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{{Short description|American physicist (1900–1988)}}
{{Infobox scientist
| name              = George Uhlenbeck
| image             = George E Uhlenbeck.jpg
| image_size        = 
| birth_name        = George Eugene Uhlenbeck
| birth_date        = {{birth date|1900|12|6}}
| birth_place       = [[Batavia, Dutch East Indies]] (now [[Jakarta]])
| death_date        = {{death date and age|1988|10|31|1900|12|6}}
| death_place       = [[Boulder, Colorado]], US
| nationality       = American
| fields            = [[Physicist]]
| workplaces        = [[Columbia University]]<br />[[MIT]]<br />[[University of Michigan]]<br />[[Rockefeller University|Rockefeller Institute]]<br />[[Princeton University]]
| alma_mater        = [[University of Leiden]]
| doctoral_advisor  = [[Paul Ehrenfest]]
| aca demic_advisors = 
| doctoral_students = [[Max Dresden]]<br />[[George W. Ford]]<br />[[Emil Konopinski]]<br>[[Edwin Albrecht Uehling]]<br>[[Seth Putterman]]<br>[[Wang Chengshu]]<br>[[Harold Hwa-Ling Szu]]
| notable_students  = 
| known_for         = [[Spin (physics)|Electron spin]]<br>[[Ornstein–Uhlenbeck process]]<br>[[Quantum Boltzmann equation|Uehling–Uhlenbeck equation]]
| author_abbrev_bot = 
| author_abbrev_zoo = 
| awards            = [[Oersted Medal]] (1955)<br />[[Max Planck medal]] (1964)<br />[[Lorentz Medal]] (1970)<br />[[National Medal of Science]] (1977)<br />[[Wolf Prize in Physics]] (1979)
| religion          = 
| signature         = <!--(filename only)-->
| children          = [[Olke C. Uhlenbeck]]
}}

'''George Eugene Uhlenbeck''' (December 6, 1900 – October 31, 1988) was a Dutch-American theoretical [[physicist]],<ref>{{cite journal|author=Dresden, Max|title=George E. Uhlenbeck|journal=Physics Today|date=December 1989|volume=42|issue=12|pages=91–94|url=http://www.physicstoday.org/resource/1/phtoad/v42/i12/p91_s1?bypassSSO=1|doi=10.1063/1.2811256|bibcode=1989PhT....42l..91D|url-status=dead|archive-url=https://web.archive.org/web/20131005013456/http://www.physicstoday.org/resource/1/phtoad/v42/i12/p91_s1?bypassSSO=1|archive-date=2013-10-05}}</ref> known for his significant contributions to [[quantum mechanics]] and [[statistical mechanics]]. He co-developed the concept of electron [[Spin (physics)|spin]], alongside [[Samuel Goudsmit]], in 1925. The formalization of [[Langevin equation]] for the [[Brownian motion]] as a [[stochastic process]], is known as the [[Ornstein–Uhlenbeck process]], derived in 1930 from his work with [[Leonard Ornstein]].  [[I. I. Rabi]] said that Uhlenbeck and Goudsmit's omission for the [[Nobel Prize in Physics]] "will always be a mystery to me".<ref name=NYTObit>{{cite news| title=George E. Uhlenbeck Dies at 87; Co-Discoverer of Electron's Spin|  last=Sullivan| first=George E.| date=November 2, 1988| work= [[The New York Times]]| url=https://www.nytimes.com/1988/11/02/obituaries/george-e-uhlenbeck-dies-at-87-co-discoverer-of-electron-s-spin.html}}</ref>

==Background and education==

George Uhlenbeck was the son of Eugenius and Anne Beeger Uhlenbeck. He attended the Hogere Burgerschool (High School) in [[The Hague]], from which he graduated in 1918.

He subsequently entered [[Delft University of Technology]] as a student in [[chemical engineering]]. During the next year, he transferred to [[Leiden University]], to study physics and mathematics, and he earned his bachelor's degree in 1920 (Dutch: ''Kandidaatsexamen''). Uhlenbeck was then admitted by [[Paul Ehrenfest|Ehrenfest]] (a student of [[Boltzmann]]'s) to the Wednesday evening physics colloquium in [[Leiden]]. Ehrenfest became the most important scientific influence in his life. From 1922 to 1925 Uhlenbeck was the tutor of the younger son of the Dutch [[ambassador]] in [[Rome]]. While there, he attended lectures by [[Tullio Levi-Civita]] and [[Vito Volterra]] and met his longtime friend, [[Enrico Fermi]]. In 1923, Uhlenbeck received his master's degree from Leiden (Dutch: ''Doctoraalexamen'').

[[File:ElectronSpinLeiden2017.jpg|thumb|Visualization of electron spin on a wall in Leiden]]
He returned to Leiden in 1925 to become Ehrenfest's assistant. Ehrenfest assigned him to work with his graduate student, [[Samuel Goudsmit]] for a quick update on "what was currently happening in physics". In mid-September 1925, Uhlenbeck and Goudsmit introduced [[electron spin]], which posits intrinsic [[angular momentum]] for the electron. In 1927 Uhlenbeck earned his Ph.D. degree under Ehrenfest with his thesis titled: "Over Statistische Methoden in de Theorie der Quanta" ("On Statistical Methods in the Quantum Theory" ).<ref>{{cite web|author=George Uhlenbeck |url=http://ilorentz.org/history/proefschriften/sources/Uhlenbeck_1927.pdf |title=Over statistische methoden in de theorie der quanta |year=1927}}</ref>

Uhlenbeck married Else Ophorst in [[Arnhem]], Netherlands in August 1927. He received a doctorate from the [[Leiden University]] in the same year.

==Career==

[[File:UhlenbeckKramersGoudsmit.jpg|thumb|G.E. Uhlenbeck, [[Hendrik Kramers|H.A. Kramers]], and [[Samuel Goudsmit|S.A. Goudsmit]] circa 1928 at the [[University of Michigan]] in [[Ann Arbor]]]]

In 1927, Uhlenbeck took a position as an instructor in physics at the [[University of Michigan]] in [[Ann Arbor, Michigan]]. He stayed there until 1935, when he succeeded [[Hans Kramers|H. A. Kramers]] as a professor of theoretical physics in [[Utrecht]]. During his eight years in Ann Arbor, Uhlenbeck organized the noted "Summerschool" in theoretical physics.

In 1938, Uhlenbeck spent half a year as visiting professor at [[Columbia University]] in [[New York City]], and then he returned to Ann Arbor as a professor of theoretical physics during the next year.  Because of the rise of Nazism in Europe, he and Else decided to leave his position in the Netherlands and return to America.

During part of [[World War II]], from 1943 through 1945, Uhlenbeck led a theory group at the [[MIT Radiation Laboratory|Radiation Laboratory]] in [[Cambridge, Massachusetts]], which was doing [[radar]]
research. In 1945, he returned to Ann Arbor, where he was named the [[Henry Smith Carhart]] Professor of Physics in 1954. In the year 1955 he occupied the Lorentz Chair at Leiden University.<ref>{{cite web|author=George Uhlenbeck |url=https://ilorentz.org/lorentzchair/Uhlenbeck_1955_English.pdf |title=Old and New Questions of Physics |year=1955}}</ref>
Uhlenbeck remained in Ann Arbor until 1960, when he joined the Rockefeller Institute for Medical Research (now the [[Rockefeller University]]) in New York City as a professor and member of the institute.

Uhlenbeck developed the physical theory of the [[Ornstein–Uhlenbeck process]].{{citation needed|date=March 2019}}

==Retirement and death==
He retired in 1971, but remained scientifically active until the early 1980s.

Uhlenbeck died on October 31, 1988, in [[Boulder, Colorado]], at the age of 87.

==Recognition==
Uhlenbeck received five honorary degrees. In addition, he received the Research Corporation award in 1953, the Oersted Medal of the American Association of Physics Teachers in 1955, the [[Max Planck Medal]] of the German Physical Society in 1964, the [[Lorentz Medal]] of the [[Royal Netherlands Academy of Arts and Sciences]] in 1970, the [[National Medal of Science]] in 1977, along with Goudsmit, and the [[Wolf Prize in Physics]] in 1979.

In 1951 he became member of the Royal Netherlands Academy of Arts and Sciences.<ref>{{cite web|url=http://www.dwc.knaw.nl/biografie/pmknaw/?pagetype=authorDetail&aId=PE00003410 |title=George Eugène Uhlenbeck (1900 - 1988) |publisher=Royal Netherlands Academy of Arts and Sciences |access-date=17 July 2015}}</ref> He was elected to the United States [[National Academy of Sciences]] in 1955,<ref>{{Cite web |title=George E. Uhlenbeck |url=http://www.nasonline.org/member-directory/deceased-members/49615.html |access-date=2022-12-20 |website=www.nasonline.org}}</ref> the [[American Philosophical Society]] in 1957,<ref>{{Cite web |title=APS Member History |url=https://search.amphilsoc.org/memhist/search?creator=George+Uhlenbeck&title=&subject=&subdiv=&mem=&year=&year-max=&dead=&keyword=&smode=advanced |access-date=2022-12-20 |website=search.amphilsoc.org}}</ref> and the [[American Academy of Arts and Sciences]] in 1964.<ref>{{Cite web |title=George Eugene Uhlenbeck |url=https://www.amacad.org/person/george-eugene-uhlenbeck |access-date=2022-12-20 |website=American Academy of Arts & Sciences |language=en}}</ref>

Uhlenbeck was a friend of many of the great [[physicist]]s and [[mathematician]]s of his era, including [[Enrico Fermi]] and [[Oskar Klein]]. [[Abraham Pais]] called him "a supurb teacher. I never heard a man who could lecture with such clarity.<ref name=NYTObit/> [[E.G.D. Cohen]], a student of Uhlenbeck's, described his teacher:<ref>{{cite journal |first=E. G. D. |last=Cohen |author-link=E.G.D. Cohen |title=George E. Uhlenbeck and statistical mechanics |journal=[[American Journal of Physics|Am. J. Phys.]] |volume=58 |issue=7 |year=1990 |pages=619–625 |doi=10.1119/1.16504 |bibcode = 1990AmJPh..58..619C }}</ref>

<blockquote>... [Uhlenbeck] often admonished me that rather than trying to be original, it was much more important to be clear and correct and to summarise critically the present status of a field in the [[Paul Ehrenfest |Ehrenfest]] tradition. He wisely observed that what is often of lasting value is not the first original contribution to a problem, but rather the final clearly and critically written survey. That is certainly what he did in this Brownian motion paper!</blockquote>

Describing Uhlenbeck's work, Cohen writes:

<blockquote>Uhlenbeck's papers are all relatively short and stand out by their conciseness, precision, and clarity, finely honed to a deeper understanding of a basic problem in statistical physics. They do not contain long formal derivations and are almost all geared to concrete problems. ... they were of a classic nobility, mathematical purity and clarity ... He felt that something really original one did only once – like the electron-spin--the rest of one's time one spent on clarifying the basics.</blockquote>

Cohen also comments on the high quality of Uhlenbeck's teaching:

<blockquote>He was an inspiring teacher. With superbly organised and extremely clear lectures, he laid bare for everyone to see the beautiful structure of statistical mechanics, based on the principles of the founding fathers, [[James Clerk Maxwell |Maxwell]], [[Ludwig Boltzmann |Boltzmann]], and [[Josiah Willard Gibbs| Gibbs]]. Thus he transmitted to a younger generation what he conceived to be the essence of the past and the way to the future. In doing so, he educated several generations of physicists in statistical mechanics in a style rare in this century.
</blockquote>

==See also==
*[[Ornstein–Uhlenbeck process]]

==References==
{{reflist}}

==External links==
{{commons|George Eugene Uhlenbeck}}
* K. van Berkel, [http://www.inghist.nl/Onderzoek/Projecten/BWN/lemmata/bwn6/uhlenbeck ''Uhlenbeck, George Eugène (1900–1988)''], in Biografisch Woordenboek van Nederland.
* {{MacTutor Biography|id=Uhlenbeck}}
* [http://www.lorentz.leidenuniv.nl/history/spin/goudsmit.html S.A. Goudsmit. ''The discovery of the electron spin'']
* {{MathGenealogy|58901}}

{{Wolf Prize in Physics}}
{{Presidents of the American Physical Society}}

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{{DEFAULTSORT:Uhlenbeck, George Eugene}}
[[Category:20th-century Dutch physicists]]
[[Category:1900 births]]
[[Category:1988 deaths]]
[[Category:American probability theorists]]
[[Category:Fellows of the American Physical Society]]
[[Category:Members of the Royal Netherlands Academy of Arts and Sciences]]
[[Category:National Medal of Science laureates]]
[[Category:Lorentz Medal winners]]
[[Category:Wolf Prize in Physics laureates]]
[[Category:Columbia University faculty]]
[[Category:University of Michigan faculty]]
[[Category:Dutch emigrants to the United States]]
[[Category:People from Batavia, Dutch East Indies]]
[[Category:20th-century American physicists]]
[[Category:Winners of the Max Planck Medal]]
[[Category:Presidents of the American Physical Society]]
[[Category:Members of the American Philosophical Society]]
[[Category:Leiden University alumni]]