text:
Eugene Wigner

Eugene Paul Wigner (Wigner Jenő Pál, ; November 17, 1902 – January 1, 1995) was a Hungarian-American theoretical physicist who also contributed to mathematical physics. He received the Nobel Prize in Physics in 1963 "for his contributions to the theory of the atomic nucleus and the elementary particles, particularly through the discovery and application of fundamental symmetry principles".

A graduate of the Technical University of Berlin, Wigner worked as an assistant to Karl Weissenberg and Richard Becker at the Kaiser Wilhelm Institute in Berlin, and David Hilbert at the University of Göttingen. Wigner and Hermann Weyl were responsible for introducing group theory into physics, particularly the theory of symmetry in physics. Along the way he performed ground-breaking work in pure mathematics, in which he authored a number of mathematical theorems. In particular, Wigner's theorem is a cornerstone in the mathematical formulation of quantum mechanics. He is also known for his research into the structure of the atomic nucleus. In 1930, Princeton University recruited Wigner, along with John von Neumann, and he moved to the United States, where he obtained citizenship in 1937.

Wigner participated in a meeting with Leo Szilard and Albert Einstein that resulted in the Einstein–Szilard letter, which prompted President Franklin D. Roosevelt to authorize the creation of the Advisory Committee on Uranium with the purpose of investigating the feasibility of nuclear weapons. Wigner was afraid that the German nuclear weapon project would develop an atomic bomb first. During the Manhattan Project, he led a team whose task was to design nuclear reactors to convert uranium into weapons grade plutonium. At the time, reactors existed only on paper, and no reactor had yet gone critical. Wigner was disappointed that DuPont was given responsibility for the detailed design of the reactors, not just their construction. He became director of research and development at the Clinton Laboratory (now the Oak Ridge National Laboratory) in early 1946, but became frustrated with bureaucratic interference by the Atomic Energy Commission, and returned to Princeton.

In the postwar period, he served on a number of government bodies, including the National Bureau of Standards from 1947 to 1951, the mathematics panel of the National Research Council from 1951 to 1954, the physics panel of the National Science Foundation, and the influential General Advisory Committee of the Atomic Energy Commission from 1952 to 1957 and again from 1959 to 1964. In later life, he became more philosophical, and published The Unreasonable Effectiveness of Mathematics in the Natural Sciences, his best-known work outside technical mathematics and physics.

Early life and education
Wigner Jenő Pál was born in Budapest, Austria-Hungary on November 17, 1902, to middle class Jewish parents, Elisabeth Elsa Einhorn and Antal Anton Wigner, a leather tanner. He had an older sister, Berta, known as Biri, and a younger sister Margit, known as Manci, who later married British theoretical physicist Paul Dirac. He was home schooled by a professional teacher until the age of 9, when he started school at the third grade. During this period, Wigner developed an interest in mathematical problems. At the age of 11, Wigner contracted what his doctors believed to be tuberculosis. His parents sent him to live for six weeks in a sanatorium in the Austrian mountains, before the doctors concluded that the diagnosis was mistaken.

Wigner's family was Jewish, but not religiously observant, and his Bar Mitzvah was a secular one. From 1915 through 1919, he studied at the secondary grammar school called Fasori Evangélikus Gimnázium, the school his father had attended. Religious education was compulsory, and he attended classes in Judaism taught by a rabbi. A fellow student was János von Neumann, who was a year behind Wigner. They both benefited from the instruction of the noted mathematics teacher László Rátz. In 1919, to escape the Béla Kun communist regime, the Wigner family briefly fled to Austria, returning to Hungary after Kun's downfall. Partly as a reaction to the prominence of Jews in the Kun regime, the family converted to Lutheranism. Wigner explained later in his life that his family decision to convert to Lutheranism "was not at heart a religious decision but an anti-communist one".

After graduating from the secondary school in 1920, Wigner enrolled at the Budapest University of Technical Sciences, known as the Műegyetem. He was not happy with the courses on offer, and in 1921 enrolled at the Technische Hochschule Berlin (now Technical University of Berlin), where he studied chemical engineering. He also attended the Wednesday afternoon colloquia of the German Physical Society. These colloquia featured leading researchers including Max Planck, Max von Laue, Rudolf Ladenburg, Werner Heisenberg, Walther Nernst, Wolfgang Pauli, and Albert Einstein. Wigner also met the physicist Leó Szilárd, who at once became Wigner's closest friend. A third experience in Berlin was formative. Wigner worked at the Kaiser Wilhelm Institute for Physical Chemistry and Electrochemistry (now the Fritz Haber Institute), and there he met Michael Polanyi, who became, after László Rátz, Wigner's greatest teacher. Polanyi supervised Wigner's DSc thesis, Bildung und Zerfall von Molekülen ("Formation and Decay of Molecules").

Middle years
Wigner returned to Budapest, where he went to work at his father's tannery, but in 1926, he accepted an offer from Karl Weissenberg at the Kaiser Wilhelm Institute in Berlin. Weissenberg wanted someone to assist him with his work on X-ray crystallography, and Polanyi had recommended Wigner. After six months as Weissenberg's assistant, Wigner went to work for Richard Becker for two semesters. Wigner explored quantum mechanics, studying the work of Erwin Schrödinger. He also delved into the group theory of Ferdinand Frobenius and Eduard Ritter von Weber.

Wigner received a request from Arnold Sommerfeld to work at the University of Göttingen as an assistant to the great mathematician David Hilbert. This proved a disappointment, as the aged Hilbert's abilities were failing, and his interests had shifted to logic. Wigner nonetheless studied independently. He laid the foundation for the theory of symmetries in quantum mechanics and in 1927 introduced what is now known as the Wigner D-matrix. Wigner and Hermann Weyl were responsible for introducing group theory into quantum mechanics. The latter had written a standard text, Group Theory and Quantum Mechanics (1928), but it was not easy to understand, especially for younger physicists. Wigner's Group Theory and Its Application to the Quantum Mechanics of Atomic Spectra (1931) made group theory accessible to a wider audience.

In these works, Wigner laid the foundation for the theory of symmetries in quantum mechanics. Wigner's theorem, proven by him in 1931, is a cornerstone of the mathematical formulation of quantum mechanics. The theorem specifies how physical symmetries such as rotations, translations, and CPT symmetry are represented on the Hilbert space of states. According to the theorem, any symmetry transformation is represented by a linear and unitary or antilinear and antiunitary transformation of Hilbert space. The representation of a symmetry group on a Hilbert space is either an ordinary representation or a projective representation.

In the late 1930s, Wigner extended his research into atomic nuclei. By 1929, his papers were drawing notice in the world of physics. In 1930, Princeton University recruited Wigner for a one-year lectureship, at 7 times the salary that he had been drawing in Europe. Princeton recruited von Neumann at the same time. Jenő Pál Wigner and János von Neumann had collaborated on three papers together in 1928 and two in 1929. They anglicized their first names to "Eugene" and "John", respectively. When their year was up, Princeton offered a five-year contract as visiting professors for half the year. The Technische Hochschule responded with a teaching assignment for the other half of the year. This was very timely, since the Nazis soon rose to power in Germany. At Princeton in 1934, Wigner introduced his sister Margit "Manci" Wigner to the physicist Paul Dirac, with whom she remarried.

Princeton did not rehire Wigner when his contract ran out in 1936. Through Gregory Breit, Wigner found new employment at the University of Wisconsin. There, he met his first wife, Amelia Frank, who was a physics student there. However, she died unexpectedly in 1937, leaving Wigner distraught. He therefore accepted an offer in 1938 from Princeton to return there. Wigner became a naturalized citizen of the United States on January 8, 1937, and he brought his parents to the United States.

Manhattan Project
Although he was a professed political amateur, on August 2, 1939, he participated in a meeting with Leó Szilárd and Albert Einstein that resulted in the Einstein–Szilárd letter, which prompted President Franklin D. Roosevelt to authorize the creation of the Advisory Committee on Uranium with the purpose of investigating the feasibility of atomic bombs. Wigner was afraid that the German nuclear weapon project would develop an atomic bomb first, and even refused to have his fingerprints taken because they could be used to track him down if Germany won. "Thoughts of being murdered," he later recalled, "focus your mind wonderfully."

On June 4, 1941, Wigner married his second wife, Mary Annette Wheeler, a professor of physics at Vassar College, who had completed her Ph.D. at Yale University in 1932. After the war she taught physics on the faculty of Rutgers University's Douglass College in New Jersey until her retirement in 1964. They remained married until her death in November 1977. They had two children, David Wigner and Martha Wigner Upton.

During the Manhattan Project, Wigner led a team that included J. Ernest Wilkins Jr., Alvin M. Weinberg, Katharine Way, Gale Young and Edward Creutz. The group's task was to design the production nuclear reactors that would convert uranium into weapons grade plutonium. At the time, reactors existed only on paper, and no reactor had yet gone critical. In July 1942, Wigner chose a conservative 100 MW design, with a graphite neutron moderator and water cooling. Wigner was present at a converted rackets court under the stands at the University of Chicago's abandoned Stagg Field on December 2, 1942, when the world's first atomic reactor, Chicago Pile One (CP-1) achieved a controlled nuclear chain reaction. Wigner was disappointed that DuPont was given responsibility for the detailed design of the reactors, not just their construction. He threatened to resign in February 1943, but was talked out of it by the head of the Metallurgical Laboratory, Arthur Compton, who sent him on vacation instead. As it turned out, a design decision by DuPont to give the reactor additional load tubes for more uranium saved the project when neutron poisoning became a problem. Without the additional tubes, the reactor could have been run at 35% power until the boron impurities in the graphite were burned up and enough plutonium produced to run the reactor at full power; but this would have set the project back a year. During the 1950s, he would even work for DuPont on the Savannah River Site. Wigner did not regret working on the bomb, remarking: "In fact, my regret is that it was not done sooner. If we had begun trying seriously to control fission in 1939, we might have had an atomic bomb by the Winter of 1943-1944. At that time Stalin's army was still bottled up in Stalingrad. By the middle of 1945, when we first used the bomb, they had already overrun much of Central Europe. The Yalta Conference would have produced a document much less favourable to Russia, and even Communist China might have been set back. So I do not regret helping to build the bomb."

An important discovery Wigner made during the project was the Wigner effect. This is a swelling of the graphite moderator caused by the displacement of atoms by neutron radiation. The Wigner effect was a serious problem for the reactors at the Hanford Site in the immediate post-war period, and resulted in production cutbacks and a reactor being shut down entirely. It was eventually discovered that it could be overcome by controlled heating and annealing.

Through Manhattan project funding, Wigner and Leonard Eisenbud also developed an important general approach to nuclear reactions, the Wigner–Eisenbud R-matrix theory, which was published in 1947.

Later years
Wigner was elected to the American Philosophical Society in 1944 and the United States National Academy of Sciences in 1945. He accepted a position as the director of research and development at the Clinton Laboratory (now the Oak Ridge National Laboratory) in Oak Ridge, Tennessee in early 1946. Because he did not want to be involved in administrative duties, he became co-director of the laboratory, with James Lum handling the administrative chores as executive director. When the newly created Atomic Energy Commission (AEC) took charge of the laboratory's operations at the start of 1947, Wigner feared that many of the technical decisions would be made in Washington. He also saw the Army's continuation of wartime security policies at the laboratory as a "meddlesome oversight", interfering with research. One such incident occurred in March 1947, when the AEC discovered that Wigner's scientists were conducting experiments with a critical mass of uranium-235 when the director of the Manhattan Project, Major General Leslie R. Groves, Jr., had forbidden such experiments in August 1946 after the death of Louis Slotin at the Los Alamos Laboratory. Wigner argued that Groves's order had been superseded, but was forced to terminate the experiments, which were completely different from the one that killed Slotin.

Feeling unsuited to a managerial role in such an environment, he left Oak Ridge in 1947 and returned to Princeton University, although he maintained a consulting role with the facility for many years. In the postwar period, he served on a number of government bodies, including the National Bureau of Standards from 1947 to 1951, the mathematics panel of the National Research Council from 1951 to 1954, the physics panel of the National Science Foundation, and the influential General Advisory Committee of the Atomic Energy Commission from 1952 to 1957 and again from 1959 to 1964. He also contributed to civil defense.

Wigner was elected to the American Academy of Arts and Sciences in 1950.

Near the end of his life, Wigner's thoughts turned more philosophical. In 1960, he published a now classic article on the philosophy of mathematics and of physics, which has become his best-known work outside technical mathematics and physics, "The Unreasonable Effectiveness of Mathematics in the Natural Sciences". He argued that biology and cognition could be the origin of physical concepts, as we humans perceive them, and that the happy coincidence that mathematics and physics were so well matched, seemed to be "unreasonable" and hard to explain. His original paper has provoked and inspired many responses across a wide range of disciplines. These included Richard Hamming in Computer Science, Arthur Lesk in Molecular Biology, Peter Norvig in data mining, Max Tegmark in Physics, Ivor Grattan-Guinness in Mathematics, and Vela Velupillai in Economics.

Turning to philosophical questions about the theory of quantum mechanics, Wigner developed a thought experiment (later called Wigner's Friend paradox) to illustrate his belief that consciousness is foundational to the quantum mechanical measurement process. He thereby followed an ontological approach that sets human's consciousness at the center: "All that quantum mechanics purports to provide are probability connections between subsequent impressions (also called 'apperceptions') of the consciousness".

Measurements are understood as the interactions which create the impressions in our consciousness (and as a result modify the wave function of the "measured" physical system), an idea which has been called the "consciousness causes collapse" interpretation.

Interestingly, Hugh Everett III (a student of Wigner's) discussed Wigner's thought experiment in the introductory part of his 1957 dissertation as an "amusing, but extremely hypothetical drama". In an early draft of Everett's work, one also finds a drawing of the Wigner's Friend situation, which must be seen as the first evidence on paper of the thought experiment that was later assigned to be Wigner's. This suggests that Everett must at least have discussed the problem together with Wigner.

In November 1963, Wigner called for the allocation of 10% of the national defense budget to be spent on nuclear blast shelters and survival resources, arguing that such an expenditure would be less costly than disarmament. Wigner considered a recent Woods Hole study's conclusion that a nuclear strike would kill 20% of Americans to be a very modest projection and that the country could recover from such an attack more quickly than Germany had recovered from the devastation of World War II.

Wigner was awarded the Nobel Prize in Physics in 1963 "for his contributions to the theory of the atomic nucleus and the elementary particles, particularly through the discovery and application of fundamental symmetry principles". The prize was shared that year, with the other half of the award divided between Maria Goeppert-Mayer and J. Hans D. Jensen. Wigner professed that he had never considered the possibility that this might occur, and added: "I never expected to get my name in the newspapers without doing something wicked." He also won the Franklin Medal in 1950, the Enrico Fermi award in 1958, the Atoms for Peace Award in 1959, the Max Planck Medal in 1961, the National Medal of Science in 1969, the Albert Einstein Award in 1972, the Golden Plate Award of the American Academy of Achievement in 1974, the eponymous Wigner Medal in 1978, and the Herzl Prize in 1982. In 1968 he gave the Josiah Willard Gibbs lecture.

After his retirement from Princeton in 1971, Wigner prepared the first edition of Symmetries and Reflections, a collection of philosophical essays, and became more involved in international and political meetings; around this time he became a leader and vocal defender of the Unification Church's annual International Conference on the Unity of the Sciences.

Mary died in November 1977. In 1979, Wigner married his third wife, Eileen Clare-Patton (Pat) Hamilton, the widow of physicist Donald Ross Hamilton, the dean of the graduate school at Princeton University, who had died in 1972. In 1992, at the age of 90, he published his memoirs, The Recollections of Eugene P. Wigner with Andrew Szanton. In it, Wigner said: "The full meaning of life, the collective meaning of all human desires, is fundamentally a mystery beyond our grasp. As a young man, I chafed at this state of affairs. But by now I have made peace with it. I even feel a certain honor to be associated with such a mystery." In his collection of essays 'Philosophical Reflections and Syntheses' (1995), he commented: "It was not possible to formulate the laws of quantum mechanics in a fully consistent way without reference to consciousness."

Wigner was credited as a member of the advisory board for the Western Goals Foundation, a private domestic intelligence agency created in the US in 1979 to "fill the critical gap caused by the crippling of the FBI, the disabling of the House Un-American Activities Committee and the destruction of crucial government files".

Wigner died of pneumonia at the University Medical Center in Princeton, New Jersey on 1 January 1995.

Publications

 * 1958 (with Alvin M. Weinberg). Physical Theory of Neutron Chain Reactors University of Chicago Press. ISBN 0-226-88517-8
 * 1959. Group Theory and its Application to the Quantum Mechanics of Atomic Spectra. New York: Academic Press. Translation by J. J. Griffin of 1931, Gruppentheorie und ihre Anwendungen auf die Quantenmechanik der Atomspektren, Vieweg Verlag, Braunschweig.
 * 1970 Symmetries and Reflections: Scientific Essays. Indiana University Press, Bloomington ISBN 0-262-73021-9
 * 1992 (as told to Andrew Szanton). The Recollections of Eugene P. Wigner. Plenum. ISBN 0-306-44326-0
 * 1995 (with Jagdish Mehra and Arthur Wightman, eds.). Philosophical Reflections and Syntheses. Springer, Berlin ISBN 3-540-63372-3

Selected contributions

 * Theoretical physics

 * Bargmann–Wigner equations
 * Jordan–Wigner transformation
 * Newton–Wigner localization
 * Polynomial Wigner–Ville distribution
 * Relativistic Breit–Wigner distribution
 * Thomas–Wigner rotation
 * Wigner–Eckart theorem
 * Wigner–Inonu contraction
 * Wigner–Seitz cell
 * Wigner–Seitz radius
 * Wigner–Weyl transform
 * Wigner–Wilkins spectrum
 * Wigner's classification
 * Wigner quasiprobability distribution
 * Wigner's friend
 * Wigner's theorem
 * Wigner crystal
 * Wigner D-matrix
 * Wigner effect
 * Wigner energy
 * Wigner lattice
 * Wigner's disease
 * Von Neumann–Wigner interpretation
 * Wigner–Witmer correlation rules

 * Mathematics

 * Gabor–Wigner transform
 * Modified Wigner distribution function
 * Wigner distribution function
 * Wigner semicircle distribution
 * Wigner rotation
 * Wigner quasiprobability distribution
 * Wigner semicircle distribution
 * 6-j symbol
 * 9-j symbol
 * Wigner 3-j symbols
 * Wigner–İnönü group contraction
 * Wigner surmise

title: Eugene Wigner


text:
Talk:Eugene Wigner

Old talk
This is indeed a good article (it was added to brilliant prose). I always get suspicious when an anonymous person posts a good, polished article :-) --but it passes the Google test (meaning it probably wasn't online in exactly these words until now). --LMS

I'm interested in Prof. Wigner's connection to the Unification Movement of Sun Myung Moon. I know he participated in the science conference sponsored by Rev. Moons International Cultural Foundation. But what was his role?

I hate to rely on memory. Was he a conference chairman, or what?

Here's a quote I picked up on an Altavista search.

 * Eugene Wigner, a theoretical physicist, is (or was) on the board of directors of the Committee on the Present Danger. (25) He is a member of the advisory board of Accuracy in Media and was a member of the advisory board of Western Goals Foundation. (36) Accuracy in Media also received some of the $400,000 raised through Charles Wick's efforts at the White House (see Govt Connections). (53) Wigner received a $200,000 "founder's award" from the Rev. Sun Myung Moon--head of the Unification Church--at the 1982 Intl Conference on the Unity of the Sciences (ICUS). ICUS is an offshoot of the Moon-funded Intl Cultural Foundation. (49)

(source)

User:Ed Poor

This article omits important aspects of his influence on cosmology and the philosophy of mathematics, in particular his most-cited article "The Unreasonable Effectiveness of Mathematics in the Physical Sciences," 1960.

- Can someone fix the template - Laureate 97 is too far off to the right. Ludvikus 07:40, 5 September 2006 (UTC) - The infobox says his religion is "Jewish", I believe the correct term is Judaism, even though he was by ethnicity Jewish. The article also says the family converted to Lutheranism. And then there's the question whether he was a practicing Jew or simply Jewish. I propose removal or perhaps alteration to "Ethnicity: Jewish" if there are no sources for his religious affiliations. Naphra 19:27, 17 April 2007 (UTC)
 * There is a source saying he was Jewish. He was clearly born Jewish.  At best it might be said "Jewish: converted to Lutheranism"; anything else violates WP:NOR.--Runcorn 21:04, 18 April 2007 (UTC)

- in the introduction to the article it says he had SEVEN MILLION THEOREMS! is that true? if so, why isn't it sited? —Preceding unsigned comment added by Qmark42 (talk • contribs) 14:55, 22 July 2008 (UTC)

Involvement in self-sustaining fission reaction?
See Talk:Chicago Pile-1 --129.49.7.125 (talk) 16:35, 23 April 2009 (UTC)

Quotes about Wigner?
Does a quote by an unreliable source that is about Rev. Moon (not Wigner) does not have place in a section of Quotes about Wigner. --Shagie (talk) 02:21, 4 May 2009 (UTC)
 * Failing to see anyone argue the opposite over the past while, I'm going to remove the section as it looks out of place and isn't about Wigner. --Shagie (talk) 06:03, 14 May 2009 (UTC)

And the content that was removed from the article:

 * In a 1987 appreciation of Professor Wigner, Alvin M. Weinberg stated: "...this trait of Wigner's [giving credit to his young collaborators] explains why so much, not only of reactor theory but of theoretical physics from 1930 to 1965 — though it may not bear Wigner's name — actually has origin in a suggestion made or question asked by Professor Wigner."

 * "I greatly appreciate Rev. Moon's deep concern for the present predicament of mankind. He believes that intellectuals have a particular responsibility to use their knowledge and creative imagination in the urgent talk of rebuilding society with values as the supreme guide." (quoted in Peace King, page 101)

--Shagie (talk) 06:05, 14 May 2009 (UTC)

can be added
since 2005 a building of the technical university in Berlin is named after him, see http://www.an-morgen-denken.de/tui/05nov/physik.htm Plehn (talk) 05:45, 29 December 2010 (UTC)

Questions and Suggestions
1. "Wigner was present at a converted squash courts ..." This is incorrect US English usage -- is it correct in British English?
 * No. Thank you for asking. The use of the singular indefinite article a with a regular plural courts is incorrect everywhere. The given citation didn't mention squash courts, but according to this citation, there was just one court there (for rackets, not for squash). This will be fixed momentarily. ChrisJBenson (talk) 00:31, 20 August 2013 (UTC)

2. "When his duties there did not work out especially well, Wigner returned to Princeton University" This is not a very substantive comment. Either more detail should be added or a citation given for this assertion.
 * Agreed. Someone had already added a citation (albeit with a meta-syntax error). I'll paraphrase its text to revise the questionable clause, and hopefully fix the citation internal syntax ChrisJBenson (talk) 00:31, 20 August 2013 (UTC)

3. "However, by his personal beliefs, Wigner was at heart a pacifist" This is a weak statement about one of the prime movers behind the creation of the Atomic Bomb, and, again, no reference is given. The interesting thing about Wigner is that his fear of the possibility of the Nazis attaining the Bomb was much stronger than any inherent or philosophical pacifism. This, of course, was also true of Albert Einstein, Leo Szilard, Robert Oppenheimer, and others, but Wigner is a particularly good and important example of this phenomenon, which is more interesting than simple "pacifism".
 * I don't disagree with [User:Chordatum], but I don't disagree with the existing text either. I am not sure whether or how to change this. As I believe the existing text is probably verifiable, I won't change it myself. Others should feel free, though! ChrisJBenson (talk) 00:31, 20 August 2013 (UTC)

--Chordatum (talk) 17:09, 20 March 2011 (UTC)

— Preceding unsigned comment added by Chordatum (talk • contribs) 16:47, 20 March 2011 (UTC)

There is a passage in the article that suggests that Wigner introduced Leo Szilard to Albert Einstein in 1939. I know for a fact that Szilard and Einstein have at least one patent from 1930, its called the Einstein Refrigerator and there is an article on it on Wikipedia. Somebody should correct that. :) — Preceding unsigned comment added by Silentnogood (talk • contribs) 11:57, 10 November 2013 (UTC)

Hungarian?
The lead says he was Hungarian, but when I knew him at LSU he always described himself as Austrian. A hatnote in the article says his "native" name was Wigner Jeno, but of course his native language was German, so I doubt that was his native name. Rwflammang (talk) 20:17, 31 January 2012 (UTC)
 * I've sent you (User Talk: Rwflammang) a long boring message on this topic. The short version is ...:

 * Name: Wigner Jenő Pál. Citizenship: Hungarian (ages 0-35). Ethnicity: Ashkenazim. Ancestral homeland: Syria around 150 AD.
 * This response is from ChrisJBenson (talk) 11:33, 20 August 2013 (UTC)
 * I'm just going on what he said in the book! Hawkeye7 (talk) 11:59, 20 August 2013 (UTC)
 * There are interviews with Wigner on Youtube where he speaks perfect Hungarian, and speaks fondly of Hungary, eg https://www.youtube.com/watch?v=Ttxc3DcMWVM&t=404s.

performed work
I am German, and my knowledge and experience of the English language is limited. But to say that he "performed" ground-breaking work in pure mathematics, doesn't that sound like he merely acted it out? --217.226.87.134 (talk) 16:32, 19 May 2016 (UTC)
 * Furthermore: How can a cornerstone of the mathematical formulation of quantum mechanics be considered a particular case of a theorem in pure mathematics? --217.226.87.134 (talk) 16:46, 19 May 2016 (UTC)

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Number of children
In the text it is mentioned that "They had two children, David Wigner and Martha Wigner Upton" (from the second marriage). However, in two other places it is mentioned that he had three children. For example at the very end: "He was survived by his wife Eileen (died 2010) and children Erika, David and Martha, and his sisters Bertha and Margit." Did I miss something? — Preceding unsigned comment added by 78.130.86.95 (talk) 11:09, 4 February 2022 (UTC)

Lead change
"Eugene Paul "E. P." Wigner (Wigner Jenő Pál, ; November 17, 1902 – January 1, 1995) was a Hungarian-American theoretical physicist who also contributed to mathematical physics. He obtained American citizenship in 1937, and received the Nobel Prize in Physics in 1963 "for his contributions to the theory of the atomic nucleus and the elementary particles, particularly through the discovery and application of fundamental symmetry principles"."

Mentioning his American citizenship in 1937 seems repetitious - the sentence before says he is Hungarian-American. Also, his American citizenship seems far less important than his Nobel Prize, yet is mentioned first. I feel his citizenship in 1937 should be mentioned elsewhere in the lead where it chronologically makes sense. 71.11.5.2 (talk) 19:56, 20 July 2022 (UTC)

Late-life right-wing politics?
I noticed Wigner on the advisory board of the sketchy Western Goals Foundation and added a sentence in his Later Life section, but while digging for some more details, it looks like around the same time he was on the board of The Washington Times; how does such a renowned / respected / respectable, and (as far as I can tell) publicly apolitical scientist get mixed up with multiple explicitly right-wing groups that late in life?

Will try to check his 1992 recollections, but the ToC doesn't look too promising, and no mention of either group in the Index.

Any more knowledgable editors have any pointers?

Thanks, ShadyNorthAmericanIPs (talk) 04:08, 10 March 2023 (UTC)

 * Doing some more digging; he seems to have spent the early 1960s lobbying for government spending to make a nuclear war survivable (as opposed to making it unthinkable). In 1960 the NYT reported his "wariness" on an atomic test ban, where he characterized the ban's supporters as "emotional" but demurred on making his views explicit with "I am very happy I do not make to make [that decision]". In 1963 they characterize a letter from him as supportive of the test-ban treaty, but the text is rather more hawkish. His own viewpoint is pretty clear in his 1965 letter to the NYT challenging their critique of such a "civil defense" proposal, where he characterized opposition as wanting to "furnish lives of our people as 'hostages to the good behavior of the US government'".
 * So he was definitely not pacifist, but those views weren't exactly fringe in the 1960s; but as the years move on, his name starts appearing in connection to more right-wing causes further removed from his area of direct expertise -- a letter of support of US policy in Cuba, a call for "order" on campuses, an announcement for the founding of a "Committee to Unite America" ("to guard morals"), lashing out at the UN over perceived anti-Israel bias, and railing against affirmative action; but, in each case, the views are attributed to a group, not Wigner specifically (though he *is* consistently cited by name, with a mention of his Nobel Laureate status to burnish the group's credibility).
 * Still not enough to warrant its own section, but it's enough to convince me that he didn't just accidentally sign onto some crank groups' charters without reading the fine print. ShadyNorthAmericanIPs (talk) 02:00, 22 March 2023 (UTC)
 * More: in his National Academy of Sciences bio, there is this tantalizing sentence about what he spent his free time post-retirement doing:
 * He also became the leader of free-ranging philosophical discussion groups that met more or less annually under the auspices of the Unification Church.
 * Nothing else in the bio references the Moonies or really politics at all, but pointedly mentioning that these meetings were "under the auspices" of a controversial religious sect seems intentional? ShadyNorthAmericanIPs (talk) 03:59, 8 May 2023 (UTC)

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Talk:Eugene Wigner


text:
Electroweak interaction

In particle physics, the electroweak interaction or electroweak force is the unified description of two of the four known fundamental interactions of nature: electromagnetism (electromagnetic interaction) and the weak interaction. Although these two forces appear very different at everyday low energies, the theory models them as two different aspects of the same force. Above the unification energy, on the order of 246 GeV, they would merge into a single force. Thus, if the temperature is high enough – approximately 1015 K – then the electromagnetic force and weak force merge into a combined electroweak force. During the quark epoch (shortly after the Big Bang), the electroweak force split into the electromagnetic and weak force. It is thought that the required temperature of 1015 K has not been seen widely throughout the universe since before the quark epoch, and currently the highest human-made temperature in thermal equilibrium is around $5.5 K$ (from the Large Hadron Collider).

Sheldon Glashow, Abdus Salam, and Steven Weinberg were awarded the 1979 Nobel Prize in Physics for their contributions to the unification of the weak and electromagnetic interaction between elementary particles, known as the Weinberg–Salam theory. The existence of the electroweak interactions was experimentally established in two stages, the first being the discovery of neutral currents in neutrino scattering by the Gargamelle collaboration in 1973, and the second in 1983 by the UA1 and the UA2 collaborations that involved the discovery of the W and Z gauge bosons in proton–antiproton collisions at the converted Super Proton Synchrotron. In 1999, Gerardus 't Hooft and Martinus Veltman were awarded the Nobel prize for showing that the electroweak theory is renormalizable.

History
After the Wu experiment in 1956 discovered parity violation in the weak interaction, a search began for a way to relate the weak and electromagnetic interactions. Extending his doctoral advisor Julian Schwinger's work, Sheldon Glashow first experimented with introducing two different symmetries, one chiral and one achiral, and combined them such that their overall symmetry was unbroken. This did not yield a renormalizable theory, and its gauge symmetry had to be broken by hand as no spontaneous mechanism was known, but it predicted a new particle, the Z boson. This received little notice, as it matched no experimental finding.

In 1964, Salam and John Clive Ward had the same idea, but predicted a massless photon and three massive gauge bosons with a manually broken symmetry. Later around 1967, while investigating spontaneous symmetry breaking, Weinberg found a set of symmetries predicting a massless, neutral gauge boson. Initially rejecting such a particle as useless, he later realized his symmetries produced the electroweak force, and he proceeded to predict rough masses for the W and Z bosons. Significantly, he suggested this new theory was renormalizable. In 1971, Gerard 't Hooft proved that spontaneously broken gauge symmetries are renormalizable even with massive gauge bosons.

Formulation

Mathematically, electromagnetism is unified with the weak interactions as a Yang–Mills field with an SU(2) × U(1) gauge group, which describes the formal operations that can be applied to the electroweak gauge fields without changing the dynamics of the system. These fields are the weak isospin fields $θ$$W$, $g, g′$$e$, and $T$$3$, and the weak hypercharge field $Y$. This invariance is known as electroweak symmetry.

The generators of SU(2) and U(1) are given the name weak isospin (labeled $undefined$) and weak hypercharge (labeled $Q$) respectively. These then give rise to the gauge bosons that mediate the electroweak interactions – the three $W$ bosons of weak isospin ($W$$W$, $W$$1$, and $W$$W$), and the $B$ boson of weak hypercharge, respectively, all of which are "initially" massless. These are not physical fields yet, before spontaneous symmetry breaking and the associated Higgs mechanism.

In the Standard Model, the observed physical particles, the and  bosons, and the photon, are produced through the spontaneous symmetry breaking of the electroweak symmetry SU(2) × U(1)$2$ to U(1)$W$, effected by the Higgs mechanism (see also Higgs boson), an elaborate quantum-field-theoretic phenomenon that "spontaneously" alters the realization of the symmetry and rearranges degrees of freedom.

The electric charge arises as the particular linear combination (nontrivial) of $3$$B$ (weak hypercharge) and the $T$$Y$ component of weak isospin ($$Q = T_3 + \tfrac{1}{2}\,Y_\mathrm{W}$$) that does not couple to the Higgs boson. That is to say: the Higgs and the electromagnetic field have no effect on each other, at the level of the fundamental forces ("tree level"), while any other combination of the hypercharge and the weak isospin must interact with the Higgs. This causes an apparent separation between the weak force, which interacts with the Higgs, and electromagnetism, which does not. Mathematically, the electric charge is a specific combination of the hypercharge and $1$$2$ outlined in the figure.

$U(1)$$3$ (the symmetry group of electromagnetism only) is defined to be the group generated by this special linear combination, and the symmetry described by the $U(1)$$undefined$ group is unbroken, since it does not directly interact with the Higgs.

The above spontaneous symmetry breaking makes the $em$$undefined$ and $em$ bosons coalesce into two different physical bosons with different masses – the boson, and the photon ($U(1)$),
 * $$ \begin{pmatrix}

\gamma \\ Z^0 \end{pmatrix} = \begin{pmatrix} \cos \theta_\text{W} & \sin \theta_\text{W} \\ -\sin \theta_\text{W} & \cos \theta_\text{W} \end{pmatrix} \begin{pmatrix} B \\ W_3 \end{pmatrix} ,$$ where $Y$$undefined$ is the weak mixing angle. The axes representing the particles have essentially just been rotated, in the ($T$$3$, $T$) plane, by the angle $3$$em$. This also introduces a mismatch between the mass of the and the mass of the  particles (denoted as $em$$W$ and $3$$B$, respectively),
 * $$m_\text{Z} = \frac{m_\text{W}}{\,\cos\theta_\text{W}\,} ~.$$

The $θ$$undefined$ and $W$$3$ bosons, in turn, combine to produce the charged massive bosons :
 * $$W^{\pm} = \frac{1}{\sqrt{2\,}}\,\bigl(\,W_1 \mp i W_2\,\bigr) ~.$$

Before electroweak symmetry breaking
The Lagrangian for the electroweak interactions is divided into four parts before electroweak symmetry breaking becomes manifest,
 * $$\mathcal{L}_{\mathrm{EW}} = \mathcal{L}_g + \mathcal{L}_f + \mathcal{L}_h + \mathcal{L}_y~.$$

The $$\mathcal{L}_g$$ term describes the interaction between the three $B$ vector bosons and the $θ$ vector boson,
 * $$\mathcal{L}_g = -\tfrac{1}{4} W_{a}^{\mu\nu}W_{\mu\nu}^a - \tfrac{1}{4} B^{\mu\nu}B_{\mu\nu},$$

where $$W_{a}^{\mu\nu}$$ ($$a=1,2,3$$) and $$B^{\mu\nu}$$ are the field strength tensors for the weak isospin and weak hypercharge gauge fields.

$$\mathcal{L}_f$$ is the kinetic term for the Standard Model fermions. The interaction of the gauge bosons and the fermions are through the gauge covariant derivative,
 * $$\mathcal{L}_f = \overline{Q}_j iD\!\!\!\!/\; Q_j+ \overline{u}_j iD\!\!\!\!/\; u_j+ \overline{d}_j iD\!\!\!\!/\; d_j + \overline{L}_j iD\!\!\!\!/\; L_j + \overline{e}_j iD\!\!\!\!/\; e_j,$$

where the subscript $undefined$ sums over the three generations of fermions; $m$, $undefined$, and $m$ are the left-handed doublet, right-handed singlet up, and right handed singlet down quark fields; and $undefined$ and $W$ are the left-handed doublet and right-handed singlet electron fields. The Feynman slash $$D\!\!\!\!/$$ means the contraction of the 4-gradient with the Dirac matrices, defined as
 * $$D\!\!\!\!/ \equiv \gamma^\mu\ D_\mu,$$

and the covariant derivative (excluding the gluon gauge field for the strong interaction) is defined as
 * $$\ D_\mu \equiv \partial_\mu - i\ \frac{g'}{2}\ Y\ B_\mu - i\ \frac{g}{2}\ T_j\ W_\mu^j.$$

Here $$\ Y\ $$ is the weak hypercharge and the $$\ T_j\ $$ are the components of the weak isospin.

The $$\mathcal{L}_h$$ term describes the Higgs field $$h$$ and its interactions with itself and the gauge bosons,
 * $$\mathcal{L}_h = |D_\mu h|^2 - \lambda \left(|h|^2 - \frac{v^2}{2}\right)^2\ ,$$

where $$v$$ is the vacuum expectation value.

The $$\ \mathcal{L}_y\ $$ term describes the Yukawa interaction with the fermions,
 * $$\mathcal{L}_y = - y_{u\ ij}\epsilon^{ab}\ h_b^\dagger\ \overline{Q}_{ia} u_j^c - y_{d\ ij}\ h\ \overline{Q}_i d^c_j - y_{e\,ij}\ h\ \overline{L}_i e^c_j + \mathrm{h.c.} ~,$$

and generates their masses, manifest when the Higgs field acquires a nonzero vacuum expectation value, discussed next. The $$\ y_k^{ij}\ ,$$ for $$\ k \in \{ \mathrm{u, d, e} \}\ ,$$ are matrices of Yukawa couplings.

After electroweak symmetry breaking
The Lagrangian reorganizes itself as the Higgs field acquires a non-vanishing vacuum expectation value dictated by the potential of the previous section. As a result of this rewriting, the symmetry breaking becomes manifest. In the history of the universe, this is believed to have happened shortly after the hot big bang, when the universe was at a temperature $1$ (assuming the Standard Model of particle physics).

Due to its complexity, this Lagrangian is best described by breaking it up into several parts as follows.
 * $$\mathcal{L}_{\mathrm{EW}} = \mathcal{L}_\mathrm{K} + \mathcal{L}_\mathrm{N} + \mathcal{L}_\mathrm{C} + \mathcal{L}_\mathrm{H} + \mathcal{L}_{\mathrm{HV}} + \mathcal{L}_{\mathrm{WWV}} + \mathcal{L}_{\mathrm{WWVV}} + \mathcal{L}_\mathrm{Y} ~.$$

The kinetic term $$\mathcal{L}_K$$ contains all the quadratic terms of the Lagrangian, which include the dynamic terms (the partial derivatives) and the mass terms (conspicuously absent from the Lagrangian before symmetry breaking)

\begin{align} \mathcal{L}_\mathrm{K} = \sum_f \overline{f}(i\partial\!\!\!/\!\;-m_f)\ f - \frac{1}{4}\ A_{\mu\nu}\ A^{\mu\nu} - \frac{1}{2}\ W^+_{\mu\nu}\ W^{-\mu\nu} + m_W^2\ W^+_\mu\ W^{-\mu} \\ \qquad -\frac{1}{4}\ Z_{\mu\nu}Z^{\mu\nu} + \frac{1}{2}\ m_Z^2\ Z_\mu\ Z^\mu + \frac{1}{2}\ (\partial^\mu\ H)(\partial_\mu\ H) - \frac{1}{2}\ m_H^2\ H^2 ~, \end{align} $$ where the sum runs over all the fermions of the theory (quarks and leptons), and the fields $$\ A_{\mu\nu}\ ,$$ $$\ Z_{\mu\nu}\ ,$$ $$\ W^-_{\mu\nu}\ ,$$ and $$\ W^+_{\mu\nu} \equiv (W^-_{\mu\nu})^\dagger\ $$ are given as
 * $$X^{a}_{\mu\nu} = \partial_\mu X^{a}_\nu - \partial_\nu X^{a}_\mu + g f^{abc}X^{b}_{\mu}X^{c}_{\nu} ~,$$

with $$X$$ to be replaced by the relevant field ($$A,$$ $$Z,$$ $$W^\pm$$) and $W$ by the structure constants of the appropriate gauge group.

The neutral current $$\ \mathcal{L}_\mathrm{N}\ $$ and charged current $$\ \mathcal{L}_\mathrm{C}\ $$ components of the Lagrangian contain the interactions between the fermions and gauge bosons,
 * $$\mathcal{L}_\mathrm{N} = e\ J_\mu^\mathrm{em}\ A^\mu + \frac{g}{\ \cos\theta_W\ }\ (\ J_\mu^3 - \sin^2\theta_W\ J_\mu^\mathrm{em}\ )\ Z^\mu ~,$$

where $$~e = g\ \sin \theta_\mathrm{W} = g'\ \cos \theta_\mathrm{W} ~.$$ The electromagnetic current $$\; J_\mu^{\mathrm{em}} \;$$ is
 * $$J_\mu^\mathrm{em} = \sum_f \ q_f\ \overline{f}\ \gamma_\mu\ f ~,$$

where $$\ q_f\ $$ is the fermions' electric charges. The neutral weak current $$\ J_\mu^3\ $$ is
 * $$J_\mu^3 = \sum_f\ T^3_f\ \overline{f}\ \gamma_\mu\ \frac{\ 1-\gamma^5\ }{2}\ f ~,$$

where $$T^3_f$$ is the fermions' weak isospin.

The charged current part of the Lagrangian is given by
 * $$\mathcal{L}_\mathrm{C} = -\frac{g}{\ \sqrt{2 \;}\ }\ \left[\ \overline{u}_i\ \gamma^\mu\ \frac{\ 1 - \gamma^5\ }{2} \; M^{\mathrm{CKM}}_{ij}\ d_j + \overline{\nu}_i\ \gamma^\mu\;\frac{\ 1-\gamma^5\ }{2} \; e_i\ \right]\ W_\mu^{+} + \mathrm{h.c.} ~,$$

where $$\ \nu\ $$ is the right-handed singlet neutrino field, and the CKM matrix $$M_{ij}^\mathrm{CKM}$$ determines the mixing between mass and weak eigenstates of the quarks.

$$\mathcal{L}_\mathrm{H}$$ contains the Higgs three-point and four-point self interaction terms,
 * $$\mathcal{L}_\mathrm{H} = -\frac{\ g\ m_\mathrm{H}^2\,}{\ 4\ m_\mathrm{W}\ }\;H^3 - \frac{\ g^2\ m_\mathrm{H}^2\ }{32\ m_\mathrm{W}^2}\;H^4 ~.$$

$$\mathcal{L}_{\mathrm{HV}}$$ contains the Higgs interactions with gauge vector bosons,
 * $$\mathcal{L}_\mathrm{HV} =\left(\ g\ m_\mathrm{HV} + \frac{\ g^2\ }{4}\;H^2\ \right)\left(\ W^{+}_\mu\ W^{-\mu} + \frac{1}{\ 2\ \cos^2\ \theta_\mathrm{W}\ }\;Z_\mu\ Z^\mu\ \right) ~.$$

$$\mathcal{L}_{\mathrm{WWV}}$$ contains the gauge three-point self interactions,
 * $$\mathcal{L}_{\mathrm{WWV}} = -i\ g\ \left[\; \left(\ W_{\mu\nu}^{+}\ W^{-\mu} - W^{+\mu}\ W^{-}_{\mu\nu}\ \right)\left(\ A^\nu\ \sin \theta_\mathrm{W} - Z^\nu\ \cos\theta_\mathrm{W}\ \right) + W^{-}_\nu\ W^{+}_\mu\ \left(\ A^{\mu\nu}\ \sin \theta_\mathrm{W} - Z^{\mu\nu}\ \cos \theta_\mathrm{W}\ \right) \;\right] ~.$$

$$\mathcal{L}_{\mathrm{WWVV}}$$ contains the gauge four-point self interactions,

\begin{align} \mathcal{L}_{\mathrm{WWVV}} = -\frac{\ g^2\ }{4}\ \Biggl\{\ &\Bigl[\ 2\ W^{+}_\mu\ W^{-\mu} + (\ A_\mu\ \sin \theta_\mathrm{W} - Z_\mu\ \cos \theta_\mathrm{W} \ )^2\ \Bigr]^2 \\ &- \Bigl[\ W_\mu^{+}\ W_\nu^{-} + W^{+}_\nu\ W^{-}_\mu + \left(\ A_\mu\ \sin \theta_\mathrm{W} - Z_\mu\ \cos \theta_\mathrm{W}\ \right)\left(\ A_\nu\ \sin \theta_\mathrm{W} - Z_\nu\ \cos \theta_\mathrm{W}\ \right)\ \Bigr]^2\,\Biggr\} ~. \end{align} $$

$$\ \mathcal{L}_\mathrm{Y}\ $$ contains the Yukawa interactions between the fermions and the Higgs field,
 * $$\mathcal{L}_\mathrm{Y} = -\sum_f\ \frac{\ g\ m_f\ }{2\ m_\mathrm{W}} \; \overline{f}\ f\ H ~.$$

General readers

 * Conveys much of the Standard Model with no formal mathematics. Very thorough on the weak interaction.

title: Electroweak interaction


text:
Elara

Elara may refer to:

 * Elara (mythology), mother of the giant Tityos in Greek mythology
 * Elara (moon), a moon of Jupiter named after Elara
 * Elara (timeshare), a building on the Las Vegas Strip in Las Vegas, Nevada, U.S
 * Ellalan, or Eḷāra, a member of the Tamil Chola dynasty and monarch of the Anuradhapura Kingdom
 * "Elara", a song from the 2012 album Soundtrack for the Voices in My Head Vol. 02 by Celldweller
 * Elara Pictures, an American film production company
 * Chery A5, a Chinese compact sedan, sold in Ukraine as the Chery Elara

title: Elara


text:
Erasmus Reinhold

Erasmus Reinhold (22 October 1511 – 19 February 1553) was a German astronomer and mathematician, considered to be the most influential astronomical pedagogue of his generation. He was born and died in Saalfeld, Saxony.

He was educated, under Jacob Milich, at the University of Wittenberg, where he was first elected dean and later became rector. In 1536 he was appointed professor of higher mathematics by Philipp Melanchthon. In contrast to the limited modern definition, "mathematics" at the time also included applied mathematics, especially astronomy. His colleague, Georg Joachim Rheticus, also studied at Wittenberg and was appointed professor of lower mathematics in 1536.

Reinhold catalogued a large number of stars. His publications on astronomy include a commentary (1542, 1553) on Georg Purbach's Theoricae novae planetarum. Reinhold knew about Copernicus and his heliocentric ideas prior to the publication of his De revolutionibus, and made a favourable reference to him in his commentary on Purbach. However, Reinhold (like other astronomers before Kepler and Galileo) translated Copernicus' mathematical methods back into a geocentric system, rejecting heliocentric cosmology on physical and theological grounds.

Duke Albert of Brandenburg Prussia supported Reinhold and financed the printing of Reinhold's Prutenicae Tabulae (1551, 1562, 1571, and 1585) or Prussian Tables. These astronomical tables helped to disseminate calculation methods of Copernicus throughout the Empire, however, Gingerich notes that they showed a "notable lack of commitment" to heliocentricity and were "carefully framed" to be independent of the movement of the Earth. Both Reinhold's Prutenic Tables and Copernicus' studies were the foundation for the Calendar Reform by Pope Gregory XIII in 1582.

It was Reinhold's heavily annotated copy of De revolutionibus in the Royal Observatory, Edinburgh, that started Owen Gingerich on his search for copies of the first and second editions which he describes in The Book Nobody Read. In Reinhold's unpublished commentary on De revolutionibus, he calculated the distance from the Earth to the Sun. He "massaged" his calculation method in order to arrive at an answer close to that of Ptolemy.

His name has been given to a prominent lunar impact crater that lies to the south-southwest of the crater Copernicus, on the Mare Insularum.

title: Erasmus Reinhold


text:
Earthquake

An earthquake – also called a quake, tremor, or temblor – is the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they cannot be felt, to those violent enough to propel objects and people into the air, damage critical infrastructure, and wreak destruction across entire cities. The seismic activity of an area is the frequency, type, and size of earthquakes experienced over a particular time. The seismicity at a particular location in the Earth is the average rate of seismic energy release per unit volume.

In its most general sense, the word earthquake is used to describe any seismic event that generates seismic waves. Earthquakes can occur naturally or be induced by human activities, such as mining, fracking, and nuclear tests. The initial point of rupture is called the hypocenter or focus, while the ground level directly above it is the epicenter. Earthquakes are primarily caused by geological faults, but also by volcanic activity, landslides, and other seismic events. The frequency, type, and size of earthquakes in an area define its seismic activity, reflecting the average rate of seismic energy release.

Significant historical earthquakes include the 1556 Shaanxi earthquake in China, with over 830,000 fatalities, and the 1960 Valdivia earthquake in Chile, the largest ever recorded at 9.5 magnitude. Earthquakes result in various effects, such as ground shaking and soil liquefaction, leading to significant damage and loss of life. When the epicenter of a large earthquake is located offshore, the seabed may be displaced sufficiently to cause a tsunami. Earthquakes can trigger landslides. Earthquakes' occurrence is influenced by tectonic movements along faults, including normal, reverse (thrust), and strike-slip faults, with energy release and rupture dynamics governed by the elastic-rebound theory.

Efforts to manage earthquake risks involve prediction, forecasting, and preparedness, including seismic retrofitting and earthquake engineering to design structures that withstand shaking. The cultural impact of earthquakes spans myths, religious beliefs, and modern media, reflecting their profound influence on human societies. Similar seismic phenomena, known as marsquakes and moonquakes, have been observed on other celestial bodies, indicating the universality of such events beyond Earth.

Terminology
An earthquake is the shaking of the surface of Earth resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes may also be referred to as quakes, tremors, or temblors. The word tremor is also used for non-earthquake seismic rumbling.

In its most general sense, an earthquake is any seismic event—whether natural or caused by humans—that generates seismic waves. Earthquakes are caused mostly by the rupture of geological faults but also by other events such as volcanic activity, landslides, mine blasts, fracking and nuclear tests. An earthquake's point of initial rupture is called its hypocenter or focus. The epicenter is the point at ground level directly above the hypocenter.

The seismic activity of an area is the frequency, type, and size of earthquakes experienced over a particular time. The seismicity at a particular location in the Earth is the average rate of seismic energy release per unit volume.

Major examples

One of the most devastating earthquakes in recorded history was the 1556 Shaanxi earthquake, which occurred on 23 January 1556 in Shaanxi, China. More than 830,000 people died. Most houses in the area were yaodongs—dwellings carved out of loess hillsides—and many victims were killed when these structures collapsed. The 1976 Tangshan earthquake, which killed between 240,000 and 655,000 people, was the deadliest of the 20th century.

The 1960 Chilean earthquake is the largest earthquake that has been measured on a seismograph, reaching 9.5 magnitude on 22 May 1960. Its epicenter was near Cañete, Chile. The energy released was approximately twice that of the next most powerful earthquake, the Good Friday earthquake (27 March 1964), which was centered in Prince William Sound, Alaska. The ten largest recorded earthquakes have all been megathrust earthquakes; however, of these ten, only the 2004 Indian Ocean earthquake is simultaneously one of the deadliest earthquakes in history.

Earthquakes that caused the greatest loss of life, while powerful, were deadly because of their proximity to either heavily populated areas or the ocean, where earthquakes often create tsunamis that can devastate communities thousands of kilometers away. Regions most at risk for great loss of life include those where earthquakes are relatively rare but powerful, and poor regions with lax, unenforced, or nonexistent seismic building codes.

Occurrence
[[File:Fault types.svg|thumb|Three types of faults:

A. Strike-slip

B. Normal

C. Reverse ]]

Tectonic earthquakes occur anywhere on the earth where there is sufficient stored elastic strain energy to drive fracture propagation along a fault plane. The sides of a fault move past each other smoothly and aseismically only if there are no irregularities or asperities along the fault surface that increases the frictional resistance. Most fault surfaces do have such asperities, which leads to a form of stick-slip behavior. Once the fault has locked, continued relative motion between the plates leads to increasing stress and, therefore, stored strain energy in the volume around the fault surface. This continues until the stress has risen sufficiently to break through the asperity, suddenly allowing sliding over the locked portion of the fault, releasing the stored energy. This energy is released as a combination of radiated elastic strain seismic waves, frictional heating of the fault surface, and cracking of the rock, thus causing an earthquake. This process of gradual build-up of strain and stress punctuated by occasional sudden earthquake failure is referred to as the elastic-rebound theory. It is estimated that only 10 percent or less of an earthquake's total energy is radiated as seismic energy. Most of the earthquake's energy is used to power the earthquake fracture growth or is converted into heat generated by friction. Therefore, earthquakes lower the Earth's available elastic potential energy and raise its temperature, though these changes are negligible compared to the conductive and convective flow of heat out from the Earth's deep interior.

Fault types
There are three main types of fault, all of which may cause an interplate earthquake: normal, reverse (thrust), and strike-slip. Normal and reverse faulting are examples of dip-slip, where the displacement along the fault is in the direction of dip and where movement on them involves a vertical component. Many earthquakes are caused by movement on faults that have components of both dip-slip and strike-slip; this is known as oblique slip. The topmost, brittle part of the Earth's crust, and the cool slabs of the tectonic plates that are descending into the hot mantle, are the only parts of our planet that can store elastic energy and release it in fault ruptures. Rocks hotter than about 300 C flow in response to stress; they do not rupture in earthquakes. The maximum observed lengths of ruptures and mapped faults (which may break in a single rupture) are approximately 1000 km. Examples are the earthquakes in Alaska (1957), Chile (1960), and Sumatra (2004), all in subduction zones. The longest earthquake ruptures on strike-slip faults, like the San Andreas Fault (1857, 1906), the North Anatolian Fault in Turkey (1939), and the Denali Fault in Alaska (2002), are about half to one third as long as the lengths along subducting plate margins, and those along normal faults are even shorter.

Normal faults
Normal faults occur mainly in areas where the crust is being extended such as a divergent boundary. Earthquakes associated with normal faults are generally less than magnitude 7. Maximum magnitudes along many normal faults are even more limited because many of them are located along spreading centers, as in Iceland, where the thickness of the brittle layer is only about 6 km.

Reverse faults
Reverse faults occur in areas where the crust is being shortened such as at a convergent boundary. Reverse faults, particularly those along convergent boundaries, are associated with the most powerful earthquakes (called megathrust earthquakes) including almost all of those of magnitude 8 or more. Megathrust earthquakes are responsible for about 90% of the total seismic moment released worldwide.

Strike-slip faults
Strike-slip faults are steep structures where the two sides of the fault slip horizontally past each other; transform boundaries are a particular type of strike-slip fault. Strike-slip faults, particularly continental transforms, can produce major earthquakes up to about magnitude 8. Strike-slip faults tend to be oriented near vertically, resulting in an approximate width of 10 km within the brittle crust. Thus, earthquakes with magnitudes much larger than 8 are not possible.

In addition, there exists a hierarchy of stress levels in the three fault types. Thrust faults are generated by the highest, strike-slip by intermediate, and normal faults by the lowest stress levels. This can easily be understood by considering the direction of the greatest principal stress, the direction of the force that "pushes" the rock mass during the faulting. In the case of normal faults, the rock mass is pushed down in a vertical direction, thus the pushing force (greatest principal stress) equals the weight of the rock mass itself. In the case of thrusting, the rock mass "escapes" in the direction of the least principal stress, namely upward, lifting the rock mass, and thus, the overburden equals the least principal stress. Strike-slip faulting is intermediate between the other two types described above. This difference in stress regime in the three faulting environments can contribute to differences in stress drop during faulting, which contributes to differences in the radiated energy, regardless of fault dimensions.

Energy released
For every unit increase in magnitude, there is a roughly thirty-fold increase in the energy released. For instance, an earthquake of magnitude 6.0 releases approximately 32 times more energy than a 5.0 magnitude earthquake and a 7.0 magnitude earthquake releases 1,000 times more energy than a 5.0 magnitude earthquake. An 8.6-magnitude earthquake releases the same amount of energy as 10,000 atomic bombs of the size used in World War II.

This is so because the energy released in an earthquake, and thus its magnitude, is proportional to the area of the fault that ruptures and the stress drop. Therefore, the longer the length and the wider the width of the faulted area, the larger the resulting magnitude. The most important parameter controlling the maximum earthquake magnitude on a fault, however, is not the maximum available length, but the available width because the latter varies by a factor of 20. Along converging plate margins, the dip angle of the rupture plane is very shallow, typically about 10 degrees. Thus, the width of the plane within the top brittle crust of the Earth can reach 50–100 km (such as in Japan, 2011, or in Alaska, 1964), making the most powerful earthquakes possible.

Focus

The majority of tectonic earthquakes originate in the Ring of Fire at depths not exceeding tens of kilometers. Earthquakes occurring at a depth of less than 70 km are classified as "shallow-focus" earthquakes, while those with a focal depth between 70 and 300 km are commonly termed "mid-focus" or "intermediate-depth" earthquakes. In subduction zones, where older and colder oceanic crust descends beneath another tectonic plate, deep-focus earthquakes may occur at much greater depths (ranging from 300 to 700 km). These seismically active areas of subduction are known as Wadati–Benioff zones. Deep-focus earthquakes occur at a depth where the subducted lithosphere should no longer be brittle, due to the high temperature and pressure. A possible mechanism for the generation of deep-focus earthquakes is faulting caused by olivine undergoing a phase transition into a spinel structure.

Volcanic activity
Earthquakes often occur in volcanic regions and are caused there, both by tectonic faults and the movement of magma in volcanoes. Such earthquakes can serve as an early warning of volcanic eruptions, as during the 1980 eruption of Mount St. Helens. Earthquake swarms can serve as markers for the location of the flowing magma throughout the volcanoes. These swarms can be recorded by seismometers and tiltmeters (a device that measures ground slope) and used as sensors to predict imminent or upcoming eruptions.

Rupture dynamics
A tectonic earthquake begins as an area of initial slip on the fault surface that forms the focus. Once the rupture has been initiated, it begins to propagate away from the focus, spreading out along the fault surface. Lateral propagation will continue until either the rupture reaches a barrier, such as the end of a fault segment, or a region on the fault where there is insufficient stress to allow continued rupture. For larger earthquakes, the depth extent of rupture will be constrained downwards by the brittle-ductile transition zone and upwards by the ground surface. The mechanics of this process are poorly understood because it is difficult either to recreate such rapid movements in a laboratory or to record seismic waves close to a nucleation zone due to strong ground motion.

In most cases, the rupture speed approaches, but does not exceed, the shear wave (S-wave) velocity of the surrounding rock. There are a few exceptions to this:

Supershear earthquakes
Supershear earthquake ruptures are known to have propagated at speeds greater than the S-wave velocity. These have so far all been observed during large strike-slip events. The unusually wide zone of damage caused by the 2001 Kunlun earthquake has been attributed to the effects of the sonic boom developed in such earthquakes.

Slow earthquakes
Slow earthquake ruptures travel at unusually low velocities. A particularly dangerous form of slow earthquake is the tsunami earthquake, observed where the relatively low felt intensities, caused by the slow propagation speed of some great earthquakes, fail to alert the population of the neighboring coast, as in the 1896 Sanriku earthquake.

Co-seismic overpressuring and effect of pore pressure
During an earthquake, high temperatures can develop at the fault plane, increasing pore pressure and consequently vaporization of the groundwater already contained within the rock. In the coseismic phase, such an increase can significantly affect slip evolution and speed, in the post-seismic phase it can control the Aftershock sequence because, after the main event, pore pressure increase slowly propagates into the surrounding fracture network. From the point of view of the Mohr-Coulomb strength theory, an increase in fluid pressure reduces the normal stress acting on the fault plane that holds it in place, and fluids can exert a lubricating effect. As thermal overpressurization may provide positive feedback between slip and strength fall at the fault plane, a common opinion is that it may enhance the faulting process instability. After the mainshock, the pressure gradient between the fault plane and the neighboring rock causes a fluid flow that increases pore pressure in the surrounding fracture networks; such an increase may trigger new faulting processes by reactivating adjacent faults, giving rise to aftershocks. Analogously, artificial pore pressure increase, by fluid injection in Earth's crust, may induce seismicity.

Tidal forces
Tides may trigger some seismicity.

Clusters
Most earthquakes form part of a sequence, related to each other in terms of location and time. Most earthquake clusters consist of small tremors that cause little to no damage, but there is a theory that earthquakes can recur in a regular pattern. Earthquake clustering has been observed, for example, in Parkfield, California where a long-term research study is being conducted around the Parkfield earthquake cluster.

Aftershocks
An aftershock is an earthquake that occurs after a previous earthquake, the mainshock. Rapid changes of stress between rocks, and the stress from the original earthquake are the main causes of these aftershocks, along with the crust around the ruptured fault plane as it adjusts to the effects of the mainshock. An aftershock is in the same region as the main shock but always of a smaller magnitude, however, they can still be powerful enough to cause even more damage to buildings that were already previously damaged from the mainshock. If an aftershock is larger than the mainshock, the aftershock is redesignated as the mainshock and the original main shock is redesignated as a foreshock. Aftershocks are formed as the crust around the displaced fault plane adjusts to the effects of the mainshock.

Swarms
Earthquake swarms are sequences of earthquakes striking in a specific area within a short period. They are different from earthquakes followed by a series of aftershocks by the fact that no single earthquake in the sequence is the main shock, so none has a notably higher magnitude than another. An example of an earthquake swarm is the 2004 activity at Yellowstone National Park. In August 2012, a swarm of earthquakes shook Southern California's Imperial Valley, showing the most recorded activity in the area since the 1970s.

Sometimes a series of earthquakes occur in what has been called an earthquake storm, where the earthquakes strike a fault in clusters, each triggered by the shaking or stress redistribution of the previous earthquakes. Similar to aftershocks but on adjacent segments of fault, these storms occur over the course of years, with some of the later earthquakes as damaging as the early ones. Such a pattern was observed in the sequence of about a dozen earthquakes that struck the North Anatolian Fault in Turkey in the 20th century and has been inferred for older anomalous clusters of large earthquakes in the Middle East.

Frequency

It is estimated that around 500,000 earthquakes occur each year, detectable with current instrumentation. About 100,000 of these can be felt. Minor earthquakes occur very frequently around the world in places like California and Alaska in the U.S., as well as in El Salvador, Mexico, Guatemala, Chile, Peru, Indonesia, the Philippines, Iran, Pakistan, the Azores in Portugal, Turkey, New Zealand, Greece, Italy, India, Nepal, and Japan. Larger earthquakes occur less frequently, the relationship being exponential; for example, roughly ten times as many earthquakes larger than magnitude 4 occur than earthquakes larger than magnitude 5. In the (low seismicity) United Kingdom, for example, it has been calculated that the average recurrences are: an earthquake of 3.7–4.6 every year, an earthquake of 4.7–5.5 every 10 years, and an earthquake of 5.6 or larger every 100 years. This is an example of the Gutenberg–Richter law.

The number of seismic stations has increased from about 350 in 1931 to many thousands today. As a result, many more earthquakes are reported than in the past, but this is because of the vast improvement in instrumentation, rather than an increase in the number of earthquakes. The United States Geological Survey (USGS) estimates that, since 1900, there have been an average of 18 major earthquakes (magnitude 7.0–7.9) and one great earthquake (magnitude 8.0 or greater) per year, and that this average has been relatively stable. In recent years, the number of major earthquakes per year has decreased, though this is probably a statistical fluctuation rather than a systematic trend. More detailed statistics on the size and frequency of earthquakes is available from the United States Geological Survey. A recent increase in the number of major earthquakes has been noted, which could be explained by a cyclical pattern of periods of intense tectonic activity, interspersed with longer periods of low intensity. However, accurate recordings of earthquakes only began in the early 1900s, so it is too early to categorically state that this is the case.

Most of the world's earthquakes (90%, and 81% of the largest) take place in the 40000 km, horseshoe-shaped zone called the circum-Pacific seismic belt, known as the Pacific Ring of Fire, which for the most part bounds the Pacific Plate. Massive earthquakes tend to occur along other plate boundaries too, such as along the Himalayan Mountains.

With the rapid growth of mega-cities such as Mexico City, Tokyo, and Tehran in areas of high seismic risk, some seismologists are warning that a single earthquake may claim the lives of up to three million people.

Induced seismicity
While most earthquakes are caused by the movement of the Earth's tectonic plates, human activity can also produce earthquakes. Activities both above ground and below may change the stresses and strains on the crust, including building reservoirs, extracting resources such as coal or oil, and injecting fluids underground for waste disposal or fracking. Most of these earthquakes have small magnitudes. The 5.7 magnitude 2011 Oklahoma earthquake is thought to have been caused by disposing wastewater from oil production into injection wells, and studies point to the state's oil industry as the cause of other earthquakes in the past century. A Columbia University paper suggested that the 8.0 magnitude 2008 Sichuan earthquake was induced by loading from the Zipingpu Dam, though the link has not been conclusively proved.

Measurement and location
The instrumental scales used to describe the size of an earthquake began with the Richter magnitude scale in the 1930s. It is a relatively simple measurement of an event's amplitude, and its use has become minimal in the 21st century. Seismic waves travel through the Earth's interior and can be recorded by seismometers at great distances. The surface wave magnitude was developed in the 1950s as a means to measure remote earthquakes and to improve the accuracy for larger events. The moment magnitude scale not only measures the amplitude of the shock but also takes into account the seismic moment (total rupture area, average slip of the fault, and rigidity of the rock). The Japan Meteorological Agency seismic intensity scale, the Medvedev–Sponheuer–Karnik scale, and the Mercalli intensity scale are based on the observed effects and are related to the intensity of shaking.

Intensity and magnitude
The shaking of the earth is a common phenomenon that has been experienced by humans from the earliest of times. Before the development of strong-motion accelerometers, the intensity of a seismic event was estimated based on the observed effects. Magnitude and intensity are not directly related and calculated using different methods. The magnitude of an earthquake is a single value that describes the size of the earthquake at its source. Intensity is the measure of shaking at different locations around the earthquake. Intensity values vary from place to place, depending on the distance from the earthquake and the underlying rock or soil makeup.

The first scale for measuring earthquake magnitudes was developed by Charles Francis Richter in 1935. Subsequent scales (seismic magnitude scales) have retained a key feature, where each unit represents a ten-fold difference in the amplitude of the ground shaking and a 32-fold difference in energy. Subsequent scales are also adjusted to have approximately the same numeric value within the limits of the scale.

Although the mass media commonly reports earthquake magnitudes as "Richter magnitude" or "Richter scale", standard practice by most seismological authorities is to express an earthquake's strength on the moment magnitude scale, which is based on the actual energy released by an earthquake, the static seismic moment.

Seismic waves
Every earthquake produces different types of seismic waves, which travel through rock with different velocities:
 * Longitudinal P-waves (shock- or pressure waves)
 * Transverse S-waves (both body waves)
 * Surface waves – (Rayleigh and Love waves)

Speed of seismic waves
Propagation velocity of the seismic waves through solid rock ranges from approx. 3 km/s up to 13 km/s, depending on the density and elasticity of the medium. In the Earth's interior, the shock- or P-waves travel much faster than the S-waves (approx. relation 1.7:1). The differences in travel time from the epicenter to the observatory are a measure of the distance and can be used to image both sources of earthquakes and structures within the Earth. Also, the depth of the hypocenter can be computed roughly.

P-wave speed
 * Upper crust soils and unconsolidated sediments: 2-3 km per second
 * Upper crust solid rock: 3-6 km per second
 * Lower crust: 6-7 km per second
 * Deep mantle: 13 km per second.

S-waves speed
 * Light sediments: 2-3 km per second
 * Earths crust: 4-5 km per second
 * Deep mantle: 7 km per second

Seismic wave arrival
As a consequence, the first waves of a distant earthquake arrive at an observatory via the Earth's mantle.

On average, the kilometer distance to the earthquake is the number of seconds between the P- and S-wave times 8. Slight deviations are caused by inhomogeneities of subsurface structure. By such analysis of seismograms, the Earth's core was located in 1913 by Beno Gutenberg.

S-waves and later arriving surface waves do most of the damage compared to P-waves. P-waves squeeze and expand the material in the same direction they are traveling, whereas S-waves shake the ground up and down and back and forth.

Location and reporting
Earthquakes are not only categorized by their magnitude but also by the place where they occur. The world is divided into 754 Flinn–Engdahl regions (F-E regions), which are based on political and geographical boundaries as well as seismic activity. More active zones are divided into smaller F-E regions whereas less active zones belong to larger F-E regions.

Standard reporting of earthquakes includes its magnitude, date and time of occurrence, geographic coordinates of its epicenter, depth of the epicenter, geographical region, distances to population centers, location uncertainty, several parameters that are included in USGS earthquake reports (number of stations reporting, number of observations, etc.), and a unique event ID.

Although relatively slow seismic waves have traditionally been used to detect earthquakes, scientists realized in 2016 that gravitational measurement could provide instantaneous detection of earthquakes, and confirmed this by analyzing gravitational records associated with the 2011 Tohoku-Oki ("Fukushima") earthquake.

Effects

The effects of earthquakes include, but are not limited to, the following:

Shaking and ground rupture

Shaking and ground rupture are the main effects created by earthquakes, principally resulting in more or less severe damage to buildings and other rigid structures. The severity of the local effects depends on the complex combination of the earthquake magnitude, the distance from the epicenter, and the local geological and geomorphological conditions, which may amplify or reduce wave propagation. The ground-shaking is measured by ground acceleration.

Specific local geological, geomorphological, and geostructural features can induce high levels of shaking on the ground surface even from low-intensity earthquakes. This effect is called site or local amplification. It is principally due to the transfer of the seismic motion from hard deep soils to soft superficial soils and the effects of seismic energy focalization owing to the typical geometrical setting of such deposits.

Ground rupture is a visible breaking and displacement of the Earth's surface along the trace of the fault, which may be of the order of several meters in the case of major earthquakes. Ground rupture is a major risk for large engineering structures such as dams, bridges, and nuclear power stations and requires careful mapping of existing faults to identify any that are likely to break the ground surface within the life of the structure.

Soil liquefaction
Soil liquefaction occurs when, because of the shaking, water-saturated granular material (such as sand) temporarily loses its strength and transforms from a solid to a liquid. Soil liquefaction may cause rigid structures, like buildings and bridges, to tilt or sink into the liquefied deposits. For example, in the 1964 Alaska earthquake, soil liquefaction caused many buildings to sink into the ground, eventually collapsing upon themselves.

Human impacts

Physical damage from an earthquake will vary depending on the intensity of shaking in a given area and the type of population. Underserved and developing communities frequently experience more severe impacts (and longer lasting) from a seismic event compared to well-developed communities. Impacts may include:
 * Injuries and loss of life
 * Damage to critical infrastructure (short and long-term)
 * Roads, bridges, and public transportation networks
 * Water, power, sewer and gas interruption
 * Communication systems
 * Loss of critical community services including hospitals, police, and fire
 * General property damage
 * Collapse or destabilization (potentially leading to future collapse) of buildings

With these impacts and others, the aftermath may bring disease, a lack of basic necessities, mental consequences such as panic attacks and depression to survivors, and higher insurance premiums. Recovery times will vary based on the level of damage and the socioeconomic status of the impacted community.

Landslides
Earthquakes can produce slope instability leading to landslides, a major geological hazard. Landslide danger may persist while emergency personnel is attempting rescue work.

Fires

Earthquakes can cause fires by damaging electrical power or gas lines. In the event of water mains rupturing and a loss of pressure, it may also become difficult to stop the spread of a fire once it has started. For example, more deaths in the 1906 San Francisco earthquake were caused by fire than by the earthquake itself.

Tsunami

Tsunamis are long-wavelength, long-period sea waves produced by the sudden or abrupt movement of large volumes of water—including when an earthquake occurs at sea. In the open ocean, the distance between wave crests can surpass 100 km, and the wave periods can vary from five minutes to one hour. Such tsunamis travel 600–800 kilometers per hour (373–497 miles per hour), depending on water depth. Large waves produced by an earthquake or a submarine landslide can overrun nearby coastal areas in a matter of minutes. Tsunamis can also travel thousands of kilometers across open ocean and wreak destruction on far shores hours after the earthquake that generated them.

Ordinarily, subduction earthquakes under magnitude 7.5 do not cause tsunamis, although some instances of this have been recorded. Most destructive tsunamis are caused by earthquakes of magnitude 7.5 or more.

Floods
Floods may be secondary effects of earthquakes if dams are damaged. Earthquakes may cause landslips to dam rivers, which collapse and cause floods.

The terrain below the Sarez Lake in Tajikistan is in danger of catastrophic flooding if the landslide dam formed by the earthquake, known as the Usoi Dam, were to fail during a future earthquake. Impact projections suggest the flood could affect roughly five million people.

Prediction
Earthquake prediction is a branch of the science of seismology concerned with the specification of the time, location, and magnitude of future earthquakes within stated limits. Many methods have been developed for predicting the time and place in which earthquakes will occur. Despite considerable research efforts by seismologists, scientifically reproducible predictions cannot yet be made to a specific day or month. Popular belief holds earthquakes are preceded by earthquake weather, in the early morning.

Forecasting
While forecasting is usually considered to be a type of prediction, earthquake forecasting is often differentiated from earthquake prediction. Earthquake forecasting is concerned with the probabilistic assessment of general earthquake hazards, including the frequency and magnitude of damaging earthquakes in a given area over years or decades. For well-understood faults the probability that a segment may rupture during the next few decades can be estimated.

Earthquake warning systems have been developed that can provide regional notification of an earthquake in progress, but before the ground surface has begun to move, potentially allowing people within the system's range to seek shelter before the earthquake's impact is felt.

Preparedness
The objective of earthquake engineering is to foresee the impact of earthquakes on buildings, bridges, tunnels, roadways, and other structures, and to design such structures to minimize the risk of damage. Existing structures can be modified by seismic retrofitting to improve their resistance to earthquakes. Earthquake insurance can provide building owners with financial protection against losses resulting from earthquakes. Emergency management strategies can be employed by a government or organization to mitigate risks and prepare for consequences.

Artificial intelligence may help to assess buildings and plan precautionary operations. The Igor expert system is part of a mobile laboratory that supports the procedures leading to the seismic assessment of masonry buildings and the planning of retrofitting operations on them. It has been applied to assess buildings in Lisbon, Rhodes, and Naples.

Individuals can also take preparedness steps like securing water heaters and heavy items that could injure someone, locating shutoffs for utilities, and being educated about what to do when the shaking starts. For areas near large bodies of water, earthquake preparedness encompasses the possibility of a tsunami caused by a large earthquake.

Historical views

From the lifetime of the Greek philosopher Anaxagoras in the 5th century BCE to the 14th century CE, earthquakes were usually attributed to "air (vapors) in the cavities of the Earth." Thales of Miletus (625–547 BCE) was the only documented person who believed that earthquakes were caused by tension between the earth and water. Other theories existed, including the Greek philosopher Anaxamines' (585–526 BCE) beliefs that short incline episodes of dryness and wetness caused seismic activity. The Greek philosopher Democritus (460–371 BCE) blamed water in general for earthquakes. Pliny the Elder called earthquakes "underground thunderstorms".

Mythology and religion
In Norse mythology, earthquakes were explained as the violent struggle of the god Loki. When Loki, god of mischief and strife, murdered Baldr, god of beauty and light, he was punished by being bound in a cave with a poisonous serpent placed above his head dripping venom. Loki's wife Sigyn stood by him with a bowl to catch the poison, but whenever she had to empty the bowl the poison dripped on Loki's face, forcing him to jerk his head away and thrash against his bonds, which caused the earth to tremble.

In Greek mythology, Poseidon was the cause and god of earthquakes. When he was in a bad mood, he struck the ground with a trident, causing earthquakes and other calamities. He also used earthquakes to punish and inflict fear upon people as revenge.

In Japanese mythology, Namazu (鯰) is a giant catfish who causes earthquakes. Namazu lives in the mud beneath the earth and is guarded by the god Kashima who restrains the fish with a stone. When Kashima lets his guard fall, Namazu thrashes about, causing violent earthquakes.

In popular culture
In modern popular culture, the portrayal of earthquakes is shaped by the memory of great cities laid waste, such as Kobe in 1995 or San Francisco in 1906. Fictional earthquakes tend to strike suddenly and without warning. For this reason, stories about earthquakes generally begin with the disaster and focus on its immediate aftermath, as in Short Walk to Daylight (1972), The Ragged Edge (1968) or Aftershock: Earthquake in New York (1999). A notable example is Heinrich von Kleist's classic novella, The Earthquake in Chile, which describes the destruction of Santiago in 1647. Haruki Murakami's short fiction collection After the Quake depicts the consequences of the Kobe earthquake of 1995.

The most popular single earthquake in fiction is the hypothetical "Big One" expected of California's San Andreas Fault someday, as depicted in the novels Richter 10 (1996), Goodbye California (1977), 2012 (2009), and San Andreas (2015), among other works. Jacob M. Appel's widely anthologized short story, A Comparative Seismology, features a con artist who convinces an elderly woman that an apocalyptic earthquake is imminent.

Contemporary depictions of earthquakes in film are variable in the manner in which they reflect human psychological reactions to the actual trauma that can be caused to directly afflicted families and their loved ones. Disaster mental health response research emphasizes the need to be aware of the different roles of loss of family and key community members, loss of home and familiar surroundings, and loss of essential supplies and services to maintain survival. Particularly for children, the clear availability of caregiving adults who can protect, nourish, and clothe them in the aftermath of the earthquake and help them make sense of what has befallen them has been shown to be more important to their emotional and physical health than the simple giving of provisions. As was observed after other disasters involving destruction and loss of life and their media depictions, recently observed in the 2010 Haiti earthquake, it is also believed to be important not to pathologize the reactions to loss and displacement or disruption of governmental administration and services, but rather to validate the reactions to support constructive problem-solving and reflection.

Outside of earth
Phenomena similar to earthquakes have been observed in other planets (e.g., marsquakes on Mars) and on the Moon (e.g., moonquakes).

title: Earthquake


text:
Talk:Electroplating/Archive 1

I'm not convinved this is the reverse of a battery. The metal deposition occurs at the Cathode whilst metal depletion occurs at the Anode.

Hull Cell
The Hull Cell is a quite bit more clever than most give credit for. Effectively it's a 30-60-90 right triangle, sides are 1, 2,square root of 3. the front part is a square of unit 1 size. (if the volume of the electrolyte is correct it is also a cube of unit 1 size.) The power varies with the inverse square law. The squared distance and the square root of the triangle cancel out, so no square root is now required, and the power (voltage and amperage) is known at the closest point of the test piece. The falloff, volts, amps and resistance of the electroplating can now be calculated with really simple arithmetic. My point being, while the volume of electrolyte is important for the chemist running the test, the actual units used are arbitrary, and a Hull Cell can be made of any volume, an ideal Hull Cell will always have a 1,2,√3 ratios.

The 30° relation of the anode to the cathode is what's important as well as the 2x relationship in size of the cathode to the anode, the exterior of the tank is irrelevant, could as well be a test in the big electroplating bath, like an infinite baffle test for loudspeakers.

DIN 50957 varies quite a bit from the ideal triangle, tank dimensions are to theoretical sharp corners, 64, and 102 to the hypotenuse, resulting in a current distribution around 5.2 log X. https://www.researchgate.net/publication/271732116_Simulation_of_Current_Density_for_Electroplating_on_Silicon_Using_a_Hull_Cell

...onto conductive surface
How does the electroplating of plastic that Feynmann developed work? Josh Parris # 06:18, 21 October 2005 (UTC)
 * There are several techniques. all use a conductive layer put on the plastic and then plating on to that.

Prehistory in Electroplating
Is it worth dedicating a space to a loosely founded and very disputed speculation? There is much speculation about what the so-called Baghdad batteries are, and they being electrical batteries is just one hypothesis, which is not well supported; that these batteries were used for electroplating, something even more disputed; so we have, in this article, a reference to an unsupported hypothesis used to support a highly-debated hypothesis. Is this correct? I think that Prehistory should be removed from the article until some substantial support for the Baghdad battery theory is found. Paiconos 18:41, 4 May 2005 (UTC).
 * I tend to agree particulary as it has not yet been established that the artifact known as the Baghdad Battery, was in fact a battry at all! DV8 2XL 01:45, 29 August 2005 (UTC)

 * Well, no more input has been given, and the only comment is in agreement... I'll remove the Prehistory section. --Paiconos 16:56, 22 September 2005
 * The Baghdad Battery re-appeared in the History section sometime around Dec 2006. The original reason for its removal still stands, and the electro-plating theory of the batteries is even weaker now, from reading the Wiki page about the batteries.  I'm going to remove it again. Brianonn 07:14, 1 December 2007 (UTC)

 * It seems the Baghdad battery has made it back into the History section. I agree that this specious and speculative statement seems a non-viable entry, particularly for this page.  The provided reference link comes off as somewhat of a propaganda push-piece from a non-objective POV.  I'm deleting the entry, unless someone wants to modify it in a NPOV manner by emphasizing the extremely theoretical nature of the content.  —Preceding unsigned comment added by 98.169.103.134 (talk) 03:08, 16 December 2009 (UTC)

RF current
It is said in the article that "Silver plating is also popular for RF connectors because radio frequency current flows primarily on the surface of its conductor; the connector will thus have the strength of brass and the conductivity of silver."

As a student of physics, I have to point out that on any metal conductor, current always flows primarily on the surface of the conductor, be it RF current or any AC or DC current. It follows from the principles of electromagnetism.

What may motivate the use of silver in the surface might be that RF applications are more sensitive to losses than your regular electrical application (higher power emmiters to compensate for the losses cost more than higher power generators to compensate losses in other electrical applications), thus justifying the use of expensive silver coating to improve the quality of the conductors. HOWEVERRRRR, this is my speculation - although it does makes sense it is not based on any expert knowledge in the field. —The preceding unsigned comment was added by 213.22.225.220 (talk • contribs) 06:06, March 28, 2006 (UTC)
 * See Skin effect. In short, the depth of the conductive layer is frequency dependent with higher frequencies flowing shallower than low frequencies. --DV8 2XL 07:39, March 28, 2006

I stand corrected. Sorry about all the confusion. —The preceding unsigned comment was added by 213.22.225.220 (talk • contribs) 05:15, April 18, 2006 (UTC)

Brush plating
Some parts of the International Space Station were electroplated using a brush technique due to the impracticality of building a tank large enough to immerse the parts and because it wasn't required to plate the entire part. http://www.pfonline.com/articles/pfd0033.html —The preceding unsigned comment was added by 67.136.145.242 (talk • contribs) 20:39, December 3, 2006 (UTC)

Plated ware
I've done a complete rewrite of the related Plated ware article, which was an untouched 1911 Britannica entry and hence woefully out of date; as I'm not any kind of expert in commercial plating, is anyone in a position to take a look and make sure I haven't made any particularly stupid mistakes? -  Irides cent   (talk to me!)  12:57, 25 March 2007 (UTC)

Electrolytic bath
I wonder is there any buffer or compound need to be added to the solution of electroplating, in order to prevent the formation of porous metal? The article haven't mentioned about that.Superdvd (talk) 07:13, 15 June 2008 (UTC)

Hydrophobic or Hydrophilic (Cleanliness)?
"...ASTM F22 describes a version of this test. This test does not detect hydrophobic contaminants, but the electroplating process can displace these easily since the solutions are water-based." 189.42.228.115 (talk) 07:08, 15 February 2009 (UTC)

 * What is the question here? Wizard191 (talk) 21:08, 15 February 2009 (UTC)

Opening paragraph
The opening paragraph contains the following text:"(generally chromium to a combustion ampere of at least 563 volt)"Even to a layman, this looks suspiciously meaningless. Could someone who is knowledgeable about this subject either repair this text, or delete it? Many thanks. Dolphin51 (talk) 04:29, 24 July 2009 (UTC)

Johann Wilhelm Ritter
Is it possible to recheck the claim on this page and on Johann Wilhelm Ritter ? about the invention of electroplating ? thanks Mion (talk) 00:44, 19 November 2009 (UTC)

Picture might be good.
I find it too confusing without... :( 69.180.172.142 (talk) 22:55, 29 April 2010 (UTC)

Electroless deposition
Something wrong with "Electroless deposition" section, I guess... It says: Failed to parse (syntax error): M^{z+} + Red_{solution} \stackrel{\text{catalytic surface}} \Longrightarrow M_{solid deposite) + Oxy_{solution} — Preceding unsigned comment added by Charon77 (talk • contribs) 18:49, 17 April 2012 (UTC)

title: Talk:Electroplating/Archive 1