Editing Richard Feynman (section)

== Manhattan Project ==
[[File:Feynman-richard_p.jpg|thumb|upright|alt=Feynman smiling|Feynman's Los Alamos ID badge]]
In 1941, with [[World War II]] occurring in Europe but the United States not yet at war, Feynman spent the summer working on ballistics problems at the [[Frankford Arsenal]] in [[Pennsylvania]].{{sfn|Gribbin|Gribbin|1997|pp=63–64}}{{sfn|Feynman|1985|pp=99–103}} After the [[attack on Pearl Harbor]] brought the United States into the war, Feynman was recruited by [[Robert R. Wilson]], who was working on means to produce [[enriched uranium]] for use in an [[atomic bomb]], as part of what would become the [[Manhattan Project]].{{sfn|Gribbin|Gribbin|1997|pp=64–65}}{{sfn|Feynman|1985|pp=107–108}} At the time, Feynman had not earned a graduate degree.<ref>[https://www.youtube.com/watch?v=uY-u1qyRM5w&t=2m16s Richard Feynman Lecture – "Los Alamos From Below"] {{Webarchive|url=https://web.archive.org/web/20200505010623/https://www.youtube.com/watch?v=uY-u1qyRM5w |date=May 5, 2020}}, talk given at [[UCSB]] in 1975 (posted to YouTube on July 12, 2016)<br />Quote:<br />"I did not even have my degree when I started to work on stuff associated with the Manhattan Project."<br />Later in this same talk, [https://www.youtube.com/watch?v=uY-u1qyRM5w&t=5m34s at 5m34s] {{Webarchive|url=https://web.archive.org/web/20220304123519/https://www.youtube.com/watch?v=uY-u1qyRM5w&t=5m34s |date=March 4, 2022}}, he explains that he took a six week vacation to finish his thesis so received his PhD prior to his arrival at Los Alamos.</ref> Wilson's team at Princeton was working on a device called an isotron, intended to electromagnetically separate [[uranium-235]] from [[uranium-238]]. This was done in a quite different manner from that used by the [[calutron]] that was under development by a team under Wilson's former mentor, [[Ernest O. Lawrence]], at the [[Lawrence Berkeley Laboratory|Radiation Laboratory]] of the [[University of California, Berkeley|University of California]]. On paper, the isotron was many times more efficient than the calutron, but Feynman and [[Paul Olum]] struggled to determine whether it was practical. Ultimately, on Lawrence's recommendation, the isotron project was abandoned.{{sfn|Gleick|1992|pp=141–145}}

At this juncture, in early 1943, [[Robert Oppenheimer]] was establishing the [[Los Alamos Laboratory]], a secret laboratory on a [[mesa]] in [[New Mexico]] where atomic bombs would be designed and built. An offer was made to the Princeton team to be redeployed there. "Like a bunch of professional soldiers," Wilson later recalled, "we signed up, en masse, to go to Los Alamos."{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|p=59}} Oppenheimer recruited many young physicists, including Feynman, who he telephoned long distance from Chicago to inform that he had found a Presbyterian [[sanatorium]] in [[Albuquerque, New Mexico]] for Arline. They were among the first to depart for New Mexico, leaving on a train on March 28, 1943. The railroad supplied Arline with a wheelchair, and Feynman paid extra for a private room for her. There they spent their wedding anniversary.{{sfn|Gleick|1992|pp=158–160}}

At Los Alamos, Feynman was assigned to Hans Bethe's Theoretical (T) Division,{{sfn|Gleick|1992|pp=165–169}} and impressed Bethe enough to be made a group leader.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|pp=157–159}} He and Bethe developed the [[Bethe–Feynman formula]] for calculating the yield of a [[Nuclear weapon design|fission bomb]], which built upon previous work by [[Robert Serber]].{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|p=183}} As a junior physicist, he was not central to the project. He administered the computation group of [[human computer]]s in the theoretical division. With [[Stanley Frankel]] and [[Nicholas Metropolis]], he assisted in establishing a system for using [[IBM]] [[punched card]]s for computation.{{sfn|Bashe|Johnson|Palmer|Pugh|1986|p=14}} He invented a new method of computing [[Logarithm#Calculation|logarithms]] that he later used on the [[Connection Machine]].{{sfn|Hillis|1989|p=78}}{{sfn|Feynman|1985|pp=125–129}} An avid drummer, Feynman figured out how to get the machine to click in musical rhythms.{{sfn|Gleick|1992|p=181}} Other work at Los Alamos included calculating [[neutron]] equations for the Los Alamos "Water Boiler", a small [[nuclear reactor]], to measure how close an assembly of fissile material was to criticality.{{sfn|Galison|1998|pp=403–407}}

On completing this work, Feynman was sent to the [[Clinton Engineer Works]] in [[Oak Ridge, Tennessee]], where the Manhattan Project had its [[uranium enrichment]] facilities. He aided the engineers there in devising safety procedures for material storage so that [[criticality accident]]s could be avoided, especially when [[enriched uranium]] came into contact with water, which acted as a [[neutron moderator]]. He insisted on giving the rank and file a lecture on nuclear physics so that they would realize the dangers.{{sfn|Galison|1998|pp=407–409}} He explained that while any amount of unenriched uranium could be safely stored, the enriched uranium had to be carefully handled. He developed a series of safety recommendations for the various grades of enrichments.<ref>{{cite web |url=https://blog.nuclearsecrecy.com/2014/06/06/feynman-and-the-bomb/ |title=Feynman and the Bomb |website=Restricted Data |first=Alex |last=Wellerstein |author-link=Alex Wellerstein |date=June 6, 2014 |access-date=June 10, 2023}}</ref> He was told that if the people at Oak Ridge gave him any difficulty with his proposals, he was to inform them that Los Alamos "could not be responsible for their safety otherwise".{{sfn|Feynman|1985|p=122}}

[[File:Los Alamos colloquium.jpg|thumb|alt=A crowd seated in folding chairs|left|At the 1946 colloquium on the [[History of the Teller–Ulam design#Teller's "Super"|"Super"]] at the [[Los Alamos Laboratory]]. Feynman is in the second row, fourth from left, next to Oppenheimer.]]
Returning to Los Alamos, Feynman was put in charge of the group responsible for the theoretical work and calculations on the proposed [[uranium hydride bomb]], which ultimately proved to be infeasible.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|pp=157–159}}{{sfn|Galison|1998|pp=414–422}} He was sought out by physicist [[Niels Bohr]] for one-on-one discussions. He later discovered the reason: most of the other physicists were too much in awe of Bohr to argue with him. Feynman had no such inhibitions, vigorously pointing out anything he considered to be flawed in Bohr's thinking. He said he felt as much respect for Bohr as anyone else, but once anyone got him talking about physics, he would become so focused he forgot about social niceties. Perhaps because of this, Bohr never warmed to Feynman.{{sfn|Gleick|1992|p=257}}{{sfn|Gribbin|Gribbin|1997|pp=95–96}}

At Los Alamos, which was isolated for security, Feynman amused himself by investigating the combination locks on the cabinets and desks of physicists. He often found that they left the lock combinations on the factory settings, wrote the combinations down, or used easily guessable combinations like dates.{{sfn|Gleick|1992|pp=188–190}} He found one cabinet's combination by trying numbers he thought a physicist might use (it proved to be 27–18–28 after the base of [[natural logarithm]]s, ''[[e (number)|e]]'' = 2.71828 ...), and found that the three filing cabinets where a colleague kept research notes all had the same combination. He left notes in the cabinets as a prank, spooking his colleague, [[Frederic de Hoffmann]], into thinking a spy had gained access to them.{{sfn|Feynman|1985|pp=147–149}}{{sfn|Pugh|2017|pp=1–2}}

Feynman's $380 ({{Inflation|US|380|1943|fmt=eq|r=-3}}) monthly salary was about half the amount needed for his modest living expenses and Arline's medical bills, and they were forced to dip into her $3,300 ({{Inflation|US|3300|1943|fmt=eq|r=-3}}) in savings.{{sfn|Gribbin|Gribbin|1997|p=99}} On weekends he borrowed a car from his friend [[Klaus Fuchs]] to drive to Albuquerque to see Arline.{{sfn|Gleick|1992|p=184}}{{sfn|Gribbin|Gribbin|1997|p=96}} Asked who at Los Alamos was most likely to be a spy, Fuchs mentioned Feynman's [[safe-cracking]] and frequent trips to Albuquerque;{{sfn|Gleick|1992|p=184}} Fuchs himself later confessed to spying for the [[Soviet Union]].{{sfn|Gleick|1992|pp=296–297}} The [[FBI]] would compile a bulky file on Feynman,<ref>{{cite web |last1=Morisy |first1=Michael |last2=Hovden |first2=Robert |date=June 6, 2012 |editor=J Pat Brown |title=The Feynman Files: The professor's invitation past the Iron Curtain |url=https://www.muckrock.com/news/archives/2012/jun/06/feynman-files-professors-invitation-past-iron-curt/ |archive-url=https://web.archive.org/web/20190505211540/https://www.muckrock.com/news/archives/2012/jun/06/feynman-files-professors-invitation-past-iron-curt/ |archive-date=May 5, 2019 |access-date=July 13, 2016 |website=MuckRock}}</ref> particularly in view of Feynman's [[Q clearance]].<ref>{{cite web|author=SAC (Special Agent in Charge ), Washington Field Office)|url=https://www.documentcloud.org/documents/366921-responsive-documents.html#document/p324|title=FOI Request FBI files on Richard Feynman Requested by Michael Morisy on March 12, 2012 for the Federal Bureau of Investigation of United States of America and fulfilled on March 21, 2012|date=January 26, 1955|access-date=June 10, 2023|page=1(324)}}{{blockquote|text=In a report by SA{{redacted content|foia-exceptions=(b)(7)(c)}} at [[Albuquerque, New Mexico]], dated 3/14/50 captioned{{redacted content|foia-exceptions=(b)(7)(c)}}-R,"<!-- -R," with unbalanced double quote in original --> there is set forth the fact that RICHARD PHILLIPS [F]EYNMAN was employed at Los Alamos, New Mexico, on the atomic bomb project in the Theoretical Physics Division from April 1, 1943, to October 27, 1945. This individual, according to this report, was granted Atomic Energy Commission security clearance rating of '''Q clearance''' on 5/25/49.}}</ref>

[[File:Feynman and Oppenheimer at Los Alamos.jpg|alt=The scientists standing in a semi-circle, wearing suits|thumb|Feynman (center) with [[Robert Oppenheimer]] (immediately right of Feynman) at a Los Alamos Laboratory social function during the Manhattan Project]]
Informed that Arline was dying, Feynman drove to Albuquerque and sat with her for hours until she died on June 16, 1945.{{sfn|Gleick|1992|pp=200–202}} He then immersed himself in work on the project and was present at the [[Trinity nuclear test]]. Feynman claimed to be the only person to see the explosion without the very dark glasses or welder's lenses provided, reasoning that it was safe to look through a truck windshield, as it would screen out the harmful [[ultraviolet]] radiation. The immense brightness of the explosion made him duck to the truck's floor, where he saw a temporary "purple splotch" [[afterimage]].{{sfn|Feynman|1985|p=134}}