Editing Eugene Wigner (section)

==Manhattan Project==
[[File:Eugene Wigner receiving Medal for Merit cph.3a38621.jpg|thumb|Wigner receiving the [[Medal for Merit]] for his work on the Manhattan Project from [[Robert P. Patterson]] (left), March 5, 1946]]
Although he was a professed political amateur, on August 2, 1939, he participated in a meeting with [[Leo Szilard|Leó Szilárd]] and [[Albert Einstein]] that resulted in the [[Einstein–Szilárd letter]], which prompted President [[Franklin D. Roosevelt]] to authorize the creation of the [[Advisory Committee on Uranium]] with the purpose of investigating the feasibility of [[Nuclear weapon|atomic bombs]].{{sfn|Szanton|1992|pp=197–202}} Wigner was afraid that the [[German nuclear weapon project]] would develop an atomic bomb first, and even refused to have his fingerprints taken because they could be used to track him down if Germany won.{{sfn|Szanton|1992|p=215}} "Thoughts of being murdered," he later recalled, "focus your mind wonderfully."{{sfn|Szanton|1992|p=215}}

On June 4, 1941, Wigner married his second wife, Mary Annette Wheeler, a professor of physics at [[Vassar College]], who had completed her Ph.D. at [[Yale University]] in 1932. After the war she taught physics on the faculty of [[Rutgers University]]'s [[Douglass Residential College|Douglass College]] in New Jersey until her retirement in 1964. They remained married until her death in November 1977.{{sfn|Szanton|1992|pp=205–207}}<ref>{{cite journal|title=Obituary: Mary Wigner|journal=Physics Today|date=July 1978|volume=31|issue=7|pages=58|url=http://www.physicstoday.org/resource/1/phtoad/v31/i7/p58_s2?bypassSSO=1|archive-url=https://archive.today/20130927144256/http://www.physicstoday.org/resource/1/phtoad/v31/i7/p58_s2?bypassSSO=1|url-status=dead|archive-date=2013-09-27|doi=10.1063/1.2995119|bibcode=1978PhT....31g..58.}}</ref> They had two children, David Wigner and Martha Wigner Upton.<ref>{{cite web|url=http://www-history.mcs.st-andrews.ac.uk/Biographies/Wigner.html |publisher=St Andrews University |title=Wigner Biography |access-date=August 10, 2013 }}</ref>

During the Manhattan Project, Wigner led a team that included [[J. Ernest Wilkins Jr.]], [[Alvin M. Weinberg]], [[Katharine Way]], [[Gale Young]] and [[Edward Creutz]]. The group's task was to design the production nuclear reactors that would convert uranium into weapons grade plutonium.  At the time, reactors existed only on paper, and no reactor had yet [[Criticality (status)|gone critical]]. In July 1942, Wigner chose a conservative 100 MW design, with a [[graphite]] [[neutron moderator]] and water cooling.{{sfn|Szanton|1992|pp=217–218}} Wigner was present at a converted rackets court under the stands at the [[University of Chicago]]'s abandoned [[Stagg Field]] on December 2, 1942, when the world's first atomic reactor, [[Chicago Pile-1|Chicago Pile One (CP-1)]] achieved a controlled [[nuclear chain reaction]].<ref>{{cite web |url=http://www.anl.gov/Science_and_Technology/History/cp1list.html |title=Chicago Pile 1 Pioneers |publisher=[[Los Alamos National Laboratory]] |access-date=August 10, 2013 |archive-url=https://web.archive.org/web/20120204040953/http://www.anl.gov/Science_and_Technology/History/cp1list.html |archive-date=February 4, 2012 |url-status=dead }}</ref>
[[File:HD.5A.036 (10555475386).jpg|thumb|left|upright|The [[Chianti]] [[Fiasco (bottle)|fiasco]] purchased by Wigner to help celebrate the first self-sustaining, controlled chain reaction. It was signed by the participants.]]
Wigner was disappointed that [[DuPont]] was given responsibility for the detailed design of the reactors, not just their construction. He threatened to resign in February 1943, but was talked out of it by the head of the [[Metallurgical Laboratory]], [[Arthur Compton]], who sent him on vacation instead. As it turned out, a design decision by DuPont to give the reactor additional load tubes for more uranium saved the project when [[neutron poison]]ing became a problem.{{sfn|Szanton|1992|pp=233–235}} Without the additional tubes, the reactor could have been run at 35% power until the boron impurities in the graphite were burned up and enough plutonium produced to run the reactor at full power; but this would have set the project back a year.{{sfn|Wigner|Weinberg|1992|p=8}} During the 1950s, he would even work for DuPont on the [[Savannah River Site]].{{sfn|Szanton|1992|pp=233–235}} Wigner did not regret working on the bomb,{{sfn|Szanton|1992|p=249}} remarking:<ref>{{cite book |last1=Mehra |first1=Jagdish |title=The Collected Works of Eugene Paul Wigner, Part A, Volume I |date=1993 |publisher=Springer |isbn=978-3-642-08154-5 |page=12 |chapter=Eugene Paul Wigner: A Biographical Sketch}}</ref>
{{blockquote
  | text=In fact, my regret is that it was not done sooner. If we had begun trying seriously to control fission in 1939, we might have had an atomic bomb by the Winter of 1943-1944. At that time Stalin's army was still bottled up in Stalingrad. By the middle of 1945, when we first used the bomb, they had already overrun much of Central Europe. The Yalta Conference would have produced a document much less favourable to Russia, and even Communist China might have been set back. So I do not regret helping to build the bomb.
}}

An important discovery Wigner made during the project was the [[Wigner effect]]. This is a swelling of the graphite moderator caused by the displacement of atoms by [[neutron radiation]].<ref>{{cite journal | doi = 10.1063/1.1707653 | title = Theoretical Physics in the Metallurgical Laboratory of Chicago | year = 1946 | last1 = Wigner | first1 = E. P. | journal = Journal of Applied Physics | volume = 17 | issue = 11 | pages = 857–863|bibcode = 1946JAP....17..857W }}</ref> The Wigner effect was a serious problem for the reactors at the [[Hanford Site]] in the immediate post-war period, and resulted in production cutbacks and a reactor being shut down entirely.{{sfn|Rhodes|1995|p=277}} It was eventually discovered that it could be overcome by controlled heating and annealing.<ref>{{cite web |url=http://users.physics.harvard.edu/~wilson/publications/ppaper848.html |title=A young Scientist's Meetings with Wigner in America |first=Richard |last=Wilson |publisher=Wigner Symposium, Hungarian Academy of Sciences |location=Budapest |date=November 8, 2002 |access-date=May 16, 2015 |url-status=dead |archive-url= https://web.archive.org/web/20150521034509/http://users.physics.harvard.edu/~wilson/publications/ppaper848.html |archive-date= May 21, 2015 }}</ref>

Through Manhattan project funding, Wigner and [[Leonard Eisenbud]] also developed an important general approach to nuclear reactions, the Wigner–Eisenbud R-matrix theory, which was published in 1947.<ref>{{cite web |url=http://ocw.mit.edu/courses/nuclear-engineering/22-106-neutron-interactions-and-applications-spring-2010/lecture-notes/MIT22_106S10_lec04b.pdf |title=Brief Review of R-Matrix Theory |first=L. C. |last=Leal  |website=MIT OpenCourseWare |access-date=August 12, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20131111071906/http://ocw.mit.edu/courses/nuclear-engineering/22-106-neutron-interactions-and-applications-spring-2010/lecture-notes/MIT22_106S10_lec04b.pdf |archive-date= Nov 11, 2013 }}
* The original paper is {{cite journal|last1=Wigner|first1=E. P.|last2=Eisenbud|first2=L.|title=Higher Angular Momenta and Long Range Interaction in Resonance Reactions|journal=Physical Review|date=1 July 1947|volume=72|issue=1|pages=29–41|doi=10.1103/PhysRev.72.29|bibcode = 1947PhRv...72...29W }}</ref>