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Enrico Fermi

Enrico Fermi (29 September 1901 – 28 November 1954) was an Italian and naturalized American physicist, renowned for being the creator of the world's first nuclear reactor, the Chicago Pile-1, and a member of the Manhattan Project. He has been called the "architect of the nuclear age" and the "architect of the atomic bomb". He was one of very few physicists to excel in both theoretical physics and experimental physics. Fermi was awarded the 1938 Nobel Prize in Physics for his work on induced radioactivity by neutron bombardment and for the discovery of transuranium elements. With his colleagues, Fermi filed several patents related to the use of nuclear power, all of which were taken over by the US government. He made significant contributions to the development of statistical mechanics, quantum theory, and nuclear and particle physics.

Fermi's first major contribution involved the field of statistical mechanics. After Wolfgang Pauli formulated his exclusion principle in 1925, Fermi followed with a paper in which he applied the principle to an ideal gas, employing a statistical formulation now known as Fermi–Dirac statistics. Today, particles that obey the exclusion principle are called "fermions". Pauli later postulated the existence of an uncharged invisible particle emitted along with an electron during beta decay, to satisfy the law of conservation of energy. Fermi took up this idea, developing a model that incorporated the postulated particle, which he named the "neutrino". His theory, later referred to as Fermi's interaction and now called weak interaction, described one of the four fundamental interactions in nature. Through experiments inducing radioactivity with the recently discovered neutron, Fermi discovered that slow neutrons were more easily captured by atomic nuclei than fast ones, and he developed the Fermi age equation to describe this. After bombarding thorium and uranium with slow neutrons, he concluded that he had created new elements. Although he was awarded the Nobel Prize for this discovery, the new elements were later revealed to be nuclear fission products.

Fermi left Italy in 1938 to escape new Italian racial laws that affected his Jewish wife, Laura Capon. He emigrated to the United States, where he worked on the Manhattan Project during World War II. Fermi led the team at the University of Chicago that designed and built Chicago Pile-1, which went critical on 2 December 1942, demonstrating the first human-created, self-sustaining nuclear chain reaction. He was on hand when the X-10 Graphite Reactor at Oak Ridge, Tennessee went critical in 1943, and when the B Reactor at the Hanford Site did so the next year. At Los Alamos, he headed F Division, part of which worked on Edward Teller's thermonuclear "Super" bomb. He was present at the Trinity test on 16 July 1945, the first test of a full nuclear bomb explosion, where he used his Fermi method to estimate the bomb's yield.

After the war, he helped establish the Institute for Nuclear Studies at Chicago, and served on the General Advisory Committee, chaired by J. Robert Oppenheimer, which advised the Atomic Energy Commission on nuclear matters. After the detonation of the first Soviet fission bomb in August 1949, he strongly opposed the development of a hydrogen bomb on both moral and technical grounds. He was among the scientists who testified on Oppenheimer's behalf at the 1954 hearing that resulted in the denial of Oppenheimer's security clearance.

Fermi did important work in particle physics, especially related to pions and muons, and he speculated that cosmic rays arose when material was accelerated by magnetic fields in interstellar space. Many awards, concepts, and institutions are named after Fermi, including the Fermi 1 (breeder reactor), the Enrico Fermi Nuclear Generating Station,  the Enrico Fermi Award, the Enrico Fermi Institute, the Fermi National Accelerator Laboratory (Fermilab), the Fermi Gamma-ray Space Telescope, the Fermi paradox, and the synthetic element fermium, making him one of 16 scientists who have elements named after them.

Early life

Enrico Fermi was born in Rome, Italy, on 29 September 1901. He was the third child of Alberto Fermi, a division head in the Ministry of Railways, and Ida de Gattis, an elementary school teacher. His sister, Maria, was two years older, his brother Giulio a year older. After the two boys were sent to a rural community to be wet nursed, Enrico rejoined his family in Rome when he was two and a half. Although he was baptized a Roman Catholic in accordance with his grandparents' wishes, his family was not particularly religious; Enrico was an agnostic throughout his adult life. As a young boy, he shared the same interests as his brother Giulio, building electric motors and playing with electrical and mechanical toys. Giulio died during an operation on a throat abscess in 1915 and Maria died in an airplane crash near Milan in 1959.

At a local market in Campo de' Fiori, Fermi found a physics book, the 900-page Elementorum physicae mathematicae. Written in Latin by Jesuit Father Andrea Caraffa, a professor at the Collegio Romano, it presented mathematics, classical mechanics, astronomy, optics, and acoustics as they were understood at the time of its 1840 publication. With a scientifically inclined friend, Enrico Persico, Fermi pursued projects such as building gyroscopes and measuring the acceleration of Earth's gravity.

In 1914, Fermi, who used to often meet with his father in front of the office after work, met a colleague of his father called Adolfo Amidei, who would walk part of the way home with Alberto. Enrico had learned that Adolfo was interested in mathematics and physics and took the opportunity to ask Adolfo a question about geometry. Adolfo understood that the young Fermi was referring to projective geometry and then proceeded to give him a book on the subject written by Theodor Reye. Two months later, Fermi returned the book, having solved all the problems proposed at the end of the book, some of which Adolfo considered difficult. Upon verifying this, Adolfo felt that Fermi was "a prodigy, at least with respect to geometry", and further mentored the boy, providing him with more books on physics and mathematics. Adolfo noted that Fermi had a very good memory and thus could return the books after having read them because he could remember their content very well.

Scuola Normale Superiore in Pisa
Fermi graduated from high school in July 1918, having skipped the third year entirely. At Amidei's urging, Fermi learned German to be able to read the many scientific papers that were published in that language at the time, and he applied to the Scuola Normale Superiore in Pisa. Amidei felt that the Scuola would provide better conditions for Fermi's development than the Sapienza University of Rome could at the time. Having lost one son, Fermi's parents only reluctantly allowed him to live in the school's lodgings away from Rome for four years. Fermi took first place in the difficult entrance exam, which included an essay on the theme of "Specific characteristics of Sounds"; the 17-year-old Fermi chose to use Fourier analysis to derive and solve the partial differential equation for a vibrating rod, and after interviewing Fermi the examiner declared he would become an outstanding physicist.

At the Scuola Normale Superiore, Fermi played pranks with fellow student Franco Rasetti; the two became close friends and collaborators. Fermi was advised by Luigi Puccianti, director of the physics laboratory, who said there was little he could teach Fermi and often asked Fermi to teach him something instead. Fermi's knowledge of quantum physics was such that Puccianti asked him to organize seminars on the topic. During this time Fermi learned tensor calculus, a technique key to general relativity. Fermi initially chose mathematics as his major, but soon switched to physics. He remained largely self-taught, studying general relativity, quantum mechanics, and atomic physics.

In September 1920, Fermi was admitted to the physics department. Since there were only three students in the department—Fermi, Rasetti, and Nello Carrara—Puccianti let them freely use the laboratory for whatever purposes they chose. Fermi decided that they should research X-ray crystallography, and the three worked to produce a Laue photograph—an X-ray photograph of a crystal. During 1921, his third year at the university, Fermi published his first scientific works in the Italian journal Nuovo Cimento. The first was entitled "On the dynamics of a rigid system of electrical charges in translational motion" (Sulla dinamica di un sistema rigido di cariche elettriche in moto traslatorio). A sign of things to come was that the mass was expressed as a tensor—a mathematical construct commonly used to describe something moving and changing in three-dimensional space. In classical mechanics, mass is a scalar quantity, but in relativity, it changes with velocity. The second paper was "On the electrostatics of a uniform gravitational field of electromagnetic charges and on the weight of electromagnetic charges" (Sull'elettrostatica di un campo gravitazionale uniforme e sul peso delle masse elettromagnetiche). Using general relativity, Fermi showed that a charge has a weight equal to U/c2, where U was the electrostatic energy of the system, and c is the speed of light.

The first paper seemed to point out a contradiction between the electrodynamic theory and the relativistic one concerning the calculation of the electromagnetic masses, as the former predicted a value of 4/3 U/c2. Fermi addressed this the next year in a paper "Concerning a contradiction between electrodynamic and the relativistic theory of electromagnetic mass" in which he showed that the apparent contradiction was a consequence of relativity. This paper was sufficiently well-regarded that it was translated into German and published in the German scientific journal Physikalische Zeitschrift in 1922. That year, Fermi submitted his article "On the phenomena occurring near a world line" (Sopra i fenomeni che avvengono in vicinanza di una linea oraria) to the Italian journal I Rendiconti dell'Accademia dei Lincei. In this article he examined the Principle of Equivalence, and introduced the so-called "Fermi coordinates". He proved that on a world line close to the timeline, space behaves as if it were a Euclidean space.

Fermi submitted his thesis, "A theorem on probability and some of its applications" (Un teorema di calcolo delle probabilità ed alcune sue applicazioni), to the Scuola Normale Superiore in July 1922, and received his laurea at the unusually young age of 20. The thesis was on X-ray diffraction images. Theoretical physics was not yet considered a discipline in Italy, and the only thesis that would have been accepted was experimental physics. For this reason, Italian physicists were slow in embracing the new ideas like relativity coming from Germany. Since Fermi was quite at home in the lab doing experimental work, this did not pose insurmountable problems for him.

While writing the appendix for the Italian edition of the book Fundamentals of Einstein Relativity by August Kopff in 1923, Fermi was the first to point out that hidden inside the Einstein equation was an enormous amount of nuclear potential energy to be exploited. "It does not seem possible, at least in the near future", he wrote, "to find a way to release these dreadful amounts of energy—which is all to the good because the first effect of an explosion of such a dreadful amount of energy would be to smash into smithereens the physicist who had the misfortune to find a way to do it."

In 1924, Fermi was initiated into the Masonic Lodge "Adriano Lemmi" of the Grand Orient of Italy.

In 1923–1924, Fermi spent a semester studying under Max Born at the University of Göttingen, where he met Werner Heisenberg and Pascual Jordan. Fermi then studied in Leiden with Paul Ehrenfest from September to December 1924 on a fellowship from the Rockefeller Foundation obtained through the intercession of the mathematician Vito Volterra. Here Fermi met Hendrik Lorentz and Albert Einstein, and became friends with Samuel Goudsmit and Jan Tinbergen. From January 1925 to late 1926, Fermi taught mathematical physics and theoretical mechanics at the University of Florence, where he teamed up with Rasetti to conduct a series of experiments on the effects of magnetic fields on mercury vapor. He also participated in seminars at the Sapienza University of Rome, giving lectures on quantum mechanics and solid state physics. While giving lectures on the new quantum mechanics based on the remarkable accuracy of predictions of the Schrödinger equation, Fermi would often say, "It has no business to fit so well!"

After Wolfgang Pauli announced his exclusion principle in 1925, Fermi responded with a paper "On the quantization of the perfect monoatomic gas" (Sulla quantizzazione del gas perfetto monoatomico), in which he applied the exclusion principle to an ideal gas. The paper was especially notable for Fermi's statistical formulation, which describes the distribution of particles in systems of many identical particles that obey the exclusion principle. This was independently developed soon after by the British physicist Paul Dirac, who also showed how it was related to the Bose–Einstein statistics. Accordingly, it is now known as Fermi–Dirac statistics. After Dirac, particles that obey the exclusion principle are today called "fermions", while those that do not are called "bosons".

Professor in Rome

Professorships in Italy were granted by competition (concorso) for a vacant chair, the applicants being rated on their publications by a committee of professors. Fermi applied for a chair of mathematical physics at the University of Cagliari on Sardinia, but was narrowly passed over in favour of Giovanni Giorgi. In 1926, at the age of 24, he applied for a professorship at the Sapienza University of Rome. This was a new chair, one of the first three in theoretical physics in Italy, that had been created by the Minister of Education at the urging of professor Orso Mario Corbino, who was the university's professor of experimental physics, the director of the Institute of Physics, and a member of Benito Mussolini's cabinet. Corbino, who also chaired the selection committee, hoped that the new chair would raise the standard and reputation of physics in Italy. The committee chose Fermi ahead of Enrico Persico and Aldo Pontremoli, and Corbino helped Fermi recruit his team, which was soon joined by notable students such as Edoardo Amaldi, Bruno Pontecorvo, Ettore Majorana and Emilio Segrè, and by Franco Rasetti, whom Fermi had appointed as his assistant. They soon nicknamed the "Via Panisperna boys" after the street where the Institute of Physics was located.

Fermi married Laura Capon, a science student at the university, on 19 July 1928. They had two children: Nella, born in January 1931, and Giulio, born in February 1936. On 18 March 1929, Fermi was appointed a member of the Royal Academy of Italy by Mussolini, and on 27 April he joined the Fascist Party. He later opposed Fascism when the 1938 racial laws were promulgated by Mussolini in order to bring Italian Fascism ideologically closer to German Nazism. These laws threatened Laura, who was Jewish, and put many of Fermi's research assistants out of work.

During their time in Rome, Fermi and his group made important contributions to many practical and theoretical aspects of physics. In 1928, he published his Introduction to Atomic Physics (Introduzione alla fisica atomica), which provided Italian university students with an up-to-date and accessible text. Fermi also conducted public lectures and wrote popular articles for scientists and teachers in order to spread knowledge of the new physics as widely as possible. Part of his teaching method was to gather his colleagues and graduate students together at the end of the day and go over a problem, often from his own research. A sign of success was that foreign students now began to come to Italy. The most notable of these was the German physicist Hans Bethe, who came to Rome as a Rockefeller Foundation fellow, and collaborated with Fermi on a 1932 paper "On the Interaction between Two Electrons" (Über die Wechselwirkung von Zwei Elektronen).

At this time, physicists were puzzled by beta decay, in which an electron was emitted from the atomic nucleus. To satisfy the law of conservation of energy, Pauli postulated the existence of an invisible particle with no charge and little or no mass that was also emitted at the same time. Fermi took up this idea, which he developed in a tentative paper in 1933, and then a longer paper the next year that incorporated the postulated particle, which Fermi called a "neutrino". His theory, later referred to as Fermi's interaction, and still later as the theory of the weak interaction, described one of the four fundamental forces of nature. The neutrino was detected after his death, and his interaction theory showed why it was so difficult to detect. When he submitted his paper to the British journal Nature, that journal's editor turned it down because it contained speculations which were "too remote from physical reality to be of interest to readers". According to Fermi's biographer David N. Schwartz, it is at least strange that Fermi seriously requested publication from the journal, since at that time Nature only published short notes on articles of this kind, and was not suitable for the publication of even a new physical theory. More suitable, if anything, would have been the Proceedings of the Royal Society of London. He agrees with some scholars' hypothesis, according to which the rejection of the British magazine convinced his young colleagues (some of them Jews and leftist) to give up the boycott of German scientific magazines, after Hitler came to power in January 1933. Thus Fermi saw the theory published in Italian and German before it was published in English.

In the introduction to the 1968 English translation, physicist Fred L. Wilson noted that:"Fermi's theory, aside from bolstering Pauli's proposal of the neutrino, has a special significance in the history of modern physics. One must remember that only the naturally occurring β emitters were known at the time the theory was proposed. Later when positron decay was discovered, the process was easily incorporated within Fermi's original framework. On the basis of his theory, the capture of an orbital electron by a nucleus was predicted and eventually observed. With time, experimental data accumulated significantly. Although peculiarities have been observed many times in β decay, Fermi's theory always has been equal to the challenge. The consequences of the Fermi theory are vast. For example, β spectroscopy was established as a powerful tool for the study of nuclear structure. But perhaps the most influential aspect of this work of Fermi is that his particular form of the β interaction established a pattern that has been appropriate for the study of other types of interactions. It was the first successful theory of the creation and annihilation of material particles. Previously, only photons had been known to be created and destroyed."

In January 1934, Irène Joliot-Curie and Frédéric Joliot announced that they had bombarded elements with alpha particles and induced radioactivity in them. By March, Fermi's assistant Gian-Carlo Wick had provided a theoretical explanation using Fermi's theory of beta decay. Fermi decided to switch to experimental physics, using the neutron, which James Chadwick had discovered in 1932. In March 1934, Fermi wanted to see if he could induce radioactivity with Rasetti's polonium-beryllium neutron source. Neutrons had no electric charge, and so would not be deflected by the positively charged nucleus. This meant that they needed much less energy to penetrate the nucleus than charged particles, and so would not require a particle accelerator, which the Via Panisperna boys did not have.

Fermi had the idea to resort to replacing the polonium-beryllium neutron source with a radon-beryllium one, which he created by filling a glass bulb with beryllium powder, evacuating the air, and then adding 50 mCi of radon gas, supplied by Giulio Cesare Trabacchi. This created a much stronger neutron source, the effectiveness of which declined with the 3.8-day half-life of radon. He knew that this source would also emit gamma rays, but, on the basis of his theory, he believed that this would not affect the results of the experiment. He started by bombarding platinum, an element with a high atomic number that was readily available, without success. He turned to aluminium, which emitted an alpha particle and produced sodium, which then decayed into magnesium by beta particle emission. He tried lead, without success, and then fluorine in the form of calcium fluoride, which emitted an alpha particle and produced nitrogen, decaying into oxygen by beta particle emission. In all, he induced radioactivity in 22 different elements. Fermi rapidly reported the discovery of neutron-induced radioactivity in the Italian journal La Ricerca Scientifica on 25 March 1934.

The natural radioactivity of thorium and uranium made it hard to determine what was happening when these elements were bombarded with neutrons but, after correctly eliminating the presence of elements lighter than uranium but heavier than lead, Fermi concluded that they had created new elements, which he called ausenium and hesperium. The chemist Ida Noddack suggested that some of the experiments could have produced lighter elements than lead rather than new, heavier elements. Her suggestion was not taken seriously at the time because her team had not carried out any experiments with uranium or built the theoretical basis for this possibility. At that time, fission was thought to be improbable if not impossible on theoretical grounds. While physicists expected elements with higher atomic numbers to form from neutron bombardment of lighter elements, nobody expected neutrons to have enough energy to split a heavier atom into two light element fragments in the manner that Noddack suggested.

The Via Panisperna boys also noticed some unexplained effects. The experiment seemed to work better on a wooden table than on a marble tabletop. Fermi remembered that Joliot-Curie and Chadwick had noted that paraffin wax was effective at slowing neutrons, so he decided to try that. When neutrons were passed through paraffin wax, they induced a hundred times as much radioactivity in silver compared with when it was bombarded without the paraffin. Fermi guessed that this was due to the hydrogen atoms in the paraffin. Those in wood similarly explained the difference between the wooden and the marble tabletops. This was confirmed by repeating the effect with water. He concluded that collisions with hydrogen atoms slowed the neutrons. The lower the atomic number of the nucleus it collides with, the more energy a neutron loses per collision, and therefore the fewer collisions that are required to slow a neutron down by a given amount. Fermi realised that this induced more radioactivity because slow neutrons were more easily captured than fast ones. He developed a diffusion equation to describe this, which became known as the Fermi age equation.

In 1938, Fermi received the Nobel Prize in Physics at the age of 37 for his "demonstrations of the existence of new radioactive elements produced by neutron irradiation, and for his related discovery of nuclear reactions brought about by slow neutrons". After Fermi received the prize in Stockholm, he did not return home to Italy but rather continued to New York City with his family in December 1938, where they applied for permanent residency. The decision to move to America and become US citizens was due primarily to the racial laws in Italy.

Manhattan Project

Fermi arrived in New York City on 2 January 1939. He was immediately offered positions at five universities, and accepted one at Columbia University, where he had already given summer lectures in 1936. He received the news that in December 1938, the German chemists Otto Hahn and Fritz Strassmann had detected the element barium after bombarding uranium with neutrons, which Lise Meitner and her nephew Otto Frisch correctly interpreted as the result of nuclear fission. Frisch confirmed this experimentally on 13 January 1939. The news of Meitner and Frisch's interpretation of Hahn and Strassmann's discovery crossed the Atlantic with Niels Bohr, who was to lecture at Princeton University. Isidor Isaac Rabi and Willis Lamb, two Columbia University physicists working at Princeton, found out about it and carried it back to Columbia. Rabi said he told Enrico Fermi, but Fermi later gave the credit to Lamb: "I remember very vividly the first month, January, 1939, that I started working at the Pupin Laboratories because things began happening very fast. In that period, Niels Bohr was on a lecture engagement at the Princeton University and I remember one afternoon Willis Lamb came back very excited and said that Bohr had leaked out great news. The great news that had leaked out was the discovery of fission and at least the outline of its interpretation. Then, somewhat later that same month, there was a meeting in Washington where the possible importance of the newly discovered phenomenon of fission was first discussed in semi-jocular earnest as a possible source of nuclear power."

Noddack was proven right after all. Fermi had dismissed the possibility of fission on the basis of his calculations, but he had not taken into account the binding energy that would appear when a nuclide with an odd number of neutrons absorbed an extra neutron. For Fermi, the news came as a profound embarrassment, as the transuranic elements that he had partly been awarded the Nobel Prize for discovering had not been transuranic elements at all, but fission products. He added a footnote to this effect to his Nobel Prize acceptance speech.

The scientists at Columbia decided that they should try to detect the energy released in the nuclear fission of uranium when bombarded by neutrons. On 25 January 1939, in the basement of Pupin Hall at Columbia, an experimental team including Fermi conducted the first nuclear fission experiment in the United States. The other members of the team were Herbert L. Anderson, Eugene T. Booth, John R. Dunning, G. Norris Glasoe, and Francis G. Slack. The next day, the Fifth Washington Conference on Theoretical Physics began in Washington, D.C. under the joint auspices of George Washington University and the Carnegie Institution of Washington. There, the news on nuclear fission was spread even further, fostering many more experimental demonstrations.

French scientists Hans von Halban, Lew Kowarski, and Frédéric Joliot-Curie had demonstrated that uranium bombarded by neutrons emitted more neutrons than it absorbed, suggesting the possibility of a chain reaction. Fermi and Anderson did so too a few weeks later. Leó Szilárd obtained 200 kg of uranium oxide from Canadian radium producer Eldorado Gold Mines Limited, allowing Fermi and Anderson to conduct experiments with fission on a much larger scale. Fermi and Szilárd collaborated on the design of a device to achieve a self-sustaining nuclear reaction—a nuclear reactor. Owing to the rate of absorption of neutrons by the hydrogen in water, it was unlikely that a self-sustaining reaction could be achieved with natural uranium and water as a neutron moderator. Fermi suggested, based on his work with neutrons, that the reaction could be achieved with uranium oxide blocks and graphite as a moderator instead of water. This would reduce the neutron capture rate, and in theory make a self-sustaining chain reaction possible. Szilárd came up with a workable design: a pile of uranium oxide blocks interspersed with graphite bricks. Szilárd, Anderson, and Fermi published a paper on "Neutron Production in Uranium". But their work habits and personalities were different, and Fermi had trouble working with Szilárd.

Fermi was among the first to warn military leaders about the potential impact of nuclear energy, giving a lecture on the subject at the Navy Department on 18 March 1939. The response fell short of what he had hoped for, although the Navy agreed to provide $1,500 towards further research at Columbia. Later that year, Szilárd, Eugene Wigner, and Edward Teller sent the letter signed by Einstein to US president Franklin D. Roosevelt, warning that Nazi Germany was likely to build an atomic bomb. In response, Roosevelt formed the Advisory Committee on Uranium to investigate the matter.

The Advisory Committee on Uranium provided money for Fermi to buy graphite, and he built a pile of graphite bricks on the seventh floor of the Pupin Hall laboratory. By August 1941, he had six tons of uranium oxide and thirty tons of graphite, which he used to build a still larger pile in Schermerhorn Hall at Columbia.

The S-1 Section of the Office of Scientific Research and Development, as the Advisory Committee on Uranium was now known, met on 18 December 1941, with the US now engaged in World War II, making its work urgent. Most of the effort sponsored by the committee had been directed at producing enriched uranium, but Committee member Arthur Compton determined that a feasible alternative was plutonium, which could be mass-produced in nuclear reactors by the end of 1944. He decided to concentrate the plutonium work at the University of Chicago. Fermi reluctantly moved, and his team became part of the new Metallurgical Laboratory there.

The possible results of a self-sustaining nuclear reaction were unknown, so it seemed inadvisable to build the first nuclear reactor on the University of Chicago campus in the middle of the city. Compton found a location in the Argonne Woods Forest Preserve, about 20 miles from Chicago. Stone & Webster was contracted to develop the site, but the work was halted by an industrial dispute. Fermi then persuaded Compton that he could build the reactor in the squash court under the stands of the University of Chicago's Stagg Field. Construction of the pile began on 6 November 1942, and Chicago Pile-1 went critical on 2 December. The shape of the pile was intended to be roughly spherical, but as work proceeded Fermi calculated that criticality could be achieved without finishing the entire pile as planned.

This experiment was a landmark in the quest for energy, and it was typical of Fermi's approach. Every step was carefully planned, and every calculation was meticulously done. When the first self-sustained nuclear chain reaction was achieved, Compton made a coded phone call to James B. Conant, the chairman of the National Defense Research Committee."I picked up the phone and called Conant. He was reached at the President's office at Harvard University. "Jim," I said, "you'll be interested to know that the Italian navigator has just landed in the new world." Then, half apologetically, because I had led the S-l Committee to believe that it would be another week or more before the pile could be completed, I added, "the earth was not as large as he had estimated, and he arrived at the new world sooner than he had expected."

"Is that so," was Conant's excited response. "Were the natives friendly?" "Everyone landed safe and happy.""

To continue the research where it would not pose a public health hazard, the reactor was disassembled and moved to the Argonne Woods site. There Fermi directed experiments on nuclear reactions, reveling in the opportunities provided by the reactor's abundant production of free neutrons. The laboratory soon branched out from physics and engineering into using the reactor for biological and medical research. Initially, Argonne was run by Fermi as part of the University of Chicago, but it became a separate entity with Fermi as its director in May 1944.

When the air-cooled X-10 Graphite Reactor at Oak Ridge went critical on 4 November 1943, Fermi was on hand just in case something went wrong. The technicians woke him early so that he could see it happen. Getting X-10 operational was another milestone in the plutonium project. It provided data on reactor design, training for DuPont staff in reactor operation, and produced the first small quantities of reactor-bred plutonium. Fermi became an American citizen in July 1944, the earliest date the law allowed.

In September 1944, Fermi inserted the first uranium fuel slug into the B Reactor at the Hanford Site, the production reactor designed to breed plutonium in large quantities. Like X-10, it had been designed by Fermi's team at the Metallurgical Laboratory and built by DuPont, but it was much larger and was water-cooled. Over the next few days, 838 tubes were loaded, and the reactor went critical. Shortly after midnight on 27 September, the operators began to withdraw the control rods to initiate production. At first, all appeared to be well, but around 03:00, the power level started to drop and by 06:30 the reactor had shut down completely. The Army and DuPont turned to Fermi's team for answers. The cooling water was investigated to see if there was a leak or contamination. The next day the reactor suddenly started up again, only to shut down once more a few hours later. The problem was traced to neutron poisoning from xenon-135 or Xe-135, a fission product with a half-life of 9.1 to 9.4 hours. Fermi and John Wheeler both deduced that Xe-135 was responsible for absorbing neutrons in the reactor, thereby sabotaging the fission process. Fermi was recommended by colleague Emilio Segrè to ask Chien-Shiung Wu, as she prepared a printed draft on this topic to be published by the Physical Review. Upon reading the draft, Fermi and the scientists confirmed their suspicions: Xe-135 indeed absorbed neutrons, in fact it had a huge neutron cross-section. DuPont had deviated from the Metallurgical Laboratory's original design in which the reactor had 1,500 tubes arranged in a circle, and had added 504 tubes to fill in the corners. The scientists had originally considered this over-engineering a waste of time and money, but Fermi realized that if all 2,004 tubes were loaded, the reactor could reach the required power level and efficiently produce plutonium. In April 1943, Fermi raised with Robert Oppenheimer the possibility of using the radioactive byproducts from enrichment to contaminate the German food supply. The background was fear that the German atomic bomb project was already at an advanced stage, and Fermi was also skeptical at the time that an atomic bomb could be developed quickly enough. Oppenheimer discussed the "promising" proposal with Edward Teller, who suggested the use of strontium-90. James B. Conant and Leslie Groves were also briefed, but Oppenheimer wanted to proceed with the plan only if enough food could be contaminated with the weapon to kill half a million people.

In mid-1944, Oppenheimer persuaded Fermi to join his Project Y at Los Alamos, New Mexico. Arriving in September, Fermi was appointed an associate director of the laboratory, with broad responsibility for nuclear and theoretical physics, and was placed in charge of F Division, which was named after him. F Division had four branches: F-1 Super and General Theory under Teller, which investigated the "Super" (thermonuclear) bomb; F-2 Water Boiler under L. D. P. King, which looked after the "water boiler" aqueous homogeneous research reactor; F-3 Super Experimentation under Egon Bretscher; and F-4 Fission Studies under Anderson. Fermi observed the Trinity test on 16 July 1945 and conducted an experiment to estimate the bomb's yield by dropping strips of paper into the blast wave. He paced off the distance they were blown by the explosion, and calculated the yield as ten kilotons of TNT; the actual yield was about 18.6 kilotons.

Along with Oppenheimer, Compton, and Ernest Lawrence, Fermi was part of the scientific panel that advised the Interim Committee on target selection. The panel agreed with the committee that atomic bombs would be used without warning against an industrial target. Like others at the Los Alamos Laboratory, Fermi found out about the atomic bombings of Hiroshima and Nagasaki from the public address system in the technical area. Fermi did not believe that atomic bombs would deter nations from starting wars, nor did he think that the time was ripe for world government. He therefore did not join the Association of Los Alamos Scientists.

Postwar work
Fermi became the Charles H. Swift Distinguished Professor of Physics at the University of Chicago on 1 July 1945, although he did not depart the Los Alamos Laboratory with his family until 31 December 1945. He was elected a member of the US National Academy of Sciences in 1945. The Metallurgical Laboratory became the Argonne National Laboratory on 1 July 1946, the first of the national laboratories established by the Manhattan Project. The short distance between Chicago and Argonne allowed Fermi to work at both places. At Argonne he continued experimental physics, investigating neutron scattering with Leona Marshall. He also discussed theoretical physics with Maria Mayer, helping her develop insights into spin–orbit coupling that would lead to her receiving the Nobel Prize.

The Manhattan Project was replaced by the Atomic Energy Commission (AEC) on 1 January 1947. Fermi served on the AEC General Advisory Committee, an influential scientific committee chaired by Robert Oppenheimer. He also liked to spend a few weeks each year at the Los Alamos National Laboratory, where he collaborated with Nicholas Metropolis, and with John von Neumann on Rayleigh–Taylor instability, the science of what occurs at the border between two fluids of different densities.

After the detonation of the first Soviet fission bomb in August 1949, Fermi, along with Isidor Rabi, wrote a strongly worded report for the committee, opposing the development of a hydrogen bomb on moral and technical grounds. Nonetheless, Fermi continued to participate in work on the hydrogen bomb at Los Alamos as a consultant. Along with Stanislaw Ulam, he calculated that not only would the amount of tritium needed for Teller's model of a thermonuclear weapon be prohibitive, but a fusion reaction could still not be assured to propagate even with this large quantity of tritium. Fermi was among the scientists who testified on Oppenheimer's behalf at the Oppenheimer security hearing in 1954 that resulted in the denial of Oppenheimer's security clearance.

In his later years, Fermi continued teaching at the University of Chicago, where he was a founder of what later became the Enrico Fermi Institute. His PhD students in the postwar period included Owen Chamberlain, Geoffrey Chew, Jerome Friedman, Marvin Goldberger, Tsung-Dao Lee, Arthur Rosenfeld and Sam Treiman. Jack Steinberger was a graduate student, and Mildred Dresselhaus was highly influenced by Fermi during the year she overlapped with him as a PhD student. Fermi conducted important research in particle physics, especially related to pions and muons. He made the first predictions of pion-nucleon resonance, relying on statistical methods, since he reasoned that exact answers were not required when the theory was wrong anyway. In a paper coauthored with Chen Ning Yang, he speculated that pions might actually be composite particles. The idea was elaborated by Shoichi Sakata. It has since been supplanted by the quark model, in which the pion is made up of quarks, which completed Fermi's model, and vindicated his approach.

Fermi wrote a paper "On the Origin of Cosmic Radiation" in which he proposed that cosmic rays arose through material being accelerated by magnetic fields in interstellar space, which led to a difference of opinion with Teller. Fermi examined the issues surrounding magnetic fields in the arms of a spiral galaxy. He mused about what is now referred to as the "Fermi paradox": the contradiction between the presumed probability of the existence of extraterrestrial life and the fact that contact has not been made.

Toward the end of his life, Fermi questioned his faith in society at large to make wise choices about nuclear technology. He said:

"Some of you may ask, what is the good of working so hard merely to collect a few facts which will bring no pleasure except to a few long-haired professors who love to collect such things and will be of no use to anybody because only few specialists at best will be able to understand them? In answer to such question[s] I may venture a fairly safe prediction.

The history of science and technology has consistently taught us that scientific advances in basic understanding have sooner or later led to technical and industrial applications that have revolutionized our way of life. It seems to me improbable that this effort to get at the structure of matter should be an exception to this rule. What is less certain, and what we all fervently hope, is that man will soon grow sufficiently adult to make good use of the powers that he acquires over nature."

Death
Fermi underwent what was called an "exploratory" operation in Billings Memorial Hospital in October 1954, after which he returned home. Fifty days later he died of inoperable stomach cancer in his home in Chicago. He was 53. Fermi suspected working near the nuclear pile involved great risk but he pressed on because he felt the benefits outweighed the risks to his personal safety. Two of his graduate student assistants working near the pile also died of cancer.

A memorial service was held at the University of Chicago chapel, where colleagues Samuel K. Allison, Emilio Segrè, and Herbert L. Anderson spoke to mourn the loss of one of the world's "most brilliant and productive physicists." His body was interred at Oak Woods Cemetery where a private graveside service for the immediate family took place presided by a Lutheran chaplain.

Legacy
Fermi received numerous awards in recognition of his achievements, including the Matteucci Medal in 1926, the Nobel Prize for Physics in 1938, the Hughes Medal in 1942, the Franklin Medal in 1947, and the Rumford Prize in 1953. He was awarded the Medal for Merit in 1946 for his contribution to the Manhattan Project. Fermi was elected member of the American Philosophical Society in 1939 and a Foreign Member of the Royal Society (FRS) in 1950. The Basilica of Santa Croce, Florence, known as the Temple of Italian Glories for its many graves of artists, scientists and prominent figures in Italian history, has a plaque commemorating Fermi. In 1999, Time named Fermi on its list of the top 100 persons of the twentieth century. Fermi was widely regarded as an unusual case of a 20th-century physicist who excelled both theoretically and experimentally. Chemist and novelist C. P. Snow wrote, "if Fermi had been born a few years earlier, one could well imagine him discovering Rutherford's atomic nucleus, and then developing Bohr's theory of the hydrogen atom. If this sounds like hyperbole, anything about Fermi is likely to sound like hyperbole".

Fermi was known as an inspiring teacher and was noted for his attention to detail, simplicity, and careful preparation of his lectures. Later, his lecture notes were transcribed into books. His papers and notebooks are today in the University of Chicago. Victor Weisskopf noted how Fermi "always managed to find the simplest and most direct approach, with the minimum of complication and sophistication." He disliked complicated theories, and while he had great mathematical ability, he would never use it when the job could be done much more simply. He was famous for getting quick and accurate answers to problems that would stump other people. Later on, his method of getting approximate and quick answers through back-of-the-envelope calculations became informally known as the "Fermi method", and is widely taught.

Fermi was fond of pointing out that when Alessandro Volta was working in his laboratory, Volta had no idea where the study of electricity would lead. Fermi is generally remembered for his work on nuclear power and nuclear weapons, especially the creation of the first nuclear reactor, and the development of the first atomic and hydrogen bombs. His scientific work has stood the test of time. This includes his theory of beta decay, his work with non-linear systems, his discovery of the effects of slow neutrons, his study of pion-nucleon collisions, and his Fermi–Dirac statistics. His speculation that a pion was not a fundamental particle pointed the way towards the study of quarks and leptons.

"As a person, Fermi seemed simplicity itself. He was extraordinarily vigorous and loved games and sport. On such occasions his ambitious nature became apparent. He played tennis with considerable ferocity and when climbing mountains acted rather as a guide. One might have called him a benevolent dictator. I remember once at the top of a mountain Fermi got up and said: "Well, it is two minutes to two, let's all leave at two o'clock"; and of course, everybody got up faithfully and obediently. This leadership and self-assurance gave Fermi the name of "The Pope" whose pronouncements were infallible in physics. He once said: "I can calculate anything in physics within a factor 2 on a few sheets; to get the numerical factor in front of the formula right may well take a physicist a year to calculate, but I am not interested in that." His leadership could go so far that it was a danger to the independence of the person working with him. I recollect once, at a party at his house when my wife cut the bread, Fermi came along and said he had a different philosophy on bread-cutting and took the knife out of my wife's hand and proceeded with the job because he was convinced that his own method was superior. But all this did not offend at all, but rather charmed everybody into liking Fermi. He had very few interests outside physics and when he once heard me play on Teller's piano he confessed that his interest in music was restricted to simple tunes."

- Egon Bretscher

Things named after Fermi

Many things bear Fermi's name. These include the Fermilab particle accelerator and physics lab in Batavia, Illinois, which was renamed in his honor in 1974, and the Fermi Gamma-ray Space Telescope, which was named after him in 2008, in recognition of his work on cosmic rays. Three nuclear reactor installations have been named after him: the Fermi 1 and Fermi 2 nuclear power plants in Newport, Michigan, the Enrico Fermi Nuclear Power Plant at Trino Vercellese in Italy, and the RA-1 Enrico Fermi research reactor in Argentina. A synthetic element isolated from the debris of the 1952 Ivy Mike nuclear test was named fermium, in honor of Fermi's contributions to the scientific community. This makes him one of 16 scientists who have elements named after them.

Since 1956, the United States Atomic Energy Commission has named its highest honor, the Fermi Award, after him. Recipients of the award have included Otto Hahn, Robert Oppenheimer, Edward Teller and Hans Bethe.

Publications
For a full list of his papers, see pages 75–78 in ref.
 * (with Edoardo Amaldi)
 * (with Edoardo Amaldi)
 * (with Edoardo Amaldi)
 * (with Edoardo Amaldi)
 * (with Edoardo Amaldi)
 * (with Edoardo Amaldi)

title: Enrico Fermi


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Entente

Entente, meaning a diplomatic "understanding", may refer to a number of agreements:

History

 * Entente (alliance), a type of treaty or military alliance where the signatories promise to consult each other or to cooperate with each other in case of a crisis or military action
 * Entente Cordiale (1904) between France and the United Kingdom
 * Anglo-Russian Entente (1907) between the United Kingdom and Russia
 * Triple Entente, an informal understanding between the Russian Empire, the French Third Republic and the United Kingdom of Great Britain and Ireland, built upon the Franco-Russian Alliance (1894), the Entente Cordiale (1904), and the Anglo-Russian Entente (1907)
 * Allies of World War I, sometimes referred to as "The Entente", "The Entente Powers", or "The Entente Forces"
 * Little Entente (1920–1938), between Czechoslovakia, Romania, and the Kingdom of Yugoslavia
 * Balkan Entente (1934–1938), between Greece, Turkey, Romania and Yugoslavia
 * Baltic Entente (1934–1939), between Lithuania, Latvia, and Estonia
 * Conseil de l'Entente (1959), between Côte d'Ivoire, Burkina Faso, Benin, Niger, and (in 1966) Togo
 * Entente frugale (beginning 2010), cooperation between the British and French governments

Other

 * Entente Florale Europe, an international horticultural competition
 * International Entente Against the Third International, an international anticommunist organisation founded in 1924
 * International Entente of Radical and Similar Democratic Parties, a political international existed in 1923–1938
 * The Entente: Battlefields WW1, a 2004 video game

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

title: Entente


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Editor war

The editor war is the rivalry between users of the Emacs and vi (now usually Vim, or more recently Neovim) text editors. The rivalry has become an enduring part of hacker culture and the free software community.

The Emacs versus vi debate was one of the original "holy wars" conducted on Usenet groups, with many flame wars fought between those insisting that their editor of choice is the paragon of editing perfection, and insulting the other, since at least 1985. Related battles have been fought over operating systems, programming languages, version control systems, and even source code indent style.

Evolution

Many small editors that were based on or derived from vi in the past were successful. This was because it was crucial to preserve the memory that was, at the time, relatively sparsely available. As computers have become more powerful, many vi clones, Vim in particular, have grown in size and code complexity. These vi variants of today, as with the old lightweight Emacs variants, tend to have many of the perceived benefits and drawbacks of the opposing side. For example, Vim without any extensions requires about ten times the disk space required by vi, and recent versions of Vim can have more extensions and run slower than Emacs. In The Art of Unix Programming, Eric S. Raymond called Vim's supposed light weight when compared with Emacs "a shared myth". Moreover, with the large amounts of RAM in modern computers, both Emacs and vi are lightweight compared to large integrated development environments such as Eclipse, which tend to draw derision from Emacs and vi users alike.

Tim O'Reilly said, in 1999, that O'Reilly Media's tutorial on vi sells twice as many copies as that on Emacs (but noted that Emacs came with a free manual). Many programmers use either Emacs and vi or their various offshoots, including Linus Torvalds who uses MicroEMACS. Also in 1999, vi creator Bill Joy said that vi was "written for a world that doesn't exist anymore" and stated that Emacs was written on much more capable machines with faster displays so they could have "funny commands with the screen shimmering and all that, and meanwhile, I'm sitting at home in sort of World War II surplus housing at Berkeley with a modem and a terminal that can just barely get the cursor off the bottom line".

In addition to Emacs and vi workalikes, pico and its free and open-source clone nano and other text editors such as ne often have their own third-party advocates in the editor wars, though not to the extent of Emacs and vi.

, both Emacs and vi can lay claim to being among the longest-lived application programs of all time, as well as being the two most commonly used text editors on Linux and Unix. Many operating systems, especially Linux and BSD derivatives, bundle multiple text editors with the operating system to cater to user demand. For example, a default installation of macOS contains ed, pico (nano before MacOS Ventura 12.3), TextEdit, and Vim. Frequently, at some point in the discussion, someone will point out that ed is the standard text editor.

Humor
The Church of Emacs, formed by Emacs and the GNU Project's creator Richard Stallman, is a parody religion. While it refers to vi as the "editor of the beast" (vi-vi-vi being 6-6-6 in Roman numerals), it does not oppose the use of vi; rather, it calls proprietary software anathema. ("Using a free version of vi is not a sin but a penance." ) The Church of Emacs has its own newsgroup, alt.religion.emacs, that has posts purporting to support this belief system.

Stallman has referred to himself as St IGNU−cius, a saint in the Church of Emacs.

Supporters of vi have created an opposing Cult of vi, argued by the more hard-line Emacs users to be an attempt to "ape their betters".

Regarding vi's modal nature (a common point of frustration for new users) some Emacs users joke that vi has two modes – "beep repeatedly" and "break everything". vi users enjoy joking that Emacs's key-sequences induce carpal tunnel syndrome, or mentioning one of many satirical expansions of the acronym EMACS, such as "Escape Meta Alt Control Shift" (a jab at Emacs's reliance on modifier keys) or "Eight Megabytes And Constantly Swapping" (in a time when that was a great amount of memory) or "EMACS Makes Any Computer Slow" (a recursive acronym like those Stallman uses) or "Eventually Munches All Computer Storage", in reference to Emacs's high system resource requirements. GNU EMACS has been expanded to "Generally Not Used, Except by Middle-Aged Computer Scientists" referencing its most ardent fans, and its declining usage among younger programmers compared to more graphically oriented editors such as Atom, BBEdit, Sublime Text, TextMate, and Visual Studio Code.

As a poke at Emacs' creeping featurism, vi advocates have been known to describe Emacs as "a great operating system, lacking only a decent editor". Emacs advocates have been known to respond that the editor is actually very good, but the operating system could use improvement (referring to Emacs' famous lack of concurrency, which has now been added ).

A game among UNIX users, either to test the depth of an Emacs user's understanding of the editor or to poke fun at the complexity of Emacs, involved predicting what would happen if a user held down a modifier key (such as or ) and typed their own name. This game humor originated with users of the older TECO editor, which was the implementation basis, via macros, of the original Emacs.

Due to how one exits vi (":q", among others), hackers joke about a proposed method of creating a pseudorandom character sequence by having a user unfamiliar with vi seated in front of an open editor and asking them to exit the program.

The Google search engine also joined in on the joke by having searches for vi resulting in the question "Did you mean: emacs" prompted at the top of the page, and searches for emacs resulting in "Did you mean: vi".

In the web series A Murder at the End of the World, there is a scene referencing the editor wars where a character asks a woman if she uses Vi or Emacs.

title: Editor war


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Talk:Editor war

Current?? state of the editor war
The section headed "Current state of the editor war seems to refer largely to 1999. That's not really current at the time of writing (2014). Perhaps it ought to be renamed or updated? -- Preceding unsigned comment added by 2001:630:D0:F111:BDB8:5CD6:8D81:39B8 (talk) 08:59, 26 June 2014 (UTC)

 * My impression is that standalone (un-integrated) plaintext editor programs have declined in practical importance over the last 15 years. They still have their advocates, are often included in standard software distributions, and are essential for certain highly-specialized tasks, but purely pragmatic programmers (who weren't necessarily around in the 1990s, and use whatever tool helps them code fastest) often don't use them... AnonMoos (talk) 03:44, 27 June 2014 (UTC)

 * WP:OR... Huihermit (talk) 05:41, 27 June 2014 (UTC)
 * And short-sighted. Whatever fad languages these IDEs are integrated with won't necessarily be the best choice in 10 years. And the "pragmatic" programmers will have to learn another editor, along with another language. -- Preceding unsigned comment added by OMPIRE (talk o  contribs) 14:09, 16 September 2014 (UTC)

2020

 * The vi/vim stackexchange seems pretty active. 27k users. Compare to travel at 84k and 296k Phissy (talk) --Preceding undated comment added 20:20, 1 September 2020 (UTC)

The Other Editor War
Interesting that there doesn't seem to exist any article about the other editor war : The "Wordprocessor War" between MS Word and WordPerfect. It almost sounds as if the Editor War described here was so much more important that no-one thought of making an Wikipedia article on that other Editor war, cynically speaking ... Alrik Fassbauer (talk) 12:28, 5 August 2017 (UTC)

 * It was a well-known issue among various groups of computer programmers during most of the 1980s and 1990s (including programmers who were likely to be connected to the early Internet and shape early Internet culture), and it only slowly trailed off. By contrast, MS-Word vs. WordPerfect was a struggle between commercial corporations (not ordinary users), and MS-Word crushed WordPerfect fairly quickly after Windows and office-suite bundling began to catch on... AnonMoos (talk) 02:25, 6 August 2017 (UTC)

GNU/Linux?
In an article where a GNU product is being discussed, it's sad to see that the operating system is being referred to as Linux instead of GNU/Linux. Please give credit to the FSF where credit is due. Linux is just the kernel, not the operating system. Sandy2712 (talk) 09:20, 31 March 2021 (UTC)
 * See MOS:LINUX. Linux is the name of the operating system and is also the name of the Kernel per overwhelming usage in the English language. GNU/Linux is not the commonly accepted term for Linux and is not used on Wikipedia except where it's part of the distro's name such as Parabola GNU/Linux. - Aoidh (talk) 18:54, 9 April 2021 (UTC)

Vi benefits
-Vi utility: Vi is useful for raw to the metal editing on small devices with minimal power. It appears Emacs is a larger system possibly not applicable to low level device editing.

-Vi cost respect of FOSS: Vi was distributed for free, whereas Emacs could cost hundreds of dollars. Source: https://en.wikipedia.org/wiki/Vi_(text_editor) -> History -> Distribution -> paragraph 1. Eiger3970 (talk) 22:51, 16 January 2024 (UTC)

 * I am not sure if the article is talking about GNU Emacs or the original Emacs, but I don't think this a valid point anymore because GNU Emacs (the most widely used version of Emacs) is distributed gratis on the net. Tusharhero (talk) 08:56, 17 January 2024 (UTC)

 * The original Emacs was TECO macros. The commercial (non-free-licensed) version was Unipress Gosling Emacs, now defunct... AnonMoos (talk) 02:56, 22 January 2024 (UTC)

title: Talk:Editor war


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Organization of the Eastern Orthodox Church

The Eastern Orthodox Church, officially the Orthodox Catholic Church and commonly known simply as the Orthodox Church is a communion composed of up to seventeen separate autocephalous (self-governing) hierarchical churches that profess Eastern Orthodoxy and recognise each other as canonical (regular) Eastern Orthodox Christian churches.

Each constituent church is self-governing; its highest-ranking bishop called the primate (a patriarch, a metropolitan or an archbishop) reports to no higher authority. Each regional church is composed of constituent eparchies (or dioceses) ruled by bishops. Some autocephalous churches have given an eparchy or group of eparchies with varying degrees of autonomy (meaning they have limited self-government). Such autonomous churches maintain varying levels of dependence on their mother church, usually defined in a tomos or another document of autonomy. In many cases, autonomous churches are almost completely self-governing, with the mother church retaining only the right to appoint the highest-ranking bishop (often an archbishop or metropolitan) of the autonomous church.

Normal governance is enacted through a synod of bishops within each church.

Church governance
The Eastern Orthodox Church is decentralised, having no central authority, earthly head or a single bishop in a leadership role. Thus, the Eastern Orthodox use a synodical system canonically, which is significantly different from the hierarchical organisation of the Catholic Church that follows the doctrine of papal supremacy. References to the Ecumenical Patriarch of Constantinople as a sole authoritative leader are an erroneous interpretation of his title “first among equals". His title is of honor rather than authority and in fact the Ecumenical Patriarch has no direct authority over churches other than the Constantinopolitan Church. The Ecumenical Patriarch's unique role is sometimes referred to as being the "spiritual leader" of the Eastern Orthodox Church, although even this is disputed.

The autocephalous churches are normally in full communion with each other, so any priest of any of those churches may lawfully minister to any member of any of them, and no member of any is excluded from any form of worship in any of the others, including the reception of the Eucharist. However, there have been varying instances in the history of the Eastern Orthodox Church where communion has been broken between member churches for short periods, particularly over autocephaly issues or disagreements over ecumenism with other Christian denominations.

In early Christian history, the church existed only as a single denomination of five communing churches ruled by five patriarchs: the bishops of Rome, Constantinople, Alexandria, Antioch, and Jerusalem, collectively referred to as the Pentarchy. Each of the five patriarchs had jurisdiction over bishops in a specified geographic region which did not overlap with the jurisdiction of another patriarch. This continued until 927, when the Bulgarian Patriarchate became the first newly promoted patriarchate to join the original five.

Historically, the Patriarch of Rome was considered to be the "first in place of honor" among the five patriarchs. Disagreement about the limits of his authority was one of the causes of the Great Schism, conventionally dated to the year 1054, which split the previously unified Church into the Roman Catholic Church in the West, headed by the Pope, and the Orthodox Catholic Church (more commonly known today as the Eastern Orthodox Church), led by the four eastern patriarchs. After the schism, the honorary primacy of the Bishop of Rome shifted to the Patriarch of Constantinople, who had previously been accorded second-place rank at the First Council of Constantinople.

In the 5th century, Oriental Orthodoxy separated from Chalcedonian Christianity (and is therefore separate from both the Eastern Orthodox Church and Roman Catholic Church), well before the 11th century Great Schism. It should not be confused with Eastern Orthodoxy or Roman Catholicism.

Autocephalous Eastern Orthodox churches
Ranked in order of seniority, with the year of independence (autocephaly) given in parentheses, where applicable. There are a total of 17 autocephalous Eastern Orthodox churches which are recognized to various degrees among the communion of the Eastern Orthodox Church.

Canonicity refers to the state of being in communion with the larger Eastern Orthodox Church (making the church in question undisputedly a constituent of the Eastern Orthodox Church), whereas autocephaly refers to the state of being more or less self-governing. Canonicity is binary (two churches are either in communion or not) while autocephaly exists on a spectrum. Disputes over autocephaly often lead to short-term breaks in communion for political reasons. These short-term breaks are typically not due to differences in doctrine or theology.

Four ancient patriarchates

 * 1) Ecumenical Patriarchate of Constantinople (independence in AD 330; elevated to the rank of autocephalous Patriarchate in 381; elevated 451 to second see; became first see due to division from the See of Rome in the Great Schism of 1054)
 * 2) Greek Orthodox Patriarchate of Alexandria
 * 3) Greek Orthodox Patriarchate of Antioch
 * 4) Greek Orthodox Patriarchate of Jerusalem (independence in AD 451, elevated to the rank of autocephalous Patriarchate in 451)

The four ancient Eastern Orthodox Patriarchates, along with the See of Rome, formed the historical Pentarchy, and remained in communion with each other after the East-West Schism in 1054. The concept of the Pentarchy and the title of "Patriarch" itself, as opposed to Archbishop or Exarch, is attributed to St Justinian in AD 531.

National patriarchates

 * 1) Bulgarian Orthodox Church (870, Patriarchate since 918/919, recognised by the Patriarchate of Constantinople in 927)
 * 2) Georgian Orthodox Church (Patriarchate since 1010)
 * 3) Serbian Orthodox Church (1219, Patriarchate since 1346)
 * 4) Russian Orthodox Church (1448, recognised in 1589)
 * 5) Romanian Orthodox Church (1872, recognised in 1885, Patriarchate since 1925)

Autocephalous archbishoprics
Note:
 * 1) Church of Cyprus (recognised in 431)
 * 2) Church of Greece (1833, recognised in 1850)
 * 3) Albanian Orthodox Church (1922, recognised in 1937)
 * 4) Macedonian Orthodox Church (1967, recognised in 2022)

Autocephalous metropolises
Note:
 * 1) Polish Orthodox Church (1924)
 * 2) Orthodox Church of the Czech Lands and Slovakia (1951)

Universally recognized as canonical, autocephaly disputed

 * 1) Orthodox Church in America (granted by the Russian Orthodox Church in 1970 and recognized by five other churches, but not recognised by the Ecumenical Patriarchate or remaining Churches. Canonicity universally recognized.)

Canonical and spiritual independence status disputed

 * 1) Ukrainian Orthodox Church (Moscow Patriarchate) (1992 as Ukrainian Orthodox Church, split from Ukrainian Orthodox Church in 1992 allying with Russian Orthodox Church, declared independence from the Russian Orthodox Church on 27 May 2022, recognised as independent by the Georgian Orthodox Church on 24 March 2023. Its status as an independent church rejected by the majority of churches)

Canonical and autocephalous status disputed

 * 1) Orthodox Church of Ukraine (1992 as Ukrainian Orthodox Church, autocephaly from 15 December 2018, recognised by the Ecumenical Patriarchate on 5 January 2019 and 3 other churches. Its autocephaly and canonicity rejected  by remaining Churches, including its rival Ukrainian Churches.)

Canonical and autocephalous status unrecognised

 * 1) A minority of the Ukrainian Orthodox Church – Kyiv Patriarchate led by Filaret (Denysenko) split again in 2019, following internal disputes and concerns as to whether the autocephaly granted by the Ecumenical Patriarchate amounted to true autocephaly due to the conditions imposed. They are not recognized by any church, including its rival Ukrainian Churches.
 * 2) The Old Calendarists and True Orthodox split from their local church and are not recognized as canonical, nor do they recognize any of the above churches as canonical. Some maintain communion with the Kyiv Patriarchate under Filaret.

Internal ranking
The typical order that the four ancient churches appear in the diptychs is the same order given above. While every major church places the four ancient churches in their diptychs before the other autocephalous churches, this order may still differ slightly. For example, in the diptychs of the Russian Orthodox Church and some of its daughter churches (e.g., the Orthodox Church in America), the ranking of the five junior patriarchates is: Russia, Georgia, Serbia, Romania, Bulgaria. The ranking of the archbishoprics is the same, with the Church of Cyprus being the only ancient one (AD 431).

Autonomous Eastern Orthodox churches

 * Under the Ecumenical Patriarchate of Constantinople
 * Estonian Apostolic Orthodox Church (autonomy recognised by the Ecumenical Patriarchate but not by the Russian Orthodox Church)
 * Orthodox Church of Finland

 * Under the Greek Orthodox Church of Antioch
 * Antiochian Orthodox Christian Archdiocese of North America
 * Antiochian Orthodox Archdiocese of São Paulo and All Brazil

 * Under the Greek Orthodox Church of Jerusalem
 * Church of Sinai

 * Under the Russian Orthodox Church
 * Belarusian Orthodox Church
 * Metropolis of Chișinău and All Moldova
 * Orthodox Church in Japan (autonomy recognised by the Russian Orthodox Church but not by the Ecumenical Patriarchate)
 * Chinese Orthodox Church (autonomy recognised by the Russian Orthodox Church but not by the Ecumenical Patriarchate)

 * Under the Romanian Orthodox Church
 * Metropolis of Bessarabia
 * Romanian Orthodox Metropolis of the Americas
 * Romanian Orthodox Metropolis of Western and Southern Europe

Semi-autonomous churches

 * Under the Ecumenical Patriarchate of Constantinople
 * Church of Crete
 * Under the Russian Orthodox Church
 * Estonian Orthodox Church of the Moscow Patriarchate
 * Russian Orthodox Church Outside Russia

Limited self-government (not autonomy)

 * Under the Ecumenical Patriarchate of Constantinople
 * Monastic community of Mount Athos
 * Greek Orthodox Archdiocese of Italy and Malta
 * Korean Orthodox Church
 * Exarchate of the Philippines
 * American Carpatho-Russian Orthodox Diocese
 * Ukrainian Orthodox Church of Canada
 * Ukrainian Orthodox Church of the USA

 * Under the Russian Orthodox Church
 * Archdiocese of Russian Orthodox churches in Western Europe

 * Under the Romanian Orthodox Church
 * Ukrainian Orthodox Vicariate Sighetu Marmației

True Orthodox
True Orthodox Christians are groups of traditionalist Eastern Orthodox churches which have severed communion since the 1920s with the mainstream Eastern Orthodox churches for various reasons, such as calendar reform, the involvement of mainstream Eastern Orthodox in ecumenism, or the refusal to submit to the authority of mainstream Eastern Orthodox Church. The True Orthodox Church in the Soviet Union was also called the Catacomb Church; the True Orthodox in Romania, Bulgaria, Greece and Cyprus are also called Old Calendarists.

These groups refrain from concelebration of the Divine Liturgy with the mainstream Eastern Orthodox, while maintaining that they remain fully within the canonical boundaries of the Church: i.e., professing Eastern Orthodox belief, retaining legitimate apostolic succession, and existing in communities with historical continuity. However, their existence outside of communion with the other churches makes the True Orthodox automatically outside of the Eastern Orthodox Church.

The churches which follow True Orthodoxy are:
 * Old Calendarists (numerous groups)
 * Serbian True Orthodox Church
 * Russian True Orthodox Church (Lazar Zhurbenko)
 * Russian Orthodox Autonomous Church
 * True Orthodox Metropolis of Germany and Europe
 * Macedonian True Orthodox Church

Old Believers
Old Believers are divided into various churches which recognize neither each other nor the mainstream Eastern Orthodox Church.

Churches that are not recognised despite wanting to
The following churches recognize all other mainstream Eastern Orthodox churches, but are not recognised by any of them due to various disputes:
 * Abkhazian Orthodox Church
 * American Orthodox Catholic Church
 * Belarusian Autocephalous Orthodox Church
 * Latvian Orthodox Church
 * Montenegrin Orthodox Church
 * Ukrainian Orthodox Church – Kyiv Patriarchate
 * Turkish Orthodox Church

Churches that are neither recognised nor fully Eastern Orthodox
The following churches use the term "Orthodox" in their name and carry belief or the traditions of Eastern Orthodox church, but blend beliefs and traditions from other denominations outside of Eastern Orthodoxy:
 * Evangelical Orthodox Church (blends with Protestant Evangelicalism and the Charismatic movement)
 * Orthodox-Catholic Church of America (blends with Roman Catholic and Oriental Orthodox elements)
 * Nordic Catholic Church in Italy (originally called the Orthodox Church in Italy, it had ties with the UOC-KP; now associates with the Nordic Catholic Church and the Union of Scranton)
 * Lusitanian Catholic Orthodox Church (blends with Catholic elements)
 * Celtic Orthodox Church
 * Orthodox Church of the Gauls


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EDT

EDT may refer to:

Science and technology

 * 1,2-Ethanedithiol, compound commonly used for cleavage during peptide synthesis
 * EDT (Digital), text editor for PDP-11 and VAX/VMS computer systems
 * EDT (Univac), text editor for UNIVAC Series 90 and Fujitsu BS2000 computer systems
 * EDT Hub, electronic document transmission software
 * Electrodynamic tether, a spacecraft component
 * Event dispatching thread, in Java

Time zones

 * Australian Eastern Daylight Time (UTC+11)
 * Eastern Daylight Time (UTC−4), in North America

Other uses

 * Chicago Engineering Design Team, a robotics team
 * Eau de toilette
 * Electronic Disturbance Theater, an activist and artist collective
 * Evidential decision theory, a school of thought within decision theory
 * Event-driven trading, institutional investors attempt to profit from a stock mispricing that may occur during or after a corporate event.

title: EDT