the 6.25 gigabytes of information collected. The free-space path loss at its distance of 4.5 light-hours (3 billion km or 20 AU or 1.9 billion mi) is approximately 303 dB at 7 GHz. Using the high gain antenna and transmitting at full power, the signal from EIRP is +83 dBm, and at this distance, the signal reaching Earth is −220 dBm. The received signal level (RSL) using one, un-arrayed Deep Space Network antenna with 72 dBi of forward gain equals −148 dBm. Because of the extremely low RSL, it could only transmit data at 1 to 2 kilobits per second. By March 30, 2016, about nine months after the flyby, New Horizons reached the halfway point of transmitting this data. The transfer was completed on October 25, 2016, at 21:48 UTC, when the last piece of data—part of a Pluto–Charon observation sequence by the Ralph/LEISA imager—was received by the Johns Hopkins University Applied Physics Laboratory. As of November 2018, at a distance of 43 AU (6.43 billion km; 4.00 billion mi) from the Sun and 0.4 AU (60 million km; 37 million mi) from 486958 Arrokoth, New Horizons was heading in the direction of the constellation Sagittarius at 14.10 km/s (8.76 mi/s; 2.97 AU/a) relative to the Sun. The brightness of the Sun from the spacecraft was magnitude −18.5. On April 17, 2021, New Horizons reached a distance of 50 AU from the Sun, while remaining fully operational. Mission extension The New Horizons team requested, and received, a mission extension through 2021 to explore additional Kuiper belt objects (KBOs). Funding was secured on July 1, 2016. During this Kuiper Belt Extended Mission (KEM) the spacecraft performed a close fly-by of 486958 Arrokoth and will conduct more distant observations of an additional two dozen objects, and possibly make a fly-by of another KBO.[citation needed] Mission planners searched for one or more additional Kuiper belt objects (KBOs) of the order of 50–100 km (30–60 mi) in diameter as targets for flybys similar to the spacecraft's Plutonian encounter. However, despite the large population of KBOs, many factors limited the number of possible targets. Because the flight path was determined by the Pluto flyby, and the probe only had 33 kg (73 lb) of hydrazine propellant remaining, the object to be visited needed to be within a cone of less than a degree's width extending from Pluto. The target also needed to be within 55 AU, because beyond 55 AU, the communications link becomes too weak, and the RTG power output decays significantly enough to hinder observations. Desirable KBOs are well over 50 km (30 mi) in diameter, neutral in color (to contrast with the reddish Pluto), and, if possible, have a moon that imparts a wobble.[citation needed] In 2011, mission scientists started the New Horizons KBO Search, a dedicated survey for suitable KBOs using ground telescopes. Large ground telescopes with wide-field cameras, notably the twin 6.5-meter Magellan Telescopes in Chile, the 8.2-meter Subaru Observatory in Hawaii and the Canada–France–Hawaii Telescope were used to search for potential targets. By participating in a citizen-science project called Ice Hunters the public helped to scan telescopic images for possible suitable mission candidates. The ground-based search resulted in the discovery of about 143 KBOs of potential interest, but none of these were close enough to the flight path of New Horizons. Only the Hubble Space Telescope was deemed likely to find a suitable target in time for a successful KBO mission. On June 16, 2014, time on Hubble was granted for a search. Hubble has a much greater ability to find suitable KBOs than ground telescopes. The probability that a target for New Horizons would be found was estimated beforehand at about 95%. On October 15, 2014, it was revealed that Hubble's search had uncovered three potential targets, temporarily designated PT1 ("potential target 1"), PT2 and PT3 by the New Horizons team. PT1 was eventually chosen as the target and would be named 486958 Arrokoth. All objects had estimated diameters in the 30–55 km (19–34 mi) range and were too small to be seen by ground telescopes. The targets were at distances from the Sun ranging from 43 to 44 AU, which would put the encounters in the 2018–2019 period. The initial estimated probabilities that these objects were reachable within New Horizons' fuel budget were 100%, 7%, and 97%, respectively. All were members of the "cold" (low-inclination, low-eccentricity) classical Kuiper belt objects, and thus were very different from Pluto. PT1 (given the temporary designation "1110113Y" on the HST web site), the most favorably situated object, had a magnitude of 26.8, is 30–45 km (19–28 mi) in diameter, and was encountered in January 2019. A course change to reach it required about 35% of New Horizons' available trajectory-adjustment fuel supply. A mission to PT3 was in some ways preferable, in that it is brighter and therefore probably larger than PT1, but the greater fuel requirements to reach it would have left less for maneuvering and unforeseen events. Once sufficient orbital information was provided, the Minor Planet Center gave provisional designations to the three target KBOs: 2014 MU69 (PT1' later 486958 Arrokoth), 2014 OS393 (PT2), and 2014 PN70 (PT3). By the fall of 2014, a possible fourth target, 2014 MT69, had been eliminated by follow-up observations. PT2 was out of the running before the Pluto flyby. On August 28, 2015, 486958 Arrokoth (then known as (486958) 2014 MU69 and nicknamed Ultima Thule) (PT1) was chosen as the flyby target. The necessary course adjustment was performed with four engine firings between October 22 and November 4, 2015. The flyby occurred on January 1, 2019, at 00:33 UTC. Aside from its flyby of 486958 Arrokoth, the extended mission for New Horizons calls for the spacecraft to conduct observations of, and look for ring systems around, between 25 and 35 different KBOs. In addition, it will continue to study the gas, dust and plasma composition of the Kuiper belt before the mission extension ends in 2021.[needs update] On November 2, 2015, New Horizons imaged KBO 15810 Arawn with the LORRI instrument from 280 million km away (170 million mi; 1.9 AU). This KBO was again imaged by the LORRI instrument on April 7–8, 2016, from a distance of 111 million km (69 million mi; 0.74 AU). The new images allowed the science team to further refine the location of 15810 Arawn to within 1,000 km (620 mi) and to determine its rotational period of 5.47 hours. In July 2016, the LORRI camera captured some distant images of Quaoar from 2.1 billion km away (1.3 billion mi; 14 AU); the oblique view will complement Earth-based observations to study the object's light-scattering properties. On December 5, 2017, when New Horizons was 40.9 AU from Earth, a calibration image of the Wishing Well cluster marked the most distant image ever taken by a spacecraft (breaking the 27-year record set by Voyager 1's famous Pale Blue Dot). Two hours later, New Horizons surpassed its own record, imaging the Kuiper belt objects 2012 HZ84 and 2012 HE85 from a distance of 0.50 and 0.34 AU, respectively. These were the closest images taken of a Kuiper belt object besides Pluto and Arrokoth as of February 2018[update]. The dwarf planet Haumea was observed from afar by the New Horizons spacecraft in October 2007, January 2017, and May 2020, from distances of 49 AU, 59 AU, and 63 AU, respectively. New Horizons has observed the dwarf planets Eris (2020), Haumea (2007, 2017, 2020), Makemake (2007, 2017), and Quaoar (2016, 2017, 2019), as well as the large KBOs Ixion (2016), Máni (2016, 2017, 2019), and 2014 OE394 (2017, 2018). It also observed Neptune's largest moon Triton (which shares similarities with Pluto and Eris) in 2019. By December 2023, New Horizons had discovered a total of about 100 KBOs, and flown close enough to about 20 of them to capture characteristics such as shape, rotational period, possible moons, and surface composition. In addition, since 2021, Canadian researchers had been able to use machine learning software to speed up identification processes of potential KBO targets for a third flyby, cutting weeks-long efforts to hours-long. Encounter with Arrokoth Science objectives of the flyby included characterizing the geology and morphology of Arrokoth and mapping the surface composition (by searching for ammonia, carbon monoxide, methane, and water ice). Searches will be conducted for orbiting moonlets, a coma, rings and the surrounding environment. Additional objectives include: Arrokoth is the first object to be targeted for a flyby that was discovered after the spacecraft was launched. New Horizons was planned to come within 3,500 km (2,200 mi) of Arrokoth, three times closer than the spacecraft's earlier encounter with Pluto. Images with a resolution of up to 30 m (98 ft) per pixel were expected. The new mission began on October 22, 2015, when New Horizons carried out the first in a series of four initial targeting maneuvers designed to send it towards Arrokoth. The maneuver, which started at approximately 19:50 UTC and used two of the spacecraft's small hydrazine-fueled thrusters, lasted approximately 16 minutes and changed the spacecraft's trajectory by about 10 meters per second (33 ft/s). The remaining three targeting maneuvers took place on October 25, October 28, and November 4, 2015. The craft was brought out of its hibernation at approximately 00:33 UTC SCET on June 5, 2018 (06:12 UTC ERT, Earth-Received Time),[a] in order to prepare for the approach phase. After verifying its health status, the spacecraft transitioned from a spin-stabilized mode to a three-axis-stabilized mode on August 13, 2018. The official approach phase began on August 16, 2018, and continued through December 24, 2018. New Horizons made its first detection of Arrokoth on August 16, 2018, from a distance of 172 million km (107 million mi). At that time, Arrokoth was visible at magnitude 20 against a crowded stellar background in the direction of the constellation Sagittarius. The Core phase began a week before the encounter and continued for two days after the encounter. The spacecraft flew by the object at a speed of 51,500 km/h (32,000 mph; 14.3 km/s) and within 3,500 km (2,200 mi). The majority of the science data was collected within 48 hours of the closest approach in a phase called the Inner Core. Closest approach occurred January 1, 2019, at 05:33 UTC SCET at which point the probe was 43.4 AU from the Sun. At this distance, the one-way transit time for radio signals between Earth and New Horizons was six hours. Confirmation that the craft had succeeded in filling its digital recorders occurred when data arrived on Earth ten hours later, at 15:29 UTC. After the encounter, preliminary, high-priority data was sent to Earth on January 1 and 2, 2019. On January 9, New Horizons returned to a spin-stabilized mode to prepare sending the remainder of its data back to Earth. This download was expected to take 20 months at a data rate of 1–2 kilobits per second. As of July 2022, approximately 10% of the data was still left to be received. Post-Arrokoth events In April 2020, New Horizons was used in conjunction with telescopes on Earth to take pictures of nearby stars Proxima Centauri and Wolf 359; the images from each vantage point – over 6.4 billion km (4 billion miles) apart – were compared to produce "the first demonstration of an easily observable stellar parallax." Images taken by the LORRI camera while New Horizons was 42 to 45 AU from the Sun were used to measure the cosmic optical background, the visible light analog of the cosmic microwave background, in seven high galactic latitude fields. At that distance New Horizons saw a sky ten times darker than the sky seen by the Hubble Space Telescope because of the absence of diffuse background sky brightness from the zodiacal light in the inner solar system. These measurements indicate that the total amount of light emitted by all galaxies at ultraviolet and visible wavelengths may be lower than previously thought. The spacecraft reached a distance of 50 AU (7.5 billion km; 4.6 billion mi) on April 17, 2021, at 12:42 UTC, a feat performed only four times before, by Pioneer 10, Pioneer 11, Voyager 1, and Voyager 2. Voyager 1 is the farthest spacecraft from the Sun, more than 152 AU (22.7 billion km; 14.1 billion mi) away when New Horizons reached its landmark in 2021. The support team continued to use the spacecraft in 2021 to study the heliospheric environment (plasma, dust and gas) and to study other Kuiper Belt objects. In 2025, the first map of all Lyman-Alpha emissions in the Milky Way galaxy was published, based on New Horizons observations. After the spacecraft passed Arrokoth, the instruments continue to have enough power to be operational until the 2030s. Team leader Alan Stern stated there is potential for a third flyby in the 2020s at the outer edges of the Kuiper belt. This depends on a suitable Kuiper belt object being found or confirmed close enough to the spacecraft's current trajectory. Since May 2020, the New Horizons team has been using time on the Subaru Telescope to look for suitable candidates within the spacecraft's proximity. As of June 2024, no suitable targets had been found. Beginning in fiscal year 2025, it was planned for New Horizons to focus on specific heliophysics data, as stated by NASA in September 2023. It will remain available for a flyby of a different target until it leaves the Kuiper belt in 2028. New Horizons may also take a picture of Earth from its distance in the Kuiper belt, but only after completing all planned KBO flybys and imaging Uranus and Neptune. This is because pointing a camera towards Earth could cause the camera to be damaged by sunlight, as none of New Horizons' cameras have an active shutter mechanism. Speed New Horizons has been called "the fastest spacecraft ever launched" because it left Earth at 16.26 kilometers per second (58,536 km/h; 36,373 mph). It is also the first spacecraft launched directly into a solar escape trajectory, which requires an approximate speed while near Earth of 16.5 km/s (59,000 km/h; 37,000 mph),[b] plus additional delta-v to cover air and gravity drag, all to be provided by the launch vehicle. As of May 2, 2024, the spacecraft is 58.80 AU (8.796 billion km; 5.466 billion mi) from the Sun traveling at 13.68 kilometres per second (49,200 km/h; 30,600 mph). However, it is not the fastest spacecraft to leave the Solar System. As of July 2023[update], this record is held by Voyager 1, traveling at 16.985 km/s (61,146 km/h; 37,994 mph) relative to the Sun. Voyager 1 attained greater hyperbolic excess velocity than New Horizons due to gravity assists by Jupiter and Saturn. When New Horizons reaches the distance of 100 AU (15 billion km; 9.3 billion mi), it will be traveling at about 13 km/s (47,000 km/h; 29,000 mph), around 4 km/s (14,000 km/h; 8,900 mph) slower than Voyager 1 at that distance. The Parker Solar Probe can also be measured as the fastest object, because of its orbital speed relative to the Sun at perihelion: 191 km/s (690,000 km/h; 430,000 mph).[c] Because it remains in solar orbit, its specific orbital energy relative to the Sun is lower than New Horizons and other artificial objects escaping the Solar System. New Horizons' Star 48B third stage is also on a hyperbolic escape trajectory from the Solar System and reached Jupiter before the New Horizons spacecraft; it was expected to cross Pluto's orbit on October 15, 2015. Because it was not in controlled flight, it did not receive the correct gravity assist and passed within 200 million km (120 million mi) of Pluto. The Centaur second stage did not achieve solar escape velocity and remains in a heliocentric orbit. Gallery See also Notes References Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/MUSH] | [TOKENS: 611] |
Contents MUSH In multiplayer online games, a MUSH (a backronymed variation on MUD most often expanded as Multi-User Shared Hallucination, though Multi-User Shared Hack, Habitat, and Holodeck are also observed) is a text-based online social medium to which multiple users are connected at the same time. MUSHes are often used for online social interaction and role-playing games, although the first forms of MUSH do not appear to be coded specifically to implement gaming activity. MUSH software was originally derived from MUDs; today's two major MUSH variants are descended from TinyMUD, which was fundamentally a social game. MUSH has forked over the years and there are now different varieties with different features, although most have strong similarities and one who is fluent in coding one variety can switch to coding for the other with only a little effort. The source code for most widely used MUSH servers is open source and available from its current maintainers. A primary feature of MUSH codebases that tends to distinguish it from other multi-user environments is the ability, by default, of any player to extend the world by creating new rooms or objects and specifying their behavior in the MUSH's internal scripting language. The programming language for MUSH, usually referred to as "MUSHcode" or "softcode" (to distinguish it from "hardcode" – the language in which the MUSH server itself is written) was developed by Larry Foard. TinyMUSH started life as a set of enhancements to the original TinyMUD code. "MUSHcode" is similar in syntax to Lisp. Roleplay Traditionally, roleplay consists of a series of "poses". Each character makes a "pose" – that is, writes a description of speech, actions, etc. which the character performs. Special commands allow players to print OOC (out of character) messages, distinguished by a prefixed string from IC (in character) action. This medium borrows traits from both improvisational stage acting and writing. Roleplaying is one of the primary activities of MUSHes, along with socializing. There is nothing in the code base that restricts a new MUSH from being a traditional hack-and-slash MUD-style game. However, the earliest uses of MUSH servers were for roleplaying and socializing, and these early trends have largely governed their descendants. Administration All MUSH servers provide a flag that, when set on a player, bestows the ability to view and modify nearly everything in the game's database. Such players are usually called Wizards, and typically form the basis for the MUSH administration. Software Maintainers and developers of MUSH servers have traditionally shared ideas with one another, so most MUSH servers include concepts or code developed originally in other servers. There is particular interest in ensuring that common MUSHcode features work similarly across servers. PennMUSH, TinyMUSH, TinyMUX and RhostMUSH are all open-source MUSH servers See also References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Hybrid_computer] | [TOKENS: 870] |
Contents Hybrid computer Hybrid computers are computers that exhibit features of analog computers and digital computers. The digital component normally serves as the controller and provides logical and numerical operations, while the analog component often serves as a solver of differential equations and other mathematically complex problems.[citation needed] History The first desktop hybrid computing system was the Hycomp 250, released by Packard Bell in 1961. Another early example was the HYDAC 2400, an integrated hybrid computer released by EAI in 1963. In the 1980s, Marconi Space and Defense Systems Limited (under Peggy Hodges) developed their "Starglow Hybrid Computer", which consisted of three EAI 8812 analog computers linked to an EAI 8100 digital computer, the latter also being linked to an SEL 3200 digital computer. Late in the 20th century, hybrids dwindled with the increasing capabilities of digital computers including digital signal processors. In general, analog computers are extraordinarily fast, since they are able to solve most mathematically complex equations at the rate at which a signal traverses the circuit, which is generally an appreciable fraction of the speed of light. On the other hand, the precision of analog computers is not good; they are limited to three, or at most, four digits of precision.[citation needed] Digital computers can be built to take the solution of equations to almost unlimited precision, but quite slowly compared to analog computers. Generally, complex mathematical equations are approximated using iterative methods which take huge numbers of iterations, depending on how good the initial "guess" at the final value is and how much precision is desired. (This initial guess is known as the numerical "seed".) For many real-time operations in the 20th century, such digital calculations were too slow to be of much use (e.g., for very high frequency phased array radars or for weather calculations), but the precision of an analog computer is insufficient.[citation needed] Hybrid computers can be used to obtain a very good but relatively imprecise 'seed' value, using an analog computer front-end, which is then fed into a digital computer iterative process to achieve the final desired degree of precision. With a three or four digit, highly accurate numerical seed, the total digital computation time to reach the desired precision is dramatically reduced, since many fewer iterations are required. One of the main technical problems to be overcome in hybrid computers is minimizing digital-computer noise in analog computing elements and grounding systems.[citation needed] Consider that the nervous system in animals is a form of hybrid computer. Signals pass across the synapses from one nerve cell to the next as discrete (digital) packets of chemicals, which are then summed within the nerve cell in an analog fashion by building an electro-chemical potential until its threshold is reached, whereupon it discharges and sends out a series of digital packets to the next nerve cell. The advantages are at least threefold: noise within the system is minimized (and tends not to be additive), no common grounding system is required, and there is minimal degradation of the signal even if there are substantial differences in activity of the cells along a path (only the signal delays tend to vary). The individual nerve cells are analogous to analog computers; the synapses are analogous to digital computers.[citation needed] Hybrid computers are distinct from hybrid systems. The latter may be no more than a digital computer equipped with an analog-to-digital converter at the input and/or a digital-to-analog converter at the output, to convert analog signals for ordinary digital signal processing, and conversely, e.g., for driving physical control systems, such as servomechanisms.[citation needed] VLSI hybrid computer chip In 2015, researchers at Columbia University published a paper on a small scale hybrid computer in 65 nm CMOS technology. This 4th-order VLSI hybrid computer contains 4 integrator blocks, 8 multiplier/gain-setting blocks, 8 fanout blocks for distributing current-mode signals, 2 ADCs, 2 DACs and 2 SRAMs blocks. Digital controllers are also implemented on the chip for executing the external instructions. A robot experiment in the paper demonstrates the use of the hybrid computing chip in today's emerging low-power embedded applications.[citation needed] References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Mozilla_Firefox] | [TOKENS: 10634] |
Contents Firefox Mozilla Firefox is a free and open-source web browser developed by the Mozilla Foundation and its subsidiary, the Mozilla Corporation. It uses the Gecko rendering engine to display web pages, which implements current and anticipated web standards. The software is available for Windows, macOS, and Linux systems, with unofficial ports for other platforms, as well as a mobile version for Android (see Firefox for Android) and iOS. Firefox is the spiritual successor of Netscape Navigator, as the Mozilla community was created by Netscape in 1998, before Netscape's acquisition by AOL. Firefox was created in 2002 under the codename "Phoenix" by members of the Mozilla community who desired a standalone browser rather than the Mozilla Application Suite bundle. During its beta phase, it proved to be popular with its testers and was praised for its speed, security, and add-ons compared to Microsoft's then-dominant Internet Explorer 6. It was released on November 9, 2004, and challenged Internet Explorer's dominance with 60 million downloads within nine months. In November 2017, Firefox began incorporating new technology under the code name "Quantum" to promote parallelism and a more intuitive user interface. The current version of Firefox is available for Windows 10 or later versions of Windows, as well as macOS, and Linux. Its unofficial ports are available for various Unix and Unix-like operating systems, including FreeBSD, OpenBSD, NetBSD, and other operating systems, such as ReactOS. It is the default, pre-installed browser on Debian, Ubuntu, and some other Linux distros. Firefox is also available for Android and iOS. However, as with all other iOS web browsers, the iOS version uses the WebKit layout engine instead of Gecko due to platform requirements. An optimized version was also available on the Amazon Fire TV as one of the two main browsers available with Amazon's Silk Browser until April 30, 2021, when Firefox would be discontinued on that platform. Firefox usage share grew to a peak of 32.21% in November 2009, with Firefox 3.5 overtaking Internet Explorer 7, although not all versions of Internet Explorer as a whole; its usage then declined in competition with Google Chrome. As of February 2025[update], according to StatCounter, it had a 6.36% usage share on traditional PCs (i.e. as a desktop browser), making it the fourth-most popular PC web browser after Google Chrome (65%), Microsoft Edge (14%), and Safari (8.65%). Features Features of the desktop edition include tabbed browsing, full-screen mode, spell checking, incremental search, smart bookmarks, bookmarking and downloading through drag and drop, a download manager, user profile management, private browsing, bookmark tags, bookmark exporting, offline mode, a screenshot tool, web development tools, a "page info" feature which shows a list of page metadata and multimedia items, a configuration menu at about:config for power users, and location-aware browsing (also known as "geolocation") based on a Google service. Firefox has an integrated search system which uses Google by default in most markets, but multiple search engines can be selected from a drop-down when searching (or custom ones added) and the default is easily changed. DNS over HTTPS is another feature whose default behaviour is determined geographically. Firefox provides an environment for web developers in which they can use built-in tools, such as the Error Console or the DOM Inspector, and extensions, such as Firebug and more recently there has been an integration feature with Pocket. Firefox Hello was an implementation of WebRTC, added in October 2014, which allows users of Firefox and other compatible systems to have a video call, with the extra feature of screen and file sharing by sending a link to each other. Firefox Hello was scheduled to be removed in September 2016. Former features include a File Transfer Protocol (FTP) client for browsing file servers, the ability to block images from individual domains (until version 72), a 3D page inspector (versions 11 to 46), tab grouping (until version 44), and the ability to add customized extra toolbars (until version 28). Functions can be added through add-ons created by third-party developers. Add-ons are primarily coded using an HTML, CSS, JavaScript, with API known as WebExtensions, which is designed to be compatible with Google Chrome and Microsoft Edge extension systems. Firefox previously supported add-ons using the XUL and XPCOM APIs, which allowed them to directly access and manipulate much of the browser's internal functionality. As compatibility was not included in the multi-process architecture, XUL add-ons have been deemed Legacy add-ons and are no longer supported on Firefox 57 "Quantum" and newer. Mozilla has occasionally installed extensions for users without their permission. This happened in 2017 when an extension designed to promote the show Mr. Robot was silently added in an update to Firefox. Firefox can have themes added to it, which users can create or download from third parties to change the appearance of the browser. Firefox also provides dark, light, and system themes. Firefox implements many web standards, including HTML, XML, XHTML, MathML, SVG 1.1 (full), SVG 2 (partial), CSS (with extensions), ECMAScript (JavaScript), DOM, XSLT, XPath, and APNG (Animated PNG) images with alpha transparency. Firefox also implements standards proposals created by the WHATWG such as client-side storage, and the canvas element. These standards are implemented through the Gecko layout engine, and SpiderMonkey JavaScript engine. Firefox 4 was the first release to introduce significant HTML5 and CSS3 support. Firefox has passed the Acid2 standards-compliance test since version 3.0. Mozilla had originally stated that they did not intend for Firefox to pass the Acid3 test fully because they believed that the SVG fonts part of the test had become outdated and irrelevant, due to WOFF being agreed upon as a standard by all major browser makers. Because the SVG font tests were removed from the Acid3 test in September 2011, Firefox 4 and greater scored 100/100. Firefox also implements "Safe Browsing," a proprietary protocol from Google used to exchange data related to phishing and malware protection. Firefox supports the playback of video content protected by HTML5 Encrypted Media Extensions (EME), since version 38. For security and privacy reasons, EME is implemented within a wrapper of open-source code that allows execution of a proprietary DRM module by Adobe Systems—Adobe Primetime Content Decryption Module (CDM). CDM runs within a "sandbox" environment to limit its access to the system and provide it a randomized device ID to prevent services from uniquely identifying the device for tracking purposes. The DRM module, once it has been downloaded, is enabled and disabled in the same manner as other plug-ins. Since version 47, "Google's Widevine CDM on Windows and Mac OS X so streaming services like Amazon Video can switch from Silverlight to encrypted HTML5 video" is also supported. Mozilla justified its partnership with Adobe and Google by stating: Firefox downloads and enables the Adobe Primetime and Google Widevine CDMs by default to give users a smooth experience on sites that require DRM. Each CDM runs in a separate container called a sandbox, and you will be notified when a CDM is in use. You can also disable each CDM and opt out of future updates — Watch DRM content on Firefox and that it is "an important step on Mozilla's roadmap to remove NPAPI plugin support." Upon the introduction of EME support, builds of Firefox on Windows were also introduced that exclude support for EME. The Free Software Foundation and Cory Doctorow condemned Mozilla's decision to support EME. History The project began as an experimental branch of the Mozilla project by Dave Hyatt, Joe Hewitt, and Blake Ross. They believed the commercial requirements of Netscape's sponsorship and developer-driven feature creep compromised the utility of the Mozilla browser. To combat what they saw as the Mozilla Suite's software bloat, they created a standalone browser, with which they intended to replace the Mozilla Suite. Version 0.1, named Phoenix, was released on September 23, 2002. On April 3, 2003, the Mozilla Organization announced that it planned to change its focus from the Mozilla Suite to Firefox and Thunderbird. The Firefox project has undergone several name changes. The nascent browser was originally named Phoenix, after the mythical bird that rose triumphantly from the ashes of its dead predecessor (in this case, from the "ashes" of Netscape Navigator, after it was sidelined by Microsoft Internet Explorer in the "First Browser War"). Phoenix was renamed in 2003 due to a trademark claim from Phoenix Technologies. The replacement name, Firebird, provoked an intense response from the Firebird database software project. The Mozilla Foundation reassured them that the browser would always bear the name Mozilla Firebird to avoid confusion. After further pressure, Mozilla Firebird became Mozilla Firefox on February 9, 2004. The name Firefox was said to be derived from a nickname of the red panda, which became the mascot for the newly named project. For the abbreviation of Firefox, Mozilla prefers Fx or fx, although it is often abbreviated as FF or Ff. The Firefox project went through many versions before version 1.0 and had already gained a great deal of acclaim from numerous media outlets, such as Forbes and The Wall Street Journal. Among Firefox's popular features were the integrated pop-up blocker, tabbed browsing, and an extension mechanism for adding functionality. Although these features have already been available for some time in other browsers such as the Mozilla Suite and Opera, Firefox was the first of these browsers to have achieved large-scale adoption so quickly. Firefox attracted attention as an alternative to Internet Explorer, which had come under fire for its alleged poor program design and insecurity—detractors cite IE's lack of support for certain Web standards, use of the potentially dangerous ActiveX component, and vulnerability to spyware and malware installation.[citation needed] Microsoft responded by releasing Windows XP Service Pack 2, which added several important security features to Internet Explorer 6. Version 1.0 of Firefox was released on November 9, 2004. This was followed by version 1.5 in November 2005, version 2.0 in October 2006, version 3.0 in June 2008, version 3.5 in June 2009, version 3.6 in January 2010, and version 4.0 in March 2011. From version 5 onwards, the development and release model changed into a "rapid" one; by the end of 2011 the stable release was version 9, and by the end of 2012 it reached version 17. In 2016, Mozilla announced a project known as Quantum, which sought to improve Firefox's Gecko engine and other components to improve the browser's performance, modernize its architecture, and transition the browser to a multi-process model. These improvements came in the wake of decreasing market share to Google Chrome, as well as concerns that its performance was lagging in comparison. Despite its improvements, these changes required existing add-ons for Firefox to be made incompatible with newer versions, in favor of a new extension system that is designed to be similar to Chrome and other recent browsers. Firefox 57, which was released in November 2017, was the first version to contain enhancements from Quantum, and has thus been named Firefox Quantum. A Mozilla executive stated that Quantum was the "biggest update" to the browser since version 1.0. Unresponsive and crashing pages only affect other pages loaded within the same process. While Chrome uses separate processes for each loaded tab, Firefox distributes tabs over four processes by default (since Quantum), to balance memory consumption and performance. The process count can be adjusted, where more processes increase performance at the cost of memory, therefore suitable for computers with larger RAM capacity. In 2013, Firefox for Android added a guest session mode, which wiped browsing data such as tabs, cookies, and history at the end of each guest session. Guest session data was kept even when restarting the browser or device, and deleted only upon a manual exit. The feature was removed in 2019, purportedly to "streamline the experience". On May 3, 2019, the expiry of an intermediate signing certificate on Mozilla servers caused Firefox to automatically disable and lock all browser extensions (add-ons). Mozilla began the roll-out of a fix shortly thereafter, using their Mozilla Studies component. Support for Adobe Flash was dropped on January 6, 2021, with the release of Firefox 85. On June 1, 2021, Firefox's 'Proton' redesign was offered through its stable release channel after being made available in the beta builds. While users were initially allowed to revert to the old design through about:config, the corresponding key-value pairs reportedly stopped working in later builds, resulting in criticism. These included accessibility concerns despite Mozilla's claim to "continue to work with the accessibility community" and had not been resolved as of October 2024[update]. On January 13, 2022, an issue with Firefox's HTTP/3 implementation resulted in a widespread outage for several hours. On September 26, 2023, Firefox 118.0 introduced on-device translation of web page content. On January 23, 2024, along with the release of Firefox 122.0, Mozilla introduced an official APT repository for Debian-based Linux distributions. Security From its inception, Firefox was positioned as a security-focused browser. At the time, Internet Explorer, the dominant browser, was facing a security crisis. Multiple vulnerabilities had been found, and malware like Download.Ject could be installed simply by visiting a compromised website. The situation was so severe that the U.S. government reportedly issued warnings about security risks with Internet Explorer. Firefox, being less integrated with the operating system, was considered a safer alternative since it was less likely to have issues that could completely compromise a computer. This led to a significant increase in Firefox's popularity during the early 2000s as a more secure alternative. Moreover, Firefox was considered to have fewer actively exploitable security vulnerabilities compared to its competitors. In 2006, The Washington Post reported that exploit code for known security vulnerabilities in Internet Explorer was available for 284 days compared to only nine days for Firefox before the problem was fixed. A Symantec study around the same period showed that even though Firefox had a higher number of vulnerabilities, on average vulnerabilities were fixed faster in Firefox than in other browsers during that period. During this period, Firefox used a monolithic architecture, like most browsers at the time. This meant all browser components ran in a single process with access to all system resources. This setup had multiple security issues. If a web page used too many resources, the entire Firefox process would hang or crash, affecting all tabs. Additionally, any exploit could easily access system resources, including user files. Between 2008 and 2012, most browsers shifted to a multiprocess architecture, isolating high-risk processes like rendering, media, GPU, and networking. However, Firefox was slower to adopt this change. It wasn't until 2015 that Firefox started its Electrolysis (e10s) project to implement sandboxing across multiple components. This rewrite relied on interprocess communication using Chromium's interprocess communication library and placed various components, including the rendering component, in its sandbox. Firefox released this rewrite in to beta in August 2016, noting a 10–20% increase in memory usage, which was lower than Chrome's at the time. However, the rewrite caused issues with their legacy extension API, which was not designed to work cross-process and required shim code to function correctly. After over a year in beta, the rewrite was enabled by default all users of Firefox in November 2017. In 2012, Mozilla launched a new project called Servo to write a completely new and experimental browser engine utilizing memory safe techniques written in Rust. In 2018, Mozilla opted to integrate parts of the Servo project into the Gecko engine in a project codenamed the Quantum project. The project completely overhauled Firefox's page rendering code, resulting in performance and stability gains while also improving the security of existing components. Additionally, the older incompatible extension API was removed in favour of a WebExtension API that more closely resembled Google Chrome's extension system. This broke compatibility with older extensions but resulted in fewer vulnerabilities and a much more maintainable extension system. While the Servo project was intended to replace more parts of the Gecko Engine, this plan never came to fruition. In 2020, Mozilla laid off all developers on the Servo team transferring ownership of the project to the Linux Foundation. Privacy When Firefox was initially released, it used a custom script permission policy where scripts that were signed by the page could gain access to higher privilege actions, such as the ability to set a user's preferences. However, this model was not widely used and was later discontinued by Firefox. Modern day Firefox instead follows the standard same-origin policy permission model that is followed by most modern browsers which disallows scripts from accessing any privileged data including data about other websites. It uses TLS to protect communications with web servers using strong cryptography when using the HTTPS protocol. The freely available HTTPS Everywhere add-on enforces HTTPS, even if a regular HTTP URL is entered; this feature is now part of the browser. Firefox supports HTTP/2. In February 2013, plans were announced for Firefox 22 to disable third-party cookies by default. However, the introduction of the feature was then delayed so Mozilla developers could "collect and analyze data on the effect of blocking some third-party cookies." Mozilla also collaborated with Stanford University's "Cookie Clearinghouse" project to develop a blacklist and whitelist of sites that will be used in the filter. Version 23, released in August 2013, followed the lead of its competitors by blocking iframe, stylesheet, and script resources served from non-HTTPS servers embedded on HTTPS pages by default. Additionally, JavaScript could also no longer be disabled through Firefox's preferences, and JavaScript was automatically re-enabled for users who upgraded to 23 or higher with it disabled. The change was made because JavaScript was being used across a majority of websites on the web, and disabling JavaScript could potentially have untoward repercussions on inexperienced users who are unaware of its impact. Firefox also cited the fact that extensions like NoScript, which can disable JavaScript in a more controlled fashion, were widely available. The following release added the ability to disable JavaScript through the developer tools for testing purposes. Beginning with Firefox 48, all extensions must be signed by Mozilla to be used in release and beta versions of Firefox. Firefox 43 blocked unsigned extensions but allowed enforcement of extension signing to be disabled. All extensions must be submitted to Mozilla Add-ons and be subject to code analysis to be signed, although extensions do not have to be listed on the service to be signed. On May 2, 2019, Mozilla announced that it would be strengthening the signature enforcement with methods that included the retroactive disabling of old extensions now deemed to be insecure. Since version 60 Firefox includes the option to use DNS over HTTPS (DoH), which causes DNS lookup requests to be sent encrypted over the HTTPS protocol. To use this feature the user must set certain preferences beginning with "network.trr" (Trusted Recursive Resolver) in about:config: if network.trr.mode is 0, DoH is disabled; 1 activates DoH in addition to unencrypted DNS; 2 causes DoH to be used before unencrypted DNS; to use only DoH, the value must be 3. By setting network.trr.uri to the URL, special Cloudflare servers will be activated. Mozilla has a privacy agreement with this server host that restricts its collection of information about incoming DNS requests. On May 21, 2019, Firefox was updated to include the ability to block scripts that used a computer's CPU to mine cryptocurrency without a user's permission, in Firefox version 67.0. The update also allowed users to block known fingerprinting scripts that track their activity across the web, however it does not resist fingerprinting on its own. In February 2021, Firefox launched Total Cookie Protection in version 86 to offer protection against cross-site tracking, without breaking the websites users visit. Also known as state partitioning, Total Cookie Protection works by creating a separate "cookie jar" for each website, thereby preventing data from being shared between websites. The feature, which was named one of 2021's best security innovations by Popular Science, also isolates local storage, service workers, and other common ways for sites to store data. Total Cookie Protection was enabled by default in 2022. Localizations Firefox is a widely localized web browser. Mozilla uses the in-house Pontoon localization platform. The first official release in November 2004 was available in 24 different languages and for 28 locales. In 2019, Mozilla released Project Fluent a localization system that allows translators to be more flexible with their translation than to be constrained in one-to-one translation of strings. As of February 2026,[update] the supported versions of Firefox are available in 97 locales (88 languages). Platform availability There are desktop versions of Firefox for Microsoft Windows, macOS, and Linux, while Firefox for Android is available for Android (formerly Firefox for mobile, it also ran on Maemo, MeeGo, and Firefox OS) and Firefox for iOS is available for iOS. Smartphones that support Linux but not Android, or iOS apps can also run Firefox in its desktop version, for example using postmarketOS, Mobian or Ubuntu Touch. Notes Firefox source code may be compiled for various operating systems; however, officially distributed binaries are provided for the following: Firefox 1.0 was released for Windows 95, as well as Windows NT 4.0 or later. Some users reported the 1.x builds were operable (but not installable) on Windows NT 3.51. The version 42.0 release includes the first x64 build. It required Windows 7 or Server 2008 R2. Starting from version 49.0, Firefox for Windows requires and uses the SSE2 instruction set. In September 2013, Mozilla released a Metro-style version of Firefox, optimized for touchscreen use, on the "Aurora" release channel. However, on March 14, 2014, Mozilla cancelled the project because of a lack of user adoption. In March 2017, Firefox 52 ESR, the last version of the browser for Windows XP and Windows Vista, was released. Support for Firefox 52 ESR ended in June 2018. Traditionally, installing the Windows version of Firefox entails visiting the Firefox website and downloading an installer package, depending on the desired localization and system architecture. In November 2021, Mozilla made Firefox available on Microsoft Store. The Store-distributed package does not interfere with the traditional installation. The last version of Firefox for Windows 7 and 8 is Firefox 115 ESR, which was released in July 2023. Its end-of-life was initially planned to be in October 2024, however in July 2024, a Mozilla employee announced in a comment on Reddit that the company consider extending the support beyond the initial date, the duration of that extension being yet to be defined.[citation needed] In September 2024, the extension was announced for an initial period of six months. In the release calendar page, a note states that Mozilla will re-evaluate the situation in early 2025 to see if another extension will be needed or not and statute about 115 ESR end-of-life then. This extension has been renewed two more times, on February 18, 2025, and on September 3, 2025, for six additional months each time, which led the end-of-life date to March 2026. The first official release (Firefox version 1.0) supported macOS (then called Mac OS X) on the PowerPC architecture. Mac OS X builds for the IA-32 architecture became available via a universal binary, which debuted with Firefox 1.5.0.2 in 2006. Starting with version 4.0, Firefox was released for the x64 architecture, to which macOS had migrated. Version 4.0 also dropped support for PowerPC architecture, although other projects continued development of a PowerPC version of Firefox. Firefox was originally released for Mac OS X 10.0 and higher. The minimum OS then increased to Mac OS X 10.2 in Firefox 1.5 and 10.4 in Firefox 3. Firefox 4 dropped support for Mac OS X 10.4 and PowerPC Macs, and Firefox 17 dropped support for Mac OS X 10.5 entirely. The system requirements were left unchanged until 2016, when Firefox 49 dropped support for Mac OS X 10.6–10.8. Mozilla ended support for OS X 10.9–10.11 in Firefox 79, with those users being supported on the Firefox 78 ESR branch until November 2021. Most recently, Mozilla ended support for macOS 10.12–10.14 in Firefox 116, with those users being supported on the Firefox 115 ESR branch until late 2024. In September 2024, however, an extension was announced for the 115 ESR branch for an initial period of six months. This extension has been renewed twice, leading the end-of-life date to September 2025, and then to March 2026. Since its inception, Firefox for Linux has supported the 32-bit memory architecture of the IA-32 instruction set. 64-bit builds were introduced in the 4.0 release. The 46.0 release replaced GTK 2.18 with 3.4 as a system requirement on Linux and other systems running X.Org. Starting with 53.0, the 32-bit builds required the SSE2 instruction set. Firefox 145 dropped support for 32-bit Linux on November 11, 2025, with those users being supported on the Firefox 140 ESR branch until September 2026. ChromeOS is technically a Linux distribution, but it is so significant, it is listed anyway. Regardless, you can get Firefox on ChromeOS through the Google Play Store, going into terminal and typing Linux commands, or downloading a .deb file and loading Firefox. Firefox for mobile, code-named "Fennec", was first released for Maemo in January 2010 with version 1.0 and for Android in March 2011 with version 4.0. Support for Maemo was discontinued after version 7, released in September 2011. Fennec had a user interface optimized for phones and tablets. It included the Awesome Bar, tabbed browsing, add-on support, a password manager, location-aware browsing, and the ability to synchronize with the user's other devices with Mozilla Firefox using Firefox Sync. At the end of its existence, it had a market share of 0.5% on Android. In August 2020, Mozilla launched a new version of its Firefox for Android app, named Firefox Daylight to the public and codenamed Fenix, after a little over a year of testing. It boasted higher speeds with its new GeckoView engine, which is described as being "the only independent web engine browser available on Android". It also added Enhanced Tracking Protection 2.0, a feature that blocks many known trackers on the Internet. It also added the ability to place the address bar on the bottom, and a new Collections feature. However, it was criticized for only having nine Add-ons at launch, and missing certain features. In response, Mozilla stated that they will allow more Add-ons with time. Mozilla initially refused to port Firefox to iOS due to the restrictions Apple imposed on third-party iOS browsers. Instead of releasing a full version of the Firefox browser, Mozilla released Firefox Home, a companion app for the iPhone and iPod Touch based on the Firefox Sync technology, which allowed users to access their Firefox browsing history, bookmarks, and recent tabs. It also included Firefox's "Awesomebar" location bar. Firefox Home was not a web browser, the application launched web pages in either an embedded viewer for that one page, or by opening the page in the Safari app. Mozilla pulled Firefox Home from the App Store in September 2012, stating it would focus its resources on other projects. The company subsequently released the source code of Firefox Home's underlying synchronization software. In April 2013, then-Mozilla CEO Gary Kovacs said that Firefox would not come to iOS if Apple required the use of the WebKit layout engine to do so. One reason given by Mozilla was that before iOS 8, Apple had supplied third-party browsers with an inferior version of its JavaScript engine, which hobbled their performance, making it impossible to match Safari's JavaScript performance on the iOS platform. Apple later opened their "Nitro" JavaScript engine to third-party browsers. In 2015, Mozilla announced it was moving forward with Firefox for iOS, with a preview release made available in New Zealand in September of that year. It was fully released in November later that year. It is the first Firefox-branded browser not to use the Gecko layout engine as is used in Firefox for desktop and mobile. Apple's policies require all iOS apps that browse the web to use the built-in WebKit rendering framework and WebKit JavaScript, so using Gecko is not possible. Unlike Firefox on Android, Firefox for iOS does not support browser add-ons. In November 2016, Firefox released a new iOS app titled Firefox Focus, a private web browser. Firefox Reality was released for augmented reality and virtual reality headsets in September 2018. It supports traditional web-browsing through 2D windows and immersive VR pages through Web VR. Firefox Reality is available on HTC Vive, Oculus, Google Daydream and Microsoft Hololens headsets. In February 2022, Mozilla announced that Igalia took over stewardship of this project under the new name of Wolvic. Firefox has also been ported to FreeBSD, NetBSD, OpenBSD, OpenIndiana, OS/2, ArcaOS, SkyOS, RISC OS and BeOS/Haiku, and an unofficial rebranded version called Timberwolf has been available for AmigaOS 4. The Firefox port for OpenBSD has been maintained by Landry Breuil since 2010. Firefox is regularly built for the current branch of the operating system; the latest versions are packaged for each release and remain frozen until the next release. In 2017, Landry began hosting packages of newer Firefox versions for OpenBSD releases from 6.0 onwards, making them available to installations without the ports system. The Solaris 10 port of Firefox (including OpenSolaris) was maintained by the Oracle Solaris Desktop Beijing Team, until March 2018 when the team was disbanded. There was also an unofficial port of Firefox 3.6.x to IBM AIX and of v1.7.x to UnixWare. Channels and release schedule In March 2011, Mozilla presented plans to switch to the rapid release model, a faster 16-week development cycle, similar to Google Chrome. Ars Technica noted that this new cycle entailed "significant technical and operational challenges" for Mozilla (notably preserving third-party add-on compatibility), but that it would help accelerate Firefox's adoption of new web standards, features, and performance improvements. This plan was implemented in April 2011. The release process was split into four "channels", with major releases trickling down to the next channel every six to eight weeks. For example, the Nightly channel would feature a preliminary unstable version of Firefox 6, which would move to the experimental "Aurora" channel after preliminary testing, then to the more stable "beta" channel, before finally reaching the public release channel, with each stage taking around six weeks. For corporations, Mozilla introduced an Extended Support Release (ESR) channel, with new versions released every 30 weeks (and supported for 12 more weeks after a new ESR version is released), though Mozilla warned that it would be less secure than the release channel, since security patches would only be backported for high-impact vulnerabilities. In 2017, Mozilla abandoned the Aurora channel, which saw low uptake, and rebased Firefox Developer Edition onto the beta channel. Mozilla uses A/B testing and a staged rollout mechanism for the release channel, where updates are first presented to a small fraction of users, with Mozilla monitoring its telemetry for increased crashes or other issues before the update is made available to all users. In 2020, Firefox moved to a four-week release cycle, to catch up with Chrome in support for new web features. Chrome switched to a four-week cycle a year later. Licensing Firefox source code is free software, with most of it being released under the Mozilla Public License (MPL) version 2.0. This license permits anyone to view, modify, or redistribute the source code. As a result, several publicly released applications have been built from it, including Firefox's predecessor Netscape, the customizable Pale Moon, and the privacy focused Tor Browser. In the past, Firefox was licensed solely under the MPL, then version 1.1, which the Free Software Foundation criticized for being weak copyleft, as the license permitted, in limited ways, proprietary derivative works. Additionally, code only licensed under MPL 1.1 could not legally be linked with code under the GPL. To address these concerns, Mozilla re-licensed most of Firefox under the tri-license scheme of MPL 1.1, GPL 2.0, or LGPL 2.1. Since the re-licensing, developers were free to choose the license under which they received most of the code, to suit their intended use: GPL or LGPL linking and derivative works when one of those licenses is chosen, or MPL use (including the possibility of proprietary derivative works) if they chose the MPL. However, Mozilla released the GPL-compatible MPL 2.0 on January 3, 2012, and with the release of Firefox 13 on June 5, 2012, Mozilla used it to replace the tri-licensing scheme. Logo and visual identity The Firefox icon is a trademark used to designate the official Mozilla build of the Firefox software and builds of official distribution partners. For this reason, software distributors who distribute modified versions of Firefox do not use the icon. Early Firebird and Phoenix releases of Firefox were considered to have reasonable visual designs but fell short when compared to many other professional software packages. In October 2003, professional interface designer Steven Garrity authored an article covering everything he considered to be wrong with Mozilla's visual identity. Shortly afterwards, the Mozilla Foundation invited Garrity to head up the new visual identity team. The release of Firefox 0.8 in February 2004 saw the introduction of the new branding efforts. Included were new icon designs by silverorange, a group of web developers with a long-standing relationship with Mozilla. The final renderings are by Jon Hicks, who had worked on Camino. The logo was later revised and updated, fixing several flaws found when it was enlarged. The animal shown in the logo is a stylized fox, although "firefox" is usually a common name for the red panda. The panda, according to Hicks, "didn't really conjure up the right imagery" and was not widely known. In 2017, Mozilla made a sleeker, newer design of the Firefox logo as part of the quantum update. In June 2019, Mozilla unveiled a revised Firefox logo, which was officially implemented on version 70. The new logo is part of an effort to build a brand system around Firefox and its complementary apps and services, which are now being promoted as a suite under the Firefox brand. Trademark The name "Mozilla Firefox" is a registered trademark of Mozilla; along with the official Firefox logo, it may only be used under certain terms and conditions. Anyone may redistribute the official binaries in unmodified form and use the Firefox name and branding for such distribution, but restrictions are placed on distributions that modify the underlying source code. The name "Firefox" derives from a nickname of the red panda. Mozilla celebrated Red Pandas. Mozilla has placed the Firefox logo files under open-source licenses, but its trademark guidelines do not allow displaying altered or similar logos in contexts where trademark law applies. There has been some controversy over the Mozilla Foundation's intentions in stopping certain open-source distributions from using the "Firefox" trademark. Open-source browsers "enable greater choice and innovation in the market rather than aiming for mass-market domination." Mozilla Foundation Chairperson Mitchell Baker explained in an interview in 2007 that distributions could freely use the Firefox trademark if they did not modify source code, and that the Mozilla Foundation's only concern was with users getting a consistent experience when they used "Firefox". To allow distributions of the code without using the official branding, the Firefox build system contains a "branding switch". This switch, often used for alphas ("Auroras") of future Firefox versions, allows the code to be compiled without the official logo and name and can allow a derivative work unencumbered by restrictions on the Firefox trademark to be produced. In the unbranded build, the trademarked logo and name are replaced with a freely distributable generic globe logo and the name of the release series from which the modified version was derived.[citation needed] Distributing modified versions of Firefox under the "Firefox" name required explicit approval from Mozilla for the changes made to the underlying code, and required the use of all of the official branding. For example, it was not permissible to use the name "Firefox" without also using the official logo. When the Debian project decided to stop using the official Firefox logo in 2006 (because Mozilla's copyright restrictions at the time were incompatible with Debian's guidelines), they were told by a representative of the Mozilla Foundation that this was not acceptable and was asked either to comply with the published trademark guidelines or cease using the "Firefox" name in their distribution. Debian switched to branding their modified version of Firefox "Iceweasel" (but in 2016 switched back to Firefox), along with other Mozilla software. GNU IceCat is another derived version of Firefox distributed by the GNU Project, which maintains its separate branding. Promotion Firefox was adopted rapidly, with 100 million downloads in its first year of availability. This was followed by a series of aggressive marketing campaigns starting in 2004 with a series of events Blake Ross and Asa Dotzler called "marketing weeks". Firefox continued to heavily market itself by releasing a marketing portal dubbed "Spread Firefox" (SFX) on September 12, 2004. It debuted along with the Firefox Preview Release, creating a centralized space for the discussion of various marketing techniques. The release of their manifesto stated that "the Mozilla project is a global community of people who believe that openness, innovation, and opportunity are key to the continued health of the Internet." A two-page ad in the edition of December 16 of The New York Times, placed by Mozilla Foundation in coordination with Spread Firefox, featured the names of the thousands of people worldwide who contributed to the Mozilla Foundation's fundraising campaign to support the launch of the Firefox 1.0 web browser. SFX portal enhanced the "Get Firefox" button program, giving users "referrer points" as an incentive. The site lists the top 250 referrers. From time to time, the SFX team or SFX members launch marketing events organized at the Spread Firefox website. As a part of the Spread Firefox campaign, there was an attempt to break the world download record with the release of Firefox 3. This resulted in an official certified Guinness world record, with over eight million downloads. In February 2011, Mozilla announced that it would be retiring Spread Firefox (SFX). Three months later, in May 2011, Mozilla officially closed Spread Firefox. Mozilla wrote that "there are currently plans to create a new iteration of this website [Spread Firefox] at a later date." In celebration of the third anniversary of the founding of the Mozilla Foundation, the "World Firefox Day" campaign was established on July 15, 2006, and ran until September 15, 2006. Participants registered themselves and a friend on the website for nomination to have their names displayed on the Firefox Friends Wall, a digital wall that was displayed at the headquarters of the Mozilla Foundation. The Firefox community has also engaged in the promotion of its web browser. In 2006, some of Firefox's contributors from Oregon State University made a crop circle of the Firefox logo in an oat field near Amity, Oregon, near the intersection of Lafayette Highway and Walnut Hill Road. After Firefox reached 500 million downloads on February 21, 2008, the Firefox community celebrated by visiting Freerice to earn 500 million grains of rice. Other initiatives included Live Chat – a service Mozilla launched in 2007 that allowed users to seek technical support from volunteers. The service was later retired. To promote the launch of Firefox Quantum in November 2017, Mozilla partnered with Reggie Watts to produce a series of TV ads and social media content. Performance In December 2005, Internet Week ran an article in which many readers reported high memory usage in Firefox 1.5. Mozilla developers said that the higher memory use of Firefox 1.5 was at least partially due to the new fast backwards-and-forwards (FastBack) feature. Other known causes of memory problems were malfunctioning extensions such as Google Toolbar and some older versions of AdBlock, or plug-ins, such as older versions of Adobe Acrobat Reader. When PC Magazine in 2006 compared memory usage of Firefox 2, Opera 9, and Internet Explorer 7, they found that Firefox used approximately as much memory as each of the other two browsers. In 2006, Softpedia noted that Firefox 1.5 took longer to start up than other browsers, which was confirmed by further speed tests. Internet Explorer 6 launched more swiftly than Firefox 1.5 on Windows XP since many of its components were built into the OS and loaded during system startup. As a workaround for the issue, a preloader application was created that loaded components of Firefox on startup, similar to Internet Explorer. A Windows Vista feature called SuperFetch performs a similar task of preloading Firefox if it is used often enough.[citation needed] Tests performed by PC World and Zimbra in 2006 indicated that Firefox 2 used less memory than Internet Explorer 7. Firefox 3 used less memory than Internet Explorer 7, Opera 9.50 Beta, Safari 3.1 Beta, and Firefox 2 in tests performed by Mozilla, CyberNet, and The Browser World. In mid-2009, BetaNews benchmarked Firefox 3.5 and declared that it performed "nearly ten times better on XP than Microsoft Internet Explorer 7". In January 2010, Lifehacker compared the performance of Firefox 3.5, Firefox 3.6, Google Chrome 4 (stable and Dev versions), Safari 4, and Opera (10.1 stable and 10.5 pre-alpha versions). Lifehacker timed how long browsers took to start and reach a page (both right after boot-up and after running at least once already), timed how long browsers took to load nine tabs at once, tested JavaScript speeds using Mozilla's Dromaeo online suite (which implements Apple's SunSpider and Google's V8 tests) and measured memory usage using Windows 7's process manager. They concluded that Firefox 3.5 and 3.6 were the fifth- and sixth-fastest browsers, respectively, on startup, 3.5 was third- and 3.6 was sixth-fastest to load nine tabs at once, 3.5 was sixth- and 3.6 was fifth-fastest on the JavaScript tests. They also concluded that Firefox 3.6 was the most efficient with memory usage followed by Firefox 3.5. In February 2012, Tom's Hardware performance tested Chrome 17, Firefox 10, Internet Explorer 9, Opera 11.61, and Safari 5.1.2 on Windows 7. Tom's Hardware summarized their tests into four categories: Performance, Efficiency, Reliability, and Conformance. In the performance category they tested HTML5, Java, JavaScript, DOM, CSS 3, Flash, Silverlight, and WebGL (WebGL 2 is current as of version 51; and Java and Silverlight stop working as of version 52)—they also tested startup time and page load time. The performance tests showed that Firefox was either "acceptable" or "strong" in most categories, winning three categories (HTML5, HTML5 hardware acceleration, and Java), only finishing "weak" in CSS performance. In the efficiency tests, Tom's Hardware tested memory usage and management. With this category, it was determined that Firefox was only "acceptable" at performing light memory usage, while it was "strong" at performing heavy memory usage. In the reliability category, Firefox performed a "strong" amount of proper page loads. For the final category, conformance, it was determined that Firefox had "strong" conformance for JavaScript and HTML5. So in conclusion, Tom's Hardware determined that Firefox was the best browser for Windows 7 OS, but that it only narrowly beat Google Chrome. In June 2013, Tom's Hardware again performance tested Firefox 22, Chrome 27, Opera 12, and Internet Explorer 10. They found that Firefox slightly edged out the other browsers in their "performance" index, which examined wait times, JavaScript execution speed, HTML5/CSS3 rendering, and hardware acceleration performance. Firefox also scored the highest on the "non-performance" index, which measured memory efficiency, reliability, security, and standards conformance, finishing ahead of Chrome, the runner-up. Tom's Hardware concluded by declaring Firefox the "sound" winner of the performance benchmarks. In January 2014, a benchmark testing the memory usage of Firefox 29, Google Chrome 34, and Internet Explorer 11 indicated that Firefox used the least memory when a substantial number of tabs were open. In benchmark testing in early 2015 on a "high-end" Windows machine, comparing Microsoft Edge [Legacy], Internet Explorer, Firefox, Chrome, and Opera, Firefox achieved the highest score on three of the seven tests. Four different JavaScript performance tests gave conflicting results. Firefox surpassed all other browsers on the Peacekeeper benchmark, but was behind the Microsoft products when tested with SunSpider. Measured with Mozilla's Kraken, it came second place to Chrome, while on Google's Octane challenge, it took third behind Chrome and Opera. Firefox took the lead with WebXPRT, which runs several typical HTML5 and JavaScript tasks. Firefox, Chrome, and Opera all achieved the highest possible score on the Oort Online test, measuring WebGL rendering speed (WebGL 2 is now current). In terms of HTML5 compatibility testing, Firefox was ranked in the middle of the group. A similar set of benchmark tests in 2016 showed Firefox's JavaScript performance on Kraken and the newer Jetstream tests trailing slightly behind all other tested browsers except Internet Explorer (IE), which performed relatively poorly. On Octane, Firefox came ahead of IE and Safari, but again slightly behind the rest, including Vivaldi and Microsoft Edge [Legacy]. Edge [Legacy] took overall first place on the Jetstream and Octane benchmarks. In 2023, Microsoft published that it corrected a mistake in MS Windows after 5 years that slowed down programs, especially Firefox. As of September 2025, Firefox's market share is 4.45%. As of the adoption of Firefox 57 and Mozilla's Quantum project entering production browsers in November 2017, Firefox was tested to be faster than Chrome in independent JavaScript tests, and demonstrated to use less memory with many browser tabs opened. TechRadar rated it as the fastest web browser in a May 2019 report. Usage share Downloads have continued at an increasing rate since Firefox 1.0 was released, and as of 31 July 2009[update] Firefox had already been downloaded over one billion times. This number does not include downloads using software updates or those from third-party websites. They do not represent a user count, as one download may be installed on many machines, one person may download the software multiple times, or the software may be obtained from a third-party.[citation needed] In July 2010, IBM asked all employees (about 400,000) to use Firefox as their default browser. Firefox was the second-most used web browser until November 2011, when Google Chrome surpassed it. According to Mozilla, Firefox had more than 450 million users as of October 2012[update]. In October 2024, Firefox was the fourth-most widely used desktop browser, and it was the fourth-most popular with 2.95% of worldwide usage share of web browsers across all platforms. According to the Firefox Public Data report by Mozilla, the active monthly count of Desktop clients has decreased from around 310 million in 2017 to 200 million in 2023. From October 2020, the desktop market share of Firefox started to decline in countries where it used to be the most popular. In Eritrea, it dropped from 50% in October 2020 to 9.32% in September 2021. In Cuba, it dropped from 54.36% in Sept 2020 to 38.42% in September 2021. The UK and US governments both follow the 2% rule. This states that only browsers with more than 2% market share among visitors of their websites will be supported. There are concerns that support for Firefox will be dropped because as of December 29, 2023, the browser market share among US government website visitors is 2.2%. Reception Firefox has been criticized by web developers for late adoption of web standards and not fixing bugs which are decades old. No support for view transition, gradient and CSS features lack is also criticized. Firefox scores less on both HTML5test and JetStream2 compared to rival browsers. Other issues include high battery usage, being highly resource intensive, removal of tab group, use of telemetry, ads in search bar, dated download system, lack of PWA, and lack of ability to share text fragment. In 2025, Mozilla introduced a terms of use for Firefox, as a means to give more transparency over users' rights and permissions for the browser outside of the Mozilla Public License. The company received criticism centering around a clause that gave Mozilla a "nonexclusive, royalty-free, worldwide license" to use any information that was sent to Mozilla in the process of using the browser. The new terms were perceived as privacy-compromising and were motivated by a desire to use user data in AI model training. Mozilla denied these claims and asserted that many modified words were to ease readability, increase transparency, formalize existing implicit agreements, and describe the circumstances of a free browser, adding that the AI features are covered by a separate agreement. Criticism centered on fears that the license grant covered all data entered by the user, while Mozilla responded saying that the change "does NOT give us ownership of your data". Days later, in an attempt to respond to the fallout, Mozilla changed the wording of their privacy FAQ, removing a pledge to never "sell your personal data" and revising another section denying allegations that it sold user data, saying that it gathers some information from hideable advertisements as well as chatbot metadata when interacted with, and that the legal definition of "sell" was vague in some jurisdictions. See also References Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/Elegast] | [TOKENS: 1040] |
Contents Elegast Elegast (elf spirit[citation needed]) is the hero and noble robber in the poem Karel ende Elegast, an early Middle Dutch epic poem that has been translated into English as Charlemagne and Elbegast. In the poem, he possibly represents the King of the Elves. He appears as a knight on a black horse, an outcast vassal of Charlemagne living in the forest. The original Dutch poem uses the name Elegast, while translated versions of the poem commonly use the name Elbegast in German and English, or Alegast in the Scandinavian ballad. Karel ende Elegast Karel ende Elegast was an original poem in Middle Dutch that scholars think was probably written at the end of the 12th century, otherwise in the 13th century and set in the region of Charlemagne's castle in Ingelheim. It is a Frankish romance of Charlemagne ("Karel") as an exemplary Christian king who was led on a strange quest to be a robber. Although the poem does not describe Elegast's background, he was an old friend of Charlemagne that had fallen into disgrace, and his banishment to the forest and his name connotes he was elven. Elegast could put people to sleep magically, could open locks without keys, and has a magic herb that when put in his mouth allows him to talk to animals. He lived in the forest, thief to the rich people and kind to poor people. In summary, Charlemagne has a heavenly vision to go thieving in disguise, so meets with Elegast in the forest at night. Elegast does not recognize the king, as Charlemagne is in disguise as a thief. When Charlemagne suggests they steal from the king's castle, Elegast proves his loyalty to Charlemagne by refusing to steal from the king. Instead, Elegast takes Charlemagne to burgle the castle of Charlemagne's brother-in-law, Eggeric van Eggermonde. Once they break into the castle, Elegast overhears Eggeric scheming to kill Charlemagne to his wife, who is Charlemagne's sister. In this way Charlemagne learns of a traitor in his court. The next day, when Eggeric arrives in Charlemagne's court, Charlemagne has Eggeric searched and finds his weapons. Elegast duels with Eggeric and exposes him as a traitor. Eggeric is therefore killed, and his wife is given in marriage to Elegast. Elegast's reputation is also restored in the Charlemagne court. Name The names Elegast, Alegast, and Elbegast are variants of the same Germanic name: the Common Germanic *albi-gastiz, composed of the well attested elements *albi- "elf" and *gastiz "guest". There is one dwarf named Elbegast in Eddic texts.[citation needed] [dubious – discuss] According to Low German legends, Elbegast was a dwarf who could steal eggs from underneath birds. In folklore and legends of Northern Europe, Elbegast was called the king of both the elves and dwarfs. Some scholars propose Elegast is the character Alberich, whose name means "king of the elves". Alberich was a sorcerer in Merovingian epics[clarification needed] of the 5th to 8th centuries.[citation needed] Context This poetry is unique in the reference to Charlemagne (the "Christian" King) being friends with a character who could be symbolic of an elf or dwarf figure of the forest, as well Charlemagne trying robbery on divine inspiration. In this friendship, the poem combines Frankish legends of Charlemagne with some Dutch-Germanic mythology. The poem is also unique that a Dutch character Elegast is a hero, most other poems of the time concern Frankish people as the hero. Elegast is possibly symbolic of the Dutch people's pre-Christian myth of an ancient elf or folk hero. In the pre-Christian mythology the dwelling in the forest is a religious and sacred dwelling place. Historically the epic poem may be about a real insurrection against Charlemagne that occurred (circa 785?), as the following event was noted in 1240 in the Chronica Albrici Monachi Trium Fontium: "By the Austracians a dangerous plot was hatched against Charlemagne, of which Hardericus was the instigator. At the discovery of the plot many were dismembered and many were banished. [ ... ] And, as is told in a song, in order to discover this plot, Charlemagne, urged by an angel, went out thieving at night." According to legend, Ingelheim (meaning "Angel's Home") was named after the angel that Charlemagne saw in the vision. Adaptations Adaptations and translations: See also References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Judeo-Tat] | [TOKENS: 939] |
Contents Judeo-Tat Hebrew Judeo-Aramaic Judeo-Arabic Other Jewish diaspora languages Jewish folklore Jewish poetry Judeo-Tat or Juhuri (Cuhuri, Жугьури, ז׳אוּהאוּראִ) is a Judeo-Persian dialect and the traditional language spoken by the Mountain Jews in the eastern Caucasus Mountains, especially Azerbaijan, parts of Russia and today in Israel. It belongs to the southwestern group of the Iranian division of the Indo-European languages, albeit with heavy influence from Hebrew. The words Juhuri and Juhuro translate as "Jewish" and "Jews". The Iranic Tat language is spoken by the Muslim Tats of Azerbaijan, a group to which the Mountain Jews were mistakenly considered to belong during the era of Soviet historiography though the languages probably originated in the same region of the Persian Empire. Judeo-Tat features Semitic elements in all linguistic levels of the language. Uniquely, Judeo-Tat retains the voiced pharyngeal approximant, also known as ayin (ع/ע), a phoneme whose presence is considered to be a hallmark of Semitic languages such as Arabic and no longer found in Modern Hebrew; no neighbouring languages feature it. Judeo-Tat is an endangered language classified as "definitely endangered" by UNESCO's Atlas of the World's Languages in Danger. Distribution The language is spoken by an estimated 101,000 people: Dialects Being a variety of the Tat language, Judeo-Tat itself can be divided into several dialects: The dialects of Oğuz (formerly Vartashen) and the now extinct Jewish community of Mücü have not been studied well and thus cannot be classified. Phonology Alphabet In the early 20th century, Judeo-Tat used the Hebrew script. In the 1920s, the Latin script was adapted for it; later it was written in Cyrillic. The use of the Hebrew alphabet has enjoyed renewed popularity. Influences and etymology Judeo-Tat is a Southwest Iranian language (as is modern Persian) and is much more closely related to (but not fully mutually intelligible with) modern Persian than most other Iranian languages of the Caucasus (for example: Talysh, Ossetian, and Kurdish). However, it also bears strong influence from other sources: Medieval Persian: Postpositions are used predominantly in lieu of prepositions, for example in modern Persian: باز او > Judeo-Tat æ uræ-voz "with him/her". Arabic: like in modern Persian, a significant portion of the vocabulary is Arabic in origin. Unlike modern Persian, Judeo-Tat has almost universally retained the original pharyngeal/uvular phonemes of Arabic, for example /ʕæsæl/ "honey" (Arab. عسل), /sæbæħ/ "morning" (Arab. صباح). Hebrew: As in other Jewish dialects, the language also has many Hebrew loanwords, for example /ʃulħon/ "table" (Heb. שֻלחן shulḥan), /mozol/ "luck" (Heb. מזל mazal), /ʕoʃiɾ/ "rich" (Heb. עשיר ʻashir). Hebrew words are typically pronounced in the tradition of other Mizrahi Jews. Examples: ח and ע are pronounced pharyngeally (like Arabic ح, ع respectively); ק is pronounced as a voiced uvular plosive (like Persian ق/غ). Classical Hebrew /w/ (ו) and /aː/ (kamatz), however, are typically pronounced as /v/ and /o/ respectively (similar to the Persian/Ashkenazi traditions, but unlike the Iraqi tradition, which retains /w/ and /aː/) Azerbaijani: Vowel harmony and many loan words Russian: Loanwords adopted after the Russian Empire's annexation of Daghestan and Azerbaijan Northeast Caucasian languages: /tʃuklæ/ "small" (probably the same origin as the medieval Caucasian city name "Sera-chuk" mentioned by Ibn Battuta, meaning "little Sera") Other common phonology/morphology changes from classical Persian/Arabic/Hebrew: See also References Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/Mount_Pinatubo] | [TOKENS: 3925] |
Contents Mount Pinatubo Events/Artifacts (north to south) Events/Artifacts Artifacts Mount Pinatubo is an active stratovolcano in the Zambales Mountains in Luzon in the Philippines. Located on the tripoint of Zambales, Tarlac and Pampanga provinces, most people were unaware of its eruptive history before the pre-eruption volcanic activity in early 1991. Dense forests, which supported a population of several thousand indigenous Aetas, heavily eroded and obscured Pinatubo. Pinatubo is known for its VEI-6 eruption on June 15, 1991, the second-largest terrestrial eruption of the 20th century after the 1912 eruption of Novarupta in Alaska. The eruption coincided with Typhoon Yunya making landfall in the Philippines, which brought a dangerous mix of ash and rain to nearby towns and cities. Early predictions led to the evacuation of tens of thousands of people, saving many lives. The eruption severely damaged surrounding areas with pyroclastic surges, pyroclastic falls, and later, flooding lahars caused by rainwater re-mobilizing volcanic deposits. This destruction affected infrastructure and altered river systems for years. Minor dome-forming eruptions inside the caldera continued from 1992 to 1993. The 1991 eruption had worldwide effects. It released roughly 10 billion tonnes (1.1×1010 short tons) or 10 km3 (2.4 cu mi) of magma, bringing large amounts of minerals and toxic metals to the surface. It also released 20 million tonnes (22 million short tons) of SO2. It ejected more particulate into the stratosphere than any eruption since Krakatoa in 1883. In the following months, aerosols formed a global layer of sulfuric acid haze. Global temperatures dropped by about 0.5 °C (0.9 °F) in the years 1991–1993, and ozone depletion temporarily increased significantly. Geography The volcano is about 87 kilometers (54 mi) northwest of Manila, the capital of the Philippines. Near Mount Pinatubo are former military bases that were maintained by the United States. The U.S. Naval Base Subic Bay was 37 kilometers (23 mi) south of Pinatubo, and the extent of Clark Air Base was just 14 kilometers (8.7 mi) east of the volcano's summit. The volcano is near to about 6 million people. History Even before the 1991 eruption, Mount Pinatubo had little topographic prominence: it was 1,745 m (5,725 ft) above sea level, only about 600 m (2,000 ft) above nearby plains, and only about 200 m (660 ft) higher than surrounding peaks, which largely obscured it from view. It is part of a chain of volcanoes which lie along the western side of the island of Luzon called the Zambales Mountains. Pinatubo belongs to the Cabusilan sub-range of the Zambales Mountains, which consists of Mount Cuadrado, Mount Negron, Mount Mataba and Mount Pinatubo. They are subduction volcanoes, formed by the Eurasian plate sliding under the Philippine Mobile Belt along the Manila Trench to the west. Mount Pinatubo and the other volcanoes on this volcanic belt arise due to magmatic occlusion from this subduction plate boundary. Pinatubo is flanked on the west by the Zambales Ophiolite Complex, which is an easterly-dipping section of Eocene oceanic crust uplifted during the late Oligocene. The Tarlac Formation north, east and southeast of Pinatubo consists of marine, nonmarine and volcanoclastic sediments formed in the late Miocene and Pliocene. The most recent study of Mount Pinatubo before the activities of 1991 was the overall geological study in 1983 and 1984 made by F. G. Delfin for the Philippine National Oil Company as part of the surface investigations of the area before exploratory drilling and well testing for geothermal energy sources in 1988 to 1990. He recognized two life histories of the mountain, which he classified as "ancestral" and "modern" Pinatubo. Activity of Ancestral Pinatubo seems to have begun about 1.1 million years ago and probably ended tens of thousands of years or more before the birth of "modern" Pinatubo. Much of the rugged land around the present volcano consists of remnants of "ancestral" Pinatubo. It was an andesite and dacite stratovolcano whose eruptive activity was much less explosive than modern Pinatubo. Its center was roughly where the current volcano is. The projected height of the mountain is up to 2,300 m (7,500 ft), or 1.43 miles above sea level if it were a lone peak, based on a profile fitting to the remaining lower slopes, or lower if it had more than one peak. The old volcano is exposed in the walls of an old 3.5 km × 4.5 km (2.2 mi × 2.8 mi) wide caldera, referred to as Tayawan Caldera by Delfin. Some of the nearby peaks are the remnants of ancestral Pinatubo, left behind when the softer parts of the old mountain slopes were eroded by weathering. Ancestral Pinatubo is a somma volcano with modern Pinatubo as the new cone. Mount Dorst, to the east, is part of the dip slope of the ancestral Pinatubo. Several mountains near modern Pinatubo are old satellite vents of ancestral Pinatubo, forming volcanic plugs and lava domes. These satellite vents were probably active around the same time as the ancestral volcano and include the domes of Mount Negron, Mount Cuadrado, Mount Mataba and the Bituin and Tapungho plugs. Later eruptions of modern Pinatubo occurred episodically and lasted for periods much shorter than the repose intervals between them. Subsequent eruptions and eruptive period occurred about: Each of these eruptions seems to have been very large, ejecting more than 10 km3 (2.4 cu mi) of material and covering large parts of the surrounding areas with pyroclastic flow deposits. Some eruptive periods have lasted decades and perhaps as much as several centuries and might appear to include multiple large explosive eruptions. The maximum size of eruptions in each eruptive period though has been getting smaller through the more than 35,000-year history of modern Pinatubo, but this might be an artifact of erosion and burial of older deposits. The oldest eruption of modern Pinatubo, Inararo, was also its largest. The 1991 eruption was among the smallest documented in its geologic record. The volcano has never grown very large between eruptions, because it produces mostly unwelded, easily erodible deposits and periodically destroys the viscous domes that fill its vents. After the Buag eruption (c. 1500 AD), the volcano lay dormant, its slopes becoming completely covered in dense rainforest and eroded into gullies and ravines. The c. 500-year repose though between the Buag and present eruptive periods is among the shorter repose periods recognized in its geologic history. In March and April 1991, magma rising toward the surface from more than 32 km (20 mi) beneath Pinatubo triggered small volcano tectonic earthquakes and caused powerful steam explosions that blasted three craters on the north flank of the volcano. Thousands of small earthquakes occurred beneath Pinatubo through April, May and early June and many thousand of tons of noxious sulfur dioxide gas were also emitted by the volcano. From June 7 to 12, the first magma reached the surface of Mount Pinatubo. Because it had lost most of the gas contained in it on the way to the surface, the magma oozed out to form a lava dome but did not cause an explosive eruption. A small blast at 3:41 PST on June 12 marked the beginning of a new, more violent phase of the eruption as millions of cubic yards of gas-charged magma reached the surface and exploded in the reawakening volcano's first spectacular eruption. A few hours later the same day, massive blasts lasting about half an hour generated big eruption columns, which quickly reached heights of over 19 kilometres (62,000 ft) and which generated large pyroclastic surges extending up to four kilometres (2.5 mi) from the summit in some river valleys. Fourteen hours later, a 15-minute blast hurled volcanic matter to heights of 24 km (15 mi). Friction in the up-rushing ash column generated abundant volcanic lightning. When even more highly gas-charged magma reached Pinatubo's surface on June 15, the volcano exploded in a cataclysmic eruption that ejected more than 5 km3 (1.2 mi3) of material. The ash cloud from this climactic eruption rose 35 km (22 mi) into the atmosphere. At lower altitudes, the volcanic ash was blown in all directions by the intense cyclonic winds of a coincidentally occurring typhoon, and winds at higher altitudes blew the ash southwestward. A blanket of ash and larger pumice lapilli blanketed the countryside. Fine ash fell as far away as the Indian Ocean and satellites tracked the ash cloud several times around the globe. Huge pyroclastic flows roared down the flanks of Mount Pinatubo, filling once-deep valleys with fresh volcanic deposits as much as 200 m (660 ft) thick. The eruption removed so much magma and rock from below the volcano that the summit collapsed to form a 2.5 km (1.6 mi) wide caldera. Following the climactic eruption of June 15, 1991, activity at the volcano continued at a much lower level, with continuous ash eruptions lasting until August 1991 and episodic eruptions continuing for another month. Activity at the volcano remained low until July 1992 when a new lava dome started growing in the caldera. Volcanologists suspected that further violent eruptions could be possible, and some areas were evacuated. However, the eruption was only minor. The last eruption of Mount Pinatubo took place in 1993. The 1991 caldera afterwards filled with water from annual monsoon rains and a crater lake, Lake Pinatubo, was formed. In 1992, a growing lava dome formed an island, which was eventually submerged by the lake. Initially, the lake was hot and highly acidic, with a minimum pH of 2 and a temperature of about 40 °C (104 °F). Subsequent rainfall cooled and diluted the lake, lowering the temperature to 26 °C (79 °F) and raising the pH to 5.5 by 2003. The lake deepened by about 1 meter (3.3 ft) per month on average, eventually submerging the lava dome, until September 2001, when fears that the walls of the crater might be unstable prompted the Philippine government to order a controlled draining of the lake. An estimated 9,000 people were once again evacuated from surrounding areas in case a large flood was accidentally triggered. Workers cut a 5-meter (16 ft) notch in the crater rim and drained about a quarter of the lake's volume. On July 10, 2002, the west wall of the crater collapsed, slowly releasing approximately 160 million cubic meters (5.7×10^9 cu ft) of water and sediment into the Maraunot River in Botolan, Zambales. On July 26, 2011, a 5.9 magnitude earthquake struck close to Pinatubo; however, no major damages or casualties were reported. On March 4, 2021, the PHIVOLCS raised Alert Level 1 over Mount Pinatubo after reporting an increase on its seismic activity. Since January 2021, 1,722 volcanic earthquakes have been recorded within the vicinity of the volcano. On August 12, 2021, PHIVOLCS said it noted a "significant decrease" in volcanic earthquakes, with a total of 104 quakes or an average 2–3 events per day recorded from July 1 to August 1, 2021. The agency also downgraded Mt. Pinatubo's Alert Level 1 to Level 0, due to "continued decrease in earthquake activity and a return to baseline seismic parameters." On November 30, 2021, PHIVOLCS reported that a weak explosion occurred at Mt. Pinatubo between 12:09 p.m. and 12:13 p.m. (PST), which produced a plume. The agency later confirmed it was a phreatic explosion produced by hydrothermal fluids near the surface, rather than a magmatic eruption. On August 7, 2025, the Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported that earthquake-monitoring equipment at the San Jose observation station in Tarlac was stolen. The stolen instruments were valued at approximately ₱1.2 million, according to PHIVOLCS. Cultural history The word pinatubo could mean "fertile place where one can make crops grow", or could mean "made to grow", in Sambal and Tagalog, which may suggest a knowledge of its previous eruption in about 1500 AD. There is a local oral tradition suggestive of a folk memory of earlier large eruptions. An ancient legend tells of Bacobaco, a terrible spirit of the sea, who could metamorphose into a huge turtle and throw fire from his mouth. In the legend, when being chased by the spirit hunters, Bacobaco flees to the mountain and digs a great hole in its summit showering the surrounding land with rock, mud, dust and fire for three days; howling so loudly that the earth shakes. Aeta elders tell many stories about the history of the mountain, the best known being that it was once a Batung Mabye (Kapampangan language for "living stone"). It was said to have been planted on a kingdom by a displeased sorcerer but relocated by a hero. The mountain was soon turned into the abode of Apo Namalyari ("The lord of happenings/events"), the pagan deity of the Sambal, Aetas and Kapampangans living on the Zambales range. It was said to comprise the whole mountain range until Sinukuan of Mount Arayat (the god of the Kapampangans) became a strong rival of Namalyari. Their fight, which took place over the center plains, shattered the mountain into smaller bodies and Mount Arayat lost its center peak. Other versions have it that Pinatubo's peak shattered because of Namalyari's immense fury in an attempt to teach humans the meaning of fear and show how misdeeds will be punished. According to the native elders, Apo Namalyari induced the June 1991 eruption because of displeasure toward illegal loggers and Philippine National Oil Company executives who performed deep exploratory drilling and well testing on the volcano looking for geothermal heat from 1988 to 1990. Discouraging results from the wells forced the abandonment of the prospect 13 months before the April 2, 1991, explosions. Aetas granted ownership of Pinatubo After being driven away by the 1991 eruption of Mount Pinatubo, in May 2009 some 454 Aeta families in Pampanga were given the first clean ancestral land ownership on Mount Pinatubo with the Certificate of Ancestral Domain Title (CADT) by the National Commission on Indigenous Peoples (NCIP), the government agency that deals with issues concerning indigenous people of the Philippines. The approved and declared net land area of 7,440.1 ha (18,385 acres) covers the barangays of Mawakat and Nabuklod in Floridablanca, Pampanga, plus a portion of San Marcelino, Zambales, and a portion of Barangay Batiawan in Subic, Zambales. On January 14, 2010, some 7,000 Aeta families from Zambales were officially granted the Certificate of Ancestral Domain Title (CADT) covering the Zambales side of Pinatubo which includes the summit and Lake Pinatubo, officially becoming their lutan tua (ancestral land). The ancestral domain title covers 15,984 ha (39,500 acres) and includes the villages of Burgos, Villar, Moraza and Belbel in Botolan and portions of the towns of Cabangan, San Felipe and San Marcelino. Ancestral domain titles are awarded to a certain community or indigenous group who have occupied or possessed the land continuously in accordance with their customs and traditions since time immemorial. They have the legal right to collectively possess and to enjoy the land and its natural resources to the exclusion of others. Having the land title will protect them from others – including foreigners – exploiting their land without compensation to and consent from the indigenous tribes. In the past, the Aetas had to contend with mining companies, loggers, and recently, tourist companies who earn from Mount Pinatubo but do not compensate the local tribes. In popular culture Long before Mount Pinatubo became famous for its cataclysmic eruption, Philippine president Ramon Magsaysay, a native of Zambales, named his C-47 presidential plane Mt. Pinatubo. The plane crashed into Mount Manunggal in Cebu province in 1957, killing the president and twenty-four others on board. The shape of Mount Pinatubo's caldera inspired New Clark City Athletics Stadium in Capas, Tarlac. Hiking activity The caldera formed and Lake Pinatubo has, since June 15, 1991, become a tourist attraction with the preferred route through Barangay Santa Juliana in Capas, Tarlac. In April 2025, Aeta communities held a protest action calling attention to their exclusion from revenues from tourism on Mount Pinatubo. The protesters said they their calls for the NCIP to address the issue had been ignored. Indigenous rights activist Beverly Longid of KATRIBU said that the NCIP has a history of neglecting the Aeta indigenous peoples. Longid stated that there is a need to recognize "the Aeta and their rights over their ancestral land and territory". Biodiversity The Long-nosed forest mouse (Apomys sacobianus) is a species of rodent endemic to Mount Pinatubo, Philippines. The Zambales forest mouse (Apomys zambalensis) is a species of rodent endemic to Zambales Mountain Range, Philippines. See also Notes References External links |
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[SOURCE: https://en.wikipedia.org/wiki/OpenOffice.org] | [TOKENS: 5554] |
Contents OpenOffice.org OpenOffice.org is an open-source office productivity software suite. It originated from the proprietary StarOffice, developed by Star Division, which was acquired by Sun Microsystems in 1999. Sun open-sourced the software in July 2000 as a free alternative to Microsoft Office, and released OpenOffice.org version 1.0 on 1 May 2002. Latest version 4.1.16 in November 2025 is a security update. Following Sun's acquisition by Oracle Corporation, development of OpenOffice.org slowed and eventually ended. In 2011, Oracle donated the project to the Apache Software Foundation, which continues it as Apache OpenOffice,, with the most-recent version being 4.1.16, released on November 10, 2025. A fork of OpenOffice, LibreOffice, was created in 2010 by members of the OpenOffice.org community. OpenOffice includes applications for word processing (Writer), spreadsheets (Calc), presentations (Impress), vector graphics (Draw), database management (Base), and formula editing (Math). Its default file format is the OpenDocument Format (ODF), which it originated. It can also read a wide variety of other file formats, with particular attention to those from Microsoft Office. OpenOffice.org was primarily developed for Linux, Microsoft Windows and Solaris, and later for Mac OS X, with ports to other operating systems. It is distributed under the GNU Lesser General Public License version 3 (LGPL); early versions are also available under the Sun Industry Standards Source License (SISSL). History OpenOffice.org originated from StarOffice, a proprietary office productivity software suite developed by German company Star Division beginning in 1985. In August 1999, Star Division was acquired by Sun Microsystems for US$59.5 million (equivalent to US$115 million in 2025), reportedly because the acquisition was less expensive than licensing Microsoft Office for Sun's 42,000 employees. On 19 July 2000, at the O'Reilly Open Source Convention, Sun announced that it would release the StarOffice source code to encourage the development of a free and open-source office suite. The project, officially named OpenOffice.org, with the ".org" added to avoid trademark conflicts, officially released its source code on 13 October 2000. The first public preview, Milestone Build 638c, followed in October 2001 and quickly surpassed one million downloads. OpenOffice.org 1.0 was officially released on 1 May 2002. OpenOffice.org became the default office suite on many Linux distributions and quickly emerged as a significant competitor to Microsoft Office, reportedly achieving 14% penetration in the large enterprise market by 2004. Sun designed the suite's OpenOffice.org XML file format, compressed in a ZIP archive, for easier data interchange and machine processing, intending it to replace proprietary binary formats. In 2002, Sun submitted the format to the Organization for the Advancement of Structured Information Standards leading to the creation of the OpenDocument file format standard in 2005, which was ratified as ISO/IEC 26300 in 2006. OpenDocument became OpenOffice's default format beginning with version 2.0 and other organizations would adopt the OpenDocument format. Development of OpenOffice.org was led by Sun, which continued to use the codebase as the upstream source for StarOffice, which it continued to sell commercially. Sun also licensed the codebase to third parties, including IBM, which used it as the foundation for IBM Lotus Symphony (originally IBM Workplace). This dual role led to criticism that Sun prioritized commercial interests over community collaboration. For example, building OpenOffice.org on many Linux distributions proved difficult, prompting the creation of projects like ooo-build to improve compatibility and incorporate unaccepted community patches. Sun was also criticized for being slow to accept outside contributions and controversially required contributors to sign a Contributor Agreement granting joint ownership of submitted code, enabling the company to continue selling proprietary versions of the software. Following Sun's acquisition by Oracle Corporation in January 2010, development continued under the a new brand, Oracle Open Office. However, Oracle significantly reduced the number of developers assigned to the project, and its commitment to the project was widely questioned. In September 2010, the majority of community OpenOffice contributors left the project, and formed The Document Foundation (TDF), citing concerns over Oracle's management of the project and its broader approach to open-source software. TDF launched a fork called LibreOffice in January 2011, which was quickly adopted by most Linux distributions. In April 2011, Oracle ceased development of OpenOffice and laid off the remaining team. While Oracle did not publicly state its reasons, speculation ranged from the project's declining community support to commercial considerations. In June 2011, Oracle donated the OpenOffice.org trademarks and codebase to the Apache Software Foundation. The code was relicensed under the Apache License at the request of IBM, which existing contractual interests in the code and preferred a permissive license. This donation became the foundation for the ongoing Apache OpenOffice project. During Sun's sponsorship, the OpenOffice.org project was governed by the Community Council, comprising OpenOffice.org community members. The Community Council suggested project goals and coordinated with producers of derivatives on long-term development planning issues. Both Sun and Oracle are claimed to have made decisions without consulting the Council or in contravention to the council's recommendations, leading to the majority of outside developers leaving for LibreOffice. Oracle demanded in October 2010 that all Council members involved with the Document Foundation step down, leaving the Community Council composed only of Oracle employees. Although the project was commonly called OpenOffice, the official name was OpenOffice.org because "OpenOffice" was already a registered trademark in the Benelux region, owned by the company Open Office Automatisering since 1999. A similar trademark conflict in Brazil led to the suite being distributed there as BrOffice.org starting in 2004. The name was also adopted by a supporting nonprofit organization founded in 2006. The BrOffice.org nonprofit transitioned to supporting LibreOffice in December 2010. Features OpenOffice.org 1.0 was launched under the following mission statement: The mission of OpenOffice.org is to create, as a community, the leading international office suite that will run on all major platforms and provide access to all functionality and data through open-component based APIs and an XML-based file format. The suite contained no personal information manager, email client or calendar application analogous to Microsoft Outlook, despite one having been present in StarOffice 5.2. Such functionality was frequently requested. The OpenOffice.org Groupware project, intended to replace Outlook and Microsoft Exchange Server, spun off in 2003 as OpenGroupware.org, which is now SOGo. The project considered bundling Mozilla Thunderbird and Mozilla Lightning for OpenOffice.org 3.0. The latest version, 4.1.16, is a security update, and this version supports Windows 10, 11, macOS and Linux. An older release, 3.4 Beta 1, was available for IA-32 versions of Windows 2000 Service Pack 2 or later, Linux (IA-32 and x64), Solaris and Mac OS X 10.4 or later, and the SPARC version of Solaris. The latest versions of OpenOffice.org on other operating systems were: OpenOffice.org included OpenSymbol, DejaVu, the Liberation fonts (from 2.4) and the Gentium fonts (from 3.2). Versions up to 2.3 included the Bitstream Vera fonts. OpenOffice.org also used the default fonts of the running operating system. Fontwork is a feature that allows users to create stylized text with special effects differing from ordinary text with the added features of gradient colour fills, shaping, letter height, and character spacing. It is similar to WordArt used by Microsoft Word. When OpenOffice.org saved documents in Microsoft Office file format, all Fontwork was converted into WordArt. From version 2.0.4, OpenOffice.org supported third-party extensions. As of April 2011, the OpenOffice Extension Repository listed more than 650 extensions. Another list was maintained by the Free Software Foundation. OpenOffice.org included OpenOffice Basic, a programming language similar to Microsoft Visual Basic for Applications (VBA). OpenOffice Basic was available in Writer, Calc and Base. OpenOffice.org also had some Microsoft VBA macro support. OpenOffice.org could interact with databases (local or remote) using ODBC (Open Database Connectivity), JDBC (Java Database Connectivity) or SDBC (StarOffice Database Connectivity). File formats From Version 2.0 onward, OpenOffice.org used ISO/IEC 26300:2006 OpenDocument as its native format. Versions 2.0–2.3.0 default to the ODF 1.0 file format; versions 2.3.1–2.4.3 default to ODF 1.1; versions 3.0 onward default to ODF 1.2. OpenOffice.org 1 used OpenOffice.org XML as its native format. This was contributed to OASIS and OpenDocument was developed from it. OpenOffice.org also claimed support for the following formats: Development OpenOffice.org converted all external formats to and from an internal XML representation. The OpenOffice.org API was based on a component technology known as Universal Network Objects (UNO). It consisted of a wide range of interfaces defined in a CORBA-like interface description language. OpenOffice.org 1.0 was criticized for not having the look and feel of applications developed natively for the platforms on which it runs. Starting with version 2.0, OpenOffice.org used native widget toolkit, icons, and font-rendering libraries on GNOME, KDE and Windows. The issue had been particularly pronounced on Mac OS X. Early versions of OpenOffice.org required the installation of X11.app or XDarwin (though the NeoOffice port supplied a native interface). Versions since 3.0 ran natively using Apple's Aqua GUI. Although originally written in C++, OpenOffice.org became increasingly reliant on the Java Runtime Environment, even including a bundled JVM. OpenOffice.org was criticized by the Free Software Foundation for its increasing dependency on Java, which was not free software. The issue came to the fore in May 2005, when Richard Stallman appeared to call for a fork of the application in a posting on the Free Software Foundation website. OpenOffice.org adopted a development guideline that future versions of OpenOffice.org would run on free implementations of Java and fixed the issues which previously prevented OpenOffice.org 2.0 from using free-software Java implementations. On 13 November 2006, Sun committed to releasing Java under the GNU General Public License and had released a free software Java, OpenJDK, by May 2007. In 2006, Lt. Col. Eric Filiol of the Laboratoire de Virologie et de Cryptologie de l'ESAT demonstrated security weaknesses, in particular within macros. In 2006, Kaspersky Lab demonstrated a proof of concept virus, "Stardust", for OpenOffice.org. This showed OpenOffice.org viruses are possible, but there is no known virus "in the wild". As of October 2011, Secunia reported no known unpatched security flaws for the software. A vulnerability in the inherited OpenOffice.org codebase was found and fixed in LibreOffice in October 2011 and Apache OpenOffice in May 2012. Version history The source code for OpenOffice.org was released on 13 October 2000. The first public preview, known as milestone build 638c, was made available in October 2001. The first stable release, OpenOffice.org 1.0, was launched on 1 May 2002, under both the LGPL and SISSL licenses for Windows, Linux, and Solaris platforms. A Mac OS X version, using an X11 interface, was released on 23 June 2003. OpenOffice.org 1.0.3.1, released in April 2003, was the last version to officially support Windows 95. The subsequent major release, OpenOffice.org 1.1, launched on 2 September 2003, introduced several new features, including one-click export to PDF, export to Flash (.SWF), macro recording, and a basic extension mechanism for third-party add-ons. Version 1.1.1, released on 29 March 2004, was notable for being included in the OpenCD project, a curated collection of open-source software for Windows users. On 2 September 2005, Sun announced it would retire the SISSL to help reduce license proliferation, though some analysts speculated the move was also intended to prevent IBM from reusing the code without contributing back. The 1.1.4 update, released on 22 December 2004, was the last version distributed under the dual SISSL and LGPL licenses. The change also applied to beta versions of OpenOffice.org 2, already under development. The final release in the OpenOffice.org 1 series, version 1.1.5, arrived on 9 September 2005. It introduced the ability to edit documents in the OpenDocument format (ODF) and was the last version to officially support Windows NT 4.0. Development of version 2.0 began in early 2003, guided by the "Q Product Concept", which aimed to improve Microsoft Office compatibility, performance, scripting support, GNOME integration, database usability, digital signatures, and overall user experience. It also marked the transition to ODF as the default file format. The first beta was released on 4 March 2005. The final version 2.0 was released on 20 October 2005, followed by version 2.0.1 eight weeks later, which included bug fixes and new features. With version 2.0.3, the project switched from an 18-month release cycle to quarterly updates. Version 2.1, released on 12 December 2006, included minor enhancements and bug fixes. This was followed by version 2.2 on 29 March 2007, which added further refinements, security updates, and small usability improvements. Version 2.3, released on 17 September 2007, introduced a redesigned charting component, enhanced the extension manager, and made several additional minor upgrades. On 27 March 2008, version 2.4 was released with new features and bug fixes, incorporating enhancements from RedOffice, a Chinese derivative of OpenOffice.org. The final maintenance release in the OpenOffice.org 2 series, version 2.4.3, arrived on 4 September 2009 and was the last version to officially support Windows 98 and Windows ME. Version 2 received significant media attention. PC Pro gave it a perfect 6-star rating, noting that it now rivaled Microsoft Office in features. Federal Computer Week listed it among the "5 stars of open-source products," citing the importance of the ODF standard. Computerworld reported that migrating to OpenOffice.org 2.0 cost some large government agencies just a tenth of the price of upgrading to Microsoft Office 2007. Version 3.0 was released on 13 October 2008, introducing several major changes, including the ability to import (though not export) documents in Microsoft's Office Open XML format, compatibility with ODF 1.2, improved handling of Microsoft's Visual Basic for Applications macros, and a native Mac OS X interface. It also introduced the "Start Center" and adopted the LGPL version 3 license. The 3.1 update, released on 7 May 2009, added support for overlining text and transparent dragging of objects. Version 3.2, released on 11 February 2010, improved support for PostScript-based OpenType fonts, added integrity checks for ODF files with repair options, and reduced "cold start" times by 46% compared to version 3.0. This release also introduced new features and performance enhancements. Version 3.2.1 followed on 4 June 2010, featuring bug fixes, refreshed OpenDocument icons, and an updated "Oracle Start Center." It was the first stable release under Oracle's ownership. The final Oracle-sponsored version, 3.3, was released on 26 January 2011. It added new spreadsheet functions and parameters, a revised print form, a FindBar, and usability improvements in Impress. Version 3.3 was also the last stable release to support Windows 2000 and Mac OS X on PowerPC systems. Version 3.3, the last Oracle version, was released in January 2011. New features include an updated print form, a FindBar and interface improvements for Impress. In parallel, Oracle released a commercial variant Oracle Open Office 3.3 (formerly named StarOffice) on 15 December 2010, along with a proprietary cloud-based suite called Oracle Cloud Office, built on a separate codebase. A beta of OpenOffice.org 3.4 was released on 12 April 2011, featuring SVG import, improved support for ODF 1.2, and enhanced spreadsheet functionality. However, before a final release could be issued, Oracle withdrew its support for the project, disbanding the remaining development team. Market share Problems arise in estimating the market share of OpenOffice.org because it could be freely distributed via download sites (including mirror sites), peer-to-peer networks, CDs, Linux distributions and so forth. The project tried to capture key adoption data in a market-share analysis, listing known distribution totals, known deployments and conversions and analyst statements and surveys. According to Valve, as of July 2010, 14.63% of Steam users had OpenOffice.org installed on their machines. A market-share analysis conducted by a web analytics service in 2010, based on over 200,000 Internet users, showed a wide range of adoption in different countries: 0.2% in China, 9% in the US and the UK and over 20% in Poland, the Czech Republic, and Germany. Although Microsoft Office retained 95% of the general market — as measured by revenue — as of August 2007, OpenOffice.org and StarOffice had secured 15–20% of the business market as of 2004 and a 2010 University of Colorado at Boulder study reported that OpenOffice.org had reached a point where it had an "irreversible" installed user base and that it would continue to grow. The project claimed more than 98 million downloads as of September 2007 and 300 million total to the release of version 3.2 in February 2010. The project claimed over one hundred million downloads for the OpenOffice.org 3 series within a year of release. Large-scale users of OpenOffice.org included Singapore's Ministry of Defence, and Banco do Brasil. As of 2006[update] OpenOffice.org was the official office suite for the French Gendarmerie. In India, several government organizations such as Employees' State Insurance, IIT Bombay, National Bank for Agriculture and Rural Development, the Supreme Court of India, ICICI Bank, and the Allahabad High Court, which use Linux, completely relied on OpenOffice.org for their administration. In Japan, conversions from Microsoft Office to OpenOffice.org included many municipal offices: Sumoto, Hyōgo, in 2004, Ninomiya, Tochigi in 2006, Aizuwakamatsu, Fukushima, in 2008 (and to LibreOffice as of 2012), Shikokuchūō, Ehime, in 2009, Minoh, Osaka, in 2009 Toyokawa, Aichi, Fukagawa, Hokkaido, and Katano, Osaka, in 2010 and Ryūgasaki, Ibaraki, in 2011. Corporate conversions included Assist in 2007 (and to LibreOffice on Ubuntu in 2011), Sumitomo Electric Industries in 2008 (and to LibreOffice in 2012), Toho Co., Ltd. in 2009 and Shinsei Financial Co., Ltd. in 2010. Assist also provided support services for OpenOffice.org. In July 2007, Everex, a division of First International Computer and the 9th-largest PC supplier in the U.S., began shipping systems preloaded with OpenOffice.org 2.2 into Wal-Mart, K-mart and Sam's Club outlets in North America. Forks and derivative software A number of open source and proprietary products derive at least some code from OpenOffice.org. Major derivatives include: In June 2011, Oracle donated the OpenOffice.org codebase and trademarks to The Apache Software Foundation. The resulting project, Apache OpenOffice project was expected to be developed by contributors from IBM, Linux distributors, and public sector agencies. In practice, most of the development was carried out by IBM, which had hired several former project developers from Oracle. To comply with Apache's licensing policies, the project removed or replaced components from OpenOffice.org 3.4 beta 1 whose licenses were incompatible with the Apache License. The first Apache release, OpenOffice 3.4.0, was published in May 2012. Later that year, IBM donated the codebase of Lotus Symphony, its customized version of OpenOffice.org, which was merged into Apache OpenOffice 4.0. Symphony was then discontinued. After IBM's withdrawal, the project has struggled to maintain a sustainable contributor base. Since 2015, Apache OpenOffice has faced ongoing difficulties delivering timely security patches. The most recent major feature release was version 4.1 in 2014, with the latest maintenance release, 4.1.16, issued on 10 November 2025. In September 2016, discussions began about possibly retiring the project entirely, though no final decision was made. As of July 2025, Apache OpenOffice remains available for download, but the Apache Software Foundation acknowledges that the software contains multiple unresolved security vulnerabilities. Although the Apache project considers itself the direct continuation of OpenOffice.org, others have described it as a fork or at least a separate project, due to its different governance model, licensing, and development direction. Sun had stated in the original OpenOffice.org announcement in 2000 that the project would be run by a neutral foundation, and put forward a more detailed proposal in 2001. There were many calls to put this into effect over the ensuing years. On 28 September 2010, in frustration at years of perceived neglect of the codebase and community by Sun and then Oracle, members of the OpenOffice.org community announced a non-profit called The Document Foundation and a fork of OpenOffice.org named LibreOffice. Go-oo improvements were merged, and that project was retired in favour of LibreOffice. The goal was to produce a vendor-independent office suite with ODF support and without any copyright assignment requirements. Oracle was invited to become a member of the Document Foundation and was asked to donate the OpenOffice.org brand. Oracle instead demanded that all members of the OpenOffice.org Community Council involved with the Document Foundation step down, leaving the Council composed only of Oracle employees. Most Linux distributions promptly replaced OpenOffice.org with LibreOffice; Oracle Linux 6 also features LibreOffice rather than OpenOffice.org or Apache OpenOffice. The project rapidly accumulated developers, development effort and added features, the majority of outside OpenOffice.org developers having moved to LibreOffice. In March 2015, an LWN.net development comparison of LibreOffice with Apache OpenOffice concluded that "LibreOffice has won the battle for developer participation". Collabora Online is a version of LibreOffice with a web interface and real-time collaborative editing. It is developed by Collabora Productivity. Collabora Online also has local client applications for Android, Chromebooks, iOS, iPadOS, Linux, Mac and Windows. NeoOffice, an independent commercial port for Macintosh that tracked the main line of development, offered a native Mac OS X Aqua user interface before OpenOffice.org did. Later versions are derived from Go-oo, rather than directly from OpenOffice.org. All versions from NeoOffice 3.1.1 to NeoOffice 2015 were based on OpenOffice.org 3.1.1, though latter versions included stability fixes from LibreOffice and Apache OpenOffice. NeoOffice 2017 and later versions are fully based on LibreOffice. The ooo-build patch set was started at Ximian in 2002, because Sun was slow to accept outside work on OpenOffice.org, even from corporate partners, and to make the build process easier on Linux. It tracked the main line of development and was not intended to constitute a fork. Most Linux distributions used, and worked together on, ooo-build. Sun's contributions to OpenOffice.org had been declining for a number of years and some developers were unwilling to assign copyright in their work to Sun, particularly given the deal between Sun and IBM to license the code outside the LGPL. On 2 October 2007, Novell announced that ooo-build would be available as a software package called Go-oo, not merely a patch set. (The go-oo.org domain name had been in use by ooo-build as early as 2005.) Sun reacted negatively, with Simon Phipps of Sun terming it "a hostile and competitive fork". Many free software advocates worried that Go-oo was a Novell effort to incorporate Microsoft technologies, such as Office Open XML, that might be vulnerable to patent claims. However, the office suite branded "OpenOffice.org" in most Linux distributions, having previously been ooo-build, soon in fact became Go-oo. Go-oo also encouraged outside contributions, with rules similar to those later adopted for LibreOffice. When LibreOffice forked, Go-oo was deprecated in favour of that project. OpenOffice Novell edition was a supported version of Go-oo. The Workplace Managed Client in IBM Workplace 2.6 (23 January 2006) incorporated code from OpenOffice.org 1.1.4, the last version under the SISSL. This code was broken out into a separate application as Lotus Symphony (30 May 2008), with a new interface based on Eclipse. Symphony 3.0 (21 October 2010) was rebased on OpenOffice.org 3.0, with the code licensed privately from Sun. IBM's changes were donated to the Apache Software Foundation in 2012, Symphony was deprecated in favour of Apache OpenOffice and its code was merged into Apache OpenOffice 4.0. Sun used OpenOffice.org as a base for its commercial proprietary StarOffice application software, which was OpenOffice.org with some added proprietary components. Oracle bought Sun in January 2010 and quickly renamed StarOffice to Oracle Open Office. Oracle discontinued development in April 2011. References External links |
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Contents Extraterrestrial life Extraterrestrial life, or alien life (colloquially aliens), is life that originates from another world rather than on Earth. No extraterrestrial life has yet been scientifically or conclusively detected. Such life might range from simple forms such as prokaryotes to intelligent beings, possibly bringing forth civilizations that might be far more, or far less, advanced than humans. The Drake equation speculates about the existence of sapient life elsewhere in the universe. The science of extraterrestrial life is known as astrobiology. Speculation about inhabited worlds beyond Earth dates back to antiquity. Early Christian writers, including Augustine, discussed ideas from thinkers like Democritus and Epicurus about countless worlds in the vast universe. Pre-modern writers typically assumed extraterrestrial "worlds" were inhabited by living beings. William Vorilong, in the 15th century, acknowledged the possibility Jesus could have visited extraterrestrial worlds to redeem their inhabitants.: 26 In 1440, Nicholas of Cusa suggested Earth is a "brilliant star"; he theorized that all celestial bodies, even the Sun, could host life. Descartes wrote that there were no means to prove the stars were not inhabited by "intelligent creatures", but their existence was a matter of speculation.: 67 In comparison to the life-abundant Earth, the vast majority of intrasolar and extrasolar planets and moons have harsh surface conditions and disparate atmospheric chemistry, or lack an atmosphere. However, there are many extreme and chemically harsh ecosystems on Earth that do support forms of life and are often hypothesized to be the origin of life on Earth. Examples include life surrounding hydrothermal vents, acidic hot springs, and volcanic lakes, as well as halophiles and the deep biosphere. Since the mid-20th century, researchers have searched for extraterrestrial life and intelligence. Solar system studies focus on Venus, Mars, Europa, and Titan, while exoplanet discoveries now total 6,022 confirmed planets in 4,490 systems as of October 2025. Depending on the category of search, methods range from analysis of telescope and specimen data to radios used to detect and transmit interstellar communication. Interstellar travel remains largely hypothetical, with only the Voyager 1 and Voyager 2 probes confirmed to have entered the interstellar medium. The concept of extraterrestrial life, especially intelligent life, has greatly influenced culture and fiction. A key debate centers on contacting extraterrestrial intelligence: some advocate active attempts, while others warn it could be risky, given human history of exploiting other societies. Context Initially, after the Big Bang, the universe was too hot to allow life. It is estimated that the temperature of the universe was around 10 billion Kelvin at the one-second mark. Roughly 15 million years later, it cooled to temperate levels, though the elements of organic life were yet nonexistent. The only freely available elements at that point were hydrogen and helium. Carbon and oxygen (and later, water) would not appear until 50 million years later, created through stellar fusion. At that point, the difficulty for life to appear was not the temperature, but the scarcity of free heavy elements. Planetary systems emerged, and the first organic compounds may have formed in the protoplanetary disk of dust grains that would eventually create rocky planets like Earth. Although Earth was in a molten state after its birth and may have burned any organics that fell on it, it would have been more receptive once it cooled down. Once the right conditions on Earth were met, life started by a chemical process known as abiogenesis. Alternatively, life may have formed less frequently, then spread—by meteoroids, for example—between habitable planets in a process called panspermia. During most of its stellar evolution, stars combine hydrogen nuclei to make helium nuclei by stellar fusion, and the comparatively lighter weight of helium allows the star to release the extra energy. The process continues until the star uses all of its available fuel, with the speed of consumption being related to the size of the star. During its last stages, stars start combining helium nuclei to form carbon nuclei. The larger stars can further combine carbon nuclei to create oxygen and silicon, oxygen into neon and sulfur, and so on until iron. Ultimately, the star blows much of its content back into the stellar medium, where it would join clouds that would eventually become new generations of stars and planets. Many of those materials are the raw components of life on Earth. As this process takes place in all the universe, said materials are ubiquitous in the cosmos and not a rarity from the Solar System. Earth is a planet in the Solar System, a planetary system formed by a star at the center, the Sun, and the objects that orbit it: other planets, moons, asteroids, and comets. The sun is part of the Milky Way, a galaxy. The Milky Way is part of the Local Group, a galaxy group that is in turn part of the Laniakea Supercluster. The universe is composed of all similar structures in existence. The immense distances between celestial objects are a difficulty for studying extraterrestrial life. So far, humans have only set foot on the Moon and sent robotic probes to other planets and moons in the Solar System. Although probes can withstand conditions that may be lethal to humans, the distances cause time delays: the New Horizons took nine years after launch to reach Pluto. No probe has ever reached extrasolar planetary systems. The Voyager 2 left the Solar System at a speed of 50,000 kilometers per hour; if it headed towards the Alpha Centauri system, the closest one to Earth at 4.4 light years, it would reach it in 100,000 years. Under current technology, such systems can only be studied by telescopes, which have limitations. It is estimated that dark matter has a larger amount of combined matter than stars and gas clouds, but as it plays no role in the stellar evolution of stars and planets, it is usually not taken into account by astrobiology. There is an area around a star, the circumstellar habitable zone or "Goldilocks zone", wherein water may be at the right temperature to exist in liquid form at a planetary surface. This area is neither too close to the star, where water would become steam, nor too far away, where water would be frozen as ice. However, although useful as an approximation, planetary habitability is complex and defined by several factors. Being in the habitable zone is not enough for a planet to be habitable, not even to actually have such liquid water. Venus is located in the solar system's habitable zone, but does not have liquid water because of the conditions of its atmosphere. Jovian planets or gas giants are not considered habitable even if they orbit close enough to their stars as hot Jupiters, due to crushing atmospheric pressures. The actual distances for the habitable zones vary according to the type of star, and even the solar activity of each specific star influences the local habitability. The type of star also defines the time the habitable zone will exist, as its presence and limits will change along with the star's stellar evolution. The Big Bang occurred 13.8 billion years ago, the Solar System was formed 4.6 billion years ago, and the first hominids appeared 6 million years ago. Life on other planets may have started, evolved, given birth to extraterrestrial intelligences, and perhaps even faced a planetary extinction event millions or billions of years ago. When considered from a cosmic perspective, the brief times of existence of Earth's species may suggest that extraterrestrial life may be equally fleeting under such a scale. During a period of about 7 million years, from about 10 to 17 million years after the Big Bang, the background temperature was between 373 and 273 K (100 and 0 °C; 212 and 32 °F), allowing the possibility of liquid water if any planets existed. Avi Loeb (2014) speculated that primitive life might in principle have appeared during this window, which he called "the Habitable Epoch of the Early Universe". Life on Earth is quite ubiquitous across the planet and has adapted over time to almost all the available environments in it, extremophiles and the deep biosphere thrive at even the most hostile ones. As a result, it is inferred that life in other celestial bodies may be equally adaptive. However, the origin of life is unrelated to its ease of adaptation and may have stricter requirements. A celestial body may not have any life on it, even if it were habitable. Likelihood of existence Life in the cosmos beyond Earth has been observed. The hypothesis of ubiquitous extraterrestrial life relies on three main ideas. The first one, the size of the universe, allows for plenty of planets to have a similar habitability to Earth, and the age of the universe gives enough time for a long process analog to the history of Earth to happen there. The second is that the substances that make life, such as carbon and water, are ubiquitous in the universe. The third is that the physical laws are universal, which means that the forces that would facilitate or prevent the existence of life would be the same ones as on Earth. According to this argument, made by scientists such as Carl Sagan and Stephen Hawking, it would be improbable for life not to exist somewhere else other than Earth. This argument is embodied in the Copernican principle, which states that Earth does not occupy a unique position in the Universe, and the mediocrity principle, which states that there is nothing special about life on Earth. Other authors consider instead that life in the cosmos, or at least multicellular life, may actually be rare. The Rare Earth hypothesis maintains that life on Earth is possible because of a series of factors that range from the location in the galaxy and the configuration of the Solar System to local characteristics of the planet, and that it is unlikely that another planet simultaneously meets all such requirements. The proponents of this hypothesis consider that very little evidence suggests the existence of extraterrestrial life and that, at this point, it is just a desired result and not a reasonable scientific explanation for any gathered data. In 1961, astronomer and astrophysicist Frank Drake devised the Drake equation as a way to stimulate scientific dialogue at a meeting on the search for extraterrestrial intelligence (SETI). The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy. The Drake equation is:: xix where: and Drake's proposed estimates are as follows, but numbers on the right side of the equation are agreed as speculative and open to substitution: 10,000 = 5 ⋅ 0.5 ⋅ 2 ⋅ 1 ⋅ 0.2 ⋅ 1 ⋅ 10,000 {\displaystyle 10{,}000=5\cdot 0.5\cdot 2\cdot 1\cdot 0.2\cdot 1\cdot 10{,}000} [better source needed] The Drake equation has proved controversial since, although it is written as a math equation, none of its values were known at the time. Although some values may eventually be measured, others are based on social sciences and are not knowable by their very nature. This does not allow one to make noteworthy conclusions from the equation. Based on observations from the Hubble Space Telescope, there are nearly 2 trillion galaxies in the observable universe. It is estimated that at least ten percent of all Sun-like stars have a system of planets. In other words, there are 6.25×1018 stars with planets orbiting them in the observable universe. Even if it is assumed that only one out of a billion of these stars has planets supporting life, there would be some 6.25 billion life-supporting planetary systems in the observable universe. A 2013 study based on results from the Kepler spacecraft estimated that the Milky Way contains at least as many planets as it does stars, resulting in 100–400 billion exoplanets. The Nebular hypothesis that explains the formation of the Solar System and other planetary systems would suggest that those can have several configurations, and not all of them may have rocky planets within the habitable zone. The apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilisations and the lack of evidence for such civilisations is known as the Fermi paradox. Dennis W. Sciama claimed that life's existence in the universe depends on various fundamental constants. Zhi-Wei Wang and Samuel L. Braunstein suggest that a random universe capable of supporting life is likely to be just barely able to do so, giving a potential explanation to the Fermi paradox. Biochemical basis If extraterrestrial life exists, it could range from simple microorganisms and multicellular organisms similar to animals or plants, to complex alien intelligences akin to humans. When scientists talk about extraterrestrial life, they consider all those types. Although it is possible that extraterrestrial life may have other configurations, scientists use the hierarchy of lifeforms from Earth for simplicity, as it is the only one known to exist. The first basic requirement for life is an environment with non-equilibrium thermodynamics, which means that the thermodynamic equilibrium must be broken by a source of energy. The traditional sources of energy in the cosmos are the stars, such as for life on Earth, which depends on the energy of the sun. However, there are other alternative energy sources, such as volcanoes, plate tectonics, and hydrothermal vents. There are ecosystems on Earth in deep areas of the ocean that do not receive sunlight, and take energy from black smokers instead. Magnetic fields and radioactivity have also been proposed as sources of energy, although they would be less efficient ones. Life on Earth requires water in a liquid state as a solvent in which biochemical reactions take place. It is highly unlikely that an abiogenesis process can start within a gaseous or solid medium: the atom speeds, either too fast or too slow, make it difficult for specific ones to meet and start chemical reactions. A liquid medium also allows the transport of nutrients and substances required for metabolism. Sufficient quantities of carbon and other elements, along with water, might enable the formation of living organisms on terrestrial planets with a chemical make-up and temperature range similar to that of Earth. Life based on ammonia rather than water has been suggested as an alternative, though this solvent appears less suitable than water. It is also conceivable that there are forms of life whose solvent is a liquid hydrocarbon, such as methane, ethane or propane. Another unknown aspect of potential extraterrestrial life would be the chemical elements that would compose it. Life on Earth is largely composed of carbon, but there could be other hypothetical types of biochemistry. A replacement for carbon would need to be able to create complex molecules, store information required for evolution, and be freely available in the medium. To create DNA, RNA, or a close analog, such an element should be able to bind its atoms with many others, creating complex and stable molecules. It should be able to create at least three covalent bonds: two for making long strings and at least a third to add new links and allow for diverse information. Only nine elements meet this requirement: boron, nitrogen, phosphorus, arsenic, antimony (three bonds), carbon, silicon, germanium and tin (four bonds). As for abundance, carbon, nitrogen, and silicon are the most abundant ones in the universe, far more than the others. On Earth's crust the most abundant of those elements is silicon, in the Hydrosphere it is carbon and in the atmosphere, it is carbon and nitrogen. Silicon, however, has disadvantages over carbon. The molecules formed with silicon atoms are less stable, and more vulnerable to acids, oxygen, and light. An ecosystem of silicon-based lifeforms would require very low temperatures, high atmospheric pressure, an atmosphere devoid of oxygen, and a solvent other than water. The low temperatures required would add an extra problem, the difficulty to kickstart a process of abiogenesis to create life in the first place. Norman Horowitz, head of the Jet Propulsion Laboratory bioscience section for the Mariner and Viking missions from 1965 to 1976 considered that the great versatility of the carbon atom makes it the element most likely to provide solutions, even exotic solutions, to the problems of survival of life on other planets. However, he also considered that the conditions found on Mars were incompatible with carbon based life. Even if extraterrestrial life is based on carbon and uses water as a solvent, like Earth life, it may still have a radically different biochemistry. Life is generally considered to be a product of natural selection. It has been proposed that to undergo natural selection a living entity must have the capacity to replicate itself, the capacity to avoid damage/decay, and the capacity to acquire and process resources in support of the first two capacities. Life on Earth may have started with an RNA world and later evolved to its current form, where some of the RNA tasks were transferred to DNA and proteins. Extraterrestrial life may still be stuck using RNA, or evolve into other configurations. It is unclear if our biochemistry is the most efficient one that could be generated, or which elements would follow a similar pattern. However, it is likely that, even if cells had a different composition to those from Earth, they would still have a cell membrane. Life on Earth jumped from prokaryotes to eukaryotes and from unicellular organisms to multicellular organisms through evolution. So far no alternative process to achieve such a result has been conceived, even if hypothetical. Evolution requires life to be divided into individual organisms, and no alternative organisation has been satisfactorily proposed either. At the basic level, membranes define the limit of a cell, between it and its environment, while remaining partially open to exchange energy and resources with it. The evolution from simple cells to eukaryotes, and from them to multicellular lifeforms, is not guaranteed. The Cambrian explosion took place thousands of millions of years after the origin of life, and its causes are not fully known yet. On the other hand, the jump to multicellularity took place several times, which suggests that it could be a case of convergent evolution, and so likely to take place on other planets as well. Palaeontologist Simon Conway Morris considers that convergent evolution would lead to kingdoms similar to our plants and animals, and that many features are likely to develop in alien animals as well, such as bilateral symmetry, limbs, digestive systems and heads with sensory organs. Scientists from the University of Oxford analysed it from the perspective of evolutionary theory and wrote in a study in the International Journal of Astrobiology that aliens may be similar to humans. The planetary context would also have an influence: a planet with higher gravity would have smaller animals, and other types of stars can lead to non-green photosynthesizers. The amount of energy available would also affect biodiversity, as an ecosystem sustained by black smokers or hydrothermal vents would have less energy available than those sustained by a star's light and heat, and so its lifeforms would not grow beyond a certain complexity. There is also research in assessing the capacity of life for developing intelligence. It has been suggested that this capacity arises with the number of potential niches a planet contains, and that the complexity of life itself is reflected in the information density of planetary environments, which in turn can be computed from its niches. It is common knowledge that the conditions on other planets in the solar system, in addition to the many galaxies outside of the Milky Way galaxy, are very harsh and seem to be too extreme to harbor any life. The environmental conditions on these planets can have intense UV radiation paired with extreme temperatures, lack of water, and much more that can lead to conditions that don't seem to favor the creation or maintenance of extraterrestrial life. However, there has been much historical evidence that some of the earliest and most basic forms of life on Earth originated in some extreme environments that seem unlikely to have harbored life at least at one point in Earth's history. Fossil evidence as well as many historical theories backed up by years of research and studies have marked environments like hydrothermal vents or acidic hot springs as some of the first places that life could have originated on Earth. These environments can be considered extreme when compared to the typical ecosystems that the majority of life on Earth now inhabit, as hydrothermal vents are scorching hot due to the magma escaping from the Earth's mantle and meeting the much colder oceanic water. Even in today's world, there can be a diverse population of bacteria found inhabiting the area surrounding these hydrothermal vents which can suggest that some form of life can be supported even in the harshest of environments like the other planets in the solar system. The aspects of these harsh environments that make them ideal for the origin of life on Earth, as well as the possibility of creation of life on other planets, is the chemical reactions forming spontaneously. For example, the hydrothermal vents found on the ocean floor are known to support many chemosynthetic processes which allow organisms to utilize energy through reduced chemical compounds that fix carbon. In return, these reactions will allow for organisms to live in relatively low oxygenated environments while maintaining enough energy to support themselves. The early Earth environment was reducing and therefore, these carbon fixing compounds were necessary for the survival and possible origin of life on Earth. With the little amount of information that scientists have found regarding the atmosphere on other planets in the Milky Way galaxy and beyond, the atmospheres are most likely reducing or with very low oxygen levels, especially when compared with Earth's atmosphere. If there were the necessary elements and ions on these planets, the same carbon fixing, reduced chemical compounds occurring around hydrothermal vents could also occur on these planets' surfaces and possibly result in the origin of extraterrestrial life. Planetary habitability in the Solar System The Solar System has a wide variety of planets, dwarf planets, and moons, and each one is studied for its potential to host life. Each one has its own specific conditions that may benefit or harm life. So far, the only lifeforms found are those from Earth. No extraterrestrial intelligence other than humans exists or has ever existed within the Solar System. Astrobiologist Mary Voytek points out that it would be unlikely to find large ecosystems, as they would have already been detected by now. The inner Solar System is likely devoid of life. However, Venus is still of interest to astrobiologists, as it is a terrestrial planet that was likely similar to Earth in its early stages and developed in a different way. There is a greenhouse effect, the surface is the hottest in the Solar System, sulfuric acid clouds, all surface liquid water is lost, and it has a thick carbon-dioxide atmosphere with huge pressure. Comparing both helps to understand the precise differences that lead to beneficial or harmful conditions for life. And despite the conditions against life on Venus, there are suspicions that microbial life-forms may still survive in high-altitude clouds. Mars is a cold and almost airless desert, inhospitable to life. However, recent studies revealed that water on Mars used to be quite abundant, forming rivers, lakes, and perhaps even oceans. Mars may have been habitable back then, and life on Mars may have been possible. But when the planetary core ceased to generate a magnetic field, solar winds removed the atmosphere and the planet became vulnerable to solar radiation. Ancient life-forms may still have left fossilised remains, and microbes may still survive deep underground. As mentioned, the gas giants and ice giants are unlikely to contain life. The most distant solar system bodies, found in the Kuiper Belt and outwards, are locked in permanent deep-freeze, but cannot be ruled out completely. Although the giant planets themselves are highly unlikely to have life, there is much hope to find it on moons orbiting these planets. Europa, from the Jovian system, has a subsurface ocean below a thick layer of ice. Ganymede and Callisto also have subsurface oceans, but life is less likely in them because water is sandwiched between layers of solid ice. Europa would have contact between the ocean and the rocky surface, which helps the chemical reactions. It may be difficult to dig so deep in order to study those oceans, though. Enceladus, a tiny moon of Saturn with another subsurface ocean, may not need to be dug, as it releases water to space in eruption columns. The space probe Cassini flew inside one of these, but could not make a full study because NASA did not expect this phenomenon and did not equip the probe to study ocean water. Still, Cassini detected complex organic molecules, salts, evidence of hydrothermal activity, hydrogen, and methane. Titan is the only celestial body in the Solar System besides Earth that has liquid bodies on the surface. It has rivers, lakes, and rain of hydrocarbons, methane, and ethane, and even a cycle similar to Earth's water cycle. This special context encourages speculations about lifeforms with different biochemistry, but the cold temperatures would make such chemistry take place at a very slow pace. Water is rock-solid on the surface, but Titan does have a subsurface water ocean like several other moons. However, it is of such a great depth that it would be very difficult to access it for study. Scientific search The science that searches and studies life in the universe, both on Earth and elsewhere, is called astrobiology. With the study of Earth's life, the only known form of life, astrobiology seeks to study how life starts and evolves and the requirements for its continuous existence. This helps to determine what to look for when searching for life in other celestial bodies. This is a complex area of study, and uses the combined perspectives of several scientific disciplines, such as astronomy, biology, chemistry, geology, oceanography, and atmospheric sciences. The scientific search for extraterrestrial life is being carried out both directly and indirectly. As of September 2017[update], 3,667 exoplanets in 2,747 systems have been identified, and other planets and moons in the Solar System hold the potential for hosting primitive life such as microorganisms. As of 8 February 2021, an updated status of studies considering the possible detection of lifeforms on Venus (via phosphine) and Mars (via methane) was reported. Scientists search for biosignatures within the Solar System by studying planetary surfaces and examining meteorites. Some claim to have identified evidence that microbial life has existed on Mars. In 1996, a controversial report stated that structures resembling nanobacteria were discovered in a meteorite, ALH84001, formed of rock ejected from Mars. Although all the unusual properties of the meteorite were eventually explained as the result of inorganic processes, the controversy over its discovery laid the groundwork for the development of astrobiology. An experiment on the two Viking Mars landers reported gas emissions from heated Martian soil samples that some scientists argue are consistent with the presence of living microorganisms. Lack of corroborating evidence from other experiments on the same samples suggests that a non-biological reaction is a more likely hypothesis. In February 2005 NASA scientists reported they may have found some evidence of extraterrestrial life on Mars. The two scientists, Carol Stoker and Larry Lemke of NASA's Ames Research Center, based their claim on methane signatures found in Mars's atmosphere resembling the methane production of some forms of primitive life on Earth, as well as on their own study of primitive life near the Rio Tinto river in Spain. NASA officials soon distanced NASA from the scientists' claims, and Stoker herself backed off from her initial assertions. In November 2011, NASA launched the Mars Science Laboratory that landed the Curiosity rover on Mars. It is designed to assess the past and present habitability on Mars using a variety of scientific instruments. The rover landed on Mars at Gale Crater in August 2012. A group of scientists at Cornell University started a catalog of microorganisms, with the way each one reacts to sunlight. The goal is to help with the search for similar organisms in exoplanets, as the starlight reflected by planets rich in such organisms would have a specific spectrum, unlike that of starlight reflected from lifeless planets. If Earth was studied from afar with this system, it would reveal a shade of green, as a result of the abundance of plants with photosynthesis. In August 2011, NASA studied meteorites found on Antarctica, finding adenine, guanine, hypoxanthine, and xanthine. Adenine and guanine are components of DNA, and the others are used in other biological processes. The studies ruled out pollution of the meteorites on Earth, as those components would not be freely available the way they were found in the samples. This discovery suggests that several organic molecules that serve as building blocks of life may be generated within asteroids and comets. In October 2011, scientists reported that cosmic dust contains complex organic compounds ("amorphous organic solids with a mixed aromatic-aliphatic structure") that could be created naturally, and rapidly, by stars. It is still unclear if those compounds played a role in the creation of life on Earth, but Sun Kwok, of the University of Hong Kong, thinks so. "If this is the case, life on Earth may have had an easier time getting started as these organics can serve as basic ingredients for life." In August 2012, and in a world first, astronomers at Copenhagen University reported the detection of a specific sugar molecule, glycolaldehyde, in a distant star system. The molecule was found around the protostellar binary IRAS 16293-2422, which is located 400 light years from Earth. Glycolaldehyde is needed to form ribonucleic acid, or RNA, which is similar in function to DNA. This finding suggests that complex organic molecules may form in stellar systems prior to the formation of planets, eventually arriving on young planets early in their formation. In December 2023, astronomers reported the first time discovery, in the plumes of Enceladus, moon of the planet Saturn, of hydrogen cyanide, a possible chemical essential for life as we know it, as well as other organic molecules, some of which are yet to be better identified and understood. According to the researchers, "these [newly discovered] compounds could potentially support extant microbial communities or drive complex organic synthesis leading to the origin of life." Although most searches are focused on the biology of extraterrestrial life, an extraterrestrial intelligence capable enough to develop a civilization may be detectable by other means as well. Technology may generate technosignatures, effects on the native planet that may not be caused by natural causes. There are three main types of techno-signatures considered: interstellar communications, effects on the atmosphere, and planetary-sized structures such as Dyson spheres. Organizations such as the SETI Institute search the cosmos for potential forms of communication. They started with radio waves, and now search for laser pulses as well. The challenge for this search is that there are natural sources of such signals as well, such as gamma-ray bursts and supernovae, and the difference between a natural signal and an artificial one would be in its specific patterns. Astronomers intend to use artificial intelligence for this, as it can manage large amounts of data and is devoid of biases and preconceptions. Besides, even if there is an advanced extraterrestrial civilization, there is no guarantee that it is transmitting radio communications in the direction of Earth. The length of time required for a signal to travel across space means that a potential answer may arrive decades or centuries after the initial message. The atmosphere of Earth is rich in nitrogen dioxide as a result of air pollution, which can be detectable. The natural abundance of carbon, which is also relatively reactive, makes it likely to be a basic component of the development of a potential extraterrestrial technological civilization, as it is on Earth. Fossil fuels may likely be generated and used on such worlds as well. The abundance of chlorofluorocarbons in the atmosphere can also be a clear technosignature, considering their role in ozone depletion. Light pollution may be another technosignature, as multiple lights on the night side of a rocky planet can be a sign of advanced technological development. However, modern telescopes are not strong enough to study exoplanets with the required level of detail to perceive it. The Kardashev scale proposes that a civilization may eventually start consuming energy directly from its local star. This would require giant structures built next to it, called Dyson spheres. Those speculative structures would cause an excess infrared radiation, that telescopes may notice. The infrared radiation is typical of young stars, surrounded by dusty protoplanetary disks that will eventually form planets. An older star such as the Sun would have no natural reason to have excess infrared radiation. The presence of heavy elements in a star's light-spectrum is another potential biosignature; such elements would (in theory) be found if the star were being used as an incinerator/repository for nuclear waste products. Some astronomers search for extrasolar planets that may be conducive to life, narrowing the search to terrestrial planets within the habitable zones of their stars. Since 1992, over four thousand exoplanets have been discovered (6,128 planets in 4,584 planetary systems including 1,017 multiple planetary systems as of 30 October 2025). The extrasolar planets so far discovered range in size from that of terrestrial planets similar to Earth's size to that of gas giants larger than Jupiter. The number of observed exoplanets is expected to increase greatly in the coming years.[better source needed] The Kepler space telescope has also detected a few thousand candidate planets, of which about 11% may be false positives. There is at least one planet on average per star. About 1 in 5 Sun-like stars[a] have an "Earth-sized"[b] planet in the habitable zone,[c] with the nearest expected to be within 12 light-years distance from Earth. Assuming 200 billion stars in the Milky Way,[d] that would be 11 billion potentially habitable Earth-sized planets in the Milky Way, rising to 40 billion if red dwarfs are included. The rogue planets in the Milky Way possibly number in the trillions. The nearest known exoplanet is Proxima Centauri b, located 4.2 light-years (1.3 pc) from Earth in the southern constellation of Centaurus. As of March 2014[update], the least massive exoplanet known is PSR B1257+12 A, which is about twice the mass of the Moon. The most massive planet listed on the NASA Exoplanet Archive is DENIS-P J082303.1−491201 b, about 29 times the mass of Jupiter, although according to most definitions of a planet, it is too massive to be a planet and may be a brown dwarf instead. Almost all of the planets detected so far are within the Milky Way, but there have also been a few possible detections of extragalactic planets. The study of planetary habitability also considers a wide range of other factors in determining the suitability of a planet for hosting life. One sign that a planet probably already contains life is the presence of an atmosphere with significant amounts of oxygen, since that gas is highly reactive and generally would not last long without constant replenishment. This replenishment occurs on Earth through photosynthetic organisms. One way to analyse the atmosphere of an exoplanet is through spectrography when it transits its star, though this might only be feasible with dim stars like white dwarfs. History and cultural impact The modern concept of extraterrestrial life is based on assumptions that were not commonplace during the early days of astronomy. The first explanations for the celestial objects seen in the night sky were based on mythology. Scholars from Ancient Greece were the first to consider that the universe is inherently understandable and rejected explanations based on supernatural incomprehensible forces, such as the myth of the Sun being pulled across the sky in the chariot of Apollo. They had not developed the scientific method yet and based their ideas on pure thought and speculation, but they developed precursor ideas to it, such as that explanations had to be discarded if they contradict observable facts. The discussions of those Greek scholars established many of the pillars that would eventually lead to the idea of extraterrestrial life, such as Earth being round and not flat. The cosmos was first structured in a geocentric model that considered that the sun and all other celestial bodies revolve around Earth. However, they did not consider them as worlds. In Greek understanding, the world was composed by both Earth and the celestial objects with noticeable movements. Anaximander thought that the cosmos was made from apeiron, a substance that created the world, and that the world would eventually return to the cosmos. Eventually two groups emerged, the atomists that thought that matter at both Earth and the cosmos was equally made of small atoms of the classical elements (earth, water, fire and air), and the Aristotelians who thought that those elements were exclusive of Earth and that the cosmos was made of a fifth one, the aether. Atomist Epicurus thought that the processes that created the world, its animals and plants should have created other worlds elsewhere, along with their own animals and plants. Aristotle thought instead that all the earth element naturally fell towards the center of the universe, and that would make it impossible for other planets to exist elsewhere. Under that reasoning, Earth was not only in the center, it was also the only planet in the universe. Cosmic pluralism, the plurality of worlds, or simply pluralism, describes the philosophical belief in numerous "worlds" in addition to Earth, which might harbor extraterrestrial life. The earliest recorded assertion of extraterrestrial human life is found in ancient scriptures of Jainism. There are multiple "worlds" mentioned in Jain scriptures that support human life. These include, among others, Bharat Kshetra, Mahavideh Kshetra, Airavat Kshetra, and Hari kshetra. Medieval Muslim writers like Fakhr al-Din al-Razi and Muhammad al-Baqir supported cosmic pluralism on the basis of the Qur'an. Chaucer's poem The House of Fame engaged in medieval thought experiments that postulated the plurality of worlds. However, those ideas about other worlds were different from the current knowledge about the structure of the universe, and did not postulate the existence of planetary systems other than the Solar System. When those authors talk about other worlds, they talk about places located at the center of their own systems, and with their own stellar vaults and cosmos surrounding them. The Greek ideas and the disputes between atomists and Aristotelians outlived the fall of the Greek empire. The Great Library of Alexandria compiled information about it, part of which was translated by Islamic scholars and thus survived the end of the Library. Baghdad combined the knowledge of the Greeks, the Indians, the Chinese and its own scholars, and the knowledge expanded through the Byzantine Empire. From there it eventually returned to Europe by the time of the Middle Ages. However, as the Greek atomist doctrine held that the world was created by random movements of atoms, with no need for a creator deity, it became associated with atheism, and the dispute intertwined with religious ones. Still, the Church did not react to those topics in a homogeneous way, and there were stricter and more permissive views within the church itself. The first known mention of the term 'panspermia' was in the writings of the 5th-century BC Greek philosopher Anaxagoras. He proposed the idea that life exists everywhere. By the time of the late Middle Ages there were many known inaccuracies in the geocentric model, but it was kept in use because naked eye observations provided limited data. Nicolaus Copernicus started the Copernican Revolution by proposing that the planets revolve around the sun rather than Earth. His proposal had little acceptance at first because, as he kept the assumption that orbits were perfect circles, his model led to as many inaccuracies as the geocentric one. Tycho Brahe improved the available data with naked-eye observatories, which worked with highly complex sextants and quadrants. Tycho could not make sense of his observations, but Johannes Kepler did: orbits were not perfect circles, but ellipses. This knowledge benefited the Copernican model, which worked now almost perfectly. The invention of the telescope a short time later, perfected by Galileo Galilei, clarified the final doubts, and the paradigm shift was completed. Under this new understanding, the notion of extraterrestrial life became feasible: if Earth is but just a planet orbiting around a star, there may be planets similar to Earth elsewhere. The astronomical study of distant bodies also proved that physical laws are the same elsewhere in the universe as on Earth, with nothing making the planet truly special. The new ideas were met with resistance from the Catholic church. Galileo was tried for the heliocentric model, which was considered heretical, and forced to recant it. The best-known early-modern proponent of ideas of extraterrestrial life was the Italian philosopher Giordano Bruno, who argued in the 16th century for an infinite universe in which every star is surrounded by its own planetary system. Bruno wrote that other worlds "have no less virtue nor a nature different to that of our earth" and, like Earth, "contain animals and inhabitants". Bruno's belief in the plurality of worlds was one of the charges leveled against him by the Venetian Holy Inquisition, which tried and executed him. The heliocentric model was further strengthened by the postulation of the theory of gravity by Sir Isaac Newton. This theory provided the mathematics that explains the motions of all things in the universe, including planetary orbits. By this point, the geocentric model was definitely discarded. By this time, the use of the scientific method had become a standard, and new discoveries were expected to provide evidence and rigorous mathematical explanations. Science also took a deeper interest in the mechanics of natural phenomena, trying to explain not just the way nature works but also the reasons for working that way. There was very little actual discussion about extraterrestrial life before this point, as the Aristotelian ideas remained influential while geocentrism was still accepted. When it was finally proved wrong, it not only meant that Earth was not the center of the universe, but also that the lights seen in the sky were not just lights, but physical objects. The notion that life may exist in them as well soon became an ongoing topic of discussion, although one with no practical ways to investigate. The possibility of extraterrestrials remained a widespread speculation as scientific discovery accelerated. William Herschel, the discoverer of Uranus, was one of many 18th–19th-century astronomers who believed that the Solar System is populated by alien life. Other scholars of the period who championed "cosmic pluralism" included Immanuel Kant and Benjamin Franklin. At the height of the Enlightenment, even the Sun and Moon were considered candidates for extraterrestrial inhabitants. Speculation about life on Mars increased in the late 19th century, following telescopic observation of apparent Martian canals – which soon, however, turned out to be optical illusions. Despite this, in 1895, American astronomer Percival Lowell published his book Mars, followed by Mars and its Canals in 1906, proposing that the canals were the work of a long-gone civilisation. Spectroscopic analysis of Mars's atmosphere began in earnest in 1894, when U.S. astronomer William Wallace Campbell showed that neither water nor oxygen was present in the Martian atmosphere. By 1909 better telescopes and the best perihelic opposition of Mars since 1877 conclusively put an end to the canal hypothesis. As a consequence of the belief in the spontaneous generation there was little thought about the conditions of each celestial body: it was simply assumed that life would thrive anywhere. This theory was disproved by Louis Pasteur in the 19th century. Popular belief in thriving alien civilisations elsewhere in the solar system still remained strong until Mariner 4 and Mariner 9 provided close images of Mars, which debunked forever the idea of the existence of Martians and decreased the previous expectations of finding alien life in general. The end of the spontaneous generation belief forced investigation into the origin of life. Although abiogenesis is the more accepted theory, a number of authors reclaimed the term "panspermia" and proposed that life was brought to Earth from elsewhere. Some of those authors are Jöns Jacob Berzelius (1834), Kelvin (1871), Hermann von Helmholtz (1879) and, somewhat later, by Svante Arrhenius (1903). The science fiction genre, although not so named during the time, developed during the late 19th century. The expansion of the genre of extraterrestrials in fiction influenced the popular perception over the real-life topic, making people eager to jump to conclusions about the discovery of aliens. Science marched at a slower pace, some discoveries fueled expectations and others dashed excessive hopes. For example, with the advent of telescopes, most structures seen on the Moon or Mars were immediately attributed to Selenites or Martians, and later ones (such as more powerful telescopes) revealed that all such discoveries were natural features. A famous case is the Cydonia region of Mars, first imaged by the Viking 1 orbiter. The low-resolution photos showed a rock formation that resembled a human face, but later spacecraft took photos in higher detail that showed that there was nothing special about the site. The search and study of extraterrestrial life became a science of its own, astrobiology. Also known as exobiology, this discipline is studied by the NASA, the ESA, the INAF, and others. Astrobiology studies life from Earth as well, but with a cosmic perspective. For example, abiogenesis is of interest to astrobiology, not because of the origin of life on Earth, but for the chances of a similar process taking place in other celestial bodies. Many aspects of life, from its definition to its chemistry, are analyzed as either likely to be similar in all forms of life across the cosmos or only native to Earth. Astrobiology, however, remains constrained by the current lack of extraterrestrial life-forms to study, as all life on Earth comes from the same ancestor, and it is hard to infer general characteristics from a group with a single example to analyse. The 20th century came with great technological advances, speculations about future hypothetical technologies, and an increased basic knowledge of science by the general population thanks to science divulgation through the mass media. The public interest in extraterrestrial life and the lack of discoveries by mainstream science led to the emergence of pseudosciences that provided affirmative, if questionable, answers to the existence of aliens. Ufology claims that many unidentified flying objects (UFOs) would be spaceships from alien species, and ancient astronauts hypothesis claim that aliens would have visited Earth in antiquity and prehistoric times but people would have failed to understand it by then. Most UFOs or UFO sightings can be readily explained as sightings of Earth-based aircraft (including top-secret aircraft), known astronomical objects or weather phenomenons, or as hoaxes. Looking beyond the pseudosciences, Lewis White Beck strove to elevate the level of public discourse on the topic of extraterrestrial life by tracing the evolution of philosophical thought over the centuries from ancient times into the modern era. His review of the contributions made by Lucretius, Plutarch, Aristotle, Copernicus, Immanuel Kant, John Wilkins, Charles Darwin and Karl Marx demonstrated that even in modern times, humanity could be profoundly influenced in its search for extraterrestrial life by subtle and comforting archetypal ideas which are largely derived from firmly held religious, philosophical and existential belief systems. On a positive note, however, Beck further argued that even if the search for extraterrestrial life proves to be unsuccessful, the endeavor itself could have beneficial consequences by assisting humanity in its attempt to actualize superior ways of living here on Earth. By the 21st century, it was accepted that multicellular life in the Solar System can only exist on Earth, but the interest in extraterrestrial life increased regardless. This is a result of the advances in several sciences. The knowledge of planetary habitability allows to consider on scientific terms the likelihood of finding life at each specific celestial body, as it is known which features are beneficial and harmful for life. Astronomy and telescopes also improved to the point exoplanets can be confirmed and even studied, increasing the number of search places. Life may still exist elsewhere in the Solar System in unicellular form, but the advances in spacecraft allow to send robots to study samples in situ, with tools of growing complexity and reliability. Although no extraterrestrial life has been found and life may still be just a rarity from Earth, there are scientific reasons to suspect that it can exist elsewhere, and technological advances that may detect it if it does. Many scientists are optimistic about the chances of finding alien life. In the words of SETI's Frank Drake, "All we know for sure is that the sky is not littered with powerful microwave transmitters". Drake noted that it is entirely possible that advanced technology results in communication being carried out in some way other than conventional radio transmission. At the same time, the data returned by space probes, and giant strides in detection methods, have allowed science to begin delineating habitability criteria on other worlds, and to confirm that at least other planets are plentiful, though aliens remain a question mark. The Wow! signal, detected in 1977 by a SETI project, remains a subject of speculative debate. On the other hand, other scientists are pessimistic. Jacques Monod wrote that "Man knows at last that he is alone in the indifferent immensity of the universe, whence which he has emerged by chance". In 2000, geologist and paleontologist Peter Ward and astrobiologist Donald Brownlee published a book entitled Rare Earth: Why Complex Life is Uncommon in the Universe.[better source needed] In it, they discussed the Rare Earth hypothesis, in which they claim that Earth-like life is rare in the universe, whereas microbial life is common. Ward and Brownlee are open to the idea of evolution on other planets that is not based on essential Earth-like characteristics such as DNA and carbon. As for the possible risks, theoretical physicist Stephen Hawking warned in 2010 that humans should not try to contact alien life forms. He warned that aliens might pillage Earth for resources. "If aliens visit us, the outcome would be much as when Columbus landed in America, which didn't turn out well for the Native Americans", he said. Jared Diamond had earlier expressed similar concerns. On 20 July 2015, Hawking and Russian billionaire Yuri Milner, along with the SETI Institute, announced a well-funded effort, called the Breakthrough Initiatives, to expand efforts to search for extraterrestrial life. The group contracted the services of the 100-meter Robert C. Byrd Green Bank Telescope in West Virginia in the United States and the 64-meter Parkes Telescope in New South Wales, Australia. On 13 February 2015, scientists (including Geoffrey Marcy, Seth Shostak, Frank Drake and David Brin) at a convention of the American Association for the Advancement of Science, discussed Active SETI and whether transmitting a message to possible intelligent extraterrestrials in the Cosmos was a good idea; one result was a statement, signed by many, that a "worldwide scientific, political and humanitarian discussion must occur before any message is sent". Government responses The 1967 Outer Space Treaty and the 1979 Moon Agreement define rules of planetary protection against potentially hazardous extraterrestrial life. COSPAR also provides guidelines for planetary protection. A committee of the United Nations Office for Outer Space Affairs had in 1977 discussed for a year strategies for interacting with extraterrestrial life or intelligence. The discussion ended without any conclusions. As of 2010, the UN lacks response mechanisms for the case of an extraterrestrial contact. One of the NASA divisions is the Office of Safety and Mission Assurance (OSMA), also known as the Planetary Protection Office. A part of its mission is to "rigorously preclude backward contamination of Earth by extraterrestrial life." In 2016, the Chinese Government released a white paper detailing its space program. According to the document, one of the research objectives of the program is the search for extraterrestrial life. It is also one of the objectives of the Chinese Five-hundred-meter Aperture Spherical Telescope (FAST) program. In 2020, Dmitry Rogozin, the head of the Russian space agency, said the search for extraterrestrial life is one of the main goals of deep space research. He also acknowledged the possibility of existence of primitive life on other planets of the Solar System. The French space agency has an office for the study of "non-identified aero spatial phenomena". The agency is maintaining a publicly accessible database of such phenomena, with over 1600 detailed entries. According to the head of the office, the vast majority of entries have a mundane explanation; but for 25% of entries, their extraterrestrial origin can neither be confirmed nor denied. In 2020, chairman of the Israel Space Agency Isaac Ben-Israel stated that the probability of detecting life in outer space is "quite large". But he disagrees with his former colleague Haim Eshed who stated that there are contacts between an advanced alien civilisation and some of Earth's governments. In fiction Although the idea of extraterrestrial peoples became feasible once astronomy developed enough to understand the nature of planets, they were not thought of as being any different from humans. Having no scientific explanation for the origin of mankind and its relation to other species, there was no reason to expect them to be any other way. This was changed by the 1859 book On the Origin of Species by Charles Darwin, which proposed the theory of evolution. Now with the notion that evolution on other planets may take other directions, science fiction authors created bizarre aliens, clearly distinct from humans. A usual way to do that was to add body features from other animals, such as insects or octopuses. Costuming and special effects feasibility alongside budget considerations forced films and TV series to tone down the fantasy, but these limitations lessened since the 1990s with the advent of computer-generated imagery (CGI), and later on as CGI became more effective and less expensive. Real-life events sometimes captivate people's imagination and this influences the works of fiction. For example, during the Barney and Betty Hill incident, the first recorded claim of an alien abduction, the couple reported that they were abducted and experimented on by aliens with oversized heads, big eyes, pale grey skin, and small noses, a description that eventually became the grey alien archetype once used in works of fiction. See also Notes References Further reading External links |
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Contents Knaanic language Knaanic (also called Canaanic, Leshon Knaan, Judaeo-Czech, Judeo-Slavic) is a tentative name for a number of West Slavic dialects or registers formerly spoken by the Jews in the lands of the Western Slavs, notably the Czech lands, but also the lands of modern Poland, Lusatia, and other Sorbian regions. They became extinct in the Late Middle Ages. Very little is known about their difference from the surrounding Slavic languages. The largest number of samples of Knaanic written in Hebrew script are in Czech; therefore, most commonly Knaanic is associated with Old Czech. Etymology The name comes from the "land of Knaan", a geo-ethnological term denoting the Jewish populations living principally in Czechia, though sometimes applied to all Jewish populations east of the Elbe River (as opposed to the Ashkenazi Jews, living to its west, or the Sephardi Jews of the Iberian Peninsula). As such, the land is often translated as simply Slavonia or Slavic Europe. The term is derived from ancient Canaan (Hebrew: כנען, kəna'an). History The language became extinct some time in the Late Middle Ages, possibly because of the expansion of the Ashkenazi culture and its own Yiddish language, descended from early Middle High German. That hypothesis is often backed by the large number of Yiddish loanwords of Slavic origin, many of which were no longer in use in Slavic languages at the time of the Ashkenazi expansion. They are believed to come from Knaanic rather than from Czech, Sorbian or Polish. The linguist Paul Wexler has hypothesised that Knaanic is actually the direct predecessor of Yiddish and that the language later became Germanised. In other words, the Knaanim, that is, the people speaking the Judaeo-Slavic languages, were the main cause of changes in Yiddish. That view has been dismissed by nearly all mainstream academics, however, and contrasts with the more widely accepted theories of Max Weinreich, who argued that Slavic loanwords were assimilated only after Yiddish had already been fully formed. The Jewish commentator Rashi was aware of this language. A possible early example of Knaanic is a 9th-century letter for a Jewish community of Ruthenia. One of the very few commonly accepted examples of Knaanic is inscriptions on bracteate coins issued under Mieszko the Old and Leszek the White, two Polish rulers of 12th and 13th century. The last evidence of usage of the language (written with the Hebrew script) comes from the 16th century. The reason that Knaanic inscriptions, which use Hebrew letters, appear on coins minted for a Polish duke is that at the time, he leased some mints to Jews. The mint masters were responsible for collecting bullion and striking coins as well as periodically taking in and restriking existing coins. The inscriptions on the coins range widely. Some are Hebrew names, possibly those of the mintmasters. Some are the names of the towns in which the mint operated, for instance Kalisz, the burial place of Mieszko the Old. Some have the duke's name. One in the National Bank of Poland's numismatic collection bears the word bracha, Hebrew for blessing. Classification In the 15th edition of Ethnologue (2005) assigned code czk to it and said that the term Knaanic is used primarily for Jewish Czech, possibly also for other Jewish variants of West Slavic languages, extinct in the Middle Ages. The 16th edition (2009) no longer lists Knaanic among the West Slavic languages. It mentioned it only as an "extinct or artificial" language without further specification and refers to the Linguist List portal. As of 2023[update] Ethnologue once again lists Knaanic as a Czech–Slovak language. See also Notes References Literature External links |
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[SOURCE: https://en.wikipedia.org/wiki/Command_line_interpreter] | [TOKENS: 7789] |
Contents Command-line interface A command-line interface (CLI), sometimes called a command-line shell, is a means of interacting with software via commands – each formatted as a line of text. Command-line interfaces emerged in the mid-1960s, on computer terminals, as an interactive and more user-friendly alternative to the non-interactive mode available with punched cards. For nearly three decades, a CLI was the most common interface for software,[disputed – discuss] but today a graphical user interface (GUI) is more common. Nonetheless, many programs such as operating system and software development utilities still provide CLI. A CLI enables automating programs since commands can be stored in a script file that can be used repeatedly. A script allows its contained commands to be executed as a group (as a single program). A CLI is made possible by command-line interpreters or command-line processors, which are programs that execute input commands. Alternatives to a CLI include a GUI (including the desktop metaphor such as Windows), text-based menuing (including DOS Shell and IBM AIX SMIT), and keyboard shortcuts. Comparison to graphical user interfaces Compared with a graphical user interface, a command-line interface requires fewer system resources to implement. Since options to commands are given in a few characters in each command line, an experienced user often finds the options easier to access. Automation of repetitive tasks is simplified by line editing and history mechanisms for storing frequently used sequences; this may extend to a scripting language that can take parameters and variable options. A command-line history can be kept, allowing review or repetition of commands. A command-line system may require paper or online manuals for the user's reference, although often a help option provides a concise review of the options of a command. The command-line environment may not provide graphical enhancements such as different fonts or extended edit windows found in a GUI. It may be difficult for a new user to become familiar with all the commands and options available, compared with the icons and drop-down menus of a graphical user interface, without reference to manuals. Types Operating system (OS) command-line interfaces are usually distinct programs supplied with the operating system. A program that implements such a text interface is often called a command-line interpreter, command processor or shell. Examples of command-line interpreters are Nushell, DEC's DIGITAL Command Language (DCL) in OpenVMS and RSX-11, the various Unix shells (sh, ksh, csh, tcsh, zsh, Bash, etc.), CP/M's CCP, DOS' COMMAND.COM, as well as the OS/2 and the Windows CMD.EXE programs, the latter groups being based heavily on DEC's RSX-11 and RSTS CLIs.[citation needed] Under most operating systems, it is possible to replace the default shell program with alternatives; examples include 4DOS for DOS, 4OS2 for OS/2, and 4NT / Take Command for Windows. Although the term shell is often used to describe a command-line interpreter, strictly speaking, a shell is a command interpreter and processor and by extension a program that provides an interface (either a user interface (command-line interface, GUI, etc...) or a programming interface) to a command interpreter and processor and to the broad capabilities of the operating system. For example, the default Windows GUI is a shell GUI named EXPLORER.EXE, as defined in the SHELL=EXPLORER.EXE line in the WIN.INI configuration file. This program strictly speaking is a shell GUI and by extension a shell (strictly speaking, the Windows shell is shell32.dll not explorer.exe which is a shell GUI for shell32.dll), but it is not a CLI (command-line interpreter) nor a shell CLI (shell command-line interface). Application programs (as opposed to operating systems) may also have command-line interfaces. An application program may support none, any, or all of these three major types of command-line interface mechanisms: Some applications support a CLI, presenting their own prompt to the user and accepting command lines. Other programs support both a CLI and a GUI. In some cases, a GUI is simply a wrapper around a separate CLI executable file. In other cases, a program may provide a CLI as an optional alternative to its GUI. CLIs and GUIs often support different functionality. For example, all features of MATLAB, a numerical analysis computer program, are available via the CLI, whereas the MATLAB GUI exposes only a subset of features. In Colossal Cave Adventure from 1975, the user uses a CLI to enter one or two words to explore a cave system. History The command-line interface evolved from a form of communication conducted by people over teleprinter (TTY) machines. Sometimes these involved sending an order or a confirmation using telex. Early computer systems often used teleprinter as the means of interaction with an operator. The mechanical teleprinter was replaced by a "glass tty", a keyboard and screen emulating the teleprinter. "Smart" terminals permitted additional functions, such as cursor movement over the entire screen, or local editing of data on the terminal for transmission to the computer. As the microcomputer revolution replaced the traditional – minicomputer + terminals – time sharing architecture, hardware terminals were replaced by terminal emulators — PC software that interpreted terminal signals sent through the PC's serial ports. These were typically used to interface an organization's new PC's with their existing mini- or mainframe computers, or to connect PC to PC. Some of these PCs were running Bulletin Board System software. Early operating system CLIs were implemented as part of resident monitor programs, and could not easily be replaced. The first implementation of the shell as a replaceable component was part of the Multics time-sharing operating system. In 1964, MIT Computation Center staff member Louis Pouzin developed the RUNCOM tool for executing command scripts while allowing argument substitution. Pouzin coined the term shell to describe the technique of using commands like a programming language, and wrote a paper about how to implement the idea in the Multics operating system. Pouzin returned to his native France in 1965, and the first Multics shell was developed by Glenda Schroeder. The first Unix shell, the V6 shell, was developed by Ken Thompson in 1971 at Bell Labs and was modeled after Schroeder's Multics shell. The Bourne shell was introduced in 1977 as a replacement for the V6 shell. Although it is used as an interactive command interpreter, it was also intended as a scripting language and contains most of the features that are commonly considered to produce structured programs. The Bourne shell led to the development of the KornShell (ksh), Almquist shell (ash), and the popular Bourne-again shell (or Bash). Early microcomputers themselves were based on a command-line interface such as CP/M, DOS or AppleSoft BASIC. During the 1980s and 1990s, the introduction of the Apple Macintosh and of Microsoft Windows on PCs saw the command line interface as the primary user interface replaced by the Graphical User Interface. The command line remained available as an alternative user interface, often used by system administrators and other advanced users for system administration, computer programming and batch processing. In November 2006, Microsoft released version 1.0 of Windows PowerShell (formerly codenamed Monad), which combined features of traditional Unix shells with their proprietary object-oriented .NET Framework. MinGW and Cygwin are open-source packages for Windows that offer a Unix-like CLI. Microsoft provides MKS Inc.'s ksh implementation MKS Korn shell for Windows through their Services for UNIX add-on. Since 2001, the Macintosh operating system macOS has been based on a Unix-like operating system called Darwin. On these computers, users can access a Unix-like command-line interface by running the terminal emulator program called Terminal, which is found in the Utilities sub-folder of the Applications folder, or by remotely logging into the machine using ssh. Z shell is the default shell for macOS; Bash, tcsh, and the KornShell are also provided. Before macOS Catalina, Bash was the default. Usage A CLI is used whenever a large vocabulary of commands or queries, coupled with a wide (or arbitrary) range of options, can be entered more rapidly as text than with a pure GUI. This is typically the case with operating system command shells. CLIs are also used by systems with insufficient resources to support a graphical user interface. Some computer language systems (such as Python, Forth, LISP, Rexx, and many dialects of BASIC) provide an interactive command-line mode to allow for rapid evaluation of code. CLIs are often used by programmers and system administrators, in engineering and scientific environments, and by technically advanced personal computer users. CLIs are also popular among people with visual disabilities since the commands and responses can be displayed using refreshable Braille displays. Anatomy of a shell CLI The general pattern of a command line is: In this format, the delimiters between command-line elements are whitespace characters and the end-of-line delimiter is the newline delimiter. This is a widely used (but not universal) convention. A CLI can generally be considered as consisting of syntax and semantics. The syntax is the grammar that all commands must follow. In the case of operating systems, DOS and Unix each define their own set of rules that all commands must follow. In the case of embedded systems, each vendor, such as Nortel, Juniper Networks or Cisco Systems, defines their own proprietary set of rules. These rules also dictate how a user navigates through the system of commands. The semantics define what sort of operations are possible, on what sort of data these operations can be performed, and how the grammar represents these operations and data—the symbolic meaning in the syntax. Two different CLIs may agree on either syntax or semantics, but it is only when they agree on both that they can be considered sufficiently similar to allow users to use both CLIs without needing to learn anything, as well as to enable re-use of scripts. A simple CLI will display a prompt, accept a command line typed by the user terminated by the Enter key, then execute the specified command and provide textual display of results or error messages. Advanced CLIs will validate, interpret and parameter-expand the command line before executing the specified command, and optionally capture or redirect its output. Unlike a button or menu item in a GUI, a command line is typically self-documenting, stating exactly what the user wants done. In addition, command lines usually include many defaults that can be changed to customize the results. Useful command lines can be saved by assigning a character string or alias to represent the full command, or several commands can be grouped to perform a more complex sequence – for instance, compile the program, install it, and run it — creating a single entity, called a command procedure or script which itself can be treated as a command. These advantages mean that a user must figure out a complex command or series of commands only once, because they can be saved, to be used again. The commands given to a CLI shell are often in one of the following forms: where doSomething is, in effect, a verb, how an adverb (for example, should the command be executed verbosely or quietly) and toFiles an object or objects (typically one or more files) on which the command should act. The > in the third example is a redirection operator, telling the command-line interpreter to send the output of the command not to its own standard output (the screen) but to the named file. This will overwrite the file. Using >> will redirect the output and append it to the file. Another redirection operator is the vertical bar (|), which creates a pipeline where the output of one command becomes the input to the next command. On some systems, such as Unix-like systems or Windows, one can modify the set of available commands by modifying which paths appear in the PATH environment variable or its equivalent. On Unix-like systems, the file containing the executable or script for a command also needs to be given execute permission. The directories in the path variable are searched in the order they are given. By re-ordering the path, one can run e.g. \OS2\MDOS\E.EXE instead of \OS2\E.EXE, when the default is the opposite. Renaming of the executables also works: people often rename their favourite editor to EDIT, for example. The command line allows one to restrict available commands, such as access to advanced internal commands. The Bourne shell and workalikes such as Bash can be run as a restricted shell; among other things, this prohibits the user from modifying the PATH environment variable, so that if PATH is set to include only directories that contain only permissible commands, the user will only be able to run those commands. The Windows CMD.EXE also supports restricting available commands. Often, shareware programs will limit the range of commands, including printing a command 'your administrator has disabled running batch files' from the prompt.[clarification needed] Some CLIs, such as those in network routers, have a hierarchy of modes, with a different set of commands supported in each mode. The set of commands are grouped by association with security, system, interface, etc. In these systems the user might traverse through a series of sub-modes. For example, if the CLI had two modes called interface and system, the user might use the command interface to enter the interface mode. At this point, commands from the system mode may not be accessible until the user exits the interface mode and enters the system mode. In IBM's flagship MVS operating systems, the Authorised Program Facility (APF) allows certain authorized programs to run with enhanced privileges, analogous to UID(0) in Unix-like systems. TSO/E supports calling, e.g., authorized commands, but only for those commands, programs and services in an installation controlled list. A command prompt (or just prompt) is a sequence of (one or more) characters used in a command-line interface to indicate readiness to accept commands. It literally prompts the user to take action. A prompt usually ends with one of the characters $, %, #, :, > or - and often includes other information, such as the path of the current working directory and the hostname. On many Unix and derivative systems, the prompt commonly ends in $ or % if the user is a normal user, but in # if the user is a superuser ("root" in Unix terminology). End-users can often modify prompts. Depending on the environment, they may include colors, special characters, and other elements (like variables and functions for the current time, user, shell number or working directory) in order, for instance, to make the prompt more informative or visually pleasing, to distinguish sessions on various machines, or to indicate the current level of nesting of commands. On some systems, special tokens in the definition of the prompt can be used to cause external programs to be called by the command-line interpreter while displaying the prompt. In DOS' COMMAND.COM and in Windows NT's cmd.exe users can modify the prompt by issuing a PROMPT command or by directly changing the value of the corresponding %PROMPT% environment variable. The default of most modern systems, the C:\> style is obtained, for instance, with PROMPT $P$G. The default of older DOS systems, C> is obtained by just PROMPT, although on some systems this produces the newer C:\> style, unless used on floppy drives A: or B:; on those systems PROMPT $N$G can be used to override the automatic default and explicitly switch to the older style. Many Unix systems feature the $PS1 variable (Prompt String 1), although other variables also may affect the prompt (depending on the shell used). In the Bash shell, a prompt of the form: could be set by issuing the command In zsh the $RPROMPT variable controls an optional prompt on the right-hand side of the display. It is not a real prompt in that the location of text entry does not change. It is used to display information on the same line as the prompt, but right-justified. In RISC OS the command prompt is a * symbol, and thus (OS) CLI commands are often referred to as star commands. One can also access the same commands from other command lines (such as the BBC BASIC command line), by preceding the command with a *. In IBM's TSO, the command prompt is referred to as the READY prompt, after the word READY in the prompt. Some shells, such as Bash, zsh, and PowerShell, allow the use of prompt systems that display a lot more information in the command prompt, like the type of remote connection, the state of machine sensors, or additional information about a version control system. They often use several ANSI colors, Unicode characters, and advanced shell features to set up a colorful display. A command-line argument or parameter is an item of information provided to a program when it is started. A program can have many command-line arguments that identify sources or destinations of information, or that alter the operation of the program. When a command processor is active a program is typically invoked by typing its name followed by command-line arguments (if any). For example, in Unix and Unix-like environments, an example of a command-line argument is: file.s is a command-line argument which tells the program rm to remove the file named file.s. Some programming languages, such as C, C++ and Java, allow a program to interpret the command-line arguments by handling them as string parameters in the main function. Other languages, such as Python, expose operating system specific API (functionality) through sys module, and in particular sys.argv for command-line arguments. In Unix-like operating systems, a single hyphen used in place of a file name is a special value specifying that a program should handle data coming from the standard input or send data to the standard output. A command-line option or simply option (also known as a flag or switch) modifies the operation of a command; the effect is determined by the command's program. Options follow the command name on the command line, separated by, e.g., commas, spaces. Separators are not always required, such as Dir/? and DIR /? in DOS, which have the same effect of listing the DIR command's available options, whereas dir --help (in many versions of Unix) does require the option to be preceded by at least one space (and is case-sensitive). The format of options varies widely between operating systems. In most cases, the syntax is by convention rather than an operating system requirement; the entire command line is simply a string passed to a program, which can process it in any way the programmer wants, so long as the interpreter can tell where the command name ends and its arguments and options begin. A few representative samples of command-line options, most relating to listing files in a directory, to illustrate some conventions: Command-line argument parsing is used to parse the arguments of a program, and such functionality is offered in various languages. For example, getopt() is in the C POSIX library for parsing arguments. In Multics, command-line options and subsystem keywords may be abbreviated. This idea appears to derive from the PL/I programming language, with its shortened keywords (e.g., STRG for STRINGRANGE and DCL for DECLARE). For example, in the Multics forum subsystem, the -long_subject parameter can be abbreviated -lgsj. It is also common for Multics commands to be abbreviated, typically corresponding to the initial letters of the words that are strung together with underscores to form command names, such as the use of did for delete_iacl_dir. In some other systems abbreviations are automatic, such as permitting enough of the first characters of a command name to uniquely identify it (such as SU as an abbreviation for SUPERUSER) while others may have some specific abbreviations pre-programmed (e.g. MD for MKDIR in COMMAND.COM) or user-defined via batch scripts and aliases (e.g. alias md mkdir in tcsh). On DOS, OS/2 and Windows, different programs called from their COMMAND.COM or CMD.EXE (or internal their commands) may use different syntax within the same operating system. For example: In DOS, OS/2 and Windows, the forward slash (/) is most prevalent, although the hyphen-minus is also sometimes used. In many versions of DOS (MS-DOS/PC DOS 2.xx and higher, all versions of DR-DOS since 5.0, as well as PTS-DOS, Embedded DOS, FreeDOS and RxDOS) the switch character (sometimes abbreviated switchar or switchchar) to be used is defined by a value returned from a system call (INT 21h/AX=3700h). The default character returned by this API is /, but can be changed to a hyphen-minus on the above-mentioned systems, except for under Datalight ROM-DOS and MS-DOS/PC DOS 5.0 and higher, which always return / from this call (unless one of many available TSRs to reenable the SwitChar feature is loaded). In some of these systems (MS-DOS/PC DOS 2.xx, DOS Plus 2.1, DR-DOS 7.02 and higher, PTS-DOS, Embedded DOS, FreeDOS and RxDOS), the setting can also be pre-configured by a SWITCHAR directive in CONFIG.SYS. General Software's Embedded DOS provides a SWITCH command for the same purpose, whereas 4DOS allows the setting to be changed via SETDOS /W:n. Under DR-DOS, if the setting has been changed from /, the first directory separator \ in the display of the PROMPT parameter $G will change to a forward slash / (which is also a valid directory separator in DOS, FlexOS, 4680 OS, 4690 OS, OS/2 and Windows) thereby serving as a visual clue to indicate the change. Also, the current setting is reflected also in the built-in help screens. Some versions of DR-DOS COMMAND.COM also support a PROMPT token $/ to display the current setting. COMMAND.COM since DR-DOS 7.02 also provides a pseudo-environment variable named %/% to allow portable batchjobs to be written. Several external DR-DOS commands additionally support an environment variable %SWITCHAR% to override the system setting. However, many programs are hardwired to use / only, rather than retrieving the switch setting before parsing command-line arguments. A very small number, mainly ports from Unix-like systems, are programmed to accept - even if the switch character is not set to it (for example netstat and ping, supplied with Microsoft Windows, will accept the /? option to list available options, and yet the list will specify the - convention). In Unix-like systems, the ASCII hyphen-minus begins options; the new (and GNU) convention is to use two hyphens then a word (e.g. --create) to identify the option's use while the old convention (and still available as an option for frequently used options) is to use one hyphen then one letter (e.g., -c); if one hyphen is followed by two or more letters it may mean two options are being specified, or it may mean the second and subsequent letters are a parameter (such as filename or date) for the first option. Two hyphen-minus characters without following letters (--) may indicate that the remaining arguments should not be treated as options, which is useful for example if a file name itself begins with a hyphen, or if further arguments are meant for an inner command (e.g., sudo). Double hyphen-minuses are also sometimes used to prefix long options where more descriptive option names are used. This is a common feature of GNU software. The getopt function and program, and the getopts command are usually used for parsing command-line options. Unix command names, arguments and options are case-sensitive (except in a few examples, mainly where popular commands from other operating systems have been ported to Unix). FlexOS, 4680 OS and 4690 OS use -. CP/M typically used [. Conversational Monitor System (CMS) uses a single left parenthesis to separate options at the end of the command from the other arguments. For example, in the following command the options indicate that the target file should be replaced if it exists, and the date and time of the source file should be retained on the copy: COPY source file a target file b (REPLACE OLDDATE) OS/360 operator commands use a comma separated list of positional and keyword parameters; only documented command and keyword abbreviations are valid. Keyword values are separated from the keywords with equal signs. TSO commands use a space separated list of positional and keyword parameters; keywords may be truncated to any unique sub-string. Only documented command abbreviations are valid. Keyword values are inside parentheses. Data General's CLI under their RDOS, AOS, etc. operating systems, as well as the version of CLI that came with their Business Basic, uses only / as the switch character, is case-insensitive, and allows local switches on some arguments to control the way they are interpreted, such as MAC/U LIB/S A B C $LPT/L has the global option U to the macro assembler command to append user symbols, but two local switches, one to specify LIB should be skipped on pass 2 and the other to direct listing to the printer, $LPT. One of the criticisms of a CLI is the lack of cues to the user as to the available actions.[citation needed] In contrast, GUIs usually inform the user of available actions with menus, icons, or other visual cues.[citation needed] To overcome this limitation, many CLI programs display a usage message, typically when invoked with no arguments or one of ?, -?, -h, -H, /?, /h, /H, /Help, -help, or --help. However, entering a program name without parameters in the hope that it will display usage help can be hazardous, as programs and scripts for which command line arguments are optional will execute without further notice. Although desirable at least for the help parameter, programs may not support all option lead-in characters exemplified above. Under DOS, where the default command-line option character can be changed from / to -, programs may query the SwitChar API in order to determine the current setting. So, if a program is not hardwired to support them all, a user may need to know the current setting even to be able to reliably request help. If the SwitChar has been changed to - and therefore the / character is accepted as alternative path delimiter also at the DOS command line, programs may misinterpret options like /h or /H as paths rather than help parameters. However, if given as first or only parameter, most DOS programs will, by convention, accept it as request for help regardless of the current SwitChar setting. In some cases, different levels of help can be selected for a program. Some programs supporting this allow to give a verbosity level as an optional argument to the help parameter (as in /H:1, /H:2, etc.) or they give just a short help on help parameters with question mark and a longer help screen for the other help options. Depending on the program, additional or more specific help on accepted parameters is sometimes available by either providing the parameter in question as an argument to the help parameter or vice versa (as in /H:W or in /W:? (assuming /W would be another parameter supported by the program)).[nb 1] In a similar fashion to the help parameter, but much less common, some programs provide additional information about themselves (like mode, status, version, author, license or contact information) when invoked with an about parameter like -!, /!, -about, or --about. Since the ? and ! characters typically also serve other purposes at the command line, they may not be available in all scenarios, therefore, they should not be the only options to access the corresponding help information. If more detailed help is necessary than provided by a program's built-in internal help, many systems support a dedicated external help command" command (or similar), which accepts a command name as calling parameter and will invoke an external help system. In the DR-DOS family, typing /? or /H at the COMMAND.COM prompt instead of a command itself will display a dynamically generated list of available internal commands; 4DOS and NDOS support the same feature by typing ? at the prompt (which is also accepted by newer versions of DR-DOS COMMAND.COM); internal commands can be individually disabled or reenabled via SETDOS /I. In addition to this, some newer versions of DR-DOS COMMAND.COM also accept a ?% command to display a list of available built-in pseudo-environment variables. Besides their purpose as quick help reference this can be used in batchjobs to query the facilities of the underlying command-line processor. Built-in usage help and man pages commonly employ a small syntax to describe the valid command form:[nb 2] Notice that these characters have different meanings than when used directly in the shell. Angle brackets may be omitted when confusing the parameter name with a literal string is not likely. In many areas of computing, but particularly in the command line, the space character can cause problems as it has two distinct and incompatible functions: as part of a command or parameter, or as a parameter or name separator. Ambiguity can be prevented either by prohibiting embedded spaces in file and directory names in the first place (for example, by substituting them with underscores _), or by enclosing a name with embedded spaces between quote characters or using an escape character before the space, usually a backslash (\). For example is ambiguous (is program name part of the program name, or two parameters?); however and are not ambiguous. Unix-based operating systems minimize the use of embedded spaces to minimize the need for quotes. In Microsoft Windows, one often has to use quotes because embedded spaces (such as in directory names) are common. Command-line interpreter Although most users think of the shell as an interactive command interpreter, it is really a programming language in which each statement runs a command. Because it must satisfy both the interactive and programming aspects of command execution, it is a strange language, shaped as much by history as by design. — Brian W. Kernighan & Rob Pike The term command-line interpreter is applied to computer programs designed to interpret a sequence of lines of text which may be entered by a user, read from a file or another kind of data stream. The context of interpretation is usually one of a given operating system or programming language. Command-line interpreters allow users to issue various commands in a very efficient (and often terse) way. This requires the user to know the names of the commands and their parameters, and the syntax of the language that is interpreted. The Unix #! mechanism and OS/2 EXTPROC command facilitate the passing of batch files to external processors. One can use these mechanisms to write specific command processors for dedicated uses, and process external data files which reside in batch files. Many graphical interfaces, such as the OS/2 Presentation Manager and early versions of Microsoft Windows use command lines to call helper programs to open documents and programs. The commands are stored in the graphical shell[clarification needed] or in files like the registry or the OS/2 OS2USER.INI file. The earliest computers did not support interactive input/output devices, often relying on sense switches and lights to communicate with the computer operator. This was adequate for batch systems that ran one program at a time, often with the programmer acting as operator. This also had the advantage of low overhead, since lights and switches could be tested and set with one machine instruction. Later a single system console was added to allow the operator to communicate with the system. From the 1960s onwards, user interaction with computers was primarily by means of command-line interfaces, initially on machines like the Teletype Model 33 ASR, but then on early CRT-based computer terminals such as the VT52. All of these devices were purely text based, with no ability to display graphic or pictures.[nb 3] For business application programs, text-based menus were used, but for more general interaction the command line was the interface. Around 1964 Louis Pouzin introduced the concept and the name shell in Multics, building on earlier, simpler facilities in the Compatible Time-Sharing System (CTSS).[better source needed] From the early 1970s the Unix operating system adapted the concept of a powerful command-line environment, and introduced the ability to pipe the output of one command in as input to another. Unix also had the capability to save and re-run strings of commands as shell scripts which acted like custom commands. The command line was also the main interface for the early home computers such as the Commodore PET, Apple II and BBC Micro – almost always in the form of a BASIC interpreter. When more powerful business-oriented microcomputers arrived with CP/M and later DOS computers such as the IBM PC, the command line began to borrow some of the syntax and features of the Unix shells such as globbing and piping of output. The command line was first seriously challenged by the PARC GUI approach used in the 1983 Apple Lisa and the 1984 Apple Macintosh. A few computer users used GUIs such as GEOS and Windows 3.1 but the majority of IBM PC users did not replace their COMMAND.COM shell with a GUI until Windows 95 was released in 1995. While most non-expert computer users now use a GUI almost exclusively, more advanced users have access to powerful command-line environments: Scripting Most command-line interpreters support scripting, to various extents. They are, after all, interpreters of an interpreted programming language, albeit in many cases the language is unique to the particular command-line interpreter. They will interpret scripts, variously termed shell scripts or batch files, written in the language that they interpret. Some command-line interpreters also incorporate the interpreter engines of other languages, such as REXX, in addition to their own, allowing the executing of scripts, in those languages, directly within the command-line interpreter itself. Conversely, scripting programming languages, in particular those with an eval function (such as REXX, Perl, Python, Ruby or Jython), can be used to implement command-line interpreters and filters. For a few operating systems, most notably DOS, such a command interpreter provides a more flexible command-line interface than the one supplied. In other cases, such a command interpreter can present a highly customised user interface employing the user interface and input/output facilities of the language. Other command-line interfaces The command line provides an interface between programs as well as the user. In this sense, a command line is an alternative to a dialog box. Editors and databases present a command line, in which alternate command processors might run. On the other hand, one might have options on the command line, which opens a dialog box. The latest version of 'Take Command' has this feature. DBase used a dialog box to construct command lines, which could be further edited before use. Programs like BASIC, diskpart, Edlin, and QBASIC all provide command-line interfaces, some of which use the system shell. Basic is modeled on the default interface for 8-bit Intel computers. Calculators can be run as command-line or dialog interfaces. Emacs provides a command-line interface in the form of its minibuffer. Commands and arguments can be entered using Emacs standard text editing support, and output is displayed in another buffer. There are a number of text mode games, like Adventure or King's Quest 1-3, which relied on the user typing commands at the bottom of the screen. One controls the character by typing commands like 'get ring' or 'look'. The program returns a text which describes how the character sees it, or makes the action happen. The text adventure The Hitchhiker's Guide to the Galaxy, a piece of interactive fiction based on Douglas Adams's book of the same name, is a teletype-style command-line game. The most notable of these interfaces is the standard streams interface, which allows the output of one command to be passed to the input of another. Text files can serve either purpose as well. This provides the interfaces of piping, filters and redirection. Under Unix, devices are files too, so the normal type of file for the shell used for stdin, stdout and stderr is a tty device file. Another command-line interface allows a shell program to launch helper programs, either to launch documents or start a program. The command is processed internally by the shell, and then passed on to another program to launch the document. The graphical interface of Windows and OS/2 rely heavily on command lines passed through to other programs – console or graphical, which then usually process the command line without presenting a user-console. Programs like the OS/2 E editor and some other IBM editors, can process command lines normally meant for the shell, the output being placed directly in the document window. A web browser's URL input field can be used as a command line. It can be used to launch web apps, access browser configuration, as well as perform a search. Google, which has been called "the command line of the internet" will perform a domain-specific search when it detects search parameters in a known format. This functionality is present whether the search is triggered from a browser field or on Google's website. There are JavaScript libraries that allow to write command line applications in browser as standalone Web apps or as part of bigger application. An example of such a website is the CLI interface to DuckDuckGo. There are also web-based SSH applications that allow access to a server’s command-line interface from a browser. Many PC video games feature a command line interface often referred to as a console. It is typically used by the game developers during development and by mod developers for debugging purposes as well as for cheating or skipping parts of the game. See also Notes References External links |
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