Editing Enrico Fermi

{{Short description|Italian-American physicist (1901–1954)}}
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{{Infobox scientist
| honorific_suffix  = {{post-nominals|country=GBR|size=100%|ForMemRS}}
| image             = Enrico Fermi 1943-49.jpg
| caption           = Fermi in 1943
| birth_name        = <!--only necessary if birth name is different-->
| birth_date        = {{birth date|df=y|1901|9|29}}
| birth_place       = [[Rome]], [[Kingdom of Italy]]
| death_date        = {{death date and age|df=y|1954|11|28|1901|9|29}}
| death_place       = [[Chicago]], [[Illinois]], U.S.
| citizenship       = Italy (1901–1944)<br>United States (1944–1954)
| alma_mater        = [[Scuola Normale Superiore di Pisa]] ([[laurea]])
| known_for         = {{ubl|Demonstrating first self-sustaining [[nuclear chain reaction]]|[[Fermi gas]]|[[Fermi's golden rule]]|[[Fermi's interaction]]|[[Fermi paradox]]|[[Fermi problem]]|[[Fermion]]|[[Chandrasekhar–Fermi method]]|[[Thomas–Fermi model]]|[[Thomas–Fermi screening]]|[[Fermi–Dirac statistics]]}}
| spouse            = {{marriage|[[Laura Capon]]|1928}}
| children          = 2
| awards            = {{ubl|[[Matteucci Medal]] (1926)|[[Nobel Prize in Physics]] (1938)|[[Hughes Medal]] (1942)|[[Medal for Merit]] (1946)|[[Franklin Medal]] (1947)|[[List of fellows of the Royal Society elected in 1950|ForMemRS (1950)]]|[[Barnard Medal for Meritorious Service to Science]] (1950)|[[Rumford Prize]] (1953)|[[Max Planck Medal]] (1954)}}
| fields            = [[Physics]]
| work_institutions = {{ubl|Scuola Normale Superiore in Pisa|[[University of Göttingen]]|[[University of Leiden]]|[[University of Florence]]|[[Sapienza University of Rome]]|[[Columbia University]]|[[University of Chicago]]}}
| doctoral_advisor  = <!--there were no PhDs in Italy at the time-->
| academic_advisors = {{ubl|[[Max Born]]| [[Paul Ehrenfest]]|[[Luigi Puccianti]]}}
| doctoral_students = {{ubl|[[Harold Agnew]]|[[Edoardo Amaldi]]|[[Owen Chamberlain]]|[[Geoffrey Chew]]|[[Mildred Dresselhaus]]|[[Jerome Isaac Friedman|Jerome Friedman]]|[[Richard Garwin]]|[[Marvin Goldberger]]|[[Tsung-Dao Lee]]|[[Ettore Majorana]]|[[Arthur Rosenfeld]]|[[Emilio Segrè]]|[[Sam Treiman]]}}
| notable_students  = {{ubl|[[Jack Steinberger]]|[[Chen Ning Yang]]}}
| signature         = Enrico Fermi signature.svg
}}
'''Enrico Fermi''' ({{IPA|it|enˈriːko ˈfermi|lang}}; 29 September 1901 – 28 November 1954) was an Italian and [[naturalized]] American physicist, renowned for being the creator of the world's first artificial [[nuclear reactor]], the [[Chicago Pile-1]], and a member of the [[Manhattan Project]]. He has been called the "architect of the [[nuclear age]]"<ref>{{cite news|url=http://www.history.com/this-day-in-history/enrico-fermi-architect-of-the-nuclear-age-dies|title=Enrico Fermi, architect of the nuclear age, dies|date=Autumn 1954|access-date=2 November 2015|archive-url=https://web.archive.org/web/20151117014820/http://www.history.com/this-day-in-history/enrico-fermi-architect-of-the-nuclear-age-dies|archive-date=17 November 2015|url-status=dead}}</ref> and the "architect of the atomic bomb".<ref name="obit" /> He was one of very few physicists to excel in both [[theoretical physics|theoretical]] 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 element]]s. 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 mechanics|quantum theory]], and [[nuclear physics|nuclear]] and [[particle physics]].

Fermi's first major contribution involved the field of statistical mechanics. After [[Wolfgang Pauli]] formulated his [[Pauli exclusion principle|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 "[[fermion]]s". 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 interaction]]s in nature. Through experiments inducing radioactivity with the recently discovered [[neutron]], Fermi discovered that [[slow neutron]]s were more easily [[neutron capture|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 product]]s.

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 [[Nuclear reactor physics#Criticality|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 [[Project Y|Los Alamos]], he headed F Division, part of which worked on [[Edward Teller]]'s [[thermonuclear]] "[[History of the Teller–Ulam design|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]] in Chicago, and served on the General Advisory Committee, chaired by [[J. Robert Oppenheimer]], which advised the [[United States Atomic Energy Commission|Atomic Energy Commission]] on nuclear matters. After [[RDS-1|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 [[Oppenheimer security hearing|hearing]] that resulted in the denial of Oppenheimer's security clearance. 

Fermi did important work in particle physics, especially related to [[pion]]s and [[muon]]s, and he speculated that [[cosmic ray]]s arose when the material was accelerated by magnetic fields in interstellar space. Many awards, concepts, and institutions are [[list of things named after Enrico Fermi|named after Fermi]], including the [[Fermi 1]] (breeder reactor), the [[Enrico Fermi Nuclear Generating Station]], the [[Enrico Fermi Award]], the [[Enrico Fermi Institute]], the [[Fermilab|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 [[List of scientists whose names are used in chemical element names|elements named after them]].

== Early life ==
[[File:BirthHouseOfEnricoFermi01.jpg|thumb|Fermi was born in Rome at [[Via Gaeta]] 19.]]
[[File:Enrico Fermi birthplace plaque.jpg|thumb|Plaque at Fermi's birthplace]]

Enrico Fermi was born in Rome, Italy, on 29 September 1901.<ref name=":0">{{Cite web |title=Portale Antenati |url=https://antenati.cultura.gov.it/ark:/12657/an_ua19794170/5xZQ9bW/ |access-date=23 May 2023 |website=Portale Antenati |language=it-IT}}</ref> He was the third child of Alberto Fermi, a division head in the Ministry of Railways, and Ida de Gattis, an elementary school teacher.<ref name=":0" />{{sfn|Segrè|1970|pp=3–4, 8}}{{sfn|Amaldi|2001|p=23}} 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 nurse]]d, Enrico rejoined his family in Rome when he was two and a half.{{sfn|Cooper|1999|p=19}} Although he was baptized a [[Catholic Church|Catholic]] in accordance with his grandparents' wishes, his family was not particularly religious; Enrico was an [[agnostic]] throughout his adult life.<ref name="Laura Fermi">{{cite book |author1=Laura Fermi |title=Atoms in the Family: My Life with Enrico Fermi |date=24 October 2014 |publisher=University of Chicago Press |isbn=9780226149653 |page=52}}</ref> As a young boy, he shared the same interests as his brother Giulio, building [[electric motor]]s and playing with electrical and mechanical toys.{{sfn|Segrè|1970|pp=5–6}} Giulio died during an operation on a throat [[abscess]] in 1915{{sfn|Fermi|1954|pp=15–16}} and Maria died in [[TWA Flight 891|an airplane crash]] near [[Milan]] in 1959.<ref>{{cite web |url=http://www.olgiateolona26giugno1959.org/10_lives/Sac.html |title=Maria Fermi Sacchetti (1899–1959) |website=www.OlgiateOlona26giugno1959.org |access-date=6 May 2017 |language=it |url-status=dead |archive-url=https://web.archive.org/web/20170830153427/http://www.olgiateolona26giugno1959.org/10_lives/Sac.html |archive-date=30 August 2017 }}</ref>

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 {{ill|Andrea Caraffa|it}}, 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.{{sfn|Segrè|1970|p=7}}{{sfn|Bonolis|2001|p=315}} With a scientifically inclined friend, [[Enrico Persico]],{{sfn|Amaldi|2001|p=24}} Fermi pursued projects such as building [[gyroscope]]s and measuring the acceleration of [[Earth's gravity]].{{sfn|Segrè|1970|pp=11–12}}

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.{{sfn|Segrè|1970|pp=8–10}}

== ''Scuola Normale Superiore'' in Pisa ==
[[File:Enrico Fermi giovane.jpg|right|thumb|upright|Enrico Fermi as a student in Pisa]]
Fermi graduated from high school in July 1918, having skipped the third year entirely. At Amidei's urging, Fermi learned [[German language|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.{{sfn|Segrè|1970|pp=11–13}}{{sfn|Fermi|1954|pp=20–21}} 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 [[Euler–Bernoulli beam theory#Dynamic beam equation|vibrating rod]], and after interviewing Fermi the examiner declared he would become an outstanding physicist.{{sfn|Segrè|1970|pp=11–13}}<ref>{{cite web |url=http://mathematica.sns.it/autori/1173/ |title=Edizione Nazionale Mathematica Italiana – Giulio Pittarelli |publisher=Scuola Normale Superiore |language=it |access-date=6 May 2017 |archive-date=17 December 2017 |archive-url=https://web.archive.org/web/20171217014929/http://mathematica.sns.it/autori/1173/ |url-status=live }}</ref>

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.{{sfn|Segrè|1970|pp=15–18}} During this time Fermi learned [[tensor calculus]], a technique key to [[general relativity]].{{sfn|Bonolis|2001|p=320}} 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]].{{sfn|Bonolis|2001|pp=317–319}}

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.{{sfn|Segrè|1970|p=20}} 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" (''{{lang|it|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 (physics)|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" (''{{lang|it|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/c<sup>2</sup>, where U is the electrostatic energy of the system, and c is the [[speed of light]].{{sfn|Bonolis|2001|pp=317–319}}

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/c<sup>2</sup>. 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.<ref>{{cite journal |title=Über einen Widerspruch zwischen der elektrodynamischen und relativistischen Theorie der elektromagnetischen Masse |language=de |journal=Physikalische Zeitschrift |volume=23 |pages=340–344 |url=https://en.wikisource.org/?curid=1059488 |access-date=17 January 2013 |archive-date=3 February 2021 |archive-url=https://web.archive.org/web/20210203233214/https://en.wikisource.org/?curid=1059488 |url-status=live }}</ref> That year, Fermi submitted his article "On the phenomena occurring near a [[world line]]" (''{{lang|it|Sopra i fenomeni che avvengono in vicinanza di una linea oraria}}'') to the Italian journal ''{{ill|I Rendiconti dell'Accademia dei Lincei|it|Rendiconti 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]].{{sfn|Bertotti|2001|p=115}}{{sfn|Bonolis|2001|p=321}}

[[File:World line2.svg|left|thumb|A [[light cone]] is a three-dimensional surface of all possible light rays arriving at and departing from a point in [[spacetime]]. Here, it is depicted with one spatial dimension suppressed. The timeline is the vertical axis.]]
Fermi submitted his thesis, "A theorem on probability and some of its applications" (''{{lang|it|Un teorema di calcolo delle probabilità ed alcune sue applicazioni}}''), to the ''Scuola Normale Superiore'' in July 1922, and received his [[Laurea#Former status of the Laurea degree|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 to embrace 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.{{sfn|Bonolis|2001|p=321}}

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 [[Mass–energy equivalence|Einstein equation]] ({{nowrap|''E'' {{=}} ''mc''<sup>2</sup>}}) was an enormous amount of [[nuclear potential energy]] to be exploited.<ref>{{Cite web |last=Service |first=Multimedia |title=[as] radici – Le masse nella teoria della relatività (1923) |url=https://www.asimmetrie.it/le-masse-nella-teoria-della-relativita |access-date=23 July 2023 |website=Asimmetrie |language=it-it}}</ref> "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."{{sfn|Bonolis|2001|p=321}}

In 1924, Fermi was initiated into the [[Masonic Lodge]] "Adriano Lemmi" of the [[Grand Orient of Italy]].<ref>{{cite web|url=http://www.goilombardia.it/massoni-illustri/enrico-fermi|title=Enrico Fermi L'Uomo, lo Scienziato e il Massone|language=it|access-date=4 March 2015|archive-url=https://web.archive.org/web/20160320065006/http://www.goilombardia.it/massoni-illustri/enrico-fermi|archive-date=20 March 2016|url-status=dead}}</ref>

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 vapour. He also participated in seminars at the Sapienza University of Rome, giving lectures on quantum mechanics and [[solid state physics]].{{sfn|Bonolis|2001|pp=321–324}} 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!"{{sfn|Hey|Walters|2003|p=61}}

After [[Wolfgang Pauli]] announced his [[Pauli exclusion principle|exclusion principle]] in 1925, Fermi responded with a paper "On the quantization of the perfect monoatomic gas" (''{{lang|it|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 [[physical system|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]].{{sfn|Bonolis|2001|pp=329–330}} After Dirac, particles that obey the exclusion principle are today called "[[fermion]]s", while those that do not are called "[[boson]]s".{{sfn|Cooper|1999|p=31}}

== Professor in Rome ==
[[File:Ragazzi di via Panisperna cropped.jpg|thumb|upright=1.2|Fermi and his research group (the [[Via Panisperna boys]]) in the courtyard of Rome University's Physics Institute in Via Panisperna, {{circa}} 1934. From left to right: [[Oscar D'Agostino]], [[Emilio Segrè]], [[Edoardo Amaldi]], [[Franco Rasetti]] and Fermi]]

Professorships in Italy were granted by competition (''{{lang|it|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]].{{sfn|Fermi|1954|pp=37–38}} 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.{{sfn|Segrè|1970|p=45}} The committee chose Fermi ahead of Enrico Persico and [[Aldo Pontremoli]],{{sfn|Fermi|1954|p=38}} 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.{{sfn|Alison|1957|p=127}} They soon were nicknamed the "[[Via Panisperna boys]]" after the street where the Institute of Physics was located.<ref>{{cite web |url=http://www.phys.uniroma1.it/DipWeb/museo/fermi.html |title=Enrico Fermi e i ragazzi di via Panisperna |language=it |publisher=University of Rome |access-date=20 January 2013 |archive-date=20 February 2021 |archive-url=https://web.archive.org/web/20210220125803/https://www.phys.uniroma1.it/DipWeb/museo/fermi.html |url-status=live }}</ref>

Fermi married [[Laura Capon]], a science student at the university, on 19 July 1928.{{sfn|Segrè|1970|p=61}} They had two children: Nella, born in January 1931, and Giulio, born in February 1936.{{sfn|Cooper|1999|pp=38–39}} 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 [[Italian Racial Laws|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.{{sfn|Alison|1957|p=130}}<ref>{{cite web |url=http://fermi.lib.uchicago.edu/fermibiog.htm |publisher=[[University of Chicago]] |title=About Enrico Fermi |access-date=20 January 2013 |archive-date=21 December 2011 |archive-url=https://web.archive.org/web/20111221232508/http://fermi.lib.uchicago.edu/fermibiog.htm |url-status=live }}</ref><ref>{{cite news|url=http://archiviostorico.corriere.it/2001/ottobre/02/Cosi_Fermi_scopri_natura_vessatoria_co_0_0110022882.shtml |author-link=Paolo Mieli |first=Paolo |last=Mieli |title=''Così Fermi scoprì la natura vessatoria del fascismo'' |language=it |newspaper=[[Corriere della Sera]] |date=2 October 2001 |access-date=20 January 2013 |url-status=dead |archive-url=https://web.archive.org/web/20131019204537/http://archiviostorico.corriere.it/2001/ottobre/02/Cosi_Fermi_scopri_natura_vessatoria_co_0_0110022882.shtml |archive-date=19 October 2013 }}</ref><ref>{{cite web|url=http://www.archivi.beniculturali.it/DGA-free/Strumenti/Strumenti_CLXVII.pdf |author=Direzione generale per gli archivi |title=''Reale accademia d'Italia:inventario dell'archivio'' |language=it |year=2005 |publisher=Ministero per i beni culturali e ambientali |location=Rome |page=xxxix |access-date=20 January 2013 |url-status=dead |archive-url=https://web.archive.org/web/20120907065146/http://www.archivi.beniculturali.it/DGA-free/Strumenti/Strumenti_CLXVII.pdf |archive-date=7 September 2012 }}</ref><ref>{{cite web|title=A Legal Examination of Mussolini's Race Laws|url=http://primolevicenter.org/printed-matter/a-legal-examination-of-mussolinis-race-laws/|website=Printed Matter|date=5 June 2014 |publisher=Centro Primo Levi|access-date=7 August 2015|archive-date=17 August 2015|archive-url=https://web.archive.org/web/20150817005628/http://primolevicenter.org/printed-matter/a-legal-examination-of-mussolinis-race-laws/|url-status=live}}</ref>

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'' (''{{lang|it|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.{{sfn|Bonolis|2001|pp=333–335}} 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.{{sfn|Bonolis|2001|pp=333–335}}{{sfn|Amaldi|2001|p=38}} 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]],{{sfn|Fermi|1954|p=217}} who came to Rome as a Rockefeller Foundation fellow, and collaborated with Fermi on a 1932 paper "On the Interaction between Two Electrons" ({{Langx|de|Über die Wechselwirkung von Zwei Elektronen}}).<ref>{{Cite journal |last1=Bethe |first1=Hans |last2=Fermi |first2=Enrico |date=1932 |title=Über die Wechselwirkung von zwei Elektronen |url=http://link.springer.com/10.1007/BF01348919 |journal=Zeitschrift für Physik |language=de |volume=77 |issue=5–6 |pages=296–306 |doi=10.1007/BF01348919 |bibcode=1932ZPhy...77..296B |issn=1434-6001}}</ref>{{sfn|Bonolis|2001|pp=333–335}}

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]]".{{sfn|Amaldi|2001|pp=50–51}}{{sfn|Bonolis|2001|p=346}}<ref name="Beta decay">{{cite journal| last = Fermi| first = E.| title = Fermi's Theory of Beta Decay (English translation by Fred L. Wilson, 1968)| journal = [[American Journal of Physics]]| year = 1968| url = http://microboone-docdb.fnal.gov/cgi-bin/RetrieveFile?docid=953;filename=FermiBetaDecay1934.pdf;version=1| access-date = 20 January 2013| doi = 10.1119/1.1974382| volume = 36| issue = 12| page = 1150| bibcode = 1968AmJPh..36.1150W| archive-date = 12 May 2013| archive-url = https://web.archive.org/web/20130512011303/http://microboone-docdb.fnal.gov/cgi-bin/RetrieveFile?docid=953;filename=FermiBetaDecay1934.pdf;version=1| url-status = live| url-access = subscription}}</ref> 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 (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".{{sfn|Bonolis|2001|p=346}} 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 leftists) to give up the boycott of German scientific magazines, after [[Hitler]] came to power in January 1933.{{sfn|Schwartz|2021|p=154}} Thus Fermi saw the theory published in Italian and German before it was published in English.{{sfn|Alison|1957|p=127}}

In the introduction to the 1968 English translation, physicist Fred L. Wilson noted that:{{quote|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.<br />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.<ref name="Beta decay" />}}

In January 1934, [[Irène Joliot-Curie]] and [[Frédéric Joliot]] announced that they had bombarded elements with [[alpha particle]]s and induced [[radioactivity]] in them.<ref name="JoliotCurie1934a">{{cite journal|last2=Joliot|first2=Frédéric|last1=Joliot-Curie|first1=Irène|title=Un nouveau type de radioactivité|trans-title=A new type of radioactivity|journal=Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences|volume=198|issue=January–June 1934|date=15 January 1934|language=fr|pages=254–256|url=http://gallica.bnf.fr/ark:/12148/bpt6k31506/f254.image|access-date=19 October 2013|archive-date=20 February 2021|archive-url=https://web.archive.org/web/20210220125607/https://gallica.bnf.fr/ark:/12148/bpt6k31506/f254.image|url-status=live}}</ref><ref name="JoliotCurie1934b">{{cite journal|last1=Joliot|first1=Frédéric|last2=Joliot-Curie|first2=Irène|title=Artificial Production of a New Kind of Radio-Element|journal=Nature|volume=133|issue=3354|year=1934|pages=201–202|doi=10.1038/133201a0|url=http://jnm.snmjournals.org/content/5/2/xii.full.pdf|bibcode=1934Natur.133..201J|s2cid=4096977|doi-access=free|access-date=19 October 2013|archive-date=23 November 2020|archive-url=https://web.archive.org/web/20201123021722/http://jnm.snmjournals.org/content/5/2/xii.full.pdf|url-status=live}}</ref> 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.{{sfn|Amaldi|2001a|pp=152–153}} 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.{{sfn|Bonolis|2001|pp=347–351}}{{sfn|Amaldi|2001a|pp=153–156}}

[[File:RasettiFermiSegre.JPG|thumb|upright=1.3|Enrico Fermi between [[Franco Rasetti]] (left) and [[Emilio Segrè]] in [[academic dress]]]]
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 m[[Curie (unit)|Ci]] of radon gas, supplied by {{ill|Giulio Cesare Trabacchi|it}}.{{sfn|Segrè|1970|p=73}}<ref name="De Gregorio2005">{{cite journal|last1=De Gregorio|first1=Alberto G.|title=Neutron physics in the early 1930s|journal=Historical Studies in the Physical and Biological Sciences|volume=35 |issue=2|year=2005 |pages=293–340 |doi=10.1525/hsps.2005.35.2.293 |arxiv=physics/0510044|bibcode=2005physics..10044D|s2cid=119489980}}</ref> 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 ray]]s, 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.<ref>{{cite journal |journal=Physics in Perspective |title=Enrico Fermi's Discovery of Neutron-Induced Artificial Radioactivity: The Influence of His Theory of Beta Decay|last1=Guerra |first1=Francesco |last2=Robotti |first2=Nadia|author2-link=Nadia Robotti |date=December 2009 |volume=11 |issue=4 |doi=10.1007/s00016-008-0415-1 |pages=379–404|bibcode = 2009PhP....11..379G |s2cid=120707438}}</ref> Fermi rapidly reported the discovery of neutron-induced radioactivity in the Italian journal ''La Ricerca Scientifica'' on 25 March 1934.<ref name="De Gregorio2005" /><ref>{{cite journal|first=Enrico|last=Fermi|title=Radioattività indotta da bombardamento di neutroni|journal=La Ricerca Scientifica|volume=1|issue=5|date=25 March 1934|page=283|url=http://www.phys.uniroma1.it/DipWeb/museo/collezione%20Fermi/documento2.htm|language=it|access-date=20 October 2013|archive-date=24 February 2021|archive-url=https://web.archive.org/web/20210224071249/https://www.phys.uniroma1.it/DipWeb/museo/collezione%20Fermi/documento2.htm|url-status=dead}}</ref><ref name="FermiAmaldi1934">{{Cite journal | last1 = Fermi | first1 = E. | last2 = Amaldi | first2 = E. | last3 = d'Agostino | first3 = O. | last4 = Rasetti | first4 = F. | last5 = Segre | first5 = E. | title = Artificial Radioactivity Produced by Neutron Bombardment | doi = 10.1098/rspa.1934.0168 | journal = Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences | volume = 146 | issue = 857 | page = 483 | year = 1934 |bibcode = 1934RSPSA.146..483F | doi-access = free }}</ref>

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]].{{sfn|Bonolis|2001|pp=347–349}}{{sfn|Amaldi|2001a|pp=153–156}} 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.{{sfn|Amaldi|2001a|pp=161–162}}{{sfn|Bonolis|2001|pp=347–349}}

[[File:Beta-minus Decay.svg|thumb|left|[[Beta decay]]. A [[neutron]] decays into a [[proton]], and an [[electron]] is emitted. In order for the total energy in the system to remain the same, Pauli and Fermi postulated that a [[neutrino]] (<math>\bar{\nu}_e</math>) was also emitted.]]
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.{{sfn|Bonolis|2001|pp=347–352}}{{sfn|Amaldi|2001a|pp=153–156}} 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.<ref>{{cite web |url=http://energyfromthorium.com/2007/02/13/a-few-good-moderators-the-numbers/ |title=A Few Good Moderators: The Numbers |publisher=The Energy From Thorium Foundation |access-date=24 September 2013 |date=13 February 2007 |archive-date=24 February 2021 |archive-url=https://web.archive.org/web/20210224071432/https://energyfromthorium.com/2007/02/13/a-few-good-moderators-the-numbers/ |url-status=live }}</ref> Fermi realised that this induced more radioactivity because [[slow neutron]]s were more easily [[neutron capture|captured]] than fast ones. He developed a [[diffusion equation]] to describe this, which became known as the [[Fermi age equation]].{{sfn|Bonolis|2001|pp=347–352}}{{sfn|Amaldi|2001a|pp=153–156}}

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 reaction]]s brought about by slow neutrons".{{sfn|Cooper|1999|p=51}} 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.{{sfn|Alison|1957|p=130}}{{sfn|Sullivan|2016|p=19}}

== Manhattan Project ==
{{Main|Manhattan Project}}
[[File:Stagg Field reactor.jpg|thumb|upright=1.2|Illustration of [[Chicago Pile-1]], the first nuclear reactor to achieve a self-sustaining chain reaction. Designed by Fermi, it consisted of uranium and uranium oxide in a cubic lattice embedded in graphite.]]
[[File:Enrico Fermi Los Alamos.png|thumb|Fermi's ID photo from [[Los Alamos National Laboratory|Los Alamos]]]]
[[File:Atomic physicists Ernest O. Lawrence, Enrico Fermi, and Isidor Rabi - NARA - 558595.jpg|thumb|upright=1.1|[[Ernest O. Lawrence]], Fermi, and [[Isidor Isaac Rabi]] |alt=Three men talking. The one on the left is wearing a tie and leans against a wall. He stands with his head and shoulders visibly above the other two's heads. The one in the center is smiling, and wearing an open-necked shirt. The one on the right wears a shirt and lab coat. All three have photo ID passes.]]
[[File:Fermiac.jpg|thumb|right|upright=0.85|The [[FERMIAC]], an [[analog computer]] invented by Fermi to study neutron transport]]

Fermi arrived in New York City on 2 January 1939.{{sfn|Cooper|1999|p=52}} He was immediately offered positions at five universities, and accepted one at [[Columbia University]],{{sfn|Persico|2001|p=40}} where he had already given summer lectures in 1936.{{sfn|Bonolis|2001|p=352}} 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,<ref>{{cite journal
 |last1=Hahn |first1=O.
 | author-link = Otto Hahn
 |last2=Strassmann |first2=F.
 | author-link2 = Fritz Strassmann
 |year=1939
 |language=de
 |title=Über den Nachweis und das Verhalten der bei der Bestrahlung des Urans mittels Neutronen entstehenden Erdalkalimetalle
 |trans-title=On the detection and characteristics of the alkaline earth metals formed by irradiation of uranium with neutrons
 |journal=[[Naturwissenschaften]]
 |volume=27 |issue=1 |pages=11–15
 |doi=10.1007/BF01488241
 |bibcode = 1939NW.....27...11H|s2cid=5920336
 }}</ref> which [[Lise Meitner]] and her nephew [[Otto Frisch]] correctly interpreted as the result of [[nuclear fission]]. Frisch confirmed this experimentally on 13 January 1939.<ref name="Frisch1939">{{cite journal|last1=Frisch |first1=O. R. |title=Physical Evidence for the Division of Heavy Nuclei under Neutron Bombardment |journal=Nature |volume=143 |issue=3616 |year=1939 |pages=276 |doi=10.1038/143276a0 |bibcode=1939Natur.143..276F |s2cid=4076376 |doi-access=free }}</ref><ref>{{cite journal
 |last1=Meitner
 |first1=L.
 |author-link=Lise Meitner
 |last2=Frisch
 |first2=O.R.
 |author-link2=Otto Robert Frisch
 |year=1939
 |title=Disintegration of Uranium by Neutrons: a New Type of Nuclear Reaction
 |url=http://www.nature.com/physics/looking-back/meitner/index.html
 |journal=[[Nature (journal)|Nature]]
 |volume=143
 |issue=3615
 |pages=239–240
 |doi=10.1038/143239a0
 |bibcode=1939Natur.143..239M
 |s2cid=4113262
 |access-date=17 March 2008
|archive-date=28 April 2019
|archive-url=https://web.archive.org/web/20190428141914/http://www.nature.com/physics/looking-back/meitner/index.html
 |url-status=live
 |url-access=subscription
 }}</ref> 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:{{sfn|Rhodes|1986|p=267}}
{{Blockquote|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]].{{sfn|Segrè|1970|pp=222–223}}}}

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.{{sfn|Amaldi|2001a|pp=161–162}} 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.{{sfn|Rhodes|1986|p=267}}<ref name="Nobel" />

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]].<ref>{{cite journal|last1=Anderson|first1=H.L.|last2=Booth|first2=E. |last3=Dunning|first3=J.|last4=Fermi |first4=E.|last5=Glasoe |first5=G. |last6=Slack|first6=F.|title=The Fission of Uranium|journal=[[Physical Review]]|volume=55|issue=5|date=16 February 1939|pages=511–512 |doi=10.1103/PhysRev.55.511.2|bibcode = 1939PhRv...55..511A }}</ref> 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.{{sfn|Rhodes|1986|pp=269–270}}

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.<ref name="Von HalbanJoliot1939">{{cite journal|last1=Von Halban |first1=H.|last2=Joliot |first2=F.|last3=Kowarski |first3=L. |title=Number of Neutrons Liberated in the Nuclear Fission of Uranium|journal=Nature|volume=143|issue=3625|date=22 April 1939|pages=680 |doi=10.1038/143680a0|bibcode = 1939Natur.143..680V |s2cid=4089039|doi-access=free}}</ref> Fermi and Anderson did so too a few weeks later.<ref name="AndersonFermi1939">{{cite journal|last1=Anderson|first1=H.|last2=Fermi|first2=E.|last3=Hanstein|first3=H.|title=Production of Neutrons in Uranium Bombarded by Neutrons|journal=Physical Review|volume=55|issue=8|date=16 March 1939|pages=797–798|doi=10.1103/PhysRev.55.797.2|bibcode = 1939PhRv...55..797A }}</ref><ref>{{cite journal|last=Anderson|first=H.L.|title=Early Days of Chain Reaction|url=https://books.google.com/books?id=IgwAAAAAMBAJ&pg=PA10|date=April 1973|journal=Bulletin of the Atomic Scientists|volume=29|issue=4|pages=8–12|bibcode=1973BuAtS..29d...8A|doi=10.1080/00963402.1973.11455466|access-date=20 November 2015|archive-date=8 June 2020|archive-url=https://web.archive.org/web/20200608222703/https://books.google.com/books?id=IgwAAAAAMBAJ&pg=PA10|url-status=live|url-access=subscription}}</ref> [[Leó Szilárd]] obtained {{convert|200|kg}} of [[uranium oxide]] from Canadian [[radium]] producer [[Eldorado Mining and Refining Limited|Eldorado Gold Mines Limited]], allowing Fermi and Anderson to conduct experiments with fission on a much larger scale.<ref name=Anderson1939 /> 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.{{sfn|Salvetti|2001|pp=186–188}} Szilárd, Anderson, and Fermi published a paper on "Neutron Production in Uranium".<ref name=Anderson1939>{{cite journal|last1=Anderson|first1=H.|last2=Fermi|first2=E.|last3=Szilárd|first3=L.|title=Neutron Production and Absorption in Uranium|journal=[[Physical Review]]|volume=56|issue=3|date=1 August 1939|pages=284–286|doi=10.1103/PhysRev.56.284|url=http://docs.fdrlibrary.marist.edu/psf/box5/a64g01.html|bibcode=1939PhRv...56..284A|access-date=19 October 2013|archive-date=25 February 2021|archive-url=https://web.archive.org/web/20210225023106/http://docs.fdrlibrary.marist.edu/psf/box5/a64g01.html|url-status=live|url-access=subscription}}</ref> But their work habits and personalities were different, and Fermi had trouble working with Szilárd.{{sfn|Bonolis|2001|pp=356–357}}

Fermi was among the first to warn military leaders about the potential impact of nuclear energy, giving a lecture on the subject at the [[United States Department of the Navy|Navy Department]] on 18&nbsp;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.{{sfn|Salvetti|2001|p=185}} Later that year, Szilárd, [[Eugene Wigner]], and [[Edward Teller]] sent [[Einstein–Szilárd letter|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.{{sfn|Salvetti|2001|pp=188–189}}

The Advisory Committee on Uranium provided money for Fermi to buy graphite,{{sfn|Rhodes|1986|pp=314–317}} and he built a pile of graphite bricks on the seventh floor of the Pupin Hall laboratory.{{sfn|Salvetti|2001|p=190}} 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.{{sfn|Salvetti|2001|p=195}}

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.{{sfn|Salvetti|2001|pp=194–196}} 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.{{sfn|Rhodes|1986|pp=399–400}}

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 {{convert|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 (sport)|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 [[Nuclear reactor physics#Criticality|critical]] on 2 December.{{sfn|Salvetti|2001|pp=198–202}} 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.<ref>{{cite journal | last=Fermi |first=E. | title=The Development of the First Chain Reaction Pile | journal=[[Proc. Am. Philos. Soc.]] | year=1946 | volume=90 |issue=1 | pages=20–24 | jstor=3301034}}</ref>

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.{{sfn|Salvetti|2001|pp=198–202}} 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]].{{quote|
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."{{sfn|Compton|1956|p=144}} }}

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.{{sfn|Bonolis|2001|p=366}} 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.{{sfn|Hewlett|Anderson|1962|p=207}}

When the air-cooled [[X-10 Graphite Reactor]] at [[Oak Ridge National Laboratory|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.{{sfn|Hewlett|Anderson|1962|pp=208–211}} 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.{{sfn|Jones|1985|p=205}} Fermi became an American citizen in July 1944, the earliest date the law allowed.{{sfn|Segrè|1970|p=104}}

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 rod]]s 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 poison]]ing from [[xenon-135]] or Xe-135, a fission product with a half-life of 9.1 to 9.4 hours. Fermi and [[John Archibald Wheeler|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]].<ref>{{Cite web|last=Dicke|first=William|title=Chien-Shiung Wu, 84, Top Experimental Physicist|url=http://cwp.library.ucla.edu/articles/wuobit.html|date=18 February 1997|access-date=12 March 2021|archive-date=14 July 2010|archive-url=https://web.archive.org/web/20100714030031/http://cwp.library.ucla.edu/articles/wuobit.html|url-status=live}}</ref> 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.<ref>{{Cite web|last=Benczer-Koller|first=Noemie|title=Chien-shiungwu 1912–1997|url=http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/wu-chien-shiung.pdf|date=January 2009|access-date=12 March 2021|archive-date=26 March 2015|archive-url=https://web.archive.org/web/20150326081624/http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/wu-chien-shiung.pdf|url-status=live}}</ref><ref>{{Cite book|last=Lykknes|first=Annette|title=Women In Their Element: Selected Women's Contributions To The Periodic System|url=https://books.google.com/books?id=2ZmxDwAAQBAJ&q=chien+shiung+wu+work+showed+xe+135+neutron+absorption+b+reactor&pg=PA387|year=2019|publisher=World Scientific |isbn=9789811206306|access-date=3 May 2021|archive-date=30 May 2021|archive-url=https://web.archive.org/web/20210530222342/https://books.google.com/books?id=2ZmxDwAAQBAJ&q=chien+shiung+wu+work+showed+xe+135+neutron+absorption+b+reactor&pg=PA387|url-status=live}}</ref><ref name="chiang">{{cite web
 |last=Chiang
 |first=T.-C.
 |date=27 November 2012
|title=Inside Story: C S Wu&nbsp;– First Lady of physics research
 |url=http://cerncourier.com/cws/article/cern/51556
 |work=[[CERN Courier]]
 |access-date=5 April 2014
|archive-date=12 June 2018
|archive-url=https://web.archive.org/web/20180612144506/http://cerncourier.com/cws/article/cern/51556
 |url-status=live
 }}</ref> 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.{{sfn|Hewlett|Anderson|1962|pp=304–307}}{{sfn|Jones|1985|pp=220–223}}
[[File:ChicagoPileTeam.png|thumb|upright=1.2|Some of the [[University of Chicago]] team that worked on the production of the world's first human-caused self-sustaining nuclear reaction, including Enrico Fermi in the front row and [[Leó Szilárd]] in the second.]]
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 sceptical 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.{{sfn|Rhodes|1986||pp=510–511}}

In mid-1944, Oppenheimer persuaded Fermi to join his [[Project Y]] at [[Los Alamos, New Mexico]].{{sfn|Bonolis|2001|pp=368–369}} 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 [[History of the Teller–Ulam design|"Super" (thermonuclear) bomb]]; F-2 Water Boiler under L. D. P. King, which looked after the "water boiler" [[Aqueous homogeneous reactor|aqueous homogeneous]] [[research reactor]]; F-3 Super Experimentation under [[Egon Bretscher]]; and F-4 Fission Studies under Anderson.{{sfn|Hawkins|1961|p=213}} 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.{{sfn|Rhodes|1986|pp=674–677}}

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.{{sfn|Jones|1985|pp=531–532}} 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]].{{sfn|Fermi|1954|pp=244–245}}

== Postwar work ==
Fermi became the Charles H. Swift Distinguished Professor of Physics at the University of Chicago on 1 July 1945,{{sfn|Segrè|1970|p=157}} although he did not depart the Los Alamos Laboratory with his family until 31 December 1945.{{sfn|Segrè|1970|p=167}} He was elected a member of the [[US National Academy of Sciences]] in 1945.<ref name="NAS">{{cite web| url = http://www.nasonline.org/member-directory/deceased-members/20001146.html| title="Enrico Fermi" on NASOnline.org| access-date = 18 February 2016| archive-date = 25 February 2016| archive-url = https://web.archive.org/web/20160225055710/http://www.nasonline.org/member-directory/deceased-members/20001146.html| url-status = live}}</ref> The Metallurgical Laboratory became the [[Argonne National Laboratory]] on 1 July 1946, the first of the [[United States Department of Energy National Laboratories|national laboratories]] established by the Manhattan Project.{{sfn|Holl|Hewlett|Harris|1997|pp=xix–xx}} 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]].{{sfn|Segrè|1970|p=171}} 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.{{sfn|Segrè|1970|p=172}}

The Manhattan Project was replaced by the [[United States Atomic Energy Commission|Atomic Energy Commission]] (AEC) on 1 January 1947.{{sfn|Hewlett|Anderson|1962|p=643}} Fermi served on the AEC General Advisory Committee, an influential scientific committee chaired by Robert Oppenheimer.{{sfn|Hewlett|Anderson|1962|p=648}} He also liked to spend a few weeks each year at the Los Alamos National Laboratory,{{sfn|Segrè|1970|p=175}} where he collaborated with [[Nicholas Metropolis]],{{sfn|Segrè|1970|p=179}} and with [[John von Neumann]] on [[Rayleigh–Taylor instability]], the science of what occurs at the border between two fluids of different densities.{{sfn|Bonolis|2001|p=381}}

[[File:Laura and Enrico Fermi 1954.jpg|thumb|left|[[Laura Fermi|Laura]] and Enrico Fermi at the [[Institute for Nuclear Studies]], Los Alamos, 1954]]
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.{{sfn|Hewlett|Duncan|1969|pp=380–385}} 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.{{sfn|Hewlett|Duncan|1969|pp=527–530}} 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.{{sfn|Cooper|1999|pp=102–103}}

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 Isaac Friedman|Jerome Friedman]], [[Marvin Goldberger]], [[Tsung-Dao Lee]], [[Arthur Rosenfeld]] and [[Sam Treiman]].<ref name="mathgene">{{MathGenealogy|id=14167}}</ref><ref name="Nobel">{{Nobelprize}} including the Nobel Lecture, 12 December 1938 ''Artificial Radioactivity Produced by Neutron Bombardment''</ref> [[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.<ref>{{cite web |url=https://www.nobelprize.org/nobel_prizes/physics/laureates/1988/steinberger-bio.html |access-date=15 August 2013 |title=Jack Steinberger&nbsp;– Biographical |publisher=Nobel Foundation |archive-date=4 October 2013 |archive-url=https://web.archive.org/web/20131004230100/http://www.nobelprize.org/nobel_prizes/physics/laureates/1988/steinberger-bio.html |url-status=live }}</ref><ref name="Cornish">{{cite news |last1=Cornish |first1=Audie |title='Queen Of Carbon' Among Medal Of Freedom Honorees |url=https://www.npr.org/2014/11/24/366379355/queen-of-carbon-among-medal-of-freedom-honorees |access-date=30 September 2018 |work=All Things Considered |publisher=NPR |date=24 November 2014 |archive-date=30 September 2018 |archive-url=https://web.archive.org/web/20180930115640/https://www.npr.org/2014/11/24/366379355/queen-of-carbon-among-medal-of-freedom-honorees |url-status=live }}</ref> Fermi conducted important research in particle physics, especially related to [[pion]]s and [[muon]]s. He made the first predictions of pion-[[nucleon]] resonance,{{sfn|Segrè|1970|p=179}} relying on [[statistical methods]], since he reasoned that exact answers were not required when the theory was wrong anyway.{{sfn|Bonolis|2001|pp=374–379}} In a paper coauthored with [[Chen Ning Yang]], he speculated that pions might actually be composite particles.<ref>{{Cite journal | last1 = Fermi | first1 = E. | last2 = Yang | first2 = C. | doi = 10.1103/PhysRev.76.1739 | title = Are Mesons Elementary Particles? | journal = Physical Review | volume = 76 | issue = 12 | page = 1739 | year = 1949 |bibcode = 1949PhRv...76.1739F }}</ref> 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.{{sfn|Jacob|Maiani|2001|pp=254–258}}

Fermi wrote a paper "On the Origin of [[cosmic radiation|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.{{sfn|Bonolis|2001|pp=374–379}} Fermi examined the issues surrounding magnetic fields in the arms of a [[spiral galaxy]].{{sfn|Bonolis|2001|p=386}} 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.{{sfn|Jones|1985a|pp=1–3}}

[[File:Enrico fermi tomb2.jpg|right|thumb|upright|Fermi's grave at [[Oak Woods Cemetery]], Chicago, near the university]]
Toward the end of his life, Fermi questioned his faith in society at large to make wise choices about nuclear technology. He said:

{{quote|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.{{sfn|Fermi|2004|p=142}}
}}

== Death ==
Fermi underwent what was called an "[[Exploratory surgery|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.<ref name="obit">{{cite news|last=|first=|date=29 November 1954|title=Enrico Fermi Dead at 53; Architect of Atomic Bomb|newspaper=[[The New York Times]]|url=https://www.nytimes.com/learning/general/onthisday/bday/0929.html|url-status=dead|access-date=21 January 2013|archive-url=https://web.archive.org/web/20190314034514/https://archive.nytimes.com/www.nytimes.com/learning/general/onthisday/bday/0929.html|archive-date=14 March 2019}}</ref> 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.<ref> {{cite web|accessdate=16 December 2022 |url= https://science.osti.gov/fermi/The-Life-of-Enrico-Fermi |title= The Life of Enrico Fermi|date= 12 December 2022}}</ref>

A memorial service was held at the [[Rockefeller Chapel|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."<ref>{{Cite journal |title=Enrico Fermi 1901–1954 |journal=Physics Today |date=January 1955 |issue=1 |pages=9–13 |doi=10.1063/1.3061909 |last1=Allison |first1=S. K. |last2=Segrè |first2=Emilio |last3=Anderson |first3=Herbert L. |volume=8 |bibcode=1955PhT.....8a...9A }}</ref> His body was interred at [[Oak Woods Cemetery]] where a private graveside service for the immediate family took place presided by a Lutheran chaplain.{{sfn|Hucke|Bielski|1999|pp=147, 150}}

== Impact and legacy ==
=== 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.{{sfn|Alison|1957|pp=135–136}} Fermi was elected member of the [[American Philosophical Society]] in 1939 and a [[List of Fellows of the Royal Society elected in 1950|Foreign Member of the Royal Society (FRS) in 1950]].<ref>{{Cite web |title=APS Member History |url=https://search.amphilsoc.org/memhist/search?creator=Enrico+Fermi&title=&subject=&subdiv=&mem=&year=&year-max=&dead=&keyword=&smode=advanced |access-date=8 May 2023 |website=search.amphilsoc.org}}</ref><ref name="frs" /> 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.<ref>{{cite web |url=http://gotterdammerung.org/photo/travel/italy/florence/churches/basilica-di-santa-croce/060907-175358%20The%20Tomb%20of%20Enrico%20Fermi%20at%20Santa%20Croce.html |title=Enrico Fermi in Santa Croce, Florence |publisher=gotterdammerung.org |access-date=10 May 2015 }}</ref> In 1999, ''[[Time (magazine)|Time]]'' named Fermi on its list of the top 100 persons of the twentieth century.<ref>{{cite news |newspaper=[[Time (magazine)|Time]] |url=http://www.time.com/time/magazine/article/0,9171,26473,00.html |archive-url=https://web.archive.org/web/20010211124411/http://www.time.com/time/magazine/article/0,9171,26473,00.html |url-status=dead |archive-date=11 February 2001 |title=''Time'' 100 Persons of the Century |date=6 June 1999 |access-date=2 March 2013 }}</ref> 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 [[Ernest Rutherford|Rutherford]]'s atomic nucleus, and then developing [[Bohr model|Bohr's theory]] of the hydrogen atom. If this sounds like hyperbole, anything about Fermi is likely to sound like hyperbole".{{sfn|Snow|1981|p=79}}

Fermi was known as an inspiring teacher and was noted for his attention to detail, simplicity, and careful preparation of his lectures.{{sfn|Ricci|2001|pp=297–302}} Later, his lecture notes were transcribed into books.{{sfn|Ricci|2001|p=286}} His papers and notebooks are today at the University of Chicago.<ref>{{cite web |url=http://fermi.lib.uchicago.edu/fermicollection.htm |title=Enrico Fermi Collection |publisher=[[University of Chicago]] |access-date=22 January 2013 |archive-date=18 March 2021 |archive-url=https://web.archive.org/web/20210318040831/http://fermi.lib.uchicago.edu/fermicollection.htm |url-status=live }}</ref> [[Victor Weisskopf]] noted how Fermi "always managed to find the simplest and most direct approach, with the minimum of complication and sophistication."{{sfn|Salvini|2001|p=5}} 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.{{sfn|Von Baeyer|1993|pp=3–8}}

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.{{sfn|Fermi|1954|p=242}} 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 [[quark]]s and [[lepton]]s.{{sfn|Salvini|2001|p=17}}

{{Quote|text=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.|author=[[Egon Bretscher]]<ref name="frs">{{Cite journal | last1 = Bretscher | first1 = E. | last2 = Cockcroft | first2 = J.D.| author-link2 = John Cockcroft | doi = 10.1098/rsbm.1955.0006 | title = Enrico Fermi. 1901–1954 | journal = [[Biographical Memoirs of Fellows of the Royal Society]] | volume = 1 | pages = 69–78 | year = 1955 | jstor = 769243| doi-access = free }}</ref>}}

=== Things named after Fermi ===
[[File:Viaenricofermi.jpg|right|thumb|The sign at Enrico Fermi Street in Rome]]
[[File:Memorial plaque in honour of Enrico Fermi in the Basilica Santa Croce, Florence. Italy.jpg|thumb|Memorial plaque in the Basilica [[Santa Croce, Florence]]. Italy]]
{{Main|List of things named after Enrico Fermi}}
Many things bear Fermi's name. These include the [[Fermilab]] particle accelerator and physics lab in [[Batavia, Illinois]], which was renamed in his honour in 1974,<ref>{{cite web |url=http://www.fnal.gov/pub/about/whatis/history.html |title=About Fermilab – History |publisher=[[Fermilab]] |access-date=21 January 2013 |archive-date=14 September 2012 |archive-url=https://web.archive.org/web/20120914170901/http://www.fnal.gov/pub/about/whatis/history.html |url-status=live }}</ref> and the [[Fermi Gamma-ray Space Telescope]], which was named after him in 2008, in recognition of his work on cosmic rays.<ref>{{cite web |url=https://science.nasa.gov/science-news/science-at-nasa/2008/26aug_firstlight/ |publisher=[[National Aeronautics and Space Administration]] |title=First Light for the Fermi Space Telescope |access-date=21 January 2013 |archive-date=1 October 2012 |archive-url=https://web.archive.org/web/20121001155336/http://science.nasa.gov/science-news/science-at-nasa/2008/26aug_firstlight/ |url-status=live }}</ref> 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 (Italy)|Enrico Fermi Nuclear Power Plant]] at [[Trino Vercellese]] in Italy,<ref>{{cite web |url=http://world-nuclear.org/info/inf101.html |title=Nuclear Power in Italy |publisher=World Nuclear Association |access-date=21 January 2013 |archive-date=11 June 2020 |archive-url=https://web.archive.org/web/20200611084218/https://world-nuclear.org/information-library/country-profiles/countries-g-n/italy.aspx |url-status=live }}</ref> and the [[RA-1 Enrico Fermi]] research reactor in [[Argentina]].<ref>{{cite web|url=http://www.cnea.edu.ar/xxi/ambiental/agua-pura/publicaciones/FolletoColor.pdf |title=Report of the National Atomic Energy Commission of Argentina (CNEA) |publisher=[[CNEA]] |date=November 2004 |access-date=21 January 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130514012403/http://www.cnea.edu.ar/xxi/ambiental/agua-pura/publicaciones/FolletoColor.pdf |archive-date=14 May 2013 }}</ref> 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.{{sfn|Seaborg|1978|p=2}}{{sfn|Hoff|1978|pp=39–48}} This makes him one of 16 scientists who have [[List of scientists whose names are used in chemical element names|elements named after them]].<ref>{{cite web|author1=Kevin A. Boudreaux|title=Derivations of the Names and Symbols of the Elements|url=http://www.angelo.edu/faculty/kboudrea/periodic/hist_names.htm|publisher=Angelo State University|access-date=11 February 2017|archive-date=3 December 2017|archive-url=https://web.archive.org/web/20171203052317/http://www.angelo.edu/faculty/kboudrea/periodic/hist_names.htm|url-status=live}}</ref>

Starting in 1956 the [[United States Atomic Energy Commission]], and from 1977, the [[U.S. Energy Department]], has named its highest honor, the [[Fermi Award]], for him.<ref>{{cite web |title=Nomination & Selection Guidelines |url=https://science.osti.gov/fermi/Nomination-and-Selection-Guidelines |website=U.S. Department of Energy |date=11 March 2025 |access-date=25 March 2025}}</ref> Recipients of the award have included Otto Hahn, Robert Oppenheimer, Edward Teller and Hans Bethe.

== Publications ==
* {{cite book |title=Introduzione alla Fisica Atomica |publisher=N. [[Zanichelli]] |location=Bologna |year=1928 |language=it |oclc=9653646 }}
* {{cite book |title=Fisica per i Licei |publisher=N. Zanichelli |location=Bologna |year=1929 |language=it |oclc=9653646 }}
* {{cite book |title=Molecole e cristalli |publisher=N. Zanichelli |location=Bologna |year=1934|language=it |oclc=19918218 }}
* {{cite book |title=Thermodynamics |publisher=Prentice Hall |location=New York |year=1937 |oclc=2379038}}
* {{cite book |title=Fisica per Istituti Tecnici |publisher=N. Zanichelli |location=Bologna |year=1938 |language=it }}
* {{cite book |title=Fisica per Licei Scientifici |publisher=N. Zanichelli |location=Bologna |year=1938|language=it }} (with [[Edoardo Amaldi]])
* {{cite book |title=Elementary particles |url=https://archive.org/details/elementarypartic00ferm |url-access=registration |publisher=Yale University Press |location=New Haven |year=1951 |oclc=362513 }}
* {{cite book | title=Notes on Quantum Mechanics | location=Chicago | publisher=The University of Chicago Press| year= 1961| oclc=1448078 }}
For a full list of his papers, see pages 75–78 in ref.<ref name="frs" />

== Patents ==
* {{cite patent|country-code=US |patent-number=2206634 |title=Process for the Production of Radioactive Substances |fdate=October 1935 |issue-date=July 1940|status=Patent}}
* {{cite patent|country-code=US |patent-number=2836554 |title=Air Cooled Neutronic Reactor |fdate=May 1945 |issue-date=April 1950|status=Patent}}
* {{cite patent|country-code=US |patent-number=2524379 |title=Neutron Velocity Selector |fdate=September 1945 |issue-date=October 1950|status=Patent}}
* {{cite patent|country-code=US |patent-number=2852461 |title=Neutronic Reactor |fdate=October 1945 |issue-date=September 1953|status=Patent}}
* {{cite patent|country-code=US |patent-number=2708656 |title=Neutronic Reactor |fdate=December 1944 |issue-date=May 1955|status=Patent}}
* {{cite patent|country-code=US |patent-number=2768134 |title=Testing Material in a Neutronic Reactor |fdate=August 1945 |issue-date=October 1956|status=Patent}}
* {{cite patent|country-code=US |patent-number=2780595 |title=Test Exponential Pile |fdate=May 1944 |issue-date=February 1957|status=Patent}}
* {{cite patent|country-code=US |patent-number=2798847 |title=Method of Operating a Neutronic Reactor |fdate=December 1944 |issue-date=July 1957|status=Patent}}
* {{cite patent|country-code=US |patent-number=2807581 |title=Neutronic Reactor |fdate=October 1945 |issue-date=September 1957|status=Patent}}
* {{cite patent|country-code=US |patent-number=2807727 |title=Neutronic Reactor Shield |fdate=January 1946 |issue-date=September 1957|status=Patent}}
* {{cite patent|country-code=US |patent-number=2813070 |title=Method of Sustaining a Neutronic Chain Reacting System |fdate=November 1945 |issue-date=November 1957|status=Patent}}
* {{cite patent|country-code=US |patent-number=2837477 |title=Chain Reacting System |fdate=February 1945 |issue-date=June 1958|status=Patent}}
* {{cite patent|country-code=US |patent-number=2931762 |title=Neutronic Reactor |fdate=May 1945 |issue-date=April 1960|status=Patent}}
* {{cite patent|country-code=US |patent-number=2969307 |title=Method of Testing Thermal Neutron Fissionable Material for Purity |fdate=1945 |issue-date=January 1961|status=Patent}}

== References ==
{{Reflist}}

== Sources ==
{{Refbegin|30em}}
* {{cite journal |last=Alison |first=Samuel King |author-link=Samuel King Allison |year=1957 |title=Enrico Fermi, 1901–1954 |url=http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/fermi-enrico.pdf |journal=Biographical Memoirs of the National Academy of Sciences |volume=30 |pages=125–155 |oclc=11772127 |access-date=4 December 2021 |archive-date=16 December 2021 |archive-url=https://web.archive.org/web/20211216123429/http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/fermi-enrico.pdf |url-status=live }}
* {{cite book |last=Amaldi |first=Edoardo |author-link=Edoardo Amaldi |contribution=Commemoration of the Academy Fellow Enrico Fermi |pages=[https://archive.org/details/enricofermihiswo0000unse/page/23 23–35] |editor-last=Bernardini |editor-first=C. |editor2-first=Luisa |editor2-last=Bonolis |year=2001 |title=Enrico Fermi: His Work and Legacy |location=Bologna |publisher=Società Italiana di Fisica: Springer |isbn=978-88-7438-015-2 |oclc=56686431 |url=https://archive.org/details/enricofermihiswo0000unse/page/23 }}
* {{cite book |last=Amaldi |first=Ugo |contribution=Nuclear Physics from the Nineteen Thirties to the Present Day |title=Enrico Fermi: His Work and Legacy |pages=[https://archive.org/details/enricofermihiswo0000unse/page/151 151–176] |editor-last=Bernardini |editor-first=C. |editor2-first=Luisa |editor2-last=Bonolis |year=2001 |location=Bologna |publisher=Società Italiana di Fisica: Springer |isbn=978-88-7438-015-2 |oclc=56686431 |ref=CITEREFAmaldi2001a |url=https://archive.org/details/enricofermihiswo0000unse/page/151 }}
* {{cite book |last=Bertotti |first=Bruno |contribution=Fermi's Coordinates and the Principle of Equivalence |pages=[https://archive.org/details/enricofermihiswo0000unse/page/115 115–125] |editor-last=Bernardini |editor-first=C. |editor2-first=Luisa |editor2-last=Bonolis |year=2001 |title=Enrico Fermi: His Work and Legacy |location=Bologna |publisher=Società Italiana di Fisica: Springer |isbn=978-88-7438-015-2 |oclc=56686431 |url=https://archive.org/details/enricofermihiswo0000unse/page/115 }}
* {{cite book |last=Bonolis |first=Luisa |contribution=Enrico Fermi's Scientific Work |pages=[https://archive.org/details/enricofermihiswo0000unse/page/314 314–394] |editor-last=Bernardini |editor-first=C. |editor2-first=Luisa |editor2-last=Bonolis |year=2001 |title=Enrico Fermi: His Work and Legacy |location=Bologna |publisher=Società Italiana di Fisica: Springer |isbn=978-88-7438-015-2 |oclc=56686431 |url=https://archive.org/details/enricofermihiswo0000unse/page/314 }}
* {{cite book |last=Compton |first=Arthur |author-link=Arthur Compton |year=1956 |title=Atomic Quest |location=New York |publisher=Oxford University Press |oclc=173307}}
* {{cite book |last=Cooper |first=Dan |year=1999 |title=Enrico Fermi: And the Revolutions in Modern physics |location=New York |publisher=Oxford University Press |url=https://archive.org/details/enricofermirevol00coop |url-access=registration |isbn=978-0-19-511762-2 |oclc=39508200 }}
* {{cite book  |last=Fermi |first=Enrico |contribution=The Future of Nuclear Physics |editor-last=Cronin |editor-first=J.W |year=2004 |title=Fermi Remembered |publisher=University of Chicago Press |location=Chicago |isbn=978-0-226-12111-6}}
* {{cite book |last=Fermi |first=Laura |author-link=Laura Fermi |year=1954 |title=Atoms in the Family: My Life with Enrico Fermi |url=https://archive.org/details/atomsinfamilymyl00fermrich |url-access=registration |location=Chicago |publisher=University of Chicago Press |oclc=537507 }}
* {{cite book |last=Hawkins |first=David |year=1961 |title=Manhattan District History: Project Y – The Los Alamos Project. Volume I: Inception until August 1945 |publisher=[[Los Alamos National Laboratory]] |location=Los Alamos |id=LAMS 2532}}
* {{cite book |last=Hoff |first=Richard |editor-last=Seaborg |editor-first=Glenn T |pages=39–49 |contribution=Production of Eisteinium and Fermium in Nuclear Explosions |editor-link=Glenn T. Seaborg |url=http://www.escholarship.org/uc/item/92g2p7cd.pdf |title=Proceedings of the Symposium Commemorating the 25th Anniversary of Elements 99 and 100 |date=23 January 1978 |publisher=[[Los Alamos National Laboratory]] |location=Los Alamos |id=Report LBL-7701 |access-date=20 January 2013 |archive-date=16 September 2011 |archive-url=https://web.archive.org/web/20110916204726/http://www.escholarship.org/uc/item/92g2p7cd.pdf |url-status=live }}
* {{cite book |last1=Hewlett |first1=Richard G. |author-link=Richard G. Hewlett |last2=Anderson |first2=Oscar E. |title=The New World, 1939–1946 |location=University Park |publisher=Pennsylvania State University Press |year=1962 |url=https://www.governmentattic.org/5docs/TheNewWorld1939-1946.pdf |isbn=978-0-520-07186-5 |oclc=637004643 |access-date=2 April 2018 |archive-date=26 September 2019 |archive-url=https://web.archive.org/web/20190926065049/https://www.governmentattic.org/5docs/TheNewWorld1939-1946.pdf |url-status=live }}
* {{cite book|last1=Hewlett|first1=Richard G.|last2=Duncan|first2=Francis|title=Atomic Shield, 1947–1952|series=A History of the United States Atomic Energy Commission|publisher=Pennsylvania State University Press|location=University Park|year=1969|isbn=978-0-520-07187-2|oclc=3717478}}
* {{cite book |last1=Hey |first1=Anthony J. G. |author-link=Tony Hey |first2=Patrick |last2=Walters |year=2003 |title=The new quantum universe |location=Cambridge, U.K. |publisher=Cambridge University Press |isbn= 978-0-521-56418-2 |oclc=50252084}}
* {{cite book |last1=Holl |first1=Jack M. |last2=Hewlett |author-link2=Richard G. Hewlett |first2=Richard G. |last3=Harris |first3=Ruth R. |title=Argonne National Laboratory, 1946–96 |publisher=University of Illinois Press |location=Urbana |year=1997 |isbn=978-0-252-02341-5}}
* {{cite book |last1=Hucke |first1=Matt |first2=Ursula |last2=Bielski |title=Graveyards of Chicago: The People, History, Art, and Lore of Cook County Cemeteries |location=Chicago |publisher=Lake Claremont Press |year=1999 |isbn=978-0-9642426-4-7 |oclc=42849992}}
* {{cite book |last1=Jacob |first1=Maurice |first2=Luciano |last2=Maiani |contribution=The Scientific Legacy of Fermi in Particle Physics |pages=[https://archive.org/details/enricofermihiswo0000unse/page/241 241–270] |editor-last=Bernardini |editor-first=C. |editor2-first=Luisa |editor2-last=Bonolis |year=2001 |title=Enrico Fermi: His Work and Legacy |location=Bologna |publisher=Società Italiana di Fisica: Springer |isbn=978-88-7438-015-2 |oclc=56686431 |url=https://archive.org/details/enricofermihiswo0000unse/page/241 }}
* {{cite book |last=Jones |first=Eric M. |url=https://fas.org/sgp/othergov/doe/lanl/la-10311-ms.pdf |title="Where is Everybody?", An Account of Fermi's Question |publisher=[[Los Alamos National Laboratory]] |location=Los Alamos |id=LA-10311-MS |date=March 1985 |oclc=4434691994 |ref=CITEREFJones1985a |access-date=20 November 2015 |archive-date=5 November 2015 |archive-url=https://web.archive.org/web/20151105211510/http://www.fas.org/sgp/othergov/doe/lanl/la-10311-ms.pdf |url-status=live }}
* {{cite book |last=Jones |first=Vincent |title=Manhattan: The Army and the Atomic Bomb |publisher=United States Army Center of Military History |location=Washington, D.C. |year=1985 |oclc=10913875}}
* {{cite book |last=Persico |first=Enrico |author-link=Enrico Persico |contribution=Commemoration of Enrico Fermi |title=Enrico Fermi: His Work and Legacy |pages=[https://archive.org/details/enricofermihiswo0000unse/page/36 36–44] |editor-last=Bernardini |editor-first=C. |editor2-first=Luisa |editor2-last=Bonolis |year=2001 |location=Bologna |publisher=Società Italiana di Fisica: Springer |isbn=978-88-7438-015-2 |oclc=56686431 |url=https://archive.org/details/enricofermihiswo0000unse/page/36 }}
* {{cite book | last = Rhodes | first = Richard | author-link = Richard Rhodes | year = 1986 | title = The Making of the Atomic Bomb | url = https://archive.org/details/makingofatomicbo00rhod | url-access = registration | location = New York | publisher = Simon & Schuster | isbn = 978-0-684-81378-3 | oclc = 13793436 }}
* {{cite book |last=Ricci |first=Renato Angelo |contribution=Fermi's Last Lessons |pages=[https://archive.org/details/enricofermihiswo0000unse/page/286 286–313] |editor-last=Bernardini |editor-first=C. |editor2-first=Luisa |editor2-last=Bonolis |year=2001 |title=Enrico Fermi: His Work and Legacy |location=Bologna |publisher=Società Italiana di Fisica: Springer |isbn=978-88-7438-015-2 |oclc=56686431 |url=https://archive.org/details/enricofermihiswo0000unse/page/286 }}
* {{cite book |last=Salvini |first=Giorgio |contribution=Enrico Fermi: His Life and Comment on his Work |pages=[https://archive.org/details/enricofermihiswo0000unse/page/1 1–20] |editor-last=Bernardini |editor-first=C. |editor2-first=Luisa |editor2-last=Bonolis |year=2001 |title=Enrico Fermi: His Work and Legacy |location=Bologna |publisher=Società Italiana di Fisica: Springer |isbn=978-88-7438-015-2 |oclc=56686431 |url=https://archive.org/details/enricofermihiswo0000unse/page/1 }}
* {{cite book |last=Salvetti |first=Carlo |contribution=The Birth of Nuclear Energy: Fermi's Pile |pages=[https://archive.org/details/enricofermihiswo0000unse/page/177 177–203] |editor-last=Bernardini |editor-first=C. |editor2-first=Luisa |editor2-last=Bonolis |year=2001 |title=Enrico Fermi: His Work and Legacy |location=Bologna |publisher=Società Italiana di Fisica: Springer |isbn=978-88-7438-015-2 |oclc=56686431 |url=https://archive.org/details/enricofermihiswo0000unse/page/177 }}
* {{cite book |last=Schwartz |first=David N. |title=L'ultimo uomo che sapeva tutto |trans-title=The Last Man Who Knew Everything |publisher=Solferino, RCS MediaGroup |date=2021 |location=Milan |isbn=978-88-282-0390-2 |language=italian }}
* {{cite book |last=Seaborg |first=Glenn T. |author-link=Glenn T. Seaborg |editor-last=Seaborg |editor-first=Glenn T |pages=1–3 |contribution=Introductory Remarks |editor-link=Glenn T. Seaborg |url=http://www.escholarship.org/uc/item/92g2p7cd.pdf |title=Proceedings of the Symposium Commemorating the 25th Anniversary of Elements 99 and 100 |date=23 January 1978 |publisher=[[Los Alamos National Laboratory]] |location=Los Alamos |id=Report LBL-7701 |access-date=20 January 2013 |archive-date=16 September 2011 |archive-url=https://web.archive.org/web/20110916204726/http://www.escholarship.org/uc/item/92g2p7cd.pdf |url-status=live }}
* {{cite book |last=Segrè |first=Emilio |author-link=Emilio Segrè |title=Enrico Fermi, Physicist |url=https://archive.org/details/enricofermiphysi0000segr_q1u1 |url-access=registration |year=1970 |publisher=University of Chicago Press |location=Chicago |isbn=978-0-226-74473-5 |oclc=118467 }}
* {{cite book |last=Snow |first=C. P. |author-link=C. P. Snow |year=1981 |title=The Physicists: A Generation that Changed the World |publisher=Little Brown |location=Boston |isbn=978-1-84232-436-3 |oclc=7722354}}
* {{cite book | last=Sullivan | first=Neil J. | title=The Prometheus Bomb: The Manhattan Project and Government in the Dark | location=Lincoln | publisher=[[University of Nebraska Press]] | year=2016 | isbn=978-1-61234-890-2 | url=https://books.google.com/books?id=Md4nDwAAQBAJ | access-date=4 December 2021 | archive-date=1 December 2021 | archive-url=https://web.archive.org/web/20211201013629/https://books.google.com/books?id=Md4nDwAAQBAJ | url-status=live }}
* {{cite book |last=Von Baeyer |first=H. C. |title=The Fermi Solution: Essays on Science |url=https://archive.org/details/fermisolutioness0000vonb |url-access=registration |location=New York |publisher=Random House |year=1993 |isbn=978-0-679-40031-8 |oclc=27266040 }}
{{Refend}}

==Further reading==
* Bernstein, Barton J. "Four Physicists and the Bomb: The Early Years, 1945-1950" ''Historical Studies in the Physical and Biological Sciences'' (1988) 18#2; covers Oppenheimer, Fermi, Lawrence and Compton. [https://www.jstor.org/stable/27757603 online]
* Galison, Peter, and Barton Bernstein. "In any light: Scientists and the decision to build the Superbomb, 1952–1954." ''Historical Studies in the Physical and Biological Sciences'' 19.2 (1989): 267–347. [https://galison.scholar.harvard.edu/sites/projects.iq.harvard.edu/files/andrewhsmith/files/27757627.pdf online]

== External links ==
{{Sister project links||wikt=no|n=no|s=|b=no|v=no|voy=no}}
* [http://manhattanprojectvoices.org/oral-histories/fermi-love-part-1 "To Fermi – with Love – Part 1"]. Voices of the Manhattan Project 1971 Radio Segment
* [https://www.osti.gov/biblio/1159286-first-reactor-anniversary-rev "The First Reactor: 40th Anniversary Commemorative Edition"], [[United States Department of Energy]], (December 1982).
* [http://nobelprize.org/nobel_prizes/physics/laureates/1938/ Nobel prize page for the 1938 physics prize]
* [http://www.atomicarchive.com/History/firstpile/index.shtml The Story of the First Pile]
* [https://web.archive.org/web/20080330180911/http://www.fi.edu/learn/case-files/fermi/ Enrico Fermi's Case File] at The Franklin Institute with information about his contributions to theoretical and experimental physics.
* [http://www.aps.org/units/fhp/meetings/april10/j1.cfm "Remembering Enrico Fermi"]. Session J1. APS April Meeting 2010, American Physical Society.
* [https://web.archive.org/web/20000527131916/http://www.time.com/time/time100/scientist/profile/fermi.html Time 100: Enrico Fermi] by [[Richard Rhodes]] 29 March 1999
* [http://ilorentz.org/history/Fermi/Fermi.html Fermi's stay with Ehrenfest in Leiden].

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