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[SOURCE: https://en.wikipedia.org/wiki/Shrek_2_(video_game)] | [TOKENS: 1381] |
Contents Shrek 2 (video game) Shrek 2 (also known as Shrek 2: The Game and ported for the PC as Shrek 2: Team Action) is a 2004 action-adventure video game published by Activision, based on the DreamWorks Animation film of the same name. The game was developed by Luxoflux for the PlayStation 2, Xbox, and GameCube platforms, while a version for PC was developed by KnowWonder. Plot Shrek 2's storyline follows a similar plot to that of the film. Shrek and Fiona are on a journey to the Kingdom of Far Far Away to visit Fiona's parents. Shrek's in-laws are unhappy that a crude ogre is married to their daughter Fiona and turned her into an ogre, and the battle for acceptance ensues. The game covers things not shown in the film. Plot elements are delivered primarily through a storybook interface (text and illustrations) shown before each level. Gameplay In this version of the game, the player is able to play as Shrek or his friends and travel through 11 levels. In each level, the player controls a team of four characters, and can switch between them at any point. Each character has a unique ability that aids them in fighting enemies or moving through the environment (for example, Donkey can destroy obstacles and Fiona can slow down time). The game is broken into different chapters, each with its own set of goals. One chapter requires the player to make sure three blind mice safely make their way to the witch's house. Other chapters have the player acting as a deputy in Far, Far Away Land—collecting bits of Humpty Dumpty, stealing treasure from a troll, helping the police clear out rioting hooligans from the streets, escorting Cinderella while she window-shops for a glass slipper, ridding the town of the Pied Piper's rat infestation, collecting chickens for a stew, or battling Puss in Boots via timed button presses. Players play mini-games when they are not traveling on hazardous paths from point A to point B. Challenges that require the player's entire party include having to punch chickens into cook pots or a pen, escorting characters through a stage (Billy Goat Gruff and the three blind mice), and collecting fairies, jewels, etc. The second type of mini-game, dubbed "Hero Time", gives one character a challenge to complete, usually emphasizing that character's particular skills displayed in the movie. Donkey at one point has to chase a fleeing onion wagon while riding on the back of Dragon. Fiona holds a private concert for a flock of black birds she is collecting for a pie (via exploding them by rhythm based button presses). Shrek has to throw a bunch of thugs into a paddy wagon. This version is a side-scroller with graphics resembling the Donkey Kong Country series, developed by Vicarious Visions. The game is separated into five books (worlds), each with five chapters (levels). The story of the game is a compressed version of the movie it is based on. The playable characters are Shrek, Donkey, Puss in Boots, Human Shrek and Gingerbread Man, each with their own unique set of skills. Development The game was first announced at E3 2003 in May that year, as a co-publishing collaboration between Activision and TDK Mediactive, the then-current video game license holder for the Shrek franchise, with Luxoflux announced to be developing the title. In December 2003, Take-Two Interactive purchased the North American operations of TDK Mediactive and rebranded them as Take-Two Licensing. With this, Activision terminated their publishing deal with TDK and instead announced a new partnership with DreamWorks for the Shrek license instead. Shortly after Activision announced that they would continue to work with DreamWorks to develop and publish several video games based on the upcoming movie, before they released the first trailer for the game in spring 2004. Two versions of the game were released for the PC; one developed by KnowWonder for younger audiences using Unreal Engine 2, and the other a port of the original console release under the title Shrek 2: Team Action which was developed by Beenox. The score for the game was composed by Kevin Manthei and Kevin Riepl. The soundtrack album consists of 58 tracks with over 65 minutes of score. It was released on May 6, 2004, by KMM Productions. Reception Shrek 2 received "mixed to average" reviews from critics. GameRankings and Metacritic gave it a score of 72.56% and 72 out of 100 for the Game Boy Advance version; 72.27% and 70 out of 100 for the GameCube version; 71.92% and 71 out of 100 for the PlayStation 2 version; 71.29% and 72 out of 100 for the Xbox version; 62.90% and 55 out of 100 for the PC version; and 49% for the Mobile version. IGN reviewer Mary Jane Irwin called the GameCube, Xbox, and PlayStation 2 versions of Shrek 2 "an amusing jaunt into the world of the movie," and Craig Harris, another reviewer of IGN, called the GBA version "an absolute treat, especially for those who dig the artstyle of the film," though he stated it to be "nothing new". The game, along with fellow movie sequel based game published by Activision, Spider-Man 2, shipped more than five million units combined and were the best-selling titles of May and June, respectively. In the United States, Shrek 2's Game Boy Advance version sold 700,000 copies and earned $18 million by August 2006. During the period between January 2000 and August 2006, it was the 35th highest-selling game launched for the Game Boy Advance, Nintendo DS or PlayStation Portable in that country. By July 2006, the PlayStation 2 version of Shrek 2 had sold 850,000 copies and earned $26 million in the United States. Next Generation ranked it as the 70th highest-selling game launched for the PlayStation 2, Xbox or GameCube between January 2000 and July 2006 in that country. Combined console sales of the Shrek series reached 2.5 million units in the United States by July 2006. During the 8th Annual Interactive Achievement Awards, the Academy of Interactive Arts & Sciences nominated Shrek 2 for "Console Children's Game of the Year". The game won for Favourite Video Game at the 2005 Kids' Choice Awards. References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Social_network#cite_ref-58] | [TOKENS: 5247] |
Contents Social network 1800s: Martineau · Tocqueville · Marx · Spencer · Le Bon · Ward · Pareto · Tönnies · Veblen · Simmel · Durkheim · Addams · Mead · Weber · Du Bois · Mannheim · Elias A social network is a social structure consisting of a set of social actors (such as individuals or organizations), networks of dyadic ties, and other social interactions between actors. The social network perspective provides a set of methods for analyzing the structure of whole social entities along with a variety of theories explaining the patterns observed in these structures. The study of these structures uses social network analysis to identify local and global patterns, locate influential entities, and examine dynamics of networks. For instance, social network analysis has been used in studying the spread of misinformation on social media platforms or analyzing the influence of key figures in social networks. Social networks and the analysis of them is an inherently interdisciplinary academic field which emerged from social psychology, sociology, statistics, and graph theory. Georg Simmel authored early structural theories in sociology emphasizing the dynamics of triads and "web of group affiliations". Jacob Moreno is credited with developing the first sociograms in the 1930s to study interpersonal relationships. These approaches were mathematically formalized in the 1950s and theories and methods of social networks became pervasive in the social and behavioral sciences by the 1980s. Social network analysis is now one of the major paradigms in contemporary sociology, and is also employed in a number of other social and formal sciences. Together with other complex networks, it forms part of the nascent field of network science. Overview The social network is a theoretical construct useful in the social sciences to study relationships between individuals, groups, organizations, or even entire societies (social units, see differentiation). The term is used to describe a social structure determined by such interactions. The ties through which any given social unit connects represent the convergence of the various social contacts of that unit. This theoretical approach is, necessarily, relational. An axiom of the social network approach to understanding social interaction is that social phenomena should be primarily conceived and investigated through the properties of relations between and within units, instead of the properties of these units themselves. Thus, one common criticism of social network theory is that individual agency is often ignored although this may not be the case in practice (see agent-based modeling). Precisely because many different types of relations, singular or in combination, form these network configurations, network analytics are useful to a broad range of research enterprises. In social science, these fields of study include, but are not limited to anthropology, biology, communication studies, economics, geography, information science, organizational studies, social psychology, sociology, and sociolinguistics. History In the late 1890s, both Émile Durkheim and Ferdinand Tönnies foreshadowed the idea of social networks in their theories and research of social groups. Tönnies argued that social groups can exist as personal and direct social ties that either link individuals who share values and belief (Gemeinschaft, German, commonly translated as "community") or impersonal, formal, and instrumental social links (Gesellschaft, German, commonly translated as "society"). Durkheim gave a non-individualistic explanation of social facts, arguing that social phenomena arise when interacting individuals constitute a reality that can no longer be accounted for in terms of the properties of individual actors. Georg Simmel, writing at the turn of the twentieth century, pointed to the nature of networks and the effect of network size on interaction and examined the likelihood of interaction in loosely knit networks rather than groups. Major developments in the field can be seen in the 1930s by several groups in psychology, anthropology, and mathematics working independently. In psychology, in the 1930s, Jacob L. Moreno began systematic recording and analysis of social interaction in small groups, especially classrooms and work groups (see sociometry). In anthropology, the foundation for social network theory is the theoretical and ethnographic work of Bronislaw Malinowski, Alfred Radcliffe-Brown, and Claude Lévi-Strauss. A group of social anthropologists associated with Max Gluckman and the Manchester School, including John A. Barnes, J. Clyde Mitchell and Elizabeth Bott Spillius, often are credited with performing some of the first fieldwork from which network analyses were performed, investigating community networks in southern Africa, India and the United Kingdom. Concomitantly, British anthropologist S. F. Nadel codified a theory of social structure that was influential in later network analysis. In sociology, the early (1930s) work of Talcott Parsons set the stage for taking a relational approach to understanding social structure. Later, drawing upon Parsons' theory, the work of sociologist Peter Blau provides a strong impetus for analyzing the relational ties of social units with his work on social exchange theory. By the 1970s, a growing number of scholars worked to combine the different tracks and traditions. One group consisted of sociologist Harrison White and his students at the Harvard University Department of Social Relations. Also independently active in the Harvard Social Relations department at the time were Charles Tilly, who focused on networks in political and community sociology and social movements, and Stanley Milgram, who developed the "six degrees of separation" thesis. Mark Granovetter and Barry Wellman are among the former students of White who elaborated and championed the analysis of social networks. Beginning in the late 1990s, social network analysis experienced work by sociologists, political scientists, and physicists such as Duncan J. Watts, Albert-László Barabási, Peter Bearman, Nicholas A. Christakis, James H. Fowler, and others, developing and applying new models and methods to emerging data available about online social networks, as well as "digital traces" regarding face-to-face networks. Levels of analysis In general, social networks are self-organizing, emergent, and complex, such that a globally coherent pattern appears from the local interaction of the elements that make up the system. These patterns become more apparent as network size increases. However, a global network analysis of, for example, all interpersonal relationships in the world is not feasible and is likely to contain so much information as to be uninformative. Practical limitations of computing power, ethics and participant recruitment and payment also limit the scope of a social network analysis. The nuances of a local system may be lost in a large network analysis, hence the quality of information may be more important than its scale for understanding network properties. Thus, social networks are analyzed at the scale relevant to the researcher's theoretical question. Although levels of analysis are not necessarily mutually exclusive, there are three general levels into which networks may fall: micro-level, meso-level, and macro-level. At the micro-level, social network research typically begins with an individual, snowballing as social relationships are traced, or may begin with a small group of individuals in a particular social context. Dyadic level: A dyad is a social relationship between two individuals. Network research on dyads may concentrate on structure of the relationship (e.g. multiplexity, strength), social equality, and tendencies toward reciprocity/mutuality. Triadic level: Add one individual to a dyad, and you have a triad. Research at this level may concentrate on factors such as balance and transitivity, as well as social equality and tendencies toward reciprocity/mutuality. In the balance theory of Fritz Heider the triad is the key to social dynamics. The discord in a rivalrous love triangle is an example of an unbalanced triad, likely to change to a balanced triad by a change in one of the relations. The dynamics of social friendships in society has been modeled by balancing triads. The study is carried forward with the theory of signed graphs. Actor level: The smallest unit of analysis in a social network is an individual in their social setting, i.e., an "actor" or "ego." Egonetwork analysis focuses on network characteristics, such as size, relationship strength, density, centrality, prestige and roles such as isolates, liaisons, and bridges. Such analyses, are most commonly used in the fields of psychology or social psychology, ethnographic kinship analysis or other genealogical studies of relationships between individuals. Subset level: Subset levels of network research problems begin at the micro-level, but may cross over into the meso-level of analysis. Subset level research may focus on distance and reachability, cliques, cohesive subgroups, or other group actions or behavior. In general, meso-level theories begin with a population size that falls between the micro- and macro-levels. However, meso-level may also refer to analyses that are specifically designed to reveal connections between micro- and macro-levels. Meso-level networks are low density and may exhibit causal processes distinct from interpersonal micro-level networks. Organizations: Formal organizations are social groups that distribute tasks for a collective goal. Network research on organizations may focus on either intra-organizational or inter-organizational ties in terms of formal or informal relationships. Intra-organizational networks themselves often contain multiple levels of analysis, especially in larger organizations with multiple branches, franchises or semi-autonomous departments. In these cases, research is often conducted at a work group level and organization level, focusing on the interplay between the two structures. Experiments with networked groups online have documented ways to optimize group-level coordination through diverse interventions, including the addition of autonomous agents to the groups. Randomly distributed networks: Exponential random graph models of social networks became state-of-the-art methods of social network analysis in the 1980s. This framework has the capacity to represent social-structural effects commonly observed in many human social networks, including general degree-based structural effects commonly observed in many human social networks as well as reciprocity and transitivity, and at the node-level, homophily and attribute-based activity and popularity effects, as derived from explicit hypotheses about dependencies among network ties. Parameters are given in terms of the prevalence of small subgraph configurations in the network and can be interpreted as describing the combinations of local social processes from which a given network emerges. These probability models for networks on a given set of actors allow generalization beyond the restrictive dyadic independence assumption of micro-networks, allowing models to be built from theoretical structural foundations of social behavior. Scale-free networks: A scale-free network is a network whose degree distribution follows a power law, at least asymptotically. In network theory a scale-free ideal network is a random network with a degree distribution that unravels the size distribution of social groups. Specific characteristics of scale-free networks vary with the theories and analytical tools used to create them, however, in general, scale-free networks have some common characteristics. One notable characteristic in a scale-free network is the relative commonness of vertices with a degree that greatly exceeds the average. The highest-degree nodes are often called "hubs", and may serve specific purposes in their networks, although this depends greatly on the social context. Another general characteristic of scale-free networks is the clustering coefficient distribution, which decreases as the node degree increases. This distribution also follows a power law. The Barabási model of network evolution shown above is an example of a scale-free network. Rather than tracing interpersonal interactions, macro-level analyses generally trace the outcomes of interactions, such as economic or other resource transfer interactions over a large population. Large-scale networks: Large-scale network is a term somewhat synonymous with "macro-level." It is primarily used in social and behavioral sciences, and in economics. Originally, the term was used extensively in the computer sciences (see large-scale network mapping). Complex networks: Most larger social networks display features of social complexity, which involves substantial non-trivial features of network topology, with patterns of complex connections between elements that are neither purely regular nor purely random (see, complexity science, dynamical system and chaos theory), as do biological, and technological networks. Such complex network features include a heavy tail in the degree distribution, a high clustering coefficient, assortativity or disassortativity among vertices, community structure (see stochastic block model), and hierarchical structure. In the case of agency-directed networks these features also include reciprocity, triad significance profile (TSP, see network motif), and other features. In contrast, many of the mathematical models of networks that have been studied in the past, such as lattices and random graphs, do not show these features. Theoretical links Various theoretical frameworks have been imported for the use of social network analysis. The most prominent of these are Graph theory, Balance theory, Social comparison theory, and more recently, the Social identity approach. Few complete theories have been produced from social network analysis. Two that have are structural role theory and heterophily theory. The basis of Heterophily Theory was the finding in one study that more numerous weak ties can be important in seeking information and innovation, as cliques have a tendency to have more homogeneous opinions as well as share many common traits. This homophilic tendency was the reason for the members of the cliques to be attracted together in the first place. However, being similar, each member of the clique would also know more or less what the other members knew. To find new information or insights, members of the clique will have to look beyond the clique to its other friends and acquaintances. This is what Granovetter called "the strength of weak ties". Structural holes In the context of networks, social capital exists where people have an advantage because of their location in a network. Contacts in a network provide information, opportunities and perspectives that can be beneficial to the central player in the network. Most social structures tend to be characterized by dense clusters of strong connections. Information within these clusters tends to be rather homogeneous and redundant. Non-redundant information is most often obtained through contacts in different clusters. When two separate clusters possess non-redundant information, there is said to be a structural hole between them. Thus, a network that bridges structural holes will provide network benefits that are in some degree additive, rather than overlapping. An ideal network structure has a vine and cluster structure, providing access to many different clusters and structural holes. Networks rich in structural holes are a form of social capital in that they offer information benefits. The main player in a network that bridges structural holes is able to access information from diverse sources and clusters. For example, in business networks, this is beneficial to an individual's career because he is more likely to hear of job openings and opportunities if his network spans a wide range of contacts in different industries/sectors. This concept is similar to Mark Granovetter's theory of weak ties, which rests on the basis that having a broad range of contacts is most effective for job attainment. Structural holes have been widely applied in social network analysis, resulting in applications in a wide range of practical scenarios as well as machine learning-based social prediction. Research clusters Research has used network analysis to examine networks created when artists are exhibited together in museum exhibition. Such networks have been shown to affect an artist's recognition in history and historical narratives, even when controlling for individual accomplishments of the artist. Other work examines how network grouping of artists can affect an individual artist's auction performance. An artist's status has been shown to increase when associated with higher status networks, though this association has diminishing returns over an artist's career. In J.A. Barnes' day, a "community" referred to a specific geographic location and studies of community ties had to do with who talked, associated, traded, and attended church with whom. Today, however, there are extended "online" communities developed through telecommunications devices and social network services. Such devices and services require extensive and ongoing maintenance and analysis, often using network science methods. Community development studies, today, also make extensive use of such methods. Complex networks require methods specific to modelling and interpreting social complexity and complex adaptive systems, including techniques of dynamic network analysis. Mechanisms such as Dual-phase evolution explain how temporal changes in connectivity contribute to the formation of structure in social networks. The study of social networks is being used to examine the nature of interdependencies between actors and the ways in which these are related to outcomes of conflict and cooperation. Areas of study include cooperative behavior among participants in collective actions such as protests; promotion of peaceful behavior, social norms, and public goods within communities through networks of informal governance; the role of social networks in both intrastate conflict and interstate conflict; and social networking among politicians, constituents, and bureaucrats. In criminology and urban sociology, much attention has been paid to the social networks among criminal actors. For example, murders can be seen as a series of exchanges between gangs. Murders can be seen to diffuse outwards from a single source, because weaker gangs cannot afford to kill members of stronger gangs in retaliation, but must commit other violent acts to maintain their reputation for strength. Diffusion of ideas and innovations studies focus on the spread and use of ideas from one actor to another or one culture and another. This line of research seeks to explain why some become "early adopters" of ideas and innovations, and links social network structure with facilitating or impeding the spread of an innovation. A case in point is the social diffusion of linguistic innovation such as neologisms. Experiments and large-scale field trials (e.g., by Nicholas Christakis and collaborators) have shown that cascades of desirable behaviors can be induced in social groups, in settings as diverse as Honduras villages, Indian slums, or in the lab. Still other experiments have documented the experimental induction of social contagion of voting behavior, emotions, risk perception, and commercial products. In demography, the study of social networks has led to new sampling methods for estimating and reaching populations that are hard to enumerate (for example, homeless people or intravenous drug users.) For example, respondent driven sampling is a network-based sampling technique that relies on respondents to a survey recommending further respondents. The field of sociology focuses almost entirely on networks of outcomes of social interactions. More narrowly, economic sociology considers behavioral interactions of individuals and groups through social capital and social "markets". Sociologists, such as Mark Granovetter, have developed core principles about the interactions of social structure, information, ability to punish or reward, and trust that frequently recur in their analyses of political, economic and other institutions. Granovetter examines how social structures and social networks can affect economic outcomes like hiring, price, productivity and innovation and describes sociologists' contributions to analyzing the impact of social structure and networks on the economy. Analysis of social networks is increasingly incorporated into health care analytics, not only in epidemiological studies but also in models of patient communication and education, disease prevention, mental health diagnosis and treatment, and in the study of health care organizations and systems. Human ecology is an interdisciplinary and transdisciplinary study of the relationship between humans and their natural, social, and built environments. The scientific philosophy of human ecology has a diffuse history with connections to geography, sociology, psychology, anthropology, zoology, and natural ecology. In the study of literary systems, network analysis has been applied by Anheier, Gerhards and Romo, De Nooy, Senekal, and Lotker, to study various aspects of how literature functions. The basic premise is that polysystem theory, which has been around since the writings of Even-Zohar, can be integrated with network theory and the relationships between different actors in the literary network, e.g. writers, critics, publishers, literary histories, etc., can be mapped using visualization from SNA. Research studies of formal or informal organization relationships, organizational communication, economics, economic sociology, and other resource transfers. Social networks have also been used to examine how organizations interact with each other, characterizing the many informal connections that link executives together, as well as associations and connections between individual employees at different organizations. Many organizational social network studies focus on teams. Within team network studies, research assesses, for example, the predictors and outcomes of centrality and power, density and centralization of team instrumental and expressive ties, and the role of between-team networks. Intra-organizational networks have been found to affect organizational commitment, organizational identification, interpersonal citizenship behaviour. Social capital is a form of economic and cultural capital in which social networks are central, transactions are marked by reciprocity, trust, and cooperation, and market agents produce goods and services not mainly for themselves, but for a common good. Social capital is split into three dimensions: the structural, the relational and the cognitive dimension. The structural dimension describes how partners interact with each other and which specific partners meet in a social network. Also, the structural dimension of social capital indicates the level of ties among organizations. This dimension is highly connected to the relational dimension which refers to trustworthiness, norms, expectations and identifications of the bonds between partners. The relational dimension explains the nature of these ties which is mainly illustrated by the level of trust accorded to the network of organizations. The cognitive dimension analyses the extent to which organizations share common goals and objectives as a result of their ties and interactions. Social capital is a sociological concept about the value of social relations and the role of cooperation and confidence to achieve positive outcomes. The term refers to the value one can get from their social ties. For example, newly arrived immigrants can make use of their social ties to established migrants to acquire jobs they may otherwise have trouble getting (e.g., because of unfamiliarity with the local language). A positive relationship exists between social capital and the intensity of social network use. In a dynamic framework, higher activity in a network feeds into higher social capital which itself encourages more activity. This particular cluster focuses on brand-image and promotional strategy effectiveness, taking into account the impact of customer participation on sales and brand-image. This is gauged through techniques such as sentiment analysis which rely on mathematical areas of study such as data mining and analytics. This area of research produces vast numbers of commercial applications as the main goal of any study is to understand consumer behaviour and drive sales. In many organizations, members tend to focus their activities inside their own groups, which stifles creativity and restricts opportunities. A player whose network bridges structural holes has an advantage in detecting and developing rewarding opportunities. Such a player can mobilize social capital by acting as a "broker" of information between two clusters that otherwise would not have been in contact, thus providing access to new ideas, opinions and opportunities. British philosopher and political economist John Stuart Mill, writes, "it is hardly possible to overrate the value of placing human beings in contact with persons dissimilar to themselves.... Such communication [is] one of the primary sources of progress." Thus, a player with a network rich in structural holes can add value to an organization through new ideas and opportunities. This in turn, helps an individual's career development and advancement. A social capital broker also reaps control benefits of being the facilitator of information flow between contacts. Full communication with exploratory mindsets and information exchange generated by dynamically alternating positions in a social network promotes creative and deep thinking. In the case of consulting firm Eden McCallum, the founders were able to advance their careers by bridging their connections with former big three consulting firm consultants and mid-size industry firms. By bridging structural holes and mobilizing social capital, players can advance their careers by executing new opportunities between contacts. There has been research that both substantiates and refutes the benefits of information brokerage. A study of high tech Chinese firms by Zhixing Xiao found that the control benefits of structural holes are "dissonant to the dominant firm-wide spirit of cooperation and the information benefits cannot materialize due to the communal sharing values" of such organizations. However, this study only analyzed Chinese firms, which tend to have strong communal sharing values. Information and control benefits of structural holes are still valuable in firms that are not quite as inclusive and cooperative on the firm-wide level. In 2004, Ronald Burt studied 673 managers who ran the supply chain for one of America's largest electronics companies. He found that managers who often discussed issues with other groups were better paid, received more positive job evaluations and were more likely to be promoted. Thus, bridging structural holes can be beneficial to an organization, and in turn, to an individual's career. Computer networks combined with social networking software produce a new medium for social interaction. A relationship over a computerized social networking service can be characterized by context, direction, and strength. The content of a relation refers to the resource that is exchanged. In a computer-mediated communication context, social pairs exchange different kinds of information, including sending a data file or a computer program as well as providing emotional support or arranging a meeting. With the rise of electronic commerce, information exchanged may also correspond to exchanges of money, goods or services in the "real" world. Social network analysis methods have become essential to examining these types of computer mediated communication. In addition, the sheer size and the volatile nature of social media has given rise to new network metrics. A key concern with networks extracted from social media is the lack of robustness of network metrics given missing data. Based on the pattern of homophily, ties between people are most likely to occur between nodes that are most similar to each other, or within neighbourhood segregation, individuals are most likely to inhabit the same regional areas as other individuals who are like them. Therefore, social networks can be used as a tool to measure the degree of segregation or homophily within a social network. Social Networks can both be used to simulate the process of homophily but it can also serve as a measure of level of exposure of different groups to each other within a current social network of individuals in a certain area. See also References Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/Madagascar:_Operation_Penguin] | [TOKENS: 334] |
Contents Madagascar: Operation Penguin Madagascar: Operation Penguin is a 2005 licensed platform game developed by Vicarious Visions and published by Activision for the Game Boy Advance. It is based on the DreamWorks Animation movie Madagascar and loosely follows events from the film's subplot, involving four penguins who attempt to escape the Central Park Zoo in order to live in Antarctica. Using various gadgets, the player traverses through 18 side-scrolling levels. The game's critical reception was mostly positive, with praise for its visuals and some criticism directed towards its gameplay and audio. Gameplay Madagascar: Operation Penguin is a side-scrolling platform game based on the DreamWorks Animation film Madagascar, loosely following events from its subplot involving four penguins journey to escape the Central Park Zoo and live in Antarctica. The player primarily controls one of these penguins, Private, through 18 levels, while using various gadgets in order to traverse certain obstacles and enemies. Reception GameZone gave the game a 7.5/10, stating: "With more variety and some mini-games, this could have been a better game, but as it stands, it's still a good outing with those penguins from Madagascar". Console Gameworld said it offers "witty dialogue to keep the story moving along and has some replay value." Game Chronicles claimed that Operation Penguin is "technically a very solid game, and only falls apart once you realize that [...] it's all the same old same old." Operation Penguin received "Favorite Video Game" at the 2006 Nickelodeon Kids' Choice Awards. References This action game–related article is a stub. You can help Wikipedia by adding missing information. |
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[SOURCE: https://en.wikipedia.org/wiki/IBM_PC_DOS] | [TOKENS: 2984] |
Contents IBM PC DOS IBM PC DOS (an acronym for IBM Personal Computer Disk Operating System),[nb 1] also known as PC DOS or IBM DOS, is a discontinued disk operating system for the IBM Personal Computer, its successors, and IBM PC compatibles. It was sold by IBM from the early 1980s into the 2000s. Developed by Microsoft, it was also sold by that company to the open market as MS-DOS. Both operating systems were identical or almost identical until 1993, when IBM began selling PC DOS 6.1 with its own new features. The collective shorthand for PC DOS and MS-DOS was DOS, which is also the generic term for disk operating system, and is shared with dozens of disk operating systems called DOS. History The IBM task force assembled to develop the IBM PC decided that critical components of the machine, including the operating system, would come from outside vendors. This radical break from company tradition of in-house development was one of the key decisions that made the IBM PC an industry standard. Microsoft, founded five years earlier by Bill Gates, was eventually selected for the operating system. IBM wanted Microsoft to retain ownership of whatever software it developed, and wanted nothing to do with helping Microsoft, other than making suggestions from afar. According to task force member Jack Sams: The reasons were internal. We had a terrible problem being sued by people claiming we had stolen their stuff. It could be horribly expensive for us to have our programmers look at code that belonged to someone else because they would then come back and say we stole it and made all this money. We had lost a series of suits on this, and so we didn't want to have a product which was clearly someone else's product worked on by IBM people. We went to Microsoft on the proposition that we wanted this to be their product.[citation needed] IBM first contacted Microsoft to look the company over in July 1980. Negotiations continued over the months that followed, and the paperwork was officially signed in early November. Although IBM expected that most customers would use PC DOS, the IBM PC also supported CP/M-86, which became available six months after PC DOS, and UCSD p-System operating systems. IBM's expectation proved correct: one survey found that 96.3% of PCs were ordered with the $40 PC DOS compared to 3.4% with the $240 CP/M-86. Over the history of IBM PC DOS, various versions were developed by IBM and Microsoft. By the time PC DOS 3.0 was completed, IBM had a team of developers covering the full OS. At that point in time, either IBM or Microsoft completely developed versions of IBM PC DOS going forward. By 1985, the joint development agreement (JDA) between IBM and Microsoft for the development of PC DOS had each company giving the other company a completely developed version. Most of the time branded versions were identical, but there were some cases in which each of the companies made minor modifications to their version of DOS. In the fall of 1984, IBM gave all the source code and documentation of the internally developed IBM TopView for DOS to Microsoft so that Microsoft could more fully understand how to develop an object-oriented operating environment, overlapping windows (for its development of Windows 2.0) and multitasking. Versions Microsoft first licensed, then purchased 86-DOS from Seattle Computer Products (SCP), which was modified for the IBM PC by Microsoft employee Bob O'Rear with assistance from SCP (later Microsoft) employee Tim Paterson. O'Rear modified 86-DOS to run on the prototype PC in February 1981. 86-DOS had to be converted from 8-inch to 5.25-inch floppy disks and integrated with the BIOS, which Microsoft was helping IBM to write. IBM had more people writing requirements for the computer than Microsoft had writing code. O'Rear often felt overwhelmed by the number of people he had to deal with at the ESD (Entry Systems Division) facility in Boca Raton, Florida. Perhaps the first public mention of the operating system was in July 1981, when Byte discussed rumors of a forthcoming personal computer with "a CP/M-like DOS ... to be called, simply, 'IBM Personal Computer DOS'". 86-DOS was rebranded IBM PC DOS 1.0 for its August 1981 release with the IBM PC. The initial version of DOS was largely based on CP/M-80 1.x and most of its architecture, function calls and file-naming conventions were copied directly from the older OS. The most significant difference was the fact that it introduced a different file system, FAT12. Unlike all later DOS versions, the DATE and TIME commands were separate executables rather than part of COMMAND.COM. Single-sided 160 kilobyte (KB) 5.25-inch floppies were the only disk format supported. At Microsoft in late 1981, Paterson began writing PC DOS 1.10. It debuted in May 1982 along with the Revision B IBM PC. Support for the new double-sided drives was added, allowing 320 KB per disk. A number of bugs were fixed, and error messages and prompts were made less cryptic. The DEBUG.EXE was now able to load files greater than 64 KB in size. Later, a group of Microsoft programmers (primarily Paul Allen, Mark Zbikowski and Aaron Reynolds) began work on PC DOS 2.0. Completely rewritten, DOS 2.0 added subdirectories and hard disk support for the new IBM XT, which debuted in March 1983. A new 9-sector format bumped the capacity of floppy disks to 360 KB. The Unix-inspired kernel featured file handles in place of the CP/M-derivative file control blocks and loadable device drivers could now be used for adding hardware beyond that which the IBM PC BIOS supported. BASIC and most of the utilities provided with DOS were substantially upgraded as well. A major undertaking that took almost 10 months of work, DOS 2.0 was more than twice as big as DOS 1.x, occupying around 28 KB of RAM compared to the 12 KB of its predecessor. It would form the basis for all Microsoft consumer-oriented OSes until 2001, when Windows XP (based on Windows NT) was released. In October 1983 (officially 1 November 1983) DOS 2.1 debuted. It fixed some bugs and added support for half-height floppy drives and the new IBM PCjr. In 1983, Compaq released the Compaq Portable, the first 100% IBM PC compatible. It shipped with COMPAQ-DOS, its own OEM version of MS-DOS 1.10 (quickly replaced by DOS 2.00) from Microsoft. Other PC compatibles followed suit, most of which included hardware-specific DOS features, although some were generic. In August 1984, IBM introduced the Intel 80286-derived IBM PC/AT, its next-generation machine. Along with this was DOS 3.00. Despite jumping a whole version number, it again proved little more than an incremental upgrade, adding nothing more substantial than support for the AT's new 1.2 megabyte (MB) floppy disks. Planned networking capabilities in DOS 3.00 were judged too buggy to be usable and Microsoft disabled them prior to the OS's release. In any case, IBM's original plans for the AT had been to equip it with a proper next-generation OS that would use its extended features, but this never materialized. PC DOS 3.1 (released March 1985) fixed the bugs in DOS 3.00 and supported IBM's Network Adapter card on the IBM PC Network. PC DOS 3.2 added support for 3+1⁄2-inch double-density 720 KB floppy disk drives, supporting the IBM PC Convertible, IBM's first computer to use 3+1⁄2-inch floppy disks, released April 1986, and later the IBM Personal System/2 in 1987. In June 1985, IBM and Microsoft signed a long-term Joint Development Agreement to share specified DOS code and create a new operating system from scratch, known at the time as Advanced DOS. On 2 April 1987 OS/2 was announced as the first product produced under the agreement. At the same time, IBM released its next generation of personal computers, the IBM Personal System/2 (PS/2). PC DOS 3.3, released with the PS/2 line, added support for high density 3+1⁄2-inch 1.44 MB floppy disk drives, which IBM introduced in its 80286-based and higher PS/2 models. The upgrade from DOS 3.2 to 3.3 was completely written by IBM, with no development effort on the part of Microsoft, who were working on "Advanced DOS 1.0". DOS 3.30 was the last version designed with the IBM XT and floppy-only systems in mind; it became one of the most popular versions and many users preferred it to its buggy successor. PC DOS 4.0 (internally known as DOS 3.4 originally) shipped July 1988. DOS 4.0 had some compatibility issues with low-level disk utilities due to some internal data structure changes. DOS 4.0 used more memory than DOS 3.30 and it also had a few glitches. Newly added EMS drivers were only compatible with IBM's EMS boards and not the more common[citation needed] Intel and AST ones. DOS 4.0 is also notable for including the first version of the DOS Shell, a full-screen utility designed to make the command-line OS more user-friendly. Microsoft resumed control of development and released a bug-fixed DOS 4.01. DOS 5 debuted in June 1991. DOS 5 supported the use of the High Memory Area (HMA) and Upper Memory Blocks (UMBs) on 80286 and later systems to reduce its conventional memory usage. Also all DOS commands now supported the /? option to display command syntax. Aside from IBM's PC DOS, MS-DOS was the only other version available, as OEM editions vanished since by this time PCs were 100% compatible, so customizations for hardware differences were no longer necessary. The POWER.EXE was introduced that has the APM standard in version 5.02. This was the last version of DOS that IBM and Microsoft shared the full code. This was the DOS integrated into the virtual DOS machine of OS/2 2.0 and later Windows NT. PC DOS remained a rebranded version of MS-DOS until 1993 when IBM and Microsoft parted ways. MS-DOS 6 was released in March, and PC DOS 6.1 (separately developed) followed in June. Most of the new features from MS-DOS 6.0 appeared in PC DOS 6.1 including new boot menu support and new commands CHOICE, DELTREE, and MOVE. QBasic was dropped. MS-DOS Editor was replaced with the IBM E Editor. It also licensed components of Central Point's PC Tools, such as Central Point Backup Utility (CPBACKUP). PC DOS 6.1 reports itself as DOS 6.00. PC DOS 6.3 followed in December. PC DOS 6.3 was also used in OS/2 for the PowerPC. PC DOS 6.3 also featured SuperStor disk compression technology from Addstor. PC DOS 7 was released in April 1995 and was the last release of DOS before IBM software development (other than the development IBM ViaVoice) moved to Austin. The REXX programming language was added, as well as support for a new floppy disk format, XDF, which extended a standard 1.44 MB floppy disk to 1.86 MB. SuperStor disk compression technology was replaced with Stac Electronics' STACKER. An algebraic command line calculator and a utility program to load device drivers from the command line were added. PC DOS 7 also included many optimizations to increase performance and reduce memory usage. The most recent retail release was PC DOS 2000 – released from Austin in 1998 – which found its niche in the embedded software market and elsewhere. PC DOS 2000 is a slipstream of 7.0 with Y2K and other fixes applied. To applications, PC DOS 2000 reports itself as "IBM PC DOS 7.00, revision 1", in contrast to the original PC DOS 7, which reported itself as "IBM PC DOS 7.00, revision 0".[nb 2] PC-DOS 2000 was the last version of IBM PC-DOS that was sold at retail. IBM advertised it as a Y2K compliant DOS. As it reports itself as "IBM PC-DOS 7 Revision 1", it is often referred to as "IBM PC-DOS7R1" or just "PC-DOS7R1". Hitachi used PC DOS 2000 in their legacy Drive Fitness Test (4.15) and Hitachi Feature Tool (2.15) until 2009. ThinkPad products had a copy of the latest version of PC DOS in their Rescue and Recovery partition. PC DOS 7.1 added support for Logical Block Addressing (LBA) and FAT32 partitions.[nb 2] Various builds from 1999 up to 2003 were not released in retail, but instead used in products such as the IBM ServerGuide Scripting Toolkit. A build of this version of DOS appeared in Norton Ghost from Symantec. Version 7.1 indicates support for FAT32 also in MS-DOS. Most builds of this version of DOS are limited to the kernel files IBMBIO.COM, IBMDOS.COM, and COMMAND.COM. The updated programs FDISK32 and FORMAT32 allow one to prepare FAT32 disks. Additional utilities are taken from PC DOS 2000, where needed. PC DOS as a distributed file client In 1986, IBM announced PC DOS support for client access to the file services defined by Distributed Data Management Architecture (DDM). This enabled programs on PCs to create, manage, and access record-oriented files available on IBM System/36, IBM System/38 and IBM mainframe computers running CICS. In 1988, client support for stream-oriented files and hierarchical directories was added to PC DOS when they became available on the DDM server systems. See also Notes References Further reading |
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Contents Eastern Mediterranean The Eastern Mediterranean is a loosely delimited region comprising the easternmost portion of the Mediterranean Sea, and well as the adjoining land—often defined as the countries around the Levantine Sea. It includes the southern half of Turkey's main region, Anatolia; its smaller Hatay Province; the island of Cyprus; the Greek Dodecanese islands; and the countries of Egypt, Israel, Palestine, Syria and Lebanon. Its broadest uses can encompass the Libyan Sea (thus Libya), the Aegean Sea (thus European Turkey and the mainland and islands of Greece), and the Ionian Sea (thus southern Albania in Southeast Europe) and can extend west to Italy's farthest south-eastern coasts. Although Jordan does not border the Mediterranean Sea, it is sometimes included in broader Levantine or Eastern Mediterranean frameworks for historical, cultural, or political analysis. Regions The eastern Mediterranean region is commonly interpreted in two ways: The World Health Organization (WHO) divides the world into six WHO regions, for the purposes of reporting, analysis and administration. In this context, the Eastern Mediterranean Region (EMR) is one of those six WHO regions. Countries The countries and territories of the Eastern Mediterranean include Cyprus, Turkey (Anatolia), its smaller Hatay Province, the Greek Dodecanese islands, and the countries of Lebanon, Syria, Israel, Palestine, Jordan and Egypt. North-eastern Mediterranean has been put to print as a term for the Greater Balkans: Albania, Bosnia and Herzegovina, Bulgaria, Croatia, Greece, Slovenia, North Macedonia, Serbia, Kosovo, Montenegro, Romania. A five-author statistics-rich study of 2019 has sought to add Moldova and Ukraine beyond, which others link more to the Black Sea's economy and history. The three-word term is mainly a complex euphemism for the Balkan peninsula used by those who stigmatise the word "Balkanisation" and to suggest parallels with other conflicts of the Eastern Mediterranean. The WHO Regional Office for the Eastern Mediterranean includes the Eastern Mediterranean as well as the other regions of contiguous Afro-Eurasia: West Asia, North Africa, the Horn of Africa, Central Asia, Afghanistan, and Pakistan. History See also References |
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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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[SOURCE: https://en.wikipedia.org/wiki/Ioudaios] | [TOKENS: 1918] |
Contents Ioudaios Ioudaios (Ancient Greek: Ἰουδαῖος; pl. Ἰουδαῖοι Ioudaioi)[n 1] is an Ancient Greek ethnonym used in classical and biblical literature which commonly translates to "Jew" or "Judean". The choice of translation is the subject of frequent scholarly debate, given its central importance to passages in the Bible (both the Hebrew Bible and the New Testament) as well as works of other writers such as Josephus and Philo. Translating it as Jews is seen to imply connotations as to the religious beliefs of the people, whereas translating it as Judeans confines the identity within the geopolitical boundaries of Judea. A related translation debate refers to the terms ἰουδαΐζειν (verb), literally translated as "Judaizing" (compare Judaizers), and Ἰουδαϊσμός (noun), controversially translated as Judaism or Judeanism. Etymology and usage The Hebrew term Yehudi (יְהוּדִי) occurs 74 times in the Masoretic text of the Hebrew Bible. It occurs first in the Hebrew Bible in 2 Kings 16:6 where Rezin king of Syria drove the 'Jews' out of Elath, and earliest among the prophets in Jeremiah 32:12 of 'Jews' that sat in the court of the prison." In the Septuagint the term is translated Ioudaios. According to Shaye J. D. Cohen, the meaning of the term "Ioudaios" evolved throughout the Second Temple period, with 2 Maccabees representing a greater emphasis on the cultural and religious aspects of Jewish identity. Despite this shift, later sources still highlight the importance of kinship and blood in Jewish national identity. For instance, Josephus recounts that Antigonus II Mattathias, the last Hasmonean king of Judea, labeled Herod a "half Judean," (ἡμιιουδαιος, or hemi-Ioudaios), referencing his Idumean ancestry, rather than his behavior. Ioudaismos The Ancient Greek term Ioudaismos (Ἰουδαϊσμός; from ἰουδαΐζειν 'to side with or imitate the [Judeans]'), often translated as "Judaism" or "Judeanism", first appears in 2 Maccabees in the 2nd century BC. In the context of the age and period it held the meaning of seeking or forming part of a cultural entity and resembles its antonym Hellenismos, meaning acceptance of Hellenic (Greek) cultural norms (the conflict between Ioudaismos and Hellenismos lay behind the Maccabean revolt and hence the invention of the term Ioudaismos). Shaye J. D. Cohen wrote: We are tempted, of course, to translate [Ioudaismos] as "Judaism," but this translation is too narrow, because in this first occurrence of the term, Ioudaismos has not yet be reduced to designation of a religion. It means rather "the aggregate of all those characteristics that makes Judaeans Judaean (or Jews Jewish)." Among these characteristics, to be sure, are practices and beliefs that we would today call "religious," but these practices and beliefs are not the sole content of the term. Thus Ioudaïsmos should be translated not as "Judaism" but as Judaeanness. Translation implications As mentioned above, translating it as "Jews" has implications about the beliefs of the people whereas translation as "Judeans" emphasizes their geographical origin. The word Ioudaioi is used primarily in three areas of literature in antiquity: the later books of the Hebrew Bible and Second Temple literature (e.g. the Books of the Maccabees), the New Testament (particularly the Gospel of John and Acts of the Apostles), and classical writers from the region such as Josephus and Philo. There is a wide range of scholarly views as to the correct translations with respect to each of these areas, with some scholars suggesting that either the words Jews or Judeans should be used in all cases, and other scholars suggesting that the correct translation needs to be interpreted on a case-by-case basis.[weasel words] One complication in the translation question is that the meaning of the word evolved over the centuries. For example, Morton Smith, writing in the 1999 Cambridge History of Judaism, states that from c.100 BCE under the Hasmoneans the meaning of the word Ioudaioi expanded further: In 2001, the third edition of the Bauer lexicon, one of the most highly respected dictionaries of Biblical Greek, supported translation of the term as "Judean", writing: Incalculable harm has been caused by simply glossing Ioudaios with 'Jew,' for many readers or auditors of Bible translations do not practice the historical judgment necessary to distinguish between circumstances and events of an ancient time and contemporary ethnic-religious-social realities, with the result that anti-Judaism in the modern sense of the term is needlessly fostered through biblical texts. In 2006, Amy-Jill Levine took the opposite view in her Misunderstood Jew, writing: "The translation 'Jew', however, signals a number of aspects of Jesus' behavior and that of other 'Jews', whether Judean, Galilean, or from the Diaspora: circumcision, wearing tzitzit, keeping kosher, calling God 'father', attending synagogue gatherings, reading the Torah and Prophets, knowing that they are neither Gentiles nor Samaritans, honoring the Sabbath, and celebrating the Passover. All these, and much more, are markers also of traditional Jews today. Continuity between Judeans and Jews outweighs the discontinuity." Academic publications in the last ten to fifteen years increasingly use the term Judeans rather than Jews. Most of these writers cite Steve Mason's 2007 article, "Jews, Judaeans, Judaizing, Judaism: Problems of Categorization in Ancient History". Mason and others argue that "Judean" is a more precise and a more ethical translation of ioudaios than is "Jew". Much of the debate stems from the use of the term in the New Testament where Ioudaios is often used in a negative context. Translating Ioudaios as "Judeans" implies simply people living in a geographic area, whereas translating the term as "Jews" implies a legalistic religious and ethnic component which in later Christian works was characterized as a religion devoid of "grace", "faith", and "freedom". It is this later understanding which some scholars have argued was not applicable in the ancient world. They argue that the New Testament texts need to be critically examined without the baggage that Christianity has associated with the term "Jew". Others such as Adele Reinhartz argue that New Testament anti-Judaism cannot be so neatly separated from later forms of anti-Judaism. It has also been suggested that “Judean” can refer to believers of the Judean God and allies of the Judean state. In 2014, Daniel R. Schwartz distinguishes "Judean" and "Jew", where the former means "Of or pertaining to Judea or southern Palestine", while the latter refers "A person belonging to the worldwide group constituting a continuation through descent or conversion of the ancient Jewish people and characterized by a sense of community". In 2021, Lester L. Grabbe explained that he translates the terms Ἰουδαῖος, Iudaeus, and יהודי as "Jew" when they appear in historical sources, using the term "Judaean" specifically for individuals who lived in, or were born in, the geographic region of Judea. In 2024, Jodi Magness, wrote the term Ioudaioi refers to a "people of Judahite/Judean ancestry who worshipped the God of Israel as their national deity and (at least nominally) lived according to his laws." Language comparison The English word Jew derives via the Anglo-French "Iuw" from the Old French forms "Giu" and "Juieu", which had elided (dropped) the letter "d" from the Medieval Latin form Iudaeus, which, like the Greek Ioudaioi it derives from, meant both Jews and Judeans / "of Judea". However, most other European languages retained the letter "d" in the word for Jew; e.g. Danish and Norwegian jøde, Dutch jood, German Jude, Italian giudeo, Spanish judío etc. The distinction of translation of Yehudim in Biblical Hebrew between "Judeans", and "Jews" is relevant in English translations of the Bible. See also Notes and references External links General references Ioudaioi in the Gospel of John |
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[SOURCE: https://en.wikipedia.org/wiki/Ursa_Major] | [TOKENS: 4349] |
Contents Ursa Major Ursa Major, also known as the Great Bear, is a constellation in the Northern Sky, whose associated mythology likely dates back into prehistory. Its Latin name means "greater (or larger) bear", referring to and contrasting it with nearby Ursa Minor, the lesser bear. In antiquity, it was one of the original 48 constellations listed by Ptolemy in the 2nd century AD, drawing on earlier works by Greek, Egyptian, Babylonian, and Assyrian astronomers. Today it is the third largest of the 88 modern constellations. Ursa Major is primarily known from the asterism of its main seven stars, which has been called the "Big Dipper", "the Wagon", "Charles's Wain", or "the Plough", among other names. In particular, the Big Dipper's stellar configuration mimics the shape of the "Little Dipper". Two of its stars, named Dubhe and Merak (α Ursae Majoris and β Ursae Majoris), can be used as the navigational pointer towards the place of the current northern pole star, Polaris in Ursa Minor. Ursa Major, along with asterisms it contains or overlaps, is significant to numerous world cultures, often as a symbol of the north. Its depiction on the flag of Alaska is a modern example of such symbolism. Ursa Major is visible throughout the year from most of the Northern Hemisphere, and appears circumpolar above the mid-northern latitudes. From southern temperate latitudes, the main asterism is invisible, but the southern parts of the constellation can still be viewed. Characteristics Ursa Major covers 1279.66 square degrees or 3.10% of the total sky, making it the third largest constellation. In 1930, Eugène Delporte set its official International Astronomical Union (IAU) constellation boundaries, defining it as a 28-sided irregular polygon. In the equatorial coordinate system, the constellation stretches between the right ascension coordinates of 08h 08.3m and 14h 29.0m and the declination coordinates of +28.30° and +73.14°. Ursa Major borders eight other constellations: Draco to the north and northeast, Boötes to the east, Canes Venatici to the east and southeast, Coma Berenices to the southeast, Leo and Leo Minor to the south, Lynx to the southwest and Camelopardalis to the northwest. The three-letter constellation abbreviation "UMa" was adopted by the IAU in 1922. Features The outline of the seven bright stars of Ursa Major form the asterism known as the "Big Dipper" in the United States and Canada, while in the United Kingdom it is called the Plough or (historically) Charles' Wain. Six of the seven stars are of second magnitude or higher, and it forms one of the best-known patterns in the sky. As many of its common names allude, its shape is said to resemble a ladle, an agricultural plough, or wagon. In the context of Ursa Major, they are commonly drawn to represent the hindquarters and tail of the Great Bear. Starting with the "ladle" portion of the dipper and extending clockwise (eastward in the sky) through the handle, these stars are the following: Except for Dubhe and Alkaid, the stars of the Big Dipper all have proper motions heading toward a common point in Sagittarius. A few other such stars have been identified, and together they are called the Ursa Major Moving Group. The stars Merak (β Ursae Majoris) and Dubhe (α Ursae Majoris) are known as the "pointer stars" because they are helpful for finding Polaris, also known as the North Star or Pole Star. By visually tracing a line from Merak through Dubhe (1 unit) and continuing for 5 units, one's eye will land on Polaris, accurately indicating true north. Another asterism is recognized in Arab culture as representing three pairs of footprints of a leaping gazelle. It is a series of three pairs of stars found along the southern border of the constellation. From southeast to southwest, the "first leap", comprising ν and ξ Ursae Majoris (Alula Borealis and Australis, respectively); the "second leap", comprising λ and μ Ursae Majoris (Tania Borealis and Australis); and the "third leap", comprising ι and κ Ursae Majoris (Talitha and Alkaphrah). The same asterism has the Chinese name Santai and the Indian name Trivikrama, both meaning "three steps". W Ursae Majoris is the prototype of a class of contact binary variable stars, and ranges between magnitudes 7.75 and 8.48. 47 Ursae Majoris is a Sun-like star with a three-planet system. 47 Ursae Majoris b, discovered in 1996, orbits every 1078 days and is 2.53 times the mass of Jupiter. 47 Ursae Majoris c, discovered in 2001, orbits every 2391 days and is 0.54 times the mass of Jupiter. 47 Ursae Majoris d, discovered in 2010, has an uncertain period, lying between 8907 and 19097 days; it is 1.64 times the mass of Jupiter. The star is of magnitude 5.0 and is approximately 46 light-years from Earth. The star TYC 3429-697-1 (9h 40m 44s 48° 14′ 2″), located to the east of θ Ursae Majoris and to the southwest of the "Big Dipper") has been recognized as the state star of Delaware, and is informally known as the Delaware Diamond. Several bright galaxies are found in Ursa Major, including the pair Messier 81 (one of the brightest galaxies in the sky) and Messier 82 above the bear's head, and Pinwheel Galaxy (M101), a spiral northeast of Alkaid. The spiral galaxies Messier 108 and Messier 109 are also found in this constellation. The bright planetary nebula Owl Nebula (M97) can be found along the bottom of the bowl of the Big Dipper. M81 is a nearly face-on spiral galaxy 11.8 million light-years from Earth. Like most spiral galaxies, it has a core made up of old stars, with arms filled with young stars and nebulae. Along with M82, it is a part of the galaxy cluster closest to the Local Group. M82 is a nearly edgewise galaxy that is interacting gravitationally with M81. It is the brightest infrared galaxy in the sky. SN 2014J, an apparent Type Ia supernova, was observed in M82 on 21 January 2014. M97, also called the Owl Nebula, is a planetary nebula 1,630 light-years from Earth; it has a magnitude of approximately 10. It was discovered in 1781 by Pierre Méchain. M101, also called the Pinwheel Galaxy, is a face-on spiral galaxy located 25 million light-years from Earth. It was discovered by Pierre Méchain in 1781. Its spiral arms have regions with extensive star formation and have strong ultraviolet emissions. It has an integrated magnitude of 7.5, making it visible in both binoculars and telescopes, but not to the naked eye. NGC 2787 is a lenticular galaxy at a distance of 24 million light-years. Unlike most lenticular galaxies, NGC 2787 has a bar at its center. It also has a halo of globular clusters, indicating its age and relative stability. NGC 2950 is a lenticular galaxy located 60 million light-years from Earth. NGC 3000 is a double star, and catalogued as a nebula-type object. NGC 3079 is a starburst spiral galaxy located 52 million light-years from Earth. It has a horseshoe-shaped structure at its center that indicates the presence of a supermassive black hole. The structure itself is formed by superwinds from the black hole. NGC 3310 is another starburst spiral galaxy located 50 million light-years from Earth. Its bright white color is caused by its higher than usual rate of star formation, which began 100 million years ago after a merger. Studies of this and other starburst galaxies have shown that their starburst phase can last for hundreds of millions of years, far longer than was previously assumed. NGC 4013 is an edge-on spiral galaxy located 55 million light-years from Earth. It has a prominent dust lane and has several visible star forming regions. I Zwicky 18 is a young dwarf galaxy at a distance of 45 million light-years. The youngest-known galaxy in the visible universe, I Zwicky 18 is about 4 million years old, about one-thousandth the age of the Solar System. It is filled with star forming regions which are creating many hot, young, blue stars at a very high rate. The Hubble Deep Field is located to the northeast of δ Ursae Majoris. HD 80606, a sun-like star in a binary system, orbits a common center of gravity with its partner, HD 80607; the two are separated by 1,200 AU on average. Research conducted in 2003 indicates that its sole planet, HD 80606 b is a future hot Jupiter, modeled to have evolved in a perpendicular orbit around 5 AU from its sun. The 4-Jupiter mass planet is projected to eventually move into a circular, more aligned orbit via the Kozai mechanism. However, it is currently on an incredibly eccentric orbit that ranges from approximately one astronomical unit at its apoapsis and six stellar radii at periapsis. History Ursa Major has been reconstructed as an Indo-European constellation. It was one of the 48 constellations listed by the 2nd century AD astronomer Ptolemy in his Almagest, who called it Arktos Megale.[a] Mythology The constellation of Ursa Major has been seen as a bear, usually female, by multiple connected civilizations. This may stem from a common oral tradition of Cosmic Hunt myths stretching back more than 13,000 years. Using statistical and phylogenetic tools, Julien d'Huy reconstructs the following Palaeolithic state of the story: "There is an animal that is a horned herbivore, especially an elk. One human pursues this ungulate. The hunt locates or get to the sky. The animal is alive when it is transformed into a constellation. It forms the Big Dipper." Whilst the Pre-Islamic Arabs recognised the larger constellation of Ursa Major as being a bear, perhaps due to Greek influence, they had traditionally always recognised the Big Dipper and Ursa Minor as being counterparts. Both were imagined as funeral processions with the ladle of either seen as a funerary bier and its handle as a train of mourners. The Big Dipper is known as banāt an-na'sh al-kubrā meaning literally "the greater daughters of the bier". However daughters here means those pertaining to it, i.e. the mourners and thus is better translated as "the greater funeral procession", whilst Ursa Minor is known as "the lesser funeral procession". There is also a legend that the body on the bier is the father of those following behind it, a man called Na'ash who was murdered by Al-judayy (the Arabic name for the North Star) and whom the funeral procession is in pursuit of. In Greek mythology, Zeus (the king of the gods, known as Jupiter in Roman mythology) lusts after a young woman named Callisto, a nymph of Artemis (known to the Romans as Diana). Zeus's jealous wife Hera (Juno to the Romans) discovers that Callisto has a son named Arcas as the result of her rape by Zeus and transforms Callisto into a bear as a punishment. Callisto, while in bear form, later encounters her son Arcas. Arcas almost spears the bear, but to avert the tragedy Zeus whisks them both into the sky, Callisto as Ursa Major and Arcas as the constellation Boötes. Ovid called Ursa Major the Parrhasian Bear, since Callisto came from Parrhasia in Arcadia, where the story is set. The Greek poet Aratus called the constellation Helike, ("turning" or "twisting"), because it turns around the celestial pole. The Odyssey notes that it is the sole constellation that never sinks below the horizon and "bathes in the Ocean's waves", so it is used as a celestial reference point for navigation. It has also been called the "Wain" or "Plaustrum", a Latin word referring to a horse-drawn cart. In Hinduism, The earliest mention of Ursa Major/Big dipper/ Great Bear is known as Saptarshi, each of the stars representing one of the Saptarishis or Seven Sages (Rishis) viz. Bhrigu, Atri, Angiras, Vasishtha, Pulastya, Pulaha, and Kratu. is found in the Rigveda (c. 1500–1200 BCE), one of the oldest known texts in human history. References in Ancient Indian Texts: For Ursa Minor, it was not explicitly mentioned in early Vedic texts but was recognized in later astronomical texts such as: The fact that the two front stars of the constellations point to the pole star is explained as the boon given to the boy sage Dhruva by Lord Vishnu. Thus, the Rigveda holds the earliest recorded mention of Ursa Major, while Ursa Minor gained prominence in later astronomical traditions. Ursa Major may be mentioned in the biblical book of Job, dated between the 7th and 4th centuries BC, although this is often disputed. In China and Japan, the Big Dipper is called the "North Dipper" 北斗 (Chinese: běidǒu, Japanese: hokuto), and in ancient times, each one of the seven stars had a specific name, often coming themselves from ancient China: In Shinto, the seven largest stars of Ursa Major belong to Ame-no-Minakanushi, the oldest and most powerful of all kami. In South Korea, the constellation is referred to as "the seven stars of the north". In the related myth, a widow with seven sons found comfort with a widower, but to get to his house required crossing a stream. The seven sons, sympathetic to their mother, placed stepping stones in the river. Their mother, not knowing who put the stones in place, blessed them and, when they died, they became the constellation. The Iroquois interpreted Alioth, Mizar, and Alkaid as three hunters pursuing the Great Bear. According to one version of their myth, the first hunter (Alioth) is carrying a bow and arrow to strike down the bear. The second hunter (Mizar) carries a large pot – the star Alcor – on his shoulder in which to cook the bear while the third hunter (Alkaid) hauls a pile of firewood to light a fire beneath the pot. The Lakota people call the constellation Wičhákhiyuhapi, or "Great Bear". The Wampanoag people (Algonquian) referred to Ursa Major as "maske", meaning "bear" according to Thomas Morton in The New England Canaan. The Wasco-Wishram Native Americans interpreted the constellation as five wolves and two bears that were left in the sky by Coyote. To Norse pagans, the Big Dipper was known as Óðins vagn, "Woden's wagon". Likewise Woden is poetically referred to by Kennings such as vagna verr 'guardian of the wagon' or vagna rúni 'confidant of the wagon' In the Finnish language, the asterism is sometimes called by its old Finnish name, Otava. The meaning of the name has been almost forgotten in Modern Finnish; it means a salmon weir. Ancient Finns believed the bear (Ursus arctos) was lowered to earth in a golden basket off the Ursa Major, and when a bear was killed, its head was positioned on a tree to allow the bear's spirit to return to Ursa Major. In the Sámi languages of Northern Europe, part of the constellation (i.e. the Big Dipper minus Dubhe and Merak, is identified as the bow of the great hunter Fávdna (the star Arcturus). In the main Sámi language, North Sámi, it is called Fávdnadávgi ("Fávdna's Bow") or simply dávggát ("the Bow"). The constellation features prominently in the Sámi anthem, which begins with the words Guhkkin davvin dávggaid vuolde sabmá suolggai Sámieanan, which translates to "Far to the north, under the Bow, the Land of the Sámi slowly comes into view." The Bow is an important part of the Sámi traditional narrative about the night sky, in which various hunters try to chase down Sarva, the Great Reindeer, a large constellation that takes up almost half the sky. According to the legend, Fávdna stands ready to fire his Bow every night but hesitates because he might hit Stella Polaris, known as Boahji ("the Rivet"), which would cause the sky to collapse and end the world. In Burmese, Pucwan Tārā (ပုဇွန် တာရာ, [bəzʊ̀ɴ tàjà]) is the name of a constellation comprising stars from the head and forelegs of Ursa Major; pucwan (ပုဇွန်) is a general term for a crustacean, such as prawn, shrimp, crab, lobster, etc. In Javanese, it is known as "lintang jong", which means "the jong constellation". Likewise, in Malay it is called "bintang jong". In Theosophy, it is believed that the Seven Stars of the Pleiades focus the spiritual energy of the seven rays from the Galactic Logos to the Seven Stars of the Great Bear, then to Sirius, then to the Sun, then to the god of Earth (Sanat Kumara), and finally through the seven Masters of the Seven Rays to the human race. In culture Ursa Major is mentioned by such poets as Homer, Spenser, Shakespeare, Tennyson and also by Federico Garcia Lorca, in "Song for the Moon". Ancient Finnish poetry also refers to the constellation, and it features in the painting Starry Night Over the Rhône by Vincent van Gogh. Graphic visualisation In European star charts, the constellation was visualized with the 'square' of the Big Dipper forming the bear's body and the chain of stars forming the Dipper's "handle" as a long tail. However, bears do not have long tails, and Jewish astronomers considered Alioth, Mizar, and Alkaid instead to be three cubs following their mother, while the Native Americans saw them as three hunters. Noted children's book author H. A. Rey, in his 1952 book The Stars: A New Way to See Them, (ISBN 0-395-24830-2) had a different asterism in mind for Ursa Major, that instead had the "bear" image of the constellation oriented with Alkaid as the tip of the bear's nose, and the "handle" of the Big Dipper part of the constellation forming the outline of the top of the bear's head and neck, rearwards to the shoulder, potentially giving it the longer head and neck of a polar bear. Ursa Major is also pictured as the Starry Plough, the Irish flag of Labour, adopted by James Connolly's Irish Citizen Army in 1916, which shows the constellation on a blue background; on the state flag of Alaska; and on the House of Bernadotte's variation of the coat of arms of Sweden. The seven stars on a red background of the flag of the Community of Madrid, Spain, may be the stars of the Plough asterism (or of Ursa Minor). The same can be said of the seven stars pictured in the bordure azure of the coat of arms of Madrid, capital of that country. See also Notes References Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/DR-DOS] | [TOKENS: 8774] |
Contents DR-DOS DR-DOS[nb 1] is a disk operating system for IBM PC compatibles, originally developed by Gary A. Kildall's Digital Research, Inc. and derived from Concurrent PC DOS 6.0, which was an advanced successor of CP/M-86. Upon its introduction in 1988, it was the first DOS that attempted to be compatible with IBM PC DOS and MS-DOS. Its first release was version 3.31, named so that it would match MS-DOS's then-current version. DR DOS 5.0 was released in 1990 as the first to be sold in retail; it was critically acclaimed and led to DR DOS becoming the main rival to Microsoft's MS-DOS, who quickly responded with its own MS-DOS 5.0 but releasing over a year later. It introduced a graphical user interface layer called ViewMAX. DR DOS 6.0 was released in 1991; then with Novell's acquisition of Digital Research, the following version was named Novell DOS 7.0 in 1994. After another sale, to Caldera, updated versions were released partly open-source under the Caldera moniker, and briefly as OpenDOS. The last version for desktops, Caldera DR-DOS 7.03, was released in 1999, after which the software was sold to Embedded Systems by Caldera and then by DeviceLogics. History Digital Research's original CP/M for the 8-bit Intel 8080- and Z80-based systems spawned numerous spin-off versions, most notably CP/M-86 for the Intel 8086/8088 family of processors. Although CP/M had dominated the market since the mid-1970s, and was shipped with the vast majority of non-proprietary-architecture personal computers, the IBM PC in 1981 brought the beginning of what was eventually to be a massive change. IBM originally approached Digital Research in 1980, seeking an x86 version of CP/M. However, there were disagreements over the contract, and IBM withdrew. Instead, a deal was struck with Microsoft, who purchased another operating system, 86-DOS, from Seattle Computer Products (SCP). This became Microsoft MS-DOS and IBM PC DOS. 86-DOS's command structure and application programming interface imitated that of CP/M 2.2 (with BDOS 2.2). Digital Research threatened legal action, claiming PC DOS/MS-DOS to be too similar to CP/M. In early 1982, IBM settled by agreeing to sell Digital Research's x86 version of CP/M, CP/M-86, alongside PC DOS. However, PC DOS sold for US$40 while CP/M-86 had a $240 price tag. The proportion of PC buyers prepared to spend six times as much to buy CP/M-86 was very small, and the limited availability of compatible application software, at first in Digital Research's favor, was only temporary. Digital Research fought a long losing battle to promote CP/M-86 and its multi-tasking multi-user successors MP/M-86 and Concurrent CP/M-86, and eventually decided that they could not beat the Microsoft-IBM lead in application software availability, so they modified Concurrent CP/M-86 to allow it to run the same applications as MS-DOS and PC DOS. This was shown publicly in December 1983 and shipped in March 1984 as Concurrent DOS 3.1 (a.k.a. CDOS with BDOS 3.1) to hardware vendors. While Concurrent DOS continued to evolve in various flavors over the years to eventually become Multiuser DOS and REAL/32, it was not specifically tailored for the desktop market and too expensive for single-user applications. Therefore, over time two attempts were made to sideline the product: In 1985, Digital Research developed DOS Plus 1.0 to 2.1, a stripped-down and modified single-user derivative of Concurrent DOS 4.1 and 5.0, which ran applications for both platforms, and allowed switching between several tasks as did the original CP/M-86. Its DOS compatibility was limited, and Digital Research made another attempt, this time a native DOS system. This new disk operating system was launched in 1988 as DR DOS. Although DRI was based in Pacific Grove and later in Monterey, California, USA, the work on DOS Plus started in Newbury, Berkshire in the UK, where Digital Research Europe had its OEM Support Group located since 1983.[nb 2] Beginning in 1986, most of the operating system work on Concurrent DOS 386 and XM, Multiuser DOS, DR DOS and PalmDOS was done in Digital Research's European Development Centre (EDC) in Hungerford, Berkshire.[nb 2] Later on some work was also done by Digital Research GmbH in Munich, Germany. As requested by several OEMs, Digital Research started a plan to develop a new DOS operating system addressing the defects left by MS-DOS in 1987. Of particular importance was a million dollar deal with Kazuhiko "Kay" Nishi of ASCII Corporation, who had previously been instrumental in opening the Japanese OEM market for Microsoft. The first DR DOS version was released on May 28, 1988. Version numbers were chosen to reflect features relative to MS-DOS; the first version promoted to the public was DR DOS 3.31, which offered features comparable to Compaq MS-DOS 3.31 with large disk support (FAT16B a.k.a. "BIGDOS"). DR DOS 3.31 reported itself as "IBM PC DOS 3.31", while the internal BDOS (Basic Disk Operating System) kernel version was reported as 6.0, single-user nature, reflecting its origin as derivative of Concurrent DOS 6.0 with the multitasking and multiuser capabilities as well as CP/M API support stripped out and the XIOS replaced by an IBM-compatible DOS-BIOS. The system files were named DRBIOS.SYS (for the DOS-BIOS) and DRBDOS.SYS (for the BDOS kernel), the disk OEM label used was "DIGITAL␠". DR DOS offered some extended command line tools with command line help, verbose error messages, sophisticated command line history and editing (HISTORY directive) as well as support for file and directory passwords built right into the kernel. It was also cheaper to license than MS-DOS, and was ROMable right from the start. The ROMed version of DR DOS was also named ROS (ROM Operating System). DRI was approached by a number of PC manufacturers who were interested in a third-party DOS, which prompted several updates to the system. At this time, MS-DOS was only available to OEMs bundled with hardware. Consequently, DR DOS achieved some immediate success when it became possible for consumers to buy it through normal retail channels beginning with version 3.4x. Known versions are DR DOS 3.31 (BDOS 6.0, June 1988, OEM only), 3.32 (BDOS 6.0, August 17, 1988, OEM only), 3.33 (BDOS 6.0, September 1, 1988, OEM only), 3.34 (BDOS 6.0, OEM only), 3.35 (BDOS 6.0, October 21, 1988, OEM only), 3.40 (BDOS 6.0, January 25, 1989), 3.41 (BDOS 6.3, June 1989, OEM and retail). Like MS-DOS, most of them were produced in several variants for different hardware. While most OEMs kept the DR DOS name designation, 2001 Sales, Inc. marketed it under the name EZ-DOS 3.41 (also known as EZ-DOS 4.1). DR DOS version 5.0 (code-named "Leopard") was released in May 1990, still reporting itself as "PC DOS 3.31" for compatibility purposes, but internally indicating a single-user BDOS 6.4 kernel. (Version 4 was skipped to avoid being associated with the relatively unpopular MS-DOS 4.0.) This introduced ViewMAX, a GEM-based GUI file management shell. ViewMAX's startup screen would present the slogan "Digital Research - We make computers work". DR DOS 5.0 also introduced the patented BatteryMAX power management system, bundled disk-caching software (DRCACHE), a remote file transfer tool (FILELINK), a cursor shape configuration utility (CURSOR), and offered a vastly improved memory management system (MemoryMAX). For compatibility purposes, the DR DOS 5.0 system files were now named IBMBIO.COM (for the DOS-BIOS) and IBMDOS.COM (for the BDOS kernel) and due to the advanced loader in the boot sector could be physically stored anywhere on disk. The OEM label in the boot sectors was changed to "IBM␠␠3.3". DR DOS 5.0 was the first DOS to include load-high capabilities. The kernel and data structures such as disk buffers could be relocated in the High Memory Area (HMA), the first 64 KB of extended memory which are accessible in real mode. This freed up the equivalent amount of critical "base" or conventional memory, the first 640 KB of the PC's RAM – the area in which all DOS applications run. Additionally, on Intel 80386 machines, DR DOS's EMS memory manager allowed the operating system to load DOS device drivers into upper memory blocks, further freeing base memory. DR DOS 5.0 was the first DOS to integrate such functionality into the base OS (loading device drivers into upper memory blocks was already possible using third-party software like QEMM). This allowed it, on 286 systems with supported chipsets and on 386 systems, to provide significantly more free conventional memory than any other DOS. Once drivers for a mouse, multimedia hardware and a network stack were loaded, an MS-DOS/PC DOS machine typically might only have had 300 to 400 KB of free conventional memory – too little to run much late-1980s software. In contrast to this, DR DOS 5.0, with a little manual tweaking, could load all this and still keep all of its conventional memory free – allowing for some necessary DOS data structures, as much as 620 KB out of the 640 KB. With MEMMAX +V, the conventional memory region could even be extended into unused portions of the graphics adapter card typically providing another 64 to 96 KB more free DOS memory. Because DR DOS left so much conventional memory available, some old programs using certain address wrapping techniques failed to run properly as they were now loaded unexpectedly (or, under MS-DOS, "impossibly") low in memory – inside the first 64 KB segment (known as "low memory"). Therefore, DR DOS 5.0's new MEMMAX -L command worked around this by pre-allocating a chunk of memory at the start of the memory map in order for programs to load above this barrier (but with less usable conventional memory then). By default, MEMMAX was configured for +L, so that applications could take advantage of the extra memory. Faced with substantial competition in the DOS arena, Microsoft responded with an announcement of a yet-to-be released MS-DOS 5.0 in May 1990. This would be released in June 1991 and include similar advanced features to those of DR DOS. It included matches of the DR's enhancements in memory management. Almost immediately in September 1991, Digital Research responded with DR DOS 6.0, code-named "Buxton". DR DOS 6.0, while already at BDOS level 6.7 internally, would still report itself as "IBM PC DOS 3.31" to normal DOS applications for compatibility purposes. This bundled in SuperStor on-the-fly disk compression, to maximize available hard disk space, and file deletion tracking and undelete functionality by Roger A. Gross. DR DOS 6.0 also included a task-switcher named TASKMAX with support for the industry-standard task-switching API to run multiple applications at the same time. In contrast to Digital Research's Multiuser DOS (successor of Concurrent DOS in the multi-user products line), which would run DOS applications in pre-emptively multitasked virtual DOS machines, the DR DOS 6.0 task switcher would freeze background applications until brought back into the foreground. While it ran on x86-machines, it was able to swap to XMS memory on 286+ machines. TASKMAX did support some Copy & Paste facility between applications. Via the task-switcher API, graphical user interfaces such as ViewMAX or PC/GEOS could register as the task manager menu and thereby replace the TASKMAX text mode menu, so that users could switch between tasks from within a GUI. Microsoft responded with MS-DOS 6.0, which again matched some features of DR DOS 6.0. In December 1991, a pre-release version of Windows 3.1 was found to return a non-fatal error message if it detected a non-Microsoft DOS. This check came to be known as the AARD code. It was a simple matter for Digital Research to patch DR DOS 6.0 to circumvent the AARD code 'authenticity check' in the Windows 3.1 beta by rearranging the order of two internal tables in memory (with no changes in functionality), and the patched version, named "business update", was on the streets within six weeks of the release of Windows 3.1. With the detection code disabled, Windows ran perfectly under DR DOS and its successor Novell DOS. The code was present but disabled in the released version of Windows 3.1. In July 1992, Digital Research Japan released DR DOS 6.0/V, a Japanese DOS/V compatible version of DR DOS 6.0. A Korean version appears to have been available as well. In 1992 Digital Research, still under its old name but already bought by Novell in July 1991, also embarked on a spin-off product code-named "Merlin" and later released as NetWare PalmDOS 1, which, as its name implies, was a very resource-light DR DOS 6.0 derivative aimed at the emerging Palmtop/PDA market. PalmDOS was the first operating system in the family to support the new BDOS 7.0 kernel with native DOS compatible internal data structures instead of emulations thereof. Replacing the DOS emulation on top of a CP/M kernel by a true DOS compatible kernel helped a lot in improving compatibility with some applications using some of DOS' internal data structures and also was the key in reducing the resident size of the kernel code even further—a particular requirement for the PDA market. On the other hand, introducing a genuine Current Directory Structure (CDS) imposed a limit on the depth of working directories down to 66 characters (as in MS-DOS/PC DOS), whereas previous issues of DR DOS had no such limitation due to their internal organization of directories as relative links to parent directories instead of as absolute paths. PalmDOS still reported itself as "PC DOS 3.31" to applications in order to keep the kernel small and not run into compatibility problems with Windows, which would expect the DOSMGR API to be implemented for any DOS version since 5.0. As well as a ROM-executing kernel, PalmDOS had palmtop-type support for features such as PCMCIA PC Cards (with DPMS support), power management (BatteryMAX and the $IDLE$ device driver with its patented dynamic idle detection by Gross and John P. Constant), MINIMAX task switcher support for PIM (Personal Information Modules) applications stored and executed from ROM via XIP (Execute-In-Place), etc. The PCMCIA stack for PalmDOS was partially written by Ian H. S. Cullimore, the original instigator of the PCMCIA/PC Card movement. Novell DOS was Novell Corporation's name for DR DOS during the period when Novell sold DR DOS, after the acquisition of Digital Research in 1991. Regarding features and performance, it was typically at least one release ahead of MS-DOS. In 1993, PC DOS 6.1, MS-DOS 6.2 and PC DOS 6.3 were trumped by Novell's DOS 7. Novell CEO Robert J. Frankenberg's strategy included "major trimming", selling off products like transactional database Btrieve and killing others such as Novell DOS and WordPerfect's multimedia Main Street children's titles. Novell licensed technology from Stac Electronics for use in Novell DOS and its network operating system NetWare. Novell sold the product line off to Caldera on July 23, 1996, after it approached Novell looking for a DOS operating system to bundle with its OpenLinux distribution. Marc Perkel claimed to have had inspired Novell in February 1991 to buy Digital Research and develop something he envisioned as "NovOS". Novell had actually bought Digital Research in July 1991 with a view to using DR's product line as a lever in their comprehensive strategy to break the Microsoft monopoly. (This was part of a massive and ultimately disastrous spending spree for Novell: they bought WordPerfect Corporation at about the same time, some of Borland's products, and invested heavily in Unix as well.) The planned "DR DOS 7.0", internally named "Panther", intended to trump Microsoft's troubled MS-DOS 6.0, was repeatedly delayed, while Novell was working on an optionally loadable Unix-like multi-user security extension (with, if loaded, file commands like BACKUP, DELPURGE, MOVE, TOUCH, TREE, UNDELETE, XATTRIB, XCOPY, XDEL and XDIR supporting an otherwise disabled /U:name command line option to select specific users or groups, compatible with Multiuser DOS) and two new graphical user interfaces (ViewMAX 3, a derivative of GEM, and "Star Trek", a true port of Apple's System 7.1 to run under the new DR DOS multitasker named "Vladivar"). When DR DOS eventually arrived in December 1993 (with localized versions released in March 1994), renamed Novell DOS 7 (a.k.a. "NWDOS"), and without these three components, it was a disappointment to some. It was larger and lacked some finishing touches, but was nevertheless seen as best DOS by many industry experts. In Germany, Novell DOS 7 was aggressively marketed with the slogan "Trau keinem DOS unter 7" (Don't trust any DOS below 7) in the press and with free demo floppies in computer magazines. The campaign aimed at 20% of the DOS market and resulted in about 1.5 million copies sold until February 1994 and more than 3000 dealers interested to carry the product. Novell DOS 7 was available through various OEMs, a dedicated mail order shop and authorized dealers. A major functional addition was Novell's second attempt at a peer-to-peer networking system, Personal NetWare (PNW).[nb 3] This was better than its predecessor, NetWare Lite (NWL), but it was incompatible with Microsoft's networking system, now growing popular with support in Windows for Workgroups, OS/2, and Windows NT. A considerable amount of manual configuration was needed to get both to co-exist on the same PC, and Personal NetWare never achieved much success. Since Novell DOS 7 implemented the DOSMGR API and internal data structures had been updated, its BDOS 7.2 kernel could report with a DOS version of 6.0 and OEM ID "IBM" without risking compatibility problems with Windows. Most tools would report this as "PC DOS 6.1", because IBM PC DOS 6.1 also reported as DOS 6.0 to applications. Novell DOS 7 introduced much advanced memory management including new support for DPMI (DOS Protected Mode Interface) and DPMS (DOS Protected Mode Services) as well as more flexible loadhigh options. It also introduced support for "true" pre-emptive multitasking of multiple DOS applications in virtual DOS machines (VDM), a component originally named MultiMAX. This was similar to Multiuser DOS, but now on the basis of a natively DOS compatible environment, similar to Windows 386 Enhanced Mode, but without a GUI. By default, the bundled TASKMGR would behave similar to the former DR DOS 6.0 TASKMAX. However, if EMM386 was loaded with the option /MULTI, EMM386 would load a natively 32-bit 386 Protected Mode operating system core providing API support for pre-emptive multitasking, multi-threading, hardware virtualization and domain management of virtual DOS machines. This API could be used by DR DOS-aware applications. If TASKMGR was run later on, it would use this API to instance the current 16-bit DOS system environment, create virtual DOS machines and run applications in them instead of using its own Real Mode task-switcher support. The multitasker was compatible with Windows, so that tasks started before launching Windows could be seen as tasks under Windows as well. Novell DOS 7 and Personal NetWare 1.0 also shipped with NetWars, a network-enabled 3D arcade game. Novell DOS 7 and Personal NetWare required several bug-fix releases (D70xyy with x=language, yy=number) and were not completely stable when the next development occurred. With beta versions of Microsoft's "Chicago" (what would later become Windows 95) in sight, Novell wound down further development on Novell DOS 7 in September 1994 and stopped maintenance in January 1996 after more than 15 updates. When Caldera approached Novell looking for a DOS operating system to bundle with their OpenLinux distribution, Novell sold the product line off to Caldera on July 23, 1996, by which time it was of little commercial value to them. Between the Caldera-owned DR-DOS and competition from IBM's PC DOS 6.3, Microsoft moved to make it impossible to use or buy the subsequent Windows version, Windows 95, with any DOS product other than their own. Claimed by them to be a purely technical change, this was later to be the subject of a major lawsuit brought in Salt Lake City by Caldera with the help of the Canopy Group. Microsoft lawyers tried repeatedly to have the case dismissed but without success. Immediately after the completion of the pre-trial deposition stage (where the parties list the evidence they intend to present), there was an out-of-court settlement on January 7, 2000, for an undisclosed sum. This was revealed in November 2009 to be $280 million. In August 1996, the US-based Caldera, Inc. was approached by Roger A. Gross, one of the original DR-DOS engineers, with a proposal to restart DR-DOS development and to make Windows 95 run on DR-DOS which would help the court case. Following a meeting in September 1996 in Lindon, Utah, USA, between Gross, Ransom H. Love, Bryan Wayne Sparks and Raymond John Noorda, Gross was hired and tasked to set up a new subsidiary in the UK.[nb 2] On September 10, 1996, Caldera announced the coming release of OpenDOS (COD) and their intent to also release the source code to the system, and Caldera UK Ltd. was incorporated on September 20, 1996.[nb 2] Gross hired some of the original developers of the operating system from the Novell EDC as well as some new talents to continue work on the operating system in a converted barn at the periphery of Andover, Hampshire, UK,[nb 2] nearby the former Digital Research and Novell EDC.[nb 2] Besides other improvements and enhancements all over the system, a string of new key features were added subsequently over the course of the next two years, including a TCP/IP stack (derived from LAN WorkPlace for DOS / NetWare Mobile), a graphical 32-bit DOS Protected Mode HTML 3.2 web-browser DR-WebSpyder (originally based on source code from the Arachne web browser by Michal Polák) with LAN and modem dialup, a POSIX Pthreads extension to the multi-tasker by Andy T. Wightman, long filename (LONGNAME) support by Edward N. Hill Jr., as well as LBA and FAT32 support (DRFAT32) by Matthias R. Paul. Gross also hired Andrew Schulman (who had been, with Geoff Chappell, instrumental in identifying the AARD code in 1992) to work as a consultant and, in Andover, assist Paul in his work on "WinGlue", a secret project to create a version of DR-DOS compatible with Windows 95, 98 and 98 SE and replace its MS-DOS 7.xx component. This was demonstrated at CeBIT in March 1998, and later, in a small team, developed into "WinBolt", both versions of DR-DOS, which remained unreleased as of 2023[update], but played an important role in the court case. Caldera UK officially released Caldera OpenDOS 7.01 on February 3, 1997, but this version was just Novell DOS 7 update 10 (as of December 1994) compiled only with the necessary adaptations to incorporate the new name in display messages as well as in environment variables and file names. It was missing a year's worth of patches which had been developed for the Novell DOS updates 11 (January 1995) to 15.2 (January 1996). This was due to parts of the Novell DOS sources having been lost at Novell meanwhile. Consequently, this version still reported an internal BDOS version of 7.2, identical to Novell DOS 7. The new suite also lacked the SETFIFO command, which had been added with one of the Novell DOS updates, as well as Fifth Generation's Search&Destroy virus scanner and FastBack Plus 2.0 utility, which previously came bundled with Novell DOS. Instead it came bundled with a newer version of PNUNPACK and brought a much advanced version of NetWars. Parts of OpenDOS 7.01 were released as open source in form of the M.R.S. kit (for Machine Readable Sources) in May 1997, but with license terms mostly incompatible with existing open-source licenses. The source was then closed again as Gross felt this would undermine the commercial aspirations of the system. After beta releases in September and November 1997, the next official release came in December 1997, with the name changed to Caldera DR-OpenDOS 7.02, soon followed by a further release in March 1998, when the DR-DOS name returned as Caldera DR-DOS 7.02, now for the first time written with a hyphen. Version 7.02 (now reporting itself as BDOS 7.3) incorporated improved BIOS and BDOS issues, developed by Paul, adding many new boot and configuration options, integrating many compatibility enhancements, bug-fixes and optimizations for size and speed, and re-implementing all fixes of the missing Novell DOS updates. The BIOS improved the coexistence of DR-DOS with Windows 9x and its support for third-party disk compression drivers such as Microsoft's DriveSpace. It introduced a diagnostics mode (activated by Scroll Lock), integrated debugger support (with DEBUG=ON and a debugger loaded before or from within CONFIG.SYS) and more flexible CONFIG.SYS tracing capabilities via the F5/F6/F7/F8 hotkeys and the TRACE and TIMEOUT commands, thereby also improving the integration of alternative command line shells such as 4DOS. Together with LOADER, SYS /DR:ext and the CHAIN directive, it brought enhanced multi-configuration support for DR/D/CONFIG.ext files and came with enhancements to the BASIC-like CONFIG.SYS language for more powerful boot menus, convenient user interaction and programmatical acting upon conditions (CPU386), return codes and error levels (ERROR, ONERROR). It also allowed to change the SCROLLOCK, CAPSLOCK, INSERT and VERIFY settings as well as the SWITCHAR, YESCHAR, NOCHAR and RESUMECHAR characters. Various behavioural details could be controlled with new parameters /Q (Quiet), /L (Lowercase), /Y (Yes) and /S (Switch) for SWITCHES. Further, it provided optional support for a LPT4: device and allowed to configure the built-in COMx: and LPTx: devices as well as to change the PRN: and AUX: defaults. The handling of environment variables in CONFIG.SYS was improved and new load-high facilities included such as the HIFILES/FILESHIGH and HIFCBS/FCBSHIGH options to relocate file handles and FCB structures into UMBs, which typically gave between 1 and 4 KB (and up to 15 KB) more free conventional memory compared to previous versions, or the HISHELL/SHELLHIGH SIZE directive to control the pre-allocation of HMA memory for COMMAND.COM, which helped to avoid memory fragmentation and thereby typically gave between 5 and 8 KB more continuous HMA memory for HMA-capable third-party drivers to work with in conjunction with third-party command line shells, which could not load into the HMA as COMMAND.COM with its /MH option. At a reduced memory footprint version 7.02 also brought an enhanced NLS 4.xx sub-system by Paul to allow multiple, distributed and possibly user-configured COUNTRY.SYS files to be used by the system at the same time in a hierarchical model. This also gave dynamic parser support for MS-DOS/PC DOS COUNTRY.SYS file formats in addition to DR-DOS' own COUNTRY.SYS formats, and it introduced support for the ISO 8601 international date format (including automatic detection) and the then-new Euro currency. Some DR-DOS files such as IBMBIO.COM, IBMDOS.COM and COUNTRY.SYS carried misleading file extensions for compatibility reasons; with DR-DOS 7.02 they were enhanced to incorporate a fat binary-style safety feature devised by Paul so that they would exit gracefully when called inappropriately. DR-DOS 7.02 was fully Year 2000 compliant and provided special support to work with buggy system BIOSes. It also came with an updated FDISK, which could partition and format FAT32 volumes (but not yet work with LBA). The sources of the Novell patches for the external tools and drivers had meanwhile been found in Germany and could thus be retro-fitted into the system as well, so that DR-DOS 7.02 finally not only caught up with Novell DOS 7, but was a true step forward. The release was followed by various updates in June, August and September 1998. The updated internal BDOS version number introduced a new problem: some legacy third-party applications with special support for Novell DOS, which were no longer being updated, stopped working. SETVER already allowed Novell DOS to disguise itself as DOS versions by file name and globally and, specifying a magic sub-version of 255, it would even disable its own internal BDOS version check in order to cope with programs specifically probing for "DR-DOS". The modified kernel and SETVER driver by Paul would, in an hierarchical model, also support load paths in order to distinguish between multiple executables of the same file name, and it introduced an extended mode, in which SETVER could not only fake DOS versions, but also BDOS kernel versions. Sub-versions of 128 to 255 would be reported as DOS sub-versions 0 to 127 to applications, but with the BDOS version check disabled, while sub-versions 100 to 127 could be used to fake different BDOS versions, whereas the DOS revision number (typically set to 0 in a static, pre-boot patchable data structure) would be taken as the reported sub-version instead, so that SETVER /G /X 6.114 would allow versions of DR-DOS since 7.02 to still report themselves as a "DOS 6.0" and with a faked BDOS version 7.2 (114 decimal = 72 hexadecimal), thereby masquerading as Novell DOS 7 / OpenDOS 7.01. While otherwise beneficial, the new HIFILES triggered a compatibility problem in the DOS-UP feature of the third-party memory manager QEMM 8, which was hard-wired to expect a chunk of five handle structures in conventional memory under DR-DOS (as with previous versions up to 7.01), whereas version 7.02 by design left eight handles in low memory when loading high files in order to maintain full compatibility with older versions of Windows 3.xx. Compatibility with Windows for Workgroups 3.11 had not been affected by this. A maintenance fix was devised to patch a single byte in IBMBIO.COM in order to switch the behaviour and optionally re-invoke the old chunking. This freed some 150 bytes of conventional memory and enabled full compatibility with DOS-UP, but at the same time broke compatibility with older versions of Windows 3.xx when using the HIFILES feature, and vice versa. The patch named IBMBIO85.SCR continued to work with newer versions of DR-DOS. In August 1998 the US-based Caldera, Inc. created two new subsidiaries, Caldera Systems, Inc. for the Linux business, and Caldera Thin Clients, Inc. for the embedded and thin-client market. Another version, DR-DOS 7.03 (still with BDOS 7.3 and reporting itself to applications as "PC DOS 6.0" for compatibility purposes), was pre-released at Christmas 1998 and then officially released on January 6, 1999, by Caldera UK. It came with significantly improved memory managers (in particular enhanced DPMI support in conjunction with the multitasker) and other enhancements, such as added DEVLOAD and DRMOUSE utilities, but a changed OEM label in the boot sector of volumes formatted under DR-DOS could also cause problems under other operating systems (which can be circumvented by NOVOLTRK). DR-DOS 7.03 would become the last version of DR-DOS also tailored for desktop use. Caldera, Inc. wanted to relocate the DR-DOS business into the US and closed the highly successful UK operation in February 1999 after Gross resigned and set up iCentrix to develop the MarioNet split web browser. Development was then moved into the US (which never worked out due to a total lack of expertise in this field at Caldera US), and the DR-DOS line fell to its branch company, Caldera Thin Clients, which was renamed Lineo, Inc. on July 20, 1999. DR-WebSpyder was renamed Embrowser and was said to be ported to Linux. Lineo re-released DR-DOS 7.03 in June and September 1999, still branded as "Caldera DR-DOS" and without any changes, but otherwise focussed on Linux for embedded systems, based on a stripped-down version of OpenLinux named Embedix. Among the latest and independently developed versions of DR-DOS were OEM DR-DOS 7.04 (as of August 19, 1999) and 7.05 (as of November 30, 1999), still branded as "Caldera DR-DOS". These were variants of the system consisting only of the kernel and command shell. With a specialized native implementation of FAT32 and large hard disk support they could be found bundled with Ontrack's Easy Recovery 5 in 2000, replacing the dynamically loadable DRFAT32 redirector driver, which still came with Easy Recovery 4. They were also used for Seagate Technology's SeaTools and the CD imaging software Nero Burning ROM. While still reporting a BDOS 7.3 internally, these were the first versions to report themselves as "PC DOS 7.10" to applications in order to indicate integrated FAT32 support. Designed to be mostly backwards-compatible, the DR-DOS 7.04/7.05 IBMBIO.COM could be combined with the DR-DOS 7.03 IBMDOS.COM in order to give the desktop-approved DR-DOS 7.03 kernel LBA capabilities and work with drives larger than 8 GB. For specific OEM requirements, DR-DOS 7.06 (as of December 14, 1999) by Wightman combined the kernel files into a single binary executable, so that, similar to IO.SYS of Windows 98, it could be booted by MS-DOS 7.10 boot sectors (but no longer by DR-DOS boot sectors). DR-DOS 7.07 (with BDOS 7.4/7.7) by Paul introduced new bootstrap loaders and updated disk tools in order to combine support for CHS and LBA disk access, the FAT12, FAT16 and FAT32 file systems, and the differing bootstrapping conventions of DR-DOS, PC DOS, MS-DOS, Windows, REAL/32 and LOADER into a single NEWLDR MBR and boot sector, so that the code would continue to load any version of DR-DOS down to 3.31 (and since DR-DOS 7.04 also with FAT32 support), but could also be used to launch the PC DOS or MS-DOS system files, including those of Windows 9x and PC DOS 7.10. At the same time the kernel could not only be booted by the new sectors, but also by any previously DR-DOS formatted disks, as well as off disks with existing PC DOS or MS-DOS boot sectors and a variety of other boot-loaders, thereby easing the coexistence and setup of multi-boot scenarios in conjunction with other operating systems. In 2002, Lineo was bought out, and some of Lineo's former managers purchased the name and formed a new company, DRDOS, Inc. dba DeviceLogics L.L.C. They have continued to sell DR-DOS for use in embedded systems. DR-DOS 8.0 was released on March 30, 2004, featuring FAT32 and large disk support, the ability to boot from ROM or Flash, multitasking and a DPMI memory manager. This version was based on the kernel from version 7.03. The company later released DR-DOS 8.1 (with better FAT32 support) in autumn 2005. This version was instead based on OpenDOS 7.01.xx. DR-DOS 8.1 was withdrawn for GPL violations (see Controversies). Aside from selling copies of the operating system, the DRDOS, Inc. website lists a buyout option for DR-DOS; the asking price is US$25000. The OpenDOS 7.01 source code was a base for The DR-DOS/OpenDOS Enhancement Project, set up in July 2002 in an attempt to bring the functionality of DR-DOS up to parity with modern PC non-Windows operating systems. The project's added native support for large disks (LBA) and the FAT32 file system, and several other enhancements, including improved memory management and support for the new FAT32+ file system extension which allows files of up to 256 GB in size on normal FAT partitions. DR-DOS 7.01.08 WIP (work in progress) was released on July 21, 2011. From 2023 on the last Enhanced DR-DOS release 7.01.08 WIP was ported to an open source build tool chain, which makes the kernel and command interpreter cross-buildable from operating systems other than DOS. The kernel can be built as a single binary KERNEL.SYS to make it compatible with boot loaders supporting the FreeDOS kernel. It received several bug fixes and updates and as of October 2024 is under active maintenance. Controversies In October 2005, it was discovered that DR-DOS 8.1 included several utilities from FreeDOS as well as other sources, and that the kernel was an outdated version of the Enhanced DR-DOS kernel. DR DOS, Inc. failed to comply with the GNU General Public License (GPL) by not crediting the FreeDOS utilities to their authors and including the source code. After complaints from FreeDOS developers (including the suggestion to provide the source code, and hence comply with the GPL), DR DOS, Inc. instead withdrew version 8.1, and also the unaffected 8.0, from its website. Commands APPEND, ASSIGN, BATCH, DBG, DELQ, ERA, ERAQ, MORE and SUBST have been among the internal commands supported since DR DOS 3.31. DR DOS 5.0 removed BATCH and added HILOAD. GOSUB, IDLE, RETURN and SWITCH were added as internal commands with DR DOS 6.0. ASSIGN and SUBST were changed to become external commands with DR DOS 6.0. ECHOERR and PAUSEERR existed as internal commands in DR DOS 6.0 (and in Multiuser DOS), but were not normally enabled. MORE remained an internal command up to including PalmDOS, but was changed to an external command with Novell DOS 7. DBG was removed with Novell DOS 7, LOADHIGH, LH and TRUENAME were added as internal commands. APPEND[citation needed] was still an internal command in DR DOS 6.0, but was changed to an external command with Novell DOS 7. The following list of internal commands is supported by DR DOS 6.0: Batch processing subcommands of DR DOS 6.0 include: DR DOS 6.0 supports the following external commands: See also Notes References Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/World_Wide_Web_Consortium] | [TOKENS: 1847] |
Contents World Wide Web Consortium The World Wide Web Consortium (W3C) is the main international standards organization for the World Wide Web. Founded in 1994 by Tim Berners-Lee, the consortium is made up of member organizations that maintain full-time staff working together in the development of technical standards for the World Wide Web. As of May 2025,[update] W3C has 350 members. The organization has been led by CEO Seth Dobbs since October 2023. W3C also engages in education and outreach, develops software and serves as an open forum for discussion about the Web. History The World Wide Web Consortium (W3C) was founded in 1994 by Tim Berners-Lee after he left the European Organization for Nuclear Research (CERN) in October 1994. It was founded at the Massachusetts Institute of Technology (MIT) Laboratory for Computer Science with support from the European Commission, and the Defense Advanced Research Projects Agency, which had pioneered the ARPANET, the most direct predecessor to the modern Internet. It was located in Technology Square until 2004, when it moved, with the MIT Computer Science and Artificial Intelligence Laboratory, to the Stata Center. The organization tries to foster compatibility and agreement among industry members in the adoption of new standards defined by the W3C. Incompatible versions of HTML are offered by different vendors, causing inconsistency in how web pages are displayed. The consortium tries to get all those vendors to implement a set of core principles and components that are chosen by the consortium. It was originally intended that CERN host the European branch of W3C; however, CERN wished to focus on particle physics, not information technology. In April 1995, the French Institute for Research in Computer Science and Automation became the European host of W3C, with Keio University Research Institute at SFC becoming the Asian host in September 1996. Starting in 1997, W3C created regional offices around the world. As of September 2009, it had eighteen World Offices covering Australia, the Benelux countries (Belgium, Netherlands and Luxembourg), Brazil, China, Finland, Germany, Austria, Greece, Hong Kong, Hungary, India, Israel, Italy, South Korea, Morocco, South Africa, Spain, Sweden, and, as of 2016, the United Kingdom and Ireland. In 2010, Jeffrey M. Jaffe was named CEO of W3C. He continued in that position until 2022. In October 2012, W3C convened a community of major web players and publishers to establish a MediaWiki wiki that seeks to document open web standards called the WebPlatform and WebPlatform Docs. In January 2013, Beihang University became the Chinese host. In 2022 the W3C WebFonts Working Group won an Emmy Award from the National Academy of Television Arts and Sciences for standardizing font technology for custom downloadable fonts and typography for web and TV devices. On 1 January 2023, it reformed as a public-interest 501(c)(3) non-profit organization. In October 2023, Seth Dobbs was named as the organization's chief executive officer. In October 2025, the W3C unveiled a new logo, signaling positive changes and updated its tagline to "making the web work — for everyone". This reflects its evolution into a nonprofit organization and continued focus on global accessibility, collaboration, innovation, privacy, security and the future of web standards. Specification maturation W3C develops technical specifications for HTML5, CSS, SVG, WOFF, the Semantic Web Stack, XML, and other technologies. Sometimes, when a specification becomes too large, it is split into independent modules that can mature at their own pace. Subsequent editions of a module or specification are known as levels and are denoted by the first integer in the title (e.g. CSS3 is Level 3). Subsequent revisions on each level are denoted by an integer following a decimal point (for example, CSS2.1 is Revision 1). The W3C standard formation process is defined within the W3C process document, outlining four maturity levels through which each new standard or recommendation must progress. After enough content has been gathered from 'editor drafts' and discussion, it may be published as a working draft (WD) for review by the community. A WD document is the first form of a standard that is publicly available. Commentary by virtually anyone is accepted, though no promises are made with regard to action on any particular element commented upon. At this stage, the standard document may have significant differences from its final form. As such, anyone who implements WD standards should be ready to significantly modify their implementations as the standard matures. A candidate recommendation is a version of a more mature standard than the WD. At this point, the group responsible for the standard is satisfied that the standard meets its goal. The purpose of the CR is to elicit aid from the development community on how implementable the standard is. The standard document may change further, but significant features are mostly decided at this point. The design of those features can still change due to feedback from implementers. A proposed recommendation is the version of a standard that has passed the prior two levels. The users of the standard provide input. At this stage, the document is submitted to the W3C Advisory Council for final approval. While this step is important, it rarely causes any significant changes to a standard as it passes to the next phase. This is the most mature stage of development. At this point, the standard has undergone extensive review and testing, under both theoretical and practical conditions. The standard is now endorsed by the W3C, indicating its readiness for deployment to the public, and encouraging more widespread support among implementers and authors. Recommendations can sometimes be implemented incorrectly, partially, or not at all, but many standards define two or more levels of conformance that developers must follow if they wish to label their product as W3C-compliant. A recommendation may be updated or extended by separately-published, non-technical errata or editor drafts until sufficient substantial edits accumulate for producing a new edition or level of the recommendation. Additionally, the W3C publishes various kinds of informative notes which are to be used as references. Unlike the Internet Society and other international standards bodies, the W3C does not have a certification program. The W3C has decided, for now, that it is not suitable to start such a program, owing to the risk of creating more drawbacks for the community than benefits. Administration In January 2023, after 28 years of being jointly administered by the MIT Computer Science and Artificial Intelligence Laboratory (located in Stata Center) in the United States, the European Research Consortium for Informatics and Mathematics [fr] (ERCIM; in Sophia Antipolis, France), Keio University (in Japan) and Beihang University (in China), the W3C incorporated as a legal entity, becoming a public-interest not-for-profit organization. The W3C has a staff team of 70–80 worldwide as of 2015[update]. W3C is run by a management team which allocates resources and designs strategy. It also includes an advisory board that supports strategy and legal matters and helps resolve conflicts. The majority of standardization work is done by external experts in the W3C's various working groups. Membership The Consortium is governed by its membership. The list of members is available to the public. Members include businesses, nonprofit organizations, universities, governmental entities, and individuals. Membership requirements are transparent except for one requirement: An application for membership must be reviewed and approved by the W3C. Many guidelines and requirements are stated in detail, but there is no final guideline about the process or standards by which membership might be finally approved or denied. The cost of membership is given on a sliding scale, depending on the character of the organization applying and the country in which it is located. Countries are categorized by the World Bank's most recent grouping by gross national income per capita. Criticism In 2012 and 2013, the W3C started considering adding DRM-specific Encrypted Media Extensions (EME) to HTML5, which was criticised as being against the openness, interoperability, and vendor neutrality that distinguished websites built using only W3C standards from those requiring proprietary plug-ins like Flash. On 18 September 2017, the W3C published the EME specification as a recommendation, leading to the Electronic Frontier Foundation's resignation from W3C. As feared by the opponents of EME, as of 2020[update], none of the widely used Content Decryption Modules used with EME are available for licensing without a per-browser licensing fee. Standards W3C/Internet Engineering Task Force standards (over Internet protocol suite): The org.w3c.dom standard library packages in the Java programming language provide interfaces for the Document Object Model (DOM). The org.xml.sax standard library packages provide interfaces for the Simple API for XML (SAX). See also References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Kuwaykat] | [TOKENS: 1186] |
Contents Kuwaykat Kuwaykat (Arabic: كويكات), also spelled Kuweikat, Kweikat or Kuwaikat, was a Palestinian village located 9 km northeast of Acre. It was depopulated in 1948. History The old khan (caravansary) in Kuwaykat possibly dated to the Crusader period or an earlier date. According to historian Denys Pringle, the khan might have been part of the headquarters of Genoese estate in the village built in the 13th century. It consisted of a round barrel-vaulted building made of ashlar. In 1245 the western part of Kuwaykat was owned by the Church and Hospital of St Thomas the Martyr in Acre. In the late Ottoman period, Kuwaykat was named Chiouwe chiateh on the French map Pierre Jacotin made of the area during Napoleon's invasion of Egypt and Syria in 1799. In 1875 Victor Guérin visited, and found the village surrounded with gardens planted with fig and olive trees, and with an ancient well. He further noted that the village was mentioned in Crusader sources. In 1881 Kuwaykat was described by the PEF's Survey of Western Palestine as being built of stone and situated at the foot of hills. The roughly 300 Muslim residents cultivated olives. In 1887, an elementary school was built in the village. In addition, the village had a mosque and a shrine for the Druze religious leader, Shaykh Aby Muhammad al-Qurayshi. A population list from about 1887 showed that Kiryet et Kuweikat had about 565 inhabitants; all Muslims. In the 1922 census of Palestine conducted by the British Mandate authorities, Kuaikat had a population of 604; all Muslims, increasing in the 1931 census to 789, still all Muslims, in a total of 163 houses. In April 1938, during the Arab revolt in Palestine, a group of Palestinian Arab rebels planted a mine on the road near Kuwaykat which blew up a British vehicle, killing nine soldiers (according to the Arabs) or one soldier and wounding two others (according to the British). A rebel leader in Kuwaykat, Fayyad Baytam, was approached by the regional rebel commander Shaykh Amhad al-Tuba, who ordered him to plant the explosive on the road. Baytam refused, arguing that planting the bomb would only inevitably bring retaliation upon the village. Two local rebels, Al-Tuba and Ali Hummada, planted the explosive instead. The British Army proceeded to start setting houses in Kafr Yasif ablaze in response, but were then informed by local residents that the inhabitants of Kuwaykat were responsible for the attack. The British troops fatally shot nine Arabs as they approached the village. In the 1945 statistics, Kuwaykat had 1,050 Muslim inhabitants, with a total of 4,733 dunums (1,170 acres) of land according to an official land and population survey. The land of Kuwaykat was considered to be among the most fertile of the district. Grain, olives and watermelons were its chief crops. In 1944/45 a total of 3,316 dunums were used for cereals, and 1,246 dunums were irrigated or used for orchards, of which 500 dunums were planted with olive trees, while 26 dunams were built-up (urban) area. The villagers also engaged in livestock breeding and dairy production. The village had a population of 1,050. The first attack on the village of Kuwaykat during the 1948 Arab–Israeli War took place on 18–19 January 1948, and involved a force of over eighty Jewish militiamen, according to Filastin, the Palestinian newspaper at the time. The attack was repulsed, as was another attack on the village on the night of 6–7 February. The village was finally depopulated during a military assault by Israel's Sheva' Brigade and Carmeli Brigade, as part of Operation Dekel. On the night of 9 July, at the start of the offensive, the village came under heavy bombardment. Villagers interviewed in 1973 in the refugee camp of Bourj el-Barajneh in Lebanon recalled: We were awakened by the loudest noise we had ever heard, shells exploding and artillery fire [..] women were screaming, children were crying...Most of the villagers began to flee with their pajamas on. The wife of Qassim Ahmad Sa´id fled carrying a pillow in her arms instead of her child ... Two people were killed and two wounded by the shelling. Many villagers fled to Abu Snan, Kafr Yasif and other villages that later surrendered. Those, mostly elderly, villagers who remained in Kuwaykat, were soon expelled to Kafr Yasif. In January 1949, kibbutz ha-Bonim (later renamed Beit HaEmek) was established near the site of Kuwaykat, on village lands. Its settlers were Jewish immigrants from England, Hungary and the Netherlands. The Palestinian historian Walid Khalidi described the village in 1992: Little remains of the village except the deserted cemetery, completely overgrown with weeds, and rubble from houses. Inscriptions on two of the graves identify one as that of Hamad 'Isa al-Hajj, and another as that of Shaykh Salih Iskandar, who died in 1940. The shrine of Shaykh Abu Muhammad al-Qurayshi still stands but its stone pedestal is badly cracked. See also Footnotes Bibliography External links |
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[SOURCE: https://en.wikipedia.org/wiki/DSL] | [TOKENS: 3479] |
Contents Digital subscriber line Digital subscriber line (DSL), originally digital subscriber loop, is a family of technologies that are used to transmit digital data over telephone lines. In telecommunications marketing, the term DSL is widely understood to mean asymmetric digital subscriber line (ADSL), the most commonly installed DSL technology, for Internet access. In ADSL, the data throughput in the upstream direction (the direction to the service provider) is lower, hence the designation of asymmetric service. In symmetric digital subscriber line (SDSL) services, the downstream and upstream data rates are equal. DSL service can be delivered simultaneously with wired telephone service on the same telephone line since DSL uses higher frequency bands for data transmission. On the customer premises, a DSL filter is installed on each telephone to prevent undesirable interaction between DSL and telephone service. The bit rate of consumer ADSL services typically ranges from 256 kbit/s up to 25 Mbit/s, while the later VDSL+ technology delivers between 16 Mbit/s and 250 Mbit/s in the direction to the customer (downstream), with up to 40 Mbit/s upstream. The exact performance is depending on technology, line conditions, and service-level implementation. Researchers at Bell Labs have reached SDSL speeds over 1 Gbit/s using traditional copper telephone lines, though such speeds have not been made available to customers yet.[as of?] History Initially, it was believed that ordinary phone lines could only be used at modest speeds, usually less than 9600 bits per second. In the 1950s, ordinary twisted-pair telephone cable often carried 4 MHz television signals between studios, suggesting that such lines would allow transmitting many megabits per second. One such circuit in the United Kingdom ran some 10 miles (16 km) between the BBC studios in Newcastle-upon-Tyne and the Pontop Pike transmitting station. However, these cables had other impairments besides Gaussian noise, preventing such rates from becoming practical in the field. The 1980s saw the development of techniques for broadband communications that allowed the limit to be greatly extended. A patent was filed in 1979 for the use of existing telephone wires for both telephones and data terminals that were connected to a remote computer via a digital data carrier system. The motivation for digital subscriber line technology was the Integrated Services Digital Network (ISDN) specification proposed in 1984 by the CCITT (now ITU-T) as part of Recommendation I.120, later reused as ISDN digital subscriber line (IDSL). Employees at Bellcore (now Telcordia Technologies) developed asymmetric digital subscriber line (ADSL) by placing wide-band digital signals at frequencies above the existing baseband analog voice signal carried on conventional twisted pair cabling between telephone exchanges and customers. A patent was filed by AT&T Bell Labs on the basic DSL concept in 1988. Joseph W. Lechleider's contribution to DSL was his insight that an asymmetric arrangement offered more than double the bandwidth capacity of symmetric DSL. This allowed Internet service providers to offer efficient service to consumers, who benefited greatly from the ability to download large amounts of data but rarely needed to upload comparable amounts. ADSL supports two modes of transport: fast channel and interleaved channel. Fast channel is preferred for streaming multimedia, where an occasional dropped bit is acceptable, but lags are less so. Interleaved channel works better for file transfers, where the delivered data must be error-free but latency (time delay) incurred by the retransmission of error-containing packets is acceptable. Consumer-oriented ADSL was designed to operate on existing lines already conditioned for Basic Rate Interface ISDN services. Engineers developed high-speed DSL facilities such as high bit rate digital subscriber line (HDSL) and symmetric digital subscriber line (SDSL) to provision traditional Digital Signal 1 (DS1) services over standard copper pair facilities. Older ADSL standards delivered 8 Mbit/s to the customer over about 2 km (1.2 mi) of unshielded twisted-pair copper wire. Newer variants improved these rates. Distances greater than 2 km (1.2 mi) significantly reduce the bandwidth usable on the wires, thus reducing the data rate. But ADSL loop extenders increase these distances by repeating the signal, allowing the local exchange carrier (LEC) to deliver DSL speeds to any distance. Until the late 1990s, the cost of digital signal processors for DSL was prohibitive. All types of DSL employ highly complex digital signal processing algorithms to overcome the inherent limitations of the existing twisted pair wires. Due to the advancements of very-large-scale integration (VLSI) technology, the cost of the equipment associated with a DSL deployment lowered significantly. The two main pieces of equipment are a digital subscriber line access multiplexer (DSLAM) at one end and a DSL modem at the other end. It is possible to set up a DSL connection over an existing cable. Such deployment, even including equipment, is much cheaper than installing a new, high-bandwidth fiber-optic cable over the same route and distance. This is true both for ADSL and SDSL variations. DSL's continued use reflects advancements in electronics that have improved performance and reduced costs, despite the high expense of laying new physical infrastructure. These advantages made ADSL a better proposition for customers requiring Internet access than metered dial up, while also allowing voice calls to be received at the same time as a data connection. Telephone companies were also under pressure to move to ADSL owing to competition from cable companies, which use DOCSIS cable modem technology to achieve similar speeds. Demand for high bandwidth applications, such as video and file sharing, also contributed to the popularity of ADSL technology. Some of the first field trials for DSL were carried out in 1996. Early DSL service required a dedicated dry loop, but when the U.S. Federal Communications Commission (FCC) required incumbent local exchange carriers (ILECs) to lease their lines to competing DSL service providers, shared-line DSL became available. Also known as DSL over unbundled network element, this unbundling of services allows a single subscriber to receive two separate services from two separate providers on one cable pair. The DSL service provider's equipment is co-located in the same telephone exchange as that of the ILEC supplying the customer's pre-existing voice service. The subscriber's circuit is rewired to interface with hardware supplied by the ILEC which combines a DSL frequency and plain old telephone service (POTS) signals on a single copper pair. Since 1999, certain ISPs have been offering microfilters. These devices are installed indoors and serve the same purpose as DSL splitters, which are deployed outdoors: they divide the frequencies needed for ADSL and POTS phone calls. These filters originated out of a desire to make self-installation of DSL service possible and eliminate early outdoor DSL splitters which were installed at or near the demarcation point between the customer and the ISP. By 2012, some carriers in the United States reported that DSL remote terminals with fiber backhaul were replacing older ADSL systems. Operation Telephones are connected to the telephone exchange via a local loop, which is a physical pair of wires. The local loop was originally intended mostly for the transmission of speech, encompassing an audio frequency range of 300 to 3400 hertz (commercial bandwidth). However, as long-distance trunks were gradually converted from analog to digital operation, the idea of being able to pass data through the local loop (by using frequencies above the voiceband) took hold, ultimately leading to DSL. The local loop connecting the telephone exchange to most subscribers has the capability of carrying frequencies well beyond the 3400 Hz upper limit of POTS. Depending on the length and quality of the loop, the upper limit can be tens of megahertz. DSL takes advantage of this unused bandwidth of the local loop by creating 4312.5 Hz wide channels starting between 10 and 100 kHz, depending on how the system is configured. Allocation of channels continues to higher frequencies (up to 1.1 MHz for ADSL) until new channels are deemed unusable. Each channel is evaluated for usability in much the same way an analog modem would on a POTS connection. More usable channels equate to more available bandwidth, which is why distance and line quality are a factor (the higher frequencies used by DSL travel only short distances). The pool of usable channels is then split into two different frequency bands for upstream and downstream traffic, based on a preconfigured ratio. This segregation reduces interference. Once the channel groups have been established, the individual channels are bonded into a pair of virtual circuits, one in each direction. Like analog modems, DSL transceivers constantly monitor the quality of each channel and will add or remove them from service depending on whether they are usable. Once upstream and downstream circuits are established, a subscriber can connect to a service such as an Internet service provider or other network services, like a corporate MPLS network. The underlying technology of transport across DSL facilities uses modulation of high-frequency carrier waves, an analog signal transmission. A DSL circuit terminates at each end in a modem which modulates patterns of bits into certain high-frequency impulses for transmission to the opposing modem. Signals received from the far-end modem are demodulated to yield a corresponding bit pattern that the modem passes on, in digital form, to its interfaced equipment, such as a computer, router, switch, etc. Unlike traditional dial-up modems, which modulate bits into signals in the 300–3400 Hz audio baseband, DSL modems modulate frequencies from 4000 Hz to as high as 4 MHz. This frequency band separation enables DSL service and plain old telephone service (POTS) to coexist on the same cables, known as voice-grade cables. On the subscriber's end of the circuit, inline DSL filters are installed on each telephone to pass voice frequencies but filter the high-frequency signals that would otherwise be heard as hiss. Also, nonlinear elements in the phone could otherwise generate audible intermodulation and may impair the operation of the data modem in the absence of these low-pass filters. DSL and RADSL modulations do not use the voice-frequency band so high-pass filters are incorporated in the circuitry of DSL modems filter out voice frequencies. Because DSL operates above the 3.4 kHz voice limit, it cannot pass through a loading coil, which is an inductive coil that is designed to counteract loss caused by shunt capacitance (capacitance between the two wires of the twisted pair). Loading coils are commonly set at regular intervals in POTS lines. Voice service cannot be maintained past a certain distance without such coils. Therefore, some areas that are within range for DSL service are disqualified from eligibility because of loading coil placement. Because of this, phone companies endeavor to remove loading coils on copper loops that can operate without them. Longer lines that require them can be replaced with fiber to the neighborhood or node (FTTN). Most residential and small-office DSL implementations reserve low frequencies for POTS, so that (with suitable filters and/or splitters) the existing voice service continues to operate independently of the DSL service. Thus POTS-based communications, including fax machines and dial-up modems, can share the wires with DSL. Only one DSL modem can use the subscriber line at a time. The standard way to let multiple computers share a DSL connection uses a router that establishes a connection between the DSL modem and a local Ethernet, powerline, or Wi-Fi network on the customer's premises. The theoretical foundations of DSL, like much of communication technology, can be traced back to Claude Shannon's seminal 1948 paper, "A Mathematical Theory of Communication". Generally, higher bit rate transmissions require a wider frequency band, though the ratio of bit rate to symbol rate and thus to bandwidth are not linear due to significant innovations in digital signal processing and digital modulation methods. Naked DSL is a way of providing only DSL services over a local loop. It is useful when the customer does not need the traditional telephony voice service because voice service is received either on top of the DSL services (usually VoIP) or through another network (E.g., mobile telephony). It is also commonly called an unbundled network element (UNE) in the United States; in Australia it is known as an unconditioned local loop (ULL); in Belgium it is known as "raw copper" and in the UK it is known as Single Order GEA (SoGEA). It started making a comeback in the United States in 2004 when Qwest started offering it, closely followed by Speakeasy. As a result of AT&T's merger with SBC, and Verizon's merger with MCI, those telephone companies have an obligation to offer naked DSL to consumers. Typical setup On the customer side, a DSL modem is hooked up to a phone line. The telephone company connects the other end of the line to a DSLAM (digital subscriber line access multiplexer), which concentrates a large number of individual DSL connections into a single box. The DSLAM cannot be located too far from the customer because of attenuation between the DSLAM and the user's DSL modem. It is common for a few residential blocks to be connected to one DSLAM. The above figure is a schematic of a simple DSL connection (in blue). The right side shows a DSLAM residing in the telephone company's telephone exchange. The left side shows the customer premises equipment with an optional router. The router manages a local area network which connects PCs and other local devices. The customer may opt for a modem that contains both a router and wireless access. This option (within the dashed bubble) often simplifies the connection. At the exchange, a DSLAM terminates the DSL circuits and aggregates them, where they are handed off to other networking transports such as a PON network or Ethernet. The DSLAM terminates all connections and recovers the original digital information. In the case of ADSL, the voice component is also separated at this step, either by a filter or splitter integrated in the DSLAM or by specialized filtering equipment installed before it. Load coils in phone lines, used for extending their range in rural areas, must be removed to allow DSL to operate as they only allow frequencies of up to 4000 Hz to pass through phone cables. The customer end of the connection consists of a DSL modem. This converts data between the digital signals used by computers and the analog voltage signal of a suitable frequency range which is then applied to the phone line. In some DSL variations (for example, HDSL), the modem connects directly to the computer via a serial interface, using protocols such as Ethernet or V.35. In other cases (particularly ADSL), it is common for the customer equipment to be integrated with higher-level functionality, such as routing, firewalling, or other application-specific hardware and software. In this case, the equipment is referred to as a gateway. Most DSL technologies require the installation of appropriate DSL filters at the customer's premises to separate the DSL signal from the low-frequency voice signal. The separation can take place either at the demarcation point, or with filters installed at the telephone outlets inside the customer premises. It is possible for a DSL gateway to integrate the filter, and allow telephones to connect through the gateway. Modern DSL gateways often integrate routing and other functionality. The system boots, synchronizes the DSL connection and finally establishes the internet IP services and connection between the local network and the service provider, using protocols such as DHCP or PPPoE. Protocols and configurations Many DSL technologies implement an Asynchronous Transfer Mode (ATM) layer over the low-level bitstream layer to enable the adaptation of a number of different technologies over the same link. DSL implementations may create bridged or routed networks. In a bridged configuration, the group of subscriber computers effectively connect into a single subnetwork. The earliest implementations used DHCP to provide the IP address to the subscriber equipment, with authentication via MAC address or an assigned hostname. Later implementations often use Point-to-Point Protocol (PPP) to authenticate with a user ID and password. Transmission modulation methods Transmission methods vary by market, region, carrier, and equipment. DSL technologies DSL technologies (sometimes collectively summarized as xDSL) include: The line-length limitations from telephone exchange to subscriber impose severe limits on data transmission rates. Technologies such as VDSL provide very high-speed but short-range links. VDSL is used as a method of delivering triple play services (typically implemented in fiber to the curb network architectures). Terabit DSL, is a technology that proposes the use of the space between the dielectrics (insulators) on copper twisted pair lines in telephone cables, as waveguides for 300 GHz signals that can offer speeds of up to 1 terabit per second at distances of up to 100 meters, 100 gigabits per second for 300 meters, and 10 gigabits per second for 500 meters. The first experiment for this was carried out with copper lines that were parallel to each other, and not twisted, inside a metal pipe meant to simulate the metal armoring in large telephone cables. See also References Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/Al-Manshiyya,_Acre] | [TOKENS: 1345] |
Contents Al-Manshiyya, Acre Al-Manshiyya (Arabic: المنشية), was a Palestinian village with a Muslim orphanage and a mosque known as the mosque of Abu 'Atiyya, which is still standing. The area just north of the village was a garden planted by Sulayman Pasha, who was the ruler of Acre in the early 19th century, named Arabic: قصر بهجي, Qasr Bahjī, mansion of delight; today this is known as the shrine of Bahá'u'lláh, who was the founder of the Baháʼí Faith. History Five graves were excavated in al-Manshiyya in 1955–56; the earliest dated from the thirteenth century BC. The people of Al-Manshiyya believed that the village was established in the aftermath of the Crusades, and the original inhabitants were brought to the area from North Africa by the Mamluks to populate the area. However, the village must have disintegrated subsequently, as it is not mentioned in the 1596 census. The local shrine of Abu Atabi has a construction text dating it to 1140 AH (1727–28 CE). It is probably it Richard Pococke refers to when he passed by in 1738: "On the highest ground of it are the ruins of a very strong square tower, and near it, is a mosque, a tower, and other great buildings; the place is called Abouotidy, from a Sheik who was buried there." In 1760, it:Giovanni Mariti called the place Bahattbe: "situated on a small eminence, which contains the ruins of an ancient temple, employed as a place of worship both by the Turks and Christians, but at different periods. Some paces further is a mosque, remarkable on account of its burying-ground, in which was interred a prodigious number of infidels, who perished under the walls of Acre." A map from 1799 showed the place as an "uninhabited ruin", while Guérin, who visited in 1875, observed that the village is "newly founded". In 1881, the PEF's Survey of Western Palestine (SWP) described the village of Al-Manshiyya as being situated on a plain, surrounded by arable land, with houses built of stone and adobe. It had a population of about 150. A population list from about 1887 showed that Kiryet el Menshiyeh had about 400 inhabitants, all Muslim. In the 1922 census of Palestine conducted by the British Mandate authorities Al Manshiyeh had a population of 371; all Muslims, increasing in the 1931 census to 460, still all Muslims, in a total of 132 houses. In the 1945 statistics, Al-Manshiyya had 810 Muslim inhabitants and 270 Jewish inhabitants, with a total of 14,886 dunums (3,678 acres) of land according to an official land and population survey. The economy of the village was based on agriculture. In 1944/45 253 dunams was used for citrus and bananas, 10,818 dunams were allotted to cereals, 619 dunams were irrigated or used for orchards, while 27 dunams were built-up (urban) land. The villagers, who were farmers, lived peacefully and had significant interaction with their Jewish neighbors. But the fighting in Acre, and later, the Deir Yassin massacre, frightened them. The village was first drawn into the 1948 Arab–Israeli War on 6 February 1948. On that day a number of armed Jews, using automatic weapons and Sten guns, attacked the village. They were driven back by village defenders. Manshiyya was captured by on 14 May 1948 during Operation Ben-Ami. One villager recalled that the dawn attack came from the hill overlooking the village. The villagers, "with bullets whizzing over their heads", ran towards the east "because all other sides were surrounded by the Jews". When they returned to remove the dead bodies, they found the village strewn with mines. One former villager recounted that her father returned to Al-Manshiyya about 10 days after the attack and found it had been razed. On 16 June 1948, David Ben-Gurion mentioned Manshiyya as one of the villages Israel had destroyed. Following the war the area was incorporated into the State of Israel. Two new villages, Shomrat and Bustan HaGalil, were established in 1948 on village land, north of the village site. The site is now part of the city of Acre. According to the Palestinian historian Walid Khalidi, the remaining structures on the village land were in 1992: "The Baha'i [sic] shrine, the mosque, the Islamic school for orphans, and a few houses still stand; the rest of the village is gone. The shrine is a handsome, domed structure, the front wall and arched entrance of which are framed by prominent stone pillars. The mosque, a stone structure with a dome and vaulted ceilings, has been turned into a private home for a Jewish family. The former Islamic school for orphans is also inhabited. The cemetery is still visible but is not tended; it contains a tombstone that is inscribed in Turkish and dates to the eighteenth century. The al-Basha water canal, built with stone blocks, still exists, but is not functioning; the same is also true of an aqueduct." Andrew Petersen, an archaeologist specializing in Islamic architecture, visited Al-Manshiyya in 1994. He found the mosque and shrine of Abu Atabi was still standing, though it has been turned into a residential complex since 1948. The prayer room functioned as a living room. An inscription in two parts was set above the doorway leading to the domed chamber containing the tomb. The date 1140 H (1727–28 C.E.) was still visible in the upper part, while the lower part, written in larger ornamental script might be earlier, possibly dating to Mamluk times. Abu Atabi is said locally to be a Muslim warrior from the time of the Crusades, killed during the siege of Acre. References Bibliography External links |
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[SOURCE: https://dev.to/sylwia-lask] | [TOKENS: 1047] |
DEV Community Sylwia Laskowska Software dev • 10+ yrs of code & caffeine ☕ • Sci-fi fan • Bug whisperer 🐞 For the top weekly post in the #a11y tag Awarded to the top CSS author each week You're a dedicated community champion! Keep up the great work by posting at least 2 comments per week for 16 straight weeks. The prized 24-week badge is within reach! Awarded to the top Node author each week Awarded for having a post featured in the weekly "must-reads" list. 🙌 Awarded to the top Rust author each week Consistency pays off! Be an active part of our community by posting at least 2 comments per week for 8 straight weeks. Earn the 16 Week Badge next. Awarded to the top git author each week Awarded for sharing the top weekly post under the #discuss tag. Awarded to the top JavaScript author each week Keep contributing to discussions by posting at least 2 comments per week for 4 straight weeks. Unlock the 8 Week Badge next. Keep the community conversation going! Post at least 2 comments for 2 straight weeks and unlock the 4 Week Badge. For actively engaging with the community by posting at least 2 comments in a single week. Awarded for writing and sharing your first DEV post! Continue sharing your work to earn the 4 Week Writing Streak Badge. Why WebGPU Feels Like the Future of the Web (Live Demo 🚀) Will WebAssembly Kill JavaScript? Let’s Find Out (+ Live Demo) 🚀 Nobody Writes Clean Code. We All Just Pretend I Put an LLM in My Browser and Now It Writes My Commit Messages. The Results Were… Unexpected😭✨ jQuery Will Outlive Half of Today’s JavaScript Frameworks - Here's Why If You See These Red Flags in an IT Interview — Run (Real Stories) Create an account to connect with Sylwia Laskowska. You can also sign in below to proceed if you already have an account. How Seriously Should We Take State of JS and Other Developer Surveys? Stop Installing Libraries: 10 Browser APIs That Already Solve Your Problems Is Learning CSS a Waste of Time in 2026? Why NaN !== NaN Makes Perfect Sense (I Promise) Your GitHub Contribution Graph Means Absolutely Nothing - And Here’s Why When React Starts Acting Like jQuery (and You Can Totally Tell 😅) Yes, true + true === 2. And No, JavaScript Isn’t Broken “Why Do You Code?” - A Surprisingly Hard Question 7 Lies Developers Keep Telling Themselves (And Somehow Still Believe) ❄️A Five-Minute UI Feature That Became an XSS Time Bomb If You Think YOUR Commit Messages Are Bad, Just Wait… 5 Myths About Legacy Code You Should Stop Believing The Biggest Lie in Tech? ‘We Don’t Have Time to Refactor’ The Real Reason Developers Hate Meetings (It’s Not Time) 🧠💥 Beginner’s Guide #6: 🌀 The Event Loop Explained in 3 Minutes (You’ll Never Forget It) 🎃 10 Scary Lines of Code I Wish I Never Wrote 💀 Auth Explained (Part 2): How your browser ‘remembers’ you? PKCE + refresh cookies explained like you're five 🔥 10 Mistakes Senior Developers Still Make (Are You Making Them Too?) Beginner’s Guide #5: Mutable vs Immutable in JS — The Silent Bug Factory Nobody Warns You About 😳 Auth Explained (Part 1): ID vs Access vs Refresh tokens — 🤔what they ACTUALLY do (and why localStorage is a trap) Signs you’ve been coding for too long (and maybe need a nap 😅) Beginner’s Guide #4: How to Copy an Object in JS - Explained Like You’re Five 👶 🧠 AI Buzzword Survival Guide — How to Sound Like an Expert (Even If You’re Just Curious) 🧭Beginner’s (and Not-So-Beginner’s) Guide #3 — const vs let (and a bit about var): What Developers Keep Getting Wrong I Used to Leave 50 Comments in Every Code Review. Here’s Why I Stopped Beginner’s Guide #2: When to Use forEach, map, for...of, and entries() — Explained Like You’re Five Beginner’s Guide #1: if (data) vs if (!!data) in JavaScript 🤔 Business value > Shiny tech 💎 DEV Diamond Sponsors Thank you to our Diamond Sponsors for supporting the DEV Community Google AI is the official AI Model and Platform Partner of DEV Neon is the official database partner of DEV Algolia is the official search partner of DEV DEV Community — A space to discuss and keep up software development and manage your software career Built on Forem — the open source software that powers DEV and other inclusive communities. Made with love and Ruby on Rails. DEV Community © 2016 - 2026. We're a place where coders share, stay up-to-date and grow their careers. |
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[SOURCE: https://en.wikipedia.org/wiki/Meta_Platforms#cite_note-180] | [TOKENS: 8626] |
Contents Meta Platforms Meta Platforms, Inc. (doing business as Meta) is an American multinational technology company headquartered in Menlo Park, California. Meta owns and operates several prominent social media platforms and communication services, including Facebook, Instagram, WhatsApp, Messenger, Threads and Manus. The company also operates an advertising network for its own sites and third parties; as of 2023[update], advertising accounted for 97.8 percent of its total revenue. Meta has been described as a part of Big Tech, which refers to the largest six tech companies in the United States, Alphabet (Google), Amazon, Apple, Meta (Facebook), Microsoft, and Nvidia, which are also the largest companies in the world by market capitalization. The company was originally established in 2004 as TheFacebook, Inc., and was renamed Facebook, Inc. in 2005. In 2021, it rebranded as Meta Platforms, Inc. to reflect a strategic shift toward developing the metaverse—an interconnected digital ecosystem spanning virtual and augmented reality technologies. In 2023, Meta was ranked 31st on the Forbes Global 2000 list of the world's largest public companies. As of 2022, it was the world's third-largest spender on research and development, with R&D expenses totaling US$35.3 billion. History Facebook filed for an initial public offering (IPO) on January 1, 2012. The preliminary prospectus stated that the company sought to raise $5 billion, had 845 million monthly active users, and a website accruing 2.7 billion likes and comments daily. After the IPO, Zuckerberg would retain 22% of the total shares and 57% of the total voting power in Facebook. Underwriters valued the shares at $38 each, valuing the company at $104 billion, the largest valuation yet for a newly public company. On May 16, one day before the IPO, Facebook announced it would sell 25% more shares than originally planned due to high demand. The IPO raised $16 billion, making it the third-largest in US history (slightly ahead of AT&T Mobility and behind only General Motors and Visa). The stock price left the company with a higher market capitalization than all but a few U.S. corporations—surpassing heavyweights such as Amazon, McDonald's, Disney, and Kraft Foods—and made Zuckerberg's stock worth $19 billion. The New York Times stated that the offering overcame questions about Facebook's difficulties in attracting advertisers to transform the company into a "must-own stock". Jimmy Lee of JPMorgan Chase described it as "the next great blue-chip". Writers at TechCrunch, on the other hand, expressed skepticism, stating, "That's a big multiple to live up to, and Facebook will likely need to add bold new revenue streams to justify the mammoth valuation." Trading in the stock, which began on May 18, was delayed that day due to technical problems with the Nasdaq exchange. The stock struggled to stay above the IPO price for most of the day, forcing underwriters to buy back shares to support the price. At the closing bell, shares were valued at $38.23, only $0.23 above the IPO price and down $3.82 from the opening bell value. The opening was widely described by the financial press as a disappointment. The stock set a new record for trading volume of an IPO. On May 25, 2012, the stock ended its first full week of trading at $31.91, a 16.5% decline. On May 22, 2012, regulators from Wall Street's Financial Industry Regulatory Authority announced that they had begun to investigate whether banks underwriting Facebook had improperly shared information only with select clients rather than the general public. Massachusetts Secretary of State William F. Galvin subpoenaed Morgan Stanley over the same issue. The allegations sparked "fury" among some investors and led to the immediate filing of several lawsuits, one of them a class action suit claiming more than $2.5 billion in losses due to the IPO. Bloomberg estimated that retail investors may have lost approximately $630 million on Facebook stock since its debut. S&P Global Ratings added Facebook to its S&P 500 index on December 21, 2013. On May 2, 2014, Zuckerberg announced that the company would be changing its internal motto from "Move fast and break things" to "Move fast with stable infrastructure". The earlier motto had been described as Zuckerberg's "prime directive to his developers and team" in a 2009 interview in Business Insider, in which he also said, "Unless you are breaking stuff, you are not moving fast enough." In November 2016, Facebook announced the Microsoft Windows client of gaming service Facebook Gameroom, formerly Facebook Games Arcade, at the Unity Technologies developers conference. The client allows Facebook users to play "native" games in addition to its web games. The service was closed in June 2021. Lasso was a short-video sharing app from Facebook similar to TikTok that was launched on iOS and Android in 2018 and was aimed at teenagers. On July 2, 2020, Facebook announced that Lasso would be shutting down on July 10. In 2018, the Oculus lead Jason Rubin sent his 50-page vision document titled "The Metaverse" to Facebook's leadership. In the document, Rubin acknowledged that Facebook's virtual reality business had not caught on as expected, despite the hundreds of millions of dollars spent on content for early adopters. He also urged the company to execute fast and invest heavily in the vision, to shut out HTC, Apple, Google and other competitors in the VR space. Regarding other players' participation in the metaverse vision, he called for the company to build the "metaverse" to prevent their competitors from "being in the VR business in a meaningful way at all". In May 2019, Facebook founded Libra Networks, reportedly to develop their own stablecoin cryptocurrency. Later, it was reported that Libra was being supported by financial companies such as Visa, Mastercard, PayPal and Uber. The consortium of companies was expected to pool in $10 million each to fund the launch of the cryptocurrency coin named Libra. Depending on when it would receive approval from the Swiss Financial Market Supervisory authority to operate as a payments service, the Libra Association had planned to launch a limited format cryptocurrency in 2021. Libra was renamed Diem, before being shut down and sold in January 2022 after backlash from Swiss government regulators and the public. During the COVID-19 pandemic, the use of online services, including Facebook, grew globally. Zuckerberg predicted this would be a "permanent acceleration" that would continue after the pandemic. Facebook hired aggressively, growing from 48,268 employees in March 2020 to more than 87,000 by September 2022. Following a period of intense scrutiny and damaging whistleblower leaks, news started to emerge on October 21, 2021 about Facebook's plan to rebrand the company and change its name. In the Q3 2021 earnings call on October 25, Mark Zuckerberg discussed the ongoing criticism of the company's social services and the way it operates, and pointed to the pivoting efforts to building the metaverse – without mentioning the rebranding and the name change. The metaverse vision and the name change from Facebook, Inc. to Meta Platforms was introduced at Facebook Connect on October 28, 2021. Based on Facebook's PR campaign, the name change reflects the company's shifting long term focus of building the metaverse, a digital extension of the physical world by social media, virtual reality and augmented reality features. "Meta" had been registered as a trademark in the United States in 2018 (after an initial filing in 2015) for marketing, advertising, and computer services, by a Canadian company that provided big data analysis of scientific literature. This company was acquired in 2017 by the Chan Zuckerberg Initiative (CZI), a foundation established by Zuckerberg and his wife, Priscilla Chan, and became one of their projects. Following the rebranding announcement, CZI announced that it had already decided to deprioritize the earlier Meta project, thus it would be transferring its rights to the name to Meta Platforms, and the previous project would end in 2022. Soon after the rebranding, in early February 2022, Meta reported a greater-than-expected decline in profits in the fourth quarter of 2021. It reported no growth in monthly users, and indicated it expected revenue growth to stall. It also expected measures taken by Apple Inc. to protect user privacy to cost it some $10 billion in advertisement revenue, an amount equal to roughly 8% of its revenue for 2021. In meeting with Meta staff the day after earnings were reported, Zuckerberg blamed competition for user attention, particularly from video-based apps such as TikTok. The 27% reduction in the company's share price which occurred in reaction to the news eliminated some $230 billion of value from Meta's market capitalization. Bloomberg described the decline as "an epic rout that, in its sheer scale, is unlike anything Wall Street or Silicon Valley has ever seen". Zuckerberg's net worth fell by as much as $31 billion. Zuckerberg owns 13% of Meta, and the holding makes up the bulk of his wealth. According to published reports by Bloomberg on March 30, 2022, Meta turned over data such as phone numbers, physical addresses, and IP addresses to hackers posing as law enforcement officials using forged documents. The law enforcement requests sometimes included forged signatures of real or fictional officials. When asked about the allegations, a Meta representative said, "We review every data request for legal sufficiency and use advanced systems and processes to validate law enforcement requests and detect abuse." In June 2022, Sheryl Sandberg, the chief operating officer of 14 years, announced she would step down that year. Zuckerberg said that Javier Olivan would replace Sandberg, though in a “more traditional” role. In March 2022, Meta (except Meta-owned WhatsApp) and Instagram were banned in Russia and added to the Russian list of terrorist and extremist organizations for alleged Russophobia and hate speech (up to genocidal calls) amid the ongoing Russian invasion of Ukraine. Meta appealed against the ban, but it was upheld by a Moscow court in June of the same year. Also in March 2022, Meta and Italian eyewear giant Luxottica released Ray-Ban Stories, a series of smartglasses which could play music and take pictures. Meta and Luxottica parent company EssilorLuxottica declined to disclose sales on the line of products as of September 2022, though Meta has expressed satisfaction with its customer feedback. In July 2022, Meta saw its first year-on-year revenue decline when its total revenue slipped by 1% to $28.8bn. Analysts and journalists accredited the loss to its advertising business, which has been limited by Apple's app tracking transparency feature and the number of people who have opted not to be tracked by Meta apps. Zuckerberg also accredited the decline to increasing competition from TikTok. On October 27, 2022, Meta's market value dropped to $268 billion, a loss of around $700 billion compared to 2021, and its shares fell by 24%. It lost its spot among the top 20 US companies by market cap, despite reaching the top 5 in the previous year. In November 2022, Meta laid off 11,000 employees, 13% of its workforce. Zuckerberg said the decision to aggressively increase Meta's investments had been a mistake, as he had wrongly predicted that the surge in e-commerce would last beyond the COVID-19 pandemic. He also attributed the decline to increased competition, a global economic downturn and "ads signal loss". Plans to lay off a further 10,000 employees began in April 2023. The layoffs were part of a general downturn in the technology industry, alongside layoffs by companies including Google, Amazon, Tesla, Snap, Twitter and Lyft. Starting from 2022, Meta scrambled to catch up to other tech companies in adopting specialized artificial intelligence hardware and software. It had been using less expensive CPUs instead of GPUs for AI work, but that approach turned out to be less efficient. The company gifted the Inter-university Consortium for Political and Social Research $1.3 million to finance the Social Media Archive's aim to make their data available to social science research. In 2023, Ireland's Data Protection Commissioner imposed a record EUR 1.2 billion fine on Meta for transferring data from Europe to the United States without adequate protections for EU citizens.: 250 In March 2023, Meta announced a new round of layoffs that would cut 10,000 employees and close 5,000 open positions to make the company more efficient. Meta revenue surpassed analyst expectations for the first quarter of 2023 after announcing that it was increasing its focus on AI. On July 6, Meta launched a new app, Threads, a competitor to Twitter. Meta announced its artificial intelligence model Llama 2 in July 2023, available for commercial use via partnerships with major cloud providers like Microsoft. It was the first project to be unveiled out of Meta's generative AI group after it was set up in February. It would not charge access or usage but instead operate with an open-source model to allow Meta to ascertain what improvements need to be made. Prior to this announcement, Meta said it had no plans to release Llama 2 for commercial use. An earlier version of Llama was released to academics. In August 2023, Meta announced its permanent removal of news content from Facebook and Instagram in Canada due to the Online News Act, which requires Canadian news outlets to be compensated for content shared on its platform. The Online News Act was in effect by year-end, but Meta will not participate in the regulatory process. In October 2023, Zuckerberg said that AI would be Meta's biggest investment area in 2024. Meta finished 2023 as one of the best-performing technology stocks of the year, with its share price up 150 percent. Its stock reached an all-time high in January 2024, bringing Meta within 2% of achieving $1 trillion market capitalization. In November 2023 Meta Platforms launched an ad-free service in Europe, allowing subscribers to opt-out of personal data being collected for targeted advertising. A group of 28 European organizations, including Max Schrems' advocacy group NOYB, the Irish Council for Civil Liberties, Wikimedia Europe, and the Electronic Privacy Information Center, signed a 2024 letter to the European Data Protection Board (EDPB) expressing concern that this subscriber model would undermine privacy protections, specifically GDPR data protection standards. Meta removed the Facebook and Instagram accounts of Iran's Supreme Leader Ali Khamenei in February 2024, citing repeated violations of its Dangerous Organizations & Individuals policy. As of March, Meta was under investigation by the FDA for alleged use of their social media platforms to sell illegal drugs. On 16 May 2024, the European Commission began an investigation into Meta over concerns related to child safety. In May 2023, Iraqi social media influencer Esaa Ahmed-Adnan encountered a troubling issue when Instagram removed his posts, citing false copyright violations despite his content being original and free from copyrighted material. He discovered that extortionists were behind these takedowns, offering to restore his content for $3,000 or provide ongoing protection for $1,000 per month. This scam, exploiting Meta’s rights management tools, became widespread in the Middle East, revealing a gap in Meta’s enforcement in developing regions. An Iraqi nonprofit Tech4Peace’s founder, Aws al-Saadi helped Ahmed-Adnan and others, but the restoration process was slow, leading to significant financial losses for many victims, including prominent figures like Ammar al-Hakim. This situation highlighted Meta’s challenges in balancing global growth with effective content moderation and protection. On 16 September 2024, Meta announced it had banned Russian state media outlets from its platforms worldwide due to concerns about "foreign interference activity." This decision followed allegations that RT and its employees funneled $10 million through shell companies to secretly fund influence campaigns on various social media channels. Meta's actions were part of a broader effort to counter Russian covert influence operations, which had intensified since the invasion. At its 2024 Connect conference, Meta presented Orion, its first pair of augmented reality glasses. Though Orion was originally intended to be sold to consumers, the manufacturing process turned out to be too complex and expensive. Instead, the company pivoted to producing a small number of the glasses to be used internally. On 4 October 2024, Meta announced about its new AI model called Movie Gen, capable of generating realistic video and audio clips based on user prompts. Meta stated it would not release Movie Gen for open development, preferring to collaborate directly with content creators and integrate it into its products by the following year. The model was built using a combination of licensed and publicly available datasets. On October 31, 2024, ProPublica published an investigation into deceptive political advertisement scams that sometimes use hundreds of hijacked profiles and facebook pages run by organized networks of scammers. The authors cited spotty enforcement by Meta as a major reason for the extent of the issue. In November 2024, TechCrunch reported that Meta were considering building a $10bn global underwater cable spanning 25,000 miles. In the same month, Meta closed down 2 million accounts on Facebook and Instagram that were linked to scam centers in Myanmar, Laos, Cambodia, the Philippines, and the United Arab Emirates doing pig butchering scams. In December 2024, Meta announced that, beginning February 2025, they would require advertisers to run ads about financial services in Australia to verify information about who are the beneficiary and the payer in a bid to regulate scams. On December 4, 2024, Meta announced it will invest US$10 billion for its largest AI data center in northeast Louisiana, powered by natural gas facilities. On the 11th of that month, Meta experienced a global outage, impacting accounts on all of their social media and messaging applications. Outage reports from DownDetector reached 70,000+ and 100,000+ within minutes for Instagram and Facebook, respectively. In January 2025, Meta announced plans to roll back its diversity, equity, and inclusion (DEI) initiatives, citing shifts in the "legal and policy landscape" in the United States following the 2024 presidential election. The decision followed reports that CEO Mark Zuckerberg sought to align the company more closely with the incoming Trump administration, including changes to content moderation policies and executive leadership. The new content moderation policies continued to bar insults about a person's intellect or mental illness, but made an exception to allow calling LGBTQ people mentally ill because they are gay or transgender. Later that month, Meta agreed to pay $25 million to settle a 2021 lawsuit brought by Donald Trump for suspending his social media accounts after the January 6 riots. Changes to Meta's moderation policies were controversial among its oversight board, with a significant divide in opinion between the board's US conservatives and its global members. In June 2025, Meta Platforms Inc. has decided to make a multibillion-dollar investment into artificial intelligence startup Scale AI. The financing could exceed $10 billion in value which would make it one of the largest private company funding events of all time. In October 2025, it was announced that Meta would be laying off 600 employees in the artificial intelligence unit to perform better and simpler. They referred to their AI unit as "bloated" and are seeking to trim down the department. This mass layoff is going to impact Meta’s AI infrastructure units, Fundamental Artificial Intelligence Research unit (FAIR) and other product-related positions. Mergers and acquisitions Meta has acquired multiple companies (often identified as talent acquisitions). One of its first major acquisitions was in April 2012, when it acquired Instagram for approximately US$1 billion in cash and stock. In October 2013, Facebook, Inc. acquired Onavo, an Israeli mobile web analytics company. In February 2014, Facebook, Inc. announced it would buy mobile messaging company WhatsApp for US$19 billion in cash and stock. The acquisition was completed on October 6. Later that year, Facebook bought Oculus VR for $2.3 billion in cash and stock, which released its first consumer virtual reality headset in 2016. In late November 2019, Facebook, Inc. announced the acquisition of the game developer Beat Games, responsible for developing one of that year's most popular VR games, Beat Saber. In Late 2022, after Facebook Inc rebranded to Meta Platforms Inc, Oculus was rebranded to Meta Quest. In May 2020, Facebook, Inc. announced it had acquired Giphy for a reported cash price of $400 million. It will be integrated with the Instagram team. However, in August 2021, UK's Competition and Markets Authority (CMA) stated that Facebook, Inc. might have to sell Giphy, after an investigation found that the deal between the two companies would harm competition in display advertising market. Facebook, Inc. was fined $70 million by CMA for deliberately failing to report all information regarding the acquisition and the ongoing antitrust investigation. In October 2022, the CMA ruled for a second time that Meta be required to divest Giphy, stating that Meta already controls half of the advertising in the UK. Meta agreed to the sale, though it stated that it disagrees with the decision itself. In May 2023, Giphy was divested to Shutterstock for $53 million. In November 2020, Facebook, Inc. announced that it planned to purchase the customer-service platform and chatbot specialist startup Kustomer to promote companies to use their platform for business. It has been reported that Kustomer valued at slightly over $1 billion. The deal was closed in February 2022 after regulatory approval. In September 2022, Meta acquired Lofelt, a Berlin-based haptic tech startup. In December 2025, it was announced Meta had acquired the AI-wearables startup, Limitless. In the same month, they also acquired another AI startup, Manus AI, for $2 billion. Manus announced in December that its platform had achieved $100mm in recurring revenue just 8 months after its launch and Meta said it will scale the platform to many other businesses. In January 2026, it was announced Meta proposed acquisition of Manus was undergoing preliminary scrutiny by Chinese regulators. The examination concerns the cross-border transfer of artificial intelligence technology developed in China. Lobbying In 2020, Facebook, Inc. spent $19.7 million on lobbying, hiring 79 lobbyists. In 2019, it had spent $16.7 million on lobbying and had a team of 71 lobbyists, up from $12.6 million and 51 lobbyists in 2018. Facebook was the largest spender of lobbying money among the Big Tech companies in 2020. The lobbying team includes top congressional aide John Branscome, who was hired in September 2021, to help the company fend off threats from Democratic lawmakers and the Biden administration. In December 2024, Meta donated $1 million to the inauguration fund for then-President-elect Donald Trump. In 2025, Meta was listed among the donors funding the construction of the White House State Ballroom. Partnerships February 2026, Meta announced a long-term partnership with Nvidia. Censorship In August 2024, Mark Zuckerberg sent a letter to Jim Jordan indicating that during the COVID-19 pandemic the Biden administration repeatedly asked Meta to limit certain COVID-19 content, including humor and satire, on Facebook and Instagram. In 2016 Meta hired Jordana Cutler, formerly an employee at the Israeli Embassy to the United States, as its policy chief for Israel and the Jewish Diaspora. In this role, Cutler pushed for the censorship of accounts belonging to Students for Justice in Palestine chapters in the United States. Critics have said that Cutler's position gives the Israeli government an undue influence over Meta policy, and that few countries have such high levels of contact with Meta policymakers. Following the election of Donald Trump in 2025, various sources noted possible censorship related to the Democratic Party on Instagram and other Meta platforms. In February 2025, a Meta rep flagged journalist Gil Duran's article and other "critiques of tech industry figures" as spam or sensitive content, limiting their reach. In March 2025, Meta attempted to block former employee Sarah Wynn-Williams from promoting or further distributing her memoir, Careless People, that includes allegations of unaddressed sexual harassment in the workplace by senior executives. The New York Times reports that the arbitration is among Meta's most forcible attempts to repudiate a former employee's account of workplace dynamics. Publisher Macmillan reacted to the ruling by the Emergency International Arbitral Tribunal by stating that it will ignore its provisions. As of 15 March 2025[update], hardback and digital versions of Careless People were being offered for sale by major online retailers. From October 2025, Meta began removing and restricting access for accounts related to LGBTQ, reproductive health and abortion information pages on its platforms. Martha Dimitratou, executive director of Repro Uncensored, called Meta's shadow-banning of these issues "One of the biggest waves of censorship we are seeing". Disinformation concerns Since its inception, Meta has been accused of being a host for fake news and misinformation. In the wake of the 2016 United States presidential election, Zuckerberg began to take steps to eliminate the prevalence of fake news, as the platform had been criticized for its potential influence on the outcome of the election. The company initially partnered with ABC News, the Associated Press, FactCheck.org, Snopes and PolitiFact for its fact-checking initiative; as of 2018, it had over 40 fact-checking partners across the world, including The Weekly Standard. A May 2017 review by The Guardian found that the platform's fact-checking initiatives of partnering with third-party fact-checkers and publicly flagging fake news were regularly ineffective, and appeared to be having minimal impact in some cases. In 2018, journalists working as fact-checkers for the company criticized the partnership, stating that it had produced minimal results and that the company had ignored their concerns. In 2024 Meta's decision to continue to disseminate a falsified video of US president Joe Biden, even after it had been proven to be fake, attracted criticism and concern. In January 2025, Meta ended its use of third-party fact-checkers in favor of a user-run community notes system similar to the one used on X. While Zuckerberg supported these changes, saying that the amount of censorship on the platform was excessive, the decision received criticism by fact-checking institutions, stating that the changes would make it more difficult for users to identify misinformation. Meta also faced criticism for weakening its policies on hate speech that were designed to protect minorities and LGBTQ+ individuals from bullying and discrimination. While moving its content review teams from California to Texas, Meta changed their hateful conduct policy to eliminate restrictions on anti-LGBT and anti-immigrant hate speech, as well as explicitly allowing users to accuse LGBT people of being mentally ill or abnormal based on their sexual orientation or gender identity. In January 2025, Meta faced significant criticism for its role in removing LGBTQ+ content from its platforms, amid its broader efforts to address anti-LGBTQ+ hate speech. The removal of LGBTQ+ themes was noted as part of the wider crackdown on content deemed to violate its community guidelines. Meta's content moderation policies, which were designed to combat harmful speech and protect users from discrimination, inadvertently led to the removal or restriction of LGBTQ+ content, particularly posts highlighting LGBTQ+ identities, support, or political issues. According to reports, LGBTQ+ posts, including those that simply celebrated pride or advocated for LGBTQ+ rights, were flagged and removed for reasons that some critics argue were vague or inconsistently applied. Many LGBTQ+ activists and users on Meta's platforms expressed concern that such actions stifled visibility and expression, potentially isolating LGBTQ+ individuals and communities, especially in spaces that were historically important for outreach and support. Lawsuits Numerous lawsuits have been filed against the company, both when it was known as Facebook, Inc., and as Meta Platforms. In March 2020, the Office of the Australian Information Commissioner (OAIC) sued Facebook, for significant and persistent infringements of the rule on privacy involving the Cambridge Analytica fiasco. Every violation of the Privacy Act is subject to a theoretical cumulative liability of $1.7 million. The OAIC estimated that a total of 311,127 Australians had been exposed. On December 8, 2020, the U.S. Federal Trade Commission and 46 states (excluding Alabama, Georgia, South Carolina, and South Dakota), the District of Columbia and the territory of Guam, launched Federal Trade Commission v. Facebook as an antitrust lawsuit against Facebook. The lawsuit concerns Facebook's acquisition of two competitors—Instagram and WhatsApp—and the ensuing monopolistic situation. FTC alleges that Facebook holds monopolistic power in the U.S. social networking market and seeks to force the company to divest from Instagram and WhatsApp to break up the conglomerate. William Kovacic, a former chairman of the Federal Trade Commission, argued the case will be difficult to win as it would require the government to create a counterfactual argument of an internet where the Facebook-WhatsApp-Instagram entity did not exist, and prove that harmed competition or consumers. In November 2025, it was ruled that Meta did not violate antitrust laws and holds no monopoly in the market. On December 24, 2021, a court in Russia fined Meta for $27 million after the company declined to remove unspecified banned content. The fine was reportedly tied to the company's annual revenue in the country. In May 2022, a lawsuit was filed in Kenya against Meta and its local outsourcing company Sama. Allegedly, Meta has poor working conditions in Kenya for workers moderating Facebook posts. According to the lawsuit, 260 screeners were declared redundant with confusing reasoning. The lawsuit seeks financial compensation and an order that outsourced moderators be given the same health benefits and pay scale as Meta employees. In June 2022, 8 lawsuits were filed across the U.S. over the allege that excessive exposure to platforms including Facebook and Instagram has led to attempted or actual suicides, eating disorders and sleeplessness, among other issues. The litigation follows a former Facebook employee's testimony in Congress that the company refused to take responsibility. The company noted that tools have been developed for parents to keep track of their children's activity on Instagram and set time limits, in addition to Meta's "Take a break" reminders. In addition, the company is providing resources specific to eating disorders as well as developing AI to prevent children under the age of 13 signing up for Facebook or Instagram. In June 2022, Meta settled a lawsuit with the US Department of Justice. The lawsuit, which was filed in 2019, alleged that the company enabled housing discrimination through targeted advertising, as it allowed homeowners and landlords to run housing ads excluding people based on sex, race, religion, and other characteristics. The U.S. Department of Justice stated that this was in violation of the Fair Housing Act. Meta was handed a penalty of $115,054 and given until December 31, 2022, to shadow the algorithm tool. In January 2023, Meta was fined €390 million for violations of the European Union General Data Protection Regulation. In May 2023, the European Data Protection Board fined Meta a record €1.2 billion for breaching European Union data privacy laws by transferring personal data of Facebook users to servers in the U.S. In July 2024, Meta agreed to pay the state of Texas US$1.4 billion to settle a lawsuit brought by Texas Attorney General Ken Paxton accusing the company of collecting users' biometric data without consent, setting a record for the largest privacy-related settlement ever obtained by a state attorney general. In October 2024, Meta Platforms faced lawsuits in Japan from 30 plaintiffs who claimed they were defrauded by fake investment ads on Facebook and Instagram, featuring false celebrity endorsements. The plaintiffs are seeking approximately $2.8 million in damages. In April 2025, the Kenyan High Court ruled that a US$2.4 billion lawsuit in which three plaintiffs claim that Facebook inflamed civil violence in Ethiopia in 2021 could proceed. In April 2025, Meta was fined €200 million ($230 million) for breaking the Digital Markets Act, by imposing a “consent or pay” system that forces users to either allow their personal data to be used to target advertisements, or pay a subscription fee for advertising-free versions of Facebook and Instagram. In late April 2025, a case was filed against Meta in Ghana over the alleged psychological distress experienced by content moderators employed to take down disturbing social media content including depictions of murders, extreme violence and child sexual abuse. Meta moved the moderation service to the Ghanaian capital of Accra after legal issues in the previous location Kenya. The new moderation company is Teleperformance, a multinational corporation with a history of worker's rights violation. Reports suggests the conditions are worse here than in the previous Kenyan location, with many workers afraid of speaking out due to fear of returning to conflict zones. Workers reported developing mental illnesses, attempted suicides, and low pay. In 26 January 2026, a New Mexico state court case was filed, suggesting that Mark Zuckerberg approved allowing minors to access artificial intelligence chatbot companions that safety staffers warned were capable of sexual interactions. In 2020, the company UReputation, which had been involved in several cases concerning the management of digital armies[clarification needed], filed a lawsuit against Facebook, accusing it of unlawfully transmitting personal data to third parties. Legal actions were initiated in Tunisia, France, and the United States. In 2025, the United States District court for the Northern District of Georgia approved a discovery procedure, allowing UReputation to access documents and evidence held by Meta. Structure Meta's key management consists of: As of October 2022[update], Meta had 83,553 employees worldwide. As of June 2024[update], Meta's board consisted of the following directors; Meta Platforms is mainly owned by institutional investors, who hold around 80% of all shares. Insiders control the majority of voting shares. The three largest individual investors in 2024 were Mark Zuckerberg, Sheryl Sandberg and Christopher K. Cox. The largest shareholders in late 2024/early 2025 were: Roger McNamee, an early Facebook investor and Zuckerberg's former mentor, said Facebook had "the most centralized decision-making structure I have ever encountered in a large company". Facebook co-founder Chris Hughes has stated that chief executive officer Mark Zuckerberg has too much power, that the company is now a monopoly, and that, as a result, it should be split into multiple smaller companies. In an op-ed in The New York Times, Hughes said he was concerned that Zuckerberg had surrounded himself with a team that did not challenge him, and that it is the U.S. government's job to hold him accountable and curb his "unchecked power". He also said that "Mark's power is unprecedented and un-American." Several U.S. politicians agreed with Hughes. European Union Commissioner for Competition Margrethe Vestager stated that splitting Facebook should be done only as "a remedy of the very last resort", and that it would not solve Facebook's underlying problems. Revenue Facebook ranked No. 34 in the 2020 Fortune 500 list of the largest United States corporations by revenue, with almost $86 billion in revenue most of it coming from advertising. One analysis of 2017 data determined that the company earned US$20.21 per user from advertising. According to New York, since its rebranding, Meta has reportedly lost $500 billion as a result of new privacy measures put in place by companies such as Apple and Google which prevents Meta from gathering users' data. In February 2015, Facebook announced it had reached two million active advertisers, with most of the gain coming from small businesses. An active advertiser was defined as an entity that had advertised on the Facebook platform in the last 28 days. In March 2016, Facebook announced it had reached three million active advertisers with more than 70% from outside the United States. Prices for advertising follow a variable pricing model based on auctioning ad placements, and potential engagement levels of the advertisement itself. Similar to other online advertising platforms like Google and Twitter, targeting of advertisements is one of the chief merits of digital advertising compared to traditional media. Marketing on Meta is employed through two methods based on the viewing habits, likes and shares, and purchasing data of the audience, namely targeted audiences and "look alike" audiences. The U.S. IRS challenged the valuation Facebook used when it transferred IP from the U.S. to Facebook Ireland (now Meta Platforms Ireland) in 2010 (which Facebook Ireland then revalued higher before charging out), as it was building its double Irish tax structure. The case is ongoing and Meta faces a potential fine of $3–5bn. The U.S. Tax Cuts and Jobs Act of 2017 changed Facebook's global tax calculations. Meta Platforms Ireland is subject to the U.S. GILTI tax of 10.5% on global intangible profits (i.e. Irish profits). On the basis that Meta Platforms Ireland Limited is paying some tax, the effective minimum US tax for Facebook Ireland will be circa 11%. In contrast, Meta Platforms Inc. would incur a special IP tax rate of 13.125% (the FDII rate) if its Irish business relocated to the U.S. Tax relief in the U.S. (21% vs. Irish at the GILTI rate) and accelerated capital expensing, would make this effective U.S. rate around 12%. The insignificance of the U.S./Irish tax difference was demonstrated when Facebook moved 1.5bn non-EU accounts to the U.S. to limit exposure to GDPR. Facilities Users outside of the U.S. and Canada contract with Meta's Irish subsidiary, Meta Platforms Ireland Limited (formerly Facebook Ireland Limited), allowing Meta to avoid US taxes for all users in Europe, Asia, Australia, Africa and South America. Meta is making use of the Double Irish arrangement which allows it to pay 2–3% corporation tax on all international revenue. In 2010, Facebook opened its fourth office, in Hyderabad, India, which houses online advertising and developer support teams and provides support to users and advertisers. In India, Meta is registered as Facebook India Online Services Pvt Ltd. It also has offices or planned sites in Chittagong, Bangladesh; Dublin, Ireland; and Austin, Texas, among other cities. Facebook opened its London headquarters in 2017 in Fitzrovia in central London. Facebook opened an office in Cambridge, Massachusetts in 2018. The offices were initially home to the "Connectivity Lab", a group focused on bringing Internet access to those who do not have access to the Internet. In April 2019, Facebook opened its Taiwan headquarters in Taipei. In March 2022, Meta opened new regional headquarters in Dubai. In September 2023, it was reported that Meta had paid £149m to British Land to break the lease on Triton Square London office. Meta reportedly had another 18 years left on its lease on the site. As of 2023, Facebook operated 21 data centers. It committed to purchase 100% renewable energy and to reduce its greenhouse gas emissions 75% by 2020. Its data center technologies include Fabric Aggregator, a distributed network system that accommodates larger regions and varied traffic patterns. Reception US Representative Alexandria Ocasio-Cortez responded in a tweet to Zuckerberg's announcement about Meta, saying: "Meta as in 'we are a cancer to democracy metastasizing into a global surveillance and propaganda machine for boosting authoritarian regimes and destroying civil society ... for profit!'" Ex-Facebook employee Frances Haugen and whistleblower behind the Facebook Papers responded to the rebranding efforts by expressing doubts about the company's ability to improve while led by Mark Zuckerberg, and urged the chief executive officer to resign. In November 2021, a video published by Inspired by Iceland went viral, in which a Zuckerberg look-alike promoted the Icelandverse, a place of "enhanced actual reality without silly looking headsets". In a December 2021 interview, SpaceX and Tesla chief executive officer Elon Musk said he could not see a compelling use-case for the VR-driven metaverse, adding: "I don't see someone strapping a frigging screen to their face all day." In January 2022, Louise Eccles of The Sunday Times logged into the metaverse with the intention of making a video guide. She wrote: Initially, my experience with the Oculus went well. I attended work meetings as an avatar and tried an exercise class set in the streets of Paris. The headset enabled me to feel the thrill of carving down mountains on a snowboard and the adrenaline rush of climbing a mountain without ropes. Yet switching to the social apps, where you mingle with strangers also using VR headsets, it was at times predatory and vile. Eccles described being sexually harassed by another user, as well as "accents from all over the world, American, Indian, English, Australian, using racist, sexist, homophobic and transphobic language". She also encountered users as young as 7 years old on the platform, despite Oculus headsets being intended for users over 13. See also References External links 37°29′06″N 122°08′54″W / 37.48500°N 122.14833°W / 37.48500; -122.14833 |
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[SOURCE: https://en.wikipedia.org/wiki/Ursa_Minor] | [TOKENS: 4231] |
Contents Ursa Minor Ursa Minor (Latin for 'Lesser Bear', contrasting with Ursa Major), also known as the Little Bear, is a constellation located in the far northern sky. As with the Great Bear, the tail of the Little Bear may also be seen as the handle of a ladle, hence the North American name, Little Dipper: seven stars with four in its bowl like its partner the Big Dipper. Ursa Minor was one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and remains one of the 88 modern constellations. Ursa Minor has traditionally been important for navigation, particularly by mariners, because of Polaris being the north pole star. Polaris, the brightest star in the constellation, is a yellow-white supergiant and the brightest Cepheid variable star in the night sky, ranging in apparent magnitude from 1.97 to 2.00. Beta Ursae Minoris, also known as Kochab, is an aging star that has swollen and cooled to become an orange giant with an apparent magnitude of 2.08, only slightly fainter than Polaris. Kochab and 3rd-magnitude Gamma Ursae Minoris have been called the "guardians of the pole star" or "Guardians of The Pole". Planets have been detected orbiting four of the stars, including Kochab. The constellation also contains an isolated neutron star—Calvera—and H1504+65, the second-hottest white dwarf yet discovered, with a surface temperature of 200,000 K. History and mythology In the Babylonian star catalogues, Ursa Minor was known as the "Wagon of Heaven" (MULMAR.GÍD.DA.AN.NA, also associated with the goddess Damkina). It is listed in the MUL.APIN catalogue, compiled around 1000 BC, among the "Stars of Enlil"—that is, the northern sky. According to Diogenes Laërtius, citing Callimachus, Thales of Miletus "measured the stars of the Wagon by which the Phoenicians sail". Diogenes identifies these as the constellation of Ursa Minor, which for its reported use by the Phoenicians for navigation at sea were also named Phoinikē. The tradition of naming the northern constellations "bears" appears to be genuinely Greek, although Homer refers to just a single "bear". The original "bear" is thus Ursa Major, and Ursa Minor was admitted as the second, or "Phoenician Bear" (Ursa Phoenicia, hence Φοινίκη, Phoenice) only later, according to Strabo (I.1.6, C3) due to a suggestion by Thales, who suggested it as a navigation aid to the Greeks, who had been navigating by Ursa Major. In classical antiquity, the celestial pole was somewhat closer to Beta Ursae Minoris than to Alpha Ursae Minoris, and the entire constellation was taken to indicate the northern direction. Since the medieval period, it has become convenient to use Alpha Ursae Minoris (or "Polaris") as the North Star. (Even though, in the medieval period, Polaris was still several degrees away from the celestial pole.[a] ) Now, Polaris is within 1° of the north celestial pole and remains the current Pole star. Its Neo-Latin name of stella polaris was coined only in the early modern period. Another ancient name of the constellation is Cynosura (Greek Κυνοσούρα "dog's tail"). The origin of this name is unclear (Ursa Minor being a "dog's tail" would imply that another constellation nearby is "the dog", but no such constellation is known). Instead, the mythographic tradition of Catasterismi makes Cynosura the name of an Oread nymph described as a nurse of Zeus, honoured by the god with a place in the sky. There are various proposed explanations for the name Cynosura. One suggestion connects it to the myth of Callisto, with her son Arcas replaced by her dog being placed in the sky by Zeus. Others have suggested that an archaic interpretation of Ursa Major was that of a cow, forming a group with Boötes as herdsman, and Ursa Minor as a dog. George William Cox explained it as a variant of Λυκόσουρα, understood as "wolf's tail" but by him etymologized as "trail, or train, of light" (i.e. λύκος "wolf" vs. λύκ- "light"). Allen points to the Old Irish name of the constellation, drag-blod "fire trail", for comparison. Brown (1899) suggested a non-Greek origin of the name (a loan from an Assyrian An‑nas-sur‑ra "high-rising"). An alternative myth tells of two bears that saved Zeus from his murderous father Cronus by hiding him on Mount Ida. Later Zeus set them in the sky, but their tails grew long from their being swung up into the sky by the god. Because Ursa Minor consists of seven stars, the Latin word for "north" (i.e., where Polaris points) is septentrio, from septem (seven) and triones (oxen), from seven oxen driving a plough, which the seven stars also resemble. This name has also been attached to the main stars of Ursa Major. In Inuit astronomy, the three brightest stars — Polaris, Kochab, and Pherkad — were known as Nuutuittut ("never moving"), though the term is more frequently used in the singular to refer to Polaris alone. The Pole Star is too high in the sky at far northern latitudes to be of use in navigation. In Chinese astronomy, the main stars of Ursa Minor are divided between two asterisms: 勾陳 Gòuchén (Curved Array) (including α UMi, δ UMi, ε UMi, ζ UMi, η UMi, θ UMi, λ UMi) and 北極 Běijí (Northern Pole) (including β UMi and γ UMi). Characteristics Ursa Minor is bordered by Camelopardalis to the west, Draco to the west, and Cepheus to the east. Covering 256 square degrees, it ranks 56th of the 88 constellations in size. Ursa Minor is colloquially known in the US as the Little Dipper because its seven brightest stars seem to form the shape of a dipper (ladle or scoop). The star at the end of the dipper handle is Polaris. Polaris can also be found by following a line through the two stars—Alpha and Beta Ursae Majoris, popularly called the Pointers—that form the end of the "bowl" of the Big Dipper, for 30 degrees (three upright fists at arms' length) across the night sky. The four stars constituting the bowl of the Little Dipper are of second, third, fourth, and fifth magnitudes, respectively, and provide an easy guide to determining what magnitude stars are visible, useful for city dwellers or testing one's eyesight. The three-letter abbreviation for the constellation, as adopted by the IAU (International Astronomical Union) in 1922, is "UMi". The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a polygon of 22 segments (illustrated in infobox). In the equatorial coordinate system, the right ascension coordinates of these borders lie between 08h 41.4m and 22h 54.0m , while the declination coordinates range from the north celestial pole to 65.40° in the south. Its position in the far northern celestial hemisphere means that the whole constellation is visible only to observers in the northern hemisphere.[b] Features The German cartographer Johann Bayer used the Greek letters alpha to theta to label the most prominent stars in the constellation, while his countryman Johann Elert Bode subsequently added iota through phi. Only lambda and pi remain in use, likely because of their proximity to the north celestial pole. Within the constellation's borders, there are 39 stars brighter than or equal to apparent magnitude 6.5.[c] The traditional names of the main seven in Johann Bayer's ordering are: Marking the Little Bear's tail, Polaris, or Alpha Ursae Minoris, is the brightest star in the constellation, varying between apparent magnitudes 1.97 and 2.00 over a period of 3.97 days. Located around 432 light-years away from Earth, it is a yellow-white supergiant that varies between spectral types F7Ib and F8Ib, and has around 6 times the Sun's mass, 2,500 times its luminosity, and 45 times its radius. Polaris is the brightest Cepheid variable star visible from Earth. It is a triple star system, the supergiant primary star having two yellow-white main-sequence star companions that are 17 and 2,400 astronomical units (AU) distant and take 29.6 and 42,000 years respectively to complete one orbit. Traditionally called Kochab, Beta Ursae Minoris, at apparent magnitude 2.08, is slightly less bright than Polaris. Located around 131 light-years away from Earth,[d] it is an orange giant—an evolved star that has used up the hydrogen in its core and moved off the main sequence—of spectral type K4III. Slightly variable over a period of 4.6 days, Kochab has had its mass estimated at 1.3 times that of the Sun via measurement of these oscillations. Kochab is 450 times more luminous than the Sun and has 42 times its diameter, with a surface temperature of approximately 4,130 K. Estimated to be around 2.95 billion years old, ±1 billion years, Kochab was announced to have a planetary companion around 6.1 times as massive as Jupiter with an orbit of 522 days. Traditionally known as Pherkad, Gamma Ursae Minoris has an apparent magnitude that varies between 3.04 and 3.09 roughly every 3.4 hours. It and Kochab have been termed the "guardians of the pole star". A white bright giant of spectral type A3II-III, with around 4.8 times the Sun's mass, 1,050 times its luminosity and 15 times its radius, it is 487±8 light-years distant from Earth. Pherkad belongs to a class of stars known as Delta Scuti variables—short period (six hours at most) pulsating stars that have been used as standard candles and as subjects to study asteroseismology. Also possibly a member of this class is Zeta Ursae Minoris, a white star of spectral type A3V, which has begun cooling, expanding and brightening. It is likely to have been a B3 main-sequence star and is now slightly variable. At magnitude 4.95 the dimmest of the seven stars of the Little Dipper is Eta Ursae Minoris. A yellow-white main-sequence star of spectral type F5V, it is 97 light-years distant. It is double the Sun's diameter, 1.4 times as massive, and shines with 7.4 times its luminosity. Nearby Zeta lies 5.00-magnitude Theta Ursae Minoris. Located 860 ± 80 light-years distant, it is an orange giant of spectral type K5III that has expanded and cooled off the main sequence, and has an estimated diameter around 4.8 times that of the Sun. Making up the handle of the Little Dipper are Delta Ursae Minoris, or Yildun, and Epsilon Ursae Minoris. Just over 3.5 degrees from the north celestial pole, Delta is a white main-sequence star of spectral type A1V with an apparent magnitude of 4.35, located 172±1 light-years from Earth. It has around 2.8 times the diameter and 47 times the luminosity of the Sun. A triple star system, Epsilon Ursae Minoris shines with a combined average light of magnitude 4.22. A yellow giant of spectral type G5III, the primary is a RS Canum Venaticorum variable star. It is a spectroscopic binary, with a companion 0.36 AU distant, and a third star—an orange main-sequence star of spectral type K0—8100 AU distant. Located close to Polaris is Lambda Ursae Minoris, a red giant of spectral type M1III. It is a semiregular variable varying between magnitudes 6.35 and 6.45. The northerly nature of the constellation means that the variable stars can be observed all year: The red giant R Ursae Minoris is a semiregular variable varying from magnitude 8.5 to 11.5 over 328 days, while S Ursae Minoris is a long-period variable that ranges between magnitudes 8.0 and 11 over 331 days. Located south of Kochab and Pherkad towards Draco is RR Ursae Minoris, a red giant of spectral type M5III that is also a semiregular variable ranging from magnitude 4.44 to 4.85 over a period of 43.3 days. T Ursae Minoris is another red-giant variable star that has undergone a dramatic change in status—from being a long-period (Mira) variable ranging from magnitude 7.8 to 15 over 310–315 days, to being a semiregular variable. The star is thought to have undergone a shell helium flash—a point where the shell of helium around the star's core reaches a critical mass and ignites—marked by its abrupt change in variability in 1979. Z Ursae Minoris is a faint variable star that suddenly dropped 6 magnitudes in 1992 and was identified as one of a rare class of stars—R Coronae Borealis variables. Eclipsing variables are star systems that vary in brightness because of one star passing in front of the other rather than from any intrinsic change in luminosity. W Ursae Minoris is one such system, its magnitude ranging from 8.51 to 9.59 over 1.7 days. The combined spectrum of the system is A2V, but the masses of the two component stars are unknown. A slight change in the orbital period in 1973 suggests there is a third component of the multiple star system—most likely a red dwarf—with an orbital period of 62.2±3.9 years. RU Ursae Minoris is another example, ranging from 10 to 10.66 over 0.52 days. It is a semidetached system, as the secondary star is filling its Roche lobe and transferring matter to the primary. RW Ursae Minoris is a cataclysmic variable star system that flared up as a nova in 1956, reaching magnitude 6. In 2003, it was still two magnitudes brighter than its baseline, and dimming at a rate of 0.02 magnitude a year. Its distance has been calculated as 5,000±800 parsecs (16,300 light-years), which puts its location in the galactic halo. Taken from the villain in The Magnificent Seven, Calvera is the nickname given to an X-ray source known as 1RXS J141256.0+792204 in the ROSAT All-Sky Survey Bright Source Catalog (RASS/BSC). It has been identified as an isolated neutron star, one of the closest of its kind to Earth. Ursa Minor has two enigmatic white dwarfs. Documented on January 27, 2011, H1504+65 is a faint (magnitude 15.9) star with the hottest surface temperature—200,000 K—yet discovered for a white dwarf. Its atmosphere, composed of roughly half carbon, half oxygen and 2% neon, is devoid of hydrogen and helium—its composition unexplainable by current models of stellar evolution. WD 1337+705 is a cooler white dwarf that has magnesium and silicon in its spectrum, suggesting a companion or circumstellar disk, though no evidence for either has come to light. WISE 1506+7027 is a brown dwarf of spectral type T6 that is a mere 11.1+2.3−1.3 light-years away from Earth. A faint object of magnitude 14, it was discovered by the Wide-field Infrared Survey Explorer (WISE) in 2011. Kochab aside, three more stellar systems have been discovered to contain planets. 11 Ursae Minoris is an orange giant of spectral type K4III around 1.8 times as massive as the Sun. Around 1.5 billion years old, it has cooled and expanded since it was an A-type main-sequence star. Around 390 light-years distant, it shines with an apparent magnitude of 5.04. A planet around 11 times the mass of Jupiter was discovered in 2009 orbiting the star with a period of 516 days. HD 120084 is another evolved star, a yellow giant of spectral type G7III, around 2.4 times the mass of the Sun. It has a planet 4.5 times the mass of Jupiter, with one of the most eccentric planetary orbits (e = 0.66), discovered by precisely measuring the radial velocity of the star in 2013. HD 150706 is a sunlike star of spectral type G0V some 89 light-years distant from the Solar System. It was thought to have a planet as massive as Jupiter at a distance of 0.6 AU, but this was discounted in 2007. A further study published in 2012 showed that it has a companion around 2.7 times as massive as Jupiter that takes around 16 years to complete an orbit and is 6.8 AU distant from its star. Ursa Minor is rather devoid of deep-sky objects. The Ursa Minor Dwarf, a dwarf spheroidal galaxy, was discovered by Albert George Wilson of the Lowell Observatory in the Palomar Sky Survey in 1955. Its centre is around 225000 light-years distant from Earth. In 1999, Kenneth Mighell and Christopher Burke used the Hubble Space Telescope to confirm that the galaxy had had a single burst of star formation that took place around 14 billion years ago and lasted around 2 billion years, and that the galaxy was probably as old as the Milky Way itself. NGC 3172 (also known as Polarissima Borealis) is a faint, magnitude-14.9 galaxy that happens to be the closest NGC object to the north celestial pole. It was discovered by John Herschel in 1831. NGC 6217 is a barred spiral galaxy located some 67 million light-years away, which can be located with a 10 cm (4 in) or larger telescope as an 11th-magnitude object about 2.5° east-northeast of Zeta Ursae Minoris. It has been characterized as a starburst galaxy, which means it is undergoing a high rate of star formation compared with a typical galaxy. NGC 6251 is an active supergiant elliptical radio galaxy more than 340 million light-years away from Earth. It has a Seyfert 2 active galactic nucleus, and is one of the most extreme examples of a Seyfert galaxy. This galaxy may be associated with gamma-ray source 3EG J1621+8203, which has high-energy gamma-ray emission. It is also noted for its one-sided radio jet—one of the brightest known—discovered in 1977. The Ursids, a prominent meteor shower that occurs in Ursa Minor, peaks between December 18 and 25. Its parent body is the comet 8P/Tuttle. See also Notes References External links |
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[SOURCE: https://en.wikipedia.org/wiki/2024_United_Kingdom_riots] | [TOKENS: 11036] |
Contents 2024 United Kingdom riots Far-right anti-immigration protesters: Supported by: Government of the United Kingdom: Northern Ireland Executive Supported by: Counter-protesters: Supported by: From 30 July to 5 August 2024,[a] far-right anti-immigration protests and riots occurred in England and Northern Ireland,[b] within the United Kingdom. This followed a mass stabbing of girls at a dance class in Southport on 29 July in which three children were killed. The riots were fuelled by false claims circulated by far-right groups, including Nigel Farage MP, that the perpetrator of the attack was a Muslim and an asylum seeker, in addition to broader Islamophobic, racist, and anti-immigrant sentiments that had grown leading up to the protests. The disorder included racist attacks, arson, and looting and was the largest incident of social unrest in England since 2011. By 8 August at least 177 had been imprisoned, to an average sentence of around two years and up to a nine-years, in relation to the unrest. The following month 1,280 arrests and nearly 800 charges had been made, and as of July 2025, the number of arrests increased to 1,840 with 1,103 charges. The riots began in Southport, just a few streets away from where the attack took place. A demonstration outside the Southport Mosque quickly turned violent and protesters attacked police officers, injuring over fifty, burned a police van, and attacked the mosque. Over the following days the unrest spread to other towns and cities in England and to Belfast in Northern Ireland. On 31 July, over 100 protesters were arrested in London and demonstrations occurred in Manchester, Hartlepool, and Aldershot. On 2 August, rioting took place in Sunderland, where a Citizens Advice bureau was set on fire and police officers were injured and several people were arrested. The most severe rioting took place over the weekend of 3–4 August, when anti-immigration protesters clashed with police and counter-protesters, attacked homes and businesses owned by immigrants, and attacked hotels housing asylum seekers. From 6 August the unrest began to abate; counter-protests consistently and considerably outnumbered far-right protesters, and were followed by large anti-racist rallies across the country on 7 August. Online forums, the formation of safe spaces and other activities also countered racist sentiment and supported affected communities. The riots had limited formal organisation; instead, rioters assembled around individual far-right social media personalities with the aid of far-right Telegram group chats affiliated with Active Club England, the terrorgram network, and football hooliganism firms. Groups involved in the riots included supporters of the defunct Islamophobic group English Defence League (EDL), including its former leader Tommy Robinson, members of the neo-Nazi hate group Patriotic Alternative, and the fascist political party Britain First. The riots were also supported by the neo-Nazi organisation British Movement and the far-right political party National Front. Rioters clashed with local Muslims and counter-protesters, who were mobilised by Stand Up to Racism and other anti-fascist and anti-racist groups. Background On 29 July 2024 a knife attack took place at a Taylor Swift-themed children's yoga and dance workshop. Three children were killed and eight other children were injured, with five of them in critical condition. Two adults at the event were also critically injured. When the prime minister of the United Kingdom, Keir Starmer, laid flowers in Southport the following day, he was met with "hostile shouts" from some of the public, with one asking, "How many more, Starmer? When are you going to do something?" Following the stabbing, the police said the name being circulated online was not that of the suspected attacker. Misinformation and disinformation, including false claims about the suspect's identity, nationality, religion and immigration status, were circulated on social media by high-profile far-right accounts, including by Tommy Robinson, a far-right activist who founded the now-disbanded anti-Islam English Defence League (EDL) in 2009. The false claim that the perpetrator was named "Ali Al-Shakati" is believed to have originated from the X (formerly Twitter) account of an anti-lockdown campaigner and gained a greater audience when repeated by the website Channel3Now, a website known for spreading fake news. Russia was accused of being behind a deliberate disinformation campaign, and as of 5 August 2024, the National Crime Agency and Department for Science, Innovation and Technology are investigating such claims. A newly created Southport-themed Telegram group became inundated with misinformation, including from the far-right National Front, prior to dissemination on social media platforms. The Institute for Strategic Dialogue stated that the now-deleted "Southport Wake Up" group with 14,000 members on Telegram became integral in organising and promoting the subsequent riots, and inciting hatred and violence. Disinformation was also spread on social media by the neo-Nazi group British Movement, and accelerationist Telegram channels with links to the proscribed terror groups Atomwaffen Division and National Action were used to co-ordinate and organise the riots. Merseyside Police attempted to quell speculation by confirming that the name being circulated was not connected to the case and was not the suspect. The police initially released the information that the suspect was a male, aged seventeen, from Banks in Lancashire, though born in Cardiff. It was later reported that the suspect was a British citizen born to Rwandan parents, that he had moved to the Southport area in 2013, and that he had no known links to Islam. The spread of misinformation has widely been given as the cause of the Southport riots. In a separate event, a woman was stabbed in Stirling on 3 August 2024. Tommy Robinson falsely claimed on social media that an "alleged Muslim" had been involved in an incident in which three women had been stabbed. Other accounts spread the misinformation, contributing to tensions. A man was arrested by the police, who described him as white and local to the area. The release of these details was unusual and done to curb misinformation. Timeline At approximately 20:05 BST, hundreds of protesters gathered outside Southport Mosque chanting, "No surrender!" and "English till I die!" Within several minutes, protesters clashed with police. Protesters barricaded themselves and shouted "Tommy Robinson", a far-right activist who founded the EDL. Robinson had been arrested and then released two days prior, before he fled the country, failing to appear at a High Court hearing to which he had been summonsed for alleged contempt of court. By 20:37, protesters began throwing objects at the mosque and police, leaving one officer injured. A police van was set alight as police deployed smoke canisters. Merseyside Police requested officers from Greater Manchester Police, Cheshire Constabulary, Lancashire Police, and North Wales Police. Riot police cleared the area near the mosque by 21:14 and protesters began dispersing shortly after that as night fell. By 23:14, the riot had ended. A local corner shop was damaged. The Merseyside Police Federation said that over fifty officers were injured at the Southport incident, with North West Ambulance Service reporting that twenty-seven were hospitalised and twelve were discharged at the scene. Merseyside Police stated that eight officers were seriously injured and three police dogs were wounded. One man from Standish was arrested on suspicion of possessing a bladed article. Police put in place a 24-hour Section 60 Order giving officers further stop-and-search authority, and a Section 34 Order, allowing police to direct people who are engaging in certain activities away from the area. Merseyside Police deployed additional officers after the riot, and ambulance resources remained. The following day Hope Not Hate warned of the possibility of further demonstrations by far-right groups in several cities across the country. Concerns of further violence were echoed by Merseyside Police. ITV News later reported that convicted member of banned neo-Nazi group National Action, Matthew Hankinson, had been one of the protesters. In London, the Metropolitan Police established public order conditions for a protest dubbed "Enough is Enough", the slogan of Patriotic Alternative, where far-right demonstrators clashed with police near Downing Street on 31 July. The Metropolitan Police said that 111 people were arrested for offences including assaults on officers, possession of knives and offensive weapons and violent disorder. On the evening of 31 July, a group of approximately 40 demonstrators gathered outside a Holiday Inn in the Newton Heath area of Manchester, which was purportedly housing asylum seekers. Chants were heard of the group exclaiming "we want our country back", a phrase associated with far-right groups in the UK. Two people were arrested. Demonstrations also broke out in the County Durham town of Hartlepool on the same evening. Objects including eggs and glass bottles were thrown at the police in response to the latter's riot shields. Several police officers were injured and a police car was set alight. Eight people were arrested. There was also a protest outside a hotel being used by the government to house asylum seekers in Aldershot. Hampshire's police and crime commissioner Donna Jones described "mob-type" behaviour, and Hampshire Constabulary reported a crowd of 200 people, with a minority throwing objects and subjecting people to racial abuse. The organiser of a march in Middlesbrough was arrested by Cleveland Police on suspicion of possessing a firearm with intent to cause fear of violence. On the evening of 2 August, protesters gathered in Sunderland's Keel Square for a march around the city centre. Mounted officers from Northumbria Police attended the demonstration along with officers in riot gear. Police and protesters clashed outside a mosque in St Mark's Road after some of the marchers attempted to approach the building. The protesters chanted "save our kids" and "we want our country back", as well as slogans in support of Tommy Robinson, and Islamophobic slurs. An Uber taxi was burnt and shops looted. Sunderland Central police station was set alight, and trains to Sunderland station were cancelled or diverted to St Peter's. Four officers were hospitalised and 12 people were arrested. Around a hundred protesters shouting anti-immigrant slogans gathered in Liverpool on the same evening. On 3 August, numerous far-right rallies and counter-protests occurred in England. In Leeds, approximately 150 protesters chanted slogans such as "You're not English anymore", with around 250 counter-protesters chanting "Say it loud, say it clear, refugees are welcome here". In Manchester, 150 protesters took part in the "Enough is Enough" protest, while 350 locals turned out for the "Stop the Far Right" counter-protest. In Nottingham, clashes were reported between opposing groups of protesters. In Liverpool, two groups who had been taking part in separate protests joined up at the Pier Head before moving on to The Strand and Church Street. Many shops were damaged and looted as Spellow Library, a community hub in Walton was torched and wheelie bins set alight. A police officer was assaulted after being pushed off his motorbike and another hit in the head by a chair as protesters threw bottles, bricks and a flare at officers. 23 people were arrested in relation to the disorder as two police officers were hospitalised with a broken jaw and broken nose respectively. In Stoke-on-Trent, a far-right march clashed with local counter-protest groups, primarily made up of Muslim men and youth, outside a local mosque, with missiles thrown at riot police. Three officers were injured and 10 people were arrested. In Manchester, 'scuffles' with police led to two arrests. Two people were arrested in Leicester city centre and a protest on The Headrow in Leeds led to one arrest. Twenty arrests were made in Blackpool after violent disorder broke out amongst nearly 1,000 protesters, with bottles and other projectiles thrown at police. Attendees of the nearby annual punk festival Rebellion formed an anti-fascist counter-protest leading to a stand-off in which chairs, bottles and planks of wood were thrown. Police reported there had also been "minor disruption" in Blackburn and Preston. Police in Bristol made multiple arrests and closed roads after protesters gathered in Castle Park, where they clashed with counter-protesters who outnumbered them. Anti-racist protesters left Castle Park and linked arms with others in front of the Mercure Hotel after receiving information that far-right protesters might target the location, as it housed asylum seekers. The anti-racist protesters arrived at the hotel shortly before the far-right group and the police. The protesters faced violent attempts by the far-right to force their way through the protective line and into the hotel. Avon and Somerset Police arrested 14 people in relation to the protests. Twenty-five people were arrested in Hull, where rioters attacked police with bricks and fireworks, set vehicles alight and looted several shops, including a Shoe Zone which was set on fire, in unrest which left 11 police officers injured. A video circulated online of a mob of rioters surrounding and attacking an Asian man in his car saying the word "kill" while shouting racial slurs. A hotel housing asylum seekers was also attacked, with rioters throwing bricks and smashing windows. Outside England, there were also protests and violence in Belfast, Northern Ireland. Anti-immigration and anti-racism demonstrators faced off outside Belfast City Hall and were kept apart by riot police. A firework was thrown toward the anti-racism demonstration. The anti-immigration protesters then attempted to march to the Belfast Islamic Centre, but were blocked by police. Instead, they attacked several immigrant-owned businesses on Botanic Avenue. Violence continued in the Sandy Row area that night, where a supermarket and a café owned by immigrants were burnt out. Cars were burned and missiles were thrown at police, injuring three officers. Four people were arrested for the violence. Elsewhere in Northern Ireland, the M5 motorway was closed due to protest activity in Newtownabbey, and there were protests in Bangor and Carrickfergus. In Cardiff, reports of a planned far-right protest, which never materialised, led to an anti-racism demonstration. A woman was stabbed on King Street in Stirling and there was online speculation from anti-Islam campaigner Tommy Robinson that the attacker was Muslim. Police Scotland issued a public statement stating that the attacker was a white man and had been arrested. In Doncaster, a planned far-right protest was cancelled after only one person showed up. In Wath upon Dearne in the Metropolitan Borough of Rotherham, there were demonstrations by anti-immigration and anti-racism protesters, with the former outnumbering the latter. There was then rioting outside a Holiday Inn Express hotel which had housed asylum seekers, where mask-wearing anti-immigration demonstrators threw objects at the building, smashing a number of windows and attempting to set the building on fire with a bin full of flammable material. They were also heard to chant "Get them out". South Yorkshire Police reported that 51 officers, as well as police dogs and horses, were injured during the violence in Rotherham, where concrete blocks, chairs, fire extinguishers and tree branches were thrown at them. Greater Manchester Police issued a Section 34 dispersal notice covering Bolton. There were again demonstrations by far-right protesters and anti-racist counter-protesters, made up of primarily Asian men, who were kept separate by the police. In Middlesbrough rioters targeted houses and cars in a residential area, smashing windows. Multiple cars were set alight and burning wheelie bins were pushed at a line of police officers, who were also targeted by missiles. Teesside University's Olympia Building had its windows broken, as did some houses and cars. Cleveland Police said that a number of properties on Parliament Road and the Crown Court building were significantly damaged, and a total of 43 people were arrested in connection to the disorder. There was further rioting outside a second Holiday Inn Express hotel in Tamworth, which had been housing asylum seekers. Objects were thrown at the building and at the police, one of whom was injured, windows were smashed and part of the building was set on fire. Three police dogs were injured, one of whom was hit in the head by a brick. In Solihull, there was a large anti-immigrant protest in the town centre, which forced the closure of the Touchwood shopping centre. Later, in the evening, West Midlands Police were called to Hermitage Road, where they dispersed two groups of people who were outside The Hub mosque. Police stated they were investigating whether one of these groups may have been connected to an anti-racism protest that was held in Birmingham city centre earlier that day. Protests also occurred in Hull and Weymouth, with a counter-protest at the latter. In Lancaster, two businesses had their windows smashed during a face off between far-right and anti-fascist protesters. A protest in Sheffield led to one arrest for a public order offence, as well as a far-right protester being injured after he was attacked. Three people were arrested and two police officers injured during a protest in Weymouth. Anti-racism protesters gathered in Cardiff following a far-right protest which had been planned, where they encountered some far-right demonstrators outside the Senedd, though no conflict materialised. In Birmingham, a large group of Muslim locals gathered around a mosque in anticipation of a far-right protest which was rumoured to be scheduled in the area. Individuals were observed keeping watch around the Village Islamic Centre, while nearby shops closed, a hospital sent staff home, and several doctors' surgeries also closed early preparing for potential violence. Several vehicles close to Stechford police station were attacked amid the protest. A Sky News crew was followed by a man in a balaclava wielding a knife who slashed their van's tyre. Before this, the Sky News broadcast from the scene was interrupted by a small group of these protesters, with one shouting "free Palestine" and "fuck the EDL". A lone man outside at a pub in Yardley was also attacked by a group. The Birmingham Mail reported that video footage of the incident shows it starting with words being exchanged before one member of the group starts assaulting the man. Others then join in the beating while some try to break up the attack. Sky News' Midlands correspondent Becky Cotterill posted to X the next day that the manager of the pub had told her the man had goaded his attackers by using offensive language as they walked past. He was barred from the pub for "inciting violence." In Plymouth, many businesses closed early, bus routes were diverted and a performance at the Theatre Royal was cancelled as two protests were planned to take place in the city. Plymouth City Council warned residents to stay away from the city centre as Devon and Cornwall Police said they would be increasing their presence there. Police lined Royal Parade as the two groups of protesters – one anti-fascist and the other far-right – faced off, throwing items including glass and stones at each other as one woman on the anti-fascist side was injured by a flying item. As the protests continued into the night, bottles, bricks and fireworks were thrown and arrests were made. Three police officers were carried away from the scene after being injured, with a police van being damaged. Shortly before 10 p.m., Devon and Cornwall Police reported that 150 officers were deployed in the city centre. A TK Maxx's shopfront was smashed and brick paving was torn up in the city centre. In a statement the police revealed that six arrests had been made relating to the disorder and 'several' officers were injured, as well as some members of the public, two of whom were hospitalised. Outside England, there was further violence in the Sandy Row area of Belfast, Northern Ireland. A business was targeted for a second time, and armoured police Land Rovers were attacked with petrol bombs and bricks. Police fired two plastic bullets at rioters in response. A man in his 50s was taken to hospital following a serious assault in which his attackers "stamped on his head" as other members of the public tried to shield him. Police were treating the attack as a racially motivated hate crime. Assistant Chief Constable Melanie Jones of the PSNI said there was loyalist paramilitary involvement in the violence. Bricks were thrown at police officers in Darlington after "two large groups of mostly males" gathered in the North Lodge Park area, which is near a mosque. There was one arrest. A unity rally took place in Oxford at Carfax Tower. Multiple Muslim graves in the Burnley Cemetery were vandalized, which Lancashire Police investigated as a hate crime. On 5 August, a list of at least 39 immigration law specialists, asylum support organisations and immigration services across England, originally published on the Telegram messaging app along with the phrase "no more immigration" and other anti-migration sentiment and widely circulated on social media, identified their addresses as targets for far-right demonstrations over the coming week. Aftermath In the Shankill area of Belfast, masked men rammed a hijacked car into an estate agents, amid false claims that the agency was renting homes to asylum seekers. Nearby, masked men attacked immigrants' homes and cars. In west Belfast, youths racially abused staff at a Middle Eastern shop. Altogether, six people (three men, three teenagers) were arrested over the disorder. One person was arrested and 37 dispersal orders issued in Durham over fears of potential unrest as reports of planned disorder circulated online. However, despite these reports, there were no reported incidents of criminal damage or disorder in the city. On 7 August, over 100 far-right and 30 counter protests were reportedly planned across the country in 41 of 43 police force areas in England and Wales, with their main focus being immigration centres and lawyers' offices. However, very few far-right protesters turned out. Instead, anti-racist rallies were held across the country with counter protests dominating the evening, involving approximately 25,000 counter-protesters. Parts of London, including Brentford, Harrow, North Finchley, and Walthamstow, saw large counter-protests at sites mentioned on the list of targets where far-right protesters were supposedly going to gather, with the latter attracting an estimated 10,000 demonstrators. In Lewisham a rally was held, organised by Stand Up To Racism and other local anti-racist groups, to "show solidarity" with communities targeted by the far right, though there was no direct threat to the area. Some local businesses closed early, and market traders were told by the council to close "earlier than usual" ahead of potential protests. This led to some confusion about whether the far-right were also planning to gather in the area, but Mayor of Lewisham Brenda Dacres confirmed on the day to News Shopper that there was no intelligence of any planned far-right activity in Lewisham that night. A similar situation happened in Stoke Newington in Hackney, where SUTR also organised a solidarity rally, although reporting by Hackney Gazette suggests it was because of rumours circulated online that a far-right demonstration had been planned for outside The Old Fire Station on Leswin Road. The Metropolitan Police declined to comment on whether it was aware of any far-right action planned in the area. The Washington Post reported that patients in multiple areas including Walthamstow received text messages explaining that their doctor's offices would close early on Wednesday to avoid "threatened disruption" due to the riots. In Liverpool, a human shield was formed outside a former church, now used by a charity for asylum seekers, by hundreds of protesters. Brighton saw a group of eight anti-immigration protesters surrounded by police to protect them from around 2,000 counter-protesters on Queen's Road; another protest in Hastings also saw a crowd of hundreds of anti-racism protesters. Over 2,000 people attended a counter-protest in Old Market, Bristol, where scenes were mostly peaceful despite one arrest after a bottle and a brick were thrown at a police vehicle. Around 500 anti-racist counter-protesters gathered in Westcliff-on-Sea, Southend, to oppose an expected far-right protest that did not materialise. One individual in the area was arrested by police on suspicion of possessing an offensive weapon. Hundreds of anti-racism protesters gathered in Birmingham's Jewellery Quarter following reports a refugee and migrant centre would be the target of a far-right protest. Around 600 people gathered at Magdalen Road in Oxford over fears that a mosque would be targeted. Counter-protests occurred elsewhere in the country, including Normanton, Derby, Newcastle, Sheffield and Swindon. Smaller gatherings were also present in Accrington and Tamworth, the latter being only a few miles from a hotel which was attacked on 4 August. Some protests were not as peaceful as others seen across the country, however scenes were still calm compared to the riots seen a few days prior. Chatham saw around 150 anti-immigration protesters outnumbering around 50 counter-protesters; in Aldershot, dozens of police had to separate two groups of protesters. Three people were arrested at a counter-protest in Northampton, and one person was arrested in Bournemouth, Blackpool, Middlesbrough and Portsmouth. The latter was the site of the largest anti-immigration protest of the day, with 200 people gathering and blocking Mile End Road. Two people were arrested in nearby Southampton, where up to 400 counter-protesters outnumbered around 50 far-right protesters. Belfast saw its third consecutive night of disorder, with objects thrown at police and bins set alight. Five men were arrested on suspicion of riotous behaviour. As well as east and north Belfast, police were present in the village of Mallusk near Newtownabbey amid reports of a planned protest. An anti-racism rally was attended by hundreds of people in Derry's Guildhall Square. Ricky Jones, a Dartford Labour councillor, was filmed addressing a crowd at a counter-protest in Walthamstow, East London, stating: "They are disgusting fascists and we need to cut all their throats and get rid of them all." in reference to the right-wing protests across the country. On 8 August, Jones was suspended by Labour and arrested following the release of the footage. On 9 August, he was charged with encouraging violent disorder. He pleaded not guilty on 6 September. In August 2025 he was tried for encouraging violent disorder and found not guilty. Two people were arrested in Barnsley after two groups of demonstrators clashed in the town centre. An anti-racism rally took place at Stormont outside Northern Ireland's Parliament Buildings, where the Northern Ireland Assembly was recalled from its summer recess to discuss the recent disorder in Belfast. Hundreds of anti-racists turned up to counter a planned protest outside a Holiday Inn rumoured to be housing asylum seekers in Crawley, West Sussex. BBC News reported there were four anti-immigration protesters, with one arrest made. In Paisley, Renfrewshire, 300 anti-racists, including representatives of trade unions and human rights organisations, protested against a planned far-right demonstration outside a hotel housing asylum seekers, but no anti-immigration protestors appeared. A similar demonstration took place at the Cairn Hotel, which was also housing asylum seekers, in Bathgate, where around 150 people gathered in response to an organised far-right protest. There was unrest in Northern Ireland during the early hours, with a petrol bomb thrown at a mosque in Newtownards around 1am, and cars set alight in Belfast. A man was arrested in connection with the Newtownards attack. Later that day, approximately 15,000 marched against racism in Belfast, organised by the United Against Racism group. Anti-racist demonstrations took place across Scotland in Dumfries, Dundee, Edinburgh and Glasgow. In Edinburgh, hundreds of protesters peacefully gathered outside the Scottish Parliament Building, with similar scenes taking place at Glasgow's George Square, Dumfries' Planestanes and Dundee's City Square, outside Caird Hall. Despite the demonstrations being organised in response to rumoured anti-immigration protests in Scotland, there was no sign of far-right protests. In England, anti-racist protesters outnumbered far-right protesters, with 5,000 assembling outside the Reform UK headquarters in London, and 1,000 people protesting in Liverpool and Newcastle. A recurring protest against the Gaza war in Cardiff was joined by many protesters opposing the far-right riots. In Tenby, around 100 people gathered in Tudor Square after a far-right demonstration due to take place on the Esplanade was flagged on social media, however no such gathering took place. Stand Up to Racism organised 22 protests titled "Stop the Far Right" in cities across the United Kingdom including London, Manchester and Birmingham. Responses After the Southport riot, Prime Minister Keir Starmer wrote that those who had "hijacked the vigil for the victims" had "insulted the community as it grieves" and that rioters would "feel the full force of the law." On 1 August, and following a meeting with senior police officers, Starmer announced the establishment of a national violent disorder programme to facilitate greater cooperation between police forces when dealing with violent disorder. On 4 August, Starmer said that rioters "will feel the full force of the law" and told them "You will regret taking part in this, whether directly or those whipping up this action online and then running away themselves". He added "I won't shy away from calling it what it is – far-right thuggery". Starmer later called an emergency response meeting of COBRA. After the COBRA meeting he announced the establishment of a "standing army" of specialist police officers to address the violence, and help bring it to an end. On 12 August, Downing Street confirmed that Starmer had cancelled his planned summer holiday in order to continue to address the violence. Home Secretary Yvette Cooper condemned the Southport riot as appalling and requested a criminal investigation. According to The Independent, Cooper was also "reviewing whether the far-right English Defence League [...] should be made a proscribed terrorist organisation", after its connection to the Southport riot, a suggestion echoed by Deputy Prime Minister Angela Rayner, although the EDL has ceased to exist in a formal sense. Home Office minister David Hanson said that police were monitoring organisations, and would use face recognition technology to identify anyone involved in violence. When asked by a Sky News journalist about claims of two-tier policing, Mark Rowley, the Metropolitan Police Commissioner, grabbed the reporter's microphone and threw it on the ground, for which he later apologised. Responding two days later, he said those asking the question were imperilling his officers. The Northern Ireland Assembly was recalled, and was scheduled to meet on 8 August, while Starmer rejected calls from some politicians, including Nigel Farage and Priti Patel, to recall the Westminster parliament. Following the emergence on 5 August of a list of immigration law specialists, asylum support organisations and immigration services to be targeted by far-right groups, the president of The Law Society wrote to the Prime Minister, Lord Chancellor and Home Secretary to express concerns. On 7 August, UK police announced their largest mobilisation since the 2011 England riots, due to the threat of further violence targeting asylum seekers and immigrants, with 6,000 riot police on duty throughout the country and 2,000 in reserve as reinforcements. Two days later, Police Scotland announced the deployment of 120 of its officers to Belfast in order to help deal with violence in the city. On 12 August, the UK government announced that despite a de-escalation in the riots over the weekend, government officials remained on "high alert". On 19 August, the UK government activated Operation Early Dawn, its measures to ease prison overcrowding, as more people were given custodial sentences over their roles in the riots. The measures, in place in the north of England and the Midlands, would see defendants waiting to appear in court held at police stations until a prison space became available for them. Jo Stevens, the Secretary of State for Wales, said that the measures would be in force for "a very short period", typically "a matter of days, or at the most months". Australia, Hong Kong, India, Indonesia, Malaysia, Nigeria, the Philippines, Singapore, Tanzania, the United Arab Emirates and the United States issued travel advisories and safety warnings to the United Kingdom advising their citizens to exercise caution and avoid areas where protests are taking place. Russia called on the British government to "refrain from any unjustified or unproportionate [sic] use of violence against protesters and ensure their right to freedom of assembly". The visiting Sri Lanka national cricket team raised concerns about England Tests due to the riots. The England and Wales Cricket Board responded by reassuring Sri Lanka Cricket and the team about the security arrangements in place. In Pakistan, officials charged a man with cyberterrorism after he was linked with the Channel3Now website, which spread false claims about the Southport attacker. He was later acquitted as local police did not find evidence identifying him as the originator of the false claims. Investigations, arrests and prosecutions On 3 August, the Ministry of Justice began discussions about magistrates' courts in England and Wales remaining open overnight to preliminary rule on suspects arrested, due to the anticipated increase in people held in custody for riot related offences. This also occurred during the 2011 England riots. This proposal was criticised by Nazir Afzal, a former Chief Crown Prosecutor, saying such a measure would worsen the backlog in British courts. By 5 August, police had arrested 378 people, and the first court hearings were held on a range of charges including violent disorder, assault on an emergency worker, and burglary, with some defendants pleading guilty. On 6 August 2024, a man was convicted of inciting violence, following Facebook posts advocating attacking a hotel in Leeds housing over 200 migrants, and was sentenced to 20 months in prison, of which at least half must be served in custody. A day later, the first sentences for crimes committed during the riots were handed out to three men who took part in unrest in Southport and Liverpool. The three were sentenced to periods of between 20 months and three years in prison. On 8 August, a further 21 people received prison sentences for their roles in the riots. On 9 August, two men were sentenced to 20 months and 18 months in prison respectively for affray after a counter-protest in Leeds city centre on 3 August. A 34-year-old woman was also sent to prison for 20 months after pushing a burning wheelie bin towards a line of police officers during a demonstration in Middlesbrough. Also on 9 August, a 55-year-old woman was arrested for circulating a fake name for the Southport attacker on her X account before his real identity was disclosed. On 12 August, two 12-year-old boys were among those convicted. They became the youngest people to be convicted following their involvement in disorder in Southport and Manchester. On 13 August, the National Police Chiefs' Council said 1,024 had been arrested and 575 had been charged in relation to the riots. On the same day, the case of a 13-year-old girl involved in rioting in Aldershot was among those to be heard. She pleaded guilty to violent disorder after being captured on film kicking and punching the entrance of Potters International Hotel, which was being used to house asylum seekers. On 14 August, a 53-year-old woman from Cheshire was sentenced to 15 months in prison after pleading guilty to sending a communication threatening death or serious harm over a Facebook post in which she suggested a mosque should "be blown up with the adults inside". On 15 August, a 30-year-old man who kicked and punched a black man in the face during a riot in Manchester was sentenced to a prison term of three years. The prosecutor said the attack was "motivated by racial hatred". Also on 15 August, a 15-year-old boy from Sunderland was the first person to be charged with the offence of rioting following the unrest. On 16 August, two men who were part of a mob that attacked a car containing three Romanian men in Hull on 3 August were sentenced to prison terms of six years and four years eight months respectively. Also on 16 August, a 35-year-old man was sentenced to three years for posting false information about the identity of the Southport attacker and praising rioters on his X account which had over 90,000 followers at the time of his arrest. On 19 August, two men who took part in violence outside a hotel housing asylum seekers in Rotherham were each sentenced to two years and eight months in prison. Those sentenced on 20 August included a man who threw bottles, bricks and three concrete blocks at police officers in Bristol, and who received two and a half years in prison. On 21 August, a man from Hull was sentenced to three years in prison for trying to smash the window of a police van with a concrete block. On 28 August, it was reported that an 11-year-old child was among people arrested in a series of dawn raids conducted by police. On 18 September, Ehsan Hussain, a 25-year-old man from Birmingham, was sentenced to two years and four months in prison, having pleaded guilty to distributing threatening and abusive material intended to stir up racial hatred. The man, who is Asian, posed as "Chris Nolan" an invented white far-right extremist and used a Telegram chat with 12,500 members to call for violence in mainly Muslim areas of the city. On 23 December, it was reported that a 40-year-old from Southport, who had been identified as a man seen in a viral video of the 30 July rioting, had been sentenced to two years and six months in jail after pleading guilty to violent disorder at Liverpool Crown Court, which involved throwing bins at officers and punching a police vehicle. In the viral video he can be seen walking up to a line of riot police, putting his hands on his hips, and gyrating in front of them. He is then struck in the chest and head by hurled bricks before turning around and walking back towards the crowd. As he holds his head, another brick hits him in the groin. Later that evening, officers were called to a separate incident at which he was present. They took him to Southport hospital to be treated for the head injury, where the police say he racially abused another patient. The officers recognised him from the already widely shared footage and he was arrested. On 29 July 2024, Lucy Connolly, then 41, a childminder, and the wife of a Conservative West Northamptonshire Councillor, posted a tweet calling for "[m]ass deportation now" and for hotels housing asylum seekers to be set on fire, adding: "If that makes me racist, so be it". X subsequently said the post had not violated their rules. Connolly was arrested on 6 August; she was charged with "publishing written material which was threatening, abusive or insulting intending thereby to stir up racial hatred or having regard to all the circumstances, whereby racial hatred was likely to be stirred up", she was granted bail, and appeared at Nottingham Magistrates Court on 10 August. She appeared by video and did not enter a plea, she was remanded in custody. Connolly was remanded in custody to appear at Northampton Crown Court on the 12 August. On 22 August 2024, Connolly's lawyer requested bail at the Crown Court, and was refused. On 2 September 2024, Connolly pled guilty to distributing material with the intention of stirring up racial hatred, contrary to the Public Order Act 1986. At a hearing held at Birmingham Crown Court on 17 October 2024, Judge Melbourne Inman KC sentenced Connolly to 31 months in prison, with 40% to be served. On 20 May 2025, Connolly was denied leave to appeal against her sentence. On 21 August 2025, Connolly was released from HM Prison Peterborough. On release, Connolly said she had been a political prisoner. On 9 August 2024, a 26-year old man, Tyler James Kay, was sentenced to 38 months (to serve up to half) for retweeting Connolly's posts. Elon Musk, the owner of Twitter, described the sentence as "messed up". In October 2024, the BBC confronted a 20-year-old man, who was an administrator in the "Southport Wake Up" Telegram messaging group, known as "Mr AG", and revealed him to be Charles-Emmanuel Mikko Rasanen, a neo-Nazi from Helsinki, Finland who shared online instructions on how to commit arson with the UK rioters. The channel had been set up within hours of the stabbing and soon amassed a huge following. It shared details about local protests but quickly descended into making violent threats against named individuals and locations. On 5 August Telegram appeared to remove the channel, which at that time had almost 15,000 members. It was unclear if Telegram made this decision itself or if it was at the direction of the authorities in the UK. Andrew McIntyre, a 39-year-old taxi driver, who started the group was jailed for seven and a half years in January 2025 for his role in instigating violence. Lynch was at the riot outside a Holiday Inn Express hotel housing asylum seekers in Manvers, Rotherham on 4 August 2024. He was recorded yelling "scum", "child killers", "protect my children", "we are on the streets now to protect our kids" and "you are protecting people who are killing our kids and raping them" at police during the riot. He was pictured holding a placard asserting the corruption of MPs, police chiefs, TV media, and judges and the judiciary. He was arrested and charged with violent disorder for which he pleaded guilty and was jailed for 2 years and 8 months. In sentencing Lynch on 22 August, Judge Jeremy Richardson KC said that Lynch's sign and protest were not unlawful, but his verbal abuse towards police officers during the "racist incident" crossed the line. Lynch hanged himself at HMP Moorland two months into his sentence on 19 October 2024, aged 61. Respects were paid to Lynch at the 'Unite the Kingdom' march in London a week later. Reactions The Labour MP for Southport, Patrick Hurley, said on BBC Radio 4's Today on 31 July, that the rioters were not local residents, but were "thugs who'd got the train in" and were "utterly disrespecting the families of the dead and injured children, and [...] the town". The rioters had broken windows of Southport Mosque; Hurley told Today that people "were using the horrific incident on Monday, the deaths of three little kiddies, for their own political purposes". The Liverpool Region Mosque Network and the Muslim Association of Britain released statements condemning the riot. The Reform UK leader, Nigel Farage, condemned the violence, stating: "The levels of intimidation and threat to life have no place in a functioning democracy". He called for Parliament to be recalled over the riots and suggested there was a widespread impression of "two-tier policing" as a result of "soft policing" during Black Lives Matter protests, which he said contributed to a "sense of injustice". Conservative former Home Secretary Priti Patel called Farage's comments deeply misleading and "simply not relevant right now". She told Times Radio: "There's a clear difference between effectively blocking streets or roads being closed to burning down libraries, hotels, food banks and attacking places of worship. What we have seen is thuggery, violence, racism." Patel also wrote to the Prime Minister and Home Secretary, asking them to recall parliament. Farage was criticised by the former head of UK counter-terrorism, Neil Basu, for questioning whether the truth was being withheld from the public, with Basu accusing Farage of inciting violence and creating conspiracy theories. Farage was also accused of giving legitimacy to acts of violence by Steve Rotheram, the Mayor of Liverpool City Region, after releasing a video in which he said he did not support violence, but the protests were "nothing to what could happen over the course of the next few weeks". On 2 August, ahead of anticipated protests the following weekend, the Muslim Council of Britain recommended that mosques "review and strengthen their security protocols", and counter-protests by anti-racists were organised under the banner of "Stop the far right: Don't let the racists divide us", predominantly by Stand Up to Racism. Church leaders in Northern Ireland condemned calls for anti-Islamic protests in the province at the weekend. Leaders from Jewish, Sikh, and Hindu religious communities also released statements condemning the anti-Islamic rioting. Hampshire's police and crime commissioner and Conservative politician Donna Jones released a controversial statement that was widely criticised, in which she said that arresting people was "treating the symptom and not the cause" and otherwise appeared to agree with the protesters. The media release was later removed from the Police and Crime Commission's website. Susan Scott, a Conservative Party councillor on Stockton-on-Tees council, resigned after making anti-Muslim remarks. Responding to a tweet with footage of the disorder that said the riots were due to the "effects of mass migration and open borders", Elon Musk, the owner of Twitter, tweeted on 4 August, "Civil war is inevitable". His comment was condemned by the Prime Minister's official spokesman. Musk had previously restored Tommy Robinson's account (after Robinson had been banned under Twitter's previous owners) and interacted with him on the platform. After the incident on 5 August in Yardley, Birmingham, Musk went on to refer to the Prime Minister as "two-tier Keir" and ask, "Why aren't all communities protected in Britain?", describing the government as "woke stasi". Musk later shared an image promoting a conspiracy theory that claimed "detainment camps" for the rioters were being constructed on the Falkland Islands. He subsequently deleted the image, which had originally been posted by Ashlea Simon, the co-leader of Britain First. On 5 August, Neil Basu said that the worst of the far-right violence should be treated as terrorism; "Not only does it fit the definition of terrorism, it is terrorism", in reference to attempting to burn down buildings occupied by Muslims or asylum seekers. He further described actions as a "racial cause designed to intimidate a section of the public". A YouGov poll of 2,114 people on 5–6 August found that 7% supported the riots, while 34% supported the broader peaceful protests; 21% of Reform UK voters supported the riots, 9% of Conservative voters, 3% of Labour voters, and 1% of Liberal Democrat voters. Another YouGov poll of 2,163 British adults in the same period saw immigration identified as the number one issue facing the country (51%), above the economy (44%), and crime (39%). In July, the figures were immigration 41%, the economy 53%, and crime 20%. This represented a 10-point rise in importance for immigration, and a 19-point rise for crime. According to YouGov, "It is impossible to unpick how much of the recent shift is because of the stabbings, and how much are as a result of the week-long rioting since then." The concern about crime figure is the highest value in polls since 2011, when there were also major national riots. On 7 August, Wired magazine reported that Telegram had removed a group set up in the wake of the Southport stabbing. On 9 August, King Charles III spoke by telephone with the Prime Minister and senior police officers. A statement was subsequently released by Buckingham Palace describing how "The King shared how he had been greatly encouraged by the many examples of community spirit that had countered the aggression and criminality from a few with the compassion and resilience of the many". Later, on 20 August, the King visited Southport, where he met those affected by the riots and members of the community who had participated in reconciliation efforts. The following day, he hosted the victims' families at Clarence House in London. Analysis For the Southport riot, far-right activists had been promoting the demonstration that started in Southport, prior to involvement in the riot. HuffPost described far-right activists as having "hijacked" the vigil for the victims, and the Manchester Evening News reported "far right thugs, fuelled by lies, sought to exploit the tragedy". Merseyside Police said on the night of the riot that they believed supporters of the EDL were involved in and organised the disturbances. Hope Not Hate described them as supporters of Tommy Robinson. Robinson denied the EDL were involved, while arguing that the anger in Southport was justified. A prominent member of the neo-Nazi group Patriotic Alternative took part in the riot and another member helped to promote the event. The protests and riots were fuelled by wider Islamophobia, concerns over crime, anti-migration sentiment, xenophobia, nationalism and against perceived biases by the police and media. The Independent described the riots as being "sparked by Islamophobic and racist sentiments", with examples of mosques being targeted and several violent racist attacks on ethnic minorities by the far-right in Liverpool, Hull and Bristol. Politico described the cause of the violence as "Islamophobic resentment that had long brewed across the United Kingdom" as having surfaced, citing hate crimes associated with British Muslims as being the highest among any religious group in the country, according to government data. According to Hope not Hate, although the stabbing in Southport was the catalyst, "most of these protests and riots are more broadly focused, expressive of a wider hostility to multiculturalism, anti-Muslim and anti-migrant prejudice, as well as a visceral streak of populist anti-Government sentiment". During the protests, widespread disinformation blaming immigrants and Muslims for crime were shared online. Andrew Chadwick, a professor of political communication at Loughborough University, described a viral tweet as being "deliberately fabricated to generate hostility toward ethnic minorities and immigrants, and it's a potentially Islamophobic piece of propaganda". Matthew Feldman, an expert on right-wing extremism, commented "It is difficult to think of a much better example of online harms breaching the real world than a fake story demonising Muslims and people of colour and leading to riots on the streets". Former security minister Stephen McPartland accused Russia and Vladimir Putin's regime of involvement in the campaign of misinformation, describing it as "part of the Russian playbook". Days later, The Independent reported that misinformation and conspiracy regarding the suspect remained and appeared to be the motivating force behind the protests. Extremism experts attributed the large far-right rally in London, led by Robinson a week prior to the protests as having boosted supporters, with Robinson playing a significant role in inciting outrage. The Financial Times described the evolution of the movement from "more formally organised white-supremacist groups into personality-driven splinter groups", while capitalising on social media for outreach and organising. Police officials have described organisers as being in distinct far-right groups, organising online under banners such as "enough is enough", "save our kids", and "stop the boats" (the latter in reference to migrant crossings of the English Channel), with Robinson being a central figure in calls to hold riots. Writing for The Observer, Shabana Mahmood, the Secretary of State for Justice, suggested the impact of the disorder would be "felt for months and years to come" as the volume of cases linked to the riots going through the courts would affect government plans to address a backlog of cases. Data recorded by ACLED shows the riots significantly increased the number of violent demonstrations across the United Kingdom in 2024, exceeding the totals of 2020 and 2021 which were affected by the COVID-19 pandemic. The second part of a review by the police inspectorate was published on 7 May 2025. It found that the participants in the riots were mostly locals and that the violence "was mainly unrelated to their ideology or political views". The inspectors did not find any conclusive evidence that any of the activities were co-ordinated by extremist groups, but that they were mostly incited online by "disaffected individuals, influencers or groups" and that "Some of the main reasons for the widespread disorder were social deprivation, austerity and the economic downturn, political policies and decisions on migration and asylum, and decreasing trust and confidence in policing". The chief inspector of constabulary said that misinformation and disinformation that had been posted online had been left up for too long and that helped fuel the disorder. The chief inspector also said that the police needed more powers to be available to make it easier for misinformation and disinformation published on social media to be taken down, and that the police should counter such information by putting the known facts into the public domain sooner. The National Police Chiefs' Council (NPCC) responded to the review saying that it did not accurately assess the police role in countering such online content and that a fully coordinated and cross government approach was required. The NPCC chair said, "While there are lessons to learn, it is crucial to acknowledge that law enforcement does not - and should not - regulate online content.", adding, "Responsibility for ensuring information is accurate and does not fuel harm lies with those posting it, platform providers and regulatory bodies" and that the report did not "fully recognise the successes" of the police media strategy, and how "strengthening intelligence alone is not enough to mitigate the risks posed by misinformation". Notes References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Mars#cite_note-u445-252] | [TOKENS: 11899] |
Contents Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", for its orange-red appearance. Mars is a desert-like rocky planet with a tenuous atmosphere that is primarily carbon dioxide (CO2). At the average surface level the atmospheric pressure is a few thousandths of Earth's, atmospheric temperature ranges from −153 to 20 °C (−243 to 68 °F), and cosmic radiation is high. Mars retains some water, in the ground as well as thinly in the atmosphere, forming cirrus clouds, fog, frost, larger polar regions of permafrost and ice caps (with seasonal CO2 snow), but no bodies of liquid surface water. Its surface gravity is roughly a third of Earth's or double that of the Moon. Its diameter, 6,779 km (4,212 mi), is about half the Earth's, or twice the Moon's, and its surface area is the size of all the dry land of Earth. Fine dust is prevalent across the surface and the atmosphere, being picked up and spread at the low Martian gravity even by the weak wind of the tenuous atmosphere. The terrain of Mars roughly follows a north-south divide, the Martian dichotomy, with the northern hemisphere mainly consisting of relatively flat, low lying plains, and the southern hemisphere of cratered highlands. Geologically, the planet is fairly active with marsquakes trembling underneath the ground, but also hosts many enormous volcanoes that are extinct (the tallest is Olympus Mons, 21.9 km or 13.6 mi tall), as well as one of the largest canyons in the Solar System (Valles Marineris, 4,000 km or 2,500 mi long). Mars has two natural satellites that are small and irregular in shape: Phobos and Deimos. With a significant axial tilt of 25 degrees, Mars experiences seasons, like Earth (which has an axial tilt of 23.5 degrees). A Martian solar year is equal to 1.88 Earth years (687 Earth days), a Martian solar day (sol) is equal to 24.6 hours. Mars formed along with the other planets approximately 4.5 billion years ago. During the martian Noachian period (4.5 to 3.5 billion years ago), its surface was marked by meteor impacts, valley formation, erosion, the possible presence of water oceans and the loss of its magnetosphere. The Hesperian period (beginning 3.5 billion years ago and ending 3.3–2.9 billion years ago) was dominated by widespread volcanic activity and flooding that carved immense outflow channels. The Amazonian period, which continues to the present, is the currently dominating and remaining influence on geological processes. Because of Mars's geological history, the possibility of past or present life on Mars remains an area of active scientific investigation, with some possible traces needing further examination. Being visible with the naked eye in Earth's sky as a red wandering star, Mars has been observed throughout history, acquiring diverse associations in different cultures. In 1963 the first flight to Mars took place with Mars 1, but communication was lost en route. The first successful flyby exploration of Mars was conducted in 1965 with Mariner 4. In 1971 Mariner 9 entered orbit around Mars, being the first spacecraft to orbit any body other than the Moon, Sun or Earth; following in the same year were the first uncontrolled impact (Mars 2) and first successful landing (Mars 3) on Mars. Probes have been active on Mars continuously since 1997. At times, more than ten probes have simultaneously operated in orbit or on the surface, more than at any other planet beyond Earth. Mars is an often proposed target for future crewed exploration missions, though no such mission is currently planned. Natural history Scientists have theorized that during the Solar System's formation, Mars was created as the result of a random process of run-away accretion of material from the protoplanetary disk that orbited the Sun. Mars has many distinctive chemical features caused by its position in the Solar System. Elements with comparatively low boiling points, such as chlorine, phosphorus, and sulfur, are much more common on Mars than on Earth; these elements were probably pushed outward by the young Sun's energetic solar wind. After the formation of the planets, the inner Solar System may have been subjected to the so-called Late Heavy Bombardment. About 60% of the surface of Mars shows a record of impacts from that era, whereas much of the remaining surface is probably underlain by immense impact basins caused by those events. However, more recent modeling has disputed the existence of the Late Heavy Bombardment. There is evidence of an enormous impact basin in the Northern Hemisphere of Mars, spanning 10,600 by 8,500 kilometres (6,600 by 5,300 mi), or roughly four times the size of the Moon's South Pole–Aitken basin, which would be the largest impact basin yet discovered if confirmed. It has been hypothesized that the basin was formed when Mars was struck by a Pluto-sized body about four billion years ago. The event, thought to be the cause of the Martian hemispheric dichotomy, created the smooth Borealis basin that covers 40% of the planet. A 2023 study shows evidence, based on the orbital inclination of Deimos (a small moon of Mars), that Mars may once have had a ring system 3.5 billion years to 4 billion years ago. This ring system may have been formed from a moon, 20 times more massive than Phobos, orbiting Mars billions of years ago; and Phobos would be a remnant of that ring. Epochs: The geological history of Mars can be split into many periods, but the following are the three primary periods: Geological activity is still taking place on Mars. The Athabasca Valles is home to sheet-like lava flows created about 200 million years ago. Water flows in the grabens called the Cerberus Fossae occurred less than 20 million years ago, indicating equally recent volcanic intrusions. The Mars Reconnaissance Orbiter has captured images of avalanches. Physical characteristics Mars is approximately half the diameter of Earth or twice that of the Moon, with a surface area only slightly less than the total area of Earth's dry land. Mars is less dense than Earth, having about 15% of Earth's volume and 11% of Earth's mass, resulting in about 38% of Earth's surface gravity. Mars is the only presently known example of a desert planet, a rocky planet with a surface akin to that of Earth's deserts. The red-orange appearance of the Martian surface is caused by iron(III) oxide (nanophase Fe2O3) and the iron(III) oxide-hydroxide mineral goethite. It can look like butterscotch; other common surface colors include golden, brown, tan, and greenish, depending on the minerals present. Like Earth, Mars is differentiated into a dense metallic core overlaid by less dense rocky layers. The outermost layer is the crust, which is on average about 42–56 kilometres (26–35 mi) thick, with a minimum thickness of 6 kilometres (3.7 mi) in Isidis Planitia, and a maximum thickness of 117 kilometres (73 mi) in the southern Tharsis plateau. For comparison, Earth's crust averages 27.3 ± 4.8 km in thickness. The most abundant elements in the Martian crust are silicon, oxygen, iron, magnesium, aluminum, calcium, and potassium. Mars is confirmed to be seismically active; in 2019, it was reported that InSight had detected and recorded over 450 marsquakes and related events. Beneath the crust is a silicate mantle responsible for many of the tectonic and volcanic features on the planet's surface. The upper Martian mantle is a low-velocity zone, where the velocity of seismic waves is lower than surrounding depth intervals. The mantle appears to be rigid down to the depth of about 250 km, giving Mars a very thick lithosphere compared to Earth. Below this the mantle gradually becomes more ductile, and the seismic wave velocity starts to grow again. The Martian mantle does not appear to have a thermally insulating layer analogous to Earth's lower mantle; instead, below 1050 km in depth, it becomes mineralogically similar to Earth's transition zone. At the bottom of the mantle lies a basal liquid silicate layer approximately 150–180 km thick. The Martian mantle appears to be highly heterogenous, with dense fragments up to 4 km across, likely injected deep into the planet by colossal impacts ~4.5 billion years ago; high-frequency waves from eight marsquakes slowed as they passed these localized regions, and modeling indicates the heterogeneities are compositionally distinct debris preserved because Mars lacks plate tectonics and has a sluggishly convecting interior that prevents complete homogenization. Mars's iron and nickel core is at least partially molten, and may have a solid inner core. It is around half of Mars's radius, approximately 1650–1675 km, and is enriched in light elements such as sulfur, oxygen, carbon, and hydrogen. The temperature of the core is estimated to be 2000–2400 K, compared to 5400–6230 K for Earth's solid inner core. In 2025, based on data from the InSight lander, a group of researchers reported the detection of a solid inner core 613 kilometres (381 mi) ± 67 kilometres (42 mi) in radius. Mars is a terrestrial planet with a surface that consists of minerals containing silicon and oxygen, metals, and other elements that typically make up rock. The Martian surface is primarily composed of tholeiitic basalt, although parts are more silica-rich than typical basalt and may be similar to andesitic rocks on Earth, or silica glass. Regions of low albedo suggest concentrations of plagioclase feldspar, with northern low albedo regions displaying higher than normal concentrations of sheet silicates and high-silicon glass. Parts of the southern highlands include detectable amounts of high-calcium pyroxenes. Localized concentrations of hematite and olivine have been found. Much of the surface is deeply covered by finely grained iron(III) oxide dust. The Phoenix lander returned data showing Martian soil to be slightly alkaline and containing elements such as magnesium, sodium, potassium and chlorine. These nutrients are found in soils on Earth, and are necessary for plant growth. Experiments performed by the lander showed that the Martian soil has a basic pH of 7.7, and contains 0.6% perchlorate by weight, concentrations that are toxic to humans. Streaks are common across Mars and new ones appear frequently on steep slopes of craters, troughs, and valleys. The streaks are dark at first and get lighter with age. The streaks can start in a tiny area, then spread out for hundreds of metres. They have been seen to follow the edges of boulders and other obstacles in their path. The commonly accepted hypotheses include that they are dark underlying layers of soil revealed after avalanches of bright dust or dust devils. Several other explanations have been put forward, including those that involve water or even the growth of organisms. Environmental radiation levels on the surface are on average 0.64 millisieverts of radiation per day, and significantly less than the radiation of 1.84 millisieverts per day or 22 millirads per day during the flight to and from Mars. For comparison the radiation levels in low Earth orbit, where Earth's space stations orbit, are around 0.5 millisieverts of radiation per day. Hellas Planitia has the lowest surface radiation at about 0.342 millisieverts per day, featuring lava tubes southwest of Hadriacus Mons with potentially levels as low as 0.064 millisieverts per day, comparable to radiation levels during flights on Earth. Although Mars has no evidence of a structured global magnetic field, observations show that parts of the planet's crust have been magnetized, suggesting that alternating polarity reversals of its dipole field have occurred in the past. This paleomagnetism of magnetically susceptible minerals is similar to the alternating bands found on Earth's ocean floors. One hypothesis, published in 1999 and re-examined in October 2005 (with the help of the Mars Global Surveyor), is that these bands suggest plate tectonic activity on Mars four billion years ago, before the planetary dynamo ceased to function and the planet's magnetic field faded. Geography and features Although better remembered for mapping the Moon, Johann Heinrich von Mädler and Wilhelm Beer were the first areographers. They began by establishing that most of Mars's surface features were permanent and by more precisely determining the planet's rotation period. In 1840, Mädler combined ten years of observations and drew the first map of Mars. Features on Mars are named from a variety of sources. Albedo features are named for classical mythology. Craters larger than roughly 50 km are named for deceased scientists and writers and others who have contributed to the study of Mars. Smaller craters are named for towns and villages of the world with populations of less than 100,000. Large valleys are named for the word "Mars" or "star" in various languages; smaller valleys are named for rivers. Large albedo features retain many of the older names but are often updated to reflect new knowledge of the nature of the features. For example, Nix Olympica (the snows of Olympus) has become Olympus Mons (Mount Olympus). The surface of Mars as seen from Earth is divided into two kinds of areas, with differing albedo. The paler plains covered with dust and sand rich in reddish iron oxides were once thought of as Martian "continents" and given names like Arabia Terra (land of Arabia) or Amazonis Planitia (Amazonian plain). The dark features were thought to be seas, hence their names Mare Erythraeum, Mare Sirenum and Aurorae Sinus. The largest dark feature seen from Earth is Syrtis Major Planum. The permanent northern polar ice cap is named Planum Boreum. The southern cap is called Planum Australe. Mars's equator is defined by its rotation, but the location of its Prime Meridian was specified, as was Earth's (at Greenwich), by choice of an arbitrary point; Mädler and Beer selected a line for their first maps of Mars in 1830. After the spacecraft Mariner 9 provided extensive imagery of Mars in 1972, a small crater (later called Airy-0), located in the Sinus Meridiani ("Middle Bay" or "Meridian Bay"), was chosen by Merton E. Davies, Harold Masursky, and Gérard de Vaucouleurs for the definition of 0.0° longitude to coincide with the original selection. Because Mars has no oceans, and hence no "sea level", a zero-elevation surface had to be selected as a reference level; this is called the areoid of Mars, analogous to the terrestrial geoid. Zero altitude was defined by the height at which there is 610.5 Pa (6.105 mbar) of atmospheric pressure. This pressure corresponds to the triple point of water, and it is about 0.6% of the sea level surface pressure on Earth (0.006 atm). For mapping purposes, the United States Geological Survey divides the surface of Mars into thirty cartographic quadrangles, each named for a classical albedo feature it contains. In April 2023, The New York Times reported an updated global map of Mars based on images from the Hope spacecraft. A related, but much more detailed, global Mars map was released by NASA on 16 April 2023. The vast upland region Tharsis contains several massive volcanoes, which include the shield volcano Olympus Mons. The edifice is over 600 km (370 mi) wide. Because the mountain is so large, with complex structure at its edges, giving a definite height to it is difficult. Its local relief, from the foot of the cliffs which form its northwest margin to its peak, is over 21 km (13 mi), a little over twice the height of Mauna Kea as measured from its base on the ocean floor. The total elevation change from the plains of Amazonis Planitia, over 1,000 km (620 mi) to the northwest, to the summit approaches 26 km (16 mi), roughly three times the height of Mount Everest, which in comparison stands at just over 8.8 kilometres (5.5 mi). Consequently, Olympus Mons is either the tallest or second-tallest mountain in the Solar System; the only known mountain which might be taller is the Rheasilvia peak on the asteroid Vesta, at 20–25 km (12–16 mi). The dichotomy of Martian topography is striking: northern plains flattened by lava flows contrast with the southern highlands, pitted and cratered by ancient impacts. It is possible that, four billion years ago, the Northern Hemisphere of Mars was struck by an object one-tenth to two-thirds the size of Earth's Moon. If this is the case, the Northern Hemisphere of Mars would be the site of an impact crater 10,600 by 8,500 kilometres (6,600 by 5,300 mi) in size, or roughly the area of Europe, Asia, and Australia combined, surpassing Utopia Planitia and the Moon's South Pole–Aitken basin as the largest impact crater in the Solar System. Mars is scarred by 43,000 impact craters with a diameter of 5 kilometres (3.1 mi) or greater. The largest exposed crater is Hellas, which is 2,300 kilometres (1,400 mi) wide and 7,000 metres (23,000 ft) deep, and is a light albedo feature clearly visible from Earth. There are other notable impact features, such as Argyre, which is around 1,800 kilometres (1,100 mi) in diameter, and Isidis, which is around 1,500 kilometres (930 mi) in diameter. Due to the smaller mass and size of Mars, the probability of an object colliding with the planet is about half that of Earth. Mars is located closer to the asteroid belt, so it has an increased chance of being struck by materials from that source. Mars is more likely to be struck by short-period comets, i.e., those that lie within the orbit of Jupiter. Martian craters can[discuss] have a morphology that suggests the ground became wet after the meteor impact. The large canyon, Valles Marineris (Latin for 'Mariner Valleys, also known as Agathodaemon in the old canal maps), has a length of 4,000 kilometres (2,500 mi) and a depth of up to 7 kilometres (4.3 mi). The length of Valles Marineris is equivalent to the length of Europe and extends across one-fifth the circumference of Mars. By comparison, the Grand Canyon on Earth is only 446 kilometres (277 mi) long and nearly 2 kilometres (1.2 mi) deep. Valles Marineris was formed due to the swelling of the Tharsis area, which caused the crust in the area of Valles Marineris to collapse. In 2012, it was proposed that Valles Marineris is not just a graben, but a plate boundary where 150 kilometres (93 mi) of transverse motion has occurred, making Mars a planet with possibly a two-tectonic plate arrangement. Images from the Thermal Emission Imaging System (THEMIS) aboard NASA's Mars Odyssey orbiter have revealed seven possible cave entrances on the flanks of the volcano Arsia Mons. The caves, named after loved ones of their discoverers, are collectively known as the "seven sisters". Cave entrances measure from 100 to 252 metres (328 to 827 ft) wide and they are estimated to be at least 73 to 96 metres (240 to 315 ft) deep. Because light does not reach the floor of most of the caves, they may extend much deeper than these lower estimates and widen below the surface. "Dena" is the only exception; its floor is visible and was measured to be 130 metres (430 ft) deep. The interiors of these caverns may be protected from micrometeoroids, UV radiation, solar flares and high energy particles that bombard the planet's surface. Martian geysers (or CO2 jets) are putative sites of small gas and dust eruptions that occur in the south polar region of Mars during the spring thaw. "Dark dune spots" and "spiders" – or araneiforms – are the two most visible types of features ascribed to these eruptions. Similarly sized dust will settle from the thinner Martian atmosphere sooner than it would on Earth. For example, the dust suspended by the 2001 global dust storms on Mars only remained in the Martian atmosphere for 0.6 years, while the dust from Mount Pinatubo took about two years to settle. However, under current Martian conditions, the mass movements involved are generally much smaller than on Earth. Even the 2001 global dust storms on Mars moved only the equivalent of a very thin dust layer – about 3 μm thick if deposited with uniform thickness between 58° north and south of the equator. Dust deposition at the two rover sites has proceeded at a rate of about the thickness of a grain every 100 sols. Atmosphere Mars lost its magnetosphere 4 billion years ago, possibly because of numerous asteroid strikes, so the solar wind interacts directly with the Martian ionosphere, lowering the atmospheric density by stripping away atoms from the outer layer. Both Mars Global Surveyor and Mars Express have detected ionized atmospheric particles trailing off into space behind Mars, and this atmospheric loss is being studied by the MAVEN orbiter. Compared to Earth, the atmosphere of Mars is quite rarefied. Atmospheric pressure on the surface today ranges from a low of 30 Pa (0.0044 psi) on Olympus Mons to over 1,155 Pa (0.1675 psi) in Hellas Planitia, with a mean pressure at the surface level of 600 Pa (0.087 psi). The highest atmospheric density on Mars is equal to that found 35 kilometres (22 mi) above Earth's surface. The resulting mean surface pressure is only 0.6% of Earth's 101.3 kPa (14.69 psi). The scale height of the atmosphere is about 10.8 kilometres (6.7 mi), which is higher than Earth's 6 kilometres (3.7 mi), because the surface gravity of Mars is only about 38% of Earth's. The atmosphere of Mars consists of about 96% carbon dioxide, 1.93% argon and 1.89% nitrogen along with traces of oxygen and water. The atmosphere is quite dusty, containing particulates about 1.5 μm in diameter which give the Martian sky a tawny color when seen from the surface. It may take on a pink hue due to iron oxide particles suspended in it. Despite repeated detections of methane on Mars, there is no scientific consensus as to its origin. One suggestion is that methane exists on Mars and that its concentration fluctuates seasonally. The existence of methane could be produced by non-biological process such as serpentinization involving water, carbon dioxide, and the mineral olivine, which is known to be common on Mars, or by Martian life. Compared to Earth, its higher concentration of atmospheric CO2 and lower surface pressure may be why sound is attenuated more on Mars, where natural sources are rare apart from the wind. Using acoustic recordings collected by the Perseverance rover, researchers concluded that the speed of sound there is approximately 240 m/s for frequencies below 240 Hz, and 250 m/s for those above. Auroras have been detected on Mars. Because Mars lacks a global magnetic field, the types and distribution of auroras there differ from those on Earth; rather than being mostly restricted to polar regions as is the case on Earth, a Martian aurora can encompass the planet. In September 2017, NASA reported radiation levels on the surface of the planet Mars were temporarily doubled, and were associated with an aurora 25 times brighter than any observed earlier, due to a massive, and unexpected, solar storm in the middle of the month. Mars has seasons, alternating between its northern and southern hemispheres, similar to on Earth. Additionally the orbit of Mars has, compared to Earth's, a large eccentricity and approaches perihelion when it is summer in its southern hemisphere and winter in its northern, and aphelion when it is winter in its southern hemisphere and summer in its northern. As a result, the seasons in its southern hemisphere are more extreme and the seasons in its northern are milder than would otherwise be the case. The summer temperatures in the south can be warmer than the equivalent summer temperatures in the north by up to 30 °C (54 °F). Martian surface temperatures vary from lows of about −110 °C (−166 °F) to highs of up to 35 °C (95 °F) in equatorial summer. The wide range in temperatures is due to the thin atmosphere which cannot store much solar heat, the low atmospheric pressure (about 1% that of the atmosphere of Earth), and the low thermal inertia of Martian soil. The planet is 1.52 times as far from the Sun as Earth, resulting in just 43% of the amount of sunlight. Mars has the largest dust storms in the Solar System, reaching speeds of over 160 km/h (100 mph). These can vary from a storm over a small area, to gigantic storms that cover the entire planet. They tend to occur when Mars is closest to the Sun, and have been shown to increase global temperature. Seasons also produce dry ice covering polar ice caps. Hydrology While Mars contains water in larger amounts, most of it is dust covered water ice at the Martian polar ice caps. The volume of water ice in the south polar ice cap, if melted, would be enough to cover most of the surface of the planet with a depth of 11 metres (36 ft). Water in its liquid form cannot persist on the surface due to Mars's low atmospheric pressure, which is less than 1% that of Earth. Only at the lowest of elevations are the pressure and temperature high enough for liquid water to exist for short periods. Although little water is present in the atmosphere, there is enough to produce clouds of water ice and different cases of snow and frost, often mixed with snow of carbon dioxide dry ice. Landforms visible on Mars strongly suggest that liquid water has existed on the planet's surface. Huge linear swathes of scoured ground, known as outflow channels, cut across the surface in about 25 places. These are thought to be a record of erosion caused by the catastrophic release of water from subsurface aquifers, though some of these structures have been hypothesized to result from the action of glaciers or lava. One of the larger examples, Ma'adim Vallis, is 700 kilometres (430 mi) long, much greater than the Grand Canyon, with a width of 20 kilometres (12 mi) and a depth of 2 kilometres (1.2 mi) in places. It is thought to have been carved by flowing water early in Mars's history. The youngest of these channels is thought to have formed only a few million years ago. Elsewhere, particularly on the oldest areas of the Martian surface, finer-scale, dendritic networks of valleys are spread across significant proportions of the landscape. Features of these valleys and their distribution strongly imply that they were carved by runoff resulting from precipitation in early Mars history. Subsurface water flow and groundwater sapping may play important subsidiary roles in some networks, but precipitation was probably the root cause of the incision in almost all cases. Along craters and canyon walls, there are thousands of features that appear similar to terrestrial gullies. The gullies tend to be in the highlands of the Southern Hemisphere and face the Equator; all are poleward of 30° latitude. A number of authors have suggested that their formation process involves liquid water, probably from melting ice, although others have argued for formation mechanisms involving carbon dioxide frost or the movement of dry dust. No partially degraded gullies have formed by weathering and no superimposed impact craters have been observed, indicating that these are young features, possibly still active. Other geological features, such as deltas and alluvial fans preserved in craters, are further evidence for warmer, wetter conditions at an interval or intervals in earlier Mars history. Such conditions necessarily require the widespread presence of crater lakes across a large proportion of the surface, for which there is independent mineralogical, sedimentological and geomorphological evidence. Further evidence that liquid water once existed on the surface of Mars comes from the detection of specific minerals such as hematite and goethite, both of which sometimes form in the presence of water. The chemical signature of water vapor on Mars was first unequivocally demonstrated in 1963 by spectroscopy using an Earth-based telescope. In 2004, Opportunity detected the mineral jarosite. This forms only in the presence of acidic water, showing that water once existed on Mars. The Spirit rover found concentrated deposits of silica in 2007 that indicated wet conditions in the past, and in December 2011, the mineral gypsum, which also forms in the presence of water, was found on the surface by NASA's Mars rover Opportunity. It is estimated that the amount of water in the upper mantle of Mars, represented by hydroxyl ions contained within Martian minerals, is equal to or greater than that of Earth at 50–300 parts per million of water, which is enough to cover the entire planet to a depth of 200–1,000 metres (660–3,280 ft). On 18 March 2013, NASA reported evidence from instruments on the Curiosity rover of mineral hydration, likely hydrated calcium sulfate, in several rock samples including the broken fragments of "Tintina" rock and "Sutton Inlier" rock as well as in veins and nodules in other rocks like "Knorr" rock and "Wernicke" rock. Analysis using the rover's DAN instrument provided evidence of subsurface water, amounting to as much as 4% water content, down to a depth of 60 centimetres (24 in), during the rover's traverse from the Bradbury Landing site to the Yellowknife Bay area in the Glenelg terrain. In September 2015, NASA announced that they had found strong evidence of hydrated brine flows in recurring slope lineae, based on spectrometer readings of the darkened areas of slopes. These streaks flow downhill in Martian summer, when the temperature is above −23 °C, and freeze at lower temperatures. These observations supported earlier hypotheses, based on timing of formation and their rate of growth, that these dark streaks resulted from water flowing just below the surface. However, later work suggested that the lineae may be dry, granular flows instead, with at most a limited role for water in initiating the process. A definitive conclusion about the presence, extent, and role of liquid water on the Martian surface remains elusive. Researchers suspect much of the low northern plains of the planet were covered with an ocean hundreds of meters deep, though this theory remains controversial. In March 2015, scientists stated that such an ocean might have been the size of Earth's Arctic Ocean. This finding was derived from the ratio of protium to deuterium in the modern Martian atmosphere compared to that ratio on Earth. The amount of Martian deuterium (D/H = 9.3 ± 1.7 10−4) is five to seven times the amount on Earth (D/H = 1.56 10−4), suggesting that ancient Mars had significantly higher levels of water. Results from the Curiosity rover had previously found a high ratio of deuterium in Gale Crater, though not significantly high enough to suggest the former presence of an ocean. Other scientists caution that these results have not been confirmed, and point out that Martian climate models have not yet shown that the planet was warm enough in the past to support bodies of liquid water. Near the northern polar cap is the 81.4 kilometres (50.6 mi) wide Korolev Crater, which the Mars Express orbiter found to be filled with approximately 2,200 cubic kilometres (530 cu mi) of water ice. In November 2016, NASA reported finding a large amount of underground ice in the Utopia Planitia region. The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior (which is 12,100 cubic kilometers). During observations from 2018 through 2021, the ExoMars Trace Gas Orbiter spotted indications of water, probably subsurface ice, in the Valles Marineris canyon system. Orbital motion Mars's average distance from the Sun is roughly 230 million km (143 million mi), and its orbital period is 687 (Earth) days. The solar day (or sol) on Mars is only slightly longer than an Earth day: 24 hours, 39 minutes, and 35.244 seconds. A Martian year is equal to 1.8809 Earth years, or 1 year, 320 days, and 18.2 hours. The gravitational potential difference and thus the delta-v needed to transfer between Mars and Earth is the second lowest for Earth. The axial tilt of Mars is 25.19° relative to its orbital plane, which is similar to the axial tilt of Earth. As a result, Mars has seasons like Earth, though on Mars they are nearly twice as long because its orbital period is that much longer. In the present day, the orientation of the north pole of Mars is close to the star Deneb. Mars has a relatively pronounced orbital eccentricity of about 0.09; of the seven other planets in the Solar System, only Mercury has a larger orbital eccentricity. It is known that in the past, Mars has had a much more circular orbit. At one point, 1.35 million Earth years ago, Mars had an eccentricity of roughly 0.002, much less than that of Earth today. Mars's cycle of eccentricity is 96,000 Earth years compared to Earth's cycle of 100,000 years. Mars has its closest approach to Earth (opposition) in a synodic period of 779.94 days. It should not be confused with Mars conjunction, where the Earth and Mars are at opposite sides of the Solar System and form a straight line crossing the Sun. The average time between the successive oppositions of Mars, its synodic period, is 780 days; but the number of days between successive oppositions can range from 764 to 812. The distance at close approach varies between about 54 and 103 million km (34 and 64 million mi) due to the planets' elliptical orbits, which causes comparable variation in angular size. At their furthest Mars and Earth can be as far as 401 million km (249 million mi) apart. Mars comes into opposition from Earth every 2.1 years. The planets come into opposition near Mars's perihelion in 2003, 2018 and 2035, with the 2020 and 2033 events being particularly close to perihelic opposition. The mean apparent magnitude of Mars is +0.71 with a standard deviation of 1.05. Because the orbit of Mars is eccentric, the magnitude at opposition from the Sun can range from about −3.0 to −1.4. The minimum brightness is magnitude +1.86 when the planet is near aphelion and in conjunction with the Sun. At its brightest, Mars (along with Jupiter) is second only to Venus in apparent brightness. Mars usually appears distinctly yellow, orange, or red. When farthest away from Earth, it is more than seven times farther away than when it is closest. Mars is usually close enough for particularly good viewing once or twice at 15-year or 17-year intervals. Optical ground-based telescopes are typically limited to resolving features about 300 kilometres (190 mi) across when Earth and Mars are closest because of Earth's atmosphere. As Mars approaches opposition, it begins a period of retrograde motion, which means it will appear to move backwards in a looping curve with respect to the background stars. This retrograde motion lasts for about 72 days, and Mars reaches its peak apparent brightness in the middle of this interval. Moons Mars has two relatively small (compared to Earth's) natural moons, Phobos (about 22 km (14 mi) in diameter) and Deimos (about 12 km (7.5 mi) in diameter), which orbit at 9,376 km (5,826 mi) and 23,460 km (14,580 mi) around the planet. The origin of both moons is unclear, although a popular theory states that they were asteroids captured into Martian orbit. Both satellites were discovered in 1877 by Asaph Hall and were named after the characters Phobos (the deity of panic and fear) and Deimos (the deity of terror and dread), twins from Greek mythology who accompanied their father Ares, god of war, into battle. Mars was the Roman equivalent to Ares. In modern Greek, the planet retains its ancient name Ares (Aris: Άρης). From the surface of Mars, the motions of Phobos and Deimos appear different from that of the Earth's satellite, the Moon. Phobos rises in the west, sets in the east, and rises again in just 11 hours. Deimos, being only just outside synchronous orbit – where the orbital period would match the planet's period of rotation – rises as expected in the east, but slowly. Because the orbit of Phobos is below a synchronous altitude, tidal forces from Mars are gradually lowering its orbit. In about 50 million years, it could either crash into Mars's surface or break up into a ring structure around the planet. The origin of the two satellites is not well understood. Their low albedo and carbonaceous chondrite composition have been regarded as similar to asteroids, supporting a capture theory. The unstable orbit of Phobos would seem to point toward a relatively recent capture. But both have circular orbits near the equator, which is unusual for captured objects, and the required capture dynamics are complex. Accretion early in the history of Mars is plausible, but would not account for a composition resembling asteroids rather than Mars itself, if that is confirmed. Mars may have yet-undiscovered moons, smaller than 50 to 100 metres (160 to 330 ft) in diameter, and a dust ring is predicted to exist between Phobos and Deimos. A third possibility for their origin as satellites of Mars is the involvement of a third body or a type of impact disruption. More-recent lines of evidence for Phobos having a highly porous interior, and suggesting a composition containing mainly phyllosilicates and other minerals known from Mars, point toward an origin of Phobos from material ejected by an impact on Mars that reaccreted in Martian orbit, similar to the prevailing theory for the origin of Earth's satellite. Although the visible and near-infrared (VNIR) spectra of the moons of Mars resemble those of outer-belt asteroids, the thermal infrared spectra of Phobos are reported to be inconsistent with chondrites of any class. It is also possible that Phobos and Deimos were fragments of an older moon, formed by debris from a large impact on Mars, and then destroyed by a more recent impact upon the satellite. More recently, a study conducted by a team of researchers from multiple countries suggests that a lost moon, at least fifteen times the size of Phobos, may have existed in the past. By analyzing rocks which point to tidal processes on the planet, it is possible that these tides may have been regulated by a past moon. Human observations and exploration The history of observations of Mars is marked by oppositions of Mars when the planet is closest to Earth and hence is most easily visible, which occur every couple of years. Even more notable are the perihelic oppositions of Mars, which are distinguished because Mars is close to perihelion, making it even closer to Earth. The ancient Sumerians named Mars Nergal, the god of war and plague. During Sumerian times, Nergal was a minor deity of little significance, but, during later times, his main cult center was the city of Nineveh. In Mesopotamian texts, Mars is referred to as the "star of judgement of the fate of the dead". The existence of Mars as a wandering object in the night sky was also recorded by the ancient Egyptian astronomers and, by 1534 BCE, they were familiar with the retrograde motion of the planet. By the period of the Neo-Babylonian Empire, the Babylonian astronomers were making regular records of the positions of the planets and systematic observations of their behavior. For Mars, they knew that the planet made 37 synodic periods, or 42 circuits of the zodiac, every 79 years. They invented arithmetic methods for making minor corrections to the predicted positions of the planets. In Ancient Greece, the planet was known as Πυρόεις. Commonly, the Greek name for the planet now referred to as Mars, was Ares. It was the Romans who named the planet Mars, for their god of war, often represented by the sword and shield of the planet's namesake. In the fourth century BCE, Aristotle noted that Mars disappeared behind the Moon during an occultation, indicating that the planet was farther away. Ptolemy, a Greek living in Alexandria, attempted to address the problem of the orbital motion of Mars. Ptolemy's model and his collective work on astronomy was presented in the multi-volume collection later called the Almagest (from the Arabic for "greatest"), which became the authoritative treatise on Western astronomy for the next fourteen centuries. Literature from ancient China confirms that Mars was known by Chinese astronomers by no later than the fourth century BCE. In the East Asian cultures, Mars is traditionally referred to as the "fire star" (火星) based on the Wuxing system. In 1609 Johannes Kepler published a 10 year study of Martian orbit, using the diurnal parallax of Mars, measured by Tycho Brahe, to make a preliminary calculation of the relative distance to the planet. From Brahe's observations of Mars, Kepler deduced that the planet orbited the Sun not in a circle, but in an ellipse. Moreover, Kepler showed that Mars sped up as it approached the Sun and slowed down as it moved farther away, in a manner that later physicists would explain as a consequence of the conservation of angular momentum.: 433–437 In 1610 the first use of a telescope for astronomical observation, including Mars, was performed by Italian astronomer Galileo Galilei. With the telescope the diurnal parallax of Mars was again measured in an effort to determine the Sun-Earth distance. This was first performed by Giovanni Domenico Cassini in 1672. The early parallax measurements were hampered by the quality of the instruments. The only occultation of Mars by Venus observed was that of 13 October 1590, seen by Michael Maestlin at Heidelberg. By the 19th century, the resolution of telescopes reached a level sufficient for surface features to be identified. On 5 September 1877, a perihelic opposition to Mars occurred. The Italian astronomer Giovanni Schiaparelli used a 22-centimetre (8.7 in) telescope in Milan to help produce the first detailed map of Mars. These maps notably contained features he called canali, which, with the possible exception of the natural canyon Valles Marineris, were later shown to be an optical illusion. These canali were supposedly long, straight lines on the surface of Mars, to which he gave names of famous rivers on Earth. His term, which means "channels" or "grooves", was popularly mistranslated in English as "canals". Influenced by the observations, the orientalist Percival Lowell founded an observatory which had 30- and 45-centimetre (12- and 18-in) telescopes. The observatory was used for the exploration of Mars during the last good opportunity in 1894, and the following less favorable oppositions. He published several books on Mars and life on the planet, which had a great influence on the public. The canali were independently observed by other astronomers, like Henri Joseph Perrotin and Louis Thollon in Nice, using one of the largest telescopes of that time. The seasonal changes (consisting of the diminishing of the polar caps and the dark areas formed during Martian summers) in combination with the canals led to speculation about life on Mars, and it was a long-held belief that Mars contained vast seas and vegetation. As bigger telescopes were used, fewer long, straight canali were observed. During observations in 1909 by Antoniadi with an 84-centimetre (33 in) telescope, irregular patterns were observed, but no canali were seen. The first spacecraft from Earth to visit Mars was Mars 1 of the Soviet Union, which flew by in 1963, but contact was lost en route. NASA's Mariner 4 followed and became the first spacecraft to successfully transmit from Mars; launched on 28 November 1964, it made its closest approach to the planet on 15 July 1965. Mariner 4 detected the weak Martian radiation belt, measured at about 0.1% that of Earth, and captured the first images of another planet from deep space. Once spacecraft visited the planet during the 1960s and 1970s, many previous concepts of Mars were radically broken. After the results of the Viking life-detection experiments, the hypothesis of a dead planet was generally accepted. The data from Mariner 9 and Viking allowed better maps of Mars to be made. Until 1997 and after Viking 1 shut down in 1982, Mars was only visited by three unsuccessful probes, two flying past without contact (Phobos 1, 1988; Mars Observer, 1993), and one (Phobos 2 1989) malfunctioning in orbit before reaching its destination Phobos. In 1997 Mars Pathfinder became the first successful rover mission beyond the Moon and started together with Mars Global Surveyor (operated until late 2006) an uninterrupted active robotic presence at Mars that has lasted until today. It produced complete, extremely detailed maps of the Martian topography, magnetic field and surface minerals. Starting with these missions a range of new improved crewless spacecraft, including orbiters, landers, and rovers, have been sent to Mars, with successful missions by the NASA (United States), Jaxa (Japan), ESA, United Kingdom, ISRO (India), Roscosmos (Russia), the United Arab Emirates, and CNSA (China) to study the planet's surface, climate, and geology, uncovering the different elements of the history and dynamic of the hydrosphere of Mars and possible traces of ancient life. As of 2023[update], Mars is host to ten functioning spacecraft. Eight are in orbit: 2001 Mars Odyssey, Mars Express, Mars Reconnaissance Orbiter, MAVEN, ExoMars Trace Gas Orbiter, the Hope orbiter, and the Tianwen-1 orbiter. Another two are on the surface: the Mars Science Laboratory Curiosity rover and the Perseverance rover. Collected maps are available online at websites including Google Mars. NASA provides two online tools: Mars Trek, which provides visualizations of the planet using data from 50 years of exploration, and Experience Curiosity, which simulates traveling on Mars in 3-D with Curiosity. Planned missions to Mars include: As of February 2024[update], debris from these types of missions has reached over seven tons. Most of it consists of crashed and inactive spacecraft as well as discarded components. In April 2024, NASA selected several companies to begin studies on providing commercial services to further enable robotic science on Mars. Key areas include establishing telecommunications, payload delivery and surface imaging. Habitability and habitation During the late 19th century, it was widely accepted in the astronomical community that Mars had life-supporting qualities, including the presence of oxygen and water. However, in 1894 W. W. Campbell at Lick Observatory observed the planet and found that "if water vapor or oxygen occur in the atmosphere of Mars it is in quantities too small to be detected by spectroscopes then available". That observation contradicted many of the measurements of the time and was not widely accepted. Campbell and V. M. Slipher repeated the study in 1909 using better instruments, but with the same results. It was not until the findings were confirmed by W. S. Adams in 1925 that the myth of the Earth-like habitability of Mars was finally broken. However, even in the 1960s, articles were published on Martian biology, putting aside explanations other than life for the seasonal changes on Mars. The current understanding of planetary habitability – the ability of a world to develop environmental conditions favorable to the emergence of life – favors planets that have liquid water on their surface. Most often this requires the orbit of a planet to lie within the habitable zone, which for the Sun is estimated to extend from within the orbit of Earth to about that of Mars. During perihelion, Mars dips inside this region, but Mars's thin (low-pressure) atmosphere prevents liquid water from existing over large regions for extended periods. The past flow of liquid water demonstrates the planet's potential for habitability. Recent evidence has suggested that any water on the Martian surface may have been too salty and acidic to support regular terrestrial life. The environmental conditions on Mars are a challenge to sustaining organic life: the planet has little heat transfer across its surface, it has poor insulation against bombardment by the solar wind due to the absence of a magnetosphere and has insufficient atmospheric pressure to retain water in a liquid form (water instead sublimes to a gaseous state). Mars is nearly, or perhaps totally, geologically dead; the end of volcanic activity has apparently stopped the recycling of chemicals and minerals between the surface and interior of the planet. Evidence suggests that the planet was once significantly more habitable than it is today, but whether living organisms ever existed there remains unknown. The Viking probes of the mid-1970s carried experiments designed to detect microorganisms in Martian soil at their respective landing sites and had positive results, including a temporary increase in CO2 production on exposure to water and nutrients. This sign of life was later disputed by scientists, resulting in a continuing debate, with NASA scientist Gilbert Levin asserting that Viking may have found life. A 2014 analysis of Martian meteorite EETA79001 found chlorate, perchlorate, and nitrate ions in sufficiently high concentrations to suggest that they are widespread on Mars. UV and X-ray radiation would turn chlorate and perchlorate ions into other, highly reactive oxychlorines, indicating that any organic molecules would have to be buried under the surface to survive. Small quantities of methane and formaldehyde detected by Mars orbiters are both claimed to be possible evidence for life, as these chemical compounds would quickly break down in the Martian atmosphere. Alternatively, these compounds may instead be replenished by volcanic or other geological means, such as serpentinite. Impact glass, formed by the impact of meteors, which on Earth can preserve signs of life, has also been found on the surface of the impact craters on Mars. Likewise, the glass in impact craters on Mars could have preserved signs of life, if life existed at the site. The Cheyava Falls rock discovered on Mars in June 2024 has been designated by NASA as a "potential biosignature" and was core sampled by the Perseverance rover for possible return to Earth and further examination. Although highly intriguing, no definitive final determination on a biological or abiotic origin of this rock can be made with the data currently available. Several plans for a human mission to Mars have been proposed, but none have come to fruition. The NASA Authorization Act of 2017 directed NASA to study the feasibility of a crewed Mars mission in the early 2030s; the resulting report concluded that this would be unfeasible. In addition, in 2021, China was planning to send a crewed Mars mission in 2033. Privately held companies such as SpaceX have also proposed plans to send humans to Mars, with the eventual goal to settle on the planet. As of 2024, SpaceX has proceeded with the development of the Starship launch vehicle with the goal of Mars colonization. In plans shared with the company in April 2024, Elon Musk envisions the beginning of a Mars colony within the next twenty years. This would be enabled by the planned mass manufacturing of Starship and initially sustained by resupply from Earth, and in situ resource utilization on Mars, until the Mars colony reaches full self sustainability. Any future human mission to Mars will likely take place within the optimal Mars launch window, which occurs every 26 months. The moon Phobos has been proposed as an anchor point for a space elevator. Besides national space agencies and space companies, groups such as the Mars Society and The Planetary Society advocate for human missions to Mars. In culture Mars is named after the Roman god of war (Greek Ares), but was also associated with the demi-god Heracles (Roman Hercules) by ancient Greek astronomers, as detailed by Aristotle. This association between Mars and war dates back at least to Babylonian astronomy, in which the planet was named for the god Nergal, deity of war and destruction. It persisted into modern times, as exemplified by Gustav Holst's orchestral suite The Planets, whose famous first movement labels Mars "The Bringer of War". The planet's symbol, a circle with a spear pointing out to the upper right, is also used as a symbol for the male gender. The symbol dates from at least the 11th century, though a possible predecessor has been found in the Greek Oxyrhynchus Papyri. The idea that Mars was populated by intelligent Martians became widespread in the late 19th century. Schiaparelli's "canali" observations combined with Percival Lowell's books on the subject put forward the standard notion of a planet that was a drying, cooling, dying world with ancient civilizations constructing irrigation works. Many other observations and proclamations by notable personalities added to what has been termed "Mars Fever". In the present day, high-resolution mapping of the surface of Mars has revealed no artifacts of habitation, but pseudoscientific speculation about intelligent life on Mars still continues. Reminiscent of the canali observations, these speculations are based on small scale features perceived in the spacecraft images, such as "pyramids" and the "Face on Mars". In his book Cosmos, planetary astronomer Carl Sagan wrote: "Mars has become a kind of mythic arena onto which we have projected our Earthly hopes and fears." The depiction of Mars in fiction has been stimulated by its dramatic red color and by nineteenth-century scientific speculations that its surface conditions might support not just life but intelligent life. This gave way to many science fiction stories involving these concepts, such as H. G. Wells's The War of the Worlds, in which Martians seek to escape their dying planet by invading Earth; Ray Bradbury's The Martian Chronicles, in which human explorers accidentally destroy a Martian civilization; as well as Edgar Rice Burroughs's series Barsoom, C. S. Lewis's novel Out of the Silent Planet (1938), and a number of Robert A. Heinlein stories before the mid-sixties. Since then, depictions of Martians have also extended to animation. A comic figure of an intelligent Martian, Marvin the Martian, appeared in Haredevil Hare (1948) as a character in the Looney Tunes animated cartoons of Warner Brothers, and has continued as part of popular culture to the present. After the Mariner and Viking spacecraft had returned pictures of Mars as a lifeless and canal-less world, these ideas about Mars were abandoned; for many science-fiction authors, the new discoveries initially seemed like a constraint, but eventually the post-Viking knowledge of Mars became itself a source of inspiration for works like Kim Stanley Robinson's Mars trilogy. See also Notes References Further reading External links Solar System → Local Interstellar Cloud → Local Bubble → Gould Belt → Orion Arm → Milky Way → Milky Way subgroup → Local Group → Local Sheet → Local Volume → Virgo Supercluster → Laniakea Supercluster → Pisces–Cetus Supercluster Complex → Local Hole → Observable universe → UniverseEach arrow (→) may be read as "within" or "part of". |
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[SOURCE: https://en.wikipedia.org/wiki/White_dwarf] | [TOKENS: 12284] |
Contents White dwarf A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. These are very dense objects: in an Earth-sized volume, it packs a mass that is comparable to the Sun. A white dwarf radiates light from residual heat, not from nuclear fusion. The nearest known white dwarf is Sirius B, at 8.6 light years, the smaller component of the Sirius binary star. There are currently thought to be eight white dwarfs among the one hundred star systems nearest the Sun. The unusual faintness of white dwarfs was first recognized in 1910.: 1 The name white dwarf was coined by Willem Jacob Luyten in 1922. White dwarfs are thought to be the final evolutionary state of main-sequence stars whose mass is not high enough to become a neutron star or black hole. These stars with masses from about 0.07 to 10 M☉ include over 97% of the stars in the Milky Way.: §1 The composition of the white dwarf produced will depend on the initial mass of the star. Galactic models suggest the Milky Way galaxy currently contains about ten billion white dwarfs. Once formed, the material in a white dwarf no longer undergoes fusion reactions and thus lacks a heat source to support it against gravitational collapse. Instead, it is supported only by electron degeneracy pressure, causing it to be extremely dense. The physics of degeneracy yields a maximum mass for a non-rotating white dwarf, the Chandrasekhar limit— approximately 1.44 times the mass of the Sun— beyond which electron degeneracy pressure cannot support it. A carbon–oxygen white dwarf that approaches this limit, typically by mass transfer from a companion star, may explode as a Type Ia supernova via a process known as carbon detonation; SN 1006 is a likely example. A white dwarf, very hot when it forms, gradually cools as it radiates its energy. This radiation, which initially has a high color temperature, lessens and reddens over time. Eventually, a white dwarf will cool enough that its material will begin to crystallize into a cold black dwarf. The oldest known white dwarfs still radiate at temperatures of a few thousand kelvins, which establishes an observational limit on the maximum possible age of the universe. History The first white dwarf discovered was in the triple star system of 40 Eridani, which contains the relatively bright main sequence star 40 Eridani A, orbited at a distance by the closer binary system of the white dwarf 40 Eridani B and the main sequence red dwarf 40 Eridani C. The pair 40 Eridani B/C was discovered by William Herschel on 31 January 1783. In 1910, Henry Norris Russell, Edward Charles Pickering and Williamina Fleming discovered that, despite being a dim star, 40 Eridani B was of spectral type A, or white. This star was far out of the normal pattern when Russell first created his now famous luminosity (brightness) versus spectral type (color) diagram. Publically Russell suggested that the spectral type may not be correct.: 114 However the spectral type of 40 Eridani B was independently confirmed in 1914 by Walter Adams. In 1939, Russell looked back on the discovery and noted that Pickering had suggested that such exceptions lead to breakthroughs and in this case it led to the discovery of white dwarfs.: 1 The white dwarf companion of Sirius, Sirius B, was next to be discovered. During the nineteenth century, positional measurements of some stars became precise enough to measure small changes in their location. Friedrich Bessel used position measurements to determine that the stars Sirius (α Canis Majoris) and Procyon (α Canis Minoris) were changing their positions periodically. In 1844 he predicted that both stars had unseen companions. Bessel roughly estimated the period of the companion of Sirius to be about half a century; C.A.F. Peters computed an orbit for it in 1851. It was not until 31 January 1862 that Alvan Graham Clark observed a previously unseen star close to Sirius, later identified as the predicted companion. Adams announced in 1915 that he had found the spectrum of Sirius B to be similar to that of Sirius. In 1917, Adriaan van Maanen discovered van Maanen's Star, an isolated white dwarf. These three white dwarfs, the first discovered, are the so-called classical white dwarfs.: 2 In 1922 Willem Luyten published a series of three papers on faint white stars that had high proper motion, meaning they were low-luminosity white stars close to the Earth. In his third paper he used the term dwarf; the term was later popularized by Arthur Eddington as white dwarf.: 118 18 white dwarfs had been discovered by 1939.: 3 Luyten and others continued to search for white dwarfs in the 1940s. By 1950, over a hundred were known, and by 1999, over 2000 were known. Since then the Sloan Digital Sky Survey has found over 9000 white dwarfs, mostly new. White dwarfs were found to be extremely dense soon after their discovery. If a star is in a binary system, as is the case for Sirius B or 40 Eridani B, it is possible to estimate its mass from observations of the binary orbit. This was done for Sirius B by 1910, yielding a mass estimate of 0.94 M☉, which compares well with a more modern estimate of 1.00 M☉. Since hotter bodies radiate more energy than colder ones, a star's surface brightness can be estimated from its effective surface temperature, and star's spectrum gives its temperature. If the star's distance is known, its absolute luminosity can also be estimated. From the absolute luminosity and distance, the star's surface area and its radius can be calculated. Reasoning of this sort led to the realization, puzzling to astronomers at the time, that due to their relatively high temperature and relatively low absolute luminosity, Sirius B and 40 Eridani B must be very dense. When Ernst Öpik estimated the density of visual binary stars in 1916, he found that 40 Eridani B had a density of over 25000 times that of the Sun, which was so high that he called it "impossible". As Eddington put it in 1927: We learn about the stars by receiving and interpreting the messages which their light brings to us. The message of the companion of Sirius when it was decoded ran: "I am composed of material 3000 times denser than anything you have ever come across; a ton of my material would be a little nugget that you could put in a matchbox." What reply can one make to such a message? The reply which most of us made in 1914 was—"Shut up. Don't talk nonsense.": 50 Such densities are possible because white dwarf material is not composed of atoms joined by chemical bonds, but rather consists of a plasma of unbound nuclei and electrons. There is therefore no obstacle to placing nuclei closer than normally allowed by electron orbitals limited by normal matter. Eddington wondered what would happen when this plasma cooled and the energy to keep the atoms ionized was no longer sufficient. This paradox was resolved by R. H. Fowler in 1926 by an application of the newly devised quantum mechanics. Since electrons obey the Pauli exclusion principle, no two electrons can occupy the same state, and they must obey Fermi–Dirac statistics, also introduced in 1926 to determine the statistical distribution of particles that satisfy the Pauli exclusion principle. At zero temperature, therefore, electrons cannot all occupy the lowest-energy, or ground, state; some of them would have to occupy higher-energy states, forming a band of lowest-available energy states, the Fermi sea. This state of the electrons, called degenerate, meant that a white dwarf could cool to zero temperature and still possess high energy. The existence of a limiting mass that no white dwarf can exceed without collapsing to a neutron star is another consequence of being supported by electron degeneracy pressure. Such limiting masses were calculated for cases of an idealized, constant density star in 1929 by Wilhelm Anderson and in 1930 by Edmund C. Stoner. This value was corrected by considering hydrostatic equilibrium for the density profile, and the presently known value of the limit was first published in 1931 by Subrahmanyan Chandrasekhar in his paper "The Maximum Mass of Ideal White Dwarfs". For a non-rotating white dwarf, it is equal to approximately 5.7 M☉ / μe2, where μe is the average molecular weight per electron of the star.: eqn.(63) As the carbon-12 and oxygen-16 that predominantly compose a carbon–oxygen white dwarf both have atomic numbers equal to half their atomic weight, one should take μe equal to 2 for such a star,[citation needed] leading to the commonly quoted value of 1.4 M☉. (Near the beginning of the 20th century, there was reason to believe that stars were composed chiefly of heavy elements,: 955 so, in his 1931 paper, Chandrasekhar set the average molecular weight per electron, μe, equal to 2.5, giving a limit of 0.91 M☉.) Together with William Alfred Fowler, Chandrasekhar received the Nobel Prize for this and other work in 1983. The limiting mass is now called the Chandrasekhar limit. Composition and structure Although white dwarfs are known with estimated masses as low as 0.17 M☉ and as high as 1.33 M☉, the mass distribution is strongly peaked at 0.6 M☉, and the majority lie between 0.5 and 0.7 M☉. The estimated radii of observed white dwarfs are typically 0.8–2% the radius of the Sun; this is comparable to the Earth's radius of approximately 0.9% solar radius. A white dwarf, then, packs mass comparable to the Sun's into a volume that is typically one millionth of the Sun's; the average density of matter in a white dwarf must therefore be, very roughly, 1000000 times greater than the average density of the Sun, or approximately 106 g/cm3, or 1 tonne per cubic centimetre. A typical white dwarf has a density of between 104 and 107 g/cm3. White dwarfs are composed of one of the densest forms of matter known, surpassed only by other compact stars such as neutron stars and the hypothetical quark stars. At these densities the nuclei within the star are much closer than nuclei in ordinary matter. Two nuclei in a white dwarf are separated by about 1.2×10−12 m, substantially less than a Bohr radius, 5.3×10−11 m, the rough size of a hydrogen atom. The white dwarf matter is pressure ionized: there is no room for bound electron orbitals. Rather than a hot thermal gas of atoms like the core of the Sun, the heat in the core of a white dwarf is associated with vibrating nuclei and the gas-like aspect providing pressure is due to the free electrons.: 575 This unusual source of pressure is known as electron degeneracy pressure, a consequence of quantum mechanics. The uncertainty principle requires the product of position uncertainty, Δ x {\displaystyle \Delta x} , and momentum uncertainty, Δ p x {\displaystyle \Delta p_{x}} , to be larger than half of the reduced Planck constant: Δ x × Δ p x > ℏ / 2. {\displaystyle \Delta x\times \Delta p_{x}>\hbar /2.} If the position uncertainty is small, the momentum uncertainty must increase. Furthermore, the Pauli principle of quantum mechanics requires every electron to be distinguishable, and that in turn means the uncertainty in the electron positions must be less than their average separation. Forcing the electrons close together (smaller average separation) reduces their position uncertainty causing an increase in their momentum uncertainty. More uncertain momentum must also be higher momentum. This increased momentum appears as a force that counteracts the gravitational force compressing the star.: 567 The balanced pressure at the center of a white dwarf will be on the order of 1.5 million times the pressure in the center of the Sun. The central temperature will exceed 10 million degrees K. While these conditions would fuse hydrogen the low luminosity of white dwarf stars implies the necessary nuclei are not present.: 560 A typical white dwarf star, a CO white dwarf, is 99% carbon and oxygen by mass, with the remainder being a thin layer of He and H. Main sequence stars close to the upper mass limit of 10 M☉ are thought to fuse carbon into neon, forming O-Ne white dwarf stars. Very light stars, below 0.6 M☉ never fuse He into carbon and oxygen so they form He-core white dwarfs.: 4 It takes more time than the age of the universe for a light star to burn through its fuel, so any observed He-core white dwarfs are expected to result from mass loss to a companion in an interacting binary star system. If a carbon-oxygen white dwarf accreted enough matter to reach the Chandrasekhar limit of about 1.44 solar masses (for a non-rotating star), it would no longer be able to support the bulk of its mass through electron degeneracy pressure and, in the absence of nuclear reactions, would begin to collapse. The current view is that this limit is not normally attained; increasing temperature and density inside the core ignite carbon fusion as the star approaches the limit (to within about 1%) before collapse is initiated. In contrast, for a core primarily composed of oxygen, neon and magnesium, the collapsing white dwarf will typically form a neutron star. In this case, only a fraction of the star's mass will be ejected during the collapse. If a white dwarf star accumulates sufficient material from a stellar companion to raise its core temperature enough to ignite carbon fusion, it will undergo runaway nuclear fusion, completely disrupting it. There are three avenues by which this detonation is theorised to happen: stable accretion of material from a companion, the collision of two white dwarfs, or accretion that causes ignition in a shell that then ignites the core. The dominant mechanism by which Type Ia supernovae are produced remains unclear. Despite this uncertainty in how Type Ia supernovae are produced, Type Ia supernovae have very uniform properties and are useful standard candles over intergalactic distances. Some calibrations are required to compensate for the gradual change in properties or different frequencies of abnormal luminosity supernovae at high redshift, and for small variations in brightness identified by light curve shape or spectrum. The relationship between the mass and radius of white dwarfs can be estimated using the nonrelativistic Fermi gas equation of state, which gives: 25 R R ⊙ ≈ 0.012 ( M M ⊙ ) − 1 / 3 ( μ e 2 ) − 5 / 3 , {\displaystyle {\frac {R}{R_{\odot }}}\approx 0.012\left({\frac {M}{M_{\odot }}}\right)^{-1/3}\left({\frac {\mu _{e}}{2}}\right)^{-5/3},} where R is the radius, M is the mass of the white dwarf, and the subscript ⊙ {\displaystyle \odot } indicates relative to the Sun. The chemical potential, μ e {\displaystyle \mu _{e}} is a thermodynamic property giving the change in energy as one electron is added or removed; it relates to the composition of the star. Numerical treatment of more complete models have been tested against observational data with good agreement. Since this analysis uses the non-relativistic formula p2 / 2m for the kinetic energy, it is non-relativistic. When the electron velocity in a white dwarf is close to the speed of light, the kinetic energy formula approaches pc where c is the speed of light, and it can be shown that the Fermi gas model has no stable equilibrium in the ultrarelativistic limit. In particular, this analysis yields the maximum mass of a white dwarf, which is: M l i m i t ≈ 1.46 ( μ e 2 ) − 2 {\displaystyle M_{\rm {limit}}\approx 1.46\left({\frac {\mu _{e}}{2}}\right)^{-2}} The observation of many white dwarf stars implies that either they started with masses similar to the Sun or something dramatic happened to reduce their mass. For a more accurate computation of the mass-radius relationship and limiting mass of a white dwarf, one must compute the equation of state that describes the relationship between density and pressure in the white dwarf material. If the density and pressure are both set equal to functions of the radius from the center of the star, the system of equations consisting of the hydrostatic equation together with the equation of state can then be solved to find the structure of the white dwarf at equilibrium. In the non-relativistic case, the radius is inversely proportional to the cube root of the mass.: eqn.(80) Relativistic corrections will alter the result so that the radius becomes zero at a finite value of the mass. This is the limiting value of the mass—called the Chandrasekhar limit—at which the white dwarf can no longer be supported by electron degeneracy pressure. The graph on the right shows the result of such a computation. It shows how radius varies with mass for non-relativistic (blue curve) and relativistic (green curve) models of a white dwarf. Both models treat the white dwarf as a cold Fermi gas in hydrostatic equilibrium. The average molecular weight per electron, μe, has been set equal to 2. Radius is measured in standard solar radii and mass in standard solar masses. These computations all assume that the white dwarf is non-rotating. If the white dwarf is rotating, the equation of hydrostatic equilibrium must be modified to take into account the centrifugal pseudo-force arising from working in a rotating frame. For a uniformly rotating white dwarf, the limiting mass increases only slightly. If the star is allowed to rotate nonuniformly, and viscosity is neglected, then, as was pointed out by Fred Hoyle in 1947, there is no limit to the mass for which it is possible for a model white dwarf to be in static equilibrium. Not all of these model stars will be dynamically stable. Rotating white dwarfs and the estimates of their diameter in terms of the angular velocity of rotation has been treated in the rigorous mathematical literature. The fine structure of the free boundary of white dwarfs has also been analysed mathematically rigorously. White dwarfs have low luminosity and therefore occupy a strip at the bottom of the Hertzsprung–Russell diagram, a graph of stellar luminosity versus color or temperature. They should not be confused with low-luminosity objects at the low-mass end of the main sequence, such as the hydrogen-fusing red dwarfs, whose cores are supported in part by thermal pressure, or the even lower-temperature brown dwarfs. The visible radiation emitted by white dwarfs varies over a wide color range, from the whitish-blue color of an O-, B- or A-type main sequence star to the yellow-orange of a late K- or early M-type star. White dwarf luminosity varies over 7 orders of magnitude, from over 100 times that of the Sun to under 1/ 10000 that of the Sun. Assuming the Stefan–Boltzmann law, relating luminosity to the fourth power of the effective surface temperature, white dwarf effective surface temperatures extend from over 150000 K to barely under 4000 K. Hot white dwarfs, with surface temperatures in excess of 30000 K, have been observed to be sources of soft (i.e., lower-energy) X-rays. This enables the composition and structure of their atmospheres to be studied by soft X-ray and extreme ultraviolet observations. White dwarfs also radiate neutrinos through the Urca process. This process has more effect on hotter and younger white dwarfs. Because neutrinos can pass easily through stellar plasma, they can drain energy directly from the dwarf's interior; this mechanism is the dominant contribution to cooling for approximately the first 20 million years of a white dwarf's existence. The degenerate matter that makes up the bulk of a white dwarf has a very low opacity, because any absorption of a photon requires that an electron must transition to a higher empty state, which may not be possible as the energy of the photon may not be a match for the possible quantum states available to that electron, hence radiative heat transfer within a white dwarf is low, but it has a high thermal conductivity. As a result, the interior of the white dwarf maintains an almost uniform temperature as it cools down, starting at approximately 108 K shortly after the formation of the white dwarf and reaching less than 106 K for the coolest known white dwarfs. An outer shell of non-degenerate matter sits on top of the degenerate core. The outermost layers, which are cooler than the interior, radiate roughly as a black body. A white dwarf remains visible for a long time, as its tenuous outer atmosphere slowly radiates the thermal content of the degenerate interior. As was explained by Leon Mestel in 1952, unless the white dwarf accretes matter from a companion star or other source, its radiation comes from its stored heat, which is not replenished.: §2.1 White dwarfs have an extremely small surface area to radiate this heat from, so they cool gradually, remaining hot for a long time. As a white dwarf cools, its surface temperature decreases, the radiation that it emits reddens, and its luminosity decreases. Since the white dwarf has no energy sink other than radiation, it follows that its cooling slows with time. The rate of cooling has been estimated for a carbon white dwarf of 0.59 M☉ with a hydrogen atmosphere. After initially taking approximately 1.5 billion years to cool to a surface temperature of 7140 K, cooling approximately 500 more kelvins to 6590 K takes around 0.3 billion years, but the next two steps of around 500 kelvins (to 6030 K and 5550 K) take first 0.4 and then 1.1 billion years.: Table 2 Most observed white dwarfs have relatively high surface temperatures, between 8000 K and 40000 K. However this is a selection effect: hotter, more luminous white dwarfs are easier to observe. A white dwarf spends more of its lifetime at cooler temperatures: more cool white dwarfs than hot white dwarfs exist. This trend stops at extremely cool white dwarfs; few white dwarfs are observed with surface temperatures below 4000 K, and one of the coolest so far observed, WD J2147–4035, has a surface temperature of approximately 3050 K. The reason for this is that the Universe's age is finite; there has not been enough time for white dwarfs to cool below this temperature. The white dwarf luminosity function can therefore be used to find the time when stars started to form in a region; an estimate for the age of our galactic disk found in this way is 8 billion years. A white dwarf will eventually, in many trillions of years, cool and become a non-radiating black dwarf in approximate thermal equilibrium with its surroundings and with the cosmic background radiation. No black dwarfs are thought to exist yet. At very low temperatures (<4000 K) white dwarfs with hydrogen in their atmosphere will be affected by collision induced absorption (CIA) of hydrogen molecules colliding with helium atoms. This affects the optical red and infrared brightness of white dwarfs with a hydrogen or mixed hydrogen-helium atmosphere. This makes old white dwarfs with this kind of atmosphere bluer than the main cooling sequence. White dwarfs with hydrogen-poor atmospheres, such as WD J2147–4035, are less affected by CIA and therefore have a yellow to orange color. White dwarf core material is a completely ionized plasma—a mixture of nuclei and electrons—that is initially in a fluid state. It was theoretically predicted in the 1960s that at a late stage of cooling, it should crystallize into a solid state, starting at its center. The crystal structure is thought to be a body-centered cubic lattice. In 1995 it was suggested that asteroseismological observations of pulsating white dwarfs yielded a potential test of the crystallization theory, and in 2004, observations were made that suggested approximately 90% of the mass of BPM 37093 had crystallized. Other work gives a crystallized mass fraction of between 32% and 82%. As a white dwarf core undergoes crystallization into a solid phase, latent heat is released, which provides a source of thermal energy that delays its cooling. Another possible mechanism that was suggested to explain this cooling anomaly in some types of white dwarfs is a solid–liquid distillation process: the crystals formed in the core are buoyant and float up, thereby displacing heavier liquid downward, thus causing a net release of gravitational energy. Chemical fractionation between the ionic species in the plasma mixture can release a similar or even greater amount of energy. This energy release was first confirmed in 2019 after the identification of a pile up in the cooling sequence of more than 15000 white dwarfs observed with the Gaia satellite. Low-mass helium white dwarfs (mass < 0.20 M☉), often referred to as extremely low-mass white dwarfs (ELM WDs), are formed in binary systems. As a result of their hydrogen-rich envelopes, residual hydrogen burning via the CNO cycle may keep these white dwarfs hot for hundreds of millions of years. In addition, they remain in a bloated proto-white dwarf stage for up to 2 Gyr before they reach the cooling track. Although most white dwarfs are thought to be composed of carbon and oxygen, spectroscopy typically shows that their emitted light comes from an atmosphere that is observed to be either hydrogen or helium dominated. The dominant element is usually at least 1000 times more abundant than all other elements. As explained by Schatzman in the 1940s, the high surface gravity is thought to cause this purity by gravitationally separating the atmosphere so that heavy elements are below and the lighter above.: §§5–6 This atmosphere, the only part of the white dwarf visible to us, is thought to be the top of an envelope that is a residue of the star's envelope in the AGB phase and may also contain material accreted from the interstellar medium. The envelope is believed to consist of a helium-rich layer with mass no more than 1/ 100 of the star's total mass, which, if the atmosphere is hydrogen-dominated, is overlain by a hydrogen-rich layer with mass approximately 1/ 10000 of the star's total mass.: §§4–5 Although thin, these outer layers determine the thermal evolution of the white dwarf. The degenerate electrons in the bulk of a white dwarf conduct heat well. Most of a white dwarf's mass is therefore at almost the same temperature (isothermal), and it is also hot: a white dwarf with surface temperature between 8000 K and 16000 K will have a core temperature between approximately 5000000 K and 20000000 K. The white dwarf is kept from cooling very quickly only by its outer layers' opacity to radiation. The first attempt to classify white dwarf spectra appears to have been by G.P. Kuiper in 1941, and various classification schemes have been proposed and used since then. The system currently in use was introduced by Edward M. Sion, Jesse L. Greenstein and their coauthors in 1983 and has been subsequently revised several times. It classifies a spectrum by a symbol that consists of an initial D, a letter describing the primary feature of the spectrum followed by an optional sequence of letters describing secondary features of the spectrum (as shown in the adjacent table), and a temperature index number, computed by dividing 50400 K by the effective temperature. For example, a white dwarf with only He I lines in its spectrum and an effective temperature of 15000 K could be given the classification of "DB3", or, if warranted by the precision of the temperature measurement, "DB3.5". Likewise, a white dwarf with a polarized magnetic field, an effective temperature of 17000 K, and a spectrum dominated by He I lines that also had hydrogen features could be given the classification of DBAP3. The symbols "?" and ":" may also be used if the correct classification is uncertain. White dwarfs whose primary spectral classification is DA have hydrogen-dominated atmospheres. They make up the majority, approximately 80%, of all observed white dwarfs. The next class in number is of DBs, approximately 16%. The hot, above 15000 K, DQ class (roughly 0.1%) have carbon-dominated atmospheres. Those classified as DB, DC, DO, DZ, and cool DQ have helium-dominated atmospheres. Assuming that carbon and metals are not present, which spectral classification is seen depends on the effective temperature. Between approximately 100000 K to 45000 K, the spectrum will be classified DO, dominated by singly ionized helium. From 30000 K to 12000 K, the spectrum will be DB, showing neutral helium lines, and below about 12000 K, the spectrum will be featureless and classified DC.: §2.4 Molecular hydrogen (H2) has been detected in spectra of the atmospheres of some white dwarfs. While theoretical work suggests that some types of white dwarfs may have stellar corona, searches at X-ray and radio wavelengths, where coronae are most easily detected, have been unsuccessful. A few white dwarfs have been observed to have inhomogeneous atmosphere with one side dominated by hydrogen and the other side dominated by helium. Around 25–33% of white dwarfs have metal lines in their spectra, which is notable because any heavy elements in a white dwarf should sink into the star's interior in just a small fraction of the star's lifetime. The prevailing explanation for metal-rich white dwarfs is that they have recently accreted rocky planetesimals. The bulk composition of the accreted object can be measured from the strengths of the metal lines. For example, a 2015 study of the white dwarf Ton 345 concluded that its metal abundances were consistent with those of a differentiated, rocky planet whose mantle had been eroded by the host star's wind during its asymptotic giant branch phase. Magnetic fields in white dwarfs with a strength at the surface of c. 1 million gauss (100 teslas) were predicted by P. M. S. Blackett in 1947 as a consequence of a physical law he had proposed, which stated that an uncharged, rotating body should generate a magnetic field proportional to its angular momentum. This putative law, sometimes called the Blackett effect, was never generally accepted, and by the 1950s even Blackett felt it had been refuted.: 39–43 In the 1960s, it was proposed that white dwarfs might have magnetic fields due to conservation of total surface magnetic flux that existed in its progenitor star phase. A surface magnetic field of c. 100 gauss (0.01 T) in the progenitor star would thus become a surface magnetic field of c. 100 × 1002 = 1 million gauss (100 T) once the star's radius had shrunk by a factor of 100.: §8 : 484 The first magnetic white dwarf to be discovered was GJ 742 (also known as GRW +70 8247), which was identified by James Kemp, John Swedlund, John Landstreet and Roger Angel in 1970 to host a magnetic field by its emission of circularly polarized light. It is thought to have a surface field of approximately 300 million gauss (30 kT).: §8 Since 1970, magnetic fields have been discovered in well over 200 white dwarfs, ranging from 2×103 to 109 gauss (0.2 T to 100 kT). Many of the presently known magnetic white dwarfs are identified by low-resolution spectroscopy, which is able to reveal the presence of a magnetic field of 1 megagauss or more. Thus the basic identification process also sometimes results in discovery of magnetic fields. White dwarf magnetic fields may also be measured without spectral lines, using the techniques of broadband circular polarimetry, or maybe through measurement of their frequencies of radio emission via the electron cyclotron maser. It has been estimated that at least 10% of white dwarfs have fields in excess of 1 million gauss (100 T). The magnetic fields in a white dwarf may allow for the existence of a new type of chemical bond, perpendicular paramagnetic bonding, in addition to ionic and covalent bonds, though detecting molecules bonded in this way is expected to be difficult. The highly magnetized white dwarf in the binary system AR Scorpii was identified in 2016 as the first pulsar in which the compact object is a white dwarf instead of a neutron star. A second white dwarf pulsar was discovered in 2023. Variability Early calculations suggested that there might be white dwarfs whose luminosity varied with a period of around 10 seconds, but searches in the 1960s failed to observe this.: §7.1.1 The first variable white dwarf found was HL Tau 76; in 1965 and 1966, and was observed to vary with a period of approximately 12.5 minutes. The reason for this period being longer than predicted is that the variability of HL Tau 76, like that of the other pulsating variable white dwarfs known, arises from non-radial gravity wave pulsations.: §7 Known types of pulsating white dwarf include the DAV, or ZZ Ceti, stars, including HL Tau 76, with hydrogen-dominated atmospheres and the spectral type DA;: 891, 895 DBV, or V777 Her, stars, with helium-dominated atmospheres and the spectral type DB;: 3525 and GW Vir stars, sometimes subdivided into DOV and PNNV stars, with atmospheres dominated by helium, carbon, and oxygen. GW Vir stars are not, strictly speaking, white dwarfs, but are stars that are in a position on the Hertzsprung–Russell diagram between the asymptotic giant branch and the white dwarf region. They may be called pre-white dwarfs. These variables all exhibit small (1%–30%) variations in light output, arising from a superposition of vibrational modes with periods of hundreds to thousands of seconds. Observation of these variations gives asteroseismological evidence about the interiors of white dwarfs. Formation After the hydrogen-fusing period of a main-sequence star of low or intermediate mass ends, such a star will expand to a red giant and fuse helium to carbon and oxygen in its core by the triple-alpha process. If a red giant has insufficient mass to generate the core temperatures required to fuse carbon (around 109 K), an inert mass of carbon and oxygen will build up at its center. After such a star sheds its outer layers and forms a planetary nebula, it will leave behind a core, which is the remnant white dwarf. White dwarf stars with less than 25% of a solar mass are all found in binary star systems. The proportion of white dwarfs in binary systems declines to 34% for masses in the range 0.5–0.75 M☉. These objects all have helium cores. It is thought that, over a lifespan that considerably exceeds the age of the universe (c. 13.8 billion years), such a star will eventually burn all its hydrogen, for a while becoming a blue dwarf, and end its evolution as a helium white dwarf composed chiefly of helium-4 nuclei. Due to the very long time this process takes, it is not thought to be the origin of the observed helium white dwarfs. Rather, they are believed to be mostly the product of mass loss in binary systems. Proposals to explain those helium white dwarfs that are not part of binary systems include mass loss due to a large exoplanetary companion, stars being stripped of material by companions exploding as supernovae, and various types of stellar mergers. If the mass of a main-sequence star is between 0.5 and 8 M☉, its core will become sufficiently hot to fuse helium into carbon and oxygen via the triple-alpha process, but it will never become sufficiently hot to fuse neon. Near the end of the period in which it undergoes fusion reactions, such a star will have a carbon–oxygen or oxygen-neon core that does not undergo fusion reactions, surrounded by an inner helium-burning shell and an outer hydrogen-burning shell. On the Hertzsprung–Russell diagram, it will be found on the asymptotic giant branch. It will then expel most of its outer material to form a planetary nebula, leaving only the carbon–oxygen core. White dwarfs with a mass greater than 1.05 M☉ are termed ultramassive white dwarfs. When formed in single-star systems, these are expected to have an oxygen-neon core. However, a significant fraction (~20%) of ultramassive white dwarfs are formed through white dwarf mergers. In this case the result is a carbon-oxygen ultramassive white dwarf. If a star is massive enough, its core will eventually become sufficiently hot to fuse carbon to neon, and then to fuse neon to iron. Such a star will not become a white dwarf, because the mass of its central, non-fusing core, initially supported by electron degeneracy pressure, will eventually exceed the largest possible mass supportable by degeneracy pressure. At this point the core of the star will collapse and it will explode in a core-collapse supernova that will leave behind a remnant neutron star, black hole, or possibly a more exotic form of compact star. Some main-sequence stars, of perhaps 8 to 10 M☉, although sufficiently massive to fuse carbon to neon and magnesium, may be insufficiently massive to fuse neon. Such a star may leave a remnant white dwarf composed chiefly of oxygen, neon, and magnesium, provided that its core does not collapse, and provided that fusion does not proceed so violently as to blow apart the star in a supernova. Although a few white dwarfs have been identified that may be of this type, most evidence for the existence of such comes from the novae called ONeMg or neon novae. The spectra of these novae exhibit abundances of neon, magnesium, and other intermediate-mass elements that appear to be only explicable by the accretion of material onto an oxygen–neon–magnesium white dwarf. Type Iax supernovae, that involve helium accretion by a white dwarf, have been proposed to be a channel for transformation of this type of stellar remnant. In this scenario, the carbon detonation produced in a Type Ia supernova is too weak to destroy the white dwarf, expelling just a small part of its mass as ejecta, but produces an asymmetric explosion that kicks the star, often known as a zombie star, to the high speeds of a hypervelocity star. The matter processed in the failed detonation is re-accreted by the white dwarf with the heaviest elements such as iron falling to its core where it accumulates. These iron-core white dwarfs would be smaller than the carbon–oxygen kind of similar mass and would cool and crystallize faster than those. Fate Once formed, a white dwarf is stable and will usually continue to cool almost indefinitely, eventually to become a black dwarf. Assuming that the universe continues to expand, it is thought that in 1019 to 1020 years, the galaxies will evaporate as their stars escape into intergalactic space.: §IIIA White dwarfs should generally survive galactic dispersion, although an occasional collision between white dwarfs may produce a new fusing star (e.g. an extreme helium star) or a super-Chandrasekhar mass white dwarf that will explode in a Type Ia supernova.: §§IIIC, IV The lifetime of a white dwarf is thought to be on the order of the hypothetical lifetime of the proton, known to be at least 1034–1035 years. Some grand unified theories predict a proton lifetime between 1030 and 1036 years. If these theories are not valid, the proton might still decay by complicated nuclear reactions or through quantum gravitational processes involving virtual black holes; in these cases, the lifetime is estimated to be no more than 10200 years. If protons do decay, the mass of a white dwarf will decrease very slowly with time as its nuclei decay, until it loses enough mass to become a non-degenerate lump of matter, and finally disappears completely.: §IV A white dwarf can also be cannibalized or evaporated by a companion star, causing the white dwarf to lose so much mass that it becomes a planetary mass object. The resultant object, orbiting the former companion, now host star, could be a helium planet or diamond planet. Debris disks and planets A white dwarf's stellar and planetary system is inherited from its progenitor star and may interact with the white dwarf in various ways. There are several indications that a white dwarf has a remnant planetary system. The most common observable evidence of a remnant planetary system is pollution of the spectrum of a white dwarf with metal absorption lines. 27–50% of white dwarfs show a spectrum polluted with metals, but these heavy elements settle out in the atmosphere of white dwarfs colder than 20000 K. The most widely accepted hypothesis is that this pollution comes from tidally disrupted rocky bodies. The first observation of a metal-polluted white dwarf was by van Maanen in 1917 at the Mount Wilson Observatory and is now recognized as the first evidence of exoplanets in astronomy. The white dwarf van Maanen 2 shows iron, calcium and magnesium in its atmosphere, but van Maanen misclassified it as the faintest F-type star based on the calcium H- and K-lines. The nitrogen in white dwarfs is thought to come from nitrogen-ice of extrasolar Kuiper Belt objects, the lithium is thought to come from accreted crust material and the beryllium is thought to come from exomoons. A less common observable evidence is infrared excess due to a flat and optically thick debris disk, which is found in around 1%–4% of white dwarfs. The first white dwarf with infrared excess was discovered by Zuckerman and Becklin in 1987 in the near-infrared around Giclas 29-38 and later confirmed as a debris disk. White dwarfs hotter than 27000 K sublimate all the dust formed by tidally disrupting a rocky body, preventing the formation of a debris disk. In colder white dwarfs, a rocky body might be tidally disrupted near the Roche radius and forced into a circular orbit by the Poynting–Robertson drag, which is stronger for less massive white dwarfs. The Poynting–Robertson drag will also cause the dust to orbit closer and closer towards the white dwarf, until it will eventually sublimate and the disk will disappear. A debris disk will have a lifetime of around a few million years for white dwarfs hotter than 10000 K. Colder white dwarfs can have disk-lifetimes of a few 10 million years, which is enough time to tidally disrupt a second rocky body and forming a second disk around a white dwarf, such as the two rings around LSPM J0207+3331. The least common observable evidence of planetary systems are detected major or minor planets. Only a handful of giant planets and a handful of minor planets are known around white dwarfs. Some estimations based on the metal content of the atmospheres of the white dwarfs consider that at least 15% of them may be orbited by planets or asteroids, or at least their debris. Another suggested idea is that white dwarfs could be orbited by the stripped cores of rocky planets, that would have survived the red giant phase of their star but losing their outer layers and, given those planetary remnants would likely be made of metals, to attempt to detect them looking for the signatures of their interaction with the white dwarf's magnetic field. Other suggested ideas of how white dwarfs are polluted with dust involve the scattering of asteroids by planets or via planet-planet scattering. Liberation of exomoons from their host planet could cause white dwarf pollution with dust. Either the liberation could cause asteroids to be scattered towards the white dwarf or the exomoon could be scattered into the Roche radius of the white dwarf. The mechanism behind the pollution of white dwarfs in binaries was also explored as these systems are more likely to lack a major planet, but this idea cannot explain the presence of dust around single white dwarfs. While old white dwarfs show evidence of dust accretion, white dwarfs older than ~1 billion years or >7000 K with dusty infrared excess were not detected until the discovery of LSPM J0207+3331 in 2018, which has a cooling age of ~3 billion years. The white dwarf shows two dusty components that are being explained with two rings with different temperatures. Another possible way to detect planetary systems around white dwarfs is through their radio emissions. In 2004 and 2005, A. J. Willes and K. Wu hypothesized that when an exoplanet travels through the magnetosphere of a white dwarf, it may generate auroral radio emissions from the magnetic poles of the white dwarf, similar to how Io stimulates radio emissions from Jupiter; a search for such radio emission from nine white dwarfs by researchers using the Arecibo radio telescope did not find any so far. Infrared spectroscopic observations made by NASA's Spitzer Space Telescope of WD 2226-210, the central star of the Helix Nebula, suggest the presence of a dust cloud, which may be caused by cometary collisions. It is possible that infalling material from this may cause X-ray emission from the central star. Similarly, observations made in 2004 indicated the presence of a dust cloud around the young (estimated to have formed from its AGB progenitor about 500 million years ago) white dwarf G29-38, which may have been created by tidal disruption of a comet passing close to the white dwarf. The metal-rich white dwarf WD 1145+017 is the first white dwarf observed with a disintegrating minor planet that transits the star. The disintegration of the planetesimal generates a debris cloud that passes in front of the star every 4.5 hours, causing a 5-minute-long fade in the star's optical brightness. The depth of the transit is highly variable. The giant planet WD J0914+1914b is first gas planet orbiting around a white dwarf and is being evaporated by the strong ultraviolet radiation of the hot white dwarf. Part of the evaporated material is being accreted in a gaseous disk around the white dwarf. The weak hydrogen line as well as other lines in the spectrum of the white dwarf revealed the presence of the giant planet. The white dwarf WD 0145+234 shows brightening in the mid-infrared, seen in NEOWISE data. The brightening, not seen before 2018, may be due to the tidal disruption of an exoasteroid, the first time such an event has been observed. WD 1856+534 is the first transiting major planet to be observed orbiting a white dwarf, and remains the only such example as of 2023. MOA-2010-BLG-477L, a white dwarf discovered thanks to a microlensing event, is also known to have a giant planet. GD 140 and LAWD 37 are suspected to have giant exoplanets due to anomaly in the Hipparcos-Gaia proper motion. For GD 140 it is suspected to be a planet several times more massive than Jupiter and for LAWD 37 it is suspected to be a planet less massive than Jupiter. Additionally, WD 0141-675 was suspected to have a super-Jupiter with an orbital period of 33.65 days based on Gaia astrometry. This is remarkable because WD 0141-675 is polluted with metals and metal polluted white dwarfs have long been suspected to host giant planets that disturb the orbits of minor planets, causing the pollution. Both GD 140 and WD 0141 will be observed with JWST in cycle 2 with the aim to detect infrared excess caused by the planets. The planet candidate at WD 0141-675 was found to be a false positive caused by a software error. Habitability A search has been proposed for transits of hypothetical Earth-like planets around white dwarfs with surface temperatures of less than 10000 K. Such stars that could harbor a habitable zone at a distance of c. 0.005 to 0.02 AU that would last upwards of 3 billion years. This is so close that any habitable planets would be tidally locked. As a white dwarf has a size similar to that of a planet, these kinds of transits would produce strong eclipses. Newer research casts some doubts on this idea, given that the close orbits of those hypothetical planets around their parent stars would subject them to strong tidal forces that could render them uninhabitable by triggering a greenhouse effect. Another suggested constraint to this idea is the origin of those planets. Leaving aside formation from the accretion disk surrounding the white dwarf, there are two ways a planet could end in a close orbit around stars of this kind: by surviving being engulfed by the star during its red giant phase, and then spiralling inward, or inward migration after the white dwarf has formed. The former case is implausible for low-mass bodies, as they are unlikely to survive being absorbed by their stars. In the latter case, the planets would have to expel so much orbital energy as heat, through tidal interactions with the white dwarf, that they would likely end as uninhabitable embers. Binary stars and novae If a white dwarf is in a binary star system and is accreting matter from its companion, a variety of phenomena may occur, including novae and Type Ia supernovae. It may also be a super-soft x-ray source if it is able to take material from its companion fast enough to sustain fusion on its surface. On the other hand, phenomena in binary systems such as tidal interaction and star–disc interaction, moderated by magnetic fields or not, act on the rotation of accreting white dwarfs. In fact, the (securely known) fastest-spinning white dwarfs are members of binary systems (the fastest one being the white dwarf in CTCV J2056-3014). A close binary system of two white dwarfs can lose angular momentum and radiate energy in the form of gravitational waves, causing their mutual orbit to steadily shrink until the stars merge. The mass of an isolated, nonrotating white dwarf cannot exceed the Chandrasekhar limit of ~ 1.4 M☉. This limit may increase if the white dwarf is rotating rapidly and nonuniformly. White dwarfs in binary systems can accrete material from a companion star, increasing both their mass and their density. As their mass approaches the Chandrasekhar limit, this could theoretically lead to either the explosive ignition of fusion in the white dwarf or its collapse into a neutron star. There are two models that might explain the progenitor systems of Type Ia supernovae: the single-degenerate model and the double-degenerate model. In the single-degenerate model, a carbon–oxygen white dwarf accretes mass and compresses its core by pulling mass from a companion non-degenerate star.: 14 It is believed that compressional heating of the core leads to ignition of carbon fusion as the mass approaches the Chandrasekhar limit. Because the white dwarf is supported against gravity by quantum degeneracy pressure instead of by thermal pressure, adding heat to the star's interior increases its temperature but not its pressure, so the white dwarf does not expand and cool in response. Rather, the increased temperature accelerates the rate of the fusion reaction, in a runaway process that feeds on itself. The thermonuclear flame consumes much of the white dwarf in a few seconds, causing a Type Ia supernova explosion that obliterates the star. In another possible mechanism for Type Ia supernovae, the double-degenerate model, two carbon–oxygen white dwarfs in a binary system merge, creating an object with mass greater than the Chandrasekhar limit in which carbon fusion is then ignited.: 14 In both cases, the white dwarfs are not expected to survive the Type Ia supernova. The single-degenerate model was the favored mechanism for Type Ia supernovae, but now, because of observations, the double-degenerate model is thought to be the more likely scenario. Predicted rates of white dwarf-white dwarf mergers are comparable to the rate of Type Ia supernovae and would explain the lack of hydrogen in the spectra of Type Ia supernovae. The main mechanism for Type Ia supernovae remains an open question. In the single-degenerate scenario, the accretion rate onto the white dwarf needs to be within a narrow range dependent on its mass so that the hydrogen burning on the surface of the white dwarf is stable. If the accretion rate is too low, novae on the surface of the white dwarf will blow away accreted material. If it is too high, the white dwarf will expand and the white dwarf and companion star will be in a common envelope. This stops the growth of the white dwarf thus preventing it from reaching the Chandrasekhar limit and exploding. For the single-degenerate model its companion is expected to survive, but there is no strong evidence of such a star near Type Ia supernovae sites. In the double-degenerate scenario, white dwarfs need to be in very close binaries; otherwise their inspiral time is longer than the age of the universe. It is also likely that instead of a Type Ia supernova, the merger of two white dwarfs will lead to core-collapse. As a white dwarf accretes material quickly, the core can ignite off-center, which leads to gravitational instabilities that could create a neutron star. The historical bright SN 1006 is thought to have been a Type Ia supernova from a white dwarf, possibly the merger of two white dwarfs. Tycho's Supernova of 1572 was also a type Ia supernova, and its remnant has been detected. WD 0810–353, a white dwarf 11 parsecs away from the Sun, is possibly a hypervelocity runaway ejected from a Type Ia supernova, though this has been disputed. A post-common envelope binary (PCEB) is a binary consisting of a white dwarf or hot subdwarf and a closely tidally-locked red dwarf (in other cases this might be a brown dwarf instead of a red dwarf). These binaries form when the red dwarf is engulfed in the red giant phase. As the red dwarf orbits inside the common envelope, it is slowed down in the denser environment. This slowed orbital speed is compensated with a decrease of the orbital distance between the red dwarf and the core of the red giant. The red dwarf spirals inwards towards the core and might merge with the core. If this does not happen and instead the common envelope is ejected, then the binary ends up in a close orbit, consisting of a white dwarf and a red dwarf. This type of binary is called a post-common envelope binary. The evolution of the PCEB continues as the two dwarf stars orbit closer and closer due to magnetic braking and by releasing gravitational waves. The binary might then evolve into one of several dramatic outcomes: a high-field magnetic white dwarf, a white dwarf pulsar, a double-degenerate binary, or even a Type Ia supernova. Because a PCEB may evolve at some point into a cataclysmic variable, some of them are also called pre-cataclysmic variables. Before accretion of material pushes a white dwarf close to the Chandrasekhar limit, accreted hydrogen-rich material on the surface may ignite in a less destructive type of thermonuclear explosion powered by hydrogen fusion. These surface explosions can be repeated as long as the white dwarf's core remains intact. This weaker kind of repetitive cataclysmic phenomenon is called a (classical) nova. Astronomers have also observed dwarf novae, which have smaller, more frequent luminosity peaks than the classical novae. These are thought to be caused by the release of gravitational potential energy when part of the accretion disc collapses onto the star, rather than through a release of energy due to fusion. In general, binary systems with a white dwarf accreting matter from a stellar companion are called cataclysmic variables. As well as novae and dwarf novae, several other classes of these variables are known, including polars and intermediate polars, both of which feature highly magnetic white dwarfs. Both fusion- and accretion-powered cataclysmic variables have been observed to be X-ray sources. Other binaries include those that consist of a main sequence star (or giant) and a white dwarf. The binary Sirius AB is an example pair of this type. White dwarfs can also exist as binaries or multiple star systems that only consist of white dwarfs. An example of a resolved triple white dwarf system is WD J1953−1019, discovered with Gaia DR2 data. One interesting field is the study of remnant planetary systems around white dwarfs. It is expected that planets orbiting several AU from a star will survive the star's post-main-sequence transformation into a white dwarf. Moreover, white dwarfs, being much smaller and correspondingly less luminous than their progenitors, are less likely to outshine any bodies in orbit around them. This makes white dwarfs advantageous targets for direct-imaging searches for exoplanets and brown dwarfs. The first brown dwarf to be detected by direct imaging was the companion to the white dwarf GD 165 A, discovered in 1988. More recently, the white dwarf WD 0806−661 was found to have a cold companion body of substellar mass, variously described as a brown dwarf or an exoplanet. Nearest white dwarfs See also References Further reading External links |
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DEV Community Aaron Rose Software engineer and technology writer at tech-reader.blog You're a dedicated community champion! Keep up the great work by posting at least 2 comments per week for 16 straight weeks. The prized 24-week badge is within reach! Consistency pays off! Be an active part of our community by posting at least 2 comments per week for 8 straight weeks. Earn the 16 Week Badge next. Awarded to the top JavaScript author each week Awarded for having a post featured in the weekly "must-reads" list. 🙌 Awarded to the top Go author each week Awarded to the top Python author each week Keep contributing to discussions by posting at least 2 comments per week for 4 straight weeks. Unlock the 8 Week Badge next. Keep the community conversation going! Post at least 2 comments for 2 straight weeks and unlock the 4 Week Badge. For actively engaging with the community by posting at least 2 comments in a single week. 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DEV Community Aaron Rose Software engineer and technology writer at tech-reader.blog You're a dedicated community champion! Keep up the great work by posting at least 2 comments per week for 16 straight weeks. The prized 24-week badge is within reach! Consistency pays off! Be an active part of our community by posting at least 2 comments per week for 8 straight weeks. Earn the 16 Week Badge next. Awarded to the top JavaScript author each week Awarded for having a post featured in the weekly "must-reads" list. 🙌 Awarded to the top Go author each week Awarded to the top Python author each week Keep contributing to discussions by posting at least 2 comments per week for 4 straight weeks. Unlock the 8 Week Badge next. Keep the community conversation going! Post at least 2 comments for 2 straight weeks and unlock the 4 Week Badge. For actively engaging with the community by posting at least 2 comments in a single week. 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Contents Judea Judea or Judaea (/dʒuːˈdiːə, dʒuːˈdeɪə/; Hebrew: יהודה, Modern: Yəhūda, Tiberian: Yehūḏā; Arabic: يهودا, Yahūdā; Greek: Ἰουδαία, Ioudaía; Latin: Iudaea) is a mountainous region of the Levant. Traditionally dominated by the city of Jerusalem, it is now part of Israel and the West Bank. The name is derived from the Hebrew name Yehudah, and was used during the Babylonian, Persian, Hellenistic, and Roman periods. Under the Hasmoneans, the Herodians, and the Romans, the term was applied to an area larger than the Judea of earlier periods. In the aftermath of the Bar Kokhba revolt (c. 132–136 CE), the Roman province of Judaea was renamed Syria Palaestina. The term Judea was used by English speakers for the hilly internal part of Mandatory Palestine. Judea roughly corresponds to the southern part of the West Bank (Arabic: الضِفَّة الغَرْبِيَّة, romanized: aḍ-ḍiffa al-gharbiya), a territory Israel has occupied since 1967 and administered as the "Judea and Samaria Area"(מחוז יהודה ושומרון, Makhoz Yehuda VeShomron). Usage of the term "Judea and Samaria" is associated with the right wing in Israeli politics. Etymology The name Judea is a Greek and Roman adaptation of the Hebrew name Yehudah (Hebrew יהודה), one of the Twelve Tribes of Israel[citation needed] and later used as the name for the ancient Kingdom of Judah. Nimrud Tablet K.3751, dated c. 733 BCE, is the earliest known extra-biblical record of the name Judah (written in Assyrian cuneiform as Yaudaya or KUR.ia-ú-da-a-a). Related nomenclature continued to be used under the rule of the Babylonians (the Yehud province), the Persians (the Yehud province), during the Hellenistic period (Hasmonean Judea), and under the Romans (Provincia Iudaea, or Province of Judaea). There is no consensus among linguists and historians as to the origins of the name Judah (Yehudah). The Book of Genesis presents a folk etymology deriving it from a legendary founder Judah, the son of Jacob, offering a wordplay This etymology is generally regarded as dubious by modern scholars because of its strong similarity to other eponymic legends from antiquity that were later proven to be false, and because Judah does not appear as a given name until late in the post-Exilic period. Several scholars have suggested Judah may be a theophoric name referencing the tetragrammaton (y-h-w), a shortening of Yehuda-el ("praise be to El"), or an otherwise-unattested god y-h-w-d. However, there is little to no agreement on the specifics of such an origin, and these theories have fallen out of favor. A more likely explanation suggests Yehuda is cognate with the Arabic wahda ("ravine" or "gorge"), though such a term is not directly attested in the Old Testament. Judea was sometimes used as the name for the entire region, including parts beyond the river Jordan. In 200 CE Sextus Julius Africanus, cited by Eusebius (Church History 1.7.14), described "Nazara" (Nazareth) as a village in Judea. The King James Version of the Bible refers to the region as "Jewry". 'Judean' was not exclusively used as ethnic identifier; Ptolemy of Ascalon, for example, quoted in a work by Ammonius of Alexandria, distinguishes between Judeans originating within the land of Judea, "and forcefully circumcised Idumeans (of Syrian or Phoenician origin, in his view) who could likewise be designated 'Judeans.'" Under the Hasmoneans, the Herodians, and the Romans, the term was applied to an area larger than the Judea of earlier periods. In the aftermath of the Bar Kokhba revolt (c. 132–136 CE), the Roman province of Judaea was renamed Syria Palaestina. 'Judea' was a name used by English speakers for the hilly internal part of Mandatory Palestine until the Jordanian rule of the area in 1948. For example, the borders of the two states to be established according to the UN's 1947 partition scheme were officially described using the terms 'Judea' and 'Samaria' and in its reports to the League of Nations Mandatory Committee, as in 1937, the geographical terms employed were 'Samaria and Judea.' Jordan called the area aḍ-ḍiffa al-gharbiya (الضِفَّة الغَرْبِيَّة translated into English as 'the West Bank'). 'Yehuda' (יהודה) is the Hebrew term used for the area in modern Israel since the region was captured and occupied by Israel in the 1967 Six Day War. According to Britannica, referring to this region as 'Judea and Samaria' (יהודה ושומרון, Yehuda VeShomron) has been associated with the right wing in Israeli politics, which does not support a two state solution to the Israeli–Palestinian conflict. The term 'West Bank' is what appears on international treaties such as the Oslo Accords established between the Palestine Liberation Organization and the Israeli government. The names "West Bank" (הַגָּדָה הַמַּעֲרָבִית, HaGadah HaMaʽaravit) or, alternatively, "the Territories" (השטחים, HaShtahim) are also current in Israeli usage. Generally, preference for one term over the other indicates the speaker's position on the Israeli political spectrum. Historical boundaries The first century Roman-Jewish historian Josephus wrote (The Jewish War 3.3.5): In the limits of Samaria and Judea lies the village Anuath, which is also named Borceos. This is the northern boundary of Judea. The southern parts of Judea, if they be measured lengthways, are bounded by a village adjoining to the confines of Arabia; the Jews that dwell there call it Jordan. However, its breadth is extended from the river Jordan to Joppa. The city Jerusalem is situated in the very middle; on which account some have, with sagacity enough, called that city the Navel of the country. Nor indeed is Judea destitute of such delights as come from the sea, since its maritime places extend as far as Ptolemais: it was parted into eleven portions, of which the royal city Jerusalem was the supreme, and presided over all the neighboring country, as the head does over the body. As to the other cities that were inferior to it, they presided over their several toparchies; Gophna was the second of those cities, and next to that Acrabatta, after them Thamna, and Lydda, and Emmaus, and Pella, and Idumea, and Engaddi, and Herodium, and Jericho; and after them came Jamnia and Joppa, as presiding over the neighboring people; and besides these there was the region of Gamala, and Gaulonitis, and Batanea, and Trachonitis, which are also parts of the kingdom of Agrippa. This [last] country begins at Mount Libanus, and the fountains of Jordan, and reaches breadthways to Lake Tiberias; and in length is extended from a village called Arpha, as far as Julias. Its inhabitants are a mixture of Jews and Syrians. And thus have I, with all possible brevity, described the country of Judea, and those that lie round about it. Elsewhere, Josephus wrote that "Arabia is a country that borders on Judea." The first century Roman historian Tacitus defined Judaea as bordered by Arabia to the east, Egypt to the south, Phoenicia and the Mediterranean Sea to the west, and Syria to the north. His conception, presented in Histories 5.6, mirrors a conventional understanding of Judaea as the territory where Jews predominated from the Hasmonaean era onward, standing apart from the provincial borders of the province of Judaea in his own period. Geography Judea is a mountainous region, part of which is considered a desert. It varies greatly in height, rising to an altitude of 1,020 metres (3,350 ft) in the south at the Hebron Hills, 30 km (19 mi) southwest of Jerusalem, and descending to as much as 400 metres (1,300 ft) below sea level in the east of the region. It also varies in rainfall, starting with about 400–500 millimetres (16–20 in) in the western hills, rising to 600 millimetres (24 in) around western Jerusalem (in central Judea), falling back to 400 millimetres (16 in) in eastern Jerusalem and dropping to around 100 millimetres (3.9 in) in the eastern parts, due to a rain shadow: this is the Judaean Desert. The climate, accordingly, moves between Mediterranean in the west and desert climate in the east, with a strip of semi-arid climate in the middle. Major urban areas in the region include Jerusalem, Bethlehem, Gush Etzion, Jericho and Hebron. Geographers divide Judea into several regions: the Hebron hills, the Jerusalem saddle, the Bethel hills and the Judaean Desert east of Jerusalem, which descends in a series of steps to the Dead Sea. The hills are distinct for their anticline structure. In ancient times the hills were forested, and the Bible records agriculture and sheep farming being practiced in the area. Animals are still grazed today, with shepherds moving them between the low ground to the hilltops as summer approaches, while the slopes are still layered with centuries-old stone terracing. The Jewish Revolt against the Romans ended in the devastation of vast areas of the Judean countryside. Mount Hazor marks the geographical boundary between Samaria to its north and Judea to its south. History According to the biblical story of the Patriarchs, Abraham came to the Land of Canaan as commanded by God and moved around in the hill country (Judaea and Samaria) and the Negev. The country is described as populated by Canaanites, Hittites, Jebusites and other population groups. This pattern continued with his son Isaac, his son Jacob and his 12 sons and daughter, Dina and their families. The Patriarchs Sarai, Abraham, Isaac, Rebecca and Jacob were buried at Hebron in the Tomb of the Patriarchs. according to Genesis and Exodus. After the Conquest of Joshua the Israelite tribes conquered and lived in most of the land west of the river Jordan and in the northern part east of that river for close to 400 years. The biblical account in the Books of Kings describes how King Saul and later King David and his son Solomon (Shlomo) succeeded in fighting the last remnants of non-Israelite populations and unified the tribes into one united monarchy. According to our[who?] understanding of the text as well as recent archeological findings, this was to a large degree possible through the Israelite adaption of Iron Age technologies. Scholarship has been divided as to the historical veracity of the existence and extension of a kingdom that unified Judea and Samaria, but archeological excavations of the last 30 years[when?] have time and again found solid evidence that confirms the bibilcal descriptions. Regardless, the Northern Kingdom was conquered by the Neo-Assyrian Empire in 720 BCE and parts of the population of the 10 northern tribes exiled. The northern Kingdom of Judah remained nominally independent, but paid tribute to the Assyrian Empire from 715 and throughout the first half of the 7th century BCE, regaining its independence as the Assyrian Empire declined after 640 BCE, but after 609 again fell under the sway of imperial rule, this time paying tribute at first to the Egyptians and after 601 BCE to the Neo-Babylonian Empire, until 586 BCE, when it was finally conquered by Babylonia, the temple in Jerusalem destroyed and many of the inhabitants of Judea exiled to Babylonia. The Babylonian Empire fell to the conquests of Cyrus the Great in 539 BCE. Judea remained under Persian rule until the conquest of Alexander the Great in 332 BCE, eventually falling under the rule of the Hellenistic Seleucid Empire until the revolt of Judas Maccabeus resulted in the Hasmonean dynasty of kings who ruled in Judea for over a century. Judea lost its independence to the Romans in the 1st century BCE, becoming first a tributary kingdom, then a province, of the Roman Empire. The Romans had allied themselves to the Maccabees and interfered in 63 BCE, at the end of the Third Mithridatic War, when the proconsul Pompey ("Pompey the Great") stayed behind to make the area secure for Rome, including his siege of Jerusalem in 63 BCE. Queen Salome Alexandra had recently died, and a civil war broke out between her sons, Hyrcanus II and Aristobulus II. Pompeius restored Hyrcanus, but political rule soon passed to the Herodian dynasty, who ruled as client kings. In 6 CE, Judea came under direct Roman rule as the southern part of the province of Judaea, although Jews living there still maintained some form of independence and could judge offenders by their own laws, including capital offences, until c. 28 CE. The Hashmonean kingdom, after Pompey's conquest, was divided in 57 BCE by Gabinius, the governor of Syria, into five administrative districts (synedria or toparchies), as mentioned by Josephus, later on the region of historical Judaea proper being further divided; the exact number of Judaean districts (in the end ten or eleven according to Josephus and Pliny) and their location is disputed, Schürer amending the ancient authors' list as follows: Jerusalem in the centre, later becoming the district of Orine ("Orine Judaea", 'mountainous [region of] Judaea'); Gophna, Akrabatta north of it; Thamna and Lydda to the northwest; Emmaus (possibly future Nicopolis/Imwas, although other towns in the region also bore that name) to the west; Bethleptepha (rather than Josephus' Pella) to the southwest; Idumaea to the south; Engaddi and Herodeion to the southeast; and Jericho to the east. Schürer dismisses Pliny's listing of "Jopica" (Joppa) and Josephus' of Pella, as these were, in his opinion, independent cities not included in Judaea proper. Other regions outside Judaea proper, which had belonged to the Hasmonean and Herodian kingdoms and came under Roman dominance and then direct rule, remained or became also split into districts with regional capitals, these being Galilee (with the capital at Sepphoris and later Tiberias), and Perea in Transjordan (with Amathus); however, a district administered from a certain Gadara is also mentioned, which can be in three different locations - either in Perea (at or near Al-Salt), in the Decapolis at Umm Qais, or - which is relevant for Judaea - at biblical Gezer in the foothills of the Judaean Mountains, mentioned by Josephus under a Hellenised form of its Semitic name, Gadara, edited to "Gazara" in the Loeb edition). In 66 CE, the Jewish population rose against Roman rule in a revolt that was unsuccessful. Jerusalem was besieged in 70 CE. The city was razed, the Second Temple was destroyed, and much of the population was killed or enslaved. In 132 CE, the Bar Kokhba revolt (132–136 CE) broke out. After an initial string of victories, rebel leader Simeon Bar Kokhba was able to form an independent Jewish state that lasted several years and included most of the district of Judea, including the Judean Mountains, the Judean Desert, and northern Negev desert, but probably not other sections of the country. When the Romans finally put an end to the uprising, most of the Jews in Judea were killed or displaced, and a sizable number of captives were sold into slavery, leaving the district mostly depopulated. Jews were expelled from the area surrounding Jerusalem. No village in the district of Judea whose remains have been excavated so far has not been destroyed during the revolt. Roman emperor Hadrian, determined to root out Jewish nationalism, changed the name of the province from Judaea to Syria Palaestina. The province's Jewish population was now mainly concentrated in Galilee, the coastal plain (especially in Lydda, Joppa, and Caesarea), and smaller Jewish communities continued to live in the Beit She'an Valley, the Carmel, and Judea's northern and southern frontiers, including the southern Hebron Hills and along the shores of the Dead Sea. The suppression of the Bar Kokhba revolt led to widespread destruction and displacement throughout Judea, and the district saw a decline in population. The Roman colony of Aelia Capitolina, which was built on the ruins of Jerusalem, remained a backwater for the duration of its existence. The villages around the city were depopulated, and arable lands in the region were confiscated by the Romans. Having no alternative population to fill the empty villages led the authorities to establish imperial or legionary estates and monasteries on confiscated village lands to benefit the elites and, later, the church. This also initiated a process of romanization that took place during the Late Roman period, with pagan populations penetrating the region and settling alongside Roman veterans. There was only a revival of village settlement on the eastern edges of Jerusalem's hinterland, on the transition between the arable highlands and the Judaean Desert. Those settlements grew on marginal lands with vague ownership and unenforced state land dominion. Judea's decline only came to an end in the fifth century CE, when it developed into a monastic center, and Jerusalem became a major Christian pilgrimage and ecclesiastical hub. Under Byzantine rule, the regional population, composed of pagan populations who had migrated there after Jews were driven out following the Bar Kokhba revolt, gradually converted to Christianity. The Byzantines redrew the borders of the land of Palestine. The various Roman provinces (Syria Palaestina, Samaria, Galilee, and Peraea) were reorganized into three dioceses of Palaestina, reverting to the name first used by Greek historian Herodotus in the mid-5th century BCE: Palaestina Prima, Secunda, and Tertia or Salutaris (First, Second, and Third Palestine), part of the Diocese of the East. Palaestina Prima consisted of Judea, Samaria, the Paralia, and Peraea with the governor residing in Caesarea. Palaestina Secunda consisted of Galilee, the lower Jezreel Valley, the regions east of Galilee, and the western part of the former Decapolis with the seat of government at Scythopolis. Palaestina Tertia included the Negev, southern Jordan—once part of Arabia—and most of Sinai, with Petra as the usual residence of the governor. Palestina Tertia was also known as Palaestina Salutaris. According to historian H.H. Ben-Sasson, this reorganisation took place under Diocletian (284–305), although other scholars suggest this change occurred later, in 390. The mostly French army of the First Crusade conquered Jerusalem from the Seljuks in 1099 and expanded the territory they held in the following years. According to Ellenblum, the Franks tended to settle in the southern half of the region between Jerusalem and Nablus since there was a sizable Christian population there. Most of the people living in the northern portion of Judea in the late 16th century were Muslims; some of them resided in towns that today have significant Christian populations. According to the 1596–1597 Ottoman census, Birzeit and Jifna, for instance, were wholly Muslim villages, while Taybeh had 63 Muslim families and 23 Christian families. There were 71 Christian families and 9 Muslim families in Ramallah, although the Christians there were recent arrivals who had moved from the Kerak area only a few years previously. According to Ehrlich, the region's Christian population decreased as a result of a combination of factors including impoverishment, oppression, marginalization, and persecution. Sufi activity took place in Jerusalem and the surrounding area, which most likely pushed Christian villagers in the region to convert to Islam. Timeline Selected towns and cities Judea, in the generic sense, also incorporates places in Galilee and in Samaria. See also References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Vela_(constellation)] | [TOKENS: 2466] |
Contents Vela (constellation) Vela is a constellation in the southern sky, which contains the Vela Supercluster. Its name is Latin for the sails of a ship, and it was originally part of a larger constellation, the ship Argo Navis, which was later divided into three parts, the others being Carina and Puppis. With an apparent magnitude of 1.8, its brightest star is the hot blue multiple star Gamma Velorum, one component of which is the closest and brightest Wolf-Rayet star in the sky. Delta and Kappa Velorum, together with Epsilon and Iota Carinae, form the asterism known as the False Cross. 1.95-magnitude Delta is actually a triple or quintuple star system. History Argo Navis was one of the 48 classical constellations listed by the 2nd-century astronomer Ptolemy, and represented the ship Argo, used by Jason and the Argonauts on their quest for the Golden Fleece in Greek mythology. German cartographer Johann Bayer depicted the constellation on his Uranometria of 1603, and gave the stars Bayer designations from Alpha to Omega. However, his chart was inaccurate as the constellation was not fully visible from the Northern Hemisphere. Argo was more accurately charted and subdivided in 1752 by the French astronomer Nicolas Louis de Lacaille, forming Carina (the keel), Vela (the sails), and Puppis (the poop deck). Despite the division, Lacaille kept Argo's Bayer designations. Therefore, Carina has the Alpha, Beta and Epsilon originally assigned to Argo Navis, while Vela's brightest stars are Gamma and Delta, Puppis has Zeta as its brightest star, and so on. Characteristics Vela is bordered by Antlia and Pyxis to the north, Puppis to the northwest, Carina to the south and southwest, and Centaurus to the east. Covering 500 square degrees, it ranks 32nd of the 88 modern constellations in size. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is "Vel". The official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of 14 segments. In the equatorial coordinate system, the right ascension coordinates of these borders lie between 08h 13.3m and 11h 05.5m , while the declination coordinates are between −37.16° and −57.17°. Features The brightest star in the constellation, Gamma Velorum, is a complex multiple star system. The brighter component, known as Gamma2 Velorum, shines as a blue-white star of apparent magnitude 1.83. It is a spectroscopic binary made up of two very hot blue stars orbiting each other every 78.5 days and separated by somewhere between 0.8 and 1.6 Astronomical Units (AU). The brighter component is a hot blue main-sequence star of spectral type O7.5 and is around 280,000 times as luminous, is around 30 times as massive and is 17 times the diameter of the Sun with a surface temperature of 35,000 K. The second component is an extremely rare example of hot star known as a Wolf–Rayet star, and is the closest and brightest example in the sky. It has a surface temperature of 57,000 and is around 170,000 times as luminous as the Sun, though it radiates most of its energy in the ultraviolet spectrum. Gamma1 is a blue-white star of spectral type B2III and apparent magnitude 4.3. The two pairs are separated by 41 arcseconds, easily separable in binoculars. Parallax measurements give a distance of 1,116 light-years, meaning that they are at least 12,000 AU apart. Further afield are 7.3-magnitude Gamma Velorum C and 9.4-magnitude Gamma Velorum D, lying 62 and 93 arcseconds south-southeast from Gamma2. These stars are the most prominent members of Vela OB2, an extended association of young stars. The next brightest star is Delta Velorum or Alsephina, also a multiple star system and one of the brightest eclipsing binaries in the sky. Together with Kappa Velorum or Markeb, Iota Carinae or Aspidiske and Epsilon Carinae or Avior, it forms the diamond-shaped asterism known as the False Cross—so called because it is sometimes mistaken for the Southern Cross, causing errors in astronavigation. Appearing as a white star of magnitude 1.95, Delta is actually a triple or possibly quintuple star system located around 80 light-years from the Solar System. Delta A has a magnitude of 1.99 and is an eclipsing binary composed of two A-type white stars (Delta Aa and Ab) which orbit each other every 45.2 days and lie 0.5 AU from each other, with a resulting drop in magnitude of 0.4 when the dimmer one passes.in front of the brighter. Delta B is a 5.1 magnitude yellow G-class star of similar dimensions to the Sun which ranges between 26 and 72 AU away from the brighter pair, taking 142 years to complete a revolution. Further out still, at a distance of 1700 AU, are two red dwarfs of magnitudes 11 and 13. If they are part of the multiple system, they take 28000 years to complete an orbit. Also called Markeb, Kappa appears as a blue-white star of spectral type B2IV-V and magnitude 2.47 but is in fact a spectroscopic binary. The two orbit around each other with a period of 116.65 days, but the size, mass and nature of the companion are as yet unclear. The orange-hued Lambda Velorum, or Suhail, is the third-brightest star in the constellation. A supergiant of spectral type K4Ib-II, it varies between magnitudes 2.14 and 2.3, and lies 545 light-years distant. It has around 11,000 times the luminosity, 9 to 12 times the mass and 207 times the diameter of the Sun. AH Velorum is a Cepheid variable located less than a degree to the northeast of Gamma. A yellow-white supergiant of spectral type F7Ib-II, it pulsates between magnitudes 5.5 and 5.89 over 4.2 days. Also lying close to Gamma, V Velorum is a Cepheid of spectral type F6-F9II ranging from magnitude 7.2 to 7.9 over 4.4 days. AI Velorum is located 2.8 degrees north-northeast of Gamma, a Delta Scuti variable of spectral type A2p-F2pIV/V that ranges between magnitudes 6.15 and 6.76 in around 2.7 hours. V390 Velorum is an aged star that has been found to be surrounded by a dusty disk. An RV Tauri variable, it has a spectral type of F3e and ranges between magnitudes 9.01 and 9.27 over nearly 95 days. Omicron Velorum is a blue-white subgiant of spectral type B3III-IV located around 495 light-years from the Solar System. A slowly pulsating B star, it ranges between magnitudes 3.57 and 3.63 over 2.8 days. It is the brightest star in, and gives its name to, the Omicron Velorum Cluster, also known as IC 2391, an open cluster located around 500 light-years away. Seven star systems have been found to have planets. HD 75289 is a Sun-like star of spectral type G0V with a hot Jupiter planetary companion that takes only about 3.51 days to revolve at an orbital distance of 0.0482 AU. WASP-19 is a star of apparent magnitude 12.3 located 815 light-years away, which has a hot Jupiter-like planet that orbits every 0.7 days. HD 73526 is a Sun-like star of spectral type G6V that has two planets around double the mass of Jupiter each with orbits of 187 and 377 days, respectively. HD 85390 is an orange dwarf of spectral type K1.5V lying around 111 light-years distant with a planet 42 times as massive as Earth orbiting every 788 days. HD 93385 is a Sun-like star of spectral type G2/G3V located around 138 light-years away that is orbited by two super-Earths with periods of 13 and 46 days and masses 8.3 and 10.1 times that of Earth, respectively. The discovery of a binary brown dwarf system named Luhman 16 only 6.6 light-years away, the third-closest system to the Solar System, was announced on 11 March 2013. Of the deep-sky objects of interest in Vela is a planetary nebula known as NGC 3132, nicknamed the 'Eight-Burst Nebula' or 'Southern Ring Nebula' (see accompanying photo). It lies on the border of the constellation with Antlia. NGC 2899 is an unusual red-hued example. This constellation has 32 more planetary nebulae. The Gum Nebula is a faint emission nebula, believed to be the remains of a million-year-old supernova. Within it lies the smaller and younger Vela Supernova Remnant. This is the nebula of a supernova explosion that is believed to have been visible from Earth around 10,000 years ago. The remnant contains the Vela Pulsar, the first pulsar to be identified optically. Nearby is NGC 2736, also known as the Pencil Nebula. HH-47 is a Herbig-Haro Object, a young star around 1,400 light-years from the Sun that is ejecting material at tremendous speed (up to a million kilometres per hour) into its surrounds. This material glows as it hits surrounding gas. NGC 2670 is an open cluster located in Vela. It has an overall magnitude of 7.8 and is 3,200 light-years from Earth. The stars of NGC 2670, a Trumpler class II 2 p and Shapley class-d cluster, are in a conformation suggesting a bow and arrow. Its class indicates that it is a poor, loose cluster, though detached from the star field. It is somewhat concentrated at its center, and its less than 50 stars range moderately in brightness. Located 2 degrees south of Gamma Velorum, NGC 2547 is an open cluster containing around 50 stars of magnitudes 7 to 15. NGC 3201 is a globular cluster discovered by James Dunlop on May 28, 1826. Its stellar population is inhomogeneous, varying with distance from the core. The effective temperature of the stars shows an increase with greater distance, with the redder and cooler stars tending to be located closer to the core. As of 2010, is one of only two clusters (including Messier 4) that shows a definite inhomogeneous population. RCW 36 is a star-forming region in Vela, and one of the nearest sites of massive star formation. This star-forming region has given rise to a cluster of several hundred young stars that power an HII region. The star-forming region lies in Clump 6 in the Vela Molecular Ridge Cloud C. See also References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Mickey_Levy] | [TOKENS: 508] |
Contents Mickey Levy Mickey Levy (Hebrew: מיקי לוי; born 21 June 1951) is an Israeli politician who currently serves as a member of the Knesset for Yesh Atid and is a former Speaker of the Knesset. He served as Deputy Minister of Finance between 2013 and 2014. Before entering politics he was a police officer. Biography Levy was born in Jerusalem to immigrant parents who were of Kurdish Jewish origin from Cizre, Turkey. He did his military service in the Israel Defense Forces in the Paratroopers Brigade. After being discharged from the military, he joined the Israel Police and held a series of command positions. He served as head of Jerusalem branch of the Israel Police between 2000 and 2004, winning the Knight of Good Government award in 2002. After retiring he worked as the Israeli police attaché in Washington, D.C. until 2007. He also gained a BA in political science from the University of Haifa and an MEd from the University of Derby, as well as serving as CEO of the Egged Ta'avura bus company. Prior to the 2013 Knesset elections, Levy joined the new Yesh Atid party and was placed eleventh on its list. He entered the Knesset after the party won 19 seats. Following Yesh Atid's coalition agreement with Likud, he was appointed to serve as Deputy Finance Minister. He was placed eleventh on the party's list again for the 2015 elections, and was re-elected as the party won 11 seats. In the build-up to the April 2019 elections, Yesh Atid joined the Blue and White alliance, with Levy placed twenty-second on its list. He was re-elected as the alliance won 35 seats. As part of the agreement between Naftali Bennett and Yair Lapid to form a "change" government, Levy was elected Speaker of the 24th Knesset on 13 June 2021, defeating Ya'akov Margi of Shas. Following the 2022 elections Levy was replaced as speaker by Yariv Levin. Levy, as the chair of the State Control Committee, voted in October 2025 in favor of creating a commission of inquiry on the 7 October attacks, though it was voted down. Personal life Levy is married to Nurit and has four children and lives in the Mevasseret Zion suburb of Jerusalem. References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Python_(programming_language)#cite_ref-103] | [TOKENS: 4314] |
Contents Python (programming language) Python is a high-level, general-purpose programming language. Its design philosophy emphasizes code readability with the use of significant indentation. Python is dynamically type-checked and garbage-collected. It supports multiple programming paradigms, including structured (particularly procedural), object-oriented and functional programming. Guido van Rossum began working on Python in the late 1980s as a successor to the ABC programming language. Python 3.0, released in 2008, was a major revision and not completely backward-compatible with earlier versions. Beginning with Python 3.5, capabilities and keywords for typing were added to the language, allowing optional static typing. As of 2026[update], the Python Software Foundation supports Python 3.10, 3.11, 3.12, 3.13, and 3.14, following the project's annual release cycle and five-year support policy. Python 3.15 is currently in the alpha development phase, and the stable release is expected to come out in October 2026. Earlier versions in the 3.x series have reached end-of-life and no longer receive security updates. Python has gained widespread use in the machine learning community. It is widely taught as an introductory programming language. Since 2003, Python has consistently ranked in the top ten of the most popular programming languages in the TIOBE Programming Community Index, which ranks based on searches in 24 platforms. History Python was conceived in the late 1980s by Guido van Rossum at Centrum Wiskunde & Informatica (CWI) in the Netherlands. It was designed as a successor to the ABC programming language, which was inspired by SETL, capable of exception handling and interfacing with the Amoeba operating system. Python implementation began in December 1989. Van Rossum first released it in 1991 as Python 0.9.0. Van Rossum assumed sole responsibility for the project, as the lead developer, until 12 July 2018, when he announced his "permanent vacation" from responsibilities as Python's "benevolent dictator for life" (BDFL); this title was bestowed on him by the Python community to reflect his long-term commitment as the project's chief decision-maker. (He has since come out of retirement and is self-titled "BDFL-emeritus".) In January 2019, active Python core developers elected a five-member Steering Council to lead the project. The name Python derives from the British comedy series Monty Python's Flying Circus. (See § Naming.) Python 2.0 was released on 16 October 2000, featuring many new features such as list comprehensions, cycle-detecting garbage collection, reference counting, and Unicode support. Python 2.7's end-of-life was initially set for 2015, and then postponed to 2020 out of concern that a large body of existing code could not easily be forward-ported to Python 3. It no longer receives security patches or updates. While Python 2.7 and older versions are officially unsupported, a different unofficial Python implementation, PyPy, continues to support Python 2, i.e., "2.7.18+" (plus 3.11), with the plus signifying (at least some) "backported security updates". Python 3.0 was released on 3 December 2008, and was a major revision and not completely backward-compatible with earlier versions, with some new semantics and changed syntax. Python 2.7.18, released in 2020, was the last release of Python 2. Several releases in the Python 3.x series have added new syntax to the language, and made a few (considered very minor) backward-incompatible changes. As of January 2026[update], Python 3.14.3 is the latest stable release. All older 3.x versions had a security update down to Python 3.9.24 then again with 3.9.25, the final version in 3.9 series. Python 3.10 is, since November 2025, the oldest supported branch. Python 3.15 has an alpha released, and Android has an official downloadable executable available for Python 3.14. Releases receive two years of full support followed by three years of security support. Design philosophy and features Python is a multi-paradigm programming language. Object-oriented programming and structured programming are fully supported, and many of their features support functional programming and aspect-oriented programming – including metaprogramming and metaobjects. Many other paradigms are supported via extensions, including design by contract and logic programming. Python is often referred to as a 'glue language' because it is purposely designed to be able to integrate components written in other languages. Python uses dynamic typing and a combination of reference counting and a cycle-detecting garbage collector for memory management. It uses dynamic name resolution (late binding), which binds method and variable names during program execution. Python's design offers some support for functional programming in the "Lisp tradition". It has filter, map, and reduce functions; list comprehensions, dictionaries, sets, and generator expressions. The standard library has two modules (itertools and functools) that implement functional tools borrowed from Haskell and Standard ML. Python's core philosophy is summarized in the Zen of Python (PEP 20) written by Tim Peters, which includes aphorisms such as these: However, Python has received criticism for violating these principles and adding unnecessary language bloat. Responses to these criticisms note that the Zen of Python is a guideline rather than a rule. The addition of some new features had been controversial: Guido van Rossum resigned as Benevolent Dictator for Life after conflict about adding the assignment expression operator in Python 3.8. Nevertheless, rather than building all functionality into its core, Python was designed to be highly extensible via modules. This compact modularity has made it particularly popular as a means of adding programmable interfaces to existing applications. Van Rossum's vision of a small core language with a large standard library and easily extensible interpreter stemmed from his frustrations with ABC, which represented the opposite approach. Python claims to strive for a simpler, less-cluttered syntax and grammar, while giving developers a choice in their coding methodology. Python lacks do .. while loops, which Rossum considered harmful. In contrast to Perl's motto "there is more than one way to do it", Python advocates an approach where "there should be one – and preferably only one – obvious way to do it". In practice, however, Python provides many ways to achieve a given goal. There are at least three ways to format a string literal, with no certainty as to which one a programmer should use. Alex Martelli is a Fellow at the Python Software Foundation and Python book author; he wrote that "To describe something as 'clever' is not considered a compliment in the Python culture." Python's developers typically prioritize readability over performance. For example, they reject patches to non-critical parts of the CPython reference implementation that would offer increases in speed that do not justify the cost of clarity and readability.[failed verification] Execution speed can be improved by moving speed-critical functions to extension modules written in languages such as C, or by using a just-in-time compiler like PyPy. Also, it is possible to transpile to other languages. However, this approach either fails to achieve the expected speed-up, since Python is a very dynamic language, or only a restricted subset of Python is compiled (with potential minor semantic changes). Python is meant to be a fun language to use. This goal is reflected in the name – a tribute to the British comedy group Monty Python – and in playful approaches to some tutorials and reference materials. For instance, some code examples use the terms "spam" and "eggs" (in reference to a Monty Python sketch), rather than the typical terms "foo" and "bar". A common neologism in the Python community is pythonic, which has a broad range of meanings related to program style: Pythonic code may use Python idioms well; be natural or show fluency in the language; or conform with Python's minimalist philosophy and emphasis on readability. Syntax and semantics Python is meant to be an easily readable language. Its formatting is visually uncluttered and often uses English keywords where other languages use punctuation. Unlike many other languages, it does not use curly brackets to delimit blocks, and semicolons after statements are allowed but rarely used. It has fewer syntactic exceptions and special cases than C or Pascal. Python uses whitespace indentation, rather than curly brackets or keywords, to delimit blocks. An increase in indentation comes after certain statements; a decrease in indentation signifies the end of the current block. Thus, the program's visual structure accurately represents its semantic structure. This feature is sometimes termed the off-side rule. Some other languages use indentation this way; but in most, indentation has no semantic meaning. The recommended indent size is four spaces. Python's statements include the following: The assignment statement (=) binds a name as a reference to a separate, dynamically allocated object. Variables may subsequently be rebound at any time to any object. In Python, a variable name is a generic reference holder without a fixed data type; however, it always refers to some object with a type. This is called dynamic typing—in contrast to statically-typed languages, where each variable may contain only a value of a certain type. Python does not support tail call optimization or first-class continuations; according to Van Rossum, the language never will. However, better support for coroutine-like functionality is provided by extending Python's generators. Before 2.5, generators were lazy iterators; data was passed unidirectionally out of the generator. From Python 2.5 on, it is possible to pass data back into a generator function; and from version 3.3, data can be passed through multiple stack levels. Python's expressions include the following: In Python, a distinction between expressions and statements is rigidly enforced, in contrast to languages such as Common Lisp, Scheme, or Ruby. This distinction leads to duplicating some functionality, for example: A statement cannot be part of an expression; because of this restriction, expressions such as list and dict comprehensions (and lambda expressions) cannot contain statements. As a particular case, an assignment statement such as a = 1 cannot be part of the conditional expression of a conditional statement. Python uses duck typing, and it has typed objects but untyped variable names. Type constraints are not checked at definition time; rather, operations on an object may fail at usage time, indicating that the object is not of an appropriate type. Despite being dynamically typed, Python is strongly typed, forbidding operations that are poorly defined (e.g., adding a number and a string) rather than quietly attempting to interpret them. Python allows programmers to define their own types using classes, most often for object-oriented programming. New instances of classes are constructed by calling the class, for example, SpamClass() or EggsClass()); the classes are instances of the metaclass type (which is an instance of itself), thereby allowing metaprogramming and reflection. Before version 3.0, Python had two kinds of classes, both using the same syntax: old-style and new-style. Current Python versions support the semantics of only the new style. Python supports optional type annotations. These annotations are not enforced by the language, but may be used by external tools such as mypy to catch errors. Python includes a module typing including several type names for type annotations. Also, mypy supports a Python compiler called mypyc, which leverages type annotations for optimization. 1.33333 frozenset() Python includes conventional symbols for arithmetic operators (+, -, *, /), the floor-division operator //, and the modulo operator %. (With the modulo operator, a remainder can be negative, e.g., 4 % -3 == -2.) Also, Python offers the ** symbol for exponentiation, e.g. 5**3 == 125 and 9**0.5 == 3.0. Also, it offers the matrix‑multiplication operator @ . These operators work as in traditional mathematics; with the same precedence rules, the infix operators + and - can also be unary, to represent positive and negative numbers respectively. Division between integers produces floating-point results. The behavior of division has changed significantly over time: In Python terms, the / operator represents true division (or simply division), while the // operator represents floor division. Before version 3.0, the / operator represents classic division. Rounding towards negative infinity, though a different method than in most languages, adds consistency to Python. For instance, this rounding implies that the equation (a + b)//b == a//b + 1 is always true. Also, the rounding implies that the equation b*(a//b) + a%b == a is valid for both positive and negative values of a. As expected, the result of a%b lies in the half-open interval [0, b), where b is a positive integer; however, maintaining the validity of the equation requires that the result must lie in the interval (b, 0] when b is negative. Python provides a round function for rounding a float to the nearest integer. For tie-breaking, Python 3 uses the round to even method: round(1.5) and round(2.5) both produce 2. Python versions before 3 used the round-away-from-zero method: round(0.5) is 1.0, and round(-0.5) is −1.0. Python allows Boolean expressions that contain multiple equality relations to be consistent with general usage in mathematics. For example, the expression a < b < c tests whether a is less than b and b is less than c. C-derived languages interpret this expression differently: in C, the expression would first evaluate a < b, resulting in 0 or 1, and that result would then be compared with c. Python uses arbitrary-precision arithmetic for all integer operations. The Decimal type/class in the decimal module provides decimal floating-point numbers to a pre-defined arbitrary precision with several rounding modes. The Fraction class in the fractions module provides arbitrary precision for rational numbers. Due to Python's extensive mathematics library and the third-party library NumPy, the language is frequently used for scientific scripting in tasks such as numerical data processing and manipulation. Functions are created in Python by using the def keyword. A function is defined similarly to how it is called, by first providing the function name and then the required parameters. Here is an example of a function that prints its inputs: To assign a default value to a function parameter in case no actual value is provided at run time, variable-definition syntax can be used inside the function header. Code examples "Hello, World!" program: Program to calculate the factorial of a non-negative integer: Libraries Python's large standard library is commonly cited as one of its greatest strengths. For Internet-facing applications, many standard formats and protocols such as MIME and HTTP are supported. The language includes modules for creating graphical user interfaces, connecting to relational databases, generating pseudorandom numbers, arithmetic with arbitrary-precision decimals, manipulating regular expressions, and unit testing. Some parts of the standard library are covered by specifications—for example, the Web Server Gateway Interface (WSGI) implementation wsgiref follows PEP 333—but most parts are specified by their code, internal documentation, and test suites. However, because most of the standard library is cross-platform Python code, only a few modules must be altered or rewritten for variant implementations. As of 13 March 2025,[update] the Python Package Index (PyPI), the official repository for third-party Python software, contains over 614,339 packages. Development environments Most[which?] Python implementations (including CPython) include a read–eval–print loop (REPL); this permits the environment to function as a command line interpreter, with which users enter statements sequentially and receive results immediately. Also, CPython is bundled with an integrated development environment (IDE) called IDLE, which is oriented toward beginners.[citation needed] Other shells, including IDLE and IPython, add additional capabilities such as improved auto-completion, session-state retention, and syntax highlighting. Standard desktop IDEs include PyCharm, Spyder, and Visual Studio Code; there are web browser-based IDEs, such as the following environments: Implementations CPython is the reference implementation of Python. This implementation is written in C, meeting the C11 standard since version 3.11. Older versions use the C89 standard with several select C99 features, but third-party extensions are not limited to older C versions—e.g., they can be implemented using C11 or C++. CPython compiles Python programs into an intermediate bytecode, which is then executed by a virtual machine. CPython is distributed with a large standard library written in a combination of C and native Python. CPython is available for many platforms, including Windows and most modern Unix-like systems, including macOS (and Apple M1 Macs, since Python 3.9.1, using an experimental installer). Starting with Python 3.9, the Python installer intentionally fails to install on Windows 7 and 8; Windows XP was supported until Python 3.5, with unofficial support for VMS. Platform portability was one of Python's earliest priorities. During development of Python 1 and 2, even OS/2 and Solaris were supported; since that time, support has been dropped for many platforms. All current Python versions (since 3.7) support only operating systems that feature multithreading, by now supporting not nearly as many operating systems (dropping many outdated) than in the past. All alternative implementations have at least slightly different semantics. For example, an alternative may include unordered dictionaries, in contrast to other current Python versions. As another example in the larger Python ecosystem, PyPy does not support the full C Python API. Creating an executable with Python often is done by bundling an entire Python interpreter into the executable, which causes binary sizes to be massive for small programs, yet there exist implementations that are capable of truly compiling Python. Alternative implementations include the following: Stackless Python is a significant fork of CPython that implements microthreads. This implementation uses the call stack differently, thus allowing massively concurrent programs. PyPy also offers a stackless version. Just-in-time Python compilers have been developed, but are now unsupported: There are several compilers/transpilers to high-level object languages; the source language is unrestricted Python, a subset of Python, or a language similar to Python: There are also specialized compilers: Some older projects existed, as well as compilers not designed for use with Python 3.x and related syntax: A performance comparison among various Python implementations, using a non-numerical (combinatorial) workload, was presented at EuroSciPy '13. In addition, Python's performance relative to other programming languages is benchmarked by The Computer Language Benchmarks Game. There are several approaches to optimizing Python performance, despite the inherent slowness of an interpreted language. These approaches include the following strategies or tools: Language Development Python's development is conducted mostly through the Python Enhancement Proposal (PEP) process; this process is the primary mechanism for proposing major new features, collecting community input on issues, and documenting Python design decisions. Python coding style is covered in PEP 8. Outstanding PEPs are reviewed and commented on by the Python community and the steering council. Enhancement of the language corresponds with development of the CPython reference implementation. The mailing list python-dev is the primary forum for the language's development. Specific issues were originally discussed in the Roundup bug tracker hosted by the foundation. In 2022, all issues and discussions were migrated to GitHub. Development originally took place on a self-hosted source-code repository running Mercurial, until Python moved to GitHub in January 2017. CPython's public releases have three types, distinguished by which part of the version number is incremented: Many alpha, beta, and release-candidates are also released as previews and for testing before final releases. Although there is a rough schedule for releases, they are often delayed if the code is not ready yet. Python's development team monitors the state of the code by running a large unit test suite during development. The major academic conference on Python is PyCon. Also, there are special Python mentoring programs, such as PyLadies. Naming Python's name is inspired by the British comedy group Monty Python, whom Python creator Guido van Rossum enjoyed while developing the language. Monty Python references appear frequently in Python code and culture; for example, the metasyntactic variables often used in Python literature are spam and eggs, rather than the traditional foo and bar. Also, the official Python documentation contains various references to Monty Python routines. Python users are sometimes referred to as "Pythonistas". Languages influenced by Python See also Notes References Further reading External links |
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