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[SOURCE: https://en.wikipedia.org/wiki/Big_Jim_(toy_line)] | [TOKENS: 1677] |
Contents Big Jim (toy line) Big Jim was a line of action figure toys produced from 1972 through 1986 by Mattel for the North American and European markets. He was renamed Kid Acero in Latin America and, for a short period of time, Mark Strong in Europe. Originally inspired by G.I. Joe, the Big Jim line was smaller in size (closer to 10 inches in height compared to Joe's 12) and each figure included a push button in the back that made the character execute a karate chop action. The action figure's arms were made of a soft plastic/vinyl material and contained a mechanism that simulated the bulge of a biceps when the elbow was bent. Big Jim was less military-oriented than the G.I. Joe line, having more of a secret agent motif, but also had a large variety of outfits and situations available including sports, space exploration, martial arts, hunting, western, camping, fishing, and photography. Basic characters Characters are sorted in the year in which they made their first appearance. Note that most of them were produced for several years after their initial release. The Original Edition First Editions – Originally, Big Jim action figures came out in a small blue box with red and white stripes. The 1972 toy line was split into three sub lines: the Basic Line, the Adventure Line and the Sports Line. Simultaneously, Mattel released an almost identical figure named Mark Strong, The Man from Mattel© in Europe. The Mark Strong figure was nearly identical to Big Jim and came with the same accessories. The crotch piece of the Mark Strong figure was thinner and more fragile than that of Big Jim. The basic line was composed mostly of figures which came almost naked, with minimal clothes or accessories. The original basic Big Jim came dressed in orange shorts with white stripes and included a karate board, a dumbbell and test of strength belt. Jack was an identical, figure, with only a different head. He was one of the first toys produced in the United States to represent a minority character in a respectful way. The Basic line also included the first incarnations of Josh and Jeff. Jeff is an Aussie type figure dressed with shorts and brown hat that came with a chopping knife, a chest belt and a bamboo stand. Josh is a bearded woodsman figure fully dressed in denim vest and shorts with brown boots. He was the only one which came with vest and shoes. All four basic figures had a mechanism that simulated the bulge of a biceps when the arm was bent. The adventure series was composed mostly of camping and explorer vehicles, and these were the first playsets in the toyline. Three animals were released with this first wave: a gorilla, a rhino and a crocodile. The sports line was composed of different versions of Big Jim. He was a baseball player, a hockey player, a pugilist, and an eagle ranger. The eagle which came with this set was also included with several later versions of Big Jim. The first wave of Big Jim also included a figure dressed as a nuclear plant worker, which had no relation to any other figures in the line. P.A.C.K. Series In 1975, Mattel decided to create an extension of the main toy line making Big Jim the leader of a Mission Impossible-like group of heroes for hire. This series is easy to identify because all related products have a howling wolf as its principal image and character art by Jack Kirby. The members of the spy group were named P.A.C.K., which is an acronym derived from "Professional Agents – Crime Killers". On its initial release, the series presented Jim as "Commander", this time as the leader of a counter intelligence strike team. He and two of his most loyal friends joins forces to against a hooded villain known as "Zorak, the ruler of the Underworld". The first Zorak action figure was named Double Trouble Zorak, because he had a face-changing feature where his normal-looking head could be turned into a monstrous green visage. Two Big Jim action figures were relaunched to join forces against Zorak. One of them was Warpath (a Native American archer) who was previously released as Tankua. Seems like the main reason for the name change was the difficulty in pronouncing "Tankua" properly, and the need for a more dynamic name. Dr. Steel returned too, but this time as a hero and member of the P.A.C.K. A new character was added to the group, The Whip, a weapons specialist armed with a bullwhip. One year later, a new character named Torpedo Fist, (a former sailor with an artificial hand and forearm) was added to the team. In Latin America several parts of this figure in particular were split to create new Big Jim characters not released in the United States, as part of the region's version of P.A.C.K., named LOBO Squadron. Pirate Series In 1978, Mattel launched a pirate themed series exclusively in Europe. The series initially consisted of repaints and retooled figures, but eventually included some figures exclusive to the region. Space Series Spy Series In 1979 and 1980, Mattel released a series of spy themed Big Jim figures. Global Command vs. Condor Force The last Big Jim sci-fi themed series appeared in the 1980s and was only distributed in Europe. There were eight characters, four "good" and four "evil", divided into two opposing camps: "Global Command" and "Condor Force", respectively. The leaders of both groups were redesigned: new heads were sculpted for the Big Jim and Professor Obb figures. Big Jim's Vehicles & Bikes Kid Acero Most Big Jim toys from the early 1970s from the adventure and sport series were sold as "Kid Acero" (Kid Steel) in Latin America. All toys are exactly the same as in the American versions and were produced by a local Mattel subsidiary with only the name being changed. The Kid Acero toy line also included several figures which were exclusively created for the Mexican market, such as The Invisible Man, The Bionic Man, Garfio, and Nocton' and retooled and repainted versions of several Big Jim toys not available in the United States or Europe. Karl May's Winnetou and Old Shatterhand A series based on the Wild West characters of the popular German writer Karl May (1842–1912) and especially the 1960s series of Karl May movies was available in the late 1970s, including Old Shatterhand and Winnetou, Chief of the Apache. In addition to May's creations Old Firehand and Old Surehand, the character of Bloody Fox was invented for the toyline. With Nscho-Tschi, Winnetou's sister, a unique female character was introduced to the series. Mattel released six dolls in the Karl May line; they came in large green display boxes with the Karl May logo on the box. The lineup was as follows: In other countries this series was renamed and distributed as part of the official Big Jim line. In Italy it appeared as Gli amici del West di Big Jim ("Big Jim's Friends of the West"), and in Spain it was made by Congost as Oeste ("West"). Most of the characters were also renamed for these releases. Furthermore, the Warpath character, known as Chief Tankua, was added to the West series in Italy. James Bond, Agent 007 Most of the Big Jim toys from the early 1980s were sold as "James Bond" toys in Latin America. The American Spy and Space series were renamed "James Bond, secret agent 007". All toys are exactly the same as in the American and European versions and were produced by a local Mattel subsidiary. Only the brand on the packages is different. Other media A live-action film adaptation produced by Mattel Films and directed by Dan Mazer was announced in January 2022. Comics Big Jim (Kid Acero) had his own title in Latin America which ran for 36 issues in 1979 published in Mexico by Editorial Novaro. References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Jews#cite_note-:4-31] | [TOKENS: 15852] |
Contents Jews Jews (Hebrew: יְהוּדִים, ISO 259-2: Yehudim, Israeli pronunciation: [jehuˈdim]), or the Jewish people, are an ethnoreligious group and nation, originating from the Israelites of ancient Israel and Judah. They traditionally adhere to Judaism. Jewish ethnicity, religion, and community are highly interrelated, as Judaism is an ethnic religion, though many ethnic Jews do not practice it. Religious Jews regard converts to Judaism as members of the Jewish nation, pursuant to the long-standing conversion process. The Israelites emerged from the pre-existing Canaanite peoples to establish Israel and Judah in the Southern Levant during the Iron Age. Originally, Jews referred to the inhabitants of the kingdom of Judah and were distinguished from the gentiles and the Samaritans. According to the Hebrew Bible, these inhabitants predominately originate from the tribe of Judah, who were descendants of Judah, the fourth son of Jacob. The tribe of Benjamin were another significant demographic in Judah and were considered Jews too. By the late 6th century BCE, Judaism had evolved from the Israelite religion, dubbed Yahwism (for Yahweh) by modern scholars, having a theology that religious Jews believe to be the expression of the Mosaic covenant between God and the Jewish people. After the Babylonian exile, Jews referred to followers of Judaism, descendants of the Israelites, citizens of Judea, or allies of the Judean state. Jewish migration within the Mediterranean region during the Hellenistic period, followed by population transfers, caused by events like the Jewish–Roman wars, gave rise to the Jewish diaspora, consisting of diverse Jewish communities that maintained their sense of Jewish history, identity, and culture. In the following millennia, Jewish diaspora communities coalesced into three major ethnic subdivisions according to where their ancestors settled: the Ashkenazim (Central and Eastern Europe), the Sephardim (Iberian Peninsula), and the Mizrahim (Middle East and North Africa). While these three major divisions account for most of the world's Jews, there are other smaller Jewish groups outside of the three. Prior to World War II, the global Jewish population reached a peak of 16.7 million, representing around 0.7% of the world's population at that time. During World War II, approximately six million Jews throughout Europe were systematically murdered by Nazi Germany in a genocide known as the Holocaust. Since then, the population has slowly risen again, and as of 2021[update], was estimated to be at 15.2 million by the demographer Sergio Della Pergola or less than 0.2% of the total world population in 2012.[b] Today, over 85% of Jews live in Israel or the United States. Israel, whose population is 73.9% Jewish, is the only country where Jews comprise more than 2.5% of the population. Jews have significantly influenced and contributed to the development and growth of human progress in many fields, both historically and in modern times, including in science and technology, philosophy, ethics, literature, governance, business, art, music, comedy, theatre, cinema, architecture, food, medicine, and religion. Jews founded Christianity and had an indirect but profound influence on Islam. In these ways and others, Jews have played a significant role in the development of Western culture. Name and etymology The term "Jew" is derived from the Hebrew word יְהוּדִי Yehudi, with the plural יְהוּדִים Yehudim. Endonyms in other Jewish languages include the Ladino ג׳ודיו Djudio (plural ג׳ודיוס, Djudios) and the Yiddish ייִד Yid (plural ייִדן Yidn). Though Genesis 29:35 and 49:8 connect "Judah" with the verb yada, meaning "praise", scholars generally agree that "Judah" most likely derives from the name of a Levantine geographic region dominated by gorges and ravines. The gradual ethnonymic shift from "Israelites" to "Jews", regardless of their descent from Judah, although not contained in the Torah, is made explicit in the Book of Esther (4th century BCE) of the Tanakh. Some modern scholars disagree with the conflation, based on the works of Josephus, Philo and Apostle Paul. The English word "Jew" is a derivation of Middle English Gyw, Iewe. The latter was loaned from the Old French giu, which itself evolved from the earlier juieu, which in turn derived from judieu/iudieu which through elision had dropped the letter "d" from the Medieval Latin Iudaeus, which, like the New Testament Greek term Ioudaios, meant both "Jew" and "Judean" / "of Judea". The Greek term was a loan from Aramaic *yahūdāy, corresponding to Hebrew יְהוּדִי Yehudi. Some scholars prefer translating Ioudaios as "Judean" in the Bible since it is more precise, denotes the community's origins and prevents readers from engaging in antisemitic eisegesis. Others disagree, believing that it erases the Jewish identity of Biblical characters such as Jesus. Daniel R. Schwartz distinguishes "Judean" and "Jew". Here, "Judean" refers to the inhabitants of Judea, which encompassed southern Palestine. Meanwhile, "Jew" refers to the descendants of Israelites that adhere to Judaism. Converts are included in the definition. But Shaye J.D. Cohen argues that "Judean" is inclusive of believers of the Judean God and allies of the Judean state. Another scholar, 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." The etymological equivalent is in use in other languages, e.g., يَهُودِيّ yahūdī (sg.), al-yahūd (pl.), in Arabic, "Jude" in German, "judeu" in Portuguese, "Juif" (m.)/"Juive" (f.) in French, "jøde" in Danish and Norwegian, "judío/a" in Spanish, "jood" in Dutch, "żyd" in Polish etc., but derivations of the word "Hebrew" are also in use to describe a Jew, e.g., in Italian (Ebreo), in Persian ("Ebri/Ebrani" (Persian: عبری/عبرانی)) and Russian (Еврей, Yevrey). The German word "Jude" is pronounced [ˈjuːdə], the corresponding adjective "jüdisch" [ˈjyːdɪʃ] (Jewish) is the origin of the word "Yiddish". According to The American Heritage Dictionary of the English Language, fourth edition (2000), It is widely recognized that the attributive use of the noun Jew, in phrases such as Jew lawyer or Jew ethics, is both vulgar and highly offensive. In such contexts Jewish is the only acceptable possibility. Some people, however, have become so wary of this construction that they have extended the stigma to any use of Jew as a noun, a practice that carries risks of its own. In a sentence such as There are now several Jews on the council, which is unobjectionable, the substitution of a circumlocution like Jewish people or persons of Jewish background may in itself cause offense for seeming to imply that Jew has a negative connotation when used as a noun. Identity Judaism shares some of the characteristics of a nation, an ethnicity, a religion, and a culture, making the definition of who is a Jew vary slightly depending on whether a religious or national approach to identity is used.[better source needed] Generally, in modern secular usage, Jews include three groups: people who were born to a Jewish family regardless of whether or not they follow the religion, those who have some Jewish ancestral background or lineage (sometimes including those who do not have strictly matrilineal descent), and people without any Jewish ancestral background or lineage who have formally converted to Judaism and therefore are followers of the religion. In the context of biblical and classical literature, Jews could refer to inhabitants of the Kingdom of Judah, or the broader Judean region, allies of the Judean state, or anyone that followed Judaism. Historical definitions of Jewish identity have traditionally been based on halakhic definitions of matrilineal descent, and halakhic conversions. These definitions of who is a Jew date back to the codification of the Oral Torah into the Babylonian Talmud, around 200 CE. Interpretations by Jewish sages of sections of the Tanakh – such as Deuteronomy 7:1–5, which forbade intermarriage between their Israelite ancestors and seven non-Israelite nations: "for that [i.e. giving your daughters to their sons or taking their daughters for your sons,] would turn away your children from following me, to serve other gods"[failed verification] – are used as a warning against intermarriage between Jews and gentiles. Leviticus 24:10 says that the son in a marriage between a Hebrew woman and an Egyptian man is "of the community of Israel." This is complemented by Ezra 10:2–3, where Israelites returning from Babylon vow to put aside their gentile wives and their children. A popular theory is that the rape of Jewish women in captivity brought about the law of Jewish identity being inherited through the maternal line, although scholars challenge this theory citing the Talmudic establishment of the law from the pre-exile period. Another argument is that the rabbis changed the law of patrilineal descent to matrilineal descent due to the widespread rape of Jewish women by Roman soldiers. Since the anti-religious Haskalah movement of the late 18th and 19th centuries, halakhic interpretations of Jewish identity have been challenged. According to historian Shaye J. D. Cohen, the status of the offspring of mixed marriages was determined patrilineally in the Bible. He brings two likely explanations for the change in Mishnaic times: first, the Mishnah may have been applying the same logic to mixed marriages as it had applied to other mixtures (Kil'ayim). Thus, a mixed marriage is forbidden as is the union of a horse and a donkey, and in both unions the offspring are judged matrilineally. Second, the Tannaim may have been influenced by Roman law, which dictated that when a parent could not contract a legal marriage, offspring would follow the mother. Rabbi Rivon Krygier follows a similar reasoning, arguing that Jewish descent had formerly passed through the patrilineal descent and the law of matrilineal descent had its roots in the Roman legal system. Origins The prehistory and ethnogenesis of the Jews are closely intertwined with archaeology, biology, historical textual records, mythology, and religious literature. The ethnic origin of the Jews lie in the Israelites, a confederation of Iron Age Semitic-speaking tribes that inhabited a part of Canaan during the tribal and monarchic periods. Modern Jews are named after and also descended from the southern Israelite Kingdom of Judah. Gary A. Rendsburg links the early Canaanite nomadic pastoralists confederation to the Shasu known to the Egyptians around the 15th century BCE. According to the Hebrew Bible narrative, Jewish history begins with the Biblical patriarchs such as Abraham, his son Isaac, Isaac's son Jacob, and the Biblical matriarchs Sarah, Rebecca, Leah, and Rachel, who lived in Canaan. The twelve sons of Jacob subsequently gave birth to the Twelve Tribes. Jacob and his family migrated to Ancient Egypt after being invited to live with Jacob's son Joseph by the Pharaoh himself. Jacob's descendants were later enslaved until the Exodus, led by Moses. Afterwards, the Israelites conquered Canaan under Moses' successor Joshua, and went through the period of the Biblical judges after the death of Joshua. Through the mediation of Samuel, the Israelites were subject to a king, Saul, who was succeeded by David and then Solomon, after whom the United Monarchy ended and was split into a separate Kingdom of Israel and a Kingdom of Judah. The Kingdom of Judah is described as comprising the tribes of Judah, Benjamin and partially, Levi. They later assimilated remnants of other tribes who migrated there from the northern Kingdom of Israel. In the extra-biblical record, the Israelites become visible as a people between 1200 and 1000 BCE. There is well accepted archeological evidence referring to "Israel" in the Merneptah Stele, which dates to about 1200 BCE, and in the Mesha stele from 840 BCE. It is debated whether a period like that of the Biblical judges occurred and if there ever was a United Monarchy. There is further disagreement about the earliest existence of the Kingdoms of Israel and Judah and their extent and power. Historians agree that a Kingdom of Israel existed by c. 900 BCE,: 169–95 there is a consensus that a Kingdom of Judah existed by c. 700 BCE at least, and recent excavations in Khirbet Qeiyafa have provided strong evidence for dating the Kingdom of Judah to the 10th century BCE. In 587 BCE, Nebuchadnezzar II, King of the Neo-Babylonian Empire, besieged Jerusalem, destroyed the First Temple and deported parts of the Judahite population. Scholars disagree regarding the extent to which the Bible should be accepted as a historical source for early Israelite history. Rendsburg states that there are two approximately equal groups of scholars who debate the historicity of the biblical narrative, the minimalists who largely reject it, and the maximalists who largely accept it, with the minimalists being the more vocal of the two. Some of the leading minimalists reframe the biblical account as constituting the Israelites' inspiring national myth narrative, suggesting that according to the modern archaeological and historical account, the Israelites and their culture did not overtake the region by force, but instead branched out of the Canaanite peoples and culture through the development of a distinct monolatristic—and later monotheistic—religion of Yahwism centered on Yahweh, one of the gods of the Canaanite pantheon. The growth of Yahweh-centric belief, along with a number of cultic practices, gradually gave rise to a distinct Israelite ethnic group, setting them apart from other Canaanites. According to Dever, modern archaeologists have largely discarded the search for evidence of the biblical narrative surrounding the patriarchs and the exodus. According to the maximalist position, the modern archaeological record independently points to a narrative which largely agrees with the biblical account. This narrative provides a testimony of the Israelites as a nomadic people known to the Egyptians as belonging to the Shasu. Over time these nomads left the desert and settled on the central mountain range of the land of Canaan, in simple semi-nomadic settlements in which pig bones are notably absent. This population gradually shifted from a tribal lifestyle to a monarchy. While the archaeological record of the ninth century BCE provides evidence for two monarchies, one in the south under a dynasty founded by a figure named David with its capital in Jerusalem, and one in the north under a dynasty founded by a figure named Omri with its capital in Samaria. It also points to an early monarchic period in which these regions shared material culture and religion, suggesting a common origin. Archaeological finds also provide evidence for the later cooperation of these two kingdoms in their coalition against Aram, and for their destructions by the Assyrians and later by the Babylonians. Genetic studies on Jews show that most Jews worldwide bear a common genetic heritage which originates in the Middle East, and that they share certain genetic traits with other Gentile peoples of the Fertile Crescent. The genetic composition of different Jewish groups shows that Jews share a common gene pool dating back four millennia, as a marker of their common ancestral origin. Despite their long-term separation, Jewish communities maintained their unique commonalities, propensities, and sensibilities in culture, tradition, and language. History The earliest recorded evidence of a people by the name of Israel appears in the Merneptah Stele, which dates to around 1200 BCE. The majority of scholars agree that this text refers to the Israelites, a group that inhabited the central highlands of Canaan, where archaeological evidence shows that hundreds of small settlements were constructed between the 12th and 10th centuries BCE. The Israelites differentiated themselves from neighboring peoples through various distinct characteristics including religious practices, prohibition on intermarriage, and an emphasis on genealogy and family history. In the 10th century BCE, two neighboring Israelite kingdoms—the northern Kingdom of Israel and the southern Kingdom of Judah—emerged. Since their inception, they shared ethnic, cultural, linguistic and religious characteristics despite a complicated relationship. Israel, with its capital mostly in Samaria, was larger and wealthier, and soon developed into a regional power. In contrast, Judah, with its capital in Jerusalem, was less prosperous and covered a smaller, mostly mountainous territory. However, while in Israel the royal succession was often decided by a military coup d'état, resulting in several dynasty changes, political stability in Judah was much greater, as it was ruled by the House of David for the whole four centuries of its existence. Scholars also describe Biblical Jews as a 'proto-nation', in the modern nationalist sense, comparable to classical Greeks, the Gauls and the British Celts. Around 720 BCE, Kingdom of Israel was destroyed when it was conquered by the Neo-Assyrian Empire, which came to dominate the ancient Near East. Under the Assyrian resettlement policy, a significant portion of the northern Israelite population was exiled to Mesopotamia and replaced by immigrants from the same region. During the same period, and throughout the 7th century BCE, the Kingdom of Judah, now under Assyrian vassalage, experienced a period of prosperity and witnessed a significant population growth. This prosperity continued until the Neo-Assyrian king Sennacherib devastated the region of Judah in response to a rebellion in the area, ultimately halting at Jerusalem. Later in the same century, the Assyrians were defeated by the rising Neo-Babylonian Empire, and Judah became its vassal. In 587 BCE, following a revolt in Judah, the Babylonian king Nebuchadnezzar II besieged and destroyed Jerusalem and the First Temple, putting an end to the kingdom. The majority of Jerusalem's residents, including the kingdom's elite, were exiled to Babylon. According to the Book of Ezra, the Persian Cyrus the Great ended the Babylonian exile in 538 BCE, the year after he captured Babylon. The exile ended with the return under Zerubbabel the Prince (so called because he was a descendant of the royal line of David) and Joshua the Priest (a descendant of the line of the former High Priests of the Temple) and their construction of the Second Temple circa 521–516 BCE. As part of the Persian Empire, the former Kingdom of Judah became the province of Judah (Yehud Medinata), with a smaller territory and a reduced population. Judea was under control of the Achaemenids until the fall of their empire in c. 333 BCE to Alexander the Great. After several centuries under foreign imperial rule, the Maccabean Revolt against the Seleucid Empire resulted in an independent Hasmonean kingdom, under which the Jews once again enjoyed political independence for a period spanning from 110 to 63 BCE. Under Hasmonean rule the boundaries of their kingdom were expanded to include not only the land of the historical kingdom of Judah, but also the Galilee and Transjordan. In the beginning of this process the Idumeans, who had infiltrated southern Judea after the destruction of the First Temple, were converted en masse. In 63 BCE, Judea was conquered by the Romans. From 37 BCE to 6 CE, the Romans allowed the Jews to maintain some degree of independence by installing the Herodian dynasty as vassal kings. However, Judea eventually came directly under Roman control and was incorporated into the Roman Empire as the province of Judaea. The Jewish–Roman wars, a series of failed uprisings against Roman rule during the first and second centuries CE, had profound and devastating consequences for the Jewish population of Judaea. The First Jewish–Roman War (66–73/74 CE) culminated in the destruction of Jerusalem and the Second Temple, after which the significantly diminished Jewish population was stripped of political autonomy. A few generations later, the Bar Kokhba revolt (132–136 CE) erupted in response to Roman plans to rebuild Jerusalem as a Roman colony, and, possibly, to restrictions on circumcision. Its violent suppression by the Romans led to the near-total depopulation of Judea, and the demographic and cultural center of Jewish life shifted to Galilee. Jews were subsequently banned from residing in Jerusalem and the surrounding area, and the province of Judaea was renamed Syria Palaestina. These developments effectively ended Jewish efforts to restore political sovereignty in the region for nearly two millennia. Similar upheavals impacted the Jewish communities in the empire's eastern provinces during the Diaspora Revolt (115–117 CE), leading to the near-total destruction of Jewish diaspora communities in Libya, Cyprus and Egypt, including the highly influential community in Alexandria. The destruction of the Second Temple in 70 CE brought profound changes to Judaism. With the Temple's central place in Jewish worship gone, religious practices shifted towards prayer, Torah study (including Oral Torah), and communal gatherings in synagogues. Judaism also lost much of its sectarian nature.: 69 Two of the three main sects that flourished during the late Second Temple period, namely the Sadducees and Essenes, eventually disappeared, while Pharisaic beliefs became the foundational, liturgical, and ritualistic basis of Rabbinic Judaism, which emerged as the prevailing form of Judaism since late antiquity. The Jewish diaspora existed well before the destruction of the Second Temple in 70 CE and had been ongoing for centuries, with the dispersal driven by both forced expulsions and voluntary migrations. In Mesopotamia, a testimony to the beginnings of the Jewish community can be found in Joachin's ration tablets, listing provisions allotted to the exiled Judean king and his family by Nebuchadnezzar II, and further evidence are the Al-Yahudu tablets, dated to the 6th–5th centuries BCE and related to the exiles from Judea arriving after the destruction of the First Temple, though there is ample evidence for the presence of Jews in Babylonia even from 626 BCE. In Egypt, the documents from Elephantine reveal the trials of a community founded by a Persian Jewish garrison at two fortresses on the frontier during the 5th–4th centuries BCE, and according to Josephus the Jewish community in Alexandria existed since the founding of the city in the 4th century BCE by Alexander the Great. By 200 BCE, there were well established Jewish communities both in Egypt and Mesopotamia ("Babylonia" in Jewish sources) and in the two centuries that followed, Jewish populations were also present in Asia Minor, Greece, Macedonia, Cyrene, and, beginning in the middle of the first century BCE, in the city of Rome. Later, in the first centuries CE, as a result of the Jewish-Roman Wars, a large number of Jews were taken as captives, sold into slavery, or compelled to flee from the regions affected by the wars, contributing to the formation and expansion of Jewish communities across the Roman Empire as well as in Arabia and Mesopotamia. After the Bar Kokhba revolt, the Jewish population in Judaea—now significantly reduced— made efforts to recover from the revolt's devastating effects, but never fully regained its former strength. Between the second and fourth centuries CE, the region of Galilee emerged as the primary center of Jewish life in Syria Palaestina, experiencing both demographic growth and cultural development. It was during this period that two central rabbinic texts, the Mishnah and the Jerusalem Talmud, were composed. The Romans recognized the patriarchs—rabbinic sages such as Judah ha-Nasi—as representatives of the Jewish people, granting them a certain degree of autonomy. However, as the Roman Empire gave way to the Christianized Byzantine Empire under Constantine, Jews began to face persecution by both the Church and imperial authorities, Jews came to be persecuted by the church and the authorities, and many immigrated to communities in the diaspora. By the fourth century CE, Jews are believed to have lost their demographic majority in Syria Palaestina. The long-established Jewish community of Mesopotamia, which had been living under Parthian and later Sasanian rule, beyond the confines of the Roman Empire, became an important center of Jewish study as Judea's Jewish population declined. Estimates often place the Babylonian Jewish community of the 3rd to 7th centuries at around one million, making it the largest Jewish diaspora community of that period. Under the political leadership of the exilarch, who was regarded as a royal heir of the House of David, this community had an autonomous status and served as a place of refuge for the Jews of Syria Palaestina. A number of significant Talmudic academies, such as the Nehardea, Pumbedita, and Sura academies, were established in Mesopotamia, and many important Amoraim were active there. The Babylonian Talmud, a centerpiece of Jewish religious law, was compiled in Babylonia in the 3rd to 6th centuries. Jewish diaspora communities are generally described to have coalesced into three major ethnic subdivisions according to where their ancestors settled: the Ashkenazim (initially in the Rhineland and France), the Sephardim (initially in the Iberian Peninsula), and the Mizrahim (Middle East and North Africa). Romaniote Jews, Tunisian Jews, Yemenite Jews, Egyptian Jews, Ethiopian Jews, Bukharan Jews, Mountain Jews, and other groups also predated the arrival of the Sephardic diaspora. During the same period, Jewish communities in the Middle East thrived under Islamic rule, especially in cities like Baghdad, Cairo, and Damascus. In Babylonia, from the 7th to 11th centuries the Pumbedita and Sura academies led the Arab and to an extent the entire Jewish world. The deans and students of said academies defined the Geonic period in Jewish history. Following this period were the Rishonim who lived from the 11th to 15th centuries. Like their European counterparts, Jews in the Middle East and North Africa also faced periods of persecution and discriminatory policies, with the Almohad Caliphate in North Africa and Iberia issuing forced conversion decrees, causing Jews such as Maimonides to seek safety in other regions. Despite experiencing repeated waves of persecution, Ashkenazi Jews in Western Europe worked in a variety of fields, making an impact on their communities' economy and societies. In Francia, for example, figures like Isaac Judaeus and Armentarius occupied prominent social and economic positions. Francia also witnessed the development of a sophisticated tradition of biblical commentary, as exemplified by Rashi and the tosafists. In 1144, the first documented blood libel occurred in Norwich, England, marking an escalation in the pattern of discrimination and violence that Jews had already been subjected to throughout medieval Europe. During the 12th and 13th centuries, Jews faced frequent antisemitic legislation - including laws prescribing distinctive dress - alongside segregation, repeated blood libels, pogroms, and massacres such as the Rhineland Massacres (1066). The Jews of the Holy Roman Empire were designated Servi camerae regis (“servants of the imperial chamber”) by Frederick II, a status that afforded limited protection while simultaneously entangling them in the political struggles between the emperor and the German principalities and cities. Persecution intensified during the Black Death in the mid-14th century, when Jews were accused of poisoning wells and many communities were destroyed. These pressures, combined with major expulsions such as that from England in 1290, gradually pushed Ashkenazi Jewish populations eastward into Poland, Lithuania, and Russia. One of the largest Jewish communities of the Middle Ages was in the Iberian Peninsula, which for a time contained the largest Jewish population in Europe. Iberian Jewry endured discrimination under the Visigoths but saw its fortunes improve under Umayyad rule and later the Taifa kingdoms. During this period, the Jews of Muslim Spain entered a "Golden Age" marked by achievements in Hebrew poetry and literature, religious scholarship, grammar, medicine and science, with leading figures including Hasdai ibn Shaprut, Judah Halevi, Moses ibn Ezra and Solomon ibn Gabirol. Jews also rose to high office, most notably Samuel ibn Naghrillah, a scholar and poet who served as grand vizier and military commander of Granada. The Golden Age ended with the rise of the radical Almoravid and Almohad dynasties, whose persecutions drove many Jews from Iberia (including Maimonides), together with the advancing Reconquista. In 1391, widespread pogroms swept across Spain, leaving thousands dead and forcing mass conversions. The Spanish Inquisition was later established to pursue, torture and execute conversos who continued to practice Judaism in secret, while public disputations were staged to discredit Judaism. In 1492, after the Reconquista, Isabella I of Castile and Ferdinand II of Aragon decreed the expulsion of all Jews who refused conversion, sending an estimated 200,000 into exile in Portugal, Italy, North Africa, and the Ottoman Empire. In 1497, Portugal's Jews, about 30,000, were formally ordered expelled but instead were forcibly converted to retain their economic role. In 1498, some 3,500 Jews were expelled from Navarre. Many converts outwardly adopted Christianity while secretly preserving Jewish practices, becoming crypto-Jews (also known as marranos or anusim), who remained targets of the various Inquisitions for centuries. Following the expulsions from Spain and Portugal in the 1490s, Jewish exiles dispersed across the Mediterranean, Europe, and North Africa. Many settled in the Ottoman Empire—which, replacing the Iberian Peninsula, became home to the world's largest Jewish population—where new communities developed in Anatolia, the Balkans, and the Land of Israel. Cities such as Istanbul and Thessaloniki grew into major Jewish centers, while in 16th-century Safed a flourishing spiritual life took shape. There, Solomon Alkabetz, Moses Cordovero, and Isaac Luria developed influential new schools of Kabbalah, giving powerful impetus to Jewish mysticism, and Joseph Karo composed the Shulchan Aruch, which became a cornerstone of Jewish law. In the 17th century, Portuguese conversos who returned to Judaism and engaged in trade and banking helped establish Amsterdam as a prosperous Jewish center, while also forming communities in cities such as Antwerp and London. This period also witnessed waves of messianic fervor, most notably the rise of the Sabbatean movement in the 1660s, led by Sabbatai Zvi of İzmir, which reverberated throughout the Jewish world. In Eastern Europe, Poland–Lithuania became the principal center of Ashkenazi Jewry, eventually becoming home to the largest Jewish population in the world. Jewish life flourished there from in the early modern era, supported by relative stability, economic opportunity, and strong communal institutions. The mid-17th century brought devastation with the Cossack uprisings in Ukraine, which reversed migration flows and sent refugees westward, yet Poland–Lithuania remained the demographic and cultural heartland of Ashkenazic Jewry. Following the partitions of Poland, most of its Jews came under Russian rule and were confined to the "Pale of Settlement." The 18th century also witnessed new religious and intellectual currents. Hasidism, founded by Baal Shem Tov, emphasized mysticism and piety, while its opponents, the Misnagdim ("opponents") led by the Vilna Gaon, defended rabbinic scholarship and tradition. In Western Europe, during the 1760s and 1770s, the Haskalah (Jewish Enlightenment) emerged in German-speaking lands, where figures such as Moses Mendelssohn promoted secular learning, vernacular literacy, and integration into European society. Elsewhere, Jews began to be re-admitted to Western Europe, including England, where Menasseh ben Israel petitioned Oliver Cromwell for their return. In the Americas, Jews of Sephardic descent first arrived as conversos in Spanish and Portuguese colonies, where many faced trial by Inquisition tribunals for "judaizing." A more durable presence began in Dutch Brazil, where Jews openly practiced their religion and established the first synagogues in the New World, before the Portuguese reconquest forced their dispersal to Amsterdam, the Caribbean, and North America. Sephardic communities took root in Curaçao, Suriname, Jamaica, and Barbados, later joined by Ashkenazi migrants. In North America, Jews were present from the mid-17th century, with New Amsterdam hosting the first organized congregation in 1654. By the time of the American Revolution, small communities in New York, Newport, Philadelphia, Savannah, and Charleston played an active role in the struggle for independence. In the late 19th century, Jews in Western Europe gradually achieved legal emancipation, though social acceptance remained limited by persistent antisemitism and rising nationalism. In Eastern Europe, particularly within the Russian Empire's Pale of Settlement, Jews faced mounting legal restrictions and recurring pogroms. From this environment emerged Zionism, a national revival movement originating in Central and Eastern Europe that sought to re-establish a Jewish polity in the Land of Israel as a means of returning the Jewish people to their ancestral homeland and ending centuries of exile and persecution. This led to waves of Jewish migration to Ottoman-controlled Palestine. Theodor Herzl, who is considered the father of political Zionism, offered his vision of a future Jewish state in his 1896 book Der Judenstaat (The Jewish State); a year later, he presided over the First Zionist Congress. The antisemitism that inflicted Jewish communities in Europe also triggered a mass exodus of 2.8 million Jews to the United States between 1881 and 1924. Despite this, some Jews of Europe and the United States were able to make great achievements in various fields of science and culture. Among the most influential from this period are Albert Einstein in physics, Sigmund Freud in psychology, Franz Kafka in literature, and Irving Berlin in music. Many Nobel Prize winners at this time were Jewish, as is still the case. When Adolf Hitler and the Nazi Party came to power in Germany in 1933, the situation for Jews deteriorated rapidly as a direct result of Nazi policies. Many Jews fled from Europe to Mandatory Palestine, the United States, and the Soviet Union as a result of racial anti-Semitic laws, economic difficulties, and the fear of an impending war. World War II started in 1939, and by 1941, Hitler occupied almost all of Europe. Following the German invasion of the Soviet Union in 1941, the Final Solution—an extensive, organized effort with an unprecedented scope intended to annihilate the Jewish people—began, and resulted in the persecution and murder of Jews in Europe and North Africa. In Poland, three million were murdered in gas chambers in all concentration camps combined, with one million at the Auschwitz camp complex alone. The Holocaust is the name given to this genocide, in which six million Jews in total were systematically murdered. Before and during the Holocaust, enormous numbers of Jews immigrated to Mandatory Palestine. In 1944, the Jewish insurgency in Mandatory Palestine began with the aim of gaining full independence from the United Kingdom. On 14 May 1948, upon the termination of the mandate, David Ben-Gurion declared the creation of the State of Israel, a Jewish and democratic state. Immediately afterwards, all neighboring Arab states invaded, and were resisted by the newly formed Israel Defense Forces. In 1949, the war ended and Israel started building its state and absorbing waves of Aliyah, granting citizenship to Jews all over the world via the Law of Return passed in 1950. However, both the Israeli–Palestinian conflict and wider Arab–Israeli conflict continue to this day. Culture The Jewish people and the religion of Judaism are strongly interrelated. Converts to Judaism have a status within the Jewish people equal to those born into it. However, converts who go on to practice no Judaism are likely to be viewed with skepticism. Mainstream Judaism does not proselytize, and conversion is considered a difficult task. A significant portion of conversions are undertaken by children of mixed marriages, or would-be or current spouses of Jews. The Hebrew Bible, a religious interpretation of the traditions and early history of the Jews, established the first of the Abrahamic religions, which are now practiced by 54 percent of the world. Judaism guides its adherents in both practice and belief, and has been called not only a religion, but also a "way of life," which has made drawing a clear distinction between Judaism, Jewish culture, and Jewish identity rather difficult. Throughout history, in eras and places as diverse as the ancient Hellenic world, in Europe before and after The Age of Enlightenment (see Haskalah), in Islamic Spain and Portugal, in North Africa and the Middle East, India, China, or the contemporary United States and Israel, cultural phenomena have developed that are in some sense characteristically Jewish without being at all specifically religious. Some factors in this come from within Judaism, others from the interaction of Jews or specific communities of Jews with their surroundings, and still others from the inner social and cultural dynamics of the community, as opposed to from the religion itself. This phenomenon has led to considerably different Jewish cultures unique to their own communities. Hebrew is the liturgical language of Judaism (termed lashon ha-kodesh, "the holy tongue"), the language in which most of the Hebrew scriptures (Tanakh) were composed, and the daily speech of the Jewish people for centuries. By the 5th century BCE, Aramaic, a closely related tongue, joined Hebrew as the spoken language in Judea. By the 3rd century BCE, some Jews of the diaspora were speaking Greek. Others, such as in the Jewish communities of Asoristan, known to Jews as Babylonia, were speaking Hebrew and Aramaic, the languages of the Babylonian Talmud. Dialects of these same languages were also used by the Jews of Syria Palaestina at that time.[citation needed] For centuries, Jews worldwide have spoken the local or dominant languages of the regions they migrated to, often developing distinctive dialectal forms or branches that became independent languages. Yiddish is the Judaeo-German language developed by Ashkenazi Jews who migrated to Central Europe. Ladino is the Judaeo-Spanish language developed by Sephardic Jews who migrated to the Iberian Peninsula. Due to many factors, including the impact of the Holocaust on European Jewry, the Jewish exodus from Arab and Muslim countries, and widespread emigration from other Jewish communities around the world, ancient and distinct Jewish languages of several communities, including Judaeo-Georgian, Judaeo-Arabic, Judaeo-Berber, Krymchak, Judaeo-Malayalam and many others, have largely fallen out of use. For over sixteen centuries Hebrew was used almost exclusively as a liturgical language, and as the language in which most books had been written on Judaism, with a few speaking only Hebrew on the Sabbath. Hebrew was revived as a spoken language by Eliezer ben Yehuda, who arrived in Palestine in 1881. It had not been used as a mother tongue since Tannaic times. Modern Hebrew is designated as the "State language" of Israel. Despite efforts to revive Hebrew as the national language of the Jewish people, knowledge of the language is not commonly possessed by Jews worldwide and English has emerged as the lingua franca of the Jewish diaspora. Although many Jews once had sufficient knowledge of Hebrew to study the classic literature, and Jewish languages like Yiddish and Ladino were commonly used as recently as the early 20th century, most Jews lack such knowledge today and English has by and large superseded most Jewish vernaculars. The three most commonly spoken languages among Jews today are Hebrew, English, and Russian. Some Romance languages, particularly French and Spanish, are also widely used. Yiddish has been spoken by more Jews in history than any other language, but it is far less used today following the Holocaust and the adoption of Modern Hebrew by the Zionist movement and the State of Israel. In some places, the mother language of the Jewish community differs from that of the general population or the dominant group. For example, in Quebec, the Ashkenazic majority has adopted English, while the Sephardic minority uses French as its primary language. Similarly, South African Jews adopted English rather than Afrikaans. Due to both Czarist and Soviet policies, Russian has superseded Yiddish as the language of Russian Jews, but these policies have also affected neighboring communities. Today, Russian is the first language for many Jewish communities in a number of Post-Soviet states, such as Ukraine and Uzbekistan,[better source needed] as well as for Ashkenazic Jews in Azerbaijan, Georgia, and Tajikistan. Although communities in North Africa today are small and dwindling, Jews there had shifted from a multilingual group to a monolingual one (or nearly so), speaking French in Algeria, Morocco, and the city of Tunis, while most North Africans continue to use Arabic or Berber as their mother tongue.[citation needed] There is no single governing body for the Jewish community, nor a single authority with responsibility for religious doctrine. Instead, a variety of secular and religious institutions at the local, national, and international levels lead various parts of the Jewish community on a variety of issues. Today, many countries have a Chief Rabbi who serves as a representative of that country's Jewry. Although many Hasidic Jews follow a certain hereditary Hasidic dynasty, there is no one commonly accepted leader of all Hasidic Jews. Many Jews believe that the Messiah will act a unifying leader for Jews and the entire world. A number of modern scholars of nationalism support the existence of Jewish national identity in antiquity. One of them is David Goodblatt, who generally believes in the existence of nationalism before the modern period. In his view, the Bible, the parabiblical literature and the Jewish national history provide the base for a Jewish collective identity. Although many of the ancient Jews were illiterate (as were their neighbors), their national narrative was reinforced through public readings. The Hebrew language also constructed and preserved national identity. Although it was not widely spoken after the 5th century BCE, Goodblatt states: the mere presence of the language in spoken or written form could invoke the concept of a Jewish national identity. Even if one knew no Hebrew or was illiterate, one could recognize that a group of signs was in Hebrew script. ... It was the language of the Israelite ancestors, the national literature, and the national religion. As such it was inseparable from the national identity. Indeed its mere presence in visual or aural medium could invoke that identity. Anthony D. Smith, an historical sociologist considered one of the founders of the field of nationalism studies, wrote that the Jews of the late Second Temple period provide "a closer approximation to the ideal type of the nation [...] than perhaps anywhere else in the ancient world." He adds that this observation "must make us wary of pronouncing too readily against the possibility of the nation, and even a form of religious nationalism, before the onset of modernity." Agreeing with Smith, Goodblatt suggests omitting the qualifier "religious" from Smith's definition of ancient Jewish nationalism, noting that, according to Smith, a religious component in national memories and culture is common even in the modern era. This view is echoed by political scientist Tom Garvin, who writes that "something strangely like modern nationalism is documented for many peoples in medieval times and in classical times as well," citing the ancient Jews as one of several "obvious examples", alongside the classical Greeks and the Gaulish and British Celts. Fergus Millar suggests that the sources of Jewish national identity and their early nationalist movements in the first and second centuries CE included several key elements: the Bible as both a national history and legal source, the Hebrew language as a national language, a system of law, and social institutions such as schools, synagogues, and Sabbath worship. Adrian Hastings argued that Jews are the "true proto-nation", that through the model of ancient Israel found in the Hebrew Bible, provided the world with the original concept of nationhood which later influenced Christian nations. However, following Jerusalem's destruction in the first century CE, Jews ceased to be a political entity and did not resemble a traditional nation-state for almost two millennia. Despite this, they maintained their national identity through collective memory, religion and sacred texts, even without land or political power, and remained a nation rather than just an ethnic group, eventually leading to the rise of Zionism and the establishment of Israel. Steven Weitzman suggests that Jewish nationalist sentiment in antiquity was encouraged because under foreign rule (Persians, Greeks, Romans) Jews were able to claim that they were an ancient nation. This claim was based on the preservation and reverence of their scriptures, the Hebrew language, the Temple and priesthood, and other traditions of their ancestors. Doron Mendels further observes that the Hasmonean kingdom, one of the few examples of indigenous statehood at its time, significantly reinforced Jewish national consciousness. The memory of this period of independence contributed to the persistent efforts to revive Jewish sovereignty in Judea, leading to the major revolts against Roman rule in the 1st and 2nd centuries CE. Demographics Within the world's Jewish population there are distinct ethnic divisions, most of which are primarily the result of geographic branching from an originating Israelite population, and subsequent independent evolutions. An array of Jewish communities was established by Jewish settlers in various places around the Old World, often at great distances from one another, resulting in effective and often long-term isolation. During the millennia of the Jewish diaspora the communities would develop under the influence of their local environments: political, cultural, natural, and populational. Today, manifestations of these differences among the Jews can be observed in Jewish cultural expressions of each community, including Jewish linguistic diversity, culinary preferences, liturgical practices, religious interpretations, as well as degrees and sources of genetic admixture. Jews are often identified as belonging to one of two major groups: the Ashkenazim and the Sephardim. Ashkenazim are so named in reference to their geographical origins (their ancestors' culture coalesced in the Rhineland, an area historically referred to by Jews as Ashkenaz). Similarly, Sephardim (Sefarad meaning "Spain" in Hebrew) are named in reference their origins in Iberia. The diverse groups of Jews of the Middle East and North Africa are often collectively referred to as Sephardim together with Sephardim proper for liturgical reasons having to do with their prayer rites. A common term for many of these non-Spanish Jews who are sometimes still broadly grouped as Sephardim is Mizrahim (lit. 'easterners' in Hebrew). Nevertheless, Mizrahis and Sepharadim are usually ethnically distinct. Smaller groups include, but are not restricted to, Indian Jews such as the Bene Israel, Bnei Menashe, Cochin Jews, and Bene Ephraim; the Romaniotes of Greece; the Italian Jews ("Italkim" or "Bené Roma"); the Teimanim from Yemen; various African Jews, including most numerously the Beta Israel of Ethiopia; and Chinese Jews, most notably the Kaifeng Jews, as well as various other distinct but now almost extinct communities. The divisions between all these groups are approximate and their boundaries are not always clear. The Mizrahim for example, are a heterogeneous collection of North African, Central Asian, Caucasian, and Middle Eastern Jewish communities that are no closer related to each other than they are to any of the earlier mentioned Jewish groups. In modern usage, however, the Mizrahim are sometimes termed Sephardi due to similar styles of liturgy, despite independent development from Sephardim proper. Thus, among Mizrahim there are Egyptian Jews, Iraqi Jews, Lebanese Jews, Kurdish Jews, Moroccan Jews, Libyan Jews, Syrian Jews, Bukharian Jews, Mountain Jews, Georgian Jews, Iranian Jews, Afghan Jews, and various others. The Teimanim from Yemen are sometimes included, although their style of liturgy is unique and they differ in respect to the admixture found among them to that found in Mizrahim. In addition, there is a differentiation made between Sephardi migrants who established themselves in the Middle East and North Africa after the expulsion of the Jews from Spain and Portugal in the 1490s and the pre-existing Jewish communities in those regions. Ashkenazi Jews represent the bulk of modern Jewry, with at least 70 percent of Jews worldwide (and up to 90 percent prior to World War II and the Holocaust). As a result of their emigration from Europe, Ashkenazim also represent the overwhelming majority of Jews in the New World continents, in countries such as the United States, Canada, Argentina, Australia, and Brazil. In France, the immigration of Jews from Algeria (Sephardim) has led them to outnumber the Ashkenazim. Only in Israel is the Jewish population representative of all groups, a melting pot independent of each group's proportion within the overall world Jewish population. Y DNA studies tend to imply a small number of founders in an old population whose members parted and followed different migration paths. In most Jewish populations, these male line ancestors appear to have been mainly Middle Eastern. For example, Ashkenazi Jews share more common paternal lineages with other Jewish and Middle Eastern groups than with non-Jewish populations in areas where Jews lived in Eastern Europe, Germany, and the French Rhine Valley. This is consistent with Jewish traditions in placing most Jewish paternal origins in the region of the Middle East. Conversely, the maternal lineages of Jewish populations, studied by looking at mitochondrial DNA, are generally more heterogeneous. Scholars such as Harry Ostrer and Raphael Falk believe this indicates that many Jewish males found new mates from European and other communities in the places where they migrated in the diaspora after fleeing ancient Israel. In contrast, Behar has found evidence that about 40 percent of Ashkenazi Jews originate maternally from just four female founders, who were of Middle Eastern origin. The populations of Sephardi and Mizrahi Jewish communities "showed no evidence for a narrow founder effect." Subsequent studies carried out by Feder et al. confirmed the large portion of non-local maternal origin among Ashkenazi Jews. Reflecting on their findings related to the maternal origin of Ashkenazi Jews, the authors conclude "Clearly, the differences between Jews and non-Jews are far larger than those observed among the Jewish communities. Hence, differences between the Jewish communities can be overlooked when non-Jews are included in the comparisons." However, a 2025 genetic study on the Ashkenazi Jewish founder population supports the presence of a substantial Near Eastern component in the maternal lineages. Analyses of mitochondrial DNA (mtDNA) indicate that the core founder lineages, estimated at around 54, likely originated from the Near East, with these founder signatures appearing in multiple copies across the population. While later admixture introduced additional mtDNA lineages, these absorbed lineages are distinguishable from the original founders. The findings are consistent with genome-wide Identity-by-Descent and Lineage Extinction analyses, reinforcing the Near Eastern origin of the Ashkenazi maternal founders. A study showed that 7% of Ashkenazi Jews have the haplogroup G2c, which is mainly found in Pashtuns and on lower scales all major Jewish groups, Palestinians, Syrians, and Lebanese. Studies of autosomal DNA, which look at the entire DNA mixture, have become increasingly important as the technology develops. They show that Jewish populations have tended to form relatively closely related groups in independent communities, with most in a community sharing significant ancestry in common. For Jewish populations of the diaspora, the genetic composition of Ashkenazi, Sephardic, and Mizrahi Jewish populations show a predominant amount of shared Middle Eastern ancestry. According to Behar, the most parsimonious explanation for this shared Middle Eastern ancestry is that it is "consistent with the historical formulation of the Jewish people as descending from ancient Hebrew and Israelite residents of the Levant" and "the dispersion of the people of ancient Israel throughout the Old World". North African, Italian and others of Iberian origin show variable frequencies of admixture with non-Jewish historical host populations among the maternal lines. In the case of Ashkenazi and Sephardi Jews (in particular Moroccan Jews), who are closely related, the source of non-Jewish admixture is mainly Southern European, while Mizrahi Jews show evidence of admixture with other Middle Eastern populations. Behar et al. have remarked on a close relationship between Ashkenazi Jews and modern Italians. A 2001 study found that Jews were more closely related to groups of the Fertile Crescent (Kurds, Turks, and Armenians) than to their Arab neighbors, whose genetic signature was found in geographic patterns reflective of Islamic conquests. The studies also show that Sephardic Bnei Anusim (descendants of the "anusim" who were forced to convert to Catholicism), which comprise up to 19.8 percent of the population of today's Iberia (Spain and Portugal) and at least 10 percent of the population of Ibero-America (Hispanic America and Brazil), have Sephardic Jewish ancestry within the last few centuries. The Bene Israel and Cochin Jews of India, Beta Israel of Ethiopia, and a portion of the Lemba people of Southern Africa, despite more closely resembling the local populations of their native countries, have also been thought to have some more remote ancient Jewish ancestry. Views on the Lemba have changed and genetic Y-DNA analyses in the 2000s have established a partially Middle-Eastern origin for a portion of the male Lemba population but have been unable to narrow this down further. Although historically, Jews have been found all over the world, in the decades since World War II and the establishment of Israel, they have increasingly concentrated in a small number of countries. In 2021, Israel and the United States together accounted for over 85 percent of the global Jewish population, with approximately 45.3% and 39.6% of the world's Jews, respectively. More than half (51.2%) of world Jewry resides in just ten metropolitan areas. As of 2021, these ten areas were Tel Aviv, New York, Jerusalem, Haifa, Los Angeles, Miami, Philadelphia, Paris, Washington, and Chicago. The Tel Aviv metro area has the highest percent of Jews among the total population (94.8%), followed by Jerusalem (72.3%), Haifa (73.1%), and Beersheba (60.4%), the balance mostly being Israeli Arabs. Outside Israel, the highest percent of Jews in a metropolitan area was in New York (10.8%), followed by Miami (8.7%), Philadelphia (6.8%), San Francisco (5.1%), Washington (4.7%), Los Angeles (4.7%), Toronto (4.5%), and Baltimore (4.1%). As of 2010, there were nearly 14 million Jews around the world, roughly 0.2% of the world's population at the time. According to the 2007 estimates of The Jewish People Policy Planning Institute, the world's Jewish population is 13.2 million. This statistic incorporates both practicing Jews affiliated with synagogues and the Jewish community, and approximately 4.5 million unaffiliated and secular Jews.[citation needed] According to Sergio Della Pergola, a demographer of the Jewish population, in 2021 there were about 6.8 million Jews in Israel, 6 million in the United States, and 2.3 million in the rest of the world. Israel, the Jewish nation-state, is the only country in which Jews make up a majority of the citizens. Israel was established as an independent democratic and Jewish state on 14 May 1948. Of the 120 members in its parliament, the Knesset, as of 2016[update], 14 members of the Knesset are Arab citizens of Israel (not including the Druze), most representing Arab political parties. One of Israel's Supreme Court judges is also an Arab citizen of Israel. Between 1948 and 1958, the Jewish population rose from 800,000 to two million. Currently, Jews account for 75.4 percent of the Israeli population, or 6 million people. The early years of the State of Israel were marked by the mass immigration of Holocaust survivors in the aftermath of the Holocaust and Jews fleeing Arab lands. Israel also has a large population of Ethiopian Jews, many of whom were airlifted to Israel in the late 1980s and early 1990s. Between 1974 and 1979 nearly 227,258 immigrants arrived in Israel, about half being from the Soviet Union. This period also saw an increase in immigration to Israel from Western Europe, Latin America, and North America. A trickle of immigrants from other communities has also arrived, including Indian Jews and others, as well as some descendants of Ashkenazi Holocaust survivors who had settled in countries such as the United States, Argentina, Australia, Chile, and South Africa. Some Jews have emigrated from Israel elsewhere, because of economic problems or disillusionment with political conditions and the continuing Arab–Israeli conflict. Jewish Israeli emigrants are known as yordim. The waves of immigration to the United States and elsewhere at the turn of the 19th century, the founding of Zionism and later events, including pogroms in Imperial Russia (mostly within the Pale of Settlement in present-day Ukraine, Moldova, Belarus and eastern Poland), the massacre of European Jewry during the Holocaust, and the founding of the state of Israel, with the subsequent Jewish exodus from Arab lands, all resulted in substantial shifts in the population centers of world Jewry by the end of the 20th century. More than half of the Jews live in the Diaspora (see Population table). Currently, the largest Jewish community outside Israel, and either the largest or second-largest Jewish community in the world, is located in the United States, with 6 million to 7.5 million Jews by various estimates. Elsewhere in the Americas, there are also large Jewish populations in Canada (315,000), Argentina (180,000–300,000), and Brazil (196,000–600,000), and smaller populations in Mexico, Uruguay, Venezuela, Chile, Colombia and several other countries (see History of the Jews in Latin America). According to a 2010 Pew Research Center study, about 470,000 people of Jewish heritage live in Latin America and the Caribbean. Demographers disagree on whether the United States has a larger Jewish population than Israel, with many maintaining that Israel surpassed the United States in Jewish population during the 2000s, while others maintain that the United States still has the largest Jewish population in the world. Currently, a major national Jewish population survey is planned to ascertain whether or not Israel has overtaken the United States in Jewish population. Western Europe's largest Jewish community, and the third-largest Jewish community in the world, can be found in France, home to between 483,000 and 500,000 Jews, the majority of whom are immigrants or refugees from North African countries such as Algeria, Morocco, and Tunisia (or their descendants). The United Kingdom has a Jewish community of 292,000. In Eastern Europe, the exact figures are difficult to establish. The number of Jews in Russia varies widely according to whether a source uses census data (which requires a person to choose a single nationality among choices that include "Russian" and "Jewish") or eligibility for immigration to Israel (which requires that a person have one or more Jewish grandparents). According to the latter criteria, the heads of the Russian Jewish community assert that up to 1.5 million Russians are eligible for aliyah. In Germany, the 102,000 Jews registered with the Jewish community are a slowly declining population, despite the immigration of tens of thousands of Jews from the former Soviet Union since the fall of the Berlin Wall. Thousands of Israelis also live in Germany, either permanently or temporarily, for economic reasons. Prior to 1948, approximately 800,000 Jews were living in lands which now make up the Arab world (excluding Israel). Of these, just under two-thirds lived in the French-controlled Maghreb region, 15 to 20 percent in the Kingdom of Iraq, approximately 10 percent in the Kingdom of Egypt and approximately 7 percent in the Kingdom of Yemen. A further 200,000 lived in Pahlavi Iran and the Republic of Turkey. Today, around 26,000 Jews live in Muslim-majority countries, mainly in Turkey (14,200) and Iran (9,100), while Morocco (2,000), Tunisia (1,000), and the United Arab Emirates (500) host the largest communities in the Arab world. A small-scale exodus had begun in many countries in the early decades of the 20th century, although the only substantial aliyah came from Yemen and Syria. The exodus from Arab and Muslim countries took place primarily from 1948. The first large-scale exoduses took place in the late 1940s and early 1950s, primarily in Iraq, Yemen and Libya, with up to 90 percent of these communities leaving within a few years. The peak of the exodus from Egypt occurred in 1956. The exodus in the Maghreb countries peaked in the 1960s. Lebanon was the only Arab country to see a temporary increase in its Jewish population during this period, due to an influx of refugees from other Arab countries, although by the mid-1970s the Jewish community of Lebanon had also dwindled. In the aftermath of the exodus wave from Arab states, an additional migration of Iranian Jews peaked in the 1980s when around 80 percent of Iranian Jews left the country.[citation needed] Outside Europe, the Americas, the Middle East, and the rest of Asia, there are significant Jewish populations in Australia (112,500) and South Africa (70,000). There is also a 6,800-strong community in New Zealand. Since at least the time of the Ancient Greeks, a proportion of Jews have assimilated into the wider non-Jewish society around them, by either choice or force, ceasing to practice Judaism and losing their Jewish identity. Assimilation took place in all areas, and during all time periods, with some Jewish communities, for example the Kaifeng Jews of China, disappearing entirely. The advent of the Jewish Enlightenment of the 18th century (see Haskalah) and the subsequent emancipation of the Jewish populations of Europe and America in the 19th century, accelerated the situation, encouraging Jews to increasingly participate in, and become part of, secular society. The result has been a growing trend of assimilation, as Jews marry non-Jewish spouses and stop participating in the Jewish community. Rates of interreligious marriage vary widely: In the United States, it is just under 50 percent; in the United Kingdom, around 53 percent; in France, around 30 percent; and in Australia and Mexico, as low as 10 percent. In the United States, only about a third of children from intermarriages affiliate with Jewish religious practice. The result is that most countries in the Diaspora have steady or slightly declining religiously Jewish populations as Jews continue to assimilate into the countries in which they live.[citation needed] The Jewish people and Judaism have experienced various persecutions throughout their history. During Late Antiquity and the Early Middle Ages, the Roman Empire (in its later phases known as the Byzantine Empire) repeatedly repressed the Jewish population, first by ejecting them from their homelands during the pagan Roman era and later by officially establishing them as second-class citizens during the Christian Roman era. According to James Carroll, "Jews accounted for 10% of the total population of the Roman Empire. By that ratio, if other factors had not intervened, there would be 200 million Jews in the world today, instead of something like 13 million." Later in medieval Western Europe, further persecutions of Jews by Christians occurred, notably during the Crusades—when Jews all over Germany were massacred—and in a series of expulsions from the Kingdom of England, Germany, and France. Then there occurred the largest expulsion of all, when Spain and Portugal, after the Reconquista (the Catholic Reconquest of the Iberian Peninsula), expelled both unbaptized Sephardic Jews and the ruling Muslim Moors. In the Papal States, which existed until 1870, Jews were required to live only in specified neighborhoods called ghettos. Islam and Judaism have a complex relationship. Traditionally Jews and Christians living in Muslim lands, known as dhimmis, were allowed to practice their religions and administer their internal affairs, but they were subject to certain conditions. They had to pay the jizya (a per capita tax imposed on free adult non-Muslim males) to the Islamic state. Dhimmis had an inferior status under Islamic rule. They had several social and legal disabilities such as prohibitions against bearing arms or giving testimony in courts in cases involving Muslims. Many of the disabilities were highly symbolic. The one described by Bernard Lewis as "most degrading" was the requirement of distinctive clothing, not found in the Quran or hadith but invented in early medieval Baghdad; its enforcement was highly erratic. On the other hand, Jews rarely faced martyrdom or exile, or forced compulsion to change their religion, and they were mostly free in their choice of residence and profession. Notable exceptions include the massacre of Jews and forcible conversion of some Jews by the rulers of the Almohad dynasty in Al-Andalus in the 12th century, as well as in Islamic Persia, and the forced confinement of Moroccan Jews to walled quarters known as mellahs beginning from the 15th century and especially in the early 19th century. In modern times, it has become commonplace for standard antisemitic themes to be conflated with anti-Zionist publications and pronouncements of Islamic movements such as Hezbollah and Hamas, in the pronouncements of various agencies of the Islamic Republic of Iran, and even in the newspapers and other publications of Turkish Refah Partisi."[better source needed] Throughout history, many rulers, empires and nations have oppressed their Jewish populations or sought to eliminate them entirely. Methods employed ranged from expulsion to outright genocide; within nations, often the threat of these extreme methods was sufficient to silence dissent. The history of antisemitism includes the First Crusade which resulted in the massacre of Jews; the Spanish Inquisition (led by Tomás de Torquemada) and the Portuguese Inquisition, with their persecution and autos-da-fé against the New Christians and Marrano Jews; the Bohdan Chmielnicki Cossack massacres in Ukraine; the Pogroms backed by the Russian Tsars; as well as expulsions from Spain, Portugal, England, France, Germany, and other countries in which the Jews had settled. According to a 2008 study published in the American Journal of Human Genetics, 19.8 percent of the modern Iberian population has Sephardic Jewish ancestry, indicating that the number of conversos may have been much higher than originally thought. The persecution reached a peak in Nazi Germany's Final Solution, which led to the Holocaust and the slaughter of approximately 6 million Jews. Of the world's 16 million Jews in 1939, almost 40% were murdered in the Holocaust. The Holocaust—the state-led systematic persecution and genocide of European Jews (and certain communities of North African Jews in European controlled North Africa) and other minority groups of Europe during World War II by Germany and its collaborators—remains the most notable modern-day persecution of Jews. The persecution and genocide were accomplished in stages. Legislation to remove the Jews from civil society was enacted years before the outbreak of World War II. Concentration camps were established in which inmates were used as slave labour until they died of exhaustion or disease. Where the Third Reich conquered new territory in Eastern Europe, specialized units called Einsatzgruppen murdered Jews and political opponents in mass shootings. Jews and Roma were crammed into ghettos before being transported hundreds of kilometres by freight train to extermination camps where, if they survived the journey, the majority of them were murdered in gas chambers. Virtually every arm of Germany's bureaucracy was involved in the logistics of the mass murder, turning the country into what one Holocaust scholar has called "a genocidal nation." Throughout Jewish history, Jews have repeatedly been directly or indirectly expelled from both their original homeland, the Land of Israel, and many of the areas in which they have settled. This experience as refugees has shaped Jewish identity and religious practice in many ways, and is thus a major element of Jewish history. In summary, the pogroms in Eastern Europe, the rise of modern antisemitism, the Holocaust, as well as the rise of Arab nationalism, all served to fuel the movements and migrations of huge segments of Jewry from land to land and continent to continent until they arrived back in large numbers at their original historical homeland in Israel. In the Bible, the patriarch Abraham is described as a migrant to the land of Canaan from Ur of the Chaldees. His descendants, the Children of Israel, undertook the Exodus (meaning "departure" or "exit" in Greek) from ancient Egypt, as described in the Book of Exodus. The first movement documented in the historical record occurred with the resettlement policy of the Neo-Assyrian Empire, which mandated the deportation of conquered peoples, and it is estimated some 4,500,000 among its captive populations suffered this dislocation over three centuries of Assyrian rule. With regard to Israel, Tiglath-Pileser III claims he deported 80% of the population of Lower Galilee, some 13,520 people. Some 27,000 Israelites, 20 to 25% of the population of the Kingdom of Israel, were described as being deported by Sargon II, and were replaced by other deported populations and sent into permanent exile by Assyria, initially to the Upper Mesopotamian provinces of the Assyrian Empire. Between 10,000 and 80,000 people from the Kingdom of Judah were similarly exiled by Babylonia, but these people were then returned to Judea by Cyrus the Great of the Persian Achaemenid Empire. Many Jews were exiled again by the Roman Empire. The 2,000 year dispersion of the Jewish diaspora beginning under the Roman Empire, as Jews were spread throughout the Roman world and, driven from land to land, settled wherever they could live freely enough to practice their religion. Over the course of the diaspora the center of Jewish life moved from Babylonia to the Iberian Peninsula to Poland to the United States and, as a result of Zionism, back to Israel. There were also many expulsions of Jews during the Middle Ages and Enlightenment in Europe, including: 1290, 16,000 Jews were expelled from England, (see the Statute of Jewry); in 1396, 100,000 from France; in 1421, thousands were expelled from Austria. Many of these Jews settled in East-Central Europe, especially Poland. Following the Spanish Inquisition in 1492, the Spanish population of around 200,000 Sephardic Jews were expelled by the Spanish crown and Catholic church, followed by expulsions in 1493 in Sicily (37,000 Jews) and Portugal in 1496. The expelled Jews fled mainly to the Ottoman Empire, the Netherlands, and North Africa, others migrating to Southern Europe and the Middle East. During the 19th century, France's policies of equal citizenship regardless of religion led to the immigration of Jews (especially from Eastern and Central Europe). This contributed to the arrival of millions of Jews in the New World. Over two million Eastern European Jews arrived in the United States from 1880 to 1925. In the latest phase of migrations, the Islamic Revolution of Iran caused many Iranian Jews to flee Iran. Most found refuge in the US (particularly Los Angeles, California, and Long Island, New York) and Israel. Smaller communities of Persian Jews exist in Canada and Western Europe. Similarly, when the Soviet Union collapsed, many of the Jews in the affected territory (who had been refuseniks) were suddenly allowed to leave. This produced a wave of migration to Israel in the early 1990s. Israel is the only country with a Jewish population that is consistently growing through natural population growth, although the Jewish populations of other countries, in Europe and North America, have recently increased through immigration. In the Diaspora, in almost every country the Jewish population in general is either declining or steady, but Orthodox and Haredi Jewish communities, whose members often shun birth control for religious reasons, have experienced rapid population growth. Orthodox and Conservative Judaism discourage proselytism to non-Jews, but many Jewish groups have tried to reach out to the assimilated Jewish communities of the Diaspora in order for them to reconnect to their Jewish roots. Additionally, while in principle Reform Judaism favours seeking new members for the faith, this position has not translated into active proselytism, instead taking the form of an effort to reach out to non-Jewish spouses of intermarried couples. There is also a trend of Orthodox movements reaching out to secular Jews in order to give them a stronger Jewish identity so there is less chance of intermarriage. As a result of the efforts by these and other Jewish groups over the past 25 years, there has been a trend (known as the Baal teshuva movement) for secular Jews to become more religiously observant, though the demographic implications of the trend are unknown. Additionally, there is also a growing rate of conversion to Jews by Choice of gentiles who make the decision to head in the direction of becoming Jews. Contributions Jewish individuals have played a significant role in the development and growth of Western culture, advancing many fields of thought, science and technology, both historically and in modern times, including through discrete trends in Jewish philosophy, Jewish ethics and Jewish literature, as well as specific trends in Jewish culture, including in Jewish art, Jewish music, Jewish humor, Jewish theatre, Jewish cuisine and Jewish medicine. Jews have established various Jewish political movements, religious movements, and, through the authorship of the Hebrew Bible and parts of the New Testament, provided the foundation for Christianity and Islam. More than 20 percent of the awarded Nobel Prize have gone to individuals of Jewish descent. Philanthropic giving is a widespread core function among Jewish organizations. Notes References External links |
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Contents Bivalvia And see text Bivalvia (/baɪˈvælviə/) or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed by a calcified exoskeleton consisting of a hinged pair of half-shells known as valves. As a group, bivalves have no head and lack some typical molluscan organs such as the radula and the odontophore. Their gills have evolved into ctenidia, specialised organs for feeding and breathing. Common bivalves include clams, oysters, cockles, mussels, scallops, and numerous other families that live in saltwater, as well as a number of families that live in freshwater. Majority of the class are benthic filter feeders that bury themselves in sediment, where they are relatively safe from predation. Others lie on the sea floor or attach themselves to rocks or other hard surfaces. Some bivalves, such as scallops and file shells, can swim. Shipworms bore into wood, clay, or stone and live inside these substances. The shell of a bivalve is composed of calcium carbonate, and consists of two, usually similar, parts called valves. These valves are for feeding and for disposal of waste. These are joined together along one edge (the hinge line) by a flexible ligament that, usually in conjunction with interlocking "teeth" on each of the valves, forms the hinge. This arrangement allows the shell to be opened and closed without the two halves detaching. The shell is typically bilaterally symmetrical, with the hinge lying in the sagittal plane. Adult shell sizes of bivalves vary from fractions of a millimetre to over a metre in length, but the majority of species do not exceed 10 cm (4 in). Bivalves have long been a part of the diet of coastal and riparian human populations. Oysters were cultured in ponds by the Romans, and mariculture has more recently become an important source of bivalves for food. Modern knowledge of molluscan reproductive cycles has led to the development of hatcheries and new culture techniques. A better understanding of the potential hazards of eating raw or undercooked shellfish has led to improved storage and processing. Pearl oysters (the common name of two very different families in salt water and fresh water) are the most common source of natural pearls. The shells of bivalves are used in craftwork, and the manufacture of jewellery and buttons. Bivalves have also been used in the biocontrol of pollution. Bivalves appear in the fossil record first in the early Cambrian more than 500 million years ago. The total number of known living species is about 9,200. These species are placed within 1,260 genera and 106 families. Marine bivalves (including brackish water and estuarine species) represent about 8,000 species, combined in four subclasses and 99 families with 1,100 genera. The largest recent marine families are the Veneridae, with more than 680 species and the Tellinidae and Lucinidae, each with over 500 species. The freshwater bivalves include seven families, the largest of which are the Unionidae, with about 700 species. Etymology The taxonomic term Bivalvia was first used by Linnaeus in the 10th edition of his Systema Naturae in 1758 to refer to animals having shells composed of two valves. More recently, the class was known as Pelecypoda, meaning "axe-foot" (based on the shape of the foot of the animal when extended). The name "bivalve" is derived from the Latin bis, meaning 'two', and valvae, meaning 'leaves of a door' ("leaf" is an older word for the main, movable part of a door; we normally consider this the door itself). Paired shells have evolved independently several times among animals that are not bivalves; other animals with paired valves include certain gastropods (small sea snails in the family Juliidae), members of the phylum Brachiopoda and the minute crustaceans known as ostracods and conchostracans. Anatomy Bivalves have bilaterally symmetrical and laterally flattened bodies, with a blade-shaped foot, vestigial head and no radula. At the dorsal or back region of the shell is the hinge point or line, which contain the umbo and beak and the lower, curved margin is the ventral or underside region. The anterior or front of the shell is where the byssus (when present) and foot are located, and the posterior of the shell is where the siphons are located. With the hinge uppermost and with the anterior edge of the animal towards the viewer's left, the valve facing the viewer is the left valve and the opposing valve the right. Many bivalves such as clams, which appear upright, are evolutionarily lying on their side. The shell is composed of two calcareous valves held together by a ligament. The valves are made of either calcite, as is the case in oysters, or both calcite and aragonite. Sometimes, the aragonite forms an inner, nacreous layer, as is the case in the order Pteriida. In other taxa, alternate layers of calcite and aragonite are laid down. The ligament and byssus, if calcified, are composed of aragonite. The outermost layer of the shell is the periostracum, a thin layer composed of horny conchiolin. The periostracum is secreted by the outer mantle and is easily abraded. The outer surface of the valves is often sculpted, with clams often having concentric striations, scallops having radial ribs and oysters a latticework of irregular markings. In all molluscs, the mantle forms a thin membrane that covers the animal's body and extends out from it in flaps or lobes. In bivalves, the mantle lobes secrete the valves, and the mantle crest secretes the whole hinge mechanism consisting of ligament, byssus threads (where present), and teeth. The posterior mantle edge may have two elongated extensions known as siphons, through one of which water is inhaled, and the other expelled. The siphons retract into a cavity, known as the pallial sinus. The shell grows larger when more material is secreted by the mantle edge, and the valves themselves thicken as more material is secreted from the general mantle surface. Calcareous matter comes from both its diet and the surrounding seawater. Concentric rings on the exterior of a valve are commonly used to age bivalves. For some groups, a more precise method for determining the age of a shell is by cutting a cross section through it and examining the incremental growth bands. The shipworms, in the family Teredinidae have greatly elongated bodies, but their shell valves are much reduced and restricted to the anterior end of the body, where they function as scraping organs that permit the animal to dig tunnels through wood. The main muscular system in bivalves is the posterior and anterior adductor muscles. These muscles connect the two valves and contract to close the shell. The valves are also joined dorsally by the hinge ligament, which is an extension of the periostracum. The ligament is responsible for opening the shell, and works against the adductor muscles when the animal opens and closes. Retractor muscles connect the mantle to the edge of the shell, along a line known as the pallial line. These muscles pull the mantle though the valves. In sedentary or recumbent bivalves that lie on one valve, such as the oysters and scallops, the anterior adductor muscle has been lost and the posterior muscle is positioned centrally. In species that can swim by flapping their valves, a single, central adductor muscle occurs. These muscles are composed of two types of muscle fibres, striated muscle bundles for fast actions and smooth muscle bundles for maintaining a steady pull. Paired pedal protractor and retractor muscles operate the animal's foot. The sedentary habits of the bivalves have meant that in general the nervous system is less complex than in most other molluscs. The animals have no brain; the nervous system consists of a nerve network and a series of paired ganglia. In all but the most primitive bivalves, two cerebropleural ganglia are on either side of the oesophagus. The cerebral ganglia control the sensory organs, while the pleural ganglia supply nerves to the mantle cavity. The pedal ganglia, which control the foot, are at its base, and the visceral ganglia, which can be quite large in swimming bivalves, are under the posterior adductor muscle. These ganglia are both connected to the cerebropleural ganglia by nerve fibres. Bivalves with long siphons may also have siphonal ganglia to control them. The sensory organs of bivalves are largely located on the posterior mantle margins. The organs are usually mechanoreceptors or chemoreceptors, in some cases located on short tentacles. The osphradium is a patch of sensory cells located below the posterior adductor muscle that may serve to taste the water or measure its turbidity. Statocysts within the organism help the bivalve to sense and correct its orientation. In the order Anomalodesmata, the inhalant siphon is surrounded by vibration-sensitive tentacles for detecting prey. Many bivalves have no eyes, but a few members of the Arcoidea, Limopsoidea, Mytiloidea, Anomioidea, Ostreoidea, and Limoidea have simple eyes on the margin of the mantle. These consist of a pit of photosensory cells and a lens. Scallops have more complex eyes with a lens, a two-layered retina, and a concave mirror. All bivalves have light-sensitive cells that can detect a shadow falling over the animal. Bivalves have an open circulatory system that bathes the organs in blood (hemolymph). The heart has three chambers: two auricles receiving blood from the gills, and a single ventricle. The ventricle is muscular and pumps hemolymph into the aorta, and then to the rest of the body. Some bivalves have a single aorta, but most also have a second, usually smaller, aorta serving the hind parts of the animal. The hemolymph usually lacks any respiratory pigment. In the carnivorous genus Poromya, the hemolymph has red amoebocytes containing a haemoglobin pigment. The paired gills are located posteriorly and consist of hollow tube-like filaments with thin walls for gas exchange. The respiratory demands of bivalves are low, due to their relative inactivity. Some freshwater species, when exposed to the air, can gape the shell slightly and gas exchange can take place. Oysters, including the Pacific oyster (Magallana gigas), are recognized as having varying metabolic responses to environmental stress, with changes in respiration rate being frequently observed. Most bivalves are filter feeders, using their gills to capture particulate food such as phytoplankton from the water. Protobranchs feed in a different way, scraping detritus from the seabed, and this may be the original mode of feeding used by all bivalves before the gills became adapted for filter feeding. These primitive bivalves hold on to the bottom with a pair of tentacles at the edge of the mouth, each of which has a single palp, or flap. The tentacles are covered in mucus, which traps the food, and cilia, which transport the particles back to the palps. These then sort the particles, rejecting those that are unsuitable or too large to digest, and conveying others to the mouth. In more advanced bivalves, water is drawn into the shell from the posterior ventral surface of the animal, passes upwards through the gills, and doubles back to be expelled just above the intake. There may be two elongated, retractable siphons reaching up to the seabed, one each for the inhalant and exhalant streams of water. The gills of filter-feeding bivalves are known as ctenidia and have become highly modified to increase their ability to capture food. For example, the cilia on the gills, which originally served to remove unwanted sediment, have become adapted to capture food particles, and transport them in a steady stream of mucus to the mouth. The filaments of the gills are also much longer than those in more primitive bivalves, and are folded over to create a groove through which food can be transported. The structure of the gills varies considerably, and can serve as a useful means for classifying bivalves into groups. A few bivalves, such as the granular poromya (Poromya granulata), are carnivorous, eating much larger prey than the tiny microalgae consumed by other bivalves. Muscles draw water in through the inhalant siphon which is modified into a cowl-shaped organ, sucking in prey. The siphon can be retracted quickly and inverted, bringing the prey within reach of the mouth. The gut is modified so that large food particles can be digested. The unusual genus, Entovalva, is endosymbiotic, being found only in the oesophagus of sea cucumbers. It has mantle folds that completely surround its small valves. When the sea cucumber sucks in sediment, the bivalve allows the water to pass over its gills and extracts fine organic particles. To prevent itself from being swept away, it attaches itself with byssal threads to the host's throat. The sea cucumber is unharmed. The digestive tract of typical bivalves consists of an oesophagus, stomach, and intestine. Protobranch stomachs have a mere sac attached to them while filter-feeding bivalves have elongated rod of solidified mucus referred to as the "crystalline style" projected into the stomach from an associated sac. Cilia in the sac cause the style to rotate, winding in a stream of food-containing mucus from the mouth, and churning the stomach contents. This constant motion propels food particles into a sorting region at the rear of the stomach, which distributes smaller particles into the digestive glands, and heavier particles into the intestine. Waste material is consolidated in the rectum and voided as pellets into the exhalent water stream through an anal pore. Feeding and digestion are synchronized with diurnal and tidal cycles. Carnivorous bivalves generally have reduced crystalline styles and the stomach has thick, muscular walls, extensive cuticular linings and diminished sorting areas and gastric chamber sections. The excretory organs of bivalves are a pair of nephridia. Each of these consists of a long, looped, glandular tube, which opens into the pericardium, and a bladder to store urine. They also have pericardial glands either line the auricles of the heart or attach to the pericardium, and serve as extra filtration organs. Metabolic waste is voided from the bladders through a nephridiopore near the front of the upper part of the mantle cavity and excreted. The sexes are usually separate in bivalves but some hermaphroditism is known. The gonads either open into the nephridia or through a separate pore into a chamber over the gills. The ripe gonads of males and females release sperm and eggs into the water column. Spawning may take place continually or be triggered by environmental factors such as day length, water temperature, or the presence of sperm in the water. Some species are "dribble spawners", releasing gametes during protracted period that can extend for weeks. Others are mass spawners and release their gametes in batches or all at once. Fertilization is usually external. Typically, a short stage lasts a few hours or days before the eggs hatch into trochophore larvae. These later develop into veliger larvae which settle on the seabed and undergo metamorphosis into adults. In some species, such as those in the genus Lasaea, females draw water containing sperm in through their inhalant siphons and fertilization takes place inside the female. These species then brood the young inside their mantle cavity, eventually releasing them into the water column as veliger larvae or as crawl-away juveniles. Most of the bivalve larvae that hatch from eggs in the water column feed on diatoms or other phytoplankton. In temperate regions, about 25% of species are lecithotrophic, depending on nutrients stored in the yolk of the egg where the main energy source is lipids. The longer the period is before the larva first feeds, the larger the egg and yolk need to be. The reproductive cost of producing these energy-rich eggs is high and they are usually smaller in number. For example, the Baltic tellin (Macoma balthica) produces few, high-energy eggs. The larvae hatching out of these rely on the energy reserves and do not feed. After about four days, they become D-stage larvae, when they first develop hinged, D-shaped valves. These larvae have a relatively small dispersal potential before settling out. The common mussel (Mytilus edulis) produces 10 times as many eggs that hatch into larvae and soon need to feed to survive and grow. They can disperse more widely as they remain planktonic for a much longer time. Freshwater bivalves have different lifecycle. Sperm is drawn into a female's gills with the inhalant water and internal fertilization takes place. The eggs hatch into glochidia larvae that develop within the female's shell. Later they are released and attach themselves parasitically to the gills or fins of a fish host. After several weeks they drop off their host, undergo metamorphosis and develop into adults on the substrate. Some of the species in the freshwater mussel family, Unionidae, commonly known as pocketbook mussels, have evolved an unusual reproductive strategy. The female's mantle protrudes from the shell and develops into an imitation small fish, complete with fish-like markings and false eyes. This decoy moves in the current and attracts the attention of real fish. Some fish see the decoy as prey, while others see a conspecific. They approach for a closer look and the mussel releases huge numbers of larvae from its gills, dousing the inquisitive fish with its tiny, parasitic young. These glochidia larvae are drawn into the fish's gills, where they attach and trigger a tissue response that forms a small cyst around each larva. The larvae then feed by breaking down and digesting the tissue of the fish within the cysts. After a few weeks they release themselves from the cysts and fall to the stream bed as juvenile molluscs. Comparison with brachiopods Brachiopods are shelled marine organisms that superficially resemble bivalves in that they are of similar size and have a hinged shell in two parts. However, brachiopods evolved from a very different ancestral line, and the resemblance to bivalves only arose because they occupy similar ecological niches. The differences between the two groups are due to their separate ancestral origins. Different initial structures have been adapted to solve the same problems, a case of convergent evolution. In modern times, brachiopods are not as common as bivalves. Both groups have a shell consisting of two valves, but the organization of the shell is quite different in the two groups. In brachiopods, the two valves are positioned on the dorsal and ventral surfaces of the body, while in bivalves, the valves are on the left and right sides of the body, and are, in most cases, mirror images of one other. Brachiopods have a lophophore, a coiled, rigid cartilaginous internal apparatus adapted for filter feeding, a feature shared with two other major groups of marine invertebrates, the bryozoans and the phoronids. Some brachiopod shells are made of calcium phosphate but most are calcium carbonate in the form of the biomineral calcite, whereas bivalve shells are always composed entirely of calcium carbonate, often in the form of the biomineral aragonite. Evolutionary history The Cambrian explosion took place around 540 to 520 million years ago (Mya). In this geologically brief period, most major animal phyla diverged including some of the first creatures with mineralized skeletons. Brachiopods and bivalves made their appearance at this time, and left their fossilized remains behind in the rocks. Possible early bivalves include Pojetaia and Fordilla; these probably lie in the stem rather than crown group. Watsonella and Anabarella are perceived to be (earlier) close relatives of these taxa. Only five genera of supposed Cambrian "bivalves" exist, the others being Tuarangia, Camya and Arhouriella and potentially Buluniella. Bivalve fossils can be formed when the sediment in which the shells are buried hardens into rock. Often, the impression made by the valves remains as the fossil rather than the valves. During the Early Ordovician, a great increase in the diversity of bivalve species occurred, and the dysodont, heterodont, and taxodont dentitions evolved. By the Early Silurian, the gills were becoming adapted for filter feeding, and during the Devonian and Carboniferous periods, siphons first appeared, which, with the newly developed muscular foot, allowed the animals to bury themselves deep in the sediment. By the middle of the Paleozoic, around 400 Mya, the brachiopods were among the most abundant filter feeders in the ocean, and over 12,000 fossil species are recognized. By the Permian–Triassic extinction event 250 Mya, bivalves were undergoing a huge radiation of diversity. The bivalves were hard hit by this event, but re-established themselves and thrived during the Triassic period that followed. In contrast, the brachiopods lost 95% of their species diversity. The ability of some bivalves to burrow and thus avoid predators may have been a major factor in their success. Other new adaptations within various families allowed species to occupy previously unused evolutionary niches. These included increasing relative buoyancy in soft sediments by developing spines on the shell, gaining the ability to swim, and in a few cases, adopting predatory habits. For a long time, bivalves were thought to be better adapted to aquatic life than brachiopods were, outcompeting and relegating them to minor niches in later ages. These two taxa appeared in textbooks as an example of replacement by competition. Evidence given for this included the fact that bivalves needed less food to subsist because of their energetically efficient ligament-muscle system for opening and closing valves. All this has been broadly disproven, though; rather, the prominence of modern bivalves over brachiopods seems due to chance disparities in their response to extinction events. Diversity of extant bivalves The adult maximum size of living species of bivalve ranges from 0.52 mm (0.02 in) in Condylonucula maya, a nut clam, to a length of 1,532 millimetres (60.3 in) in Kuphus polythalamia, an elongated, burrowing shipworm. However, the species generally regarded as the largest living bivalve is the giant clam Tridacna gigas, which can grow to a length of 1,200 mm (47 in) and a weight of more than 200 kg (441 lb). The largest known extinct bivalve is a species of Platyceramus whose fossils measure up to 3,000 mm (118 in) in length. In his 2010 treatise, Compendium of Bivalves, Markus Huber gives the total number of living bivalve species as about 9,200 combined in 106 families. Huber states that the number of 20,000 living species, often encountered in literature, could not be verified and presents the following table to illustrate the known diversity: Distribution The bivalves are a highly successful class of invertebrates found in aquatic habitats throughout the world. Most are infaunal and live buried in sediment on the seabed, or in the sediment in freshwater habitats. A large number of bivalve species are found in the intertidal and sublittoral zones of the oceans. A sandy sea beach may superficially appear to be devoid of life, but often a very large number of bivalves and other invertebrates are living beneath the surface of the sand. On a large beach in South Wales, careful sampling produced an estimate of 1.44 million cockles (Cerastoderma edule) per acre of beach. Bivalves inhabit the tropics, as well as temperate and boreal waters. A number of species can survive and even flourish in extreme conditions. They are abundant in the Arctic, about 140 species being known from that zone. The Antarctic scallop, Adamussium colbecki, lives under the sea ice at the other end of the globe, where the subzero temperatures mean that growth rates are very slow. The giant mussel, Bathymodiolus thermophilus, and the giant white clam, Calyptogena magnifica, both live clustered around hydrothermal vents at abyssal depths in the Pacific Ocean. They have chemosymbiotic bacteria in their gills that oxidise hydrogen sulphide, and the molluscs absorb nutrients synthesized by these bacteria. Some species are found in the hadal zone, like Vesicomya sergeevi, which occurs at depths of 7600–9530 meters. The saddle oyster, Enigmonia aenigmatica, is a marine species that could be considered amphibious. It lives above the high tide mark in the tropical Indo-Pacific on the underside of mangrove leaves, on mangrove branches, and on sea walls in the splash zone. Some freshwater bivalves have very restricted ranges. For example, the Ouachita creekshell mussel, Villosa arkansasensis, is known only from the streams of the Ouachita Mountains in Arkansas and Oklahoma, and like several other freshwater mussel species from the southeastern US, it is in danger of extinction. In contrast, a few species of freshwater bivalves, including the golden mussel (Limnoperna fortunei), are dramatically increasing their ranges. The golden mussel has spread from Southeast Asia to Argentina, where it has become an invasive species. Another well-travelled freshwater bivalve, the zebra mussel (Dreissena polymorpha) originated in southeastern Russia, and has been accidentally introduced to inland waterways in North America and Europe, where the species damages water installations and disrupts local ecosystems. Behaviour Most bivalves adopt a sedentary or even sessile lifestyle, often spending their whole lives in the area in which they first settled as juveniles. The majority of bivalves are infaunal, living under the seabed, buried in soft substrates such as sand, silt, mud, gravel, or coral fragments. Many of these live in the intertidal zone where the sediment remains damp even when the tide is out. When buried in the sediment, burrowing bivalves are protected from the pounding of waves, desiccation, and overheating during low tide, and variations in salinity caused by rainwater. They are also out of the reach of many predators. Their general strategy is to extend their siphons to the surface for feeding and respiration during high tide, but to descend to greater depths or keep their shell tightly shut when the tide goes out. They use their muscular foot to dig into the substrate. To do this, the animal relaxes its adductor muscles and opens its shell wide to anchor itself in position while it extends its foot downwards into the substrate. Then it dilates the tip of its foot, retracts the adductor muscles to close the shell, shortens its foot and draws itself downwards. This series of actions is repeated to dig deeper. Other bivalves, such as mussels, attach themselves to hard surfaces using tough byssus threads made of collagen and elastin proteins. Some species, including the true oysters, the jewel boxes, the jingle shells, the thorny oysters and the kitten's paws, cement themselves to stones, rock or larger dead shells. In oysters, the lower valve may be almost flat while the upper valve develops layer upon layer of thin horny material reinforced with calcium carbonate. Oysters sometimes occur in dense beds in the neritic zone and, like most bivalves, are filter feeders. Bivalves filter large amounts of water to feed and breathe but they are not permanently open. They regularly shut their valves to enter a resting state, even when they are permanently submerged. In oysters, for example, their behaviour follows very strict circatidal and circadian rhythms according to the relative positions of the moon and sun. During neap tides, they exhibit much longer closing periods than during spring tides. Although many non-sessile bivalves use their muscular foot to move around, or to dig, members of the freshwater family Sphaeriidae are exceptional in that these small clams climb about quite nimbly on weeds using their long and flexible foot. The European fingernail clam (Sphaerium corneum), for example, climbs around on water weeds at the edges of lakes and ponds; this enables the clam to find the best position for filter feeding. The thick shell and rounded shape of bivalves make them awkward for potential predators to tackle. Nevertheless, a number of different creatures include them in their diet. Many species of demersal fish feed on them including the common carp (Cyprinus carpio), which is being used in the upper Mississippi River to try to control the invasive zebra mussel (Dreissena polymorpha). Birds such as the Eurasian oystercatcher (Haematopus ostralegus) have specially adapted beaks which can pry open their shells. The herring gull (Larus argentatus) sometimes drops heavy shells onto rocks in order to crack them open. Sea otters feed on a variety of bivalve species and have been observed to use stones balanced on their chests as anvils on which to crack open the shells. The Pacific walrus (Odobenus rosmarus divergens) is one of the main predators feeding on bivalves in Arctic waters. Shellfish have formed part of the human diet since prehistoric times, a fact evidenced by the remains of mollusc shells found in ancient middens. Examinations of these deposits in Peru has provided a means of dating long past El Niño events because of the disruption these caused to bivalve shell growth. Further changes in shell development due to environmental stress has also been suggested to cause increased mortality in oysters due to reduced shell strength. Invertebrate predators include crustaceans, starfish and octopuses. Crustaceans crack the shells with their pincers and starfish use their water vascular system to force the valves apart and then insert part of their stomach between the valves to digest the bivalve's body. It has been found experimentally that both crabs and starfish preferred molluscs that are attached by byssus threads to ones that are cemented to the substrate. This was probably because they could manipulate the shells and open them more easily when they could tackle them from different angles. Octopuses either pull bivalves apart by force, or they bore a hole into the shell and insert a digestive fluid before sucking out the liquified contents. Certain carnivorous gastropod snails such as whelks (Buccinidae) and murex snails (Muricidae) feed on bivalves by boring into their shells. A dog whelk (Nucella) drills a hole with its radula assisted by a shell-dissolving secretion. The dog whelk then inserts its extendible proboscis and sucks out the body contents of the victim, which is typically a blue mussel. Razor shells can dig themselves into the sand with great speed to escape predation. When a Pacific razor clam (Siliqua patula) is laid on the surface of the beach, it can bury itself completely in seven seconds and the Atlantic jackknife clam, Ensis directus, can do the same within fifteen seconds. Scallops and file clams can swim by opening and closing their valves rapidly; water is ejected on either side of the hinge area and they move with the flapping valves in front. Scallops have simple eyes around the margin of the mantle and can clap their valves shut to move sharply, hinge first, to escape from danger. Cockles can use their foot to move across the seabed or leap away from threats. The foot is first extended before being contracted suddenly when it acts like a spring, projecting the animal forwards. In many bivalves that have siphons, they can be retracted back into the safety of the shell. If the siphons inadvertently get attacked by a predator, in some cases, they snap off. The animal can regenerate them later, a process that starts when the cells close to the damaged site become activated and remodel the tissue back to its pre-existing form and size. In some other cases, it does not snap off. If the siphon is exposed, it is the key for a predatory fish to obtain the entire body. This tactic has been observed against bivalves with an infaunal lifestyle. File shells, such as Limaria fragilis, can produce a noxious secretion when stressed. It has numerous tentacles which fringe its mantle and protrude some distance from the shell when it is feeding. If attacked, it sheds tentacles in a process known as autotomy. The toxin released by this is distasteful and the detached tentacles continue to writhe which may also serve to distract potential predators. Mariculture Oysters, mussels, clams, scallops and other bivalve species are grown with food materials that occur naturally in their culture environment in the sea and lagoons. One-third of the world's farmed food fish harvested in 2010 was achieved without the use of feed, through the production of bivalves and filter-feeding carps. European flat oysters (Ostrea edulis) were first farmed by the Romans in shallow ponds and similar techniques are still in use. Seed oysters are either raised in a hatchery or harvested from the wild. Hatchery production provides some control of the broodstock but remains problematic because disease-resistant strains of this oyster have not yet been developed. Wild spats are harvested either by broadcasting empty mussel shells on the seabed or by the use of long, small-mesh nets filled with mussel shells supported on steel frames. The oyster larvae preferentially settle out on the mussel shells. Juvenile oysters are then grown on in nursery trays and are transferred to open waters when they reach 5 to 6 millimetres (0.20 to 0.24 in) in length. Many juveniles are further reared off the seabed in suspended rafts, on floating trays or cemented to ropes. Here they are largely free from bottom-dwelling predators such as starfish and crabs but more labour is required to tend them. They can be harvested by hand when they reach a suitable size. Other juveniles are laid directly on the seabed at the rate of 50 to 100 kilograms (110 to 220 lb) per hectare. They grow on for about two years before being harvested by dredging. Survival rates are low at about 5%. The Pacific oyster (Crassostrea gigas) is cultivated by similar methods but in larger volumes and in many more regions of the world. This oyster originated in Japan where it has been cultivated for many centuries. It is an estuarine species and prefers salinities of 20 to 25 parts per thousand. Breeding programmes have produced improved stock that is available from hatcheries. A single female oyster can produce 50–80 million eggs in a batch so the selection of broodstock is of great importance. The larvae are grown on in tanks of static or moving water. They are fed high quality microalgae and diatoms and grow fast. At metamorphosis the juveniles may be allowed to settle on PVC sheets or pipes, or crushed shell. In some cases, they continue their development in "upwelling culture" in large tanks of moving water rather than being allowed to settle on the bottom. They then may be transferred to transitional, nursery beds before being moved to their final rearing quarters. Culture there takes place on the bottom, in plastic trays, in mesh bags, on rafts or on long lines, either in shallow water or in the intertidal zone. The oysters are ready for harvesting in 18 to 30 months depending on the size required. Similar techniques are used in different parts of the world to cultivate other species including the Sydney rock oyster (Saccostrea commercialis), the northern quahog (Mercenaria mercenaria), the blue mussel (Mytilus edulis), the Mediterranean mussel (Mytilus galloprovincialis), the New Zealand green-lipped mussel (Perna canaliculus), the grooved carpet shell (Ruditapes decussatus), the Japanese carpet shell (Venerupis philippinarum), the pullet carpet shell (Venerupis pullastra) and the Yesso scallop (Patinopecten yessoensis). Production of bivalve molluscs by mariculture in 2010 was 12,913,199 tons, up from 8,320,724 tons in 2000. Culture of clams, cockles and ark shells more than doubled over this time period from 2,354,730 to 4,885,179 tons. Culture of mussels over the same period grew from 1,307,243 to 1,812,371 tons, of oysters from 3,610,867 to 4,488,544 tons and of scallops from 1,047,884 to 1,727,105 tons. Use as food Bivalves have been an important source of food for humans at least since Roman times and empty shells found in middens at archaeological sites are evidence of earlier consumption. Oysters, scallops, clams, ark clams, mussels and cockles are the most commonly consumed kinds of bivalve, and are eaten cooked or raw. In 1950, the year in which the Food and Agriculture Organization (FAO) started making such information available, world trade in bivalve molluscs was 1,007,419 tons. By 2010, world trade in bivalves had risen to 14,616,172 tons, up from 10,293,607 tons a decade earlier. The figures included 5,554,348 (3,152,826) tons of clams, cockles and ark shells, 1,901,314 (1,568,417) tons of mussels, 4,592,529 (3,858,911) tons of oysters and 2,567,981 (1,713,453) tons of scallops. China increased its consumption 400-fold during the period 1970 to 1997. It has been known for more than a century that consumption of raw or insufficiently cooked shellfish can be associated with infectious diseases. These are caused either by bacteria naturally present in the sea such as Vibrio spp. or by viruses and bacteria from sewage effluent that sometimes contaminates coastal waters. As filter feeders, bivalves pass large quantities of water through their gills, filtering out the organic particles, including the microbial pathogens. These are retained in the animals' tissues and become concentrated in their liver-like digestive glands. Another possible source of contamination occurs when bivalves contain marine biotoxins as a result of ingesting numerous dinoflagellates. These microalgae are not associated with sewage but occur unpredictably as algal blooms. Large areas of a sea or lake may change colour as a result of the proliferation of millions of single-cell algae, and this condition is known as a red tide. In 1816 in France, a physician, J. P. A. Pasquier, described an outbreak of typhoid linked to the consumption of raw oysters. The first report of this kind in the United States was in Connecticut in 1894. As sewage treatment programmes became more prevalent in the late 19th century, more outbreaks took place. This may have been because sewage was released through outlets into the sea providing more food for bivalves in estuaries and coastal habitats. A causal link between the bivalves and the illness was not easy to demonstrate because the illness might come on days or even weeks after the ingestion of the contaminated shellfish. One viral pathogen is the Norwalk virus. This is resistant to treatment with chlorine-containing chemicals and may be present in the marine environment even when coliform bacteria have been killed by the treatment of sewage. Since the 1970s, outbreaks of oyster-vectored diseases have occurs throughout the world. The mortality rate of one disease causing bacteria Vibrio vulnificus, was high at 50%. In 1978, an oyster-associated gastrointestinal infection affecting more than 2,000 people occurred in Australia. The causative agent was found to be the Norwalk virus and the epidemic caused major economic difficulties to the oyster farming industry in the country. In 1988, an outbreak of hepatitis A associated with the consumption of inadequately cooked clams (Anadara subcrenata) took place in the Shanghai area of China. An estimated 290,000 people were infected and there were 47 deaths. In the United States and the European Union, since the early 1990s regulations have been in place that are designed to prevent shellfish from contaminated waters entering restaurants. Paralytic shellfish poisoning (PSP) is primarily caused by the consumption of bivalves that have accumulated toxins by feeding on toxic dinoflagellates, single-celled protists found naturally in the sea and inland waters. Saxitoxin is the most virulent of these. In mild cases, PSP causes tingling, numbness, sickness and diarrhoea. In more severe cases, the muscles of the chest wall may be affected leading to paralysis and even death. In 1937, researchers in California established the connection between blooms of these phytoplankton and PSP. The biotoxin remains potent even when the shellfish are well-cooked. In the United States, there is a regulatory limit of 80 μg/g of saxitoxin equivalent in shellfish meat. Amnesic shellfish poisoning (ASP) was first reported in eastern Canada in 1987. It is caused by the substance domoic acid found in certain diatoms of the genus Pseudo-nitzschia. Bivalves can become toxic when they filter these microalgae out of the water. Domoic acid is a low-molecular weight amino acid that is able to destroy brain cells causing memory loss, gastroenteritis, long-term neurological problems or death. In an outbreak in the western United States in 1993, finfish were also implicated as vectors, and seabirds and mammals suffered neurological symptoms. In the United States and Canada, a regulatory limit of 20 μg/g of domoic acid in shellfish meat is set. Ecosystem services Ecosystem services provided by marine bivalves in relation to nutrient extraction from the coastal environment have gained increased attention to mitigate adverse effects of excess nutrient loading from human activities, such as agriculture and sewage discharge. These activities damage coastal ecosystems and require action from local, regional, and national environmental management. Marine bivalves filter particles like phytoplankton, thereby transforming particulate organic matter into bivalve tissue or larger faecal pellets that are transferred to the benthos. Nutrient extraction from the coastal environment takes place through two different pathways: (i) harvest/removal of the bivalves – thereby returning nutrients back to land; or (ii) through increased denitrification in proximity to dense bivalve aggregations, leading to loss of nitrogen to the atmosphere. Active use of marine bivalves for nutrient extraction may include a number of secondary effects on the ecosystem, such as filtration of particulate material. This leads to partial transformation of particulate-bound nutrients into dissolved nutrients via bivalve excretion or enhanced mineralization of faecal material. When they live in polluted waters, bivalve molluscs have a tendency to accumulate substances such as heavy metals and persistent organic pollutants in their tissues. This is because they ingest the chemicals as they feed but their enzyme systems are not capable of metabolising them and as a result, the levels build up. This may be a health hazard for the molluscs themselves, and is one for humans who eat them. It also has certain advantages in that bivalves can be used in monitoring the presence and quantity of pollutants in their environment. There are limitations to the use of bivalves as bioindicators. The level of pollutants found in the tissues varies with species, age, size, time of year and other factors. The quantities of pollutants in the water may vary and the molluscs may reflect past rather than present values. In a study near Vladivostok it was found that the level of pollutants in the bivalve tissues did not always reflect the high levels in the surrounding sediment in such places as harbours. The reason for this was thought to be that the bivalves in these locations did not need to filter so much water as elsewhere because of the water's high nutritional content. A study of nine different bivalves with widespread distributions in tropical marine waters concluded that the mussel, Trichomya hirsuta, most nearly reflected in its tissues the level of heavy metals (Pb, Cd, Cu, Zn, Co, Ni, and Ag) in its environment. In this species there was a linear relationship between the sedimentary levels and the tissue concentration of all the metals except zinc. In the Persian Gulf, the Atlantic pearl-oyster (Pinctada radiata) is considered to be a useful bioindicator of heavy metals. Crushed shells, available as a by-product of the seafood canning industry, can be used to remove pollutants from water. It has been found that, as long as the water is maintained at an alkaline pH, crushed shells will remove cadmium, lead and other heavy metals from contaminated waters by swapping the calcium in their constituent aragonite for the heavy metal, and retaining these pollutants in a solid form. The rock oyster (Saccostrea cucullata) has been shown to reduce the levels of copper and cadmium in contaminated waters in the Persian Gulf. The live animals acted as biofilters, selectively removing these metals, and the dead shells also had the ability to reduce their concentration. Other uses Conchology is the scientific study of mollusc shells, but the term conchologist is also sometimes used to describe a collector of shells. Many people pick up shells on the beach or purchase them and display them in their homes. There are many private and public collections of mollusc shells, but the largest one in the world is at the Smithsonian Institution, which houses in excess of 20 million specimens. Shells are used decoratively in many ways. They can be pressed into concrete or plaster to make decorative paths, steps or walls and can be used to embellish picture frames, mirrors or other craft items. They can be stacked up and glued together to make ornaments. They can be pierced and threaded onto necklaces or made into other forms of jewellery. Shells have had various uses in the past as body decorations, utensils, scrapers and cutting implements. Carefully cut and shaped shell tools dating back 32,000 years have been found in a cave in Indonesia. In this region, shell technology may have been developed in preference to the use of stone or bone implements, perhaps because of the scarcity of suitable rock materials. The indigenous peoples of the Americas living near the east coast used pieces of shell as wampum. The channeled whelk (Busycotypus canaliculatus) and the quahog (Mercenaria mercenaria) were used to make white and purple traditional patterns. The shells were cut, rolled, polished and drilled before being strung together and woven into belts. These were used for personal, social and ceremonial purposes and also, at a later date, for currency. The Ho-Chunk people from Wisconsin had numerous uses for freshwater mussels including using them as spoons, cups, ladles and utensils. They notched them to provide knives, graters and saws. They carved them into fish hooks and lures. They incorporated powdered shell into clay to temper their pottery vessels. They used them as scrapers for removing flesh from hides and for separating the scalps of their victims. They used shells as scoops for gouging out fired logs when building canoes and they drilled holes in them and fitted wooden handles for tilling the ground. Buttons have traditionally been made from a variety of freshwater and marine shells. At first they were used decoratively rather than as fasteners and the earliest known example dates back five thousand years and was found at Mohenjo-daro in the Indus Valley. Sea silk is a fine fabric woven from the byssus threads of bivalves, particularly the pen shell (Pinna nobilis). It used to be produced in the Mediterranean region where these shells are endemic. It was an expensive fabric and overfishing has much reduced populations of the pen shell. Crushed shells are added as a calcareous supplement to the diet of laying poultry. Oyster shell and cockle shell are often used for this purpose and are obtained as a by-product from other industries. Mother-of-pearl or nacre is the naturally occurring lustrous layer that lines some mollusc shells. It is used to make pearl buttons and in artisan craftwork to make organic jewellery. It has traditionally been inlaid into furniture and boxes, particularly in China. It has been used to decorate musical instruments, watches, pistols, fans and other products. The import and export of goods made with nacre are controlled in many countries under the International Convention of Trade in Endangered Species of Wild Fauna and Flora. A pearl is created in the mantle of a mollusc when an irritant particle is surrounded by layers of nacre. Although most bivalves can create pearls, oysters in the family Pteriidae and freshwater mussels in the families Unionidae and Margaritiferidae are the main source of commercially available pearls because the calcareous concretions produced by most other species have no lustre. Finding pearls inside oysters is a very chancy business as hundreds of shells may need to be pried open before a single pearl can be found. Most pearls are now obtained from cultured shells where an irritant substance has been purposefully introduced to induce the formation of a pearl. A "mabe" (irregular) pearl can be grown by the insertion of an implant, usually made of plastic, under a flap of the mantle and next to the mother-of-pearl interior of the shell. A more difficult procedure is the grafting of a piece of oyster mantle into the gonad of an adult specimen together with the insertion of a shell bead nucleus. This produces a superior, spherical pearl. The animal can be opened to extract the pearl after about two years and reseeded so that it produces another pearl. Pearl oyster farming and pearl culture is an important industry in Japan and many other countries bordering the Indian and Pacific Oceans. The scallop is the symbol of St James and is called Coquille Saint-Jacques in French. It is an emblem carried by pilgrims on their way to the shrine of Santiago de Compostela in Galicia. The shell became associated with the pilgrimage and came to be used as a symbol showing hostelries along the route and later as a sign of hospitality, food and lodging elsewhere. Roman myth has it that Venus, the goddess of love, was born in the sea and emerged accompanied by fish and dolphins, with Botticelli depicting her as arriving in a scallop shell. The Romans revered her and erected shrines in her honour in their gardens, praying to her to provide water and verdant growth. From this, the scallop and other bivalve shells came to be used as a symbol for fertility. Its depiction is used in architecture, furniture and fabric design and it is the logo of Royal Dutch Shell, the global oil and gas company. Bivalvian taxonomies For the past two centuries no consensus has existed on bivalve phylogeny from the many classifications developed. In earlier taxonomic systems, experts used a single characteristic feature for their classifications, choosing among shell morphology, hinge type or gill type. Conflicting naming schemes proliferated due to these taxonomies based on single organ systems. One of the most widely accepted systems was that put forward by Norman D. Newell in Part N of the Treatise on Invertebrate Paleontology, which employed a classification system based on general shell shape, microstructures and hinge configuration. Because features such as hinge morphology, dentition, mineralogy, shell morphology and shell composition change slowly over time, these characteristics can be used to define major taxonomic groups. Since the year 2000, taxonomic studies using cladistical analyses of multiple organ systems, shell morphology (including fossil species) and modern molecular phylogenetics have resulted in the drawing up of what experts believe is a more accurate phylogeny of the Bivalvia. Based upon these studies, a new proposed classification system for the Bivalvia was published in 2010 by Bieler, Carter & Coan. In 2012, this new system was adopted by the World Register of Marine Species (WoRMS) for the classification of the Bivalvia. Some experts still maintain that Anomalodesmacea should be considered a separate subclass, whereas the new system treats it as the order Anomalodesmata, within the subclass Heterodonta. Molecular phylogenetic work continues, further clarifying which Bivalvia are most closely related and thus refining the classification. R.C. Moore, in Moore, Lalicker, and Fischer, 1952, Invertebrate Fossils, gives a practical and useful classification of pelecypods (Bivalvia) even if somewhat antiquated, based on shell structure, gill type, and hinge teeth configuration. Subclasses and orders given are: Prionodesmacea have a prismatic and nacreous shell structure, separated mantle lobes, poorly developed siphons, and hinge teeth that are lacking or unspecialized. Gills range from protobranch to eulamellibranch. Teleodesmacea on the other hand have a porcelanous and partly nacreous shell structure; Mantle lobes that are generally connected, well developed siphons, and specialized hinge teeth. In most, gills are eulamellibranch. In his 1935 work Handbuch der systematischen Weichtierkunde (Handbook of Systematic Malacology), Johannes Thiele introduced a mollusc taxonomy based upon the 1909 work by Cossmann and Peyrot. Thiele's system divided the bivalves into three orders. Taxodonta consisted of forms that had taxodont dentition, with a series of small parallel teeth perpendicular to the hinge line. Anisomyaria consisted of forms that had either a single adductor muscle or one adductor muscle much smaller than the other. Eulamellibranchiata consisted of forms with ctenidial gills. The Eulamellibranchiata was further divided into four suborders: Schizodonta, Heterodonta, Adapedonta and Anomalodesmata. The systematic layout presented here follows Newell's 1965 classification based on hinge tooth morphology (all taxa marked † are extinct) : Solemyoida † Cyrtodontoida Limoida (file shells) Mytiloida (true mussels) Ostreoida (oysters, formerly included in Pterioida) † Praecardioida Pterioida (pearl oysters, pen shells) Unionoida (freshwater mussels) † Modiomorpha † Hippuritoida † Lyrodesmatidae Myoida (soft-shell clams, geoducks, shipworms) † Redoniidae Veneroida (hard-shell clams, cockles, razor shells) The monophyly of the subclass Anomalodesmata is disputed. The standard view now is that it resides within the subclass Heterodonta. An alternative systematic scheme exists using gill morphology. This distinguishes between Protobranchia, Filibranchia and Eulamellibranchia. The first corresponds to Newell's Palaeotaxodonta and Cryptodonta, the second to his Pteriomorphia, with the last corresponding to all other groups. In addition, Franc separated the Septibranchia from his eulamellibranchs because of the morphological differences between them. The septibranchs belong to the superfamily Poromyoidea and are carnivorous, having a muscular septum instead of filamentous gills. In May 2010, a new taxonomy of the Bivalvia was published in the journal Malacologia. In compiling this, the authors used a variety of phylogenetic information including molecular analysis, anatomical analysis, shell morphology and shell microstructure as well as bio-geographic, paleobiogeographic and stratigraphic information. In this classification 324 families are recognized as valid, 214 of which are known exclusively from fossils and 110 of which occur in the recent past, with or without a fossil record. This classification has since been adopted by WoRMS. Proposed classification of Class Bivalvia (under the redaction of Rüdiger Bieler, Joseph G. Carter and Eugene V. Coan) (all taxa marked † are extinct) : Grade Euprotobranchia Subclass Heterodonta Infraclass Archiheterodonta Infraclass Euheterodonta Subclass Palaeoheterodonta Subclass Protobranchia Subclass Pteriomorphia Infraclass Eupteriomorphia References Further reading |
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Contents Bill Gates William Henry Gates III (born October 28, 1955) is an American businessman and philanthropist. A pioneer of the microcomputer revolution of the 1970s and 1980s, he co-founded the software company Microsoft in 1975 with his childhood friend Paul Allen. Gates became the world's then-youngest billionaire in 1987, at age 31. This followed Microsoft's initial public offering in the previous year and subsequent stock increase. Forbes magazine ranked him as the world's wealthiest person for 18 out of 24 years between 1995 and 2017, including 13 years consecutively from 1995 to 2007. Gates became the first centibillionaire in 1999, when his net worth briefly surpassed US$100 billion. According to Forbes, as of May 2025, his net worth stood at US$115.1 billion, making him the thirteenth-richest individual in the world. Born and raised in Seattle, Washington, Gates was privately educated at Lakeside School, where he befriended Allen and developed his computing interests. In 1973, he enrolled at Harvard University, where he took classes including Math 55 and graduate- level computer science courses, but he dropped out in 1975 to co-found and lead Microsoft. He served as its CEO for the next 25 years and also became president and chairman of the board when the company was incorporated in 1981. Succeeded as CEO by Steve Ballmer in 2000, he transitioned to chief software architect, a position he held until 2008. He stepped down as chairman of the board in 2014 and became technology adviser to CEO Satya Nadella and other Microsoft leaders, a position he still holds. He resigned from the board in 2020. Over time, Gates reduced his role at Microsoft to focus on his philanthropic work with the Bill & Melinda Gates Foundation, the world's largest private charitable organization, which he and his then-wife, Melinda French Gates, co-chaired from 2000 until 2024. Focusing on areas including health, education, and poverty alleviation, Gates became known for his efforts to combat transmissible diseases such as tuberculosis, malaria, and polio. After French Gates resigned as co-chair following the couple's divorce, the foundation was renamed the Gates Foundation, with Gates as its sole chair. Gates is the founder and chairman of several other companies, including BEN, Cascade Investment, TerraPower, Gates Ventures, and Breakthrough Energy. In 2010, he and Warren Buffett founded the Giving Pledge, whereby they and other billionaires pledged to give at least half their wealth to philanthropy. Named as one of the 100 most influential people of the 20th century by Time magazine in 1999, he has received numerous other honors and accolades, including a Presidential Medal of Freedom, awarded jointly to him and French Gates in 2016 for their philanthropic work. The subject of several documentary films, he published the first of three planned memoirs, Source Code: My Beginnings, in 2025. Early life and education William Henry Gates III was born on October 28, 1955, in Seattle, Washington, as the only son of William H. Gates Sr.[a] (1925–2020) and his first wife, Mary Maxwell Gates (1929–1994). His ancestry includes English, German, and Irish/Scots-Irish. His father was a prominent lawyer, and his mother served on the board of directors of First Interstate BancSystem and United Way of America. Gates's maternal grandfather, J. W. Maxwell, was a national bank president. Gates also has an older sister, Kristi (Kristianne), and a younger sister, Libby. He is the fourth of his name in his family, but is known as William Gates III or "Trey" (i.e., three) because his father had the "II" suffix. The family lived in the Sand Point area of Seattle in a home that was damaged by a rare tornado when Gates was 7. When Gates was young, his parents wanted him to pursue a career in law. During his childhood, his family regularly attended a church of the Congregational Christian Churches, a Protestant Reformed denomination. Gates was small for his age and was bullied as a child. The family encouraged competition; one visitor reported that "it didn't matter whether it was hearts or pickleball or swimming to the dock; there was always a reward for winning, and there was always a penalty for losing". At age 13, Gates enrolled in the private Lakeside Prep School. When he was in the eighth grade, the Mothers' Club at the school used proceeds from Lakeside School's rummage sale to buy a Teletype Model 33 ASR terminal and a block of computer time on a General Electric (GE) computer for the students. Gates took an interest in programming the GE system in BASIC, and he was excused from math classes to pursue his interest. He wrote his first computer program on this machine, an implementation of tic-tac-toe that allowed users to play games against the computer. Gates was fascinated by the machine and how it would always execute software code perfectly. After the Mothers Club donation was exhausted, Gates and other students sought time on systems, including DEC PDP minicomputers. One of these systems was a PDP-10 belonging to Computer Center Corporation (CCC), which banned Gates, Paul Allen, Ric Weiland, and Gates's best friend and first business partner, Kent Evans, for the summer after it caught them exploiting bugs in the operating system to obtain free computer time. The four students formed the Lakeside Programmers Club to make money. At the end of the ban, they offered to find bugs in CCC's software in exchange for extra computer time. Rather than using the system remotely via Teletype, Gates went to CCC's offices and studied source code for various programs that ran on the system, including Fortran, Lisp, and machine language. The arrangement with CCC continued until 1970, when the company went out of business. In 1971, a Lakeside teacher enlisted Gates and Evans to automate the school's class-scheduling system, providing them computer time and royalties in return. The duo worked diligently in order to have the program ready for their senior year. Towards the end of their junior year, Evans was killed in a mountain climbing accident, which Gates described as one of the saddest days of his life. He then turned to Allen, who helped him finish the system for Lakeside. At age 17, Gates formed a venture with Allen called Traf-O-Data to make traffic counters based on the Intel 8008 processor. In 1972, he served as a congressional page in the House of Representatives. He was a national merit scholar when he graduated from Lakeside School in 1973. He scored 1590 out of 1600 on the Scholastic Aptitude Tests (SAT) and enrolled at Harvard University in the autumn of 1973. Gates did not stay at Harvard long enough to choose a concentration, but took mathematics (including Math 55) and graduate-level computer science courses. While at Harvard, he met fellow student and future Microsoft CEO Steve Ballmer. Gates left Harvard after two years while Ballmer stayed and graduated magna cum laude. Years later, Ballmer succeeded Gates as Microsoft's CEO and maintained that position from 2000 until his resignation in 2014. Gates devised an algorithm for pancake sorting as a solution to one of a series of unsolved problems presented in a combinatorics class by Professor Harry Lewis. His solution held the record as the fastest version for over 30 years, and its successor is faster by only 2%. His solution was formalized and published in collaboration with Harvard computer scientist Christos Papadimitriou. Gates remained in contact with Paul Allen and joined him at Honeywell during the summer of 1974. In 1975, the MITS Altair 8800 was released based on the Intel 8080 CPU, and Gates and Allen saw the opportunity to start their own computer software company. Gates dropped out of Harvard that same year. His parents were supportive of him after seeing how much he wanted to start his own company. He explained his decision to leave Harvard: "If things hadn't worked out, I could always go back to school. I was officially on leave." Microsoft Gates read the January 1975 issue of Popular Electronics, which demonstrated the Altair 8800, and contacted Micro Instrumentation and Telemetry Systems (MITS) to inform them that he and others were working on a BASIC interpreter for the platform. In reality, Gates and Allen did not have an Altair and had not written code for it; they merely wanted to gauge MITS's interest. MITS president Ed Roberts agreed to meet them for a demonstration, and over the course of a few weeks, they developed an Altair emulator that ran on a minicomputer and then the BASIC interpreter. The demonstration was held at MITS's offices in Albuquerque, New Mexico. It was a success and resulted in a deal with MITS to distribute the interpreter as Altair BASIC. MITS hired Allen, and Gates took a leave of absence from Harvard to work with him at MITS in November 1975. Allen named their partnership "Micro-Soft", a combination of "microcomputer" and "software". Their first office was in Albuquerque. The first employee Gates and Allen hired was their high school collaborator Ric Weiland. They dropped the hyphen within a year and officially registered the trade name "Microsoft" with the Secretary of the State of New Mexico on November 26, 1976. Gates never returned to Harvard to complete his studies. Microsoft's Altair BASIC was popular with computer hobbyists, but Gates discovered that a pre-market copy had leaked out and was being widely copied and distributed. In February 1976, he wrote An Open Letter to Hobbyists in the MITS newsletter in which he asserted that more than 90% of the users of Microsoft Altair BASIC had not paid Microsoft for it, and the Altair "hobby market" was in danger of eliminating the incentive for any professional developers to produce, distribute, and maintain high-quality software. This letter was unpopular with many computer hobbyists, but Gates persisted in his belief that software developers should be able to demand payment. Microsoft became independent of MITS in late 1976, and it continued to develop programming language software for various systems. The company moved from Albuquerque to Bellevue, Washington, on January 1, 1979. Gates said he personally reviewed and often rewrote every line of code that the company produced in its first five years. As the company grew, he transitioned into a manager role, then an executive. IBM, the leading supplier of computer equipment to commercial enterprises at the time, approached Microsoft in July 1980 concerning software for its upcoming personal computer, the IBM PC, after Gates's mother mentioned Microsoft to John Opel, IBM's then CEO. IBM first proposed that Microsoft write the BASIC interpreter. IBM's representatives also mentioned that they needed an operating system, and Gates referred them to Digital Research (DRI), makers of the widely used CP/M operating system. IBM's discussions with Digital Research went poorly, and they did not reach a licensing agreement. IBM representative Jack Sams mentioned the licensing difficulties during a subsequent meeting with Gates and asked if Microsoft could provide an operating system. A few weeks later, Gates and Allen proposed using 86-DOS, an operating system similar to CP/M, that Tim Paterson of Seattle Computer Products (SCP) had made for hardware similar to the PC. Microsoft made a deal with SCP to be the exclusive licensing agent of 86-DOS, and later the full owner. Microsoft employed Paterson to adapt the operating system for the PC and delivered it to IBM as PC DOS for a one-time fee of $50,000. The contract itself only earned Microsoft a relatively small fee. It was the prestige brought to Microsoft by IBM's adoption of its operating system that would be the origin of Microsoft's transformation from a small business to the leading software company in the world. Gates had not offered to transfer the copyright on the operating system to IBM because he believed that other personal computer makers would clone IBM's PC hardware. They did, making the IBM-compatible PC, running DOS, a de facto standard. The sales of MS-DOS (the version of DOS sold to customers other than IBM) made Microsoft a major player in the industry. The press quickly identified Microsoft as being very influential on the IBM PC. PC Magazine asked if Gates was "the man behind the machine?". Gates oversaw Microsoft's company restructuring on June 25, 1981, which re-incorporated the company in Washington state and made Gates the president and chairman of the board, with Paul Allen as vice president and vice chairman. In early 1983, Allen left the company after receiving a Hodgkin lymphoma diagnosis, effectively ending the formal business partnership between Gates and Allen, which had been strained months prior due to a contentious dispute over Microsoft equity. Later in the decade, Gates repaired his relationship with Allen, and together the two donated millions to their childhood school, Lakeside. They remained friends until Allen's death in October 2018. Microsoft and Gates launched their first retail version of Microsoft Windows on November 20, 1985, in an attempt to fend off competition from Apple's Macintosh GUI, which had captivated consumers with its simplicity and ease of use. In August 1986, the company struck a deal with IBM to develop a separate operating system called OS/2. Although the two companies successfully developed the first version of the new system, the partnership deteriorated due to mounting creative differences. The operating system grew out of DOS in an organic fashion over a decade until Windows 95, which hid the DOS prompt by default. Windows XP was released one year after Gates stepped down as Microsoft CEO. Windows 8.1 was the last version of the OS released before Gates left the chair of the firm to John W. Thompson on February 5, 2014. During Microsoft's early years, Gates was an active software developer, particularly in the company's programming language products, but his primary role in most of the company's history was as a manager and executive. He has not officially been on a development team since working on the TRS-80 Model 100, but he wrote code that shipped with the company's products as late as 1989. Jerry Pournelle wrote in 1985 when Gates announced Microsoft Excel: "Bill Gates likes the program, not because it's going to make him a lot of money (although I'm sure it will do that), but because it's a neat hack." During the late 1990s, he was criticized for his business tactics, which were considered anti-competitive. This opinion has been upheld by numerous court rulings. In June 2006, Gates announced that he would transition out of his role at Microsoft to dedicate more time to philanthropy. He gradually divided his responsibilities between two successors when he placed Ray Ozzie in charge of management and Craig Mundie in charge of long-term product strategy. The process took two years to fully transfer his duties to Ozzie and Mundie, and was completed on June 27, 2008. Post-Microsoft Since leaving day-to-day operations at Microsoft, Gates has continued his philanthropy and works on other projects. He stepped down as chairman of Microsoft in February 2014 to become a technology advisor at the firm to support newly appointed CEO Satya Nadella. Gates provided his perspective on a range of issues in an interview that was published in the March 2014 issue of Rolling Stone magazine. In the interview, he provided his perspective on climate change, his charitable activities, various tech companies and people involved in them, and the state of America. In response to a question about his greatest fear when he looks 50 years into the future, Gates stated: "there'll be some really bad things that'll happen in the next 50 or 100 years, but hopefully none of them on the scale of, say, a million people that you didn't expect to die from a pandemic, or nuclear or bioterrorism." Gates also identified innovation as the "real driver of progress" and pronounced that "America's way better today than it's ever been." Gates has often expressed concern about the potential harms of superintelligence; in a Reddit "ask me anything", he stated that: First the machines will do a lot of jobs for us and not be super intelligent. That should be positive if we manage it well. A few decades after that though the intelligence is strong enough to be a concern. I agree with Elon Musk and some others on this and don't understand why some people are not concerned. In an interview that was held at the TED conference in March 2015, with Baidu co-founder and CEO, Robin Li, Gates said he would "highly recommend" Nick Bostrom's recent work, Superintelligence: Paths, Dangers, Strategies. During the conference, Gates warned that the world was not prepared for the next pandemic, a situation that would come to pass in late 2019 when the COVID-19 pandemic began. In March 2018, Gates met at his home in Seattle with Mohammed bin Salman, the crown prince and de facto ruler of Saudi Arabia, to discuss investment opportunities for Saudi Vision 2030. In June 2019, Gates admitted that losing the mobile operating system race to Android was his biggest mistake. He stated that it was within their skill set of be the dominant player, but partially blames the antitrust litigation during that time. That same year, Gates became an advisory board member of the Bloomberg New Economy Forum. In March 2020, Microsoft announced Gates would be leaving his board positions at Berkshire Hathaway and Microsoft to dedicate himself to philanthropic endeavors such as climate change, global health and development, and education. The Wall Street Journal reported in May 2021 that Gates stepped down before Microsoft's board finished its investigation into Gates's alleged inappropriate sexual relationship with a Microsoft employee, which an external law firm had begun probing in late 2019. During the COVID-19 pandemic, Gates has been looked at by media outlets as an expert on the issue, despite not being a public official or having any prior medical training. His foundation did, however, establish the COVID-19 Therapeutics Accelerator in 2020 to hasten the development and evaluation of new and repurposed drugs and biologics to treat patients for COVID-19 and, as of February 2021, Gates expressed that he and Anthony Fauci frequently talk and collaborate on matters including vaccines and other medical innovations to fight the pandemic. Gates has a multi-billion dollar investment portfolio with stakes in companies in multiple sectors and has participated in several entrepreneurial ventures beyond Microsoft, including: Climate change and energy Gates considers climate change and global access to energy to be critical, interrelated issues. He has urged governments and the private sector to invest in research and development to make clean, reliable energy cheaper. Gates envisions that a breakthrough innovation in sustainable energy technology could drive down both greenhouse gas emissions and poverty, and bring economic benefits by stabilizing energy prices. In 2011, he said, "If you gave me the choice between picking the next 10 presidents or ensuring that energy is environmentally friendly and a quarter as costly, I'd pick the energy thing." In 2015, he wrote about the challenge of transitioning the world's energy system from one based primarily on fossil fuels to one based on sustainable energy sources. Global energy transitions have historically taken decades. He wrote, "I believe we can make this transition faster, both because the pace of innovation is accelerating, and because we have never had such an urgent reason to move from one source of energy to another." This rapid transition, according to Gates, would depend on increased government funding for basic research and financially risky private-sector investment, to enable innovation in diverse areas such as nuclear energy, grid energy storage to facilitate greater use of solar and wind energy, and solar fuels. Gates spearheaded two initiatives that he announced at the 2015 United Nations Climate Change Conference in Paris. One was Mission Innovation, in which 20 national governments pledged to double their spending on research and development for carbon-free energy in over five years' time. Another initiative was Breakthrough Energy, a group of investors who agreed to fund high-risk startups in clean energy technologies. Gates, who had already invested $1 billion of his own money in innovative energy startups, committed a further $1 billion to Breakthrough Energy. In December 2020, he called for the U.S. federal government to create institutes for clean energy research, analogous to the National Institutes of Health. Gates has also urged rich nations to shift to 100% synthetic beef industries to reduce greenhouse gas emissions from food production. Gates has been criticized for holding a large stake in Signature Aviation, a company that services emissions-intensive private jets. In 2019, he began to divest from fossil fuels. He does not expect divestment itself to have much practical impact, but says that if his efforts to provide alternatives were to fail, he would not want to personally benefit from an increase in fossil fuel stock prices. After he published his book How to Avoid a Climate Disaster, parts of the climate activist community criticized Gates's approach as technological solutionism. In 2022, educational streamer Wondrium produced the series "Solving for Zero: The Search for Climate Innovation", inspired by the book. In June 2021, Gates's company TerraPower and Warren Buffett's PacifiCorp announced the first sodium nuclear reactor in Wyoming. Wyoming Governor Mike Gordon hailed the project as a step toward carbon-negative nuclear power. Wyoming Senator John Barrasso also said that it could boost the state's once-active uranium mining industry. Gates supported the passage of the Inflation Reduction Act of 2022. He tried to convince Joe Manchin to support a climate bill starting in 2019, and especially in the months leading up to the adoption of the bill. The bill aimed to cut the global greenhouse gas emissions to a level similar to "eliminating the annual planet-warming pollution of France and Germany combined" and may help to limit the warming of the planet to 1.5 degrees – the target of the Paris Agreement. He thanked both Joe Manchin and Chuck Schumer for their efforts in a guest essay in The New York Times, where he said, "The Inflation Reduction Act of 2022 may be the single most important piece of climate legislation in American history", given its potential to spur development of new technologies. Gates gave further insights on climate change in his commencement address at Northern Arizona University on May 6, 2023, where he was bestowed an honorary doctorate. Political positions In October 2024, The New York Times reported Gates had recently donated $50 million to Future Forward USA Action, a 501(c)(4) organization supporting Kamala Harris's 2024 presidential campaign. In response to the report, he did not explicitly address the donation or endorse Harris, but said "this election is different". In 1998, Gates rejected the need for regulation of the software industry in testimony before the United States Senate. During the Federal Trade Commission's (FTC) investigation of Microsoft in the 1990s, Gates was reportedly upset at then Commissioner Dennis Yao for "float[ing] a line of hypothetical questions suggesting possible curbs on Microsoft's growing monopoly power". After Facebook and Twitter had banned Donald Trump from their platforms on January 7, 2021, as a result of the 2020 United States presidential election which led to the January 6 United States Capitol attack, Gates said in February that a permanent ban of Trump "would be a shame" and would be an "extreme measure". He warned that it would cause "polarization" if users with different political views divide up among various social networks, and said: "I don't think banning somebody who actually did get a fair number of votes (in the presidential election) – well less than a majority – but I don't think having him off forever would be that good." In April 2021, during the COVID-19 pandemic, Gates was criticized for suggesting that pharmaceutical companies should hold onto patents and intellectual property for COVID-19 vaccines. He opposed the TRIPS waiver. The Gates Foundation encouraged Oxford University to partner with a big company rather than give away the rights to its COVID-19 vaccine, as the university had initially announced. Oxford University eventually partnered with AstraZeneca. The criticism came due to the possibility of this preventing poorer nations from obtaining adequate vaccines. Gates argued that what limited widespread access was not intellectual property, but rather the time needed for safety protocols, and the difficulty of safely transferring vaccine production to new facilities. His views on the topic have been linked to his views on legal monopolies in software. Gates has been critical of cryptocurrencies like Bitcoin. According to him, cryptocurrencies provide no "valuable output", contribute nothing to society, and pose a danger especially for smaller investors who could not survive the potentially high losses. Gates also does not own any cryptocurrencies himself. Philanthropy In an interview with the BBC in 2025, Gates stated that his charitable donations have totalled $100 billion, of which $60 billion have gone to the Bill & Melinda Gates Foundation. Gates studied the work of Andrew Carnegie and John D. Rockefeller, and donated some of his Microsoft stock in 1994 to create the "William H. Gates Foundation". In 2000, Gates and his wife combined three family foundations and donated stock valued at $5 billion to create the Bill & Melinda Gates Foundation, which was identified by the Funds for NGOs company in 2013, as the world's largest charitable foundation, with assets reportedly valued at more than $34.6 billion. The foundation allows benefactors to access information that shows how its money is being spent, unlike other major charitable organizations such as the Wellcome Trust. Gates, through his foundation, also donated $20 million to the Carnegie Mellon University for a new building to be named Gates Center for Computer Science which opened in 2009. Gates has credited the generosity and extensive philanthropy of David Rockefeller as a major influence. He and his father met with Rockefeller several times, and their charity work is partly modeled on the Rockefeller family's philanthropic focus, whereby they are interested in tackling the global problems that are ignored by governments and other organizations. The foundation is organized into five program areas: Global Development Division, Global Health Division, United States Division, and Global Policy & Advocacy Division. Among others, it supports a wide range of public health projects, granting aid to fight transmissible diseases such AIDS, tuberculosis and malaria, as well as widespread vaccine programs to eradicate polio. It grants funds to learning institutes and libraries and supports scholarships at universities. The foundation established a water, sanitation and hygiene program to provide sustainable sanitation services in poor countries. Its agriculture division supports the International Rice Research Institute in developing Golden Rice, a genetically modified rice variant used to combat vitamin A deficiency. The foundation aims to provide women and girls in the developing world with information and support regarding contraception and, ultimately, universal access to consensual family planning. In 2007, the Los Angeles Times criticized the foundation for investing its assets in companies that have been accused of worsening poverty, pollution and pharmaceutical firms that do not sell to developing countries. Although the foundation announced a review of its investments to assess social responsibility, it was subsequently canceled and upheld its policy of investing for maximum return, while using voting rights to influence company practices. Gates delivered his thoughts in a fireside chat moderated by journalist and news anchor Shereen Bhan virtually at the Singapore FinTech Festival on December 8, 2020, on the topic, "Building Infrastructure for Resilience: What the COVID-19 Response Can Teach Us About How to Scale Financial Inclusion". Governments are there to think ahead to bad things that might happen. In the case of (the COVID-19) pandemic, not enough was done. We can't forget that another pandemic will come and we'll need to invest in being ready in that, ... while not forgetting that we were not prepared and we're going to have to invest – just like having a fire department – some money in an intelligent way and actually simulate what might happen and make sure that we're ready for it. In a November 2020 interview with actress Rashida Jones, Gates endorsed the wearing of face masks as a means to public reopening, derisively comparing anti-mask activism to "nudists" who oppose wearing pants. Melinda Gates suggested that people should emulate the philanthropic efforts of the Salwen family, who sold their home and gave away half of its value, as detailed in their book, The Power of Half. Gates and his wife invited Joan Salwen to Seattle to speak about what the family had done, and on December 9, 2010, Bill and Melinda Gates and investor Warren Buffett each signed a commitment they called the "Giving Pledge", which is a commitment by all three to donate at least half of their wealth, over the course of time, to charity. The Foundation has received criticism, particularly over its role in Common Core, with critics stating the support is "cronyist" in that it profits from the "federal, state, and local contracts". Gates has also provided personal donations to educational institutions. In 1999, Gates donated $20 million to the Massachusetts Institute of Technology for the construction of a computer laboratory named the "William H. Gates Building" that was designed by architect Frank Gehry. While Microsoft had previously given financial support to the institution, this was the first personal donation received from Gates. The Maxwell Dworkin Laboratory of the Harvard John A. Paulson School of Engineering and Applied Sciences is named after the mothers of both Gates and Microsoft President Steven A. Ballmer, both of whom were students (Ballmer was a member of the school's graduating class of 1977, while Gates left his studies for Microsoft), and donated funds for the laboratory's construction. Gates also donated $6 million to the construction of the Gates Computer Science Building, completed in January 1996, on the campus of Stanford University. The building contains the Computer Science Department and the Computer Systems Laboratory (CSL) of Stanford's Engineering department. Since 2005, Gates and his foundation have taken an interest in solving global sanitation problems. For example, they announced the "Reinvent the Toilet Challenge", which has received considerable media interest. To raise awareness for the topic of sanitation and possible solutions, Gates drank water that was "produced from human feces" in 2014 – it was produced from a sewage sludge treatment process called the Omni Processor. In early 2015, he also appeared with Jimmy Fallon on The Tonight Show and challenged him to see if he could taste the difference between this reclaimed water or bottled water. In November 2017, Gates said he would give $50 million to the Dementia Discovery Fund, a venture capital fund that seeks treatment for Alzheimer's disease. He also pledged an additional $50 million to start-up ventures working in Alzheimer's research. Bill and Melinda Gates have said that they intend to leave their three children $10 million each as their inheritance. With only $30 million kept in the family, they are expected to give away about 99.96% of their wealth. In 2025 Bill Gates said in an interview with Raj Shammi that his children will inherit less than 1% of his wealth. On August 25, 2018, Gates distributed $600,000 through his foundation via UNICEF which is helping flood affected victims in Kerala, India. In June 2018, Gates offered free ebooks, to all new graduates of U.S. colleges and universities, and in 2021, offered free ebooks, to all college and university students around the world. The Bill & Melinda Gates Foundation partially funds OpenStax, which creates and provides free digital textbooks. In July 2022 he reiterated the commitment he had made by starting the Giving Pledge campaign by announcing on his Twitter channel he planned to give 'virtually all' his wealth to charity and eventually 'move off of the list of the world's richest people'. In April 2017, Gates partnered with Swiss tennis player Roger Federer in playing in the Match for Africa 4, a noncompetitive tennis match at a sold-out Key Arena in Seattle. The event was in support of the Roger Federer Foundation's charity efforts in Africa. Federer and Gates played against John Isner, the top-ranked American player for much of this decade, and Mike McCready, the lead guitarist for Pearl Jam. The pair won the match 6 games to 4. Overall, they raised $2 million for children in Africa. The following year, Gates and Federer returned to play in the Match for Africa 5 on March 5, 2018, at San Jose's SAP Center. Their opponents were Jack Sock, one of the top American players and a grand slam winner in doubles, and Savannah Guthrie, a co-anchor for NBC's Today show. Gates and Federer recorded their second match victory together by a score of 6–3 and the event raised over $2.5 million. Books In 1989, Gates wrote the foreword to the Microsoft Press book Learn BASIC Now, by Michael Halvorson and David Rygmyr, reflecting on the growth of the BASIC language and its use in most of the era's personal computers. He also sketched out plans for BASIC's use as a universal language to embellish or alter the performance of a range of software applications. Gates has authored several books. The Road Ahead, co-authored with Microsoft executive Nathan Myhrvold and journalist Peter Rinearson, was published in November 1995. It summarized the implications of the personal computing revolution and described a future profoundly changed by the arrival of a global information superhighway. His second book, Business @ the Speed of Thought, co-authored with Collins Hemingway, was published in 1999, and discusses how business and technology are integrated, and shows how digital infrastructures and information networks can help to get an edge on the competition. In 2021 he published How to Avoid a Climate Disaster, which presents what Gates learned in over a decade of studying climate change and investing in innovations to address climate problems. Following the COVID-19 pandemic Gates published How to Prevent the Next Pandemic in 2022 which proposes a "Global Epidemic Response and Mobilization" (GERM) team with annual funding of $1 billion, under the auspices of the WHO. The first of Gates's planned three memoirs, Source Code was published in February 2025. Personal life Gates is an avid reader, and the ceiling of his large home library is engraved with a quotation from The Great Gatsby. He also enjoys bridge, golf, and tennis. His days are planned for him on a minute-by-minute basis, similarly to the U.S. president's schedule. Despite his wealth and extensive business travel, Gates flew coach (economy class) in commercial aircraft until 1997, when he bought a private jet. In the 1990s, Gates built an earth-sheltered mansion, designed by James Cutler and Peter Bohlin, in the side of a hill overlooking Lake Washington in Medina, Washington. The estate has been nicknamed "Xanadu 2.0" by Gates's biographers. In 2009, property taxes on the mansion were reported to be US$1.063 million, on a total assessed value of US$147.5 million. The 66,000-square-foot (6,100 m2) estate has a 60-foot (18 m) swimming pool with an underwater music system, as well as a 2,500-square-foot (230 m2) gym and a 1,000-square-foot (93 m2) dining room. Gates purchased the Codex Leicester, a collection of scientific writings by Leonardo da Vinci, for US$30.8 million at an auction in 1994. In 1998, he reportedly paid $30 million for the original 1885 maritime painting Lost on the Grand Banks, at the time a record price for an American painting. In 2016, he revealed that he was color-blind. In 2025, in Source Code, Gates wrote that he believed he was autistic. In 1987, at a trade fair in New York, Gates met Melinda French, then a recent graduate of Duke University who had begun working at Microsoft around four months earlier. Gates and French became engaged in 1993 after dating for six years. They married on January 1, 1994, at the 12th hole of the Jack Nicklaus–designed Manele Golf Course on the Hawaiian Island of Lānaʻi. They have three children, two daughters and a son. On May 3, 2021, Bill and Melinda Gates announced their decision to divorce after more than 27 years of marriage. The Wall Street Journal reported that Melinda had begun meeting with divorce attorneys in 2019, citing interviews that suggested Gates's ties with Jeffrey Epstein were among her concerns. However, the couple delayed their divorce until their youngest child Phoebe Gates graduated from high school. The divorce was finalized on August 2, 2021, and the financial details have remained confidential. In October 2021, Gates's eldest daughter Jennifer, a pediatrician and professional show-jumper, married Olympic equestrian Nayel Nassar, with whom she has two daughters, born in March 2023 and October 2024. His son Rory is pursuing a PhD at the Institute of World Politics. His youngest daughter Phoebe co-founded the digital fashion platform Phia and is an advocate for women's health and reproductive rights. In February 2023, Gates confirmed that he was dating Paula Hurd (née Kalupa), widow of former Oracle Corporation and Hewlett-Packard chief executive Mark Hurd. Appearing on the Today show in February 2025, he described Hurd as a "serious girlfriend", stating he had "moved past the divorce". Gates's public image has changed over the years. At first he was perceived as a brilliant but ruthless "robber baron", a "nerd-turned-tycoon". Starting in 2000 with the foundation of the Bill & Melinda Gates Foundation, and particularly after he stepped down as head of Microsoft, he turned his attention to philanthropy, spending more than $50 billion on causes like health, poverty, and education. His image morphed from "tyrannical technocrat to saintly savior" to a "huggable billionaire techno-philanthropist", celebrated on magazine covers and sought after for his opinions on major issues like global health and climate change. Still another shift in public opinion came in 2021 with the announcement that he and Melinda were divorcing. Coverage of that proceeding brought out information about romantic pursuits of women who worked for him, a long-term extra-marital affair, and a friendship with convicted sex offender Jeffrey Epstein. This information and his response to the COVID-19 pandemic resulted in some deterioration of his public image, going from "a lovable nerd who was out to save the world" to "a tech supervillain who wants to protect profits over public health". Investigative journalist Tim Schwab has accused Gates of using his contributions to the media to shape their coverage of him in order to protect his public image. In September 2022, Politico published an exposé critical of NGO leadership at the helm of the worldwide COVID-19 pandemic response, written in cooperation with the German newspaper Die Welt. Criticisms included the interconnectivity of the non-profits with Gates, as well as his personal lack of formal credentials in medicine. Gates and the projects of his foundation have been the subject of many conspiracy theories that proliferate on Facebook and elsewhere. He has been implausibly accused of attempting to depopulate the world, distributing harmful or unethical vaccines, and implanting people with privacy-violating microchips. These unfounded theories reached a new level of influence during the COVID-19 pandemic when, according to New York Times journalist Rory Smith, the uncertainties of pandemic life drove people to seek explanations from the Internet. When asked about the theories, Gates has remarked that some people are tempted by the "simple explanation" that an evil person rather than biological factors are to blame, and that he does not know for what purpose anyone believes he would want to track them with microchips. In an interview with Rolling Stone, Gates said in regard to his faith: "The moral systems of religion, I think, are super important. We've raised our kids in a religious way; they've gone to the Catholic church that Melinda goes to and I participate in. I've been very lucky, and therefore I owe it to try and reduce the inequity in the world. And that's kind of a religious belief. I mean, it's at least a moral belief." In the same 2014 interview he also said: "I agree with people like Richard Dawkins that mankind felt the need for creation myths. Before we really began to understand disease and the weather and things like that, we sought false explanations for them. Now science has filled in some of the realm – not all – that religion used to fill. But the mystery and the beauty of the world is overwhelmingly amazing, and there's no scientific explanation of how it came about. To say that it was generated by random numbers, that does seem, you know, sort of an uncharitable view [laughs]. I think it makes sense to believe in God, but exactly what decision in your life you make differently because of it, I don't know." When Microsoft went public in 1986, Gates retained 44.9% ownership of the company. In 1987, he was listed as a billionaire in Forbes magazine's first America's richest issue; Gates was the world's youngest-ever self-made billionaire, with a net worth of $1.25 billion. Since then, he has been featured on The World's Billionaires list and was ranked as the richest person in 1995, 1996, 1998–2007, and 2009, maintaining the position until 2018, when Jeff Bezos surpassed his wealth. Gates was ranked first on the Forbes 400 list of wealthiest Americans from 1993 to 2007, in 2009, and from 2014 to 2017. According to Forbes, as of February 17, 2025, Gates' estimated net worth stood at US$108.8 billion, making him the 16th richest individual in the world. Gates's wealth briefly surpassed US$100 billion in 1999, making him the first person to reach this net worth. After 2000, the nominal value of his Microsoft holdings declined, partly because of the decline in Microsoft's stock price after the dot-com bubble burst, and partly because of the multi-billion dollar donations he had made to his charitable foundations. In May 2006, Gates remarked that he wished that he was not the richest man in the world, because he disliked the attention that it brought. In March 2010, Gates was the second wealthiest person after Carlos Slim, but regained the top position in 2013, according to the Bloomberg Billionaires Index. Slim regained the position again in June 2014 (but then lost the top position back to Gates). Between 2009 and 2014, his wealth doubled from US$40 billion to US$82 billion. In October 2017, Gates was surpassed by Amazon founder Jeff Bezos as the richest person in the world. In the Forbes 400 list of wealthiest Americans in 2023, he was ranked sixth with a wealth of $115.0 billion. He once again became the richest person in the world in November 2019 after a 48% increase in Microsoft shares, surpassing Bezos. Gates told the BBC, "I've paid more tax than any individual ever, and gladly so ... I've paid over $6 billion in taxes." He is a proponent of higher taxes, particularly for the rich. Gates has several investments outside Microsoft, which in 2006 paid him a salary of US$616,667 and a bonus of US$350,000, for a total of US$966,667. In 1989, he founded Corbis, a digital imaging company. In 2004, he became a board member of Berkshire Hathaway, the investment company headed by long-time friend Warren Buffett. Controversies During his tenure as CEO of Microsoft, Gates approved of many decisions that led to antitrust litigation over Microsoft's business practices. In 1998's United States v. Microsoft Corp., Gates gave deposition testimony that several journalists characterized as evasive. He argued with examiner David Boies over the contextual meaning of words such as "compete", "concerned", and "we". Later in the year, when portions of the videotaped deposition were played back in court, the judge was seen laughing and shaking his head. BusinessWeek reported: Early rounds of his deposition show him offering obfuscatory answers and saying "I don't recall" so many times that even the presiding judge had to chuckle. Worse, many of the technology chief's denials and pleas of ignorance were directly refuted by prosecutors with snippets of e-mail that Gates both sent and received. Gates later said that he had simply resisted attempts by Boies to mischaracterize his words and actions. "Did I fence with Boies? ... I plead guilty ... rudeness to Boies in the first degree." Despite Gates's denials, the judge ruled that Microsoft had committed monopolization, tying and blocking competition, each in violation of the Sherman Antitrust Act. Some Microsoft employees, including key executives, have begun to act, speak, and sometimes look a bit like Gates. They may rock in their chairs, as if they were ready to go somewhere, or end each sentence by elongating the last word. — Computerworld, 1987 In my [early 1990s] BillG review meeting, the whole reporting hierarchy was there, along with their cousins, sisters, and aunts, and a person who came along from my team whose whole job during the meeting was to keep an accurate count of how many times Bill said the F word. The lower the f***-count, the better ... [After the meeting] "Four," announced the f*** counter, and everyone said, "wow, that’s the lowest I can remember. Bill is getting mellow in his old age." He was, you know, 36. — Joel Spolsky, 2006, Gates gained a reputation for being distant from others; an industry executive complained in 1981 that "Gates is notorious for not being reachable by phone and for not returning phone calls". He saw competition in personal terms; when Borland's Turbo Pascal performed better than Microsoft's own tools, he yelled at programming director Greg Whitten "for half an hour" because, Gates believed, Borland's Philippe Kahn had surpassed Gates. An Atari executive recalled that he showed Gates a game and defeated him 35 of 37 times. When they met again a month later, Gates "won or tied every game. He had studied the game until he solved it. That is a competitor". In the early 1980s, while business partner Paul Allen was undergoing treatments for cancer, Gates—according to Allen—conspired to reduce Allen's share in Microsoft by issuing himself stock options. In his autobiography, Allen would later recall that Gates was "scheming to rip me off. It was mercenary opportunism plain and simple". Gates says he remembers the episode differently. Allen would also recall that Gates was prone to shouting episodes. By 1987 Computerworld quoted an industry observer who said "Bill personifies Microsoft, and hotshots want to work for him". Joel Spolsky recalled how, when presenting Visual Basic for Applications for approval in the early 1990s, Gates had in one night read the technical specification of 500 pages and written notes on every page: "You couldn’t bullshit him for a minute because he was a programmer. A real, actual, programmer". Gates has often been accused of bullying Microsoft employees. He met regularly with Microsoft's senior managers and program managers, and the managers described him as being verbally combative, berating them for perceived holes in their business strategies or proposals that placed the company's long-term interests at risk. Gates interrupted presentations with such comments as "that's the stupidest thing I've ever heard" and "why don't you just give up your options and join the Peace Corps?" The target of his outburst would then have to defend the proposal in detail until Gates was fully convinced. Spolsky recalled being told after his presentation to Gates: Bill doesn’t really want to review your spec, he just wants to make sure you've got it under control. His standard M.O. is to ask harder and harder questions until you admit that you don’t know, and then he can yell at you for being unprepared. Not all harsh language was criticism; a manager recalled that "You're full of shit. That's the stupidest fucking thing I've ever heard" meant that Gates was amazed. "In the lore of Microsoft, if Bill says that to you, you're made". When subordinates appeared to be procrastinating, he was known to remark sarcastically, "I'll do it over the weekend". A 2019 New York Times article reported that Gates's relationship with financier Jeffrey Epstein started in 2011, a few years after Epstein was convicted for procuring a child for prostitution, and continued for some years, including a visit to Epstein's house with his wife in the fall of 2013, despite her declared discomfort. Gates said in 2011 about Epstein: "His lifestyle is very different and kind of intriguing although it would not work for me". The depth of the friendship between Gates and Epstein is unclear though Gates generally commented that "I met him. I didn't have any business relationship or friendship with him". However, Gates visited Epstein "many times, despite [Epstein's] past". It was reported that Epstein and Gates "discussed the Gates Foundation and philanthropy". Gates stated "Every meeting where I was with him were meetings with men. I was never at any parties or anything like that. He never donated any money to anything that I know about." In August 2021, Gates said the reason he had meetings with Epstein was because Gates hoped Epstein could provide money for philanthropic work, though nothing came of the idea. Gates added, "It was a huge mistake to spend time with him, to give him the credibility of being there." Gates came under further scrutiny after it was revealed that he had travelled on Epstein's private jet, though further claims about Gates travelling to Little Saint James proved unsubstantiated. It has also been reported that Epstein and Gates met with Nobel Committee chair Thorbjørn Jagland at his residence in Strasbourg, France, in March 2013 to discuss the Nobel Prize. Also in attendance were representatives of the International Peace Institute which has received millions in grants from the Gates Foundation, including a $2.5 million "community engagement" grant in October 2013. In 2023, it was reported that Epstein threatened to expose an alleged affair Gates had with a Russian bridge player. In December 2025, Gates appeared in two photos released by the House Oversight and Government Reform Committee from documents in Jeffrey Epstein's estate. These photos were part of thousands of other files ordered to be released pursuant to the Epstein Files Transparency Act. In January 2026, unsealed Epstein files revealed two 2013 draft emails by Epstein alleging Gates' extramarital affairs with "Russian girls" and "married women", resulting in him contracting an STD, and that an associate secretly obtained antibiotics for Melinda Gates while facilitating encounters. The emails accused Gates of ending their friendship after a failed Gates Foundation-JPMorgan deal and mentioned Epstein's resignation amid marital disputes and inappropriate activities. Unclear if sent and uncorroborated, the allegations were denied by Gates' spokesperson as "absolutely absurd and completely false", stemming from Epstein's frustration and efforts to "entrap and defame". It was also revealed that the emails by Epstein which involved discussion about Gates possibly contracting an STD and in need of antibiotics were in fact written on behalf of Boris Nikolić, an aggrieved employee of Gates who served as the Gates Foundation's chief advisor of science and technology, and was also planning to resign. Nikolic resigned from the Gates Foundation in 2014, and would also go on to serve as an executor to Epstein's estate. In February 2026, Gates cancelled his scheduled keynote address at the India AI Impact Summit hours before it was due to take place. According to multiple news reports, the withdrawal came amid renewed public scrutiny over his past associations with Jeffrey Epstein, although the Gates Foundation stated the decision was made to ensure the summit remained focused on its core priorities. In October 2025, Gates issued a statement saying that climate change does not pose an existential threat to civilization, stating that while it remains a serious problem, it was more important to give money to other causes such as solving poverty and improving healthcare. The statement was criticized by climate scientists, who stated that many of the issues Gates described as more of a priority result from climate change. Katharine Hayhoe said: "Climate change is not a separate bucket...The reason we care about climate change is that it's the hole in every bucket." According to prominent climate scientist Michael E. Mann: "There is no greater threat to developing nations than the climate crisis...He's got this all backwards." Gates's statement was received by some climate change deniers as proof that climate change is a "hoax". Donald Trump reacted by posting on social media that he had "just won the War on the Climate Change Hoax" because Gates had "finally admitted that he was completely WRONG on the issue." Gates responded to Trump's statement saying that it was "a gigantic misreading of the memo", telling Axios that he would actually increase his spending on climate and health. The memo came a day after the United Nations said humanity had missed the 1.5-degree target and warning of "devastating consequences", some of which are linked to tipping points, like in the Amazon, Greenland, Western Antarctica, and coral reefs. The memo was also released around the same time Hurricane Melissa, strengthened by climate change, struck the Caribbean islands whose damage was calculated as costing Jamaica alone 30%-250% of its annual GDP. The situation was worsened by hurricane affecting countries whose citizens are affected by the second Trump administration's deportation program, with analysts saying that the storm could increase migration. Approximately at the same time, a peer reviewed climate report warned that "we are hurtling toward climate chaos", and the number of scientific studies warning of societal collapse from climate change around said time was also rising. Awards and recognition Depiction in media Gates was the guest on BBC Radio 4's Desert Island Discs on January 31, 2016, in which he talked about his relationships with his father and Steve Jobs, meeting Melinda Ann French, the start of Microsoft and some of his habits (for example reading The Economist "from cover to cover every week"). His choice of things to take on a desert island were, for music: "Blue Skies" by Willie Nelson; a book: The Better Angels of Our Nature by Steven Pinker; and luxury item: a DVD Collection of Lectures from The Teaching Company. Gates starred as himself in a brief appearance on the Frasier episode "The Two Hundredth Episode". He also made a guest appearance as himself on the TV show The Big Bang Theory, in an episode titled "The Gates Excitation". He also appeared in a cameo role in 2019 on the series finale of Silicon Valley. Gates was parodied in The Simpsons episode "Das Bus". In 2023, Gates was the interviewee in an episode of the Amol Rajan Interviews series on BBC Two, and was the subject of an episode of the UK Channel 4 series The Billionaires Who Made Our World. In 2025, he also made guest appearance via video call in Hindi TV show Kyunki Saas Bhi Kabhi Bahu Thi 2. Books See also Notes References Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/Astronomical_radio_source] | [TOKENS: 1988] |
Contents Astronomical radio source An astronomical radio source is an object in outer space that emits strong radio waves. Radio emission comes from a wide variety of sources. Such objects are among the most extreme and energetic physical processes in the universe. History In 1932, American physicist and radio engineer Karl Jansky detected radio waves coming from an unknown source in the center of the Milky Way galaxy. Jansky was studying the origins of radio frequency interference for Bell Laboratories. He found "...a steady hiss type static of unknown origin", which eventually he concluded had an extraterrestrial origin. This was the first time that radio waves were detected from outer space. The first radio sky survey was conducted by Grote Reber and was completed in 1941. In the 1970s, some stars in the Milky Way were found to be radio emitters, one of the strongest being the unique binary MWC 349. Sources: Solar System As the nearest star, the Sun is the brightest radiation source in most frequencies, down to the radio spectrum at 300 MHz (1 m wavelength). When the Sun is quiet, the galactic background noise dominates at longer wavelengths. During geomagnetic storms, the Sun will dominate even at these low frequencies. Oscillation of electrons trapped in the magnetosphere of Jupiter produce strong radio signals, particularly bright in the decimeter band. The magnetosphere of Jupiter is responsible for intense episodes of radio emission from the planet's polar regions. Volcanic activity on Jupiter's moon Io injects gas into Jupiter's magnetosphere, producing a torus of particles about the planet. As Io moves through this torus, the interaction generates Alfvén waves that carry ionized matter into the polar regions of Jupiter. As a result, radio waves are generated through a cyclotron maser mechanism, and the energy is transmitted out along a cone-shaped surface. When Earth intersects this cone, the radio emissions from Jupiter can exceed the solar radio output. In 2021 news outlets reported that scientists, with the Juno spacecraft that orbits Jupiter since 2016, detected an FM radio signal from the moon Ganymede at a location where the planet's magnetic field lines connect with those of its moon. According to the reports these were caused by cyclotron maser instability and were similar to both WiFi-signals and Jupiter's radio emissions. A study about the radio emissions was published in September 2020 but did not describe them to be of FM nature or similar to WiFi signals.[clarification needed] Sources: Galactic The center of the Milky Way was the first radio source to be detected. It contains a number of radio sources, including Sagittarius A, the compact region around the supermassive black hole, Sagittarius A*, as well as the black hole itself. When flaring, the accretion disk around the supermassive black hole lights up, detectable in radio waves. In the 2000s, three Galactic Center Radio Transients (GCRTs) were detected: GCRT J1746–2757, GCRT J1745–3009, and GCRT J1742–3001. In addition, ASKAP J173608.2-321635, which was detected six times in 2020, may be a fourth GCRT. In 2021, astronomers reported the detection of peculiar, highly circularly polarized intermittent radio waves from near the Galactic Center whose unidentified source could represent a new class of astronomical objects with a GCRT so far not "fully explain[ing] the observations". Supernova remnants often show diffuse radio emission. Examples include Cassiopeia A, the brightest extrasolar radio source in the sky, and the Crab Nebula. Supernovae sometimes leave behind dense spinning neutron stars called pulsars. They emit jets of charged particles which emit synchrotron radiation in the radio spectrum. Examples include the Crab Pulsar, the first pulsar to be discovered. Pulsars and quasars (dense central cores of extremely distant galaxies) were both discovered by radio astronomers. In 2003 astronomers using the Parkes radio telescope discovered two pulsars orbiting each other, the first such system known. Rotating radio transients (RRATs) are a type of neutron stars discovered in 2006 by a team led by Maura McLaughlin from the Jodrell Bank Observatory at the University of Manchester in the UK. RRATs are believed to produce radio emissions which are very difficult to locate, because of their transient nature. Early efforts have been able to detect radio emissions (sometimes called RRAT flashes) for less than one second a day, and, like with other single-burst signals, one must take great care to distinguish them from terrestrial radio interference. Distributing computing and the Astropulse algorithm may thus lend itself to further detection of RRATs. Short radio waves are emitted from complex molecules in dense clouds of gas where stars are being born. Spiral galaxies contain clouds of neutral hydrogen and carbon monoxide which emit radio waves. The radio frequencies of these two molecules were used to map a large portion of the Milky Way galaxy. Sources: extra-galactic Many galaxies are strong radio emitters, called radio galaxies. Some of the more notable are Centaurus A and Messier 87. Quasars (short for "quasi-stellar radio source") were one of the first point-like radio sources to be discovered. Quasars' extreme redshift led us to conclude that they are distant active galactic nuclei, believed to be powered by black holes. Active galactic nuclei have jets of charged particles which emit synchrotron radiation. One example is 3C 273, the optically brightest quasar in the sky. Merging galaxy clusters often show diffuse radio emission. The cosmic microwave background is blackbody background radiation left over from the Big Bang (the rapid expansion, roughly 13.8 billion years ago, that was the beginning of the universe. D. R. Lorimer and others analyzed archival survey data and found a 30-jansky dispersed burst, less than 5 milliseconds in duration, located 3° from the Small Magellanic Cloud. They reported that the burst properties argue against a physical association with our Galaxy or the Small Magellanic Cloud. In a recent paper, they argue that current models for the free electron content in the universe imply that the burst is less than 1 gigaparsec distant. The fact that no further bursts were seen in 90 hours of additional observations implies that it was a singular event such as a supernova or coalescence (fusion) of relativistic objects. It is suggested that hundreds of similar events could occur every day and, if detected, could serve as cosmological probes. Radio pulsar surveys such as Astropulse-SETI@home offer one of the few opportunities to monitor the radio sky for impulsive burst-like events with millisecond durations. Because of the isolated nature of the observed phenomenon, the nature of the source remains speculative. Possibilities include a black hole-neutron star collision, a neutron star-neutron star collision, a black hole-black hole collision, or some phenomenon not yet considered. In 2010 there was a new report of 16 similar pulses from the Parkes Telescope which were clearly of terrestrial origin, but in 2013 four pulse sources were identified that supported the likelihood of a genuine extragalactic pulsing population. These pulses are known as fast radio bursts (FRBs). The first observed burst has become known as the Lorimer burst. Blitzars are one proposed explanation for them. Sources: not yet observed According to the Big Bang Model, during the first few moments after the Big Bang, pressure and temperature were extremely great. Under these conditions, simple fluctuations in the density of matter may have resulted in local regions dense enough to create black holes. Although most regions of high density would be quickly dispersed by the expansion of the universe, a primordial black hole would be stable, persisting to the present. One goal of Astropulse is to detect postulated mini black holes that might be evaporating due to "Hawking radiation". Such mini black holes are postulated to have been created during the Big Bang, unlike currently known black holes. Martin Rees has theorized that a black hole, exploding via Hawking radiation, might produce a signal that's detectable in the radio. The Astropulse project hopes that this evaporation would produce radio waves that Astropulse can detect. The evaporation wouldn't create radio waves directly. Instead, it would create an expanding fireball of high-energy gamma rays and particles. This fireball would interact with the surrounding magnetic field, pushing it out and generating radio waves. Previous searches by various "search for extraterrestrial intelligence" (SETI) projects, starting with Project Ozma, have looked for extraterrestrial communications in the form of narrow-band signals, analogous to our own radio stations. The Astropulse project argues that since we know nothing about how ET might communicate, this might be a bit closed-minded. Thus, the Astropulse Survey can be viewed[by whom?] as complementary to the narrow-band SETI@home survey as a by-product of the search for physical phenomena.[citation needed] Explaining their discovery in 2005 of a powerful bursting radio source, NRL astronomer Dr. Joseph Lazio stated: "Amazingly, even though the sky is known to be full of transient objects emitting at X- and gamma-ray wavelengths, very little has been done to look for radio bursts, which are often easier for astronomical objects to produce." The use of coherent dedispersion algorithms and the computing power provided by the SETI network may lead to discovery of previously undiscovered phenomena. See also References |
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[SOURCE: https://en.wikipedia.org/wiki/United_States#cite_note-184] | [TOKENS: 17273] |
Contents United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 states and a federal capital district, Washington, D.C. The 48 contiguous states border Canada to the north and Mexico to the south, with the semi-exclave of Alaska in the northwest and the archipelago of Hawaii in the Pacific Ocean. The United States also asserts sovereignty over five major island territories and various uninhabited islands in Oceania and the Caribbean.[j] It is a megadiverse country, with the world's third-largest land area[c] and third-largest population, exceeding 341 million.[k] Paleo-Indians first migrated from North Asia to North America at least 15,000 years ago, and formed various civilizations. Spanish colonization established Spanish Florida in 1513, the first European colony in what is now the continental United States. British colonization followed with the 1607 settlement of Virginia, the first of the Thirteen Colonies. Enslavement of Africans was practiced in all colonies by 1770 and supplied most of the labor for the Southern Colonies' plantation economy. Clashes with the British Crown began as a civil protest over the illegality of taxation without representation in Parliament and the denial of other English rights. They evolved into the American Revolution, which led to the Declaration of Independence and a society based on universal rights. Victory in the 1775–1783 Revolutionary War brought international recognition of U.S. sovereignty and fueled westward expansion, further dispossessing native inhabitants. As more states were admitted, a North–South division over slavery led the Confederate States of America to declare secession and fight the Union in the 1861–1865 American Civil War. With the United States' victory and reunification, slavery was abolished nationally. By the late 19th century, the U.S. economy outpaced the French, German and British economies combined. As of 1900, the country had established itself as a great power, a status solidified after its involvement in World War I. Following Japan's attack on Pearl Harbor in 1941, the U.S. entered World War II. Its aftermath left the U.S. and the Soviet Union as rival superpowers, competing for ideological dominance and international influence during the Cold War. The Soviet Union's collapse in 1991 ended the Cold War, leaving the U.S. as the world's sole superpower. The U.S. federal government is a representative democracy with a president and a constitution that grants separation of powers under three branches: legislative, executive, and judicial. The United States Congress is a bicameral national legislature composed of the House of Representatives (a lower house based on population) and the Senate (an upper house based on equal representation for each state). Federalism grants substantial autonomy to the 50 states. In addition, 574 Native American tribes have sovereignty rights, and there are 326 Native American reservations. Since the 1850s, the Democratic and Republican parties have dominated American politics. American ideals and values are based on a democratic tradition inspired by the American Enlightenment movement. A developed country, the U.S. ranks high in economic competitiveness, innovation, and higher education. Accounting for over a quarter of nominal global GDP, its economy has been the world's largest since about 1890. It is the wealthiest country, with the highest disposable household income per capita among OECD members, though its wealth inequality is highly pronounced. Shaped by centuries of immigration, the culture of the U.S. is diverse and globally influential. Making up more than a third of global military spending, the country has one of the strongest armed forces and is a designated nuclear state. A member of numerous international organizations, the U.S. plays a major role in global political, cultural, economic, and military affairs. Etymology Documented use of the phrase "United States of America" dates back to January 2, 1776. On that day, Stephen Moylan, a Continental Army aide to General George Washington, wrote a letter to Joseph Reed, Washington's aide-de-camp, seeking to go "with full and ample powers from the United States of America to Spain" to seek assistance in the Revolutionary War effort. The first known public usage is an anonymous essay published in the Williamsburg newspaper The Virginia Gazette on April 6, 1776. Sometime on or after June 11, 1776, Thomas Jefferson wrote "United States of America" in a rough draft of the Declaration of Independence, which was adopted by the Second Continental Congress on July 4, 1776. The term "United States" and its initialism "U.S.", used as nouns or as adjectives in English, are common short names for the country. The initialism "USA", a noun, is also common. "United States" and "U.S." are the established terms throughout the U.S. federal government, with prescribed rules.[l] "The States" is an established colloquial shortening of the name, used particularly from abroad; "stateside" is the corresponding adjective or adverb. "America" is the feminine form of the first word of Americus Vesputius, the Latinized name of Italian explorer Amerigo Vespucci (1454–1512);[m] it was first used as a place name by the German cartographers Martin Waldseemüller and Matthias Ringmann in 1507.[n] Vespucci first proposed that the West Indies discovered by Christopher Columbus in 1492 were part of a previously unknown landmass and not among the Indies at the eastern limit of Asia. In English, the term "America" usually does not refer to topics unrelated to the United States, despite the usage of "the Americas" to describe the totality of the continents of North and South America. History The first inhabitants of North America migrated from Siberia approximately 15,000 years ago, either across the Bering land bridge or along the now-submerged Ice Age coastline. Small isolated groups of hunter-gatherers are said to have migrated alongside herds of large herbivores far into Alaska, with ice-free corridors developing along the Pacific coast and valleys of North America in c. 16,500 – c. 13,500 BCE (c. 18,500 – c. 15,500 BP). The Clovis culture, which appeared around 11,000 BCE, is believed to be the first widespread culture in the Americas. Over time, Indigenous North American cultures grew increasingly sophisticated, and some, such as the Mississippian culture, developed agriculture, architecture, and complex societies. In the post-archaic period, the Mississippian cultures were located in the midwestern, eastern, and southern regions, and the Algonquian in the Great Lakes region and along the Eastern Seaboard, while the Hohokam culture and Ancestral Puebloans inhabited the Southwest. Native population estimates of what is now the United States before the arrival of European colonizers range from around 500,000 to nearly 10 million. Christopher Columbus began exploring the Caribbean for Spain in 1492, leading to Spanish-speaking settlements and missions from what are now Puerto Rico and Florida to New Mexico and California. The first Spanish colony in the present-day continental United States was Spanish Florida, chartered in 1513. After several settlements failed there due to starvation and disease, Spain's first permanent town, Saint Augustine, was founded in 1565. France established its own settlements in French Florida in 1562, but they were either abandoned (Charlesfort, 1578) or destroyed by Spanish raids (Fort Caroline, 1565). Permanent French settlements were founded much later along the Great Lakes (Fort Detroit, 1701), the Mississippi River (Saint Louis, 1764) and especially the Gulf of Mexico (New Orleans, 1718). Early European colonies also included the thriving Dutch colony of New Nederland (settled 1626, present-day New York) and the small Swedish colony of New Sweden (settled 1638 in what became Delaware). British colonization of the East Coast began with the Virginia Colony (1607) and the Plymouth Colony (Massachusetts, 1620). The Mayflower Compact in Massachusetts and the Fundamental Orders of Connecticut established precedents for local representative self-governance and constitutionalism that would develop throughout the American colonies. While European settlers in what is now the United States experienced conflicts with Native Americans, they also engaged in trade, exchanging European tools for food and animal pelts.[o] Relations ranged from close cooperation to warfare and massacres. The colonial authorities often pursued policies that forced Native Americans to adopt European lifestyles, including conversion to Christianity. Along the eastern seaboard, settlers trafficked Africans through the Atlantic slave trade, largely to provide manual labor on plantations. The original Thirteen Colonies[p] that would later found the United States were administered as possessions of the British Empire by Crown-appointed governors, though local governments held elections open to most white male property owners. The colonial population grew rapidly from Maine to Georgia, eclipsing Native American populations; by the 1770s, the natural increase of the population was such that only a small minority of Americans had been born overseas. The colonies' distance from Britain facilitated the entrenchment of self-governance, and the First Great Awakening, a series of Christian revivals, fueled colonial interest in guaranteed religious liberty. Following its victory in the French and Indian War, Britain began to assert greater control over local affairs in the Thirteen Colonies, resulting in growing political resistance. One of the primary grievances of the colonists was the denial of their rights as Englishmen, particularly the right to representation in the British government that taxed them. To demonstrate their dissatisfaction and resolve, the First Continental Congress met in 1774 and passed the Continental Association, a colonial boycott of British goods enforced by local "committees of safety" that proved effective. The British attempt to then disarm the colonists resulted in the 1775 Battles of Lexington and Concord, igniting the American Revolutionary War. At the Second Continental Congress, the colonies appointed George Washington commander-in-chief of the Continental Army, and created a committee that named Thomas Jefferson to draft the Declaration of Independence. Two days after the Second Continental Congress passed the Lee Resolution to create an independent, sovereign nation, the Declaration was adopted on July 4, 1776. The political values of the American Revolution evolved from an armed rebellion demanding reform within an empire to a revolution that created a new social and governing system founded on the defense of liberty and the protection of inalienable natural rights; sovereignty of the people; republicanism over monarchy, aristocracy, and other hereditary political power; civic virtue; and an intolerance of political corruption. The Founding Fathers of the United States, who included Washington, Jefferson, John Adams, Benjamin Franklin, Alexander Hamilton, John Jay, James Madison, Thomas Paine, and many others, were inspired by Classical, Renaissance, and Enlightenment philosophies and ideas. Though in practical effect since its drafting in 1777, the Articles of Confederation was ratified in 1781 and formally established a decentralized government that operated until 1789. After the British surrender at the siege of Yorktown in 1781, American sovereignty was internationally recognized by the Treaty of Paris (1783), through which the U.S. gained territory stretching west to the Mississippi River, north to present-day Canada, and south to Spanish Florida. The Northwest Ordinance (1787) established the precedent by which the country's territory would expand with the admission of new states, rather than the expansion of existing states. The U.S. Constitution was drafted at the 1787 Constitutional Convention to overcome the limitations of the Articles. It went into effect in 1789, creating a federal republic governed by three separate branches that together formed a system of checks and balances. George Washington was elected the country's first president under the Constitution, and the Bill of Rights was adopted in 1791 to allay skeptics' concerns about the power of the more centralized government. His resignation as commander-in-chief after the Revolutionary War and his later refusal to run for a third term as the country's first president established a precedent for the supremacy of civil authority in the United States and the peaceful transfer of power. In the late 18th century, American settlers began to expand westward in larger numbers, many with a sense of manifest destiny. The Louisiana Purchase of 1803 from France nearly doubled the territory of the United States. Lingering issues with Britain remained, leading to the War of 1812, which was fought to a draw. Spain ceded Florida and its Gulf Coast territory in 1819. The Missouri Compromise of 1820, which admitted Missouri as a slave state and Maine as a free state, attempted to balance the desire of northern states to prevent the expansion of slavery into new territories with that of southern states to extend it there. Primarily, the compromise prohibited slavery in all other lands of the Louisiana Purchase north of the 36°30′ parallel. As Americans expanded further into territory inhabited by Native Americans, the federal government implemented policies of Indian removal or assimilation. The most significant such legislation was the Indian Removal Act of 1830, a key policy of President Andrew Jackson. It resulted in the Trail of Tears (1830–1850), in which an estimated 60,000 Native Americans living east of the Mississippi River were forcibly removed and displaced to lands far to the west, causing 13,200 to 16,700 deaths along the forced march. Settler expansion as well as this influx of Indigenous peoples from the East resulted in the American Indian Wars west of the Mississippi. During the colonial period, slavery became legal in all the Thirteen colonies, but by 1770 it provided the main labor force in the large-scale, agriculture-dependent economies of the Southern Colonies from Maryland to Georgia. The practice began to be significantly questioned during the American Revolution, and spurred by an active abolitionist movement that had reemerged in the 1830s, states in the North enacted laws to prohibit slavery within their boundaries. At the same time, support for slavery had strengthened in Southern states, with widespread use of inventions such as the cotton gin (1793) having made slavery immensely profitable for Southern elites. The United States annexed the Republic of Texas in 1845, and the 1846 Oregon Treaty led to U.S. control of the present-day American Northwest. Dispute with Mexico over Texas led to the Mexican–American War (1846–1848). After the victory of the U.S., Mexico recognized U.S. sovereignty over Texas, New Mexico, and California in the 1848 Mexican Cession; the cession's lands also included the future states of Nevada, Colorado and Utah. The California gold rush of 1848–1849 spurred a huge migration of white settlers to the Pacific coast, leading to even more confrontations with Native populations. One of the most violent, the California genocide of thousands of Native inhabitants, lasted into the mid-1870s. Additional western territories and states were created. Throughout the 1850s, the sectional conflict regarding slavery was further inflamed by national legislation in the U.S. Congress and decisions of the Supreme Court. In Congress, the Fugitive Slave Act of 1850 mandated the forcible return to their owners in the South of slaves taking refuge in non-slave states, while the Kansas–Nebraska Act of 1854 effectively gutted the anti-slavery requirements of the Missouri Compromise. In its Dred Scott decision of 1857, the Supreme Court ruled against a slave brought into non-slave territory, simultaneously declaring the entire Missouri Compromise to be unconstitutional. These and other events exacerbated tensions between North and South that would culminate in the American Civil War (1861–1865). Beginning with South Carolina, 11 slave-state governments voted to secede from the United States in 1861, joining to create the Confederate States of America. All other state governments remained loyal to the Union.[q] War broke out in April 1861 after the Confederacy bombarded Fort Sumter. Following the Emancipation Proclamation on January 1, 1863, many freed slaves joined the Union army. The war began to turn in the Union's favor following the 1863 Siege of Vicksburg and Battle of Gettysburg, and the Confederates surrendered in 1865 after the Union's victory in the Battle of Appomattox Court House. Efforts toward reconstruction in the secessionist South had begun as early as 1862, but it was only after President Lincoln's assassination that the three Reconstruction Amendments to the Constitution were ratified to protect civil rights. The amendments codified nationally the abolition of slavery and involuntary servitude except as punishment for crimes, promised equal protection under the law for all persons, and prohibited discrimination on the basis of race or previous enslavement. As a result, African Americans took an active political role in ex-Confederate states in the decade following the Civil War. The former Confederate states were readmitted to the Union, beginning with Tennessee in 1866 and ending with Georgia in 1870. National infrastructure, including transcontinental telegraph and railroads, spurred growth in the American frontier. This was accelerated by the Homestead Acts, through which nearly 10 percent of the total land area of the United States was given away free to some 1.6 million homesteaders. From 1865 through 1917, an unprecedented stream of immigrants arrived in the United States, including 24.4 million from Europe. Most came through the Port of New York, as New York City and other large cities on the East Coast became home to large Jewish, Irish, and Italian populations. Many Northern Europeans as well as significant numbers of Germans and other Central Europeans moved to the Midwest. At the same time, about one million French Canadians migrated from Quebec to New England. During the Great Migration, millions of African Americans left the rural South for urban areas in the North. Alaska was purchased from Russia in 1867. The Compromise of 1877 is generally considered the end of the Reconstruction era, as it resolved the electoral crisis following the 1876 presidential election and led President Rutherford B. Hayes to reduce the role of federal troops in the South. Immediately, the Redeemers began evicting the Carpetbaggers and quickly regained local control of Southern politics in the name of white supremacy. African Americans endured a period of heightened, overt racism following Reconstruction, a time often considered the nadir of American race relations. A series of Supreme Court decisions, including Plessy v. Ferguson, emptied the Fourteenth and Fifteenth Amendments of their force, allowing Jim Crow laws in the South to remain unchecked, sundown towns in the Midwest, and segregation in communities across the country, which would be reinforced in part by the policy of redlining later adopted by the federal Home Owners' Loan Corporation. An explosion of technological advancement, accompanied by the exploitation of cheap immigrant labor, led to rapid economic expansion during the Gilded Age of the late 19th century. It continued into the early 20th, when the United States already outpaced the economies of Britain, France, and Germany combined. This fostered the amassing of power by a few prominent industrialists, largely by their formation of trusts and monopolies to prevent competition. Tycoons led the nation's expansion in the railroad, petroleum, and steel industries. The United States emerged as a pioneer of the automotive industry. These changes resulted in significant increases in economic inequality, slum conditions, and social unrest, creating the environment for labor unions and socialist movements to begin to flourish. This period eventually ended with the advent of the Progressive Era, which was characterized by significant economic and social reforms. Pro-American elements in Hawaii overthrew the Hawaiian monarchy; the islands were annexed in 1898. That same year, Puerto Rico, the Philippines, and Guam were ceded to the U.S. by Spain after the latter's defeat in the Spanish–American War. (The Philippines was granted full independence from the U.S. on July 4, 1946, following World War II. Puerto Rico and Guam have remained U.S. territories.) American Samoa was acquired by the United States in 1900 after the Second Samoan Civil War. The U.S. Virgin Islands were purchased from Denmark in 1917. The United States entered World War I alongside the Allies in 1917 helping to turn the tide against the Central Powers. In 1920, a constitutional amendment granted nationwide women's suffrage. During the 1920s and 1930s, radio for mass communication and early television transformed communications nationwide. The Wall Street Crash of 1929 triggered the Great Depression, to which President Franklin D. Roosevelt responded with the New Deal plan of "reform, recovery and relief", a series of unprecedented and sweeping recovery programs and employment relief projects combined with financial reforms and regulations. Initially neutral during World War II, the U.S. began supplying war materiel to the Allies of World War II in March 1941 and entered the war in December after Japan's attack on Pearl Harbor. Agreeing to a "Europe first" policy, the U.S. concentrated its wartime efforts on Japan's allies Italy and Germany until their final defeat in May 1945. The U.S. developed the first nuclear weapons and used them against the Japanese cities of Hiroshima and Nagasaki in August 1945, ending the war. The United States was one of the "Four Policemen" who met to plan the post-war world, alongside the United Kingdom, the Soviet Union, and China. The U.S. emerged relatively unscathed from the war, with even greater economic power and international political influence. The end of World War II in 1945 left the U.S. and the Soviet Union as superpowers, each with its own political, military, and economic sphere of influence. Geopolitical tensions between the two superpowers soon led to the Cold War. The U.S. implemented a policy of containment intended to limit the Soviet Union's sphere of influence; engaged in regime change against governments perceived to be aligned with the Soviets; and prevailed in the Space Race, which culminated with the first crewed Moon landing in 1969. Domestically, the U.S. experienced economic growth, urbanization, and population growth following World War II. The civil rights movement emerged, with Martin Luther King Jr. becoming a prominent leader in the early 1960s. The Great Society plan of President Lyndon B. Johnson's administration resulted in groundbreaking and broad-reaching laws, policies and a constitutional amendment to counteract some of the worst effects of lingering institutional racism. The counterculture movement in the U.S. brought significant social changes, including the liberalization of attitudes toward recreational drug use and sexuality. It also encouraged open defiance of the military draft (leading to the end of conscription in 1973) and wide opposition to U.S. intervention in Vietnam, with the U.S. totally withdrawing in 1975. A societal shift in the roles of women was significantly responsible for the large increase in female paid labor participation starting in the 1970s, and by 1985 the majority of American women aged 16 and older were employed. The Fall of Communism and the dissolution of the Soviet Union from 1989 to 1991 marked the end of the Cold War and left the United States as the world's sole superpower. This cemented the United States' global influence, reinforcing the concept of the "American Century" as the U.S. dominated international political, cultural, economic, and military affairs. The 1990s saw the longest recorded economic expansion in American history, a dramatic decline in U.S. crime rates, and advances in technology. Throughout this decade, technological innovations such as the World Wide Web, the evolution of the Pentium microprocessor in accordance with Moore's law, rechargeable lithium-ion batteries, the first gene therapy trial, and cloning either emerged in the U.S. or were improved upon there. The Human Genome Project was formally launched in 1990, while Nasdaq became the first stock market in the United States to trade online in 1998. In the Gulf War of 1991, an American-led international coalition of states expelled an Iraqi invasion force that had occupied neighboring Kuwait. The September 11 attacks on the United States in 2001 by the pan-Islamist militant organization al-Qaeda led to the war on terror and subsequent military interventions in Afghanistan and in Iraq. The U.S. housing bubble culminated in 2007 with the Great Recession, the largest economic contraction since the Great Depression. In the 2010s and early 2020s, the United States has experienced increased political polarization and democratic backsliding. The country's polarization was violently reflected in the January 2021 Capitol attack, when a mob of insurrectionists entered the U.S. Capitol and sought to prevent the peaceful transfer of power in an attempted self-coup d'état. Geography The United States is the world's third-largest country by total area behind Russia and Canada.[c] The 48 contiguous states and the District of Columbia have a combined area of 3,119,885 square miles (8,080,470 km2). In 2021, the United States had 8% of the Earth's permanent meadows and pastures and 10% of its cropland. Starting in the east, the coastal plain of the Atlantic seaboard gives way to inland forests and rolling hills in the Piedmont plateau region. The Appalachian Mountains and the Adirondack Massif separate the East Coast from the Great Lakes and the grasslands of the Midwest. The Mississippi River System, the world's fourth-longest river system, runs predominantly north–south through the center of the country. The flat and fertile prairie of the Great Plains stretches to the west, interrupted by a highland region in the southeast. The Rocky Mountains, west of the Great Plains, extend north to south across the country, peaking at over 14,000 feet (4,300 m) in Colorado. The supervolcano underlying Yellowstone National Park in the Rocky Mountains, the Yellowstone Caldera, is the continent's largest volcanic feature. Farther west are the rocky Great Basin and the Chihuahuan, Sonoran, and Mojave deserts. In the northwest corner of Arizona, carved by the Colorado River, is the Grand Canyon, a steep-sided canyon and popular tourist destination known for its overwhelming visual size and intricate, colorful landscape. The Cascade and Sierra Nevada mountain ranges run close to the Pacific coast. The lowest and highest points in the contiguous United States are in the State of California, about 84 miles (135 km) apart. At an elevation of 20,310 feet (6,190.5 m), Alaska's Denali (also called Mount McKinley) is the highest peak in the country and on the continent. Active volcanoes in the U.S. are common throughout Alaska's Alexander and Aleutian Islands. Located entirely outside North America, the archipelago of Hawaii consists of volcanic islands, physiographically and ethnologically part of the Polynesian subregion of Oceania. In addition to its total land area, the United States has one of the world's largest marine exclusive economic zones spanning approximately 4.5 million square miles (11.7 million km2) of ocean. With its large size and geographic variety, the United States includes most climate types. East of the 100th meridian, the climate ranges from humid continental in the north to humid subtropical in the south. The western Great Plains are semi-arid. Many mountainous areas of the American West have an alpine climate. The climate is arid in the Southwest, Mediterranean in coastal California, and oceanic in coastal Oregon, Washington, and southern Alaska. Most of Alaska is subarctic or polar. Hawaii, the southern tip of Florida and U.S. territories in the Caribbean and Pacific are tropical. The United States receives more high-impact extreme weather incidents than any other country. States bordering the Gulf of Mexico are prone to hurricanes, and most of the world's tornadoes occur in the country, mainly in Tornado Alley. Due to climate change in the country, extreme weather has become more frequent in the U.S. in the 21st century, with three times the number of reported heat waves compared to the 1960s. Since the 1990s, droughts in the American Southwest have become more persistent and more severe. The regions considered as the most attractive to the population are the most vulnerable. The U.S. is one of 17 megadiverse countries containing large numbers of endemic species: about 17,000 species of vascular plants occur in the contiguous United States and Alaska, and over 1,800 species of flowering plants are found in Hawaii, few of which occur on the mainland. The United States is home to 428 mammal species, 784 birds, 311 reptiles, 295 amphibians, and around 91,000 insect species. There are 63 national parks, and hundreds of other federally managed monuments, forests, and wilderness areas, administered by the National Park Service and other agencies. About 28% of the country's land is publicly owned and federally managed, primarily in the Western States. Most of this land is protected, though some is leased for commercial use, and less than one percent is used for military purposes. Environmental issues in the United States include debates on non-renewable resources and nuclear energy, air and water pollution, biodiversity, logging and deforestation, and climate change. The U.S. Environmental Protection Agency (EPA) is the federal agency charged with addressing most environmental-related issues. The idea of wilderness has shaped the management of public lands since 1964, with the Wilderness Act. The Endangered Species Act of 1973 provides a way to protect threatened and endangered species and their habitats. The United States Fish and Wildlife Service implements and enforces the Act. In 2024, the U.S. ranked 35th among 180 countries in the Environmental Performance Index. Government and politics The United States is a federal republic of 50 states and a federal capital district, Washington, D.C. The U.S. asserts sovereignty over five unincorporated territories and several uninhabited island possessions. It is the world's oldest surviving federation, and its presidential system of federal government has been adopted, in whole or in part, by many newly independent states worldwide following their decolonization. The Constitution of the United States serves as the country's supreme legal document. Most scholars describe the United States as a liberal democracy.[r] Composed of three branches, all headquartered in Washington, D.C., the federal government is the national government of the United States. The U.S. Constitution establishes a separation of powers intended to provide a system of checks and balances to prevent any of the three branches from becoming supreme. The three-branch system is known as the presidential system, in contrast to the parliamentary system where the executive is part of the legislative body. Many countries around the world adopted this aspect of the 1789 Constitution of the United States, especially in the postcolonial Americas. In the U.S. federal system, sovereign powers are shared between three levels of government specified in the Constitution: the federal government, the states, and Indian tribes. The U.S. also asserts sovereignty over five permanently inhabited territories: American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the U.S. Virgin Islands. Residents of the 50 states are governed by their elected state government, under state constitutions compatible with the national constitution, and by elected local governments that are administrative divisions of a state. States are subdivided into counties or county equivalents, and (except for Hawaii) further divided into municipalities, each administered by elected representatives. The District of Columbia is a federal district containing the U.S. capital, Washington, D.C. The federal district is an administrative division of the federal government. Indian country is made up of 574 federally recognized tribes and 326 Indian reservations. They hold a government-to-government relationship with the U.S. federal government in Washington and are legally defined as domestic dependent nations with inherent tribal sovereignty rights. In addition to the five major territories, the U.S. also asserts sovereignty over the United States Minor Outlying Islands in the Pacific Ocean and the Caribbean. The seven undisputed islands without permanent populations are Baker Island, Howland Island, Jarvis Island, Johnston Atoll, Kingman Reef, Midway Atoll, and Palmyra Atoll. U.S. sovereignty over the unpopulated Bajo Nuevo Bank, Navassa Island, Serranilla Bank, and Wake Island is disputed. The Constitution is silent on political parties. However, they developed independently in the 18th century with the Federalist and Anti-Federalist parties. Since then, the United States has operated as a de facto two-party system, though the parties have changed over time. Since the mid-19th century, the two main national parties have been the Democratic Party and the Republican Party. The former is perceived as relatively liberal in its political platform while the latter is perceived as relatively conservative in its platform. The United States has an established structure of foreign relations, with the world's second-largest diplomatic corps as of 2024[update]. It is a permanent member of the United Nations Security Council and home to the United Nations headquarters. The United States is a member of the G7, G20, and OECD intergovernmental organizations. Almost all countries have embassies and many have consulates (official representatives) in the country. Likewise, nearly all countries host formal diplomatic missions with the United States, except Iran, North Korea, and Bhutan. Though Taiwan does not have formal diplomatic relations with the U.S., it maintains close unofficial relations. The United States regularly supplies Taiwan with military equipment to deter potential Chinese aggression. Its geopolitical attention also turned to the Indo-Pacific when the United States joined the Quadrilateral Security Dialogue with Australia, India, and Japan. The United States has a "Special Relationship" with the United Kingdom and strong ties with Canada, Australia, New Zealand, the Philippines, Japan, South Korea, Israel, and several European Union countries such as France, Italy, Germany, Spain, and Poland. The U.S. works closely with its NATO allies on military and national security issues, and with countries in the Americas through the Organization of American States and the United States–Mexico–Canada Free Trade Agreement. The U.S. exercises full international defense authority and responsibility for Micronesia, the Marshall Islands, and Palau through the Compact of Free Association. It has increasingly conducted strategic cooperation with India, while its ties with China have steadily deteriorated. Beginning in 2014, the U.S. had become a key ally of Ukraine. After Donald Trump was elected U.S. president in 2024, he sought to negotiate an end to the Russo-Ukrainian War. He paused all military aid to Ukraine in March 2025, although the aid resumed later. Trump also ended U.S. intelligence sharing with the country, but this too was eventually restored. The president is the commander-in-chief of the United States Armed Forces and appoints its leaders, the secretary of defense and the Joint Chiefs of Staff. The Department of Defense, headquartered at the Pentagon near Washington, D.C., administers five of the six service branches, which are made up of the U.S. Army, Marine Corps, Navy, Air Force, and Space Force. The Coast Guard is administered by the Department of Homeland Security in peacetime and can be transferred to the Department of the Navy in wartime. Total strength of the entire military is about 1.3 million active duty with an additional 400,000 in reserve. The United States spent $997 billion on its military in 2024, which is by far the largest amount of any country, making up 37% of global military spending and accounting for 3.4% of the country's GDP. The U.S. possesses 42% of the world's nuclear weapons—the second-largest stockpile after that of Russia. The U.S. military is widely regarded as the most powerful and advanced in the world. The United States has the third-largest combined armed forces in the world, behind the Chinese People's Liberation Army and Indian Armed Forces. The U.S. military operates about 800 bases and facilities abroad, and maintains deployments greater than 100 active duty personnel in 25 foreign countries. The United States has engaged in over 400 military interventions since its founding in 1776, with over half of these occurring between 1950 and 2019 and 25% occurring in the post-Cold War era. State defense forces (SDFs) are military units that operate under the sole authority of a state government. SDFs are authorized by state and federal law but are under the command of the state's governor. By contrast, the 54 U.S. National Guard organizations[t] fall under the dual control of state or territorial governments and the federal government; their units can also become federalized entities, but SDFs cannot be federalized. The National Guard personnel of a state or territory can be federalized by the president under the National Defense Act Amendments of 1933; this legislation created the Guard and provides for the integration of Army National Guard and Air National Guard units and personnel into the U.S. Army and (since 1947) the U.S. Air Force. The total number of National Guard members is about 430,000, while the estimated combined strength of SDFs is less than 10,000. There are about 18,000 U.S. police agencies from local to national level in the United States. Law in the United States is mainly enforced by local police departments and sheriff departments in their municipal or county jurisdictions. The state police departments have authority in their respective state, and federal agencies such as the Federal Bureau of Investigation (FBI) and the U.S. Marshals Service have national jurisdiction and specialized duties, such as protecting civil rights, national security, enforcing U.S. federal courts' rulings and federal laws, and interstate criminal activity. State courts conduct almost all civil and criminal trials, while federal courts adjudicate the much smaller number of civil and criminal cases that relate to federal law. There is no unified "criminal justice system" in the United States. The American prison system is largely heterogenous, with thousands of relatively independent systems operating across federal, state, local, and tribal levels. In 2025, "these systems hold nearly 2 million people in 1,566 state prisons, 98 federal prisons, 3,116 local jails, 1,277 juvenile correctional facilities, 133 immigration detention facilities, and 80 Indian country jails, as well as in military prisons, civil commitment centers, state psychiatric hospitals, and prisons in the U.S. territories." Despite disparate systems of confinement, four main institutions dominate: federal prisons, state prisons, local jails, and juvenile correctional facilities. Federal prisons are run by the Federal Bureau of Prisons and hold pretrial detainees as well as people who have been convicted of federal crimes. State prisons, run by the department of corrections of each state, hold people sentenced and serving prison time (usually longer than one year) for felony offenses. Local jails are county or municipal facilities that incarcerate defendants prior to trial; they also hold those serving short sentences (typically under a year). Juvenile correctional facilities are operated by local or state governments and serve as longer-term placements for any minor adjudicated as delinquent and ordered by a judge to be confined. In January 2023, the United States had the sixth-highest per capita incarceration rate in the world—531 people per 100,000 inhabitants—and the largest prison and jail population in the world, with more than 1.9 million people incarcerated. An analysis of the World Health Organization Mortality Database from 2010 showed U.S. homicide rates "were 7 times higher than in other high-income countries, driven by a gun homicide rate that was 25 times higher". Economy The U.S. has a highly developed mixed economy that has been the world's largest nominally since about 1890. Its 2024 gross domestic product (GDP)[e] of more than $29 trillion constituted over 25% of nominal global economic output, or 15% at purchasing power parity (PPP). From 1983 to 2008, U.S. real compounded annual GDP growth was 3.3%, compared to a 2.3% weighted average for the rest of the G7. The country ranks first in the world by nominal GDP, second when adjusted for purchasing power parities (PPP), and ninth by PPP-adjusted GDP per capita. In February 2024, the total U.S. federal government debt was $34.4 trillion. Of the world's 500 largest companies by revenue, 138 were headquartered in the U.S. in 2025, the highest number of any country. The U.S. dollar is the currency most used in international transactions and the world's foremost reserve currency, backed by the country's dominant economy, its military, the petrodollar system, its large U.S. treasuries market, and its linked eurodollar. Several countries use it as their official currency, and in others it is the de facto currency. The U.S. has free trade agreements with several countries, including the USMCA. Although the United States has reached a post-industrial level of economic development and is often described as having a service economy, it remains a major industrial power; in 2024, the U.S. manufacturing sector was the world's second-largest by value output after China's. New York City is the world's principal financial center, and its metropolitan area is the world's largest metropolitan economy. The New York Stock Exchange and Nasdaq, both located in New York City, are the world's two largest stock exchanges by market capitalization and trade volume. The United States is at the forefront of technological advancement and innovation in many economic fields, especially in artificial intelligence; electronics and computers; pharmaceuticals; and medical, aerospace and military equipment. The country's economy is fueled by abundant natural resources, a well-developed infrastructure, and high productivity. The largest trading partners of the United States are the European Union, Mexico, Canada, China, Japan, South Korea, the United Kingdom, Vietnam, India, and Taiwan. The United States is the world's largest importer and second-largest exporter.[u] It is by far the world's largest exporter of services. Americans have the highest average household and employee income among OECD member states, and the fourth-highest median household income in 2023, up from sixth-highest in 2013. With personal consumption expenditures of over $18.5 trillion in 2023, the U.S. has a heavily consumer-driven economy and is the world's largest consumer market. The U.S. ranked first in the number of dollar billionaires and millionaires in 2023, with 735 billionaires and nearly 22 million millionaires. Wealth in the United States is highly concentrated; in 2011, the richest 10% of the adult population owned 72% of the country's household wealth, while the bottom 50% owned just 2%. U.S. wealth inequality increased substantially since the late 1980s, and income inequality in the U.S. reached a record high in 2019. In 2024, the country had some of the highest wealth and income inequality levels among OECD countries. Since the 1970s, there has been a decoupling of U.S. wage gains from worker productivity. In 2016, the top fifth of earners took home more than half of all income, giving the U.S. one of the widest income distributions among OECD countries. There were about 771,480 homeless persons in the U.S. in 2024. In 2022, 6.4 million children experienced food insecurity. Feeding America estimates that around one in five, or approximately 13 million, children experience hunger in the U.S. and do not know where or when they will get their next meal. Also in 2022, about 37.9 million people, or 11.5% of the U.S. population, were living in poverty. The United States has a smaller welfare state and redistributes less income through government action than most other high-income countries. It is the only advanced economy that does not guarantee its workers paid vacation nationally and one of a few countries in the world without federal paid family leave as a legal right. The United States has a higher percentage of low-income workers than almost any other developed country, largely because of a weak collective bargaining system and lack of government support for at-risk workers. The United States has been a leader in technological innovation since the late 19th century and scientific research since the mid-20th century. Methods for producing interchangeable parts and the establishment of a machine tool industry enabled the large-scale manufacturing of U.S. consumer products in the late 19th century. By the early 20th century, factory electrification, the introduction of the assembly line, and other labor-saving techniques created the system of mass production. In the 21st century, the United States continues to be one of the world's foremost scientific powers, though China has emerged as a major competitor in many fields. The U.S. has the highest research and development expenditures of any country and ranks ninth as a percentage of GDP. In 2022, the United States was (after China) the country with the second-highest number of published scientific papers. In 2021, the U.S. ranked second (also after China) by the number of patent applications, and third by trademark and industrial design applications (after China and Germany), according to World Intellectual Property Indicators. In 2025 the United States ranked third (after Switzerland and Sweden) in the Global Innovation Index. The United States is considered to be a world leader in the development of artificial intelligence technology. In 2023, the United States was ranked the second most technologically advanced country in the world (after South Korea) by Global Finance magazine. The United States has maintained a space program since the late 1950s, beginning with the establishment of the National Aeronautics and Space Administration (NASA) in 1958. NASA's Apollo program (1961–1972) achieved the first crewed Moon landing with the 1969 Apollo 11 mission; it remains one of the agency's most significant milestones. Other major endeavors by NASA include the Space Shuttle program (1981–2011), the Voyager program (1972–present), the Hubble and James Webb space telescopes (launched in 1990 and 2021, respectively), and the multi-mission Mars Exploration Program (Spirit and Opportunity, Curiosity, and Perseverance). NASA is one of five agencies collaborating on the International Space Station (ISS); U.S. contributions to the ISS include several modules, including Destiny (2001), Harmony (2007), and Tranquility (2010), as well as ongoing logistical and operational support. The United States private sector dominates the global commercial spaceflight industry. Prominent American spaceflight contractors include Blue Origin, Boeing, Lockheed Martin, Northrop Grumman, and SpaceX. NASA programs such as the Commercial Crew Program, Commercial Resupply Services, Commercial Lunar Payload Services, and NextSTEP have facilitated growing private-sector involvement in American spaceflight. In 2023, the United States received approximately 84% of its energy from fossil fuel, and its largest source of energy was petroleum (38%), followed by natural gas (36%), renewable sources (9%), coal (9%), and nuclear power (9%). In 2022, the United States constituted about 4% of the world's population, but consumed around 16% of the world's energy. The U.S. ranks as the second-highest emitter of greenhouse gases behind China. The U.S. is the world's largest producer of nuclear power, generating around 30% of the world's nuclear electricity. It also has the highest number of nuclear power reactors of any country. From 2024, the U.S. plans to triple its nuclear power capacity by 2050. The United States' 4 million miles (6.4 million kilometers) of road network, owned almost entirely by state and local governments, is the longest in the world. The extensive Interstate Highway System that connects all major U.S. cities is funded mostly by the federal government but maintained by state departments of transportation. The system is further extended by state highways and some private toll roads. The U.S. is among the top ten countries with the highest vehicle ownership per capita (850 vehicles per 1,000 people) in 2022. A 2022 study found that 76% of U.S. commuters drive alone and 14% ride a bicycle, including bike owners and users of bike-sharing networks. About 11% use some form of public transportation. Public transportation in the United States is well developed in the largest urban areas, notably New York City, Washington, D.C., Boston, Philadelphia, Chicago, and San Francisco; otherwise, coverage is generally less extensive than in most other developed countries. The U.S. also has many relatively car-dependent localities. Long-distance intercity travel is provided primarily by airlines, but travel by rail is more common along the Northeast Corridor, the only high-speed rail in the U.S. that meets international standards. Amtrak, the country's government-sponsored national passenger rail company, has a relatively sparse network compared to that of Western European countries. Service is concentrated in the Northeast, California, the Midwest, the Pacific Northwest, and Virginia/Southeast. The United States has an extensive air transportation network. U.S. civilian airlines are all privately owned. The three largest airlines in the world, by total number of passengers carried, are U.S.-based; American Airlines became the global leader after its 2013 merger with US Airways. Of the 50 busiest airports in the world, 16 are in the United States, as well as five of the top 10. The world's busiest airport by passenger volume is Hartsfield–Jackson Atlanta International in Atlanta, Georgia. In 2022, most of the 19,969 U.S. airports were owned and operated by local government authorities, and there are also some private airports. Some 5,193 are designated as "public use", including for general aviation. The Transportation Security Administration (TSA) has provided security at most major airports since 2001. The country's rail transport network, the longest in the world at 182,412.3 mi (293,564.2 km), handles mostly freight (in contrast to more passenger-centered rail in Europe). Because they are often privately owned operations, U.S. railroads lag behind those of the rest of the world in terms of electrification. The country's inland waterways are the world's fifth-longest, totaling 25,482 mi (41,009 km). They are used extensively for freight, recreation, and a small amount of passenger traffic. Of the world's 50 busiest container ports, four are located in the United States, with the busiest in the country being the Port of Los Angeles. Demographics The U.S. Census Bureau reported 331,449,281 residents on April 1, 2020,[v] making the United States the third-most-populous country in the world, after India and China. The Census Bureau's official 2025 population estimate was 341,784,857, an increase of 3.1% since the 2020 census. According to the Bureau's U.S. Population Clock, on July 1, 2024, the U.S. population had a net gain of one person every 16 seconds, or about 5400 people per day. In 2023, 51% of Americans age 15 and over were married, 6% were widowed, 10% were divorced, and 34% had never been married. In 2023, the total fertility rate for the U.S. stood at 1.6 children per woman, and, at 23%, it had the world's highest rate of children living in single-parent households in 2019. Most Americans live in the suburbs of major metropolitan areas. The United States has a diverse population; 37 ancestry groups have more than one million members. White Americans with ancestry from Europe, the Middle East, or North Africa form the largest racial and ethnic group at 57.8% of the United States population. Hispanic and Latino Americans form the second-largest group and are 18.7% of the United States population. African Americans constitute the country's third-largest ancestry group and are 12.1% of the total U.S. population. Asian Americans are the country's fourth-largest group, composing 5.9% of the United States population. The country's 3.7 million Native Americans account for about 1%, and some 574 native tribes are recognized by the federal government. In 2024, the median age of the United States population was 39.1 years. While many languages and dialects are spoken in the United States, English is by far the most commonly spoken and written. De facto, English is the official language of the United States, and in 2025, Executive Order 14224 declared English official. However, the U.S. has never had a de jure official language, as Congress has never passed a law to designate English as official for all three federal branches. Some laws, such as U.S. naturalization requirements, nonetheless standardize English. Twenty-eight states and the United States Virgin Islands have laws that designate English as the sole official language; 19 states and the District of Columbia have no official language. Three states and four U.S. territories have recognized local or indigenous languages in addition to English: Hawaii (Hawaiian), Alaska (twenty Native languages),[w] South Dakota (Sioux), American Samoa (Samoan), Puerto Rico (Spanish), Guam (Chamorro), and the Northern Mariana Islands (Carolinian and Chamorro). In total, 169 Native American languages are spoken in the United States. In Puerto Rico, Spanish is more widely spoken than English. According to the American Community Survey (2020), some 245.4 million people in the U.S. age five and older spoke only English at home. About 41.2 million spoke Spanish at home, making it the second most commonly used language. Other languages spoken at home by one million people or more include Chinese (3.40 million), Tagalog (1.71 million), Vietnamese (1.52 million), Arabic (1.39 million), French (1.18 million), Korean (1.07 million), and Russian (1.04 million). German, spoken by 1 million people at home in 2010, fell to 857,000 total speakers in 2020. America's immigrant population is by far the world's largest in absolute terms. In 2022, there were 87.7 million immigrants and U.S.-born children of immigrants in the United States, accounting for nearly 27% of the overall U.S. population. In 2017, out of the U.S. foreign-born population, some 45% (20.7 million) were naturalized citizens, 27% (12.3 million) were lawful permanent residents, 6% (2.2 million) were temporary lawful residents, and 23% (10.5 million) were unauthorized immigrants. In 2019, the top countries of origin for immigrants were Mexico (24% of immigrants), India (6%), China (5%), the Philippines (4.5%), and El Salvador (3%). In fiscal year 2022, over one million immigrants (most of whom entered through family reunification) were granted legal residence. The undocumented immigrant population in the U.S. reached a record high of 14 million in 2023. The First Amendment guarantees the free exercise of religion in the country and forbids Congress from passing laws respecting its establishment. Religious practice is widespread, among the most diverse in the world, and profoundly vibrant. The country has the world's largest Christian population, which includes the fourth-largest population of Catholics. Other notable faiths include Judaism, Buddhism, Hinduism, Islam, New Age, and Native American religions. Religious practice varies significantly by region. "Ceremonial deism" is common in American culture. The overwhelming majority of Americans believe in a higher power or spiritual force, engage in spiritual practices such as prayer, and consider themselves religious or spiritual. In the Southern United States' "Bible Belt", evangelical Protestantism plays a significant role culturally; New England and the Western United States tend to be more secular. Mormonism, a Restorationist movement founded in the U.S. in 1847, is the predominant religion in Utah and a major religion in Idaho. About 82% of Americans live in metropolitan areas, particularly in suburbs; about half of those reside in cities with populations over 50,000. In 2022, 333 incorporated municipalities had populations over 100,000, nine cities had more than one million residents, and four cities—New York City, Los Angeles, Chicago, and Houston—had populations exceeding two million. Many U.S. metropolitan populations are growing rapidly, particularly in the South and West. According to the Centers for Disease Control and Prevention (CDC), average U.S. life expectancy at birth reached 79.0 years in 2024, its highest recorded level. This was an increase of 0.6 years over 2023. The CDC attributed the improvement to a significant fall in the number of fatal drug overdoses in the country, noting that "heart disease continues to be the leading cause of death in the United States, followed by cancer and unintentional injuries." In 2024, life expectancy at birth for American men rose to 76.5 years (+0.7 years compared to 2023), while life expectancy for women was 81.4 years (+0.3 years). Starting in 1998, life expectancy in the U.S. fell behind that of other wealthy industrialized countries, and Americans' "health disadvantage" gap has been increasing ever since. The Commonwealth Fund reported in 2020 that the U.S. had the highest suicide rate among high-income countries. Approximately one-third of the U.S. adult population is obese and another third is overweight. The U.S. healthcare system far outspends that of any other country, measured both in per capita spending and as a percentage of GDP, but attains worse healthcare outcomes when compared to peer countries for reasons that are debated. The United States is the only developed country without a system of universal healthcare, and a significant proportion of the population that does not carry health insurance. Government-funded healthcare coverage for the poor (Medicaid) and for those age 65 and older (Medicare) is available to Americans who meet the programs' income or age qualifications. In 2010, then-President Obama passed the Patient Protection and Affordable Care Act.[x] Abortion in the United States is not federally protected, and is illegal or restricted in 17 states. American primary and secondary education, known in the U.S. as K–12 ("kindergarten through 12th grade"), is decentralized. School systems are operated by state, territorial, and sometimes municipal governments and regulated by the U.S. Department of Education. In general, children are required to attend school or an approved homeschool from the age of five or six (kindergarten or first grade) until they are 18 years old. This often brings students through the 12th grade, the final year of a U.S. high school, but some states and territories allow them to leave school earlier, at age 16 or 17. The U.S. spends more on education per student than any other country, an average of $18,614 per year per public elementary and secondary school student in 2020–2021. Among Americans age 25 and older, 92.2% graduated from high school, 62.7% attended some college, 37.7% earned a bachelor's degree, and 14.2% earned a graduate degree. The U.S. literacy rate is near-universal. The U.S. has produced the most Nobel Prize winners of any country, with 411 (having won 413 awards). U.S. tertiary or higher education has earned a global reputation. Many of the world's top universities, as listed by various ranking organizations, are in the United States, including 19 of the top 25. American higher education is dominated by state university systems, although the country's many private universities and colleges enroll about 20% of all American students. Local community colleges generally offer open admissions, lower tuition, and coursework leading to a two-year associate degree or a non-degree certificate. As for public expenditures on higher education, the U.S. spends more per student than the OECD average, and Americans spend more than all nations in combined public and private spending. Colleges and universities directly funded by the federal government do not charge tuition and are limited to military personnel and government employees, including: the U.S. service academies, the Naval Postgraduate School, and military staff colleges. Despite some student loan forgiveness programs in place, student loan debt increased by 102% between 2010 and 2020, and exceeded $1.7 trillion in 2022. Culture and society The United States is home to a wide variety of ethnic groups, traditions, and customs. The country has been described as having the values of individualism and personal autonomy, as well as a strong work ethic and competitiveness. Voluntary altruism towards others also plays a major role; according to a 2016 study by the Charities Aid Foundation, Americans donated 1.44% of total GDP to charity—the highest rate in the world by a large margin. Americans have traditionally been characterized by a unifying political belief in an "American Creed" emphasizing consent of the governed, liberty, equality under the law, democracy, social equality, property rights, and a preference for limited government. The U.S. has acquired significant hard and soft power through its diplomatic influence, economic power, military alliances, and cultural exports such as American movies, music, video games, sports, and food. The influence that the United States exerts on other countries through soft power is referred to as Americanization. Nearly all present Americans or their ancestors came from Europe, Africa, or Asia (the "Old World") within the past five centuries. Mainstream American culture is a Western culture largely derived from the traditions of European immigrants with influences from many other sources, such as traditions brought by slaves from Africa. More recent immigration from Asia and especially Latin America has added to a cultural mix that has been described as a homogenizing melting pot, and a heterogeneous salad bowl, with immigrants contributing to, and often assimilating into, mainstream American culture. Under the First Amendment to the Constitution, the United States is considered to have the strongest protections of free speech of any country. Flag desecration, hate speech, blasphemy, and lese majesty are all forms of protected expression. A 2016 Pew Research Center poll found that Americans were the most supportive of free expression of any polity measured. Additionally, they are the "most supportive of freedom of the press and the right to use the Internet without government censorship". The U.S. is a socially progressive country with permissive attitudes surrounding human sexuality. LGBTQ rights in the United States are among the most advanced by global standards. The American Dream, or the perception that Americans enjoy high levels of social mobility, plays a key role in attracting immigrants. Whether this perception is accurate has been a topic of debate. While mainstream culture holds that the United States is a classless society, scholars identify significant differences between the country's social classes, affecting socialization, language, and values. Americans tend to greatly value socioeconomic achievement, but being ordinary or average is promoted by some as a noble condition as well. The National Foundation on the Arts and the Humanities is an agency of the United States federal government that was established in 1965 with the purpose to "develop and promote a broadly conceived national policy of support for the humanities and the arts in the United States, and for institutions which preserve the cultural heritage of the United States." It is composed of four sub-agencies: Colonial American authors were influenced by John Locke and other Enlightenment philosophers. The American Revolutionary Period (1765–1783) is notable for the political writings of Benjamin Franklin, Alexander Hamilton, Thomas Paine, and Thomas Jefferson. Shortly before and after the Revolutionary War, the newspaper rose to prominence, filling a demand for anti-British national literature. An early novel is William Hill Brown's The Power of Sympathy, published in 1791. Writer and critic John Neal in the early- to mid-19th century helped advance America toward a unique literature and culture by criticizing predecessors such as Washington Irving for imitating their British counterparts, and by influencing writers such as Edgar Allan Poe, who took American poetry and short fiction in new directions. Ralph Waldo Emerson and Margaret Fuller pioneered the influential Transcendentalism movement; Henry David Thoreau, author of Walden, was influenced by this movement. The conflict surrounding abolitionism inspired writers, like Harriet Beecher Stowe, and authors of slave narratives, such as Frederick Douglass. Nathaniel Hawthorne's The Scarlet Letter (1850) explored the dark side of American history, as did Herman Melville's Moby-Dick (1851). Major American poets of the 19th century American Renaissance include Walt Whitman, Melville, and Emily Dickinson. Mark Twain was the first major American writer to be born in the West. Henry James achieved international recognition with novels like The Portrait of a Lady (1881). As literacy rates rose, periodicals published more stories centered around industrial workers, women, and the rural poor. Naturalism, regionalism, and realism were the major literary movements of the period. While modernism generally took on an international character, modernist authors working within the United States more often rooted their work in specific regions, peoples, and cultures. Following the Great Migration to northern cities, African-American and black West Indian authors of the Harlem Renaissance developed an independent tradition of literature that rebuked a history of inequality and celebrated black culture. An important cultural export during the Jazz Age, these writings were a key influence on Négritude, a philosophy emerging in the 1930s among francophone writers of the African diaspora. In the 1950s, an ideal of homogeneity led many authors to attempt to write the Great American Novel, while the Beat Generation rejected this conformity, using styles that elevated the impact of the spoken word over mechanics to describe drug use, sexuality, and the failings of society. Contemporary literature is more pluralistic than in previous eras, with the closest thing to a unifying feature being a trend toward self-conscious experiments with language. Twelve American laureates have won the Nobel Prize in Literature. Media in the United States is broadly uncensored, with the First Amendment providing significant protections, as reiterated in New York Times Co. v. United States. The four major broadcasters in the U.S. are the National Broadcasting Company (NBC), Columbia Broadcasting System (CBS), American Broadcasting Company (ABC), and Fox Broadcasting Company (Fox). The four major broadcast television networks are all commercial entities. The U.S. cable television system offers hundreds of channels catering to a variety of niches. In 2021, about 83% of Americans over age 12 listened to broadcast radio, while about 40% listened to podcasts. In the prior year, there were 15,460 licensed full-power radio stations in the U.S. according to the Federal Communications Commission (FCC). Much of the public radio broadcasting is supplied by National Public Radio (NPR), incorporated in February 1970 under the Public Broadcasting Act of 1967. U.S. newspapers with a global reach and reputation include The Wall Street Journal, The New York Times, The Washington Post, and USA Today. About 800 publications are produced in Spanish. With few exceptions, newspapers are privately owned, either by large chains such as Gannett or McClatchy, which own dozens or even hundreds of newspapers; by small chains that own a handful of papers; or, in an increasingly rare situation, by individuals or families. Major cities often have alternative newspapers to complement the mainstream daily papers, such as The Village Voice in New York City and LA Weekly in Los Angeles. The five most-visited websites in the world are Google, YouTube, Facebook, Instagram, and ChatGPT—all of them American-owned. Other popular platforms used include X (formerly Twitter) and Amazon. In 2025, the U.S. was the world's second-largest video game market by revenue (after China). In 2015, the U.S. video game industry consisted of 2,457 companies that employed around 220,000 jobs and generated $30.4 billion in revenue. There are 444 game publishers, developers, and hardware companies in California alone. According to the Game Developers Conference (GDC), the U.S. is the top location for video game development, with 58% of the world's game developers based there in 2025. The United States is well known for its theater. Mainstream theater in the United States derives from the old European theatrical tradition and has been heavily influenced by the British theater. By the middle of the 19th century, America had created new distinct dramatic forms in the Tom Shows, the showboat theater and the minstrel show. The central hub of the American theater scene is the Theater District in Manhattan, with its divisions of Broadway, off-Broadway, and off-off-Broadway. Many movie and television celebrities have gotten their big break working in New York productions. Outside New York City, many cities have professional regional or resident theater companies that produce their own seasons. The biggest-budget theatrical productions are musicals. U.S. theater has an active community theater culture. The Tony Awards recognizes excellence in live Broadway theater and are presented at an annual ceremony in Manhattan. The awards are given for Broadway productions and performances. One is also given for regional theater. Several discretionary non-competitive awards are given as well, including a Special Tony Award, the Tony Honors for Excellence in Theatre, and the Isabelle Stevenson Award. Folk art in colonial America grew out of artisanal craftsmanship in communities that allowed commonly trained people to individually express themselves. It was distinct from Europe's tradition of high art, which was less accessible and generally less relevant to early American settlers. Cultural movements in art and craftsmanship in colonial America generally lagged behind those of Western Europe. For example, the prevailing medieval style of woodworking and primitive sculpture became integral to early American folk art, despite the emergence of Renaissance styles in England in the late 16th and early 17th centuries. The new English styles would have been early enough to make a considerable impact on American folk art, but American styles and forms had already been firmly adopted. Not only did styles change slowly in early America, but there was a tendency for rural artisans there to continue their traditional forms longer than their urban counterparts did—and far longer than those in Western Europe. The Hudson River School was a mid-19th-century movement in the visual arts tradition of European naturalism. The 1913 Armory Show in New York City, an exhibition of European modernist art, shocked the public and transformed the U.S. art scene. American Realism and American Regionalism sought to reflect and give America new ways of looking at itself. Georgia O'Keeffe, Marsden Hartley, and others experimented with new and individualistic styles, which would become known as American modernism. Major artistic movements such as the abstract expressionism of Jackson Pollock and Willem de Kooning and the pop art of Andy Warhol and Roy Lichtenstein developed largely in the United States. Major photographers include Alfred Stieglitz, Edward Steichen, Dorothea Lange, Edward Weston, James Van Der Zee, Ansel Adams, and Gordon Parks. The tide of modernism and then postmodernism has brought global fame to American architects, including Frank Lloyd Wright, Philip Johnson, and Frank Gehry. The Metropolitan Museum of Art in Manhattan is the largest art museum in the United States and the fourth-largest in the world. American folk music encompasses numerous music genres, variously known as traditional music, traditional folk music, contemporary folk music, or roots music. Many traditional songs have been sung within the same family or folk group for generations, and sometimes trace back to such origins as the British Isles, mainland Europe, or Africa. The rhythmic and lyrical styles of African-American music in particular have influenced American music. Banjos were brought to America through the slave trade. Minstrel shows incorporating the instrument into their acts led to its increased popularity and widespread production in the 19th century. The electric guitar, first invented in the 1930s, and mass-produced by the 1940s, had an enormous influence on popular music, in particular due to the development of rock and roll. The synthesizer, turntablism, and electronic music were also largely developed in the U.S. Elements from folk idioms such as the blues and old-time music were adopted and transformed into popular genres with global audiences. Jazz grew from blues and ragtime in the early 20th century, developing from the innovations and recordings of composers such as W.C. Handy and Jelly Roll Morton. Louis Armstrong and Duke Ellington increased its popularity early in the 20th century. Country music developed in the 1920s, bluegrass and rhythm and blues in the 1940s, and rock and roll in the 1950s. In the 1960s, Bob Dylan emerged from the folk revival to become one of the country's most celebrated songwriters. The musical forms of punk and hip hop both originated in the United States in the 1970s. The United States has the world's largest music market, with a total retail value of $15.9 billion in 2022. Most of the world's major record companies are based in the U.S.; they are represented by the Recording Industry Association of America (RIAA). Mid-20th-century American pop stars, such as Frank Sinatra and Elvis Presley, became global celebrities and best-selling music artists, as have artists of the late 20th century, such as Michael Jackson, Madonna, Whitney Houston, and Mariah Carey, and of the early 21st century, such as Eminem, Britney Spears, Lady Gaga, Katy Perry, Taylor Swift and Beyoncé. The United States has the world's largest apparel market by revenue. Apart from professional business attire, American fashion is eclectic and predominantly informal. Americans' diverse cultural roots are reflected in their clothing; however, sneakers, jeans, T-shirts, and baseball caps are emblematic of American styles. New York, with its Fashion Week, is considered to be one of the "Big Four" global fashion capitals, along with Paris, Milan, and London. A study demonstrated that general proximity to Manhattan's Garment District has been synonymous with American fashion since its inception in the early 20th century. A number of well-known designer labels, among them Tommy Hilfiger, Ralph Lauren, Tom Ford and Calvin Klein, are headquartered in Manhattan. Labels cater to niche markets, such as preteens. New York Fashion Week is one of the most influential fashion shows in the world, and is held twice each year in Manhattan; the annual Met Gala, also in Manhattan, has been called the fashion world's "biggest night". The U.S. film industry has a worldwide influence and following. Hollywood, a district in central Los Angeles, the nation's second-most populous city, is also metonymous for the American filmmaking industry. The major film studios of the United States are the primary source of the most commercially successful movies selling the most tickets in the world. Largely centered in the New York City region from its beginnings in the late 19th century through the first decades of the 20th century, the U.S. film industry has since been primarily based in and around Hollywood. Nonetheless, American film companies have been subject to the forces of globalization in the 21st century, and an increasing number of films are made elsewhere. The Academy Awards, popularly known as "the Oscars", have been held annually by the Academy of Motion Picture Arts and Sciences since 1929, and the Golden Globe Awards have been held annually since January 1944. The industry peaked in what is commonly referred to as the "Golden Age of Hollywood", from the early sound period until the early 1960s, with screen actors such as John Wayne and Marilyn Monroe becoming iconic figures. In the 1970s, "New Hollywood", or the "Hollywood Renaissance", was defined by grittier films influenced by French and Italian realist pictures of the post-war period. The 21st century has been marked by the rise of American streaming platforms, which came to rival traditional cinema. Early settlers were introduced by Native Americans to foods such as turkey, sweet potatoes, corn, squash, and maple syrup. Of the most enduring and pervasive examples are variations of the native dish called succotash. Early settlers and later immigrants combined these with foods they were familiar with, such as wheat flour, beef, and milk, to create a distinctive American cuisine. New World crops, especially pumpkin, corn, potatoes, and turkey as the main course are part of a shared national menu on Thanksgiving, when many Americans prepare or purchase traditional dishes to celebrate the occasion. Characteristic American dishes such as apple pie, fried chicken, doughnuts, french fries, macaroni and cheese, ice cream, hamburgers, hot dogs, and American pizza derive from the recipes of various immigrant groups. Mexican dishes such as burritos and tacos preexisted the United States in areas later annexed from Mexico, and adaptations of Chinese cuisine as well as pasta dishes freely adapted from Italian sources are all widely consumed. American chefs have had a significant impact on society both domestically and internationally. In 1946, the Culinary Institute of America was founded by Katharine Angell and Frances Roth. This would become the United States' most prestigious culinary school, where many of the most talented American chefs would study prior to successful careers. The United States restaurant industry was projected at $899 billion in sales for 2020, and employed more than 15 million people, representing 10% of the nation's workforce directly. It is the country's second-largest private employer and the third-largest employer overall. The United States is home to over 220 Michelin star-rated restaurants, 70 of which are in New York City. Wine has been produced in what is now the United States since the 1500s, with the first widespread production beginning in what is now New Mexico in 1628. In the modern U.S., wine production is undertaken in all fifty states, with California producing 84 percent of all U.S. wine. With more than 1,100,000 acres (4,500 km2) under vine, the United States is the fourth-largest wine-producing country in the world, after Italy, Spain, and France. The classic American diner, a casual restaurant type originally intended for the working class, emerged during the 19th century from converted railroad dining cars made stationary. The diner soon evolved into purpose-built structures whose number expanded greatly in the 20th century. The American fast-food industry developed alongside the nation's car culture. American restaurants developed the drive-in format in the 1920s, which they began to replace with the drive-through format by the 1940s. American fast-food restaurant chains, such as McDonald's, Burger King, Chick-fil-A, Kentucky Fried Chicken, Dunkin' Donuts and many others, have numerous outlets around the world. The most popular spectator sports in the U.S. are American football, basketball, baseball, soccer, and ice hockey. Their premier leagues are, respectively, the National Football League, the National Basketball Association, Major League Baseball, Major League Soccer, and the National Hockey League, All these leagues enjoy wide-ranging domestic media coverage and, except for the MLS, all are considered the preeminent leagues in their respective sports in the world. While most major U.S. sports such as baseball and American football have evolved out of European practices, basketball, volleyball, skateboarding, and snowboarding are American inventions, many of which have become popular worldwide. Lacrosse and surfing arose from Native American and Native Hawaiian activities that predate European contact. The market for professional sports in the United States was approximately $69 billion in July 2013, roughly 50% larger than that of Europe, the Middle East, and Africa combined. American football is by several measures the most popular spectator sport in the United States. Although American football does not have a substantial following in other nations, the NFL does have the highest average attendance (67,254) of any professional sports league in the world. In the year 2024, the NFL generated over $23 billion, making them the most valued professional sports league in the United States and the world. Baseball has been regarded as the U.S. "national sport" since the late 19th century. The most-watched individual sports in the U.S. are golf and auto racing, particularly NASCAR and IndyCar. On the collegiate level, earnings for the member institutions exceed $1 billion annually, and college football and basketball attract large audiences, as the NCAA March Madness tournament and the College Football Playoff are some of the most watched national sporting events. In the U.S., the intercollegiate sports level serves as the main feeder system for professional and Olympic sports, with significant exceptions such as Minor League Baseball. This differs greatly from practices in nearly all other countries, where publicly and privately funded sports organizations serve this function. Eight Olympic Games have taken place in the United States. The 1904 Summer Olympics in St. Louis, Missouri, were the first-ever Olympic Games held outside of Europe. The Olympic Games will be held in the U.S. for a ninth time when Los Angeles hosts the 2028 Summer Olympics. U.S. athletes have won a total of 2,968 medals (1,179 gold) at the Olympic Games, the most of any country. In other international competition, the United States is the home of a number of prestigious events, including the America's Cup, World Baseball Classic, the U.S. Open, and the Masters Tournament. The U.S. men's national soccer team has qualified for eleven World Cups, while the women's national team has won the FIFA Women's World Cup and Olympic soccer tournament four and five times, respectively. The 1999 FIFA Women's World Cup was hosted by the United States. Its final match was attended by 90,185, setting the world record for largest women's sporting event crowd at the time. The United States hosted the 1994 FIFA World Cup and will co-host, along with Canada and Mexico, the 2026 FIFA World Cup. See also Notes References This article incorporates text from a free content work. Licensed under CC BY-SA IGO 3.0 (license statement/permission). Text taken from World Food and Agriculture – Statistical Yearbook 2023, FAO, FAO. External links 40°N 100°W / 40°N 100°W / 40; -100 (United States of America) |
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Contents OpenAI OpenAI is an American artificial intelligence research organization comprising both a non-profit foundation and a controlled for-profit public benefit corporation (PBC), headquartered in San Francisco. It aims to develop "safe and beneficial" artificial general intelligence (AGI), which it defines as "highly autonomous systems that outperform humans at most economically valuable work". OpenAI is widely recognized for its development of the GPT family of large language models, the DALL-E series of text-to-image models, and the Sora series of text-to-video models, which have influenced industry research and commercial applications. Its release of ChatGPT in November 2022 has been credited with catalyzing widespread interest in generative AI. The organization was founded in 2015 in Delaware but evolved a complex corporate structure. As of October 2025, following restructuring approved by California and Delaware regulators, the non-profit OpenAI Foundation holds 26% of the for-profit OpenAI Group PBC, with Microsoft holding 27% and employees/other investors holding 47%. Under its governance arrangements, the OpenAI Foundation holds the authority to appoint the board of the for-profit OpenAI Group PBC, a mechanism designed to align the entity’s strategic direction with the Foundation’s charter. Microsoft previously invested over $13 billion into OpenAI, and provides Azure cloud computing resources. In October 2025, OpenAI conducted a $6.6 billion share sale that valued the company at $500 billion. In 2023 and 2024, OpenAI faced multiple lawsuits for alleged copyright infringement against authors and media companies whose work was used to train some of OpenAI's products. In November 2023, OpenAI's board removed Sam Altman as CEO, citing a lack of confidence in him, but reinstated him five days later following a reconstruction of the board. Throughout 2024, roughly half of then-employed AI safety researchers left OpenAI, citing the company's prominent role in an industry-wide problem. Founding In December 2015, OpenAI was founded as a not for profit organization by Sam Altman, Elon Musk, Ilya Sutskever, Greg Brockman, Trevor Blackwell, Vicki Cheung, Andrej Karpathy, Durk Kingma, John Schulman, Pamela Vagata, and Wojciech Zaremba, with Sam Altman and Elon Musk as the co-chairs. A total of $1 billion in capital was pledged by Sam Altman, Greg Brockman, Elon Musk, Reid Hoffman, Jessica Livingston, Peter Thiel, Amazon Web Services (AWS), and Infosys. However, the actual capital collected significantly lagged pledges. According to company disclosures, only $130 million had been received by 2019. In its founding charter, OpenAI stated an intention to collaborate openly with other institutions by making certain patents and research publicly available, but later restricted access to its most capable models, citing competitive and safety concerns. OpenAI was initially run from Brockman's living room. It was later headquartered at the Pioneer Building in the Mission District, San Francisco. According to OpenAI's charter, its founding mission is "to ensure that artificial general intelligence (AGI)—by which we mean highly autonomous systems that outperform humans at most economically valuable work—benefits all of humanity." Musk and Altman stated in 2015 that they were partly motivated by concerns about AI safety and existential risk from artificial general intelligence. OpenAI stated that "it's hard to fathom how much human-level AI could benefit society", and that it is equally difficult to comprehend "how much it could damage society if built or used incorrectly". The startup also wrote that AI "should be an extension of individual human wills and, in the spirit of liberty, as broadly and evenly distributed as possible", and that "because of AI's surprising history, it's hard to predict when human-level AI might come within reach. When it does, it'll be important to have a leading research institution which can prioritize a good outcome for all over its own self-interest." Co-chair Sam Altman expected a decades-long project that eventually surpasses human intelligence. Brockman met with Yoshua Bengio, one of the "founding fathers" of deep learning, and drew up a list of great AI researchers. Brockman was able to hire nine of them as the first employees in December 2015. OpenAI did not pay AI researchers salaries comparable to those of Facebook or Google. It also did not pay stock options which AI researchers typically get. Nevertheless, OpenAI spent $7 million on its first 52 employees in 2016. OpenAI's potential and mission drew these researchers to the firm; a Google employee said he was willing to leave Google for OpenAI "partly because of the very strong group of people and, to a very large extent, because of its mission." OpenAI co-founder Wojciech Zaremba stated that he turned down "borderline crazy" offers of two to three times his market value to join OpenAI instead. In April 2016, OpenAI released a public beta of "OpenAI Gym", its platform for reinforcement learning research. Nvidia gifted its first DGX-1 supercomputer to OpenAI in August 2016 to help it train larger and more complex AI models with the capability of reducing processing time from six days to two hours. In December 2016, OpenAI released "Universe", a software platform for measuring and training an AI's general intelligence across the world's supply of games, websites, and other applications. Corporate structure In 2019, OpenAI transitioned from non-profit to "capped" for-profit, with the profit being capped at 100 times any investment. According to OpenAI, the capped-profit model allows OpenAI Global, LLC to legally attract investment from venture funds and, in addition, to grant employees stakes in the company. Many top researchers work for Google Brain, DeepMind, or Facebook, which offer equity that a nonprofit would be unable to match. Before the transition, OpenAI was legally required to publicly disclose the compensation of its top employees. The company then distributed equity to its employees and partnered with Microsoft, announcing an investment package of $1 billion into the company. Since then, OpenAI systems have run on an Azure-based supercomputing platform from Microsoft. OpenAI Global, LLC then announced its intention to commercially license its technologies. It planned to spend $1 billion "within five years, and possibly much faster". Altman stated that even a billion dollars may turn out to be insufficient, and that the lab may ultimately need "more capital than any non-profit has ever raised" to achieve artificial general intelligence. The nonprofit, OpenAI, Inc., is the sole controlling shareholder of OpenAI Global, LLC, which, despite being a for-profit company, retains a formal fiduciary responsibility to OpenAI, Inc.'s nonprofit charter. A majority of OpenAI, Inc.'s board is barred from having financial stakes in OpenAI Global, LLC. In addition, minority members with a stake in OpenAI Global, LLC are barred from certain votes due to conflict of interest. Some researchers have argued that OpenAI Global, LLC's switch to for-profit status is inconsistent with OpenAI's claims to be "democratizing" AI. On February 29, 2024, Elon Musk filed a lawsuit against OpenAI and CEO Sam Altman, accusing them of shifting focus from public benefit to profit maximization—a case OpenAI dismissed as "incoherent" and "frivolous," though Musk later revived legal action against Altman and others in August. On April 9, 2024, OpenAI countersued Musk in federal court, alleging that he had engaged in "bad-faith tactics" to slow the company's progress and seize its innovations for his personal benefit. OpenAI also argued that Musk had previously supported the creation of a for-profit structure and had expressed interest in controlling OpenAI himself. The countersuit seeks damages and legal measures to prevent further alleged interference. On February 10, 2025, a consortium of investors led by Elon Musk submitted a $97.4 billion unsolicited bid to buy the nonprofit that controls OpenAI, declaring willingness to match or exceed any better offer. The offer was rejected on 14 February 2025, with OpenAI stating that it was not for sale, but the offer complicated Altman's restructuring plan by suggesting a lower bar for how much the nonprofit should be valued. OpenAI, Inc. was originally designed as a nonprofit in order to ensure that AGI "benefits all of humanity" rather than "the private gain of any person". In 2019, it created OpenAI Global, LLC, a capped-profit subsidiary controlled by the nonprofit. In December 2024, OpenAI proposed a restructuring plan to convert the capped-profit into a Delaware-based public benefit corporation (PBC), and to release it from the control of the nonprofit. The nonprofit would sell its control and other assets, getting equity in return, and would use it to fund and pursue separate charitable projects, including in science and education. OpenAI's leadership described the change as necessary to secure additional investments, and claimed that the nonprofit's founding mission to ensure AGI "benefits all of humanity" would be better fulfilled. The plan has been criticized by former employees. A legal letter named "Not For Private Gain" asked the attorneys general of California and Delaware to intervene, stating that the restructuring is illegal and would remove governance safeguards from the nonprofit and the attorneys general. The letter argues that OpenAI's complex structure was deliberately designed to remain accountable to its mission, without the conflicting pressure of maximizing profits. It contends that the nonprofit is best positioned to advance its mission of ensuring AGI benefits all of humanity by continuing to control OpenAI Global, LLC, whatever the amount of equity that it could get in exchange. PBCs can choose how they balance their mission with profit-making. Controlling shareholders have a large influence on how closely a PBC sticks to its mission. On October 28, 2025, OpenAI announced that it had adopted the new PBC corporate structure after receiving approval from the attorneys general of California and Delaware. Under the new structure, OpenAI's for-profit branch became a public benefit corporation known as OpenAI Group PBC, while the non-profit was renamed to the OpenAI Foundation. The OpenAI Foundation holds a 26% stake in the PBC, while Microsoft holds a 27% stake and the remaining 47% is owned by employees and other investors. All members of the OpenAI Group PBC board of directors will be appointed by the OpenAI Foundation, which can remove them at any time. Members of the Foundation's board will also serve on the for-profit board. The new structure allows the for-profit PBC to raise investor funds like most traditional tech companies, including through an initial public offering, which Altman claimed was the most likely path forward. In January 2023, OpenAI Global, LLC was in talks for funding that would value the company at $29 billion, double its 2021 value. On January 23, 2023, Microsoft announced a new US$10 billion investment in OpenAI Global, LLC over multiple years, partially needed to use Microsoft's cloud-computing service Azure. From September to December, 2023, Microsoft rebranded all variants of its Copilot to Microsoft Copilot, and they added MS-Copilot to many installations of Windows and released Microsoft Copilot mobile apps. Following OpenAI's 2025 restructuring, Microsoft owns a 27% stake in the for-profit OpenAI Group PBC, valued at $135 billion. In a deal announced the same day, OpenAI agreed to purchase $250 billion of Azure services, with Microsoft ceding their right of first refusal over OpenAI's future cloud computing purchases. As part of the deal, OpenAI will continue to share 20% of its revenue with Microsoft until it achieves AGI, which must now be verified by an independent panel of experts. The deal also loosened restrictions on both companies working with third parties, allowing Microsoft to pursue AGI independently and allowing OpenAI to develop products with other companies. In 2017, OpenAI spent $7.9 million, a quarter of its functional expenses, on cloud computing alone. In comparison, DeepMind's total expenses in 2017 were $442 million. In the summer of 2018, training OpenAI's Dota 2 bots required renting 128,000 CPUs and 256 GPUs from Google for multiple weeks. In October 2024, OpenAI completed a $6.6 billion capital raise with a $157 billion valuation including investments from Microsoft, Nvidia, and SoftBank. On January 21, 2025, Donald Trump announced The Stargate Project, a joint venture between OpenAI, Oracle, SoftBank and MGX to build an AI infrastructure system in conjunction with the US government. The project takes its name from OpenAI's existing "Stargate" supercomputer project and is estimated to cost $500 billion. The partners planned to fund the project over the next four years. In July, the United States Department of Defense announced that OpenAI had received a $200 million contract for AI in the military, along with Anthropic, Google, and xAI. In the same month, the company made a deal with the UK Government to use ChatGPT and other AI tools in public services. OpenAI subsequently began a $50 million fund to support nonprofit and community organizations. In April 2025, OpenAI raised $40 billion at a $300 billion post-money valuation, which was the highest-value private technology deal in history. The financing round was led by SoftBank, with other participants including Microsoft, Coatue, Altimeter and Thrive. In July 2025, the company reported annualized revenue of $12 billion. This was an increase from $3.7 billion in 2024, which was driven by ChatGPT subscriptions, which reached 20 million paid subscribers by April 2025, up from 15.5 million at the end of 2024, alongside a rapidly expanding enterprise customer base that grew to five million business users. The company’s cash burn remains high because of the intensive computational costs required to train and operate large language models. It projects an $8 billion operating loss in 2025. OpenAI reports revised long-term spending projections totaling approximately $115 billion through 2029, with annual expenditures projected to escalate significantly, reaching $17 billion in 2026, $35 billion in 2027, and $45 billion in 2028. These expenditures are primarily allocated toward expanding compute infrastructure, developing proprietary AI chips, constructing data centers, and funding intensive model training programs, with more than half of the spending through the end of the decade expected to support research-intensive compute for model training and development. The company's financial strategy prioritizes market expansion and technological advancement over near-term profitability, with OpenAI targeting cash-flow-positive operations by 2029 and projecting revenue of approximately $200 billion by 2030. This aggressive spending trajectory underscores both the enormous capital requirements of scaling cutting-edge AI technology and OpenAI's commitment to maintaining its position as a leader in the artificial intelligence industry. In October 2025, OpenAI completed an employee share sale of up to $10 billion to existing investors which valued the company at $500 billion. The deal values OpenAI as the most valuable privately owned company in the world—surpassing SpaceX as the world's most valuable private company. On November 17, 2023, Sam Altman was removed as CEO when its board of directors (composed of Helen Toner, Ilya Sutskever, Adam D'Angelo and Tasha McCauley) cited a lack of confidence in him. Chief Technology Officer Mira Murati took over as interim CEO. Greg Brockman, the president of OpenAI, was also removed as chairman of the board and resigned from the company's presidency shortly thereafter. Three senior OpenAI researchers subsequently resigned: director of research and GPT-4 lead Jakub Pachocki, head of AI risk Aleksander Mądry, and researcher Szymon Sidor. On November 18, 2023, there were reportedly talks of Altman returning as CEO amid pressure placed upon the board by investors such as Microsoft and Thrive Capital, who objected to Altman's departure. Although Altman himself spoke in favor of returning to OpenAI, he has since stated that he considered starting a new company and bringing former OpenAI employees with him if talks to reinstate him didn't work out. The board members agreed "in principle" to resign if Altman returned. On November 19, 2023, negotiations with Altman to return failed and Murati was replaced by Emmett Shear as interim CEO. The board initially contacted Anthropic CEO Dario Amodei (a former OpenAI executive) about replacing Altman, and proposed a merger of the two companies, but both offers were declined. On November 20, 2023, Microsoft CEO Satya Nadella announced Altman and Brockman would be joining Microsoft to lead a new advanced AI research team, but added that they were still committed to OpenAI despite recent events. Before the partnership with Microsoft was finalized, Altman gave the board another opportunity to negotiate with him. About 738 of OpenAI's 770 employees, including Murati and Sutskever, signed an open letter stating they would quit their jobs and join Microsoft if the board did not rehire Altman and then resign. This prompted OpenAI investors to consider legal action against the board as well. In response, OpenAI management sent an internal memo to employees stating that negotiations with Altman and the board had resumed and would take some time. On November 21, 2023, after continued negotiations, Altman and Brockman returned to the company in their prior roles along with a reconstructed board made up of new members Bret Taylor (as chairman) and Lawrence Summers, with D'Angelo remaining. According to subsequent reporting, shortly before Altman’s firing, some employees raised concerns to the board about how he had handled the safety implications of a recent internal AI capability discovery. On November 29, 2023, OpenAI announced that an anonymous Microsoft employee had joined the board as a non-voting member to observe the company's operations; Microsoft resigned from the board in July 2024. In February 2024, the Securities and Exchange Commission subpoenaed OpenAI's internal communication to determine if Altman's alleged lack of candor misled investors. In 2024, following the temporary removal of Sam Altman and his return, many employees gradually left OpenAI, including most of the original leadership team and a significant number of AI safety researchers. In August 2023, it was announced that OpenAI had acquired the New York-based start-up Global Illumination, a company that deploys AI to develop digital infrastructure and creative tools. In June 2024, OpenAI acquired Multi, a startup focused on remote collaboration. In March 2025, OpenAI reached a deal with CoreWeave to acquire $350 million worth of CoreWeave shares and access to AI infrastructure, in return for $11.9 billion paid over five years. Microsoft was already CoreWeave's biggest customer in 2024. Alongside their other business dealings, OpenAI and Microsoft were renegotiating the terms of their partnership to facilitate a potential future initial public offering by OpenAI, while ensuring Microsoft's continued access to advanced AI models. On May 21, OpenAI announced the $6.5 billion acquisition of io, an AI hardware start-up founded by former Apple designer Jony Ive in 2024. In September 2025, OpenAI agreed to acquire the product testing startup Statsig for $1.1 billion in an all-stock deal and appointed Statsig's founding CEO Vijaye Raji as OpenAI's chief technology officer of applications. The company also announced development of an AI-driven hiring service designed to rival LinkedIn. OpenAI acquired personal finance app Roi in October 2025. In October 2025, OpenAI acquired Software Applications Incorporated, the developer of Sky, a macOS-based natural language interface designed to operate across desktop applications. The Sky team joined OpenAI, and the company announced plans to integrate Sky’s capabilities into ChatGPT. In December 2025, it was announced OpenAI had agreed to acquire Neptune, an AI tooling startup that helps companies track and manage model training, for an undisclosed amount. In January 2026, it was announced OpenAI had acquired healthcare technology startup Torch for approximately $60 million. The acquisition followed the launch of OpenAI’s ChatGPT Health product and was intended to strengthen the company’s medical data and healthcare artificial intelligence capabilities. OpenAI has been criticized for outsourcing the annotation of data sets to Sama, a company based in San Francisco that employed workers in Kenya. These annotations were used to train an AI model to detect toxicity, which could then be used to moderate toxic content, notably from ChatGPT's training data and outputs. However, these pieces of text usually contained detailed descriptions of various types of violence, including sexual violence. The investigation uncovered that OpenAI began sending snippets of data to Sama as early as November 2021. The four Sama employees interviewed by Time described themselves as mentally scarred. OpenAI paid Sama $12.50 per hour of work, and Sama was redistributing the equivalent of between $1.32 and $2.00 per hour post-tax to its annotators. Sama's spokesperson said that the $12.50 was also covering other implicit costs, among which were infrastructure expenses, quality assurance and management. In 2024, OpenAI began collaborating with Broadcom to design a custom AI chip capable of both training and inference, targeted for mass production in 2026 and to be manufactured by TSMC on a 3 nm process node. This initiative intended to reduce OpenAI's dependence on Nvidia GPUs, which are costly and face high demand in the market. In January 2024, Arizona State University purchased ChatGPT Enterprise in OpenAI's first deal with a university. In June 2024, Apple Inc. signed a contract with OpenAI to integrate ChatGPT features into its products as part of its new Apple Intelligence initiative. In June 2025, OpenAI began renting Google Cloud's Tensor Processing Units (TPUs) to support ChatGPT and related services, marking its first meaningful use of non‑Nvidia AI chips. In September 2025, it was revealed that OpenAI signed a contract with Oracle to purchase $300 billion in computing power over the next five years. In September 2025, OpenAI and NVIDIA announced a memorandum of understanding that included a potential deployment of at least 10 gigawatts of NVIDIA systems and a $100 billion investment from NVIDIA in OpenAI. OpenAI expected the negotiations to be completed within weeks. As of January 2026, this has not been realized, and the two sides are rethinking the future of their partnership. In October 2025, OpenAI announced a multi-billion dollar deal with AMD. OpenAI committed to purchasing six gigawatts worth of AMD chips, starting with the MI450. OpenAI will have the option to buy up to 160 million shares of AMD, about 10% of the company, depending on development, performance and share price targets. In December 2025, Disney said it would make a $1 billion investment in OpenAI, and signed a three-year licensing deal that will let users generate videos using Sora—OpenAI's short-form AI video platform. More than 200 Disney, Marvel, Star Wars and Pixar characters will be available to OpenAI users. In early 2026, Amazon entered advanced discussions to invest up to $50 billion in OpenAI as part of a potential artificial intelligence partnership. Under the proposed agreement, OpenAI’s models could be integrated into Amazon’s digital assistant Alexa and other internal projects. OpenAI provides LLMs to the Artificial Intelligence Cyber Challenge and to the Advanced Research Projects Agency for Health. In October 2024, The Intercept revealed that OpenAI's tools are considered "essential" for AFRICOM's mission and included in an "Exception to Fair Opportunity" contractual agreement between the United States Department of Defense and Microsoft. In December 2024, OpenAI said it would partner with defense-tech company Anduril to build drone defense technologies for the United States and its allies. In 2025, OpenAI's Chief Product Officer, Kevin Weil, was commissioned lieutenant colonel in the U.S. Army to join Detachment 201 as senior advisor. In June 2025, the U.S. Department of Defense awarded OpenAI a $200 million one-year contract to develop AI tools for military and national security applications. OpenAI announced a new program, OpenAI for Government, to give federal, state, and local governments access to its models, including ChatGPT. Services In February 2019, GPT-2 was announced, which gained attention for its ability to generate human-like text. In 2020, OpenAI announced GPT-3, a language model trained on large internet datasets. GPT-3 is aimed at natural language answering questions, but it can also translate between languages and coherently generate improvised text. It also announced that an associated API, named the API, would form the heart of its first commercial product. Eleven employees left OpenAI, mostly between December 2020 and January 2021, in order to establish Anthropic. In 2021, OpenAI introduced DALL-E, a specialized deep learning model adept at generating complex digital images from textual descriptions, utilizing a variant of the GPT-3 architecture. In December 2022, OpenAI received widespread media coverage after launching a free preview of ChatGPT, its new AI chatbot based on GPT-3.5. According to OpenAI, the preview received over a million signups within the first five days. According to anonymous sources cited by Reuters in December 2022, OpenAI Global, LLC was projecting $200 million of revenue in 2023 and $1 billion in revenue in 2024. After ChatGPT was launched, Google announced a similar chatbot, Bard, amid internal concerns that ChatGPT could threaten Google’s position as a primary source of online information. On February 7, 2023, Microsoft announced that it was building AI technology based on the same foundation as ChatGPT into Microsoft Bing, Edge, Microsoft 365 and other products. On March 14, 2023, OpenAI released GPT-4, both as an API (with a waitlist) and as a feature of ChatGPT Plus. On November 6, 2023, OpenAI launched GPTs, allowing individuals to create customized versions of ChatGPT for specific purposes, further expanding the possibilities of AI applications across various industries. On November 14, 2023, OpenAI announced they temporarily suspended new sign-ups for ChatGPT Plus due to high demand. Access for newer subscribers re-opened a month later on December 13. In December 2024, the company launched the Sora model. It also launched OpenAI o1, an early reasoning model that was internally codenamed strawberry. Additionally, ChatGPT Pro—a $200/month subscription service offering unlimited o1 access and enhanced voice features—was introduced, and preliminary benchmark results for the upcoming OpenAI o3 models were shared. On January 23, 2025, OpenAI released Operator, an AI agent and web automation tool for accessing websites to execute goals defined by users. The feature was only available to Pro users in the United States. OpenAI released deep research agent, nine days later. It scored a 27% accuracy on the benchmark Humanity's Last Exam (HLE). Altman later stated GPT-4.5 would be the last model without full chain-of-thought reasoning. In July 2025, reports indicated that AI models by both OpenAI and Google DeepMind solved mathematics problems at the level of top-performing students in the International Mathematical Olympiad. OpenAI's large language model was able to achieve gold medal-level performance, reflecting significant progress in AI's reasoning abilities. On October 6, 2025, OpenAI unveiled its Agent Builder platform during the company's DevDay event. The platform includes a visual drag-and-drop interface that lets developers and businesses design, test, and deploy agentic workflows with limited coding. On October 21, 2025, OpenAI introduced ChatGPT Atlas, a browser integrating the ChatGPT assistant directly into web navigation, to compete with existing browsers such as Google Chrome and Apple Safari. On December 11, 2025, OpenAI announced GPT-5.2. This model will be better at creating spreadsheets, building presentations, perceiving images, writing code and understanding long context. On January 27, 2026, OpenAI introduced Prism, a LaTeX-native workspace meant to assist scientists to help with research and writing. The platform utilizes GPT-5.2 as a backend to automate the process of drafting for scientific papers, including features for managing citations, complex equation formatting, and real-time collaborative editing. In March 2023, the company was criticized for disclosing particularly few technical details about products like GPT-4, contradicting its initial commitment to openness and making it harder for independent researchers to replicate its work and develop safeguards. OpenAI cited competitiveness and safety concerns to justify this repudiation. OpenAI's former chief scientist Ilya Sutskever argued in 2023 that open-sourcing increasingly capable models was increasingly risky, and that the safety reasons for not open-sourcing the most potent AI models would become "obvious" in a few years. In September 2025, OpenAI published a study on how people use ChatGPT for everyday tasks. The study found that "non-work tasks" (according to an LLM-based classifier) account for more than 72 percent of all ChatGPT usage, with a minority of overall usage related to business productivity. In July 2023, OpenAI launched the superalignment project, aiming within four years to determine how to align future superintelligent systems. OpenAI promised to dedicate 20% of its computing resources to the project, although the team denied receiving anything close to 20%. OpenAI ended the project in May 2024 after its co-leaders Ilya Sutskever and Jan Leike left the company. In August 2025, OpenAI was criticized after thousands of private ChatGPT conversations were inadvertently exposed to public search engines like Google due to an experimental "share with search engines" feature. The opt-in toggle, intended to allow users to make specific chats discoverable, resulted in some discussions including personal details such as names, locations, and intimate topics appearing in search results when users accidentally enabled it while sharing links. OpenAI announced the feature's permanent removal on August 1, 2025, and the company began coordinating with search providers to remove the exposed content, emphasizing that it was not a security breach but a design flaw that heightened privacy risks. CEO Sam Altman acknowledged the issue in a podcast, noting users often treat ChatGPT as a confidant for deeply personal matters, which amplified concerns about AI handling sensitive data. Management In 2018, Musk resigned from his Board of Directors seat, citing "a potential future conflict [of interest]" with his role as CEO of Tesla due to Tesla's AI development for self-driving cars. OpenAI stated that Musk's financial contributions were below $45 million. On March 3, 2023, Reid Hoffman resigned from his board seat, citing a desire to avoid conflicts of interest with his investments in AI companies via Greylock Partners, and his co-founding of the AI startup Inflection AI. Hoffman remained on the board of Microsoft, a major investor in OpenAI. In May 2024, Chief Scientist Ilya Sutskever resigned and was succeeded by Jakub Pachocki. Co-leader Jan Leike also departed amid concerns over safety and trust. OpenAI then signed deals with Reddit, News Corp, Axios, and Vox Media. Paul Nakasone then joined the board of OpenAI. In August 2024, cofounder John Schulman left OpenAI to join Anthropic, and OpenAI's president Greg Brockman took extended leave until November. In September 2024, CTO Mira Murati left the company. In November 2025, Lawrence Summers resigned from the board of directors. Governance and legal issues In May 2023, Sam Altman, Greg Brockman and Ilya Sutskever posted recommendations for the governance of superintelligence. They stated that superintelligence could happen within the next 10 years, allowing a "dramatically more prosperous future" and that "given the possibility of existential risk, we can't just be reactive". They proposed creating an international watchdog organization similar to IAEA to oversee AI systems above a certain capability threshold, suggesting that relatively weak AI systems on the other side should not be overly regulated. They also called for more technical safety research for superintelligences, and asked for more coordination, for example through governments launching a joint project which "many current efforts become part of". In July 2023, the FTC issued a civil investigative demand to OpenAI to investigate whether the company's data security and privacy practices to develop ChatGPT were unfair or harmed consumers (including by reputational harm) in violation of Section 5 of the Federal Trade Commission Act of 1914. These are typically preliminary investigative matters and are nonpublic, but the FTC's document was leaked. In July 2023, the FTC launched an investigation into OpenAI over allegations that the company scraped public data and published false and defamatory information. They asked OpenAI for comprehensive information about its technology and privacy safeguards, as well as any steps taken to prevent the recurrence of situations in which its chatbot generated false and derogatory content about people. The agency also raised concerns about ‘circular’ spending arrangements—for example, Microsoft extending Azure credits to OpenAI while both companies shared engineering talent—and warned that such structures could negatively affect the public. In September 2024, OpenAI's global affairs chief endorsed the UK's "smart" AI regulation during testimony to a House of Lords committee. In February 2025, OpenAI CEO Sam Altman stated that the company is interested in collaborating with the People's Republic of China, despite regulatory restrictions imposed by the U.S. government. This shift comes in response to the growing influence of the Chinese artificial intelligence company DeepSeek, which has disrupted the AI market with open models, including DeepSeek V3 and DeepSeek R1. Following DeepSeek's market emergence, OpenAI enhanced security protocols to protect proprietary development techniques from industrial espionage. Some industry observers noted similarities between DeepSeek's model distillation approach and OpenAI's methodology, though no formal intellectual property claim was filed. According to Oliver Roberts, in March 2025, the United States had 781 state AI bills or laws. OpenAI advocated for preempting state AI laws with federal laws. According to Scott Kohler, OpenAI has opposed California's AI legislation and suggested that the state bill encroaches on a more competent federal government. Public Citizen opposed a federal preemption on AI and pointed to OpenAI's growth and valuation as evidence that existing state laws have not hampered innovation. Before May 2024, OpenAI required departing employees to sign a lifelong non-disparagement agreement forbidding them from criticizing OpenAI and acknowledging the existence of the agreement. Daniel Kokotajlo, a former employee, publicly stated that he forfeited his vested equity in OpenAI in order to leave without signing the agreement. Sam Altman stated that he was unaware of the equity cancellation provision, and that OpenAI never enforced it to cancel any employee's vested equity. However, leaked documents and emails refute this claim. On May 23, 2024, OpenAI sent a memo releasing former employees from the agreement. OpenAI was sued for copyright infringement by authors Sarah Silverman, Matthew Butterick, Paul Tremblay and Mona Awad in July 2023. In September 2023, 17 authors, including George R. R. Martin, John Grisham, Jodi Picoult and Jonathan Franzen, joined the Authors Guild in filing a class action lawsuit against OpenAI, alleging that the company's technology was illegally using their copyrighted work. The New York Times also sued the company in late December 2023. In May 2024 it was revealed that OpenAI had destroyed its Books1 and Books2 training datasets, which were used in the training of GPT-3, and which the Authors Guild believed to have contained over 100,000 copyrighted books. In 2021, OpenAI developed a speech recognition tool called Whisper. OpenAI used it to transcribe more than one million hours of YouTube videos into text for training GPT-4. The automated transcription of YouTube videos raised concerns within OpenAI employees regarding potential violations of YouTube's terms of service, which prohibit the use of videos for applications independent of the platform, as well as any type of automated access to its videos. Despite these concerns, the project proceeded with notable involvement from OpenAI's president, Greg Brockman. The resulting dataset proved instrumental in training GPT-4. In February 2024, The Intercept as well as Raw Story and Alternate Media Inc. filed lawsuit against OpenAI on copyright litigation ground. The lawsuit is said to have charted a new legal strategy for digital-only publishers to sue OpenAI. On April 30, 2024, eight newspapers filed a lawsuit in the Southern District of New York against OpenAI and Microsoft, claiming illegal harvesting of their copyrighted articles. The suing publications included The Mercury News, The Denver Post, The Orange County Register, St. Paul Pioneer Press, Chicago Tribune, Orlando Sentinel, Sun Sentinel, and New York Daily News. In June 2023, a lawsuit claimed that OpenAI scraped 300 billion words online without consent and without registering as a data broker. It was filed in San Francisco, California, by sixteen anonymous plaintiffs. They also claimed that OpenAI and its partner as well as customer Microsoft continued to unlawfully collect and use personal data from millions of consumers worldwide to train artificial intelligence models. On May 22, 2024, OpenAI entered into an agreement with News Corp to integrate news content from The Wall Street Journal, the New York Post, The Times, and The Sunday Times into its AI platform. Meanwhile, other publications like The New York Times chose to sue OpenAI and Microsoft for copyright infringement over the use of their content to train AI models. In November 2024, a coalition of Canadian news outlets, including the Toronto Star, Metroland Media, Postmedia, The Globe and Mail, The Canadian Press and CBC, sued OpenAI for using their news articles to train its software without permission. In October 2024 during a New York Times interview, Suchir Balaji accused OpenAI of violating copyright law in developing its commercial LLMs which he had helped engineer. He was a likely witness in a major copyright trial against the AI company, and was one of several of its current or former employees named in court filings as potentially having documents relevant to the case. On November 26, 2024, Balaji died by suicide. His death prompted the circulation of conspiracy theories alleging that he had been deliberately silenced. California Congressman Ro Khanna endorsed calls for an investigation. On April 24, 2025, Ziff Davis sued OpenAI in Delaware federal court for copyright infringement. Ziff Davis is known for publications such as ZDNet, PCMag, CNET, IGN and Lifehacker. In April 2023, the EU's European Data Protection Board (EDPB) formed a dedicated task force on ChatGPT "to foster cooperation and to exchange information on possible enforcement actions conducted by data protection authorities" based on the "enforcement action undertaken by the Italian data protection authority against OpenAI about the ChatGPT service". In late April 2024 NOYB filed a complaint with the Austrian Datenschutzbehörde against OpenAI for violating the European General Data Protection Regulation. A text created with ChatGPT gave a false date of birth for a living person without giving the individual the option to see the personal data used in the process. A request to correct the mistake was denied. Additionally, neither the recipients of ChatGPT's work nor the sources used, could be made available, OpenAI claimed. OpenAI was criticized for lifting its ban on using ChatGPT for "military and warfare". Up until January 10, 2024, its "usage policies" included a ban on "activity that has high risk of physical harm, including", specifically, "weapons development" and "military and warfare". Its new policies prohibit "[using] our service to harm yourself or others" and to "develop or use weapons". In August 2025, the parents of a 16-year-old boy who died by suicide filed a wrongful death lawsuit against OpenAI (and CEO Sam Altman), alleging that months of conversations with ChatGPT about mental health and methods of self-harm contributed to their son's death and that safeguards were inadequate for minors. OpenAI expressed condolences and said it was strengthening protections (including updated crisis response behavior and parental controls). Coverage described it as a first-of-its-kind wrongful death case targeting the company's chatbot. The complaint was filed in California state court in San Francisco. In November 2025, the Social Media Victims Law Center and Tech Justice Law Project filed seven lawsuits against OpenAI, of which four lawsuits alleged wrongful death. The suits were filed on behalf of Zane Shamblin, 23, of Texas; Amaurie Lacey, 17, of Georgia; Joshua Enneking, 26, of Florida; and Joe Ceccanti, 48, of Oregon, who each committed suicide after prolonged ChatGPT usage. In December 2025, Stein-Erik Soelberg, who was 56 years old at the time, allegedly murdered his mother Suzanne Adams. In the months prior the paranoid, delusional man often discussed his ideas with ChatGPT. Adam's estate then sued OpenAI claiming that the company shared responsibility due to the risk of chatbot psychosis despite the fact that chatbot psychosis is not a real medical diagnosis. OpenAI responded saying they will make ChatGPT safer for users disconnected from reality. See also References Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/Gastropod] | [TOKENS: 5175] |
Contents Gastropoda Gastropods (/ˈɡæstrəpɒdz/; previously known as Univalves; class Gastropoda /ɡæsˈtrɒpədə/) are a vast and diverse group of invertebrates within the phylum Mollusca, comprising the animals commonly known as snails and slugs. With an estimated 65,000 to 80,000 living species, they form the second-largest animal class after the insects. The fossil record of gastropods extends back to the Late Cambrian. As of 2017[update], 721 families are recognized—476 extant (some with fossil representatives) and 245 extinct known only from fossils. Gastropods inhabit an extraordinary range of environments, including marine, freshwater, and terrestrial ecosystems. They occur in gardens, woodlands, deserts, mountains, rivers, lakes, estuaries, mudflats, intertidal zones, the deep sea, hydrothermal vents, and even in parasitic niches. The term snail generally refers to gastropods with a large external shell into which the body can fully retract, while slugs have no shell or a small internal one, and semislugs can only partially withdraw into their reduced shell. Marine gastropods include familiar forms such as abalones, conches, periwinkles, whelks, and cowries, whose shells are usually coiled in adulthood. In contrast, limpets and related groups coil their shells only in the larval stage, retaining a simple conical form as adults. Because of their vast diversity, gastropods exhibit remarkable variation in anatomy, behavior, feeding, and reproduction, making broad generalizations difficult. Gastropods remain one of evolution’s most successful and adaptable animal lineages. Etymology In the scientific literature, gastropods were described as "gasteropodes" by Georges Cuvier in 1795. The word gastropod comes from Greek γαστήρ (gastḗr 'stomach') and πούς (poús 'foot'), a reference to the fact that the animal's "foot" is positioned below its guts. The earlier name "univalve" means one valve (or shell), in contrast to bivalves, such as clams, which have two valves or shells. Diversity At all taxonomic levels, gastropods are second only to insects in terms of their diversity. Gastropods have the greatest numbers of named mollusk species. However, estimates of the total number of gastropod species vary widely, depending on cited sources. The number of gastropod species can be ascertained from estimates of the number of described species of Mollusca with accepted names: about 85,000 (minimum 50,000, maximum 120,000). But an estimate of the total number of Mollusca, including undescribed species, is about 240,000 species. The estimate of 85,000 mollusks includes 24,000 described species of terrestrial gastropods. Different estimates for aquatic gastropods (based on different sources) give about 30,000 species of marine gastropods, and about 5,000 species of freshwater and brackish gastropods. Many deep-sea species remain to be discovered, as only 0.0001% of the deep-sea floor has been studied biologically. The total number of living species of freshwater snails is about 4,000. Recently extinct species of gastropods (extinct since 1500) number 444, 18 species are now extinct in the wild (but still exist in captivity), and 69 species are "possibly extinct". The number of prehistoric (fossil) species of gastropods is at least 15,000 species. In marine habitats, the continental slope and the continental rise are home to the highest diversity, while the continental shelf and abyssal depths have a low diversity of marine gastropods. Habitat Gastropods are found in a wide range of aquatic and terrestrial habitats, from deep ocean trenches to deserts.[citation needed] Some of the more familiar and better-known gastropods are terrestrial gastropods (the land snails and slugs). Some live in fresh water, but most named species of gastropods live in a marine environment. [citation needed] Gastropods have a worldwide distribution, from the near Arctic and Antarctic zones to the tropics. They have become adapted to almost every kind of existence on earth, having colonized nearly every available medium.[citation needed] In habitats where not enough calcium carbonate is available to build a really solid shell, such as on some acidic soils on land, various species of slugs occur, and also some snails with thin, translucent shells, mostly or entirely composed of the protein conchiolin.[citation needed] Snails such as Sphincterochila boissieri and Xerocrassa seetzeni have adapted to desert conditions. Other snails have adapted to an existence in ditches, near deepwater hydrothermal vents, in oceanic trenches 10,000 meters (6 miles) below the surface, the pounding surf of rocky shores, caves, and many other diverse areas. Gastropods can be accidentally transferred from one habitat to another by other animals, e.g. by birds. Anatomy Snails are distinguished by an anatomical process known as torsion, where the visceral mass of the animal rotates 180° to one side during development, such that the anus is situated more or less above the head. This process is unrelated to the coiling of the shell, which is a separate phenomenon. Torsion is present in all gastropods, but the opisthobranch gastropods are secondarily untorted to various degrees. Torsion occurs in two stages. The first, mechanistic stage is muscular, and the second is mutagenetic. The effects of torsion are primarily physiological. The organism develops by asymmetrical growth, with the majority of growth occurring on the left side. This leads to the loss of right-side anatomy that in most bilaterians is a duplicate of the left side anatomy. The essential feature of this asymmetry is that the anus generally lies to one side of the median plane. The gill-combs, the olfactory organs, the foot slime-gland, nephridia, and the auricle of the heart are single or at least are more developed on one side of the body than the other. Furthermore, there is only one genital orifice, which lies on the same side of the body as the anus. Furthermore, the anus becomes redirected to the same space as the head. This is speculated to have some evolutionary function, as prior to torsion, when retracting into the shell, first the posterior end would get pulled in, and then the anterior. Now, the front can be retracted more easily, perhaps suggesting a defensive purpose.[citation needed] Gastropods typically have a well-defined head with two or four sensory tentacles with eyes, and a ventral foot. The foremost division of the foot is called the propodium. Its function is to push away sediment as the snail crawls. The larval shell of a gastropod is called a protoconch.[citation needed] Most shelled gastropods have a one piece shell (with exceptional bivalved gastropods), typically coiled or spiraled, at least in the larval stage. This coiled shell usually opens on the right-hand side (as viewed with the shell apex pointing upward). Numerous species have an operculum, which in many species acts as a trapdoor to close the shell. This is usually made of a horn-like material, but in some molluscs it is calcareous. In the land slugs, the shell is reduced or absent, and the body is streamlined.[citation needed] Some gastropods have adult shells which are bottom heavy due to the presence of a thick, often broad, convex ventral callus deposit on the inner lip and adapical to the aperture which may be important for gravitational stability. Most snail species possess a dextral (right-coiled) shell, which mirrors their internal anatomy. However, sinistral (left-coiled) shells are the obligate and standard form in several large families and genera (such as Physidae and most Clausiliidae), where the internal anatomy is symmetrically reversed. Some sea slugs are very brightly colored. This serves either as a warning, when they are poisonous or contain stinging cells, or to camouflage them on the brightly colored hydroids, sponges, and seaweeds on which many of the species are found.[citation needed] Lateral outgrowths on the body of nudibranchs are called cerata. These contain an outpocketing of digestive glands called the diverticula. The sensory organs of gastropods include olfactory organs, eyes, statocysts and mechanoreceptors. Gastropods have no hearing. In terrestrial gastropods (land snails and slugs), the olfactory organs, located on the tips of the four tentacles, are the most important sensory organ. The chemosensory organs of opisthobranch marine gastropods are called rhinophores. The majority of gastropods have simple visual organs, eye spots either at the tip or base of the tentacles. However, "eyes" in gastropods range from simple ocelli that only distinguish light and dark, to more complex pit eyes, and even to lens eyes. In land snails and slugs, vision is not the most important sense, because they are mainly nocturnal animals. The nervous system of gastropods includes the peripheral nervous system and the central nervous system. The central nervous system consists of ganglia connected by nerve cells. It includes paired ganglia: the cerebral ganglia, pedal ganglia, osphradial ganglia, pleural ganglia, parietal ganglia and the visceral ganglia. There are sometimes also buccal ganglia. The radula of a gastropod is usually adapted to the food that a species eats. The simplest gastropods are the limpets and abalone, herbivores that use their hard radula to rasp at seaweeds on rocks.[citation needed] Many marine gastropods are burrowers, and have a siphon that extends out from the mantle edge. Sometimes the shell has a siphonal canal to accommodate this structure. A siphon enables the animal to draw water into their mantle cavity and over the gill. They use the siphon primarily to "taste" the water to detect prey from a distance. Gastropods with siphons tend to be either predators or scavengers.[citation needed] Almost all marine gastropods breathe with a gill, but many freshwater species, and the majority of terrestrial species, have a pallial lung. The respiratory protein in almost all gastropods is hemocyanin, but one freshwater pulmonate family, the Planorbidae, have hemoglobin as the respiratory protein.[citation needed] In one large group of sea slugs, the gills are arranged as a rosette of feathery plumes on their backs, which gives rise to their other name, nudibranchs. Some nudibranchs have smooth or warty backs with no visible gill mechanism, such that respiration may likely take place directly through the skin. Gastropods have open circulatory system and the transport fluid is hemolymph. Hemocyanin is present in the hemolymph as the respiratory pigment.[citation needed] The primary organs of excretion in gastropods are nephridia, which produce either ammonia or uric acid as a waste product. The nephridium also plays an important role in maintaining water balance in freshwater and terrestrial species. Additional organs of excretion, at least in some species, include pericardial glands in the body cavity, and digestive glands opening into the stomach.[citation needed] Courtship is a part of mating behavior in some gastropods, including some of the Helicidae. Again, in some land snails, an unusual feature of the reproductive system of gastropods is the presence and utilization of love darts.[citation needed] In many marine gastropods other than the opisthobranchs, there are separate sexes (dioecious/gonochoric); most land gastropods, however, are hermaphrodites.[citation needed] Life cycle Courtship is a part of the behavior of mating gastropods with some pulmonate families of land snails creating and utilizing love darts, the throwing of which have been identified as a form of sexual selection. The main aspects of the life cycle of gastropods include: Feeding behavior The diet of gastropods differs according to the group considered. Marine gastropods include some that are herbivores, detritus feeders, predatory carnivores, scavengers, parasites, and also a few ciliary feeders, in which the radula is reduced or absent. Land-dwelling species can chew up leaves, bark, fruit, fungi, and decomposing animals while marine species can scrape algae off the rocks on the seafloor. Certain species such as the Archaeogastropoda maintain horizontal rows of slender marginal teeth. In some species that have evolved into endoparasites, such as the eulimid Thyonicola doglieli, many of the standard gastropod features are strongly reduced or absent.[citation needed] A few sea slugs are herbivores and some are carnivores. The carnivorous habit is due to specialisation. Many gastropods have distinct dietary preferences and regularly occur in close association with their food species.[citation needed] Some predatory carnivorous gastropods include: cone shells, Testacella, Daudebardia, turrids, ghost slugs and others.[citation needed] Studies based on direct observations, fecal and gut analyses, as well as food-choice experiments, have revealed that snails and slugs consume a wide variety of food resources. Their diet spans from living plants at various developmental stages such as pollen, seeds, seedlings, and wood, to decaying plant material like leaf litter. Additionally, they feed on fungi, lichens, algae, soil, and even other animals, both living and dead, including their feces. Given this diverse diet, terrestrial gastropods can be classified as herbivores, omnivores, carnivores, and detritivores. However, the majority are microbivores, primarily consuming microbes associated with decaying organic material. Despite their ecological importance, there is a notable lack of research exploring the specific roles that terrestrial gastropods play within soil food webs. Many terrestrial gastropod mollusks are known to consume fungi, a behavior observed in various species of snails and slugs across distinct families. Notable examples of fungivore slugs include members of the family Philomycidae, which feed on slime molds (myxomycetes), and the Ariolimacidae, which primarily consume mushrooms (basidiomycetes). Snail families that contain fungivore species include Clausiliidae, Macrocyclidae, and Polygyridae. Mushroom-producing fungi used as a food source by snails and slugs include species from several genera. Some examples are milk-caps (Lactarius spp.), the oyster mushroom (Pleurotus ostreatus), and the penny bun. Additionally, slugs feed on fungi from other genera, such as Agaricus, Pleurocybella, and Russula. Snails have also been reported to feed on penny buns as well as Coprinellus, Aleurodiscus, Armillaria, Grifola , Marasmiellus, Mycena, Pholiota, and Ramaria. As for slime molds, commonly consumed species include Stemonitis axifera and Symphytocarpus flaccidus. Feeding behaviors in slugs exhibit considerable variation. Some species display selectivity, consuming specific parts or developmental stages of fungi. For instance, certain slugs may target fungi only at particular stages of maturity, such as immature fruiting bodies or spore-producing structures. Conversely, other species show little to no selectivity, consuming entire mushrooms regardless of developmental stage. This variability stresses the diverse dietary adaptations among slug species and their ecological roles in fungal consumption. Moreover, by consuming fungi, snails and slugs can also indirectly help in their dispersal by carrying along some of their spores or the fungi themselves. Genetics Gastropods exhibit an important degree of variation in mitochondrial gene organization when compared to other animals. Main events of gene rearrangement occurred at the origin of Patellogastropoda and Heterobranchia, whereas fewer changes occurred between the ancestors of Vetigastropoda (only tRNAs D, C and N) and Caenogastropoda (a large single inversion, and translocations of the tRNAs D and N). Within Heterobranchia, gene order seems relatively conserved, and gene rearrangements are mostly related with transposition of tRNA genes. Geological history and evolution The first gastropods were exclusively marine, with the earliest known representatives appearing in the Late Cambrian (e.g., Chippewaella, Strepsodiscus). However, their only definitive gastropod feature is a coiled shell, which raises the possibility that they may belong to the stem lineage of gastropods, or might not be gastropods at all. Early Cambrian species such as Helcionella, Barskovia, and Scenella are no longer considered gastropods, and the small coiled Aldanella from the same period is probably not even a mollusk.[citation needed] It is not until the Ordovician that true crown-group gastropods appear. By this time, gastropods had diversified into a variety of forms and inhabited a range of aquatic environments. Fossil gastropods from the early Paleozoic are often poorly preserved, making identification difficult. However, the Silurian genus Poleumita contains at least 15 identified species. Overall, gastropods were less common in the Paleozoic than bivalves. Most Paleozoic gastropods belong to primitive groups, some of which still exist today. By the Carboniferous period, many gastropod shell shapes found in fossils resemble those of modern species, though most of these early forms are not directly related to living gastropods. It was during the Mesozoic era that the ancestors of many extant gastropods evolved. One of the earliest known terrestrial gastropods is Anthracopupa (or Maturipupa), found in the Carboniferous Coal Measures of Europe. However, land snails and their relatives were rare before the Cretaceous period. In Mesozoic rocks, gastropods become more common in the fossil record, with well-preserved shells. Fossils are found in ancient beds from both freshwater and marine environments. Notable examples include the Purbeck Marble of the Jurassic and the Sussex Marble of the early Cretaceous, both from southern England. These limestones contain abundant remains of the pond snail Viviparus. Cenozoic rocks yield vast numbers of gastropod fossils, many of which are closely related to modern species. The diversity of gastropods increased significantly at the start of this era, alongside that of bivalves. Certain trail-like markings preserved in ancient sedimentary rocks are thought to have been made by gastropods crawling over the soft mud and sand. Although these trace fossils are of debatable origin, some of them do resemble the trails made by living gastropods today. Gastropod fossils may sometimes be confused with ammonites or other shelled cephalopods. An example of this is Bellerophon from the limestones of the Carboniferous period in Europe, the shell of which is planispirally coiled and can be mistaken for the shell of a cephalopod.[citation needed] Gastropods also provide important evidence of faunal changes during the Pleistocene epoch, reflecting the impacts of advancing and retreating ice sheets.[citation needed] A cladogram showing the phylogenic relationships of Gastropoda with example species: Panpulmonata ► Euopisthobranchia ► Nudipleura ► Caenogastropoda Neritimorpha Vetigastropoda Patellogastropoda ► Neomphaliones and Lower Heterobranchia are not included in the above cladogram. Taxonomy The present backbone classification of gastropods relies on the results of phylogenomic analyses. Consensus has not been reached yet considering the relationships at the very base of the gastropod tree of life, but otherwise the major groups are known with confidence. Since Darwin, biological taxonomy has attempted to reflect the phylogeny of organisms, i.e., the tree of life. The classifications used in taxonomy attempt to represent the precise interrelatedness of the various taxa. However, the taxonomy of the Gastropoda is constantly being revised and so the versions shown in various texts can differ in major ways.[citation needed] In the older classification of the gastropods, there were four subclasses: The taxonomy of the Gastropoda is still under revision, and more and more of the old taxonomy is being abandoned, as the results of DNA studies slowly become clearer. Nevertheless, a few of the older terms such as "opisthobranch" and "prosobranch" are still sometimes used in a descriptive way.[citation needed] New insights based on DNA sequencing of gastropods have produced some revolutionary new taxonomic insights. In the case of the Gastropoda, the taxonomy is now gradually being rewritten to embody strictly monophyletic groups (only one lineage of gastropods in each group). Integrating new findings into a working taxonomy remain challenging. Consistent ranks within the taxonomy at the level of subclass, superorder, order, and suborder have already been abandoned as unworkable. Ongoing revisions of the higher taxonomic levels are expected in the near future.[when?] Convergent evolution, which appears to exist at especially high frequency in gastropods, may account for the observed differences between the older phylogenies, which were based on morphological data, and more recent gene-sequencing studies.[citation needed] In 2004, Brian Simison and David R. Lindberg showed possible diphyletic origins of the Gastropoda based on mitochondrial gene order and amino acid sequence analyses of complete genes. In 2005, Philippe Bouchet and Jean-Pierre Rocroi made sweeping changes in the systematics, resulting in the Bouchet & Rocroi taxonomy, which is a step closer to the evolutionary history of the phylum. The Bouchet & Rocroi classification system is based partly on the older systems of classification, and partly on new cladistic research. In the past, the taxonomy of gastropods was largely based on phenetic morphological characters of the taxa. The recent advances are more based on molecular characters from DNA and RNA research. This has made the taxonomical ranks and their hierarchy controversial. In 2017, Bouchet, Rocroi, and other collaborators published a significantly updated version of the 2005 taxonomy. In the Bouchet et al. taxonomy, the authors used unranked clades for taxa above the rank of superfamily (replacing the ranks suborder, order, superorder and subclass), while using the traditional Linnaean approach for all taxa below the rank of superfamily. Whenever monophyly has not been tested, or is known to be paraphyletic or polyphyletic, the term "group" or "informal group" has been used. The classification of families into subfamilies is often not well resolved.[citation needed] Fixed ranks like family, genus, and species however remain useful for practical classification and remain used in the World Register of Marine Species (WoRMS). Also many researchers continue to use traditional ranks because they are entrenched in the literature and familiar to specialists and non-specialists alike. Ecology and conservation Many gastropod species face threats from habitat destruction, pollution, and climate change. Some species are endangered or have become extinct due to these factors. Conservation efforts often focus on protecting their habitats, especially in freshwater and terrestrial ecosystems. Gastropods are prey to a wide range of organisms depending on the environment. In marine habitats, gastropods are preyed upon by fish, marine birds, marine mammals, crustaceans, and other mollusks such as cephalopods. In terrestrial environments, gastropod predators include insects, arachnids (spiders, harvestmen), birds, and mammals, among others. References Sources External links |
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[SOURCE: https://en.wikipedia.org/wiki/Social_network#cite_ref-10] | [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/Blaze_(toy)] | [TOKENS: 377] |
Contents Blaze (toy) Blaze was a rocking horse toy produced by Mattel toymakers and introduced in 1961. Blaze was featured prominently during children's television advertising (Mattel was the first toymaker to advertise year around with television commercials). Unlike other rocking-horses of the time, Blaze was mounted on a stand that was said to be "untippable" and had no springs. The apparatus prevented pinched fingers, and was fitted out with a mechanism that moved the horses legs in "real life action." Another Mattel feature allowed Blaze to talk when you pulled his "Magic Ring." His talking voice unit was the very same one produced by Mattel and unveiled in 1960 in its talking Chatty Cathy doll, and later toys like the Talking Mister Ed puppet. Blaze could say 11 different things like, "How about some hay?"; he could also whinny and neigh. A toy like this, that could gallop and move realistically when the horse was rocked forward and backward, was something special. Blaze was made of what Mattel called "hi-impact plastic" with black-and-white markings (a pinto pony), and a molded black saddle and red blanket. Blaze also had attached reins, fixed hand-posts, and 2-position foot rests. The stand was made of 1-inch tubular steel and was advertised as being "untippable." Saddle height was 29 inches and was recommended for ages 1–7. Blaze was marketed in most retail catalogs, such as Sears, JCPenney, and Montgomery Ward. When first issued, Blaze did not have the talking feature, this was added very quickly after his initial release, so there may be versions of this toy that do not, and never did, talk. References This toy-related article is a stub. You can help Wikipedia by adding missing information. |
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[SOURCE: https://en.wikipedia.org/wiki/Mattel_Brick_Shop] | [TOKENS: 101] |
Contents Mattel Brick Shop Mattel Brick Shop is a brand of construction sets produced by Mattel. The product line was first released in 2025, and has been described as a competitor to Lego. Release The product line was first revealed at the Nuremberg International Toy Fair in February 2025. Seven sets were released initially, which were based on Mattel's Hot Wheels toy line. In early 2026, collaborations with several more car companies were announced. See also References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Hexadecimal] | [TOKENS: 3505] |
Contents Hexadecimal Hexadecimal (hex for short) is a positional numeral system for representing a numeric value as base 16. For the most common convention, a digit is represented as "0" to "9" like for decimal and as a letter of the alphabet from "A" to "F" (either upper or lower case) for the digits with decimal value 10 to 15. As typical computer hardware is binary in nature and that hex is power of 2, the hex representation is often used in computing as a dense representation of binary information. A hex digit represents 4 contiguous bits –known as a nibble. An 8-bit byte is two hex digits, such as 2C. Special notation is often used to indicate that a number is hex. In mathematics, a subscript is typically used to specify the base. For example, the decimal value 491 would be expressed in hex as 1EB16. In computer programming, various notations are used. In C and many related languages, the prefix 0x is used. For example, 0x1EB. Written representation Typically, a hex representation convention allows either lower or upper case letters and treats the letter the same regardless of its case. Often when rendering non-textual data, a value stored in memory is displayed as a sequence of hex digits with spaces between values. For instance, in the following hex dump, each 8-bit byte is a 2-digit hex number, with spaces between them, while the 32-bit offset at the start is an 8-digit hex number. There are several conventions for expressing that a number is represented as hex. In some contexts, a number is always written as hex, and therefore, needs no identification notation. Notable other hexadecimal representations that use symbols other than letters "A" through "F" to represent the digits above 9 include: The hex system can express negative numbers the same way as in decimal, by putting a minus sign (−) before the number to indicate that it is negative. Hex can express the bit pattern in a processor, so a sequence of hex digits may represent a signed or even a floating-point value. This way, the negative number −4210 can be written as FFFF FFD6 in a 32-bit CPU register (in two's complement), as C228 0000 in a 32-bit FPU register or C045 0000 0000 0000 in a 64-bit FPU register (in the IEEE floating-point standard). Just as decimal numbers can be represented in exponential notation, so too can hex numbers. P notation uses the letter P (or p, for "power"), whereas E (or e) serves a similar purpose in decimal E notation. The number after the P is decimal and represents the binary exponent. Increasing the exponent by 1 multiplies by 2, not 16: 20p0 = 10p1 = 8p2 = 4p3 = 2p4 = 1p5. Usually, the number is normalized so that the hex digits start with 1. (zero is usually 0 with no P). Example: 1.3DEp42 represents 1.3DE16 × 24210. P notation is required by the IEEE 754-2008 binary floating-point standard and can be used for floating-point literals in the C99 edition of the C programming language. Using the %a or %A conversion specifiers, this notation can be produced by implementations of the printf family of functions following the C99 specification and Single Unix Specification (IEEE Std 1003.1) POSIX standard. Verbal representation Most European languages lack non-decimal-based words for some of the numerals eleven to fifteen. Some people read hex numbers digit by digit, like a phone number, or using the NATO phonetic alphabet, the Joint Army/Navy Phonetic Alphabet, or a similar ad hoc system. In the wake of the adoption of hex among IBM System/360 programmers, Magnuson (1968) suggested a pronunciation guide that gave short names to the letters of hex – for instance, "A" was pronounced "ann", B "bet", C "chris", etc. Another naming-system was published online by Rogers (2007) that tries to make the verbal representation distinguishable in any case, even when the actual number does not contain numbers A–F. Examples are listed in the tables below. Yet another naming system was elaborated by Babb (2015), based on a joke in Silicon Valley. The system proposed by Babb was further improved by Atkins-Bittner in 2015-2016. Others have proposed using the verbal Morse code conventions to express four-bit hex digits, with "dit" and "dah" representing zero and one, respectively, so that "0000" is voiced as "dit-dit-dit-dit" (....), "dah-dit-dit-dah" (-..-) voices the digit with a value of nine, and "dah-dah-dah-dah" (----) voices the hex digit for decimal 15. Systems of counting on digits have been devised for both binary and hex. Arthur C. Clarke suggested using each finger as an on/off bit, allowing finger counting from zero to 102310 on ten fingers. Another system for counting up to FF16 (25510) is illustrated on the right. Conversion Most computers manipulate binary data, but it is difficult for humans to work with a large number of digits for even a relatively small binary number. Although most humans are familiar with the base 10 system, it is much easier to map binary to hex than to decimal because each hex digit maps to a whole number of bits (410). This example converts 11112 to base ten. Since each position in a binary numeral can contain either a 1 or a 0, its value may be easily determined by its position from the right: Therefore: With little practice, mapping 11112 to F16 in one step becomes easy. The advantage of using hex rather than decimal increases rapidly with the size of the number. When the number becomes large, conversion to decimal is very tedious. However, when mapping to hex, it is trivial to regard the binary string as 4-digit groups and map each to a single hex digit. This example shows the conversion of a binary number to decimal, mapping each digit to the decimal value, and adding the results. Compare this to the conversion to hex, where each group of four digits can be considered independently and converted directly: The conversion from hex to binary is equally direct. Although quaternary (base 4) is little used, it can easily be converted to and from hex or binary. Each hex digit corresponds to a pair of quaternary digits, and each quaternary digit corresponds to a pair of binary digits. In the above example 2 5 C16 = 02 11 304. The octal (base 8) system can also be converted with relative ease, although not quite as trivially as with bases 2 and 4. Each octal digit corresponds to three binary digits, rather than four. Therefore, we can convert between octal and hex via an intermediate conversion to binary followed by regrouping the binary digits in groups of either three or four. As with all bases there is a simple algorithm for converting a representation of a number to hex by doing integer division and remainder operations in the source base. In theory, this is possible from any base, but for most humans, only decimal and for most computers, only binary (which can be converted by far more efficient methods) can be easily handled with this method. Let d be the number to represent in hex, and the series hihi−1...h2h1 be the hex digits representing the number. "16" may be replaced with any other base that may be desired. The following is a JavaScript implementation of the above algorithm for converting any number to a hex in String representation. Its purpose is to illustrate the above algorithm. To work with data seriously, however, it is much more advisable to work with bitwise operators. It is also possible to make the conversion by assigning each place in the source base the hex representation of its place value –before carrying out multiplication and addition to get the final representation. For example, to convert the number B3AD to decimal, one can split the hex number into its digits: B (1110), 3 (310), A (1010) and D (1310), and then get the final result by multiplying each decimal representation by 16p (p being the corresponding hex digit position, counting from right to left, beginning with 0). In this case, we have that: B3AD = (11 × 163) + (3 × 162) + (10 × 161) + (13 × 160) which is 45997 in base 10. Many computer systems provide a calculator utility capable of performing conversions between the various radices frequently including hex. In Microsoft Windows, the Calculator, on its Programmer mode, allows conversions between hex and other common programming bases. Elementary arithmetic Elementary operations such as division can be carried out indirectly through conversion to an alternate numeral system, such as the commonly used decimal system or the binary system where each hex digit corresponds to four binary digits. Alternatively, one can also perform elementary operations directly within the hex system itself –by relying on its addition/multiplication tables and its corresponding standard algorithms such as long division and the traditional subtraction algorithm. Real numbers As with other numeral systems, the hex system can be used to represent rational numbers, although repeating expansions are common since sixteen (1016) has only a single prime factor: two. For any base, 0.1 (or "1/10") is always equivalent to one divided by the representation of that base value in its own number system. Thus, whether dividing one by two for binary or dividing one by sixteen for hex, both of these fractions are written as 0.1. Because the radix 16 is a perfect square (42), fractions expressed in hex have an odd period much more often than decimal ones, and there are no cyclic numbers (other than trivial single digits). Recurring digits are exhibited when the denominator in lowest terms has a prime factor not found in the radix; thus, when using hex notation, all fractions with denominators that are not a power of two result in an infinite string of recurring digits (such as thirds and fifths). This makes hex (and binary) less convenient than decimal for representing rational numbers since a larger proportion lies outside its range of finite representation. All rational numbers finitely representable in hex are also finitely representable in decimal, duodecimal and sexagesimal: that is, any hex number with a finite number of digits also has a finite number of digits when expressed in those other bases. Conversely, only a fraction of those finitely representable in the latter bases are finitely representable in hex. For example, decimal 0.1 corresponds to the infinite recurring representation 0.19 in hex. However, hex is more efficient than duodecimal and sexagesimal for representing fractions with powers of two in the denominator. For example, 0.062510 (one-sixteenth) is equivalent to 0.116, 0.0912, and 0;3,4560. The table below gives the expansions of some common irrational numbers in decimal and hex. The first 16 powers of 2 are below as hex to show relative simplicity compared to decimal representation. Cultural history The traditional Chinese units of measurement were base-16. For example, one jīn (斤) in the old system equals sixteen taels. The suanpan (Chinese abacus) can be used to perform hex calculations such as additions and subtractions. As with the duodecimal system, there have been occasional attempts to promote hex as the preferred numeral system. These attempts often propose specific pronunciation and symbols for the individual numerals. Some proposals unify standard measures so that they are multiples of 16. An early such proposal was put forward by John W. Nystrom in Project of a New System of Arithmetic, Weight, Measure and Coins: Proposed to be called the Tonal System, with Sixteen to the Base, published in 1862. Nystrom among other things suggested hexadecimal time, which subdivides a day by 16, so that there are 16 "hours" (or "10 tims", pronounced tontim) in a day. The word hexadecimal is first recorded in 1952. It is macaronic in the sense that it combines Greek ἕξ (hex) "six" with Latinate -decimal. The all-Latin alternative sexadecimal (compare the word sexagesimal for base 60) is older, and sees at least occasional use from the late 19th century. It is still in use in the 1950s in Bendix documentation. Schwartzman (1994) argues that use of sexadecimal may have been avoided because of its suggestive abbreviation to sex. Many western languages since the 1960s have adopted terms equivalent in formation to hexadecimal (e.g. French hexadécimal, Italian esadecimale, Romanian hexazecimal, Serbian хексадецимални, etc.) but others have introduced terms which substitute native words for "sixteen" (e.g. Greek δεκαεξαδικός, Icelandic sextándakerfi, Russian шестнадцатеричной etc.) Terminology and notation did not become settled until the end of the 1960s. In 1969, Donald Knuth argued that the etymologically correct term would be senidenary, or possibly sedenary, a Latinate term intended to convey "grouped by 16" modelled on binary, ternary, quaternary, etc. According to Knuth's argument, the correct terms for decimal and octal arithmetic would be denary and octonary, respectively. Alfred B. Taylor used senidenary in his mid-1800s work on alternative number bases, although he rejected base 16 because of its "incommodious number of digits". The now-current notation using the letters A to F establishes itself as the de facto standard beginning in 1966, in the wake of the publication of the Fortran IV manual for IBM System/360, which (unlike earlier variants of Fortran) recognizes a standard for entering hexadecimal constants. As noted above, alternative notations were used by NEC (1960) and The Pacific Data Systems 1020 (1964). The standard adopted by IBM seems to have become widely adopted by 1968, when Bruce Alan Martin in his letter to the editor of the CACM complains that With the ridiculous choice of letters A, B, C, D, E, F as hexadecimal number symbols adding to already troublesome problems of distinguishing octal (or hex) numbers from decimal numbers (or variable names), the time is overripe for reconsideration of our number symbols. This should have been done before poor choices gelled into a de facto standard! Martin's argument was that use of numerals 0 to 9 in nondecimal numbers "imply to us a base-ten place-value scheme": "Why not use entirely new symbols (and names) for the seven or fifteen nonzero digits needed in octal or hex. Even use of the letters A through P would be an improvement, but entirely new symbols could reflect the binary nature of the system". He also argued that "re-using alphabetic letters for numerical digits represents a gigantic backward step from the invention of distinct, non-alphabetic glyphs for numerals sixteen centuries ago" (as Brahmi numerals, and later in a Hindu–Arabic numeral system), and that the recent ASCII standards (ASA X3.4-1963 and USAS X3.4-1968) "should have preserved six code table positions following the ten decimal digits -- rather than needlessly filling these with punctuation characters" (":;<=>?") that might have been placed elsewhere among the 128 available positions. Base16 Base16 is a binary to text encoding in the family that also contains Base32, Base58, and Base64. Data is broken into 4-bit sequences, and each value (0-15) is encoded as a character. Although any 16 characters could be used, in practice, the ASCII digits "0"–"9" and letters "A"–"F" (or "a"–"f") are used to align with the typical notation for hex numbers. Support for Base16 encoding is ubiquitous in modern computing. It is the basis for the W3C standard for URL percent encoding, where a character is replaced with a percent sign "%" and its Base16-encoded form. Most modern programming languages directly include support for formatting and parsing Base16-encoded numbers. Advantages of Base16 encoding include: Disadvantages include: See also References |
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[SOURCE: https://en.wikipedia.org/wiki/Python_(programming_language)#cite_ref-DownloadOther_9-1] | [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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[SOURCE: https://en.wikipedia.org/wiki/National_camp] | [TOKENS: 525] |
Contents National camp Defunct In Israeli politics, the national camp (Hebrew: המחנה הלאומי) or right-wing bloc is an informal coalition of nationalist and right-wing, religious conservative political parties that since 1977 has frequently co-operated to form governments. The coalition is led by Likud, and includes parties to its political right as well as religious parties. Generally, the two Haredi parties (Shas and the United Torah Judaism alliance) align with Likud. In the past, the coalition has included the National Religious Party, the National Union, Gesher, Tkuma, The Jewish Home, the New Right (until 2020), Yisrael Beiteinu (until late 2019) and Zehut. Right-wing bloc Following the September 2019 Israeli legislative election, Israeli Prime Minister Benjamin Netanyahu formed a "right-wing bloc" for the purposes of coalition negotiations, consisting of Likud, Shas, United Torah Judaism and Yamina, that would support Netanyahu as Prime Minister. In February 2021, Yamina left the bloc to pursue negotiations with opposition parties, and the Religious Zionist Party, which had split from Yamina, also declined to sign on, despite supporting Netanyahu as Prime Minister. However, the Religious Zionist Party later rejoined the bloc and participated in bloc meetings. Following the fall of the Netanyahu government in June 2021, the four parties of the right-wing bloc went into the opposition, but continued to hold regular joint meetings in Netanyahu's office. The bloc returned to power under Netanyahu's leadership following the 2022 Israeli legislative election, forming the thirty-seventh government of Israel. Composition ^ a: Includes Agudat Israel and Degel HaTorah. ^ b: Merger of National Union-Tkuma and The Jewish Home. ^ c: Membership in the government currently terminated. In January 2022, Israeli Prime Minister Naftali Bennett suggested he was planning to form a "new national camp" with Yamina, Yisrael Beiteinu and New Hope, excluding Likud. The three parties parted their ways during the collapse of 36th Cabinet of Israel. In August 2024, Gideon Sa'ar, the leader of New Hope, called for the unification of what he described as the "liberal right-wing camp", which would also include Yisrael Beiteinu and Bennett's New Right. The national camp in the Knesset References This article about an Israeli political party is a stub. You can help Wikipedia by adding missing information. |
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[SOURCE: https://en.wikipedia.org/wiki/JANET] | [TOKENS: 1667] |
Contents JANET Janet is a high-speed network for the UK research and education community provided by Jisc, a not-for-profit company set up to provide computing support for education. It serves 18 million users and is the busiest National Research and Education Network in Europe by volume of data carried. Previously, Janet was a private, UK-government funded organisation, which provided the JANET computer network and related collaborative services to UK research and education. All further- and higher-education organisations in the UK are connected to the Janet network, as are all the Research Councils; the majority of these sites are connected via 20 metropolitan area networks across the UK (though Janet refers to these as regions, emphasising that Janet connections are not just confined to a metropolitan area). The network also carries traffic between schools within the UK, although many of the schools' networks maintain their own general Internet connectivity. The name was originally a contraction of Joint Academic NETwork but it is now known as Janet in its own right. The network is linked to other European and worldwide NRENs through GÉANT and peers extensively with other ISPs at Internet Exchange Points in the UK. Any other networks are reached via transit services from commercial ISPs using Janet's Peering Policy. The Janet network is operated by Jisc Services Limited, part of Jisc. Janet is also responsible for the .ac.uk domain. On 1 December 2012, Janet and Jisc Collections joined to form Jisc Collections and Janet Limited, as subsidiary organisations to Jisc. In March 2015, Jisc Collections and Janet Limited was renamed to Jisc Services Limited. Jisc Services continues to operate under the brand name of Janet, with the same remit. Janet was previously known as the JNT Association, and prior to that, UKERNA (the United Kingdom Education and Research Networking Association). History Janet developed out of academic networks built in Britain since the late 1960s. Planning for the first regional network, South West Universities Computer Network (SWUCN), centred on Bristol began in 1967 and work started in 1969. A number of national computer facilities serving the Science Research Council (SRC) community developed in the early 1970s, each with their own star network (ULCC London, UMRCC Manchester, Rutherford Appleton Laboratory). Other regional networks followed in the mid-late 1970s around Edinburgh (RCOnet), London (METROnet), the Midlands (MIDnet), and Newcastle (NUMAC - the Northern Universities Multiple Access Computer) among others such as Yorkshire and the South East. These groups of institutions pooled resources to provide better computing facilities than could be afforded individually. The star networks developed into distributed computer networks but each was based on one manufacturer's standards and were mutually incompatible and overlapping. In the early 1980s a standardisation and interconnection effort started, hosted on an expansion of the SERCnet X.25 research network.[nb 1] The JANET effort was based on the Coloured Book protocols developed by the British academic community, which provided the first complete X.25 standard, and gave the UK "several years lead over other countries". The naming scheme, JANET NRS, established "UK" as the top-level domain. Later that year, the Internet's Domain Name System adopted British researchers' recommendation to use country code top-level domains. By then, the UK had a pre-existing national standard, which was retained as the .uk Internet country-code top level domain for the United Kingdom. JANET went live on 1 April 1984, two years before the NSFNET initiated operations in the United States. It hosted about 50 sites with line speeds of 9.6 kbit/s. In the mid-80s the backbone was upgraded to 2 Mbit/s, with 64 kbit/s access links. JANET connected to NSFNET in 1989. Planning began in January 1991 for the JANET Internet Protocol Service (JIPS). It was set up as a pilot project in March 1991 to host Internet Protocol (IP) traffic on the existing network. Within eight months the IP traffic had exceeded the levels of X.25 traffic, and the IP support became official in November. JANET became, primarily, a high-speed IP network. A further upgrade in the early 1990s took the backbone to 8 Mbit/s and the access links to 2 Mbit/s, making Janet the fastest X.25 network in the world at the time. There had been some talk of moving Janet to OSI protocols in the 1990s, but changes in the networking world meant this never happened. The X.25 service was closed in August 1997. In order to address speed concerns, several hardware upgrades have been incorporated into the Janet system. In 1989 SuperJanet was proposed, to re-host JANET on a fibre optic network. Work started in late 1992, and by late 1993 the first 14 sites had migrated to the new 34 Mbit/s ATM system. SuperJanet also moved solely to IP. In 1995 SuperJanet2 started, adding 155 Mbit/s ATM backbones and a 10 Mbit/s SMDS network encompassing some of the original JANET nodes. JANET's mandate now included running metropolitan area networks centred on these sites. SuperJanet3 created new 155 Mbit/s ATM nodes to fully connect all of the major sites at London, Bristol, Manchester and Leeds, with 34 Mbit/s links to smaller sites around the country. In March 2001 SuperJanet4 was launched. The key challenges for SuperJanet4 were the need to increase network capacity and to strengthen the design and management of the JANET network to allow it to meet a similar increase in the size of its userbase. SuperJanet4 saw the implementation of a 2.5 Gbit/s core backbone from which connections to regional network points of presence were made at speeds ranging between 155 Mbit/s to 2.5 Gbit/s depending upon the size of the regional network. In 2002 the core SuperJanet4 backbone was upgraded to 10 Gbit/s. SuperJanet4 also saw an increase in the userbase of the JANET network, with the inclusion of the Further Education Community and the use of the SuperJanet4 backbone to interconnect schools' networks. The core point of presence (Backbone) sites in SuperJanet4 were Edinburgh, Glasgow, Warrington, Reading, Bristol, Portsmouth, London and Leeds. In October 2006 the SuperJanet5 project was launched after £29 million of investment. It provides a 10 Gbit/s backbone, with an upgrade path to 40 Gbit/s over the next few years. The new backbone as a result of the SuperJanet5 project is a hybrid network offering, providing both a high speed IP transit service and private bandwidth channel services provisioned over a dedicated fibre network. It is designed not only to fully accommodate the requirements of the traditional JANET user base - all research institutes, universities and further education - but also to meet the needs of a new userbase in the UK's primary and secondary schools. In April 2011 Verizon helped Janet upgrade 4 central locations to run at 100 Gbit/s bringing it to a national research and education network performance parity with Internet2 (which upgraded its backbone to 100 Gbit/s in October 2007). As of October 2011 they have over 18 million end-users. Janet6 started to go live in July 2013, and was officially launched at an event at the London Film Museum on 26 November 2013. At launch, Janet6 had an initial capacity of 2 Tbit/s. Regions The Janet network is implemented through 18 regions which connect universities, colleges and schools to the Janet network. Most regions are operated by Janet, although a few operate as independent entities working under contract. Each regional network covers a specific geographical area. As of 2014 the following regional networks are connected to Janet: Notes See also References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Elon_Musk#cite_note-319] | [TOKENS: 10515] |
Contents Elon Musk Elon Reeve Musk (/ˈiːlɒn/ EE-lon; born June 28, 1971) is a businessman and entrepreneur known for his leadership of Tesla, SpaceX, Twitter, and xAI. Musk has been the wealthiest person in the world since 2025; as of February 2026,[update] Forbes estimates his net worth to be around US$852 billion. Born into a wealthy family in Pretoria, South Africa, Musk emigrated in 1989 to Canada; he has Canadian citizenship since his mother was born there. He received bachelor's degrees in 1997 from the University of Pennsylvania before moving to California to pursue business ventures. In 1995, Musk co-founded the software company Zip2. Following its sale in 1999, he co-founded X.com, an online payment company that later merged to form PayPal, which was acquired by eBay in 2002. Musk also became an American citizen in 2002. In 2002, Musk founded the space technology company SpaceX, becoming its CEO and chief engineer; the company has since led innovations in reusable rockets and commercial spaceflight. Musk joined the automaker Tesla as an early investor in 2004 and became its CEO and product architect in 2008; it has since become a leader in electric vehicles. In 2015, he co-founded OpenAI to advance artificial intelligence (AI) research, but later left; growing discontent with the organization's direction and their leadership in the AI boom in the 2020s led him to establish xAI, which became a subsidiary of SpaceX in 2026. In 2022, he acquired the social network Twitter, implementing significant changes, and rebranding it as X in 2023. His other businesses include the neurotechnology company Neuralink, which he co-founded in 2016, and the tunneling company the Boring Company, which he founded in 2017. In November 2025, a Tesla pay package worth $1 trillion for Musk was approved, which he is to receive over 10 years if he meets specific goals. Musk was the largest donor in the 2024 U.S. presidential election, where he supported Donald Trump. After Trump was inaugurated as president in early 2025, Musk served as Senior Advisor to the President and as the de facto head of the Department of Government Efficiency (DOGE). After a public feud with Trump, Musk left the Trump administration and returned to managing his companies. Musk is a supporter of global far-right figures, causes, and political parties. His political activities, views, and statements have made him a polarizing figure. Musk has been criticized for COVID-19 misinformation, promoting conspiracy theories, and affirming antisemitic, racist, and transphobic comments. His acquisition of Twitter was controversial due to a subsequent increase in hate speech and the spread of misinformation on the service, following his pledge to decrease censorship. His role in the second Trump administration attracted public backlash, particularly in response to DOGE. The emails he sent to Jeffrey Epstein are included in the Epstein files, which were published between 2025–26 and became a topic of worldwide debate. Early life Elon Reeve Musk was born on June 28, 1971, in Pretoria, South Africa's administrative capital. He is of British and Pennsylvania Dutch ancestry. His mother, Maye (née Haldeman), is a model and dietitian born in Saskatchewan, Canada, and raised in South Africa. Musk therefore holds both South African and Canadian citizenship from birth. His father, Errol Musk, is a South African electromechanical engineer, pilot, sailor, consultant, emerald dealer, and property developer, who partly owned a rental lodge at Timbavati Private Nature Reserve. His maternal grandfather, Joshua N. Haldeman, who died in a plane crash when Elon was a toddler, was an American-born Canadian chiropractor, aviator and political activist in the technocracy movement who moved to South Africa in 1950. Elon has a younger brother, Kimbal, a younger sister, Tosca, and four paternal half-siblings. Musk was baptized as a child in the Anglican Church of Southern Africa. Despite both Elon and Errol previously stating that Errol was a part owner of a Zambian emerald mine, in 2023, Errol recounted that the deal he made was to receive "a portion of the emeralds produced at three small mines". Errol was elected to the Pretoria City Council as a representative of the anti-apartheid Progressive Party and has said that his children shared their father's dislike of apartheid. After his parents divorced in 1979, Elon, aged around 9, chose to live with his father because Errol Musk had an Encyclopædia Britannica and a computer. Elon later regretted his decision and became estranged from his father. Elon has recounted trips to a wilderness school that he described as a "paramilitary Lord of the Flies" where "bullying was a virtue" and children were encouraged to fight over rations. In one incident, after an altercation with a fellow pupil, Elon was thrown down concrete steps and beaten severely, leading to him being hospitalized for his injuries. Elon described his father berating him after he was discharged from the hospital. Errol denied berating Elon and claimed, "The [other] boy had just lost his father to suicide, and Elon had called him stupid. Elon had a tendency to call people stupid. How could I possibly blame that child?" Elon was an enthusiastic reader of books, and had attributed his success in part to having read The Lord of the Rings, the Foundation series, and The Hitchhiker's Guide to the Galaxy. At age ten, he developed an interest in computing and video games, teaching himself how to program from the VIC-20 user manual. At age twelve, Elon sold his BASIC-based game Blastar to PC and Office Technology magazine for approximately $500 (equivalent to $1,600 in 2025). Musk attended Waterkloof House Preparatory School, Bryanston High School, and then Pretoria Boys High School, where he graduated. Musk was a decent but unexceptional student, earning a 61/100 in Afrikaans and a B on his senior math certification. Musk applied for a Canadian passport through his Canadian-born mother to avoid South Africa's mandatory military service, which would have forced him to participate in the apartheid regime, as well as to ease his path to immigration to the United States. While waiting for his application to be processed, he attended the University of Pretoria for five months. Musk arrived in Canada in June 1989, connected with a second cousin in Saskatchewan, and worked odd jobs, including at a farm and a lumber mill. In 1990, he entered Queen's University in Kingston, Ontario. Two years later, he transferred to the University of Pennsylvania, where he studied until 1995. Although Musk has said that he earned his degrees in 1995, the University of Pennsylvania did not award them until 1997 – a Bachelor of Arts in physics and a Bachelor of Science in economics from the university's Wharton School. He reportedly hosted large, ticketed house parties to help pay for tuition, and wrote a business plan for an electronic book-scanning service similar to Google Books. In 1994, Musk held two internships in Silicon Valley: one at energy storage startup Pinnacle Research Institute, which investigated electrolytic supercapacitors for energy storage, and another at Palo Alto–based startup Rocket Science Games. In 1995, he was accepted to a graduate program in materials science at Stanford University, but did not enroll. Musk decided to join the Internet boom of the 1990s, applying for a job at Netscape, to which he reportedly never received a response. The Washington Post reported that Musk lacked legal authorization to remain and work in the United States after failing to enroll at Stanford. In response, Musk said he was allowed to work at that time and that his student visa transitioned to an H1-B. According to numerous former business associates and shareholders, Musk said he was on a student visa at the time. Business career In 1995, Musk, his brother Kimbal, and Greg Kouri founded the web software company Zip2 with funding from a group of angel investors. They housed the venture at a small rented office in Palo Alto. Replying to Rolling Stone, Musk denounced the notion that they started their company with funds borrowed from Errol Musk, but in a tweet, he recognized that his father contributed 10% of a later funding round. The company developed and marketed an Internet city guide for the newspaper publishing industry, with maps, directions, and yellow pages. According to Musk, "The website was up during the day and I was coding it at night, seven days a week, all the time." To impress investors, Musk built a large plastic structure around a standard computer to create the impression that Zip2 was powered by a small supercomputer. The Musk brothers obtained contracts with The New York Times and the Chicago Tribune, and persuaded the board of directors to abandon plans for a merger with CitySearch. Musk's attempts to become CEO were thwarted by the board. Compaq acquired Zip2 for $307 million in cash in February 1999 (equivalent to $590,000,000 in 2025), and Musk received $22 million (equivalent to $43,000,000 in 2025) for his 7-percent share. In 1999, Musk co-founded X.com, an online financial services and e-mail payment company. The startup was one of the first federally insured online banks, and, in its initial months of operation, over 200,000 customers joined the service. The company's investors regarded Musk as inexperienced and replaced him with Intuit CEO Bill Harris by the end of the year. The following year, X.com merged with online bank Confinity to avoid competition. Founded by Max Levchin and Peter Thiel, Confinity had its own money-transfer service, PayPal, which was more popular than X.com's service. Within the merged company, Musk returned as CEO. Musk's preference for Microsoft software over Unix created a rift in the company and caused Thiel to resign. Due to resulting technological issues and lack of a cohesive business model, the board ousted Musk and replaced him with Thiel in 2000.[b] Under Thiel, the company focused on the PayPal service and was renamed PayPal in 2001. In 2002, PayPal was acquired by eBay for $1.5 billion (equivalent to $2,700,000,000 in 2025) in stock, of which Musk—the largest shareholder with 11.72% of shares—received $175.8 million (equivalent to $320,000,000 in 2025). In 2017, Musk purchased the domain X.com from PayPal for an undisclosed amount, stating that it had sentimental value. In 2001, Musk became involved with the nonprofit Mars Society and discussed funding plans to place a growth-chamber for plants on Mars. Seeking a way to launch the greenhouse payloads into space, Musk made two unsuccessful trips to Moscow to purchase intercontinental ballistic missiles (ICBMs) from Russian companies NPO Lavochkin and Kosmotras. Musk instead decided to start a company to build affordable rockets. With $100 million of his early fortune, (equivalent to $180,000,000 in 2025) Musk founded SpaceX in May 2002 and became the company's CEO and Chief Engineer. SpaceX attempted its first launch of the Falcon 1 rocket in 2006. Although the rocket failed to reach Earth orbit, it was awarded a Commercial Orbital Transportation Services program contract from NASA, then led by Mike Griffin. After two more failed attempts that nearly caused Musk to go bankrupt, SpaceX succeeded in launching the Falcon 1 into orbit in 2008. Later that year, SpaceX received a $1.6 billion NASA contract (equivalent to $2,400,000,000 in 2025) for Falcon 9-launched Dragon spacecraft flights to the International Space Station (ISS), replacing the Space Shuttle after its 2011 retirement. In 2012, the Dragon vehicle docked with the ISS, a first for a commercial spacecraft. Working towards its goal of reusable rockets, in 2015 SpaceX successfully landed the first stage of a Falcon 9 on a land platform. Later landings were achieved on autonomous spaceport drone ships, an ocean-based recovery platform. In 2018, SpaceX launched the Falcon Heavy; the inaugural mission carried Musk's personal Tesla Roadster as a dummy payload. Since 2019, SpaceX has been developing Starship, a reusable, super heavy-lift launch vehicle intended to replace the Falcon 9 and Falcon Heavy. In 2020, SpaceX launched its first crewed flight, the Demo-2, becoming the first private company to place astronauts into orbit and dock a crewed spacecraft with the ISS. In 2024, NASA awarded SpaceX an $843 million (equivalent to $865,000,000 in 2025) contract to build a spacecraft that NASA will use to deorbit the ISS at the end of its lifespan. In 2015, SpaceX began development of the Starlink constellation of low Earth orbit satellites to provide satellite Internet access. After the launch of prototype satellites in 2018, the first large constellation was deployed in May 2019. As of May 2025[update], over 7,600 Starlink satellites are operational, comprising 65% of all operational Earth satellites. The total cost of the decade-long project to design, build, and deploy the constellation was estimated by SpaceX in 2020 to be $10 billion (equivalent to $12,000,000,000 in 2025).[c] During the Russian invasion of Ukraine, Musk provided free Starlink service to Ukraine, permitting Internet access and communication at a yearly cost to SpaceX of $400 million (equivalent to $440,000,000 in 2025). However, Musk refused to block Russian state media on Starlink. In 2023, Musk denied Ukraine's request to activate Starlink over Crimea to aid an attack against the Russian navy, citing fears of a nuclear response. Tesla, Inc., originally Tesla Motors, was incorporated in July 2003 by Martin Eberhard and Marc Tarpenning. Both men played active roles in the company's early development prior to Musk's involvement. Musk led the Series A round of investment in February 2004; he invested $6.35 million (equivalent to $11,000,000 in 2025), became the majority shareholder, and joined Tesla's board of directors as chairman. Musk took an active role within the company and oversaw Roadster product design, but was not deeply involved in day-to-day business operations. Following a series of escalating conflicts in 2007 and the 2008 financial crisis, Eberhard was ousted from the firm.[page needed] Musk assumed leadership of the company as CEO and product architect in 2008. A 2009 lawsuit settlement with Eberhard designated Musk as a Tesla co-founder, along with Tarpenning and two others. Tesla began delivery of the Roadster, an electric sports car, in 2008. With sales of about 2,500 vehicles, it was the first mass production all-electric car to use lithium-ion battery cells. Under Musk, Tesla has since launched several well-selling electric vehicles, including the four-door sedan Model S (2012), the crossover Model X (2015), the mass-market sedan Model 3 (2017), the crossover Model Y (2020), and the pickup truck Cybertruck (2023). In May 2020, Musk resigned as chairman of the board as part of the settlement of a lawsuit from the SEC over him tweeting that funding had been "secured" for potentially taking Tesla private. The company has also constructed multiple lithium-ion battery and electric vehicle factories, called Gigafactories. Since its initial public offering in 2010, Tesla stock has risen significantly; it became the most valuable carmaker in summer 2020, and it entered the S&P 500 later that year. In October 2021, it reached a market capitalization of $1 trillion (equivalent to $1,200,000,000,000 in 2025), the sixth company in U.S. history to do so. Musk provided the initial concept and financial capital for SolarCity, which his cousins Lyndon and Peter Rive founded in 2006. By 2013, SolarCity was the second largest provider of solar power systems in the United States. In 2014, Musk promoted the idea of SolarCity building an advanced production facility in Buffalo, New York, triple the size of the largest solar plant in the United States. Construction of the factory started in 2014 and was completed in 2017. It operated as a joint venture with Panasonic until early 2020. Tesla acquired SolarCity for $2 billion in 2016 (equivalent to $2,700,000,000 in 2025) and merged it with its battery unit to create Tesla Energy. The deal's announcement resulted in a more than 10% drop in Tesla's stock price; at the time, SolarCity was facing liquidity issues. Multiple shareholder groups filed a lawsuit against Musk and Tesla's directors, stating that the purchase of SolarCity was done solely to benefit Musk and came at the expense of Tesla and its shareholders. Tesla directors settled the lawsuit in January 2020, leaving Musk the sole remaining defendant. Two years later, the court ruled in Musk's favor. In 2016, Musk co-founded Neuralink, a neurotechnology startup, with an investment of $100 million. Neuralink aims to integrate the human brain with artificial intelligence (AI) by creating devices that are embedded in the brain. Such technology could enhance memory or allow the devices to communicate with software. The company also hopes to develop devices to treat neurological conditions like spinal cord injuries. In 2022, Neuralink announced that clinical trials would begin by the end of the year. In September 2023, the Food and Drug Administration approved Neuralink to initiate six-year human trials. Neuralink has conducted animal testing on macaques at the University of California, Davis. In 2021, the company released a video in which a macaque played the video game Pong via a Neuralink implant. The company's animal trials—which have caused the deaths of some monkeys—have led to claims of animal cruelty. The Physicians Committee for Responsible Medicine has alleged that Neuralink violated the Animal Welfare Act. Employees have complained that pressure from Musk to accelerate development has led to botched experiments and unnecessary animal deaths. In 2022, a federal probe was launched into possible animal welfare violations by Neuralink.[needs update] In 2017, Musk founded the Boring Company to construct tunnels; he also revealed plans for specialized, underground, high-occupancy vehicles that could travel up to 150 miles per hour (240 km/h) and thus circumvent above-ground traffic in major cities. Early in 2017, the company began discussions with regulatory bodies and initiated construction of a 30-foot (9.1 m) wide, 50-foot (15 m) long, and 15-foot (4.6 m) deep "test trench" on the premises of SpaceX's offices, as that required no permits. The Los Angeles tunnel, less than two miles (3.2 km) in length, debuted to journalists in 2018. It used Tesla Model Xs and was reported to be a rough ride while traveling at suboptimal speeds. Two tunnel projects announced in 2018, in Chicago and West Los Angeles, have been canceled. A tunnel beneath the Las Vegas Convention Center was completed in early 2021. Local officials have approved further expansions of the tunnel system. April 14, 2022 In early 2017, Musk expressed interest in buying Twitter and had questioned the platform's commitment to freedom of speech. By 2022, Musk had reached 9.2% stake in the company, making him the largest shareholder.[d] Musk later agreed to a deal that would appoint him to Twitter's board of directors and prohibit him from acquiring more than 14.9% of the company. Days later, Musk made a $43 billion offer to buy Twitter. By the end of April Musk had successfully concluded his bid for approximately $44 billion. This included approximately $12.5 billion in loans and $21 billion in equity financing. Having backtracked on his initial decision, Musk bought the company on October 27, 2022. Immediately after the acquisition, Musk fired several top Twitter executives including CEO Parag Agrawal; Musk became the CEO instead. Under Elon Musk, Twitter instituted monthly subscriptions for a "blue check", and laid off a significant portion of the company's staff. Musk lessened content moderation and hate speech also increased on the platform after his takeover. In late 2022, Musk released internal documents relating to Twitter's moderation of Hunter Biden's laptop controversy in the lead-up to the 2020 presidential election. Musk also promised to step down as CEO after a Twitter poll, and five months later, Musk stepped down as CEO and transitioned his role to executive chairman and chief technology officer (CTO). Despite Musk stepping down as CEO, X continues to struggle with challenges such as viral misinformation, hate speech, and antisemitism controversies. Musk has been accused of trying to silence some of his critics such as Twitch streamer Asmongold, who criticized him during one of his streams. Musk has been accused of removing their accounts' blue checkmarks, which hinders visibility and is considered a form of shadow banning, or suspending their accounts without justification. Other activities In August 2013, Musk announced plans for a version of a vactrain, and assigned engineers from SpaceX and Tesla to design a transport system between Greater Los Angeles and the San Francisco Bay Area, at an estimated cost of $6 billion. Later that year, Musk unveiled the concept, dubbed the Hyperloop, intended to make travel cheaper than any other mode of transport for such long distances. In December 2015, Musk co-founded OpenAI, a not-for-profit artificial intelligence (AI) research company aiming to develop artificial general intelligence, intended to be safe and beneficial to humanity. Musk pledged $1 billion of funding to the company, and initially gave $50 million. In 2018, Musk left the OpenAI board. Since 2018, OpenAI has made significant advances in machine learning. In July 2023, Musk launched the artificial intelligence company xAI, which aims to develop a generative AI program that competes with existing offerings like OpenAI's ChatGPT. Musk obtained funding from investors in SpaceX and Tesla, and xAI hired engineers from Google and OpenAI. December 16, 2022 Musk uses a private jet owned by Falcon Landing LLC, a SpaceX-linked company, and acquired a second jet in August 2020. His heavy use of the jets and the consequent fossil fuel usage have received criticism. Musk's flight usage is tracked on social media through ElonJet. In December 2022, Musk banned the ElonJet account on Twitter, and made temporary bans on the accounts of journalists that posted stories regarding the incident, including Donie O'Sullivan, Keith Olbermann, and journalists from The New York Times, The Washington Post, CNN, and The Intercept. In October 2025, Musk's company xAI launched Grokipedia, an AI-generated online encyclopedia that he promoted as an alternative to Wikipedia. Articles on Grokipedia are generated and reviewed by xAI's Grok chatbot. Media coverage and academic analysis described Grokipedia as frequently reusing Wikipedia content but framing contested political and social topics in line with Musk's own views and right-wing narratives. A study by Cornell University researchers and NBC News stated that Grokipedia cites sources that are blacklisted or considered "generally unreliable" on Wikipedia, for example, the conspiracy site Infowars and the neo-Nazi forum Stormfront. Wired, The Guardian and Time criticized Grokipedia for factual errors and for presenting Musk himself in unusually positive terms while downplaying controversies. Politics Musk is an outlier among business leaders who typically avoid partisan political advocacy. Musk was a registered independent voter when he lived in California. Historically, he has donated to both Democrats and Republicans, many of whom serve in states in which he has a vested interest. Since 2022, his political contributions have mostly supported Republicans, with his first vote for a Republican going to Mayra Flores in the 2022 Texas's 34th congressional district special election. In 2024, he started supporting international far-right political parties, activists, and causes, and has shared misinformation and numerous conspiracy theories. Since 2024, his views have been generally described as right-wing. Musk supported Barack Obama in 2008 and 2012, Hillary Clinton in 2016, Joe Biden in 2020, and Donald Trump in 2024. In the 2020 Democratic Party presidential primaries, Musk endorsed candidate Andrew Yang and expressed support for Yang's proposed universal basic income, and endorsed Kanye West's 2020 presidential campaign. In 2021, Musk publicly expressed opposition to the Build Back Better Act, a $3.5 trillion legislative package endorsed by Joe Biden that ultimately failed to pass due to unanimous opposition from congressional Republicans and several Democrats. In 2022, gave over $50 million to Citizens for Sanity, a conservative political action committee. In 2023, he supported Republican Ron DeSantis for the 2024 U.S. presidential election, giving $10 million to his campaign, and hosted DeSantis's campaign announcement on a Twitter Spaces event. From June 2023 to January 2024, Musk hosted a bipartisan set of X Spaces with Republican and Democratic candidates, including Robert F. Kennedy Jr., Vivek Ramaswamy, and Dean Phillips. In October 2025, former vice-president Kamala Harris commented that it was a mistake from the Democratic side to not invite Musk to a White House electric vehicle event organized in August 2021 and featuring executives from General Motors, Ford and Stellantis, despite Tesla being "the major American manufacturer of extraordinary innovation in this space." Fortune remarked that this was a nod to United Auto Workers and organized labor. Harris said presidents should put aside political loyalties when it came to recognizing innovation, and guessed that the non-invitation impacted Musk's perspective. Fortune noted that, at the time, Musk said, "Yeah, seems odd that Tesla wasn't invited." A month later, he criticized Biden as "not the friendliest administration." Jacob Silverman, author of the book Gilded Rage: Elon Musk and the Radicalization of Silicon Valley, said that the tech industry represented by Musk, Thiel, Andreessen and other capitalists, actually flourished under Biden, but the tech leaders chose Trump for their common ground on cultural issues. By early 2024, Musk had become a vocal and financial supporter of Donald Trump. In July 2024, minutes after the attempted assassination of Donald Trump, Musk endorsed him for president saying; "I fully endorse President Trump and hope for his rapid recovery." During the presidential campaign, Musk joined Trump on stage at a campaign rally, and during the campaign promoted conspiracy theories and falsehoods about Democrats, election fraud and immigration, in support of Trump. Musk was the largest individual donor of the 2024 election. In 2025, Musk contributed $19 million to the Wisconsin Supreme Court race, hoping to influence the state's future redistricting efforts and its regulations governing car manufacturers and dealers. In 2023, Musk said he shunned the World Economic Forum because it was boring. The organization commented that they had not invited him since 2015. He has participated in Dialog, dubbed "Tech Bilderberg" and organized by Peter Thiel and Auren Hoffman, though. Musk's international political actions and comments have come under increasing scrutiny and criticism, especially from the governments and leaders of France, Germany, Norway, Spain and the United Kingdom, particularly due to his position in the U.S. government as well as ownership of X. An NBC News analysis found he had boosted far-right political movements to cut immigration and curtail regulation of business in at least 18 countries on six continents since 2023. During his speech after the second inauguration of Donald Trump, Musk twice made a gesture interpreted by many as a Nazi or a fascist Roman salute.[e] He thumped his right hand over his heart, fingers spread wide, and then extended his right arm out, emphatically, at an upward angle, palm down and fingers together. He then repeated the gesture to the crowd behind him. As he finished the gestures, he said to the crowd, "My heart goes out to you. It is thanks to you that the future of civilization is assured." It was widely condemned as an intentional Nazi salute in Germany, where making such gestures is illegal. The Anti-Defamation League said it was not a Nazi salute, but other Jewish organizations disagreed and condemned the salute. American public opinion was divided on partisan lines as to whether it was a fascist salute. Musk dismissed the accusations of Nazi sympathies, deriding them as "dirty tricks" and a "tired" attack. Neo-Nazi and white supremacist groups celebrated it as a Nazi salute. Multiple European political parties demanded that Musk be banned from entering their countries. The concept of DOGE emerged in a discussion between Musk and Donald Trump, and in August 2024, Trump committed to giving Musk an advisory role, with Musk accepting the offer. In November and December 2024, Musk suggested that the organization could help to cut the U.S. federal budget, consolidate the number of federal agencies, and eliminate the Consumer Financial Protection Bureau, and that its final stage would be "deleting itself". In January 2025, the organization was created by executive order, and Musk was designated a "special government employee". Musk led the organization and was a senior advisor to the president, although his official role is not clear. In sworn statement during a lawsuit, the director of the White House Office of Administration stated that Musk "is not an employee of the U.S. DOGE Service or U.S. DOGE Service Temporary Organization", "is not the U.S. DOGE Service administrator", and has "no actual or formal authority to make government decisions himself". Trump said two days later that he had put Musk in charge of DOGE. A federal judge has ruled that Musk acted as the de facto leader of DOGE. Musk's role in the second Trump administration, particularly in response to DOGE, has attracted public backlash. He was criticized for his treatment of federal government employees, including his influence over the mass layoffs of the federal workforce. He has prioritized secrecy within the organization and has accused others of violating privacy laws. A Senate report alleged that Musk could avoid up to $2 billion in legal liability as a result of DOGE's actions. In May 2025, Bill Gates accused Musk of "killing the world's poorest children" through his cuts to USAID, which modeling by Boston University estimated had resulted in 300,000 deaths by this time, most of them of children. By November 2025, the estimated death toll had increased to 400,000 children and 200,000 adults. Musk announced on May 28, 2025, that he would depart from the Trump administration as planned when the special government employee's 130 day deadline expired, with a White House official confirming that Musk's offboarding from the Trump administration was already underway. His departure was officially confirmed during a joint Oval Office press conference with Trump on May 30, 2025. @realDonaldTrump is in the Epstein files. That is the real reason they have not been made public. June 5, 2025 After leaving office, Musk criticized the Trump administration's Big Beautiful Bill, calling it a "disgusting abomination" due to its provisions increasing the deficit. A feud began between Musk and Trump, with its most notable event being Musk alleging Trump had ties to sex offender Jeffrey Epstein on X (formerly Twitter) on June 5, 2025. Trump responded on Truth Social stating that Musk went "CRAZY" after the "EV Mandate" was purportedly taken away and threatened to cut Musk's government contracts. Musk then called for a third Trump impeachment. The next day, Trump stated that he did not wish to reconcile with Musk, and added that Musk would face "very serious consequences" if he funds Democratic candidates. On June 11, Musk publicly apologized for the tweets against Trump, saying they "went too far". Views November 6, 2022 Rejecting the conservative label, Musk has described himself as a political moderate, even as his views have become more right-wing over time. His views have been characterized as libertarian and far-right, and after his involvement in European politics, they have received criticism from world leaders such as Emmanuel Macron and Olaf Scholz. Within the context of American politics, Musk supported Democratic candidates up until 2022, at which point he voted for a Republican for the first time. He has stated support for universal basic income, gun rights, freedom of speech, a tax on carbon emissions, and H-1B visas. Musk has expressed concern about issues such as artificial intelligence (AI) and climate change, and has been a critic of wealth tax, short-selling, and government subsidies. An immigrant himself, Musk has been accused of being anti-immigration, and regularly blames immigration policies for illegal immigration. He is also a pronatalist who believes population decline is the biggest threat to civilization, and identifies as a cultural Christian. Musk has long been an advocate for space colonization, especially the colonization of Mars. He has repeatedly pushed for humanity colonizing Mars, in order to become an interplanetary species and lower the risks of human extinction. Musk has promoted conspiracy theories and made controversial statements that have led to accusations of racism, sexism, antisemitism, transphobia, disseminating disinformation, and support of white pride. While describing himself as a "pro-Semite", his comments regarding George Soros and Jewish communities have been condemned by the Anti-Defamation League and the Biden White House. Musk was criticized during the COVID-19 pandemic for making unfounded epidemiological claims, defying COVID-19 lockdowns restrictions, and supporting the Canada convoy protest against vaccine mandates. He has amplified false claims of white genocide in South Africa. Musk has been critical of Israel's actions in the Gaza Strip during the Gaza war, praised China's economic and climate goals, suggested that Taiwan and China should resolve cross-strait relations, and was described as having a close relationship with the Chinese government. In Europe, Musk expressed support for Ukraine in 2022 during the Russian invasion, recommended referendums and peace deals on the annexed Russia-occupied territories, and supported the far-right Alternative for Germany political party in 2024. Regarding British politics, Musk blamed the 2024 UK riots on mass migration and open borders, criticized Prime Minister Keir Starmer for what he described as a "two-tier" policing system, and was subsequently attacked as being responsible for spreading misinformation and amplifying the far-right. He has also voiced his support for far-right activist Tommy Robinson and pledged electoral support for Reform UK. In February 2026, Musk described Spanish Prime Minister Pedro Sánchez as a "tyrant" following Sánchez's proposal to prohibit minors under the age of 16 from accessing social media platforms. Legal affairs In 2018, Musk was sued by the U.S. Securities and Exchange Commission (SEC) for a tweet stating that funding had been secured for potentially taking Tesla private.[f] The securities fraud lawsuit characterized the tweet as false, misleading, and damaging to investors, and sought to bar Musk from serving as CEO of publicly traded companies. Two days later, Musk settled with the SEC, without admitting or denying the SEC's allegations. As a result, Musk and Tesla were fined $20 million each, and Musk was forced to step down for three years as Tesla chairman but was able to remain as CEO. Shareholders filed a lawsuit over the tweet, and in February 2023, a jury found Musk and Tesla not liable. Musk has stated in interviews that he does not regret posting the tweet that triggered the SEC investigation. In 2019, Musk stated in a tweet that Tesla would build half a million cars that year. The SEC reacted by asking a court to hold him in contempt for violating the terms of the 2018 settlement agreement. A joint agreement between Musk and the SEC eventually clarified the previous agreement details, including a list of topics about which Musk needed preclearance. In 2020, a judge blocked a lawsuit that claimed a tweet by Musk regarding Tesla stock price ("too high imo") violated the agreement. Freedom of Information Act (FOIA)-released records showed that the SEC concluded Musk had subsequently violated the agreement twice by tweeting regarding "Tesla's solar roof production volumes and its stock price". In October 2023, the SEC sued Musk over his refusal to testify a third time in an investigation into whether he violated federal law by purchasing Twitter stock in 2022. In February 2024, Judge Laurel Beeler ruled that Musk must testify again. In January 2025, the SEC filed a lawsuit against Musk for securities violations related to his purchase of Twitter. In January 2024, Delaware judge Kathaleen McCormick ruled in a 2018 lawsuit that Musk's $55 billion pay package from Tesla be rescinded. McCormick called the compensation granted by the company's board "an unfathomable sum" that was unfair to shareholders. The Delaware Supreme Court overturned McCormick's decision in December 2025, restoring Musk's compensation package and awarding $1 in nominal damages. Personal life Musk became a U.S. citizen in 2002. From the early 2000s until late 2020, Musk resided in California, where both Tesla and SpaceX were founded. He then relocated to Cameron County, Texas, saying that California had become "complacent" about its economic success. While hosting Saturday Night Live in 2021, Musk stated that he has Asperger syndrome (an outdated term for autism spectrum disorder). When asked about his experience growing up with Asperger's syndrome in a TED2022 conference in Vancouver, Musk stated that "the social cues were not intuitive ... I would just tend to take things very literally ... but then that turned out to be wrong — [people were not] simply saying exactly what they mean, there's all sorts of other things that are meant, and [it] took me a while to figure that out." Musk suffers from back pain and has undergone several spine-related surgeries, including a disc replacement. In 2000, he contracted a severe case of malaria while on vacation in South Africa. Musk has stated he uses doctor-prescribed ketamine for occasional depression and that he doses "a small amount once every other week or something like that"; since January 2024, some media outlets have reported that he takes ketamine, marijuana, LSD, ecstasy, mushrooms, cocaine and other drugs. Musk at first refused to comment on his alleged drug use, before responding that he had not tested positive for drugs, and that if drugs somehow improved his productivity, "I would definitely take them!". The New York Times' investigations revealed Musk's overuse of ketamine and numerous other drugs, as well as strained family relationships and concerns from close associates who have become troubled by his public behavior as he became more involved in political activities and government work. According to The Washington Post, President Trump described Musk as "a big-time drug addict". Through his own label Emo G Records, Musk released a rap track, "RIP Harambe", on SoundCloud in March 2019. The following year, he released an EDM track, "Don't Doubt Ur Vibe", featuring his own lyrics and vocals. Musk plays video games, which he stated has a "'restoring effect' that helps his 'mental calibration'". Some games he plays include Quake, Diablo IV, Elden Ring, and Polytopia. Musk once claimed to be one of the world's top video game players but has since admitted to "account boosting", or cheating by hiring outside services to achieve top player rankings. Musk has justified the boosting by claiming that all top accounts do it so he has to as well to remain competitive. In 2024 and 2025, Musk criticized the video game Assassin's Creed Shadows and its creator Ubisoft for "woke" content. Musk posted to X that "DEI kills art" and specified the inclusion of the historical figure Yasuke in the Assassin's Creed game as offensive; he also called the game "terrible". Ubisoft responded by saying that Musk's comments were "just feeding hatred" and that they were focused on producing a game not pushing politics. Musk has fathered at least 14 children, one of whom died as an infant. The Wall Street Journal reported in 2025 that sources close to Musk suggest that the "true number of Musk's children is much higher than publicly known". He had six children with his first wife, Canadian author Justine Wilson, whom he met while attending Queen's University in Ontario, Canada; they married in 2000. In 2002, their first child Nevada Musk died of sudden infant death syndrome at the age of 10 weeks. After his death, the couple used in vitro fertilization (IVF) to continue their family; they had twins in 2004, followed by triplets in 2006. The couple divorced in 2008 and have shared custody of their children. The elder twin he had with Wilson came out as a trans woman and, in 2022, officially changed her name to Vivian Jenna Wilson, adopting her mother's surname because she no longer wished to be associated with Musk. Musk began dating English actress Talulah Riley in 2008. They married two years later at Dornoch Cathedral in Scotland. In 2012, the couple divorced, then remarried the following year. After briefly filing for divorce in 2014, Musk finalized a second divorce from Riley in 2016. Musk then dated the American actress Amber Heard for several months in 2017; he had reportedly been "pursuing" her since 2012. In 2018, Musk and Canadian musician Grimes confirmed they were dating. Grimes and Musk have three children, born in 2020, 2021, and 2022.[g] Musk and Grimes originally gave their eldest child the name "X Æ A-12", which would have violated California regulations as it contained characters that are not in the modern English alphabet; the names registered on the birth certificate are "X" as a first name, "Æ A-Xii" as a middle name, and "Musk" as a last name. They received criticism for choosing a name perceived to be impractical and difficult to pronounce; Musk has said the intended pronunciation is "X Ash A Twelve". Their second child was born via surrogacy. Despite the pregnancy, Musk confirmed reports that the couple were "semi-separated" in September 2021; in an interview with Time in December 2021, he said he was single. In October 2023, Grimes sued Musk over parental rights and custody of X Æ A-Xii. Elon Musk has taken X Æ A-Xii to multiple official events in Washington, D.C. during Trump's second term in office. Also in July 2022, The Wall Street Journal reported that Musk allegedly had an affair with Nicole Shanahan, the wife of Google co-founder Sergey Brin, in 2021, leading to their divorce the following year. Musk denied the report. Musk also had a relationship with Australian actress Natasha Bassett, who has been described as "an occasional girlfriend". In October 2024, The New York Times reported Musk bought a Texas compound for his children and their mothers, though Musk denied having done so. Musk also has four children with Shivon Zilis, director of operations and special projects at Neuralink: twins born via IVF in 2021, a child born in 2024 via surrogacy and a child born in 2025.[h] On February 14, 2025, Ashley St. Clair, an influencer and author, posted on X claiming to have given birth to Musk's son Romulus five months earlier, which media outlets reported as Musk's supposed thirteenth child.[i] On February 22, 2025, it was reported that St Clair had filed for sole custody of her five-month-old son and for Musk to be recognised as the child's father. On March 31, 2025, Musk wrote that, while he was unsure if he was the father of St. Clair's child, he had paid St. Clair $2.5 million and would continue paying her $500,000 per year.[j] Later reporting from the Wall Street Journal indicated that $1 million of these payments to St. Clair were structured as a loan. In 2014, Musk and Ghislaine Maxwell appeared together in a photograph taken at an Academy Awards after-party, which Musk later described as a "photobomb". The January 2026 Epstein files contain emails between Musk and Epstein from 2012 to 2013, after Epstein's first conviction. Emails released on January 30, 2026, indicated that Epstein invited Musk to visit his private island on multiple occasions. The correspondence showed that while Epstein repeatedly encouraged Musk to attend, Musk did not visit the island. In one instance, Musk discussed the possibility of attending a party with his then-wife Talulah Riley and asked which day would be the "wildest party"; according to the emails, the visit did not take place after Epstein later cancelled the plans.[k] On Christmas day in 2012, Musk emailed Epstein asking "Do you have any parties planned? I’ve been working to the edge of sanity this year and so, once my kids head home after Christmas, I really want to hit the party scene in St Barts or elsewhere and let loose. The invitation is much appreciated, but a peaceful island experience is the opposite of what I’m looking for". Epstein replied that the "ratio on my island" might make Musk's wife uncomfortable to which Musk responded, "Ratio is not a problem for Talulah". On September 11, 2013, Epstein sent an email asking Musk if he had any plans for coming to New York for the opening of the United Nations General Assembly where many "interesting people" would be coming to his house to which Musk responded that "Flying to NY to see UN diplomats do nothing would be an unwise use of time". Epstein responded by stating "Do you think i am retarded. Just kidding, there is no one over 25 and all very cute." Musk has denied any close relationship with Epstein and described him as a "creep" who attempted to ingratiate himself with influential people. When Musk was asked in 2019 if he introduced Epstein to Mark Zuckerberg, Musk responded: "I don’t recall introducing Epstein to anyone, as I don’t know the guy well enough to do so." The released emails nonetheless showed cordial exchanges on a range of topics, including Musk's inquiry about parties on the island. The correspondence also indicated that Musk suggested hosting Epstein at SpaceX, while Epstein separately discussed plans to tour SpaceX and bring "the girls", though there is no evidence that such a visit occurred. Musk has described the release of the files a "distraction", later accusing the second Trump administration of suppressing them to protect powerful individuals, including Trump himself.[l] Wealth Elon Musk is the wealthiest person in the world, with an estimated net worth of US$690 billion as of January 2026, according to the Bloomberg Billionaires Index, and $852 billion according to Forbes, primarily from his ownership stakes in SpaceX and Tesla. Having been first listed on the Forbes Billionaires List in 2012, around 75% of Musk's wealth was derived from Tesla stock in November 2020, although he describes himself as "cash poor". According to Forbes, he became the first person in the world to achieve a net worth of $300 billion in 2021; $400 billion in December 2024; $500 billion in October 2025; $600 billion in mid-December 2025; $700 billion later that month; and $800 billion in February 2026. In November 2025, a Tesla pay package worth potentially $1 trillion for Musk was approved, which he is to receive over 10 years if he meets specific goals. Public image Although his ventures have been highly influential within their separate industries starting in the 2000s, Musk only became a public figure in the early 2010s. He has been described as an eccentric who makes spontaneous and impactful decisions, while also often making controversial statements, contrary to other billionaires who prefer reclusiveness to protect their businesses. Musk's actions and his expressed views have made him a polarizing figure. Biographer Ashlee Vance described people's opinions of Musk as polarized due to his "part philosopher, part troll" persona on Twitter. He has drawn denouncement for using his platform to mock the self-selection of personal pronouns, while also receiving praise for bringing international attention to matters like British survivors of grooming gangs. Musk has been described as an American oligarch due to his extensive influence over public discourse, social media, industry, politics, and government policy. After Trump's re-election, Musk's influence and actions during the transition period and the second presidency of Donald Trump led some to call him "President Musk", the "actual president-elect", "shadow president" or "co-president". Awards for his contributions to the development of the Falcon rockets include the American Institute of Aeronautics and Astronautics George Low Transportation Award in 2008, the Fédération Aéronautique Internationale Gold Space Medal in 2010, and the Royal Aeronautical Society Gold Medal in 2012. In 2015, he received an honorary doctorate in engineering and technology from Yale University and an Institute of Electrical and Electronics Engineers Honorary Membership. Musk was elected a Fellow of the Royal Society (FRS) in 2018.[m] In 2022, Musk was elected to the National Academy of Engineering. Time has listed Musk as one of the most influential people in the world in 2010, 2013, 2018, and 2021. Musk was selected as Time's "Person of the Year" for 2021. Then Time editor-in-chief Edward Felsenthal wrote that, "Person of the Year is a marker of influence, and few individuals have had more influence than Musk on life on Earth, and potentially life off Earth too." Notes References Works cited Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/Judah_(Bible)] | [TOKENS: 3788] |
Contents Judah (son of Jacob) Judah (Hebrew: יְהוּדָה, Modern: Yəhūda, Tiberian: Yŭhūḏā) was, according to the Book of Genesis, the fourth of the six sons of Jacob and Leah and the founder of the Tribe of Judah of the Israelites. By extension, he is indirectly the eponym of the Kingdom of Judah, the land of Judea, and the word Jew. According to the narrative in Genesis, Judah alongside Tamar is a patrilineal ancestor of the Davidic line. The Tribe of Judah features prominently in Deuteronomistic history, which most scholars agree was reduced to written form, although subject to exilic and post-exilic alterations and emendations, during the reign of the Judahist reformer Josiah from 641 to 609 BCE. Etymology The Hebrew name for Judah, Yehuda (יהודה), literally "thanksgiving" or "praise," is the noun form of the root Y-H-D (יהד), "to thank" or "to praise." His birth is recorded at Gen. 29:35; upon his birth, Leah exclaims, "This time I will praise the LORD/YHWH," with the Hebrew word for "I will praise," odeh (אודה) sharing the same root as Yehuda. Alternatively, Edward Lipiński connected Hebrew yĕhūdā with Arabic whd / wahda "cleft, ravine". Biblical references Judah is the fourth son of the patriarch Jacob and his first wife, Leah: his full brothers are Reuben, Simeon and Levi (all older), and Issachar and Zebulun (younger), and he has one full sister, Dinah. Through his father, he also has six half-brothers: Dan and Naphtali (whose mother is Bilhah), Gad and Asher (whose mother is Zilpah), and Joseph and Benjamin (whose mother is Rachel). Following his birth, Judah's next appearance is in Gen 37, when he and his brothers cast Joseph into a pit out of jealousy after Joseph approaches them, flaunting a coat of many colors, while they are working in the field. It is Judah who spots a caravan of Ishmaelites coming towards them on its way to Egypt and suggests that Joseph be sold to the Ishmaelites rather than killed, after his brother Reuben suggests they do not kill him to begin with. (Gen. 37:26-28, "What profit is it if we slay our brother and conceal his blood? ... Let not our hand be upon him, for he is our brother, our flesh.") Judah marries the daughter of Shuah, a Canaanite. In Genesis chapter 38, Judah and his wife have three children, Er, Onan, and Shelah. Er marries Tamar, but God kills him because he was wicked in His sight (Gen. 38:7). Tamar becomes Onan's wife in accordance with custom, but he too is killed after he refuses to father children for his older brother's childless widow, and spills his seed instead. Although Tamar should have married Shelah, the remaining brother, Judah did not consent, and in response Tamar deceives Judah into having intercourse with her by pretending to be a prostitute. When Judah discovers that Tamar is pregnant he prepares to have her killed, but recants and confesses when he finds out that he is the father (Gen. 38:24-26). Tamar is the mother of twins, Perez (Peretz) and Zerah (Gen. 38:27-30). The former is the patrilinear ancestor of the messiah, according to the Book of Ruth (4:18-22). Meanwhile, Joseph rises to a position of power in Egypt. Twenty years after being betrayed, he meets his brothers again without them recognizing him. The youngest brother, Benjamin, had remained in Canaan with Jacob, so Joseph takes Simeon hostage and insists that the brothers return with Benjamin. Judah offers himself to Jacob as surety for Benjamin's safety, and manages to persuade Jacob to let them take Benjamin to Egypt. When the brothers return, Joseph tests them by demanding the enslavement of Benjamin. Judah pleads for Benjamin's life, and Joseph reveals his true identity. Before he dies, Jacob blesses Judah as his lead heir, stating that his other sons "shall bow down before you" and that he shall hold "the ruler's staff." Textual criticism Literary critics have focused on the relationship between the Judah story in chapter 38, and the Joseph story in chapters 37 and 39. Victor Hamilton notes some "intentional literary parallels" between the chapters, such as the exhortation to "identify" (38:25-26 and 37:32-33). J. A. Emerton, Regius Professor of Hebrew at the University of Cambridge, regards the connections as evidence for including chapter 38 in the J corpus, and suggests that the J writer dovetailed the Joseph and Judah traditions. Derek Kidner points out that the insertion of chapter 38 "creates suspense for the reader", but Robert Alter goes further and suggests it is a result of the "brilliant splicing of sources by a literary artist". He notes that the same verb identify will play "a crucial thematic role in the dénouement of the Joseph story when he confronts his brothers in Egypt, he recognizing them, they failing to recognize him". Similarly, J. P. Fokkelman notes that the "extra attention" for Judah in chapter 38, "sets him up for his major role as the brothers' spokesman in Genesis 44". Other than Joseph (and perhaps Benjamin), Judah receives the most favorable treatment in Genesis among Jacob's sons, which according to biblical historians is a reflection on the historical primacy that the tribe of Judah possessed throughout much of Israel's history, including as the source of the Davidic line. Although Judah is only the fourth son of Leah, he is expressly depicted in Genesis as assuming a leadership role among the 10 eldest brothers, including speaking up against killing Joseph, negotiating with his father regarding Joseph's demand that Benjamin be brought down to Egypt, and pleading with Joseph after the latter secrets the silver cup into Benjamin's bag. Judah's position is further enhanced through the downfall of his older brothers: Reuben, the eldest, cedes his birthright through sexual misconduct with Jacob's concubine Bilhah (Gen. 35:22), and the bloody revenge taken by Simeon and Levi following the rape of Dinah (Gen. chap. 34) disqualifies them as leaders. The eternal legacy of these events are foreshadowed in the deathbed blessing of Jacob (Gen. 49:1-33), which has been attributed according to the documentary hypothesis to the pro-Judah Yahwist source. In Jacob's blessing, Reuben has "not the excellency" to lead "because thou went up to thy father's bed, then defiled [it]"; meanwhile, Simeon and Levi are condemned as "cruel" and "weapons of violence [are] their kinship." (Gen. 49.:3-7.) On the other hand, Judah is praised as "a lion's whelp" whose brothers "shall bow down before thee", and "the sceptre shall not depart from Judah" (Genesis 49:10), the latter a clear reference to the aspirations of the united monarchy. Hebraist Gary Rendsburg argues that the original Biblical audience would have noticed the parallels between Judah and Tamar on the one hand and David and Bathsheba on the other. In particular, Rendsburg notes the similarity between Bathsheba (בַּת-שֱבַע, bat-šɛbaʿ, ‘Bathsheba) and Judah's wife the daughter of Shua', whose name is not given (בַּת-שוּעַ, bat…šua, the daughter of … Shua). Archaeologist and scholar Israel Finkelstein argues that these and other pro-Judah narrative strands likely originated after the demise of the Kingdom of Israel in the eighth century BCE: "[I]t was only after the fall of Israel that Judah grew into a fully developed state with the necessary complement of professional priests and trained scribes able to undertake such a task. When Judah suddenly faced the non-Israelite world on its own, it needed a defining and motivating text. That text was the historical core of the Bible, composed in Jerusalem in the course of the seventh century BCE. And because Judah was the birthplace of ancient Israel's central scripture, it is hardly surprising that the biblical text repeatedly stresses Judah's special status from the very beginnings of Israel's history.... [In Genesis], it was Judah, among all of Jacob's sons, whose destiny was to rule over all the other tribes in Israel." Emerton notes that it is "widely agreed" that the story of Judah and Tamar "reflects a period after the settlement of the Israelites in Canaan". He also suggests the possibility that it contains "aetiological motifs concerned with the eponymous ancestors of the clans of Judah". Emerton notes that Dillman and Noth considered the account of the deaths of Er and Onan to "reflect the dying out of two clans of Judah bearing their names, or at least of their failure to maintain a separate existence". However, this view was "trenchantly criticized" by Thomas L. Thompson. Along with the account of Lot and his daughters (Genesis 19:30–38), Tamar and Judah is one of two instances of "sperm stealing" in the Bible, in which a woman seduces a male relative under false pretenses in order to become pregnant. Jewish tradition The text of the Torah argues that the name of Judah, meaning to thank or admit, refers to Leah's intent to thank Hashem, on account of having achieved four children, and derived from odeh, meaning I will give thanks. In classical rabbinical literature, the name is interpreted as a combination of Yahweh and a dalet (the letter d); in Gematria, the dalet has the numerical value 4, which these rabbinical sources argue refers to Judah being Jacob's fourth son. Since Leah was matriarch, Jewish scholars think the text's authors believed the tribe was part of the original Israelite confederation; however, it is worthy of note that the tribe of Judah was not purely Israelite, but contained a large admixture of non-Israelites, with a number of Kenizzite groups, the Jerahmeelites, and the Kenites, merging into the tribe at various points. Classical rabbinical sources refer to the passage "... a ruler came from Judah", from 1 Chronicles 5:2, to imply that Judah was the leader of his brothers, terming him the king. This passage also describes Judah as the strongest of his brothers in which rabbinical literature portray him as having had extraordinary physical strength, able to shout for over 400 parasangs, able to crush iron into dust by his mouth, and with hair that stiffened so much, when he became angry, that it pierced his clothes. Classical rabbinical sources also allude to a war between the Canaanites and Judah's family (not mentioned in the Hebrew Bible), as a result of their destruction of Shechem in revenge for the rape of Dinah; Judah features heavily as a protagonist in accounts of this war. In these accounts Judah kills Jashub, king of Tappuah, in hand-to-hand combat, after first having deposed Jashub from his horse by throwing an extremely heavy stone (60 shekels in weight) at him from a large distance away (the Midrash Wayissau states 177⅓ cubits, while other sources have only 30 cubits); the accounts say that Judah was able to achieve this even though he was himself under attack, from arrows which Jashub was shooting at him with both hands. The accounts go on to state that while Judah was trying to remove Jashub's armour from his corpse, nine assistants of Jashub fell upon him in combat, but after Judah killed one, he scared away the others; nevertheless, Judah killed several members of Jashub's army (42 men according to the midrashic Book of Jasher, but 1000 men according to the Testament of Judah). According to some classical sources, Jacob suspected that Judah had killed Joseph, especially, according to the Midrash Tanhuma, when Judah was the one who had brought the blood stained coat to Jacob. Since rabbinical sources held Judah to have been the leader of his brothers, these sources also hold that the other nine brothers blamed him to be responsible for this deception, even if it was not Judah himself who brought the coat to Jacob. Even if Judah had been trying to save Joseph, the classical rabbinical sources still regard him negatively for it; these sources argue that, as the leader of the brothers, Judah should have made more effort and carried Joseph home to Jacob on his (Judah's) own shoulders. These sources argue that Judah's brothers, after witnessing Jacob's grief at the loss of Joseph, deposed and excommunicated Judah, as the brothers held Judah entirely responsible, since they would have brought Joseph home if Judah had asked them to do so. Divine punishment, according to such classical sources, was also inflicted on Judah in punishment; the death of Er and Onan, and of his wife, are portrayed in by such classical rabbis as being acts of divine retribution. When Benjamin was held in bondage following the accusation of stealing Joseph's cup, Judah offered himself among his brethren as a bondman in replace of him, but Joseph was strict that the punishment is only applied to the one who was guilty, not to the innocent ones. According to classical rabbinical literature, because Judah had proposed that he should take any blame forever, this ultimately led to his bones being rolled around his coffin without cease, while it was being carried during the Exodus, until Moses interceded with God, by arguing that Judah's confession (in regard to cohabiting with Tamar) had led to Reuben confessing his own incest. Apparently, Judah learned a lesson from his experience with Tamar that he must be responsible for those around him and this eventually prepares him for his future reconciliatory encounter with Joseph. Genesis Rabbah, and particularly the midrashic book of Jasher, expand on this by describing Judah's plea[clarification needed] as much more extensive than given in the Torah, and more vehement. The classical rabbinical literature argues that Judah reacted violently to the threat against Benjamin, shouting so loudly that Hushim, who was then in Canaan, was able to hear Judah ask him to travel to Egypt, to help Judah destroy it; some sources have Judah angrily picking up an extremely heavy stone (400 shekels in weight), throwing it into the air, then grinding it to dust with his feet once it had landed. These rabbinical sources argue that Judah had Naphtali enumerate the districts of Egypt, and after finding out that there were 12 (historically, there were actually 20 in Lower Egypt and 22 in Upper Egypt), he decided to destroy three himself and have his brothers destroy one of the remaining districts each; the threat of destroying Egypt was, according to these sources, what really motivated Joseph to reveal himself to his brothers. Before his death, Judah told his children about his bravery and heroism in the wars against the kings of Canaan and the family of Esau, also confessed his shortcomings caused by wine that led him astray in his relationship with Bathshua and Tamar. Judah admonished his sons not to love gold, and not to look upon the beauty of women, for through these things, the sons of Judah will fall into misery. In his last words, he reminded them to observe the whole law of the Lord. According to Classical rabbinical literature, Judah was born on 15 Sivan (early June); classical sources differ on the date of death, with the Book of Jubilees advocating a death at age 119, 18 years before Levi, but the midrashic Book of Jasher advocating a death at the age of 129. The marriage of Judah and births of his children are described in a passage widely regarded as an abrupt change to the surrounding narrative. The passage is often regarded as presenting a significant chronological issue, as the surrounding context appears to constrain the events of the passage to happening within 22 years, and the context together with the passage itself requires the birth of the grandson of Judah and of his son's wife, and the birth of that son to have happened within this time (to be consistent, this requires an average of less than 8 years gap per generation). According to textual scholars, the reason for the abrupt interruption this passage causes to the surrounding narrative, and the chronological anomaly it seems to present, is that it derives from the Jahwist source, while the immediately surrounding narrative is from the Elohist. Family Tree Tomb Local Muslim and Samaritan traditions placed the tomb of Judah (Nabi Huda ibn Sayyidna Ya'qub, "the prophet Judah, son of our lord Jacob") at al-Yahudiya, present-day Yehud. Today, it is a destination of Jewish pilgrimage. Another local tradition, held by Druze and Muslims, places the tomb of Judah in "Nabi Yehuda", a maqam located near Horvat Omrit in the Hula Valley. See also References Bibliography External links |
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[SOURCE: https://en.wikipedia.org/wiki/Black_hole#cite_note-57] | [TOKENS: 13839] |
Contents Black hole A black hole is an astronomical body so compact that its gravity prevents anything, including light, from escaping. Albert Einstein's theory of general relativity predicts that a sufficiently compact mass will form a black hole. The boundary of no escape is called the event horizon. In general relativity, a black hole's event horizon seals an object's fate but produces no locally detectable change when crossed. General relativity also predicts that every black hole should have a central singularity, where the curvature of spacetime is infinite. In many ways, a black hole acts like an ideal black body, as it reflects no light. Quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is of the order of billionths of a kelvin for stellar black holes, making it essentially impossible to observe directly. Objects whose gravitational fields are too strong for light to escape were first considered in the 18th century by John Michell and Pierre-Simon Laplace. In 1916, Karl Schwarzschild found the first modern solution of general relativity that would characterise a black hole. Due to his influential research, the Schwarzschild metric is named after him. David Finkelstein, in 1958, first interpreted Schwarzschild's model as a region of space from which nothing can escape. Black holes were long considered a mathematical curiosity; it was not until the 1960s that theoretical work showed they were a generic prediction of general relativity. The first black hole known was Cygnus X-1, identified by several researchers independently in 1971. Black holes typically form when massive stars collapse at the end of their life cycle. After a black hole has formed, it can grow by absorbing mass from its surroundings. Supermassive black holes of millions of solar masses may form by absorbing other stars and merging with other black holes, or via direct collapse of gas clouds. There is consensus that supermassive black holes exist in the centres of most galaxies. The presence of a black hole can be inferred through its interaction with other matter and with electromagnetic radiation such as visible light. Matter falling toward a black hole can form an accretion disk of infalling plasma, heated by friction and emitting light. In extreme cases, this creates a quasar, some of the brightest objects in the universe. Merging black holes can also be detected by observation of the gravitational waves they emit. If other stars are orbiting a black hole, their orbits can be used to determine the black hole's mass and location. Such observations can be used to exclude possible alternatives such as neutron stars. In this way, astronomers have identified numerous stellar black hole candidates in binary systems and established that the radio source known as Sagittarius A*, at the core of the Milky Way galaxy, contains a supermassive black hole of about 4.3 million solar masses. History The idea of a body so massive that even light could not escape was first proposed in the late 18th century by English astronomer and clergyman John Michell and independently by French scientist Pierre-Simon Laplace. Both scholars proposed very large stars in contrast to the modern concept of an extremely dense object. Michell's idea, in a short part of a letter published in 1784, calculated that a star with the same density but 500 times the radius of the sun would not let any emitted light escape; the surface escape velocity would exceed the speed of light.: 122 Michell correctly hypothesized that such supermassive but non-radiating bodies might be detectable through their gravitational effects on nearby visible bodies. In 1796, Laplace mentioned that a star could be invisible if it were sufficiently large while speculating on the origin of the Solar System in his book Exposition du Système du Monde. Franz Xaver von Zach asked Laplace for a mathematical analysis, which Laplace provided and published in a journal edited by von Zach. In 1905, Albert Einstein showed that the laws of electromagnetism would be invariant under a Lorentz transformation: they would be identical for observers travelling at different velocities relative to each other. This discovery became known as the principle of special relativity. Although the laws of mechanics had already been shown to be invariant, gravity remained yet to be included.: 19 In 1907, Einstein published a paper proposing his equivalence principle, the hypothesis that inertial mass and gravitational mass have a common cause. Using the principle, Einstein predicted the redshift and half of the lensing effect of gravity on light; the full prediction of gravitational lensing required development of general relativity.: 19 By 1915, Einstein refined these ideas into his general theory of relativity, which explained how matter affects spacetime, which in turn affects the motion of other matter. This formed the basis for black hole physics. Only a few months after Einstein published the field equations describing general relativity, astrophysicist Karl Schwarzschild set out to apply the idea to stars. He assumed spherical symmetry with no spin and found a solution to Einstein's equations.: 124 A few months after Schwarzschild, Johannes Droste, a student of Hendrik Lorentz, independently gave the same solution. At a certain radius from the center of the mass, the Schwarzschild solution became singular, meaning that some of the terms in the Einstein equations became infinite. The nature of this radius, which later became known as the Schwarzschild radius, was not understood at the time. Many physicists of the early 20th century were skeptical of the existence of black holes. In a 1926 popular science book, Arthur Eddington critiqued the idea of a star with mass compressed to its Schwarzschild radius as a flaw in the then-poorly-understood theory of general relativity.: 134 In 1939, Einstein himself used his theory of general relativity in an attempt to prove that black holes were impossible. His work relied on increasing pressure or increasing centrifugal force balancing the force of gravity so that the object would not collapse beyond its Schwarzschild radius. He missed the possibility that implosion would drive the system below this critical value.: 135 By the 1920s, astronomers had classified a number of white dwarf stars as too cool and dense to be explained by the gradual cooling of ordinary stars. In 1926, Ralph Fowler showed that quantum-mechanical degeneracy pressure was larger than thermal pressure at these densities.: 145 In 1931, Subrahmanyan Chandrasekhar calculated that a non-rotating body of electron-degenerate matter below a certain limiting mass is stable, and by 1934 he showed that this explained the catalog of white dwarf stars.: 151 When Chandrasekhar announced his results, Eddington pointed out that stars above this limit would radiate until they were sufficiently dense to prevent light from exiting, a conclusion he considered absurd. Eddington and, later, Lev Landau argued that some yet unknown mechanism would stop the collapse. In the 1930s, Fritz Zwicky and Walter Baade studied stellar novae, focusing on exceptionally bright ones they called supernovae. Zwicky promoted the idea that supernovae produced stars with the density of atomic nuclei—neutron stars—but this idea was largely ignored.: 171 In 1939, based on Chandrasekhar's reasoning, J. Robert Oppenheimer and George Volkoff predicted that neutron stars below a certain mass limit, later called the Tolman–Oppenheimer–Volkoff limit, would be stable due to neutron degeneracy pressure. Above that limit, they reasoned that either their model would not apply or that gravitational contraction would not stop.: 380 John Archibald Wheeler and two of his students resolved questions about the model behind the Tolman–Oppenheimer–Volkoff (TOV) limit. Harrison and Wheeler developed the equations of state relating density to pressure for cold matter all the way through electron degeneracy and neutron degeneracy. Masami Wakano and Wheeler then used the equations to compute the equilibrium curve for stars, relating mass to circumference. They found no additional features that would invalidate the TOV limit. This meant that the only thing that could prevent black holes from forming was a dynamic process ejecting sufficient mass from a star as it cooled.: 205 The modern concept of black holes was formulated by Robert Oppenheimer and his student Hartland Snyder in 1939.: 80 In the paper, Oppenheimer and Snyder solved Einstein's equations of general relativity for an idealized imploding star, in a model later called the Oppenheimer–Snyder model, then described the results from far outside the star. The implosion starts as one might expect: the star material rapidly collapses inward. However, as the density of the star increases, gravitational time dilation increases and the collapse, viewed from afar, seems to slow down further and further until the star reaches its Schwarzschild radius, where it appears frozen in time.: 217 In 1958, David Finkelstein identified the Schwarzschild surface as an event horizon, calling it "a perfect unidirectional membrane: causal influences can cross it in only one direction". In this sense, events that occur inside of the black hole cannot affect events that occur outside of the black hole. Finkelstein created a new reference frame to include the point of view of infalling observers.: 103 Finkelstein's new frame of reference allowed events at the surface of an imploding star to be related to events far away. By 1962 the two points of view were reconciled, convincing many skeptics that implosion into a black hole made physical sense.: 226 The era from the mid-1960s to the mid-1970s was the "golden age of black hole research", when general relativity and black holes became mainstream subjects of research.: 258 In this period, more general black hole solutions were found. In 1963, Roy Kerr found the exact solution for a rotating black hole. Two years later, Ezra Newman found the cylindrically symmetric solution for a black hole that is both rotating and electrically charged. In 1967, Werner Israel found that the Schwarzschild solution was the only possible solution for a nonspinning, uncharged black hole, meaning that a Schwarzschild black hole would be defined by its mass alone. Similar identities were later found for Reissner-Nordstrom and Kerr black holes, defined only by their mass and their charge or spin respectively. Together, these findings became known as the no-hair theorem, which states that a stationary black hole is completely described by the three parameters of the Kerr–Newman metric: mass, angular momentum, and electric charge. At first, it was suspected that the strange mathematical singularities found in each of the black hole solutions only appeared due to the assumption that a black hole would be perfectly spherically symmetric, and therefore the singularities would not appear in generic situations where black holes would not necessarily be symmetric. This view was held in particular by Vladimir Belinski, Isaak Khalatnikov, and Evgeny Lifshitz, who tried to prove that no singularities appear in generic solutions, although they would later reverse their positions. However, in 1965, Roger Penrose proved that general relativity without quantum mechanics requires that singularities appear in all black holes. Astronomical observations also made great strides during this era. In 1967, Antony Hewish and Jocelyn Bell Burnell discovered pulsars and by 1969, these were shown to be rapidly rotating neutron stars. Until that time, neutron stars, like black holes, were regarded as just theoretical curiosities, but the discovery of pulsars showed their physical relevance and spurred a further interest in all types of compact objects that might be formed by gravitational collapse. Based on observations in Greenwich and Toronto in the early 1970s, Cygnus X-1, a galactic X-ray source discovered in 1964, became the first astronomical object commonly accepted to be a black hole. Work by James Bardeen, Jacob Bekenstein, Carter, and Hawking in the early 1970s led to the formulation of black hole thermodynamics. These laws describe the behaviour of a black hole in close analogy to the laws of thermodynamics by relating mass to energy, area to entropy, and surface gravity to temperature. The analogy was completed: 442 when Hawking, in 1974, showed that quantum field theory implies that black holes should radiate like a black body with a temperature proportional to the surface gravity of the black hole, predicting the effect now known as Hawking radiation. While Cygnus X-1, a stellar-mass black hole, was generally accepted by the scientific community as a black hole by the end of 1973, it would be decades before a supermassive black hole would gain the same broad recognition. Although, as early as the 1960s, physicists such as Donald Lynden-Bell and Martin Rees had suggested that powerful quasars in the center of galaxies were powered by accreting supermassive black holes, little observational proof existed at the time. However, the Hubble Space Telescope, launched decades later, found that supermassive black holes were not only present in these active galactic nuclei, but that supermassive black holes in the center of galaxies were ubiquitous: Almost every galaxy had a supermassive black hole at its center, many of which were quiescent. In 1999, David Merritt proposed the M–sigma relation, which related the dispersion of the velocity of matter in the center bulge of a galaxy to the mass of the supermassive black hole at its core. Subsequent studies confirmed this correlation. Around the same time, based on telescope observations of the velocities of stars at the center of the Milky Way galaxy, independent work groups led by Andrea Ghez and Reinhard Genzel concluded that the compact radio source in the center of the galaxy, Sagittarius A*, was likely a supermassive black hole. On 11 February 2016, the LIGO Scientific Collaboration and Virgo Collaboration announced the first direct detection of gravitational waves, named GW150914, representing the first observation of a black hole merger. At the time of the merger, the black holes were approximately 1.4 billion light-years away from Earth and had masses of 30 and 35 solar masses.: 6 In 2017, Rainer Weiss, Kip Thorne, and Barry Barish, who had spearheaded the project, were awarded the Nobel Prize in Physics for their work. Since the initial discovery in 2015, hundreds more gravitational waves have been observed by LIGO and another interferometer, Virgo. On 10 April 2019, the first direct image of a black hole and its vicinity was published, following observations made by the Event Horizon Telescope (EHT) in 2017 of the supermassive black hole in Messier 87's galactic centre. In 2022, the Event Horizon Telescope collaboration released an image of the black hole in the center of the Milky Way galaxy, Sagittarius A*; The data had been collected in 2017. In 2020, the Nobel Prize in Physics was awarded for work on black holes. Andrea Ghez and Reinhard Genzel shared one-half for their discovery that Sagittarius A* is a supermassive black hole. Penrose received the other half for his work showing that the mathematics of general relativity requires the formation of black holes. Cosmologists lamented that Hawking's extensive theoretical work on black holes would not be honored since he died in 2018. In December 1967, a student reportedly suggested the phrase black hole at a lecture by John Wheeler; Wheeler adopted the term for its brevity and "advertising value", and Wheeler's stature in the field ensured it quickly caught on, leading some to credit Wheeler with coining the phrase. However, the term was used by others around that time. Science writer Marcia Bartusiak traces the term black hole to physicist Robert H. Dicke, who in the early 1960s reportedly compared the phenomenon to the Black Hole of Calcutta, notorious as a prison where people entered but never left alive. The term was used in print by Life and Science News magazines in 1963, and by science journalist Ann Ewing in her article "'Black Holes' in Space", dated 18 January 1964, which was a report on a meeting of the American Association for the Advancement of Science held in Cleveland, Ohio. Definition A black hole is generally defined as a region of spacetime from which no information-carrying signals or objects can escape. However, verifying an object as a black hole by this definition would require waiting for an infinite time and at an infinite distance from the black hole to verify that indeed, nothing has escaped, and thus cannot be used to identify a physical black hole. Broadly, physicists do not have a precisely-agreed-upon definition of a black hole. Among astrophysicists, a black hole is a compact object with a mass larger than four solar masses. A black hole may also be defined as a reservoir of information: 142 or a region where space is falling inwards faster than the speed of light. Properties The no-hair theorem postulates that, once it achieves a stable condition after formation, a black hole has only three independent physical properties: mass, electric charge, and angular momentum; the black hole is otherwise featureless. If the conjecture is true, any two black holes that share the same values for these properties, or parameters, are indistinguishable from one another. The degree to which the conjecture is true for real black holes is currently an unsolved problem. The simplest static black holes have mass but neither electric charge nor angular momentum. According to Birkhoff's theorem, these Schwarzschild black holes are the only vacuum solution that is spherically symmetric. Solutions describing more general black holes also exist. Non-rotating charged black holes are described by the Reissner–Nordström metric, while the Kerr metric describes a non-charged rotating black hole. The most general stationary black hole solution known is the Kerr–Newman metric, which describes a black hole with both charge and angular momentum. The simplest static black holes have mass but neither electric charge nor angular momentum. Contrary to the popular notion of a black hole "sucking in everything" in its surroundings, from far away, the external gravitational field of a black hole is identical to that of any other body of the same mass. While a black hole can theoretically have any positive mass, the charge and angular momentum are constrained by the mass. The total electric charge Q and the total angular momentum J are expected to satisfy the inequality Q 2 4 π ϵ 0 + c 2 J 2 G M 2 ≤ G M 2 {\displaystyle {\frac {Q^{2}}{4\pi \epsilon _{0}}}+{\frac {c^{2}J^{2}}{GM^{2}}}\leq GM^{2}} for a black hole of mass M. Black holes with the maximum possible charge or spin satisfying this inequality are called extremal black holes. Solutions of Einstein's equations that violate this inequality exist, but they do not possess an event horizon. These are so-called naked singularities that can be observed from the outside. Because these singularities make the universe inherently unpredictable, many physicists believe they could not exist. The weak cosmic censorship hypothesis, proposed by Sir Roger Penrose, rules out the formation of such singularities, when they are created through the gravitational collapse of realistic matter. However, this theory has not yet been proven, and some physicists believe that naked singularities could exist. It is also unknown whether black holes could even become extremal, forming naked singularities, since natural processes counteract increasing spin and charge when a black hole becomes near-extremal. The total mass of a black hole can be estimated by analyzing the motion of objects near the black hole, such as stars or gas. All black holes spin, often fast—One supermassive black hole, GRS 1915+105 has been estimated to spin at over 1,000 revolutions per second. The Milky Way's central black hole Sagittarius A* rotates at about 90% of the maximum rate. The spin rate can be inferred from measurements of atomic spectral lines in the X-ray range. As gas near the black hole plunges inward, high energy X-ray emission from electron-positron pairs illuminates the gas further out, appearing red-shifted due to relativistic effects. Depending on the spin of the black hole, this plunge happens at different radii from the hole, with different degrees of redshift. Astronomers can use the gap between the x-ray emission of the outer disk and the redshifted emission from plunging material to determine the spin of the black hole. A newer way to estimate spin is based on the temperature of gasses accreting onto the black hole. The method requires an independent measurement of the black hole mass and inclination angle of the accretion disk followed by computer modeling. Gravitational waves from coalescing binary black holes can also provide the spin of both progenitor black holes and the merged hole, but such events are rare. A spinning black hole has angular momentum. The supermassive black hole in the center of the Messier 87 (M87) galaxy appears to have an angular momentum very close to the maximum theoretical value. That uncharged limit is J ≤ G M 2 c , {\displaystyle J\leq {\frac {GM^{2}}{c}},} allowing definition of a dimensionless spin magnitude such that 0 ≤ c J G M 2 ≤ 1. {\displaystyle 0\leq {\frac {cJ}{GM^{2}}}\leq 1.} Most black holes are believed to have an approximately neutral charge. For example, Michal Zajaček, Arman Tursunov, Andreas Eckart, and Silke Britzen found the electric charge of Sagittarius A* to be at least ten orders of magnitude below the theoretical maximum. A charged black hole repels other like charges just like any other charged object. If a black hole were to become charged, particles with an opposite sign of charge would be pulled in by the extra electromagnetic force, while particles with the same sign of charge would be repelled, neutralizing the black hole. This effect may not be as strong if the black hole is also spinning. The presence of charge can reduce the diameter of the black hole by up to 38%. The charge Q for a nonspinning black hole is bounded by Q ≤ G M , {\displaystyle Q\leq {\sqrt {G}}M,} where G is the gravitational constant and M is the black hole's mass. Classification Black holes can have a wide range of masses. The minimum mass of a black hole formed by stellar gravitational collapse is governed by the maximum mass of a neutron star and is believed to be approximately two-to-four solar masses. However, theoretical primordial black holes, believed to have formed soon after the Big Bang, could be far smaller, with masses as little as 10−5 grams at formation. These very small black holes are sometimes called micro black holes. Black holes formed by stellar collapse are called stellar black holes. Estimates of their maximum mass at formation vary, but generally range from 10 to 100 solar masses, with higher estimates for black holes progenated by low-metallicity stars. The mass of a black hole formed via a supernova has a lower bound: If the progenitor star is too small, the collapse may be stopped by the degeneracy pressure of the star's constituents, allowing the condensation of matter into an exotic denser state. Degeneracy pressure occurs from the Pauli exclusion principle—Particles will resist being in the same place as each other. Smaller progenitor stars, with masses less than about 8 M☉, will be held together by the degeneracy pressure of electrons and will become a white dwarf. For more massive progenitor stars, electron degeneracy pressure is no longer strong enough to resist the force of gravity and the star will be held together by neutron degeneracy pressure, which can occur at much higher densities, forming a neutron star. If the star is still too massive, even neutron degeneracy pressure will not be able to resist the force of gravity and the star will collapse into a black hole.: 5.8 Stellar black holes can also gain mass via accretion of nearby matter, often from a companion object such as a star. Black holes that are larger than stellar black holes but smaller than supermassive black holes are called intermediate-mass black holes, with masses of approximately 102 to 105 solar masses. These black holes seem to be rarer than their stellar and supermassive counterparts, with relatively few candidates having been observed. Physicists have speculated that such black holes may form from collisions in globular and star clusters or at the center of low-mass galaxies. They may also form as the result of mergers of smaller black holes, with several LIGO observations finding merged black holes within the 110-350 solar mass range. The black holes with the largest masses are called supermassive black holes, with masses more than 106 times that of the Sun. These black holes are believed to exist at the centers of almost every large galaxy, including the Milky Way. Some scientists have proposed a subcategory of even larger black holes, called ultramassive black holes, with masses greater than 109-1010 solar masses. Theoretical models predict that the accretion disc that feeds black holes will be unstable once a black hole reaches 50-100 billion times the mass of the Sun, setting a rough upper limit to black hole mass. Structure While black holes are conceptually invisible sinks of all matter and light, in astronomical settings, their enormous gravity alters the motion of surrounding objects and pulls nearby gas inwards at near-light speed, making the area around black holes the brightest objects in the universe. Some black holes have relativistic jets—thin streams of plasma travelling away from the black hole at more than one-tenth of the speed of light. A small faction of the matter falling towards the black hole gets accelerated away along the hole rotation axis. These jets can extend as far as millions of parsecs from the black hole itself. Black holes of any mass can have jets. However, they are typically observed around spinning black holes with strongly-magnetized accretion disks. Relativistic jets were more common in the early universe, when galaxies and their corresponding supermassive black holes were rapidly gaining mass. All black holes with jets also have an accretion disk, but the jets are usually brighter than the disk. Quasars, typically found in other galaxies, are believed to be supermassive black holes with jets; microquasars are believed to be stellar-mass objects with jets, typically observed in the Milky Way. The mechanism of formation of jets is not yet known, but several options have been proposed. One method proposed to fuel these jets is the Blandford-Znajek process, which suggests that the dragging of magnetic field lines by a black hole's rotation could launch jets of matter into space. The Penrose process, which involves extraction of a black hole's rotational energy, has also been proposed as a potential mechanism of jet propulsion. Due to conservation of angular momentum, gas falling into the gravitational well created by a massive object will typically form a disk-like structure around the object.: 242 As the disk's angular momentum is transferred outward due to internal processes, its matter falls farther inward, converting its gravitational energy into heat and releasing a large flux of x-rays. The temperature of these disks can range from thousands to millions of Kelvin, and temperatures can differ throughout a single accretion disk. Accretion disks can also emit in other parts of the electromagnetic spectrum, depending on the disk's turbulence and magnetization and the black hole's mass and angular momentum. Accretion disks can be defined as geometrically thin or geometrically thick. Geometrically thin disks are mostly confined to the black hole's equatorial plane and have a well-defined edge at the innermost stable circular orbit (ISCO), while geometrically thick disks are supported by internal pressure and temperature and can extend inside the ISCO. Disks with high rates of electron scattering and absorption, appearing bright and opaque, are called optically thick; optically thin disks are more translucent and produce fainter images when viewed from afar. Accretion disks of black holes accreting beyond the Eddington limit are often referred to as polish donuts due to their thick, toroidal shape that resembles that of a donut. Quasar accretion disks are expected to usually appear blue in color. The disk for a stellar black hole, on the other hand, would likely look orange, yellow, or red, with its inner regions being the brightest. Theoretical research suggests that the hotter a disk is, the bluer it should be, although this is not always supported by observations of real astronomical objects. Accretion disk colors may also be altered by the Doppler effect, with the part of the disk travelling towards an observer appearing bluer and brighter and the part of the disk travelling away from the observer appearing redder and dimmer. In Newtonian gravity, test particles can stably orbit at arbitrary distances from a central object. In general relativity, however, there exists a smallest possible radius for which a massive particle can orbit stably. Any infinitesimal inward perturbations to this orbit will lead to the particle spiraling into the black hole, and any outward perturbations will, depending on the energy, cause the particle to spiral in, move to a stable orbit further from the black hole, or escape to infinity. This orbit is called the innermost stable circular orbit, or ISCO. The location of the ISCO depends on the spin of the black hole and the spin of the particle itself. In the case of a Schwarzschild black hole (spin zero) and a particle without spin, the location of the ISCO is: r I S C O = 3 r s = 6 G M c 2 , {\displaystyle r_{\rm {ISCO}}=3\,r_{\text{s}}={\frac {6\,GM}{c^{2}}},} where r I S C O {\displaystyle r_{\rm {_{ISCO}}}} is the radius of the ISCO, r s {\displaystyle r_{\text{s}}} is the Schwarzschild radius of the black hole, G {\displaystyle G} is the gravitational constant, and c {\displaystyle c} is the speed of light. The radius of this orbit changes slightly based on particle spin. For charged black holes, the ISCO moves inwards. For spinning black holes, the ISCO is moved inwards for particles orbiting in the same direction that the black hole is spinning (prograde) and outwards for particles orbiting in the opposite direction (retrograde). For example, the ISCO for a particle orbiting retrograde can be as far out as about 9 r s {\displaystyle 9r_{\text{s}}} , while the ISCO for a particle orbiting prograde can be as close as at the event horizon itself. The photon sphere is a spherical boundary for which photons moving on tangents to that sphere are bent completely around the black hole, possibly orbiting multiple times. Light rays with impact parameters less than the radius of the photon sphere enter the black hole. For Schwarzschild black holes, the photon sphere has a radius 1.5 times the Schwarzschild radius; the radius for non-Schwarzschild black holes is at least 1.5 times the radius of the event horizon. When viewed from a great distance, the photon sphere creates an observable black hole shadow. Since no light emerges from within the black hole, this shadow is the limit for possible observations.: 152 The shadow of colliding black holes should have characteristic warped shapes, allowing scientists to detect black holes that are about to merge. While light can still escape from the photon sphere, any light that crosses the photon sphere on an inbound trajectory will be captured by the black hole. Therefore, any light that reaches an outside observer from the photon sphere must have been emitted by objects between the photon sphere and the event horizon. Light emitted towards the photon sphere may also curve around the black hole and return to the emitter. For a rotating, uncharged black hole, the radius of the photon sphere depends on the spin parameter and whether the photon is orbiting prograde or retrograde. For a photon orbiting prograde, the photon sphere will be 1-3 Schwarzschild radii from the center of the black hole, while for a photon orbiting retrograde, the photon sphere will be between 3-5 Schwarzschild radii from the center of the black hole. The exact location of the photon sphere depends on the magnitude of the black hole's rotation. For a charged, nonrotating black hole, there will only be one photon sphere, and the radius of the photon sphere will decrease for increasing black hole charge. For non-extremal, charged, rotating black holes, there will always be two photon spheres, with the exact radii depending on the parameters of the black hole. Near a rotating black hole, spacetime rotates similar to a vortex. The rotating spacetime will drag any matter and light into rotation around the spinning black hole. This effect of general relativity, called frame dragging, gets stronger closer to the spinning mass. The region of spacetime in which it is impossible to stay still is called the ergosphere. The ergosphere of a black hole is a volume bounded by the black hole's event horizon and the ergosurface, which coincides with the event horizon at the poles but bulges out from it around the equator. Matter and radiation can escape from the ergosphere. Through the Penrose process, objects can emerge from the ergosphere with more energy than they entered with. The extra energy is taken from the rotational energy of the black hole, slowing down the rotation of the black hole.: 268 A variation of the Penrose process in the presence of strong magnetic fields, the Blandford–Znajek process, is considered a likely mechanism for the enormous luminosity and relativistic jets of quasars and other active galactic nuclei. The observable region of spacetime around a black hole closest to its event horizon is called the plunging region. In this area it is no longer possible for free falling matter to follow circular orbits or stop a final descent into the black hole. Instead, it will rapidly plunge toward the black hole at close to the speed of light, growing increasingly hot and producing a characteristic, detectable thermal emission. However, light and radiation emitted from this region can still escape from the black hole's gravitational pull. For a nonspinning, uncharged black hole, the radius of the event horizon, or Schwarzschild radius, is proportional to the mass, M, through r s = 2 G M c 2 ≈ 2.95 M M ⊙ k m , {\displaystyle r_{\mathrm {s} }={\frac {2GM}{c^{2}}}\approx 2.95\,{\frac {M}{M_{\odot }}}~\mathrm {km,} } where rs is the Schwarzschild radius and M☉ is the mass of the Sun.: 124 For a black hole with nonzero spin or electric charge, the radius is smaller,[Note 1] until an extremal black hole could have an event horizon close to r + = G M c 2 , {\displaystyle r_{\mathrm {+} }={\frac {GM}{c^{2}}},} half the radius of a nonspinning, uncharged black hole of the same mass. Since the volume within the Schwarzschild radius increase with the cube of the radius, average density of a black hole inside its Schwarzschild radius is inversely proportional to the square of its mass: supermassive black holes are much less dense than stellar black holes. The average density of a 108 M☉ black hole is comparable to that of water. The defining feature of a black hole is the existence of an event horizon, a boundary in spacetime through which matter and light can pass only inward towards the center of the black hole. Nothing, not even light, can escape from inside the event horizon. The event horizon is referred to as such because if an event occurs within the boundary, information from that event cannot reach or affect an outside observer, making it impossible to determine whether such an event occurred.: 179 For non-rotating black holes, the geometry of the event horizon is precisely spherical, while for rotating black holes, the event horizon is oblate. To a distant observer, a clock near a black hole would appear to tick more slowly than one further from the black hole.: 217 This effect, known as gravitational time dilation, would also cause an object falling into a black hole to appear to slow as it approached the event horizon, never quite reaching the horizon from the perspective of an outside observer.: 218 All processes on this object would appear to slow down, and any light emitted by the object to appear redder and dimmer, an effect known as gravitational redshift. An object falling from half of a Schwarzschild radius above the event horizon would fade away until it could no longer be seen, disappearing from view within one hundredth of a second. It would also appear to flatten onto the black hole, joining all other material that had ever fallen into the hole. On the other hand, an observer falling into a black hole would not notice any of these effects as they cross the event horizon. Their own clocks appear to them to tick normally, and they cross the event horizon after a finite time without noting any singular behaviour. In general relativity, it is impossible to determine the location of the event horizon from local observations, due to Einstein's equivalence principle.: 222 Black holes that are rotating and/or charged have an inner horizon, often called the Cauchy horizon, inside of the black hole. The inner horizon is divided up into two segments: an ingoing section and an outgoing section. At the ingoing section of the Cauchy horizon, radiation and matter that fall into the black hole would build up at the horizon, causing the curvature of spacetime to go to infinity. This would cause an observer falling in to experience tidal forces. This phenomenon is often called mass inflation, since it is associated with a parameter dictating the black hole's internal mass growing exponentially, and the buildup of tidal forces is called the mass-inflation singularity or Cauchy horizon singularity. Some physicists have argued that in realistic black holes, accretion and Hawking radiation would stop mass inflation from occurring. At the outgoing section of the inner horizon, infalling radiation would backscatter off of the black hole's spacetime curvature and travel outward, building up at the outgoing Cauchy horizon. This would cause an infalling observer to experience a gravitational shock wave and tidal forces as the spacetime curvature at the horizon grew to infinity. This buildup of tidal forces is called the shock singularity. Both of these singularities are weak, meaning that an object crossing them would only be deformed a finite amount by tidal forces, even though the spacetime curvature would still be infinite at the singularity. This is as opposed to a strong singularity, where an object hitting the singularity would be stretched and squeezed by an infinite amount. They are also null singularities, meaning that a photon could travel parallel to the them without ever being intercepted. Ignoring quantum effects, every black hole has a singularity inside, points where the curvature of spacetime becomes infinite, and geodesics terminate within a finite proper time.: 205 For a non-rotating black hole, this region takes the shape of a single point; for a rotating black hole it is smeared out to form a ring singularity that lies in the plane of rotation.: 264 In both cases, the singular region has zero volume. All of the mass of the black hole ends up in the singularity.: 252 Since the singularity has nonzero mass in an infinitely small space, it can be thought of as having infinite density. Observers falling into a Schwarzschild black hole (i.e., non-rotating and not charged) cannot avoid being carried into the singularity once they cross the event horizon. As they fall further into the black hole, they will be torn apart by the growing tidal forces in a process sometimes referred to as spaghettification or the noodle effect. Eventually, they will reach the singularity and be crushed into an infinitely small point.: 182 However any perturbations, such as those caused by matter or radiation falling in, would cause space to oscillate chaotically near the singularity. Any matter falling in would experience intense tidal forces rapidly changing in direction, all while being compressed into an increasingly small volume. Alternative forms of general relativity, including addition of some quatum effects, can lead to regular, or nonsingular, black holes without singularities. For example, the fuzzball model, based on string theory, states that black holes are actually made up of quantum microstates and need not have a singularity or an event horizon. The theory of loop quantum gravity proposes that the curvature and density at the center of a black hole is large, but not infinite. Formation Black holes are formed by gravitational collapse of massive stars, either by direct collapse or during a supernova explosion in a process called fallback. Black holes can result from the merger of two neutron stars or a neutron star and a black hole. Other more speculative mechanisms include primordial black holes created from density fluctuations in the early universe, the collapse of dark stars, a hypothetical object powered by annihilation of dark matter, or from hypothetical self-interacting dark matter. Gravitational collapse occurs when an object's internal pressure is insufficient to resist the object's own gravity. At the end of a star's life, it will run out of hydrogen to fuse, and will start fusing more and more massive elements, until it gets to iron. Since the fusion of elements heavier than iron would require more energy than it would release, nuclear fusion ceases. If the iron core of the star is too massive, the star will no longer be able to support itself and will undergo gravitational collapse. While most of the energy released during gravitational collapse is emitted very quickly, an outside observer does not actually see the end of this process. Even though the collapse takes a finite amount of time from the reference frame of infalling matter, a distant observer would see the infalling material slow and halt just above the event horizon, due to gravitational time dilation. Light from the collapsing material takes longer and longer to reach the observer, with the delay growing to infinity as the emitting material reaches the event horizon. Thus the external observer never sees the formation of the event horizon; instead, the collapsing material seems to become dimmer and increasingly red-shifted, eventually fading away. Observations of quasars at redshift z ∼ 7 {\displaystyle z\sim 7} , less than a billion years after the Big Bang, has led to investigations of other ways to form black holes. The accretion process to build supermassive black holes has a limiting rate of mass accumulation and a billion years is not enough time to reach quasar status. One suggestion is direct collapse of nearly pure hydrogen gas (low metalicity) clouds characteristic of the young universe, forming a supermassive star which collapses into a black hole. It has been suggested that seed black holes with typical masses of ~105 M☉ could have formed in this way which then could grow to ~109 M☉. However, the very large amount of gas required for direct collapse is not typically stable to fragmentation to form multiple stars. Thus another approach suggests massive star formation followed by collisions that seed massive black holes which ultimately merge to create a quasar.: 85 A neutron star in a common envelope with a regular star can accrete sufficient material to collapse to a black hole or two neutron stars can merge. These avenues for the formation of black holes are considered relatively rare. In the current epoch of the universe, conditions needed to form black holes are rare and are mostly only found in stars. However, in the early universe, conditions may have allowed for black hole formations via other means. Fluctuations of spacetime soon after the Big Bang may have formed areas that were denser then their surroundings. Initially, these regions would not have been compact enough to form a black hole, but eventually, the curvature of spacetime in the regions become large enough to cause them to collapse into a black hole. Different models for the early universe vary widely in their predictions of the scale of these fluctuations. Various models predict the creation of primordial black holes ranging from a Planck mass (~2.2×10−8 kg) to hundreds of thousands of solar masses. Primordial black holes with masses less than 1015 g would have evaporated by now due to Hawking radiation. Despite the early universe being extremely dense, it did not re-collapse into a black hole during the Big Bang, since the universe was expanding rapidly and did not have the gravitational differential necessary for black hole formation. Models for the gravitational collapse of objects of relatively constant size, such as stars, do not necessarily apply in the same way to rapidly expanding space such as the Big Bang. In principle, black holes could be formed in high-energy particle collisions that achieve sufficient density, although no such events have been detected. These hypothetical micro black holes, which could form from the collision of cosmic rays and Earth's atmosphere or in particle accelerators like the Large Hadron Collider, would not be able to aggregate additional mass. Instead, they would evaporate in about 10−25 seconds, posing no threat to the Earth. Evolution Black holes can also merge with other objects such as stars or even other black holes. This is thought to have been important, especially in the early growth of supermassive black holes, which could have formed from the aggregation of many smaller objects. The process has also been proposed as the origin of some intermediate-mass black holes. Mergers of supermassive black holes may take a long time: As a binary of supermassive black holes approach each other, most nearby stars are ejected, leaving little for the remaining black holes to gravitationally interact with that would allow them to get closer to each other. This phenomenon has been called the final parsec problem, as the distance at which this happens is usually around one parsec. When a black hole accretes matter, the gas in the inner accretion disk orbits at very high speeds because of its proximity to the black hole. The resulting friction heats the inner disk to temperatures at which it emits vast amounts of electromagnetic radiation (mainly X-rays) detectable by telescopes. By the time the matter of the disk reaches the ISCO, between 5.7% and 42% of its mass will have been converted to energy, depending on the black hole's spin. About 90% of this energy is released within about 20 black hole radii. In many cases, accretion disks are accompanied by relativistic jets that are emitted along the black hole's poles, which carry away much of the energy. The mechanism for the creation of these jets is currently not well understood, in part due to insufficient data. Many of the universe's most energetic phenomena have been attributed to the accretion of matter on black holes. Active galactic nuclei and quasars are believed to be the accretion disks of supermassive black holes. X-ray binaries are generally accepted to be binary systems in which one of the two objects is a compact object accreting matter from its companion. Ultraluminous X-ray sources may be the accretion disks of intermediate-mass black holes. At a certain rate of accretion, the outward radiation pressure will become as strong as the inward gravitational force, and the black hole should unable to accrete any faster. This limit is called the Eddington limit. However, many black holes accrete beyond this rate due to their non-spherical geometry or instabilities in the accretion disk. Accretion beyond the limit is called Super-Eddington accretion and may have been commonplace in the early universe. Stars have been observed to get torn apart by tidal forces in the immediate vicinity of supermassive black holes in galaxy nuclei, in what is known as a tidal disruption event (TDE). Some of the material from the disrupted star forms an accretion disk around the black hole, which emits observable electromagnetic radiation. The correlation between the masses of supermassive black holes in the centres of galaxies with the velocity dispersion and mass of stars in their host bulges suggests that the formation of galaxies and the formation of their central black holes are related. Black hole winds from rapid accretion, particularly when the galaxy itself is still accreting matter, can compress gas nearby, accelerating star formation. However, if the winds become too strong, the black hole may blow nearly all of the gas out of the galaxy, quenching star formation. Black hole jets may also energize nearby cavities of plasma and eject low-entropy gas from out of the galactic core, causing gas in galactic centers to be hotter than expected. If Hawking's theory of black hole radiation is correct, then black holes are expected to shrink and evaporate over time as they lose mass by the emission of photons and other particles. The temperature of this thermal spectrum (Hawking temperature) is proportional to the surface gravity of the black hole, which is inversely proportional to the mass. Hence, large black holes emit less radiation than small black holes.: Ch. 9.6 A stellar black hole of 1 M☉ has a Hawking temperature of 62 nanokelvins. This is far less than the 2.7 K temperature of the cosmic microwave background radiation. Stellar-mass or larger black holes receive more mass from the cosmic microwave background than they emit through Hawking radiation and thus will grow instead of shrinking. To have a Hawking temperature larger than 2.7 K (and be able to evaporate), a black hole would need a mass less than the Moon. Such a black hole would have a diameter of less than a tenth of a millimetre. The Hawking radiation for an astrophysical black hole is predicted to be very weak and would thus be exceedingly difficult to detect from Earth. A possible exception is the burst of gamma rays emitted in the last stage of the evaporation of primordial black holes. Searches for such flashes have proven unsuccessful and provide stringent limits on the possibility of existence of low mass primordial black holes, with modern research predicting that primordial black holes must make up less than a fraction of 10−7 of the universe's total mass. NASA's Fermi Gamma-ray Space Telescope, launched in 2008, has searched for these flashes, but has not yet found any. The properties of a black hole are constrained and interrelated by the theories that predict these properties. When based on general relativity, these relationships are called the laws of black hole mechanics. For a black hole that is not still forming or accreting matter, the zeroth law of black hole mechanics states the black hole's surface gravity is constant across the event horizon. The first law relates changes in the black hole's surface area, angular momentum, and charge to changes in its energy. The second law says the surface area of a black hole never decreases on its own. Finally, the third law says that the surface gravity of a black hole is never zero. These laws are mathematical analogs of the laws of thermodynamics. They are not equivalent, however, because, according to general relativity without quantum mechanics, a black hole can never emit radiation, and thus its temperature must always be zero.: 11 Quantum mechanics predicts that a black hole will continuously emit thermal Hawking radiation, and therefore must always have a nonzero temperature. It also predicts that all black holes have entropy which scales with their surface area. When quantum mechanics is accounted for, the laws of black hole mechanics become equivalent to the classical laws of thermodynamics. However, these conclusions are derived without a complete theory of quantum gravity, although many potential theories do predict black holes having entropy and temperature. Thus, the true quantum nature of black hole thermodynamics continues to be debated.: 29 Observational evidence Millions of black holes with around 30 solar masses derived from stellar collapse are expected to exist in the Milky Way. Even a dwarf galaxy like Draco should have hundreds. Only a few of these have been detected. By nature, black holes do not themselves emit any electromagnetic radiation other than the hypothetical Hawking radiation, so astrophysicists searching for black holes must generally rely on indirect observations. The defining characteristic of a black hole is its event horizon. The horizon itself cannot be imaged, so all other possible explanations for these indirect observations must be considered and eliminated before concluding that a black hole has been observed.: 11 The Event Horizon Telescope (EHT) is a global system of radio telescopes capable of directly observing a black hole shadow. The angular resolution of a telescope is based on its aperture and the wavelengths it is observing. Because the angular diameters of Sagittarius A* and Messier 87* in the sky are very small, a single telescope would need to be about the size of the Earth to clearly distinguish their horizons using radio wavelengths. By combining data from several different radio telescopes around the world, the Event Horizon Telescope creates an effective aperture the diameter size of the Earth. The EHT team used imaging algorithms to compute the most probable image from the data in its observations of Sagittarius A* and M87*. Gravitational-wave interferometry can be used to detect merging black holes and other compact objects. In this method, a laser beam is split down two long arms of a tunnel. The laser beams reflect off of mirrors in the tunnels and converge at the intersection of the arms, cancelling each other out. However, when a gravitational wave passes, it warps spacetime, changing the lengths of the arms themselves. Since each laser beam is now travelling a slightly different distance, they do not cancel out and produce a recognizable signal. Analysis of the signal can give scientists information about what caused the gravitational waves. Since gravitational waves are very weak, gravitational-wave observatories such as LIGO must have arms several kilometers long and carefully control for noise from Earth to be able to detect these gravitational waves. Since the first measurements in 2016, multiple gravitational waves from black holes have been detected and analyzed. The proper motions of stars near the centre of the Milky Way provide strong observational evidence that these stars are orbiting a supermassive black hole. Since 1995, astronomers have tracked the motions of 90 stars orbiting an invisible object coincident with the radio source Sagittarius A*. In 1998, by fitting the motions of the stars to Keplerian orbits, the astronomers were able to infer that Sagittarius A* must be a 2.6×106 M☉ object must be contained within a radius of 0.02 light-years. Since then, one of the stars—called S2—has completed a full orbit. From the orbital data, astronomers were able to refine the calculations of the mass of Sagittarius A* to 4.3×106 M☉, with a radius of less than 0.002 light-years. This upper limit radius is larger than the Schwarzschild radius for the estimated mass, so the combination does not prove Sagittarius A* is a black hole. Nevertheless, these observations strongly suggest that the central object is a supermassive black hole as there are no other plausible scenarios for confining so much invisible mass into such a small volume. Additionally, there is some observational evidence that this object might possess an event horizon, a feature unique to black holes. The Event Horizon Telescope image of Sagittarius A*, released in 2022, provided further confirmation that it is indeed a black hole. X-ray binaries are binary systems that emit a majority of their radiation in the X-ray part of the electromagnetic spectrum. These X-ray emissions result when a compact object accretes matter from an ordinary star. The presence of an ordinary star in such a system provides an opportunity for studying the central object and to determine if it might be a black hole. By measuring the orbital period of the binary, the distance to the binary from Earth, and the mass of the companion star, scientists can estimate the mass of the compact object. The Tolman-Oppenheimer-Volkoff limit (TOV limit) dictates the largest mass a nonrotating neutron star can be, and is estimated to be about two solar masses. While a rotating neutron star can be slightly more massive, if the compact object is much more massive than the TOV limit, it cannot be a neutron star and is generally expected to be a black hole. The first strong candidate for a black hole, Cygnus X-1, was discovered in this way by Charles Thomas Bolton, Louise Webster, and Paul Murdin in 1972. Observations of rotation broadening of the optical star reported in 1986 lead to a compact object mass estimate of 16 solar masses, with 7 solar masses as the lower bound. In 2011, this estimate was updated to 14.1±1.0 M☉ for the black hole and 19.2±1.9 M☉ for the optical stellar companion. X-ray binaries can be categorized as either low-mass or high-mass; This classification is based on the mass of the companion star, not the compact object itself. In a class of X-ray binaries called soft X-ray transients, the companion star is of relatively low mass, allowing for more accurate estimates of the black hole mass. These systems actively emit X-rays for only several months once every 10–50 years. During the period of low X-ray emission, called quiescence, the accretion disk is extremely faint, allowing detailed observation of the companion star. Numerous black hole candidates have been measured by this method. Black holes are also sometimes found in binaries with other compact objects, such as white dwarfs, neutron stars, and other black holes. The centre of nearly every galaxy contains a supermassive black hole. The close observational correlation between the mass of this hole and the velocity dispersion of the host galaxy's bulge, known as the M–sigma relation, strongly suggests a connection between the formation of the black hole and that of the galaxy itself. Astronomers use the term active galaxy to describe galaxies with unusual characteristics, such as unusual spectral line emission and very strong radio emission. Theoretical and observational studies have shown that the high levels of activity in the centers of these galaxies, regions called active galactic nuclei (AGN), may be explained by accretion onto supermassive black holes. These AGN consist of a central black hole that may be millions or billions of times more massive than the Sun, a disk of interstellar gas and dust called an accretion disk, and two jets perpendicular to the accretion disk. Although supermassive black holes are expected to be found in most AGN, only some galaxies' nuclei have been more carefully studied in attempts to both identify and measure the actual masses of the central supermassive black hole candidates. Some of the most notable galaxies with supermassive black hole candidates include the Andromeda Galaxy, Messier 32, Messier 87, the Sombrero Galaxy, and the Milky Way itself. Another way black holes can be detected is through observation of effects caused by their strong gravitational field. One such effect is gravitational lensing: The deformation of spacetime around a massive object causes light rays to be deflected, making objects behind them appear distorted. When the lensing object is a black hole, this effect can be strong enough to create multiple images of a star or other luminous source. However, the distance between the lensed images may be too small for contemporary telescopes to resolve—this phenomenon is called microlensing. Instead of seeing two images of a lensed star, astronomers see the star brighten slightly as the black hole moves towards the line of sight between the star and Earth and then return to its normal luminosity as the black hole moves away. The turn of the millennium saw the first 3 candidate detections of black holes in this way, and in January 2022, astronomers reported the first confirmed detection of a microlensing event from an isolated black hole. This was also the first determination of an isolated black hole mass, 7.1±1.3 M☉. Alternatives While there is a strong case for supermassive black holes, the model for stellar-mass black holes assumes of an upper limit for the mass of a neutron star: objects observed to have more mass are assumed to be black holes. However, the properties of extremely dense matter are poorly understood. New exotic phases of matter could allow other kinds of massive objects. Quark stars would be made up of quark matter and supported by quark degeneracy pressure, a form of degeneracy pressure even stronger than neutron degeneracy pressure. This would halt gravitational collapse at a higher mass than for a neutron star. Even stronger stars called electroweak stars would convert quarks in their cores into leptons, providing additional pressure to stop the star from collapsing. If, as some extensions of the Standard Model posit, quarks and leptons are made up of the even-smaller fundamental particles called preons, a very compact star could be supported by preon degeneracy pressure. While none of these hypothetical models can explain all of the observations of stellar black hole candidates, a Q star is the only alternative which could significantly exceed the mass limit for neutron stars and thus provide an alternative for supermassive black holes.: 12 A few theoretical objects have been conjectured to match observations of astronomical black hole candidates identically or near-identically, but which function via a different mechanism. A dark energy star would convert infalling matter into vacuum energy; This vacuum energy would be much larger than the vacuum energy of outside space, exerting outwards pressure and preventing a singularity from forming. A black star would be gravitationally collapsing slowly enough that quantum effects would keep it just on the cusp of fully collapsing into a black hole. A gravastar would consist of a very thin shell and a dark-energy interior providing outward pressure to stop the collapse into a black hole or formation of a singularity; It could even have another gravastar inside, called a 'nestar'. Open questions According to the no-hair theorem, a black hole is defined by only three parameters: its mass, charge, and angular momentum. This seems to mean that all other information about the matter that went into forming the black hole is lost, as there is no way to determine anything about the black hole from outside other than those three parameters. When black holes were thought to persist forever, this information loss was not problematic, as the information can be thought of as existing inside the black hole. However, black holes slowly evaporate by emitting Hawking radiation. This radiation does not appear to carry any additional information about the matter that formed the black hole, meaning that this information is seemingly gone forever. This is called the black hole information paradox. Theoretical studies analyzing the paradox have led to both further paradoxes and new ideas about the intersection of quantum mechanics and general relativity. While there is no consensus on the resolution of the paradox, work on the problem is expected to be important for a theory of quantum gravity.: 126 Observations of faraway galaxies have found that ultraluminous quasars, powered by supermassive black holes, existed in the early universe as far as redshift z ≥ 7 {\displaystyle z\geq 7} . These black holes have been assumed to be the products of the gravitational collapse of large population III stars. However, these stellar remnants were not massive enough to produce the quasars observed at early times without accreting beyond the Eddington limit, the theoretical maximum rate of black hole accretion. Physicists have suggested a variety of different mechanisms by which these supermassive black holes may have formed. It has been proposed that smaller black holes may have also undergone mergers to produce the observed supermassive black holes. It is also possible that they were seeded by direct-collapse black holes, in which a large cloud of hot gas avoids fragmentation that would lead to multiple stars, due to low angular momentum or heating from a nearby galaxy. Given the right circumstances, a single supermassive star forms and collapses directly into a black hole without undergoing typical stellar evolution. Additionally, these supermassive black holes in the early universe may be high-mass primordial black holes, which could have accreted further matter in the centers of galaxies. Finally, certain mechanisms allow black holes to grow faster than the theoretical Eddington limit, such as dense gas in the accretion disk limiting outward radiation pressure that prevents the black hole from accreting. However, the formation of bipolar jets prevent super-Eddington rates. In fiction Black holes have been portrayed in science fiction in a variety of ways. Even before the advent of the term itself, objects with characteristics of black holes appeared in stories such as the 1928 novel The Skylark of Space with its "black Sun" and the "hole in space" in the 1935 short story Starship Invincible. As black holes grew to public recognition in the 1960s and 1970s, they began to be featured in films as well as novels, such as Disney's The Black Hole. Black holes have also been used in works of the 21st century, such as Christopher Nolan's science fiction epic Interstellar. Authors and screenwriters have exploited the relativistic effects of black holes, particularly gravitational time dilation. For example, Interstellar features a black hole planet with a time dilation factor of over 60,000:1, while the 1977 novel Gateway depicts a spaceship approaching but never crossing the event horizon of a black hole from the perspective of an outside observer due to time dilation effects. Black holes have also been appropriated as wormholes or other methods of faster-than-light travel, such as in the 1974 novel The Forever War, where a network of black holes is used for interstellar travel. Additionally, black holes can feature as hazards to spacefarers and planets: A black hole threatens a deep-space outpost in 1978 short story The Black Hole Passes, and a binary black hole dangerously alters the orbit of a planet in the 2018 Netflix reboot of Lost in Space. Notes References Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/Chatty_Cathy] | [TOKENS: 2281] |
Contents Chatty Cathy Chatty Cathy is a pull-string "talking" doll originally created by Ruth and Elliot Handler and manufactured by the Mattel toy company from 1959 to 1965. The doll was first released in stores and appeared in television commercials beginning in 1960, with a suggested retail price of $18.00, though usually priced under $10.00 in catalog advertisements. Chatty Cathy was on the market for six years.[citation needed] After the success of Chatty Cathy, Mattel introduced "Chatty Baby" in 1962 and "Tiny Chatty Baby", "Tiny Chatty Brother", and "Charmin' Chatty" in 1963. The last doll to have the word "chatty" in its name in the 1960s was "Singin' Chatty" in 1965. Mattel trademarked the name "chatty" in the 1960s, and the boxes for Mattel talking dolls such as Drowsy, Baby Cheryl, and Tatters each had the tag-line "A Chatty Doll by Mattel". Physical look The original Chatty Cathy was designed to look like a five-year-old girl with light skin, blue eyes and blonde hair in a short bob. Brunette and auburn-haired versions of the doll were introduced in 1962 and 1963, respectively. An African-American version of the doll with a brown skin tone was also produced in 1962-63. In 1963, Chatty Cathy's hair was re-styled into what Mattel called "long twin ponytails". Mattel catalogs stated that Chatty Cathy and all the other Chatty dolls had the go-to-sleep, "lifelike decal eyes".[clarification needed] Voice Although its mouth did not move, the Chatty Cathy doll "spoke" one of eleven phrases at random when the "chatty ring" protruding from its upper back was pulled. The ring was attached to a string connected to a simple phonograph record inside the cavity behind the doll's abdomen. The record was driven by a metal coil wound by pulling the toy's string. The voice unit was designed by Jack Ryan, Mattel's head of research and development. When it arrived on the market in 1960, the doll played eleven phrases, including "I love you", "I hurt myself!" and "Please take me with you". In 1963, seven more were added to the doll's repertoire, including "Let's play school" and "May I have a cookie?", for a total of 18 phrases. Cartoon voice actress June Foray, known for the voice of Rocket "Rocky" J. Squirrel in the Rocky & Bullwinkle cartoon series and other well-known cartoon characters from the 1940s to the mid-2000s, recorded the phrases for the 1960s version of Chatty Cathy. Clothing In 1960, two outfits were available for the Chatty Cathy doll. One was a blue dress with a white eyelet overblouse, panties, crinoline, blue shoes and white socks; the other was a red velvet headband, red sunsuit with a red pinafore with an overskirt of white voile, red shoes and white socks. Other accessories included a story and comic book, a shoehorn, and a paper wrist tag that also served as a numbered warranty card. The doll and its accompanying accessories were advertised at less than $20. In 1961, the red Chatty Cathy dress was discontinued, replaced by a pink and white striped dress with a white pinafore called "Pink Peppermint Stick", which was available until 1964. Also in 1961, six extra outfits were made separately available, including "Party Dress", "Nursery School Dress", "Sleepytime Pajamas", "Playtime Shorts set", and "Party Coat". The outfits "Sunday Visit Dress" and "Sunny Day Capri Short set" came out in 1963. Production history In 1962, Mattel licensed its proprietary voice mechanism and licensed the Chatty Cathy doll to the Dee & Cee Toy Company of Canada. Dee & Cee, known as Mattel Canada by 1964, produced several Canadian versions of the dolls. Though made from the original American molds, there was a notable difference in the Canadian dolls' materials: the vinyl had a slightly glossier look, the doll's eyebrows had a higher/thinner arch on the forehead, and a different type of eye was used. These differences account for the higher prices of some Canadian Chattys among collectors. Some of the doll's phrases were different, reflecting cultural differences between Canada and the United States.[citation needed] These differences also made the doll suitable for export to other English-speaking countries.[citation needed] Dee & Cee's models had the same 11-18 phrases as the American Chatty Cathys. Dee & Cee was rumored to have sold a French-speaking Chatty Cathy, though the doll recording gives her name as "Carola". According to Chatty Cathy reseller Kathy Scott, alterations made to original Canadian Chatty Cathys make it difficult to identify which original Canadian Chatty Cathys are original French-speaking "Carola" Chatty dolls, if any. Chatty Cathy, as well as Chatty Baby and Tiny Chatty Baby, were redesigned and reissued by Mattel in 1970. The dolls were completely different in appearance from earlier Chatty dolls. Maureen McCormick, who had appeared in Chatty Cathy television commercials with future Brady Bunch co-star Eve Plumb in the 1960s, provided the voice of the new Chatty Cathy doll, which was sold for two years. All three new dolls had painted eyes, not the go-to-sleep version. In 1984, Mattel introduced Chatty Patty, which also had a different look from the other Chatty dolls; it too had painted eyes. Mattel Classics released special reproduction editions of Chatty Cathy from 1998 to 2001. These special reproductions were made to resemble the 1960 version of Chatty Cathy with go-to-sleep "lifelike decal eyes", along with the most memorable outfits, a cartoon box with a Chatty Cathy story book, a wrist tag, and a shoehorn. The 1998 models spoke the original eleven 1960s phrases in the original June Foray voice; the special package included a numbered certificate of authenticity, a wrist tag with a picture of Chatty Cathy creators Ruth and Elliot Handler, and a special letter from Ruth Handler. The special reproduction editions were sold exclusively in JCPenney stores (later in specialty doll and toy stores) and priced starting at $98.99. The models came in three well-known outfits. One of the three models had brown eyes. All the original 1998 models had blonde bob hairstyles. Mattel also sold a "Holiday" Chatty Cathy in a holiday-themed cartoon box with a tree ornament on the wrist and a newly designed holiday dress. The holiday model, the only one from 1998/99 with long curled brown hair and brown "pinwheel" type eyes, plays some original phrases as well as holiday-themed ones. All 1998/99 Chatty Cathys sold out immediately, most purchased by avid collectors, resellers, and fans of the original dolls. In 1965, Mattel licensed its proprietary voice box/mechanism to the Rosebud Doll Company in England, which produced a British "Chatty Cathy" that spoke different phrases in a British accent (the doll does not say its name is Cathy). Sold until about 1970, the dolls were made from different molds and do not resemble any of the North American Mattel Chatty Cathys. According to Kathy Scott, the British dolls came in three models: sandy blonde with tight short curls, platinum blonde with long straight hair, or long straight brown hair on a stubbier 18-inch model. In popular culture The popularity of Chatty Cathy led to many pull-string talking dolls flooding the toy industry. The same basic pull-string talking mechanisms were used in all other Mattel talking dolls and toys of the 1960s and 1970s. These included favorites like talking Bugs Bunny, Porky Pig, Mrs. Beasley, Drowsy, Herman Munster, Dr. Seuss characters, Woody Woodpecker, Mister Ed, and all the See 'n Say toys. When Mattel's Baby First Step ("the world's first walking doll") sold well upon its introduction in 1965, a talking version was released the following year. Other Mattel dolls that "learned to talk" were the Baby Tender Love line (1970), which eventually included Talking Baby Tender Love, and the Baby Beans line (1971), which spawned a Talking Baby Beans. Many dolls from the Barbie line were sold in pull-string talking versions in the late 1960s and early 1970s. "Living Doll", a 1963 episode of The Twilight Zone, features a murderous talking doll named "Talky Tina" modeled after Chatty Cathy and voiced by June Foray, the original voice of Chatty Cathy. The doll used to portray Talky Tina was produced by the Vogue Doll Company between 1959 and 1961 and marketed under the name "Brikette". The term "Chatty Cathy" can be used to refer to a particularly talkative person. In the 1987 movie Planes, Trains and Automobiles, Steve Martin scolds John Candy, saying, "It's like going on a date with a Chatty Cathy doll. I expect you have a little string on your chest, you know, that I pull out and have to snap back." In the Arrow episode "Lost Souls", Felicity Smoak refers to Green Arrow as a "Chatty Cathy" for talking to her mother too often. The How I Met Your Mother episode titled "Spoiler Alert" shows Ted dating a very talkative woman named Cathy. The "Corey's Remix" episode of That '80s Show features a scene in which Katie Howard demands that her brother Corey apologize for cutting the string from her Chatty Cathy doll when they were kids, thus making it just plain "Cathy". The character Gabby Gabby in the 2019 film Toy Story 4 was inspired by Chatty Cathy and "Talky Tina", according to director Josh Cooley. The 2007 Robot Chicken episode "Moesha Poppins" depicts a fictional Michael Moore listing the fates of several "girl toys" that faded into obscurity, ending with Chatty Cathy, whose tongue is cut out by the mafia after she witnesses a mob crime. A GEICO commercial from 2007 parodied the Chatty Cathy commercial with the dolls saying phrases about their car insurance rates. In 2007 and 2010, Hallmark released the Chatty Cathy keepsake ornament. Other media A live-action film adaptation produced by Mattel Films and Aggregate Films was announced in January 2022. See also References External links |
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Contents Backward compatibility In telecommunications and computing, backward compatibility (or backwards compatibility) is a property of an operating system, software, real-world product, or technology that allows for interoperability with an older legacy system, or with input designed for such a system. Modifying a system in a way that does not allow backward compatibility is sometimes called "breaking" backward compatibility. Such breaking usually incurs various types of costs, such as switching cost. A complementary concept is forward compatibility; a design that is forward-compatible usually has a roadmap for compatibility with future standards and products. Usage A simple example of both backward and forward compatibility is the introduction of FM radio in stereo. FM radio was initially mono, with only one audio channel represented by one signal. With the introduction of two-channel stereo FM radio, many listeners had only mono FM receivers. Forward compatibility for mono receivers with stereo signals was achieved by sending the sum of both left and right audio channels in one signal and the difference in another signal. That allows mono FM receivers to receive and decode the sum signal while ignoring the difference signal, which is necessary only for separating the audio channels. Stereo FM receivers can receive a mono signal and decode it without the need for a second signal, and they can separate a sum signal to left and right channels if both sum and difference signals are received. Without the requirement for backward compatibility, a simpler method could have been chosen. Full backward compatibility is particularly important in computer instruction set architectures, two of the most successful being the IBM 360/370/390/Zseries families of mainframes, and the Intel x86 family of microprocessors. IBM announced the first 360 models in 1964 and has continued to update the series ever since, with migration over the decades from 32-bit register/24-bit addresses to 64-bit registers and addresses. Intel announced the first Intel 8086/8088 processors in 1978, again with migrations over the decades from 16-bit to 64-bit. (The 8086/8088, in turn, were designed with easy machine-translatability of programs written for its predecessor in mind, although they were not instruction-set compatible with the 8-bit Intel 8080 processor of 1974. The Zilog Z80, however, was fully backward compatible with the Intel 8080.) Fully backward compatible processors can process the same binary executable software instructions as their predecessors, allowing the use of a newer processor without having to acquire new applications or operating systems. Similarly, the success of the Wi-Fi digital communication standard is attributed to its broad forward and backward compatibility; it became more popular than other standards that were not backward compatible. In software development, backward compatibility is a general notion of interoperation between software pieces that will not produce any errors when its functionality is invoked via API. The software is considered stable when its API that is used to invoke functions is stable across different versions. In operating systems, upgrades to newer versions are said to be backward compatible if executables and other files from the previous versions will work as usual. In compilers, backward compatibility may refer to the ability of a compiler for a newer version of the language to accept source code of programs or data that worked under the previous version. A data format is said to be backward compatible when a newer version of the program can open it without errors just like its predecessor. Tradeoffs There are several incentives for a company to implement backward compatibility. One is that it can be used to preserve older software that would have otherwise been lost when a manufacturer decides to stop supporting older hardware. Video games are the most notable examples of this, as it is most commonly discussed when discussing the value of supporting older software. The cultural impact of video games is a large part of their continued success, and some believe ignoring backward compatibility would cause these titles to disappear. Backward compatibility can also act as a selling point for newly-introduced hardware, as the existing user install base for the preceding hardware can more affordably upgrade to subsequent generations of a console. This can also help make up for the lack of titles at the launch of new systems, as users can pull from the previous console's library of games while developers transition to the new hardware. For example, the PlayStation 2's backward compatibility with the original PlayStation (PS) software discs and peripherals is considered to have been one of the key selling points for the console during its early months on the market. Moreover, studies in the mid-1990s found that even consumers who never play older games after purchasing a new system consider backward compatibility a highly desirable feature, valuing the mere ability to continue to play an existing collection of games even if they choose never to do so. In recent times, however, advancements in emulation and preservation efforts have made it much easier to play many older computer, handheld, and console video games outside of their original or intended hardware or computer specifications. Despite not being included at launch, Microsoft slowly incorporated backward compatibility for select titles on the Xbox One several years into its product life cycle. Players have racked up over a billion hours with backward-compatible games on Xbox. A large part of the success and implementation of this feature is that the hardware within newer generation consoles is both powerful and similar enough to legacy systems that older titles can be broken down and re-configured to run on the Xbox One. This program has proven incredibly popular with Xbox players and goes against the recent trend of studio-made remasters of classic titles, creating what some believe to be an important shift in console makers' strategies. The current generation of consoles such as the PlayStation 5 (PS5) and Xbox Series X/S also support this feature as well. The monetary costs of supporting old software is considered to be a large drawback to the usage of backward compatibility. The associated costs of backward compatibility are a larger bill of materials if hardware is required to support the legacy systems; increased complexity of the product that may lead to longer time to market, technological hindrances, and slowing innovation; and increased expectations from users in terms of compatibility. For video games, this also creates the risk that developers will favor developing games that are compatible with both the old and new systems, since this gives them a larger base of potential buyers, resulting in a dearth of software which uses the advanced features of the new system. Because of this, several console manufacturers phased out backward compatibility towards the end of the console generation in order to reduce cost and briefly reinvigorate sales before the arrival of newer hardware. One such example of this approach was the PlayStation 3 (PS3), where it initially featured backward compatibility with PlayStation 2 (PS2) games via the inclusion of the onboard Emotion Engine and Graphics Synthesizer hardware chips on earlier revisions but were later removed on later systems to reduce hardware costs and improve console sales, effectively eliminating PS2 backward compatibility from the console. Despite this, it is still possible to bypass some of these hardware costs. For instance, earlier PS2 systems had the core of the original PlayStation (PS1) CPU integrated into the I/O processor for dual-purpose use; it could act as either the main CPU in PS1 mode or it can up-clock itself to offload I/O in PS2 mode. The original I/O core was replaced with a PowerPC-based core in later systems to serve the same functions, emulating the same functions as the PS1 CPU core. Such an approach can backfire, however, as was the case of the Super Nintendo Entertainment System (Super NES). It opted for the more peculiar 65C816 CPU over the more popular 16-bit microprocessors on the basis that it would allow for easier backwards compatibility with the original Nintendo Entertainment System (NES) due to the 65C816's software compatibility with the 6502 CPU in emulation mode, but ultimately did not proved to be workable once the rest of the Super NES's architecture was designed. See also References External links |
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[SOURCE: https://en.wikipedia.org/wiki/HH_24-26] | [TOKENS: 281] |
Contents HH 24-26 HH 24-26 is a molecular cloud and star-forming region containing the Herbig-Haro objects HH 24, HH 25 and HH 26. This region contains the highest concentration of astrophysical jets known anywhere in the sky. The molecular cloud is located about 1400 light-years away in the L1630 dark cloud, which is part of the Orion B molecular cloud in the constellation of Orion. The region contains multiple protostars (two class 0 and one class I) and four more evolved IRAS sources. The three protostars are driving the Herbig-Haro objects in this region. Observation The L1630 dark cloud also contains NGC 2071 and the Flame Nebula. HH 24-26 is located just a few arcminutes south of Messier 78. HH 24 The image of HH 24 taken by the Hubble Space Telescope is probably the most well known image of this Herbig-Haro object. HH 24 resembles a lightsaber from the science fiction movies Star Wars and the Hubble image was published during the release of Star Wars Episode VII: The Force Awakens. HH 24 contains a class 0 protostar, which might be a proto-binary system. The disks around these objects are highly misaligned, which is a sign of turbulent fragmentation. See also References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Python_(programming_language)#cite_ref-13] | [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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[SOURCE: https://en.wikipedia.org/wiki/Ashkelon] | [TOKENS: 4246] |
Contents Ashkelon Ashkelon (/ˈæʃkəlɒn/ ASH-kə-lon; Hebrew: אשקלון, romanized: ʾAšqəlōn, IPA: [ʔaʃkeˈlon] ⓘ; Arabic: عسقلان, romanized: ʿAsqalān) or Ashqelon, is a coastal city in the Southern District of Israel on the Mediterranean coast, 50 kilometres (30 mi) south of Tel Aviv, and 13 kilometres (8 mi) north of the border with the Gaza Strip. The modern city is named after the ancient seaport of Ascalon, which was destroyed in 1270 and whose remains are on the southwestern edge of the modern metropolis. The Israeli city, first known as Migdal (Hebrew: מגדל), was founded in 1949 approximately 4 km inland from ancient Ascalon at the Palestinian town of al-Majdal (Arabic: الْمِجْدَل, romanized: al-Mijdal). Its inhabitants had been exclusively Muslims and Christians, and the area had been allocated to Palestine in the United Nations Partition Plan for Palestine; on the eve of the 1948 Arab–Israeli War the inhabitants numbered 10,000 and in October 1948, the city accommodated thousands more Palestinian refugees from nearby villages. The town was conquered by Israeli forces on 5 November 1948, by which time much of the Arab population had fled, leaving some 2700 inhabitants, of whom Israeli soldiers deported 500 in December 1948, and most of the rest were deported by 1950. Today, the city's population is almost entirely Israeli Jews. Migdal, as it was called in Hebrew, was initially repopulated by Jewish immigrants and demobilized soldiers. It was subsequently renamed multiple times, first as Migdal Gaza, Migdal Gad and Migdal Ashkelon, until in 1953, the coastal neighbourhood of Afridar was incorporated, and the name Ashkelon was adopted for the combined town. By 1961, Ashkelon was ranked 18th among Israeli urban centers with a population of 24,000. In 2023 the population of Ashkelon was 161,744, making it the third-largest city in Israel's Southern District. Etymology The name Ashkelon is probably Western Semitic, and might be connected to the triliteral root š-q-l 'to weigh', from a Semitic root ṯ-q-l, akin to Hebrew šāqal (שָקַל) or Arabic ṯiql (ثِقْل), 'weight', perhaps attesting to its importance as a center for trade. It appears in late Old Egyptian in the execration texts in a form that suggests the earliest pronunciation was ʾaθqalānu, which shifts to ʾaθqalōnu in Middle Egyptian, demonstrating the Canaanite shift in the 2nd millennium BCE. Its name appeared in Phoenician and Punic as ŠQLN (𐤔𐤒𐤋𐤍) and ʾŠQLN (𐤀𐤔𐤒𐤋𐤍). Majdal (Arabic) and Migdal (Hebrew) mean 'tower'. History The archaeological site of Ascalon, today known as Tel Ashkelon, was the oldest and largest seaport in Canaan, part of Philistia, the pentapolis (a grouping of five cities) of the Philistines, north of Gaza City and south of Jaffa. The site was an important city during Roman, Byzantine and pre-Crusades Muslim rule, and particularly during the period of the Kingdom of Jerusalem, due to its location near the coast and between the Crusader states and Egypt. The Battle of Ascalon was the last action of the First Crusade. In 1270, the Mamluk sultan Baybars ordered the fortifications and harbour of Ascalon to be destroyed. Its inhabitants moved to Majdal 'Asqalān, which was established by Baybars as a substitute 3 kilometres (1.9 mi) inland, and endowed with a magnificent congregational mosque, a marketplace and religious shrines. Established by Baybars following the destruction of Ascalon in the 13th century, the Arab village of Majdal is mentioned by historians and tourists at the end of the 15th century. In 1596, Ottoman records showed Majdal to be a large village of 559 Muslim households, making it the 7th-most-populous locality in Palestine after Safad, Jerusalem, Gaza, Nablus, Hebron and Kafr Kanna. An official Ottoman village list of about 1870 showed that Medschdel had a total of 420 houses and a population of 1175, though the population count included men only. In the 1922 census of Palestine, Majdal had a population of 5,064; 33 Christians and 5,031 Muslims, increasing in the 1931 census to 6,226 (6,166 Muslims and 41 Christians) with 172 in the suburbs (167 Muslims, 4 Christians, and one Jew). In the 1945 statistics Majdal had a population of 9,910; ninety Christians and 9,820 Muslims, with a total (urban and rural) of 43,680 dunams of land, according to an official land and population survey. 2,050 dunams were public land; all the rest was owned by Arabs. of the dunams, 2,337 were used for citrus and bananas, 2,886 were plantations and irrigable land, 35,442 for cereals, while 1,346 were built-up land. Majdal was known for the majdalawi weaving industry. The town had around 500 looms in 1909. In 1920 a British Government report estimated that there were 550 cotton looms in the town with an annual output worth 30–40 million francs. But the industry suffered from imports from Europe and by 1927 only 119 weaving establishments remained. The three major fabrics produced were "malak" (silk), 'ikhdari' (bands of red and green) and 'jiljileh' (dark red bands). These were used for festival dresses throughout Southern Palestine. Many other fabrics were produced, some with poetic names such as ji'nneh u nar ("heaven and hell"), nasheq rohoh ("breath of the soul") and abu mitayn ("father of two hundred"). In addition to agriculture, residents practiced animal husbandry which formed was an important source of income for the town. In 1943, they owned 354 heads of cattle, 168 sheep over a year old, 170 goats over a year old, 65 camels, 17 horses, 39 mules, 447 donkeys, 2966 fowls, and 808 pigeons. Majdal was occupied by the Egyptian army in the early stages of the 1948 Palestine war, along with the rest of the Gaza region, which had been allocated to the Arab State in the United Nations plan. Over the next few months, the town was subjected to Israeli air raids and shelling. All but about 1,000 of the town's residents were forced to leave by the time it was captured by Israeli forces as a sequel to Operation Yoav on 4 November 1948. General Yigal Allon ordered the expulsion of the remaining Palestinians, but the local commanders did not do so. The Arab population soon recovered to more than 2500, due mostly to refugees slipping back and also due to the transfer of Palestinians from nearby villages. Most were elderly, women, or children. During the next year or so, the Palestinians were held in a confined area surrounded by barbed wire, which became commonly known as the "ghetto". Moshe Dayan and Prime Minister David Ben-Gurion were in favor of expulsion, while Mapam and the Israeli labor union Histadrut objected. The government offered the Palestinians positive inducements to leave, including a favorable currency exchange, but also caused panic through night-time raids. The first group was deported to the Gaza Strip by truck on 17 August 1950 after an expulsion order had been served. Deportation was approved by Ben-Gurion and Dayan over the objections of Pinhas Lavon, secretary-general of the Histadrut, who envisioned the town as a productive example of equal opportunity. By October 1950, twenty Palestinian families remained, most of whom later moved to Lydda or Gaza. According to Israeli records, in total 2,333 Palestinians were transferred to the Gaza Strip, 60 to Jordan, 302 to other towns in Israel, and a small number remained in Ashkelon. Lavon argued that this operation dissipated "the last shred of trust the Arabs had in Israel, the sincerity of the State's declarations on democracy and civil equality, and the last remnant of confidence the Arab workers had in the Histadrut." Acting on an Egyptian complaint, the Egyptian-Israel Mixed Armistice Commission ruled that the Palestinians transferred from Majdal should be returned to Israel, but this was not done. Majdal was granted to Israel in the 1949 Armistice Agreements. Re-population of the recently vacated Arab dwellings by Jews had been official policy since at least December 1948, but the process began slowly. The Israeli national plan of June 1949 designated al-Majdal as the site for a regional urban center of 20,000 people. From July 1949, new immigrants and demobilized soldiers moved to the new town, increasing the Jewish population to 2,500 within six months. These early immigrants were mostly from Yemen, North Africa, and Europe. In 1949, the town was renamed Migdal Gaza, and then Migdal Gad. Soon after, it became Migdal Ashkelon. The city expanded as the population grew. In 1951, the neighborhood of Afridar was established for Jewish immigrants from South Africa, and in 1953 it was incorporated into the city. The current name Ashkelon was adopted and the town was granted local council status in 1953. In 1955, Ashkelon had more than 16,000 residents. By 1961, Ashkelon ranked 18th among Israeli urban centers with a population of 24,000. This grew to 43,000 in 1972 and 53,000 in 1983. In 2005, the population exceeded 106,000. In 1949 and 1950, three immigrant transit camps (ma'abarot) were established alongside Majdal (renamed Migdal) for Jewish refugees from Arab countries, Romania and Poland. Northwest of Migdal and the immigrant camps, on the lands of the depopulated Palestinian village of al-Jura, entrepreneur Zvi Segal, one of the signatories of Israel's Declaration of Independence, established the upscale Barnea neighborhood. A large tract of land south of Barnea was handed over to the trusteeship of the South African Zionist Federation, which established the neighborhood of Afridar. Plans for the city were drawn up in South Africa according to the garden city model. Migdal was surrounded by a broad ring of orchards. Barnea developed slowly, but Afridar grew rapidly. The first homes, built in 1951, were occupied by new Jewish immigrants from South Africa and South America, as well as some native-born Israelis. The first public housing project for residents of the transit camps, the Southern Hills Project (Hageva'ot Hadromiyot), also known as Zion Hill (Givat Zion), was built in 1952. The Sheikh Omar Hadid Brigade launched a series of attempted rocket attacks toward Ashkelon from the Gaza Strip in 2015. These included unsuccessful launches in June, August, September, and October, and one strike on September 18 that destroyed a bus and a residence but caused no reported casualties. Under a plan signed in October 2015, seven new neighborhoods comprising 32,000 housing units, a new stretch of highway, and three new highway interchanges will be built, turning Ashkelon into the sixth-largest city in Israel.[needs update] Landmarks The ancient site of Ascalon is now administered as the Ashkelon National Park. The walls that encircled the city are still visible, as well as Canaanite earth ramparts. The park contains mainly Roman, Byzantine, and Crusader ruins. The largest dog cemetery in the ancient world was discovered in Ashkelon. A Roman burial tomb two kilometres north of Ashkelon National Park was discovered in 1937. There are two burial tombs, a painted Hellenistic cave and a Roman cave. The Hellenistic cave is decorated with paintings of nymphs, water scenes, mythological figures and animals. In 1986 ruins of 4th- to 6th-century baths were found in Ashkelon. The bathhouses are believed to have been used for prostitution. The remains of nearly 100 mostly male infants were found in a sewer under the bathhouse, leading to conjectures that prostitutes had discarded their unwanted newborns there. The remains of a 4th-century Byzantine church with marble slab flooring and glass mosaic walls can be seen in the Barnea Quarter. Remains of a synagogue from this period have also been found. An 11th-century mosque, Maqam al-Imam al-Husayn, a site of pilgrimage for both Sunni and Shia Muslims,: 185–186 which had been built by the Fatimid Caliphate by Badr al-Jamali and where tradition held that the head of Mohammad's grandson Hussein ibn Ali was buried, was blown up by the Israel Defense Forces under instructions from Moshe Dayan as part of a broader programme to destroy mosques in July 1950. The area was subsequently redeveloped for a local Israeli hospital, Barzilai. After the site was re-identified on the hospital grounds, funds from Mohammed Burhanuddin, leader of a Shi'a Ismaili sect based in India, were used to construct a small marble prayer platform, which is visited by Shi'ite pilgrims from India and Pakistan. A domed structure housing the 13th-century tomb of Sheikh Awad sits atop a hill overlooking Ashkelon's northern beaches. Ashkelon Khan and Museum contains archaeological finds, among them a replica of Ashkelon's Canaanite silver calf, whose discovery was reported on the front page of The New York Times. The Outdoor Museum near the municipal cultural center displays two Roman burial coffins made of marble depicting battle and hunting scenes, and famous mythological scenes. The Ashkelon Marina, located between Delila and Bar Kochba beaches, offers a shipyard and repair services. Ashkeluna is a water-slide park on Ashkelon beach. Palestinians and Ashkelon Most of the founding members of Hamas were born in Mandatory Palestine, outside of the Gaza Strip, or have parents who were. Many of them were from villages that were in the vicinity of present-day Ashkelon, including most of the party's leaders: On 1–2 March 2008, rockets fired by Hamas from the Gaza Strip (some of them Grad rockets) hit Ashkelon, wounding seven, and causing property damage. Mayor Roni Mahatzri stated that "This is a state of war, I know no other definition for it. If it lasts a week or two, we can handle that, but we have no intention of allowing this to become part of our daily routine." In March 2008, 230 buildings and 30 cars were damaged by rocket fire on Ashkelon. On 12 May 2008, a rocket fired from the northern Gazan city of Beit Lahiya hit a shopping mall in southern Ashkelon, causing significant structural damage. According to The Jerusalem Post, four people were seriously injured and 87 were treated for shock. Fifteen people suffered minor to moderate injuries as a result of the collapsed structure. Southern District Police chief Uri Bar-Lev believed the Grad-model Katyusha rocket was manufactured in Iran. In March 2009, a Qassam rocket hit a school, destroying classrooms and injuring two people. In November 2014, the mayor, Itamar Shimoni, began a policy of discrimination against Arab workers, refusing to allow them to work on city projects to build bomb shelters for children. His discriminatory actions brought criticism from others, including Israeli Prime Minister Benjamin Netanyahu and Jerusalem mayor Nir Barkat who likened the discrimination to the anti-Semitism experienced by Jews in Europe 70 years earlier. On May 11, 2021, Hamas fired 137 rockets on Ashkelon killing 2 and injuring many others. On October 10, 2023, during the Gaza war, Abu Obaida, spokesperson for Hamas, warned all citizens of Ashkelon to evacuate before 5:00 P.M. local time via a post to his Telegram channel. Once the deadline hit, Hamas launched a barrage of missiles towards Ashkelon. Demographics In the early years, the city was primarily inhabited by Mizrahi Jews, who moved to Israel after being expelled or migrating from Muslim lands. Today, Mizrahi Jews still constitute the majority of the population. In the early 1950s, many South African Jews settled in Ashkelon, establishing the Afridar neighbourhood. They were followed by an influx of immigrants from the United Kingdom. During the 1990s, the city received additional arrivals of Ethiopian Jews and Russian Jews. Ashkelon today Ashkelon is the northern terminus for the Trans-Israel pipeline, which brings petroleum products from Eilat to an oil terminal at the port. The Ashkelon seawater reverse osmosis (SWRO) desalination plant is the largest in the world. The project was developed as a BOT (build–operate–transfer) by a consortium of three international companies: Veolia water, IDE Technologies and Elran. In March 2006, it was voted "Desalination Plant of the Year" in the Global Water Awards. Since 1992, Israel Beer Breweries has been operating in Ashkelon, brewing Carlsberg and Tuborg beer for the Israeli market. The Ashkelon Sports Arena opened in 1999. The "Jewish Eye" is a Jewish world film festival that takes place annually in Ashkelon. The festival marked its seventh year in 2010. The Breeza Music Festival has been held yearly in and around Ashkelon's amphitheatre since 1992. Most of the musical performances are free. Israel Lacrosse operates substantial youth lacrosse programs in the city and recently hosted the Turkey men's national team in Israel's first home international in 2013. There is also a museum and art gallery called Ashkelon Khan Museum located in what was the Great Mosque (Jamia al-Kabir) that was constructed by Sayf al-Din Salar in 1300. Ashkelon and environs is served by the Barzilai Medical Center, established in 1961. It was built in place of Hussein ibn Ali's 11th-century mosque, a center of Muslim pilgrimages, destroyed by the Israeli army in 1950. Situated ten kilometres (6 mi) from Gaza, the hospital has been the target of numerous Qassam rocket attacks, sometimes as many as 140 over one weekend. The hospital plays a vital role in treating wounded soldiers and terror victims. A rocket and missile-proof emergency room opened in February 2018. The city has 19 elementary schools, and nine junior high and high schools. The Ashkelon Academic College opened in 1998, and now hosts thousands of students. Harvard University operates an archaeological summer school program in Ashkelon. Twin towns – sister cities Ashkelon is twinned with: Former: Notable people See also References Bibliography External links 31°40′N 34°34′E / 31.667°N 34.567°E / 31.667; 34.567 |
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Contents URL A uniform resource locator (URL), colloquially known as web address, is a reference to a resource on the World Wide Web. A URL specifies the location of a resource on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identifier (URI), although many people use the two terms interchangeably.[a] A URL is most commonly used to reference a web page (HTTP/HTTPS) but is also used for file transfer (FTP), email (mailto), database access (JDBC), and many other applications. Most web browsers display the URL of a web page above the page in an address bar. As an example of a web page URL, https://www.example.com/index.html indicates protocol https, hostname www.example.com, and file name index.html. History The Uniform Resource Locator was defined in RFC 1738 in 1994 by Tim Berners-Lee, the inventor of the World Wide Web, and the URI working group of the Internet Engineering Task Force (IETF), as an outcome of collaboration started at the IETF Living Documents birds of a feather session in 1992. The format combines the pre-existing system of domain names (created in 1985) with file path syntax, where slashes are used to separate directory and filenames. Conventions already existed where server names could be prefixed to complete file paths, preceded by a double slash (//). Berners-Lee later expressed regret at the use of dots to separate the parts of the domain name within URIs, wishing he had used slashes throughout, and also said that, given the colon following the first component of a URI, the two slashes before the domain name were unnecessary. Early WorldWideWeb collaborators, including Berners-Lee, originally proposed the use of UDIs: Universal Document Identifiers. An early (1993) draft of the HTML Specification referred to "Universal" Resource Locators. This was dropped some time between June 1994 and October 1994. In his book Weaving the Web, Berners-Lee emphasizes his preference for the original inclusion of "universal" in the expansion rather than the word "uniform", to which it was later changed, and he gives a brief account of the contention that led to the change. Syntax Every HTTP URL conforms to the syntax of a generic URI. The URI generic syntax consists of five components organized hierarchically in order of decreasing significance from left to right:: §3 A component is undefined if it has an associated delimiter and the delimiter does not appear in the URI; the scheme and path components are always defined.: §5.2.1 A component is empty if it has no characters; the scheme component is always non-empty.: §3 The authority component consists of subcomponents: This is represented in a syntax diagram as: The URI comprises: A web browser will usually dereference a URL by performing an HTTP request to the specified host, by default on port number 80. URLs using the https scheme require that requests and responses be made over a secure connection to the website. Internationalized URL Internet users are distributed throughout the world using a wide variety of languages and alphabets, and expect to be able to create URLs in their own local alphabets. An Internationalized Resource Identifier (IRI) is a form of URL that includes Unicode characters. All modern browsers support IRIs. The parts of the URL requiring special treatment for different alphabets are the domain name and path. The domain name in the IRI is known as an Internationalized Domain Name (IDN). Web and Internet software automatically convert the domain name into punycode usable by the Domain Name System; for example, the Chinese URL http://例子.卷筒纸 becomes http://xn--fsqu00a.xn--3lr804guic/. The xn-- indicates that the character was not originally ASCII. The URL path name can also be specified by the user in the local writing system. If not already encoded, it is converted to UTF-8, and any characters not part of the basic URL character set are escaped as hexadecimal using percent-encoding; for example, the Japanese URL http://example.com/引き割り.html becomes http://example.com/%E5%BC%95%E3%81%8D%E5%89%B2%E3%82%8A.html. The target computer decodes the address and displays the page. Protocol-relative URLs Protocol-relative links (PRL), also known as protocol-relative URLs (PRURL), are URLs that have no protocol specified. For example, //example.com will use the protocol of the current page, typically HTTP or HTTPS. See also Notes Citations References External links |
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Contents Meta Platforms Meta Platforms, Inc. (doing business as Meta) is an American multinational technology company headquartered in Menlo Park, California. Meta owns and operates several prominent social media platforms and communication services, including Facebook, Instagram, WhatsApp, Messenger, Threads and Manus. The company also operates an advertising network for its own sites and third parties; as of 2023[update], advertising accounted for 97.8 percent of its total revenue. Meta has been described as a part of Big Tech, which refers to the largest six tech companies in the United States, Alphabet (Google), Amazon, Apple, Meta (Facebook), Microsoft, and Nvidia, which are also the largest companies in the world by market capitalization. The company was originally established in 2004 as TheFacebook, Inc., and was renamed Facebook, Inc. in 2005. In 2021, it rebranded as Meta Platforms, Inc. to reflect a strategic shift toward developing the metaverse—an interconnected digital ecosystem spanning virtual and augmented reality technologies. In 2023, Meta was ranked 31st on the Forbes Global 2000 list of the world's largest public companies. As of 2022, it was the world's third-largest spender on research and development, with R&D expenses totaling US$35.3 billion. History Facebook filed for an initial public offering (IPO) on January 1, 2012. The preliminary prospectus stated that the company sought to raise $5 billion, had 845 million monthly active users, and a website accruing 2.7 billion likes and comments daily. After the IPO, Zuckerberg would retain 22% of the total shares and 57% of the total voting power in Facebook. Underwriters valued the shares at $38 each, valuing the company at $104 billion, the largest valuation yet for a newly public company. On May 16, one day before the IPO, Facebook announced it would sell 25% more shares than originally planned due to high demand. The IPO raised $16 billion, making it the third-largest in US history (slightly ahead of AT&T Mobility and behind only General Motors and Visa). The stock price left the company with a higher market capitalization than all but a few U.S. corporations—surpassing heavyweights such as Amazon, McDonald's, Disney, and Kraft Foods—and made Zuckerberg's stock worth $19 billion. The New York Times stated that the offering overcame questions about Facebook's difficulties in attracting advertisers to transform the company into a "must-own stock". Jimmy Lee of JPMorgan Chase described it as "the next great blue-chip". Writers at TechCrunch, on the other hand, expressed skepticism, stating, "That's a big multiple to live up to, and Facebook will likely need to add bold new revenue streams to justify the mammoth valuation." Trading in the stock, which began on May 18, was delayed that day due to technical problems with the Nasdaq exchange. The stock struggled to stay above the IPO price for most of the day, forcing underwriters to buy back shares to support the price. At the closing bell, shares were valued at $38.23, only $0.23 above the IPO price and down $3.82 from the opening bell value. The opening was widely described by the financial press as a disappointment. The stock set a new record for trading volume of an IPO. On May 25, 2012, the stock ended its first full week of trading at $31.91, a 16.5% decline. On May 22, 2012, regulators from Wall Street's Financial Industry Regulatory Authority announced that they had begun to investigate whether banks underwriting Facebook had improperly shared information only with select clients rather than the general public. Massachusetts Secretary of State William F. Galvin subpoenaed Morgan Stanley over the same issue. The allegations sparked "fury" among some investors and led to the immediate filing of several lawsuits, one of them a class action suit claiming more than $2.5 billion in losses due to the IPO. Bloomberg estimated that retail investors may have lost approximately $630 million on Facebook stock since its debut. S&P Global Ratings added Facebook to its S&P 500 index on December 21, 2013. On May 2, 2014, Zuckerberg announced that the company would be changing its internal motto from "Move fast and break things" to "Move fast with stable infrastructure". The earlier motto had been described as Zuckerberg's "prime directive to his developers and team" in a 2009 interview in Business Insider, in which he also said, "Unless you are breaking stuff, you are not moving fast enough." In November 2016, Facebook announced the Microsoft Windows client of gaming service Facebook Gameroom, formerly Facebook Games Arcade, at the Unity Technologies developers conference. The client allows Facebook users to play "native" games in addition to its web games. The service was closed in June 2021. Lasso was a short-video sharing app from Facebook similar to TikTok that was launched on iOS and Android in 2018 and was aimed at teenagers. On July 2, 2020, Facebook announced that Lasso would be shutting down on July 10. In 2018, the Oculus lead Jason Rubin sent his 50-page vision document titled "The Metaverse" to Facebook's leadership. In the document, Rubin acknowledged that Facebook's virtual reality business had not caught on as expected, despite the hundreds of millions of dollars spent on content for early adopters. He also urged the company to execute fast and invest heavily in the vision, to shut out HTC, Apple, Google and other competitors in the VR space. Regarding other players' participation in the metaverse vision, he called for the company to build the "metaverse" to prevent their competitors from "being in the VR business in a meaningful way at all". In May 2019, Facebook founded Libra Networks, reportedly to develop their own stablecoin cryptocurrency. Later, it was reported that Libra was being supported by financial companies such as Visa, Mastercard, PayPal and Uber. The consortium of companies was expected to pool in $10 million each to fund the launch of the cryptocurrency coin named Libra. Depending on when it would receive approval from the Swiss Financial Market Supervisory authority to operate as a payments service, the Libra Association had planned to launch a limited format cryptocurrency in 2021. Libra was renamed Diem, before being shut down and sold in January 2022 after backlash from Swiss government regulators and the public. During the COVID-19 pandemic, the use of online services, including Facebook, grew globally. Zuckerberg predicted this would be a "permanent acceleration" that would continue after the pandemic. Facebook hired aggressively, growing from 48,268 employees in March 2020 to more than 87,000 by September 2022. Following a period of intense scrutiny and damaging whistleblower leaks, news started to emerge on October 21, 2021 about Facebook's plan to rebrand the company and change its name. In the Q3 2021 earnings call on October 25, Mark Zuckerberg discussed the ongoing criticism of the company's social services and the way it operates, and pointed to the pivoting efforts to building the metaverse – without mentioning the rebranding and the name change. The metaverse vision and the name change from Facebook, Inc. to Meta Platforms was introduced at Facebook Connect on October 28, 2021. Based on Facebook's PR campaign, the name change reflects the company's shifting long term focus of building the metaverse, a digital extension of the physical world by social media, virtual reality and augmented reality features. "Meta" had been registered as a trademark in the United States in 2018 (after an initial filing in 2015) for marketing, advertising, and computer services, by a Canadian company that provided big data analysis of scientific literature. This company was acquired in 2017 by the Chan Zuckerberg Initiative (CZI), a foundation established by Zuckerberg and his wife, Priscilla Chan, and became one of their projects. Following the rebranding announcement, CZI announced that it had already decided to deprioritize the earlier Meta project, thus it would be transferring its rights to the name to Meta Platforms, and the previous project would end in 2022. Soon after the rebranding, in early February 2022, Meta reported a greater-than-expected decline in profits in the fourth quarter of 2021. It reported no growth in monthly users, and indicated it expected revenue growth to stall. It also expected measures taken by Apple Inc. to protect user privacy to cost it some $10 billion in advertisement revenue, an amount equal to roughly 8% of its revenue for 2021. In meeting with Meta staff the day after earnings were reported, Zuckerberg blamed competition for user attention, particularly from video-based apps such as TikTok. The 27% reduction in the company's share price which occurred in reaction to the news eliminated some $230 billion of value from Meta's market capitalization. Bloomberg described the decline as "an epic rout that, in its sheer scale, is unlike anything Wall Street or Silicon Valley has ever seen". Zuckerberg's net worth fell by as much as $31 billion. Zuckerberg owns 13% of Meta, and the holding makes up the bulk of his wealth. According to published reports by Bloomberg on March 30, 2022, Meta turned over data such as phone numbers, physical addresses, and IP addresses to hackers posing as law enforcement officials using forged documents. The law enforcement requests sometimes included forged signatures of real or fictional officials. When asked about the allegations, a Meta representative said, "We review every data request for legal sufficiency and use advanced systems and processes to validate law enforcement requests and detect abuse." In June 2022, Sheryl Sandberg, the chief operating officer of 14 years, announced she would step down that year. Zuckerberg said that Javier Olivan would replace Sandberg, though in a “more traditional” role. In March 2022, Meta (except Meta-owned WhatsApp) and Instagram were banned in Russia and added to the Russian list of terrorist and extremist organizations for alleged Russophobia and hate speech (up to genocidal calls) amid the ongoing Russian invasion of Ukraine. Meta appealed against the ban, but it was upheld by a Moscow court in June of the same year. Also in March 2022, Meta and Italian eyewear giant Luxottica released Ray-Ban Stories, a series of smartglasses which could play music and take pictures. Meta and Luxottica parent company EssilorLuxottica declined to disclose sales on the line of products as of September 2022, though Meta has expressed satisfaction with its customer feedback. In July 2022, Meta saw its first year-on-year revenue decline when its total revenue slipped by 1% to $28.8bn. Analysts and journalists accredited the loss to its advertising business, which has been limited by Apple's app tracking transparency feature and the number of people who have opted not to be tracked by Meta apps. Zuckerberg also accredited the decline to increasing competition from TikTok. On October 27, 2022, Meta's market value dropped to $268 billion, a loss of around $700 billion compared to 2021, and its shares fell by 24%. It lost its spot among the top 20 US companies by market cap, despite reaching the top 5 in the previous year. In November 2022, Meta laid off 11,000 employees, 13% of its workforce. Zuckerberg said the decision to aggressively increase Meta's investments had been a mistake, as he had wrongly predicted that the surge in e-commerce would last beyond the COVID-19 pandemic. He also attributed the decline to increased competition, a global economic downturn and "ads signal loss". Plans to lay off a further 10,000 employees began in April 2023. The layoffs were part of a general downturn in the technology industry, alongside layoffs by companies including Google, Amazon, Tesla, Snap, Twitter and Lyft. Starting from 2022, Meta scrambled to catch up to other tech companies in adopting specialized artificial intelligence hardware and software. It had been using less expensive CPUs instead of GPUs for AI work, but that approach turned out to be less efficient. The company gifted the Inter-university Consortium for Political and Social Research $1.3 million to finance the Social Media Archive's aim to make their data available to social science research. In 2023, Ireland's Data Protection Commissioner imposed a record EUR 1.2 billion fine on Meta for transferring data from Europe to the United States without adequate protections for EU citizens.: 250 In March 2023, Meta announced a new round of layoffs that would cut 10,000 employees and close 5,000 open positions to make the company more efficient. Meta revenue surpassed analyst expectations for the first quarter of 2023 after announcing that it was increasing its focus on AI. On July 6, Meta launched a new app, Threads, a competitor to Twitter. Meta announced its artificial intelligence model Llama 2 in July 2023, available for commercial use via partnerships with major cloud providers like Microsoft. It was the first project to be unveiled out of Meta's generative AI group after it was set up in February. It would not charge access or usage but instead operate with an open-source model to allow Meta to ascertain what improvements need to be made. Prior to this announcement, Meta said it had no plans to release Llama 2 for commercial use. An earlier version of Llama was released to academics. In August 2023, Meta announced its permanent removal of news content from Facebook and Instagram in Canada due to the Online News Act, which requires Canadian news outlets to be compensated for content shared on its platform. The Online News Act was in effect by year-end, but Meta will not participate in the regulatory process. In October 2023, Zuckerberg said that AI would be Meta's biggest investment area in 2024. Meta finished 2023 as one of the best-performing technology stocks of the year, with its share price up 150 percent. Its stock reached an all-time high in January 2024, bringing Meta within 2% of achieving $1 trillion market capitalization. In November 2023 Meta Platforms launched an ad-free service in Europe, allowing subscribers to opt-out of personal data being collected for targeted advertising. A group of 28 European organizations, including Max Schrems' advocacy group NOYB, the Irish Council for Civil Liberties, Wikimedia Europe, and the Electronic Privacy Information Center, signed a 2024 letter to the European Data Protection Board (EDPB) expressing concern that this subscriber model would undermine privacy protections, specifically GDPR data protection standards. Meta removed the Facebook and Instagram accounts of Iran's Supreme Leader Ali Khamenei in February 2024, citing repeated violations of its Dangerous Organizations & Individuals policy. As of March, Meta was under investigation by the FDA for alleged use of their social media platforms to sell illegal drugs. On 16 May 2024, the European Commission began an investigation into Meta over concerns related to child safety. In May 2023, Iraqi social media influencer Esaa Ahmed-Adnan encountered a troubling issue when Instagram removed his posts, citing false copyright violations despite his content being original and free from copyrighted material. He discovered that extortionists were behind these takedowns, offering to restore his content for $3,000 or provide ongoing protection for $1,000 per month. This scam, exploiting Meta’s rights management tools, became widespread in the Middle East, revealing a gap in Meta’s enforcement in developing regions. An Iraqi nonprofit Tech4Peace’s founder, Aws al-Saadi helped Ahmed-Adnan and others, but the restoration process was slow, leading to significant financial losses for many victims, including prominent figures like Ammar al-Hakim. This situation highlighted Meta’s challenges in balancing global growth with effective content moderation and protection. On 16 September 2024, Meta announced it had banned Russian state media outlets from its platforms worldwide due to concerns about "foreign interference activity." This decision followed allegations that RT and its employees funneled $10 million through shell companies to secretly fund influence campaigns on various social media channels. Meta's actions were part of a broader effort to counter Russian covert influence operations, which had intensified since the invasion. At its 2024 Connect conference, Meta presented Orion, its first pair of augmented reality glasses. Though Orion was originally intended to be sold to consumers, the manufacturing process turned out to be too complex and expensive. Instead, the company pivoted to producing a small number of the glasses to be used internally. On 4 October 2024, Meta announced about its new AI model called Movie Gen, capable of generating realistic video and audio clips based on user prompts. Meta stated it would not release Movie Gen for open development, preferring to collaborate directly with content creators and integrate it into its products by the following year. The model was built using a combination of licensed and publicly available datasets. On October 31, 2024, ProPublica published an investigation into deceptive political advertisement scams that sometimes use hundreds of hijacked profiles and facebook pages run by organized networks of scammers. The authors cited spotty enforcement by Meta as a major reason for the extent of the issue. In November 2024, TechCrunch reported that Meta were considering building a $10bn global underwater cable spanning 25,000 miles. In the same month, Meta closed down 2 million accounts on Facebook and Instagram that were linked to scam centers in Myanmar, Laos, Cambodia, the Philippines, and the United Arab Emirates doing pig butchering scams. In December 2024, Meta announced that, beginning February 2025, they would require advertisers to run ads about financial services in Australia to verify information about who are the beneficiary and the payer in a bid to regulate scams. On December 4, 2024, Meta announced it will invest US$10 billion for its largest AI data center in northeast Louisiana, powered by natural gas facilities. On the 11th of that month, Meta experienced a global outage, impacting accounts on all of their social media and messaging applications. Outage reports from DownDetector reached 70,000+ and 100,000+ within minutes for Instagram and Facebook, respectively. In January 2025, Meta announced plans to roll back its diversity, equity, and inclusion (DEI) initiatives, citing shifts in the "legal and policy landscape" in the United States following the 2024 presidential election. The decision followed reports that CEO Mark Zuckerberg sought to align the company more closely with the incoming Trump administration, including changes to content moderation policies and executive leadership. The new content moderation policies continued to bar insults about a person's intellect or mental illness, but made an exception to allow calling LGBTQ people mentally ill because they are gay or transgender. Later that month, Meta agreed to pay $25 million to settle a 2021 lawsuit brought by Donald Trump for suspending his social media accounts after the January 6 riots. Changes to Meta's moderation policies were controversial among its oversight board, with a significant divide in opinion between the board's US conservatives and its global members. In June 2025, Meta Platforms Inc. has decided to make a multibillion-dollar investment into artificial intelligence startup Scale AI. The financing could exceed $10 billion in value which would make it one of the largest private company funding events of all time. In October 2025, it was announced that Meta would be laying off 600 employees in the artificial intelligence unit to perform better and simpler. They referred to their AI unit as "bloated" and are seeking to trim down the department. This mass layoff is going to impact Meta’s AI infrastructure units, Fundamental Artificial Intelligence Research unit (FAIR) and other product-related positions. Mergers and acquisitions Meta has acquired multiple companies (often identified as talent acquisitions). One of its first major acquisitions was in April 2012, when it acquired Instagram for approximately US$1 billion in cash and stock. In October 2013, Facebook, Inc. acquired Onavo, an Israeli mobile web analytics company. In February 2014, Facebook, Inc. announced it would buy mobile messaging company WhatsApp for US$19 billion in cash and stock. The acquisition was completed on October 6. Later that year, Facebook bought Oculus VR for $2.3 billion in cash and stock, which released its first consumer virtual reality headset in 2016. In late November 2019, Facebook, Inc. announced the acquisition of the game developer Beat Games, responsible for developing one of that year's most popular VR games, Beat Saber. In Late 2022, after Facebook Inc rebranded to Meta Platforms Inc, Oculus was rebranded to Meta Quest. In May 2020, Facebook, Inc. announced it had acquired Giphy for a reported cash price of $400 million. It will be integrated with the Instagram team. However, in August 2021, UK's Competition and Markets Authority (CMA) stated that Facebook, Inc. might have to sell Giphy, after an investigation found that the deal between the two companies would harm competition in display advertising market. Facebook, Inc. was fined $70 million by CMA for deliberately failing to report all information regarding the acquisition and the ongoing antitrust investigation. In October 2022, the CMA ruled for a second time that Meta be required to divest Giphy, stating that Meta already controls half of the advertising in the UK. Meta agreed to the sale, though it stated that it disagrees with the decision itself. In May 2023, Giphy was divested to Shutterstock for $53 million. In November 2020, Facebook, Inc. announced that it planned to purchase the customer-service platform and chatbot specialist startup Kustomer to promote companies to use their platform for business. It has been reported that Kustomer valued at slightly over $1 billion. The deal was closed in February 2022 after regulatory approval. In September 2022, Meta acquired Lofelt, a Berlin-based haptic tech startup. In December 2025, it was announced Meta had acquired the AI-wearables startup, Limitless. In the same month, they also acquired another AI startup, Manus AI, for $2 billion. Manus announced in December that its platform had achieved $100mm in recurring revenue just 8 months after its launch and Meta said it will scale the platform to many other businesses. In January 2026, it was announced Meta proposed acquisition of Manus was undergoing preliminary scrutiny by Chinese regulators. The examination concerns the cross-border transfer of artificial intelligence technology developed in China. Lobbying In 2020, Facebook, Inc. spent $19.7 million on lobbying, hiring 79 lobbyists. In 2019, it had spent $16.7 million on lobbying and had a team of 71 lobbyists, up from $12.6 million and 51 lobbyists in 2018. Facebook was the largest spender of lobbying money among the Big Tech companies in 2020. The lobbying team includes top congressional aide John Branscome, who was hired in September 2021, to help the company fend off threats from Democratic lawmakers and the Biden administration. In December 2024, Meta donated $1 million to the inauguration fund for then-President-elect Donald Trump. In 2025, Meta was listed among the donors funding the construction of the White House State Ballroom. Partnerships February 2026, Meta announced a long-term partnership with Nvidia. Censorship In August 2024, Mark Zuckerberg sent a letter to Jim Jordan indicating that during the COVID-19 pandemic the Biden administration repeatedly asked Meta to limit certain COVID-19 content, including humor and satire, on Facebook and Instagram. In 2016 Meta hired Jordana Cutler, formerly an employee at the Israeli Embassy to the United States, as its policy chief for Israel and the Jewish Diaspora. In this role, Cutler pushed for the censorship of accounts belonging to Students for Justice in Palestine chapters in the United States. Critics have said that Cutler's position gives the Israeli government an undue influence over Meta policy, and that few countries have such high levels of contact with Meta policymakers. Following the election of Donald Trump in 2025, various sources noted possible censorship related to the Democratic Party on Instagram and other Meta platforms. In February 2025, a Meta rep flagged journalist Gil Duran's article and other "critiques of tech industry figures" as spam or sensitive content, limiting their reach. In March 2025, Meta attempted to block former employee Sarah Wynn-Williams from promoting or further distributing her memoir, Careless People, that includes allegations of unaddressed sexual harassment in the workplace by senior executives. The New York Times reports that the arbitration is among Meta's most forcible attempts to repudiate a former employee's account of workplace dynamics. Publisher Macmillan reacted to the ruling by the Emergency International Arbitral Tribunal by stating that it will ignore its provisions. As of 15 March 2025[update], hardback and digital versions of Careless People were being offered for sale by major online retailers. From October 2025, Meta began removing and restricting access for accounts related to LGBTQ, reproductive health and abortion information pages on its platforms. Martha Dimitratou, executive director of Repro Uncensored, called Meta's shadow-banning of these issues "One of the biggest waves of censorship we are seeing". Disinformation concerns Since its inception, Meta has been accused of being a host for fake news and misinformation. In the wake of the 2016 United States presidential election, Zuckerberg began to take steps to eliminate the prevalence of fake news, as the platform had been criticized for its potential influence on the outcome of the election. The company initially partnered with ABC News, the Associated Press, FactCheck.org, Snopes and PolitiFact for its fact-checking initiative; as of 2018, it had over 40 fact-checking partners across the world, including The Weekly Standard. A May 2017 review by The Guardian found that the platform's fact-checking initiatives of partnering with third-party fact-checkers and publicly flagging fake news were regularly ineffective, and appeared to be having minimal impact in some cases. In 2018, journalists working as fact-checkers for the company criticized the partnership, stating that it had produced minimal results and that the company had ignored their concerns. In 2024 Meta's decision to continue to disseminate a falsified video of US president Joe Biden, even after it had been proven to be fake, attracted criticism and concern. In January 2025, Meta ended its use of third-party fact-checkers in favor of a user-run community notes system similar to the one used on X. While Zuckerberg supported these changes, saying that the amount of censorship on the platform was excessive, the decision received criticism by fact-checking institutions, stating that the changes would make it more difficult for users to identify misinformation. Meta also faced criticism for weakening its policies on hate speech that were designed to protect minorities and LGBTQ+ individuals from bullying and discrimination. While moving its content review teams from California to Texas, Meta changed their hateful conduct policy to eliminate restrictions on anti-LGBT and anti-immigrant hate speech, as well as explicitly allowing users to accuse LGBT people of being mentally ill or abnormal based on their sexual orientation or gender identity. In January 2025, Meta faced significant criticism for its role in removing LGBTQ+ content from its platforms, amid its broader efforts to address anti-LGBTQ+ hate speech. The removal of LGBTQ+ themes was noted as part of the wider crackdown on content deemed to violate its community guidelines. Meta's content moderation policies, which were designed to combat harmful speech and protect users from discrimination, inadvertently led to the removal or restriction of LGBTQ+ content, particularly posts highlighting LGBTQ+ identities, support, or political issues. According to reports, LGBTQ+ posts, including those that simply celebrated pride or advocated for LGBTQ+ rights, were flagged and removed for reasons that some critics argue were vague or inconsistently applied. Many LGBTQ+ activists and users on Meta's platforms expressed concern that such actions stifled visibility and expression, potentially isolating LGBTQ+ individuals and communities, especially in spaces that were historically important for outreach and support. Lawsuits Numerous lawsuits have been filed against the company, both when it was known as Facebook, Inc., and as Meta Platforms. In March 2020, the Office of the Australian Information Commissioner (OAIC) sued Facebook, for significant and persistent infringements of the rule on privacy involving the Cambridge Analytica fiasco. Every violation of the Privacy Act is subject to a theoretical cumulative liability of $1.7 million. The OAIC estimated that a total of 311,127 Australians had been exposed. On December 8, 2020, the U.S. Federal Trade Commission and 46 states (excluding Alabama, Georgia, South Carolina, and South Dakota), the District of Columbia and the territory of Guam, launched Federal Trade Commission v. Facebook as an antitrust lawsuit against Facebook. The lawsuit concerns Facebook's acquisition of two competitors—Instagram and WhatsApp—and the ensuing monopolistic situation. FTC alleges that Facebook holds monopolistic power in the U.S. social networking market and seeks to force the company to divest from Instagram and WhatsApp to break up the conglomerate. William Kovacic, a former chairman of the Federal Trade Commission, argued the case will be difficult to win as it would require the government to create a counterfactual argument of an internet where the Facebook-WhatsApp-Instagram entity did not exist, and prove that harmed competition or consumers. In November 2025, it was ruled that Meta did not violate antitrust laws and holds no monopoly in the market. On December 24, 2021, a court in Russia fined Meta for $27 million after the company declined to remove unspecified banned content. The fine was reportedly tied to the company's annual revenue in the country. In May 2022, a lawsuit was filed in Kenya against Meta and its local outsourcing company Sama. Allegedly, Meta has poor working conditions in Kenya for workers moderating Facebook posts. According to the lawsuit, 260 screeners were declared redundant with confusing reasoning. The lawsuit seeks financial compensation and an order that outsourced moderators be given the same health benefits and pay scale as Meta employees. In June 2022, 8 lawsuits were filed across the U.S. over the allege that excessive exposure to platforms including Facebook and Instagram has led to attempted or actual suicides, eating disorders and sleeplessness, among other issues. The litigation follows a former Facebook employee's testimony in Congress that the company refused to take responsibility. The company noted that tools have been developed for parents to keep track of their children's activity on Instagram and set time limits, in addition to Meta's "Take a break" reminders. In addition, the company is providing resources specific to eating disorders as well as developing AI to prevent children under the age of 13 signing up for Facebook or Instagram. In June 2022, Meta settled a lawsuit with the US Department of Justice. The lawsuit, which was filed in 2019, alleged that the company enabled housing discrimination through targeted advertising, as it allowed homeowners and landlords to run housing ads excluding people based on sex, race, religion, and other characteristics. The U.S. Department of Justice stated that this was in violation of the Fair Housing Act. Meta was handed a penalty of $115,054 and given until December 31, 2022, to shadow the algorithm tool. In January 2023, Meta was fined €390 million for violations of the European Union General Data Protection Regulation. In May 2023, the European Data Protection Board fined Meta a record €1.2 billion for breaching European Union data privacy laws by transferring personal data of Facebook users to servers in the U.S. In July 2024, Meta agreed to pay the state of Texas US$1.4 billion to settle a lawsuit brought by Texas Attorney General Ken Paxton accusing the company of collecting users' biometric data without consent, setting a record for the largest privacy-related settlement ever obtained by a state attorney general. In October 2024, Meta Platforms faced lawsuits in Japan from 30 plaintiffs who claimed they were defrauded by fake investment ads on Facebook and Instagram, featuring false celebrity endorsements. The plaintiffs are seeking approximately $2.8 million in damages. In April 2025, the Kenyan High Court ruled that a US$2.4 billion lawsuit in which three plaintiffs claim that Facebook inflamed civil violence in Ethiopia in 2021 could proceed. In April 2025, Meta was fined €200 million ($230 million) for breaking the Digital Markets Act, by imposing a “consent or pay” system that forces users to either allow their personal data to be used to target advertisements, or pay a subscription fee for advertising-free versions of Facebook and Instagram. In late April 2025, a case was filed against Meta in Ghana over the alleged psychological distress experienced by content moderators employed to take down disturbing social media content including depictions of murders, extreme violence and child sexual abuse. Meta moved the moderation service to the Ghanaian capital of Accra after legal issues in the previous location Kenya. The new moderation company is Teleperformance, a multinational corporation with a history of worker's rights violation. Reports suggests the conditions are worse here than in the previous Kenyan location, with many workers afraid of speaking out due to fear of returning to conflict zones. Workers reported developing mental illnesses, attempted suicides, and low pay. In 26 January 2026, a New Mexico state court case was filed, suggesting that Mark Zuckerberg approved allowing minors to access artificial intelligence chatbot companions that safety staffers warned were capable of sexual interactions. In 2020, the company UReputation, which had been involved in several cases concerning the management of digital armies[clarification needed], filed a lawsuit against Facebook, accusing it of unlawfully transmitting personal data to third parties. Legal actions were initiated in Tunisia, France, and the United States. In 2025, the United States District court for the Northern District of Georgia approved a discovery procedure, allowing UReputation to access documents and evidence held by Meta. Structure Meta's key management consists of: As of October 2022[update], Meta had 83,553 employees worldwide. As of June 2024[update], Meta's board consisted of the following directors; Meta Platforms is mainly owned by institutional investors, who hold around 80% of all shares. Insiders control the majority of voting shares. The three largest individual investors in 2024 were Mark Zuckerberg, Sheryl Sandberg and Christopher K. Cox. The largest shareholders in late 2024/early 2025 were: Roger McNamee, an early Facebook investor and Zuckerberg's former mentor, said Facebook had "the most centralized decision-making structure I have ever encountered in a large company". Facebook co-founder Chris Hughes has stated that chief executive officer Mark Zuckerberg has too much power, that the company is now a monopoly, and that, as a result, it should be split into multiple smaller companies. In an op-ed in The New York Times, Hughes said he was concerned that Zuckerberg had surrounded himself with a team that did not challenge him, and that it is the U.S. government's job to hold him accountable and curb his "unchecked power". He also said that "Mark's power is unprecedented and un-American." Several U.S. politicians agreed with Hughes. European Union Commissioner for Competition Margrethe Vestager stated that splitting Facebook should be done only as "a remedy of the very last resort", and that it would not solve Facebook's underlying problems. Revenue Facebook ranked No. 34 in the 2020 Fortune 500 list of the largest United States corporations by revenue, with almost $86 billion in revenue most of it coming from advertising. One analysis of 2017 data determined that the company earned US$20.21 per user from advertising. According to New York, since its rebranding, Meta has reportedly lost $500 billion as a result of new privacy measures put in place by companies such as Apple and Google which prevents Meta from gathering users' data. In February 2015, Facebook announced it had reached two million active advertisers, with most of the gain coming from small businesses. An active advertiser was defined as an entity that had advertised on the Facebook platform in the last 28 days. In March 2016, Facebook announced it had reached three million active advertisers with more than 70% from outside the United States. Prices for advertising follow a variable pricing model based on auctioning ad placements, and potential engagement levels of the advertisement itself. Similar to other online advertising platforms like Google and Twitter, targeting of advertisements is one of the chief merits of digital advertising compared to traditional media. Marketing on Meta is employed through two methods based on the viewing habits, likes and shares, and purchasing data of the audience, namely targeted audiences and "look alike" audiences. The U.S. IRS challenged the valuation Facebook used when it transferred IP from the U.S. to Facebook Ireland (now Meta Platforms Ireland) in 2010 (which Facebook Ireland then revalued higher before charging out), as it was building its double Irish tax structure. The case is ongoing and Meta faces a potential fine of $3–5bn. The U.S. Tax Cuts and Jobs Act of 2017 changed Facebook's global tax calculations. Meta Platforms Ireland is subject to the U.S. GILTI tax of 10.5% on global intangible profits (i.e. Irish profits). On the basis that Meta Platforms Ireland Limited is paying some tax, the effective minimum US tax for Facebook Ireland will be circa 11%. In contrast, Meta Platforms Inc. would incur a special IP tax rate of 13.125% (the FDII rate) if its Irish business relocated to the U.S. Tax relief in the U.S. (21% vs. Irish at the GILTI rate) and accelerated capital expensing, would make this effective U.S. rate around 12%. The insignificance of the U.S./Irish tax difference was demonstrated when Facebook moved 1.5bn non-EU accounts to the U.S. to limit exposure to GDPR. Facilities Users outside of the U.S. and Canada contract with Meta's Irish subsidiary, Meta Platforms Ireland Limited (formerly Facebook Ireland Limited), allowing Meta to avoid US taxes for all users in Europe, Asia, Australia, Africa and South America. Meta is making use of the Double Irish arrangement which allows it to pay 2–3% corporation tax on all international revenue. In 2010, Facebook opened its fourth office, in Hyderabad, India, which houses online advertising and developer support teams and provides support to users and advertisers. In India, Meta is registered as Facebook India Online Services Pvt Ltd. It also has offices or planned sites in Chittagong, Bangladesh; Dublin, Ireland; and Austin, Texas, among other cities. Facebook opened its London headquarters in 2017 in Fitzrovia in central London. Facebook opened an office in Cambridge, Massachusetts in 2018. The offices were initially home to the "Connectivity Lab", a group focused on bringing Internet access to those who do not have access to the Internet. In April 2019, Facebook opened its Taiwan headquarters in Taipei. In March 2022, Meta opened new regional headquarters in Dubai. In September 2023, it was reported that Meta had paid £149m to British Land to break the lease on Triton Square London office. Meta reportedly had another 18 years left on its lease on the site. As of 2023, Facebook operated 21 data centers. It committed to purchase 100% renewable energy and to reduce its greenhouse gas emissions 75% by 2020. Its data center technologies include Fabric Aggregator, a distributed network system that accommodates larger regions and varied traffic patterns. Reception US Representative Alexandria Ocasio-Cortez responded in a tweet to Zuckerberg's announcement about Meta, saying: "Meta as in 'we are a cancer to democracy metastasizing into a global surveillance and propaganda machine for boosting authoritarian regimes and destroying civil society ... for profit!'" Ex-Facebook employee Frances Haugen and whistleblower behind the Facebook Papers responded to the rebranding efforts by expressing doubts about the company's ability to improve while led by Mark Zuckerberg, and urged the chief executive officer to resign. In November 2021, a video published by Inspired by Iceland went viral, in which a Zuckerberg look-alike promoted the Icelandverse, a place of "enhanced actual reality without silly looking headsets". In a December 2021 interview, SpaceX and Tesla chief executive officer Elon Musk said he could not see a compelling use-case for the VR-driven metaverse, adding: "I don't see someone strapping a frigging screen to their face all day." In January 2022, Louise Eccles of The Sunday Times logged into the metaverse with the intention of making a video guide. She wrote: Initially, my experience with the Oculus went well. I attended work meetings as an avatar and tried an exercise class set in the streets of Paris. The headset enabled me to feel the thrill of carving down mountains on a snowboard and the adrenaline rush of climbing a mountain without ropes. Yet switching to the social apps, where you mingle with strangers also using VR headsets, it was at times predatory and vile. Eccles described being sexually harassed by another user, as well as "accents from all over the world, American, Indian, English, Australian, using racist, sexist, homophobic and transphobic language". She also encountered users as young as 7 years old on the platform, despite Oculus headsets being intended for users over 13. See also References External links 37°29′06″N 122°08′54″W / 37.48500°N 122.14833°W / 37.48500; -122.14833 |
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