C8 Spin of the Electron

In the fall of 1925 University of Leiden graduate students Sam Goudsmit and George Uhlenbeck were puzzling over “those complicated Zeeman effects” and the mystery of the fourth quantum number assigned to the spectrum of hydrogen.  Uhlenbeck exclaimed: “it means there is a fourth degree of freedom of the electron…it must be rotating!”.  Electron spin provided the quantitative explanation of the anomalous Zeeman effect and a key to our modern understanding of atomic structure.  In 1927 one month after receiving their doctoral degrees the two began careers as instructors at the University of Michigan.




Samuel A Goudsmit (1902-1978) studied physics at the University of Leiden under Paul Ehrenfest,[3] where he obtained his PhD in 1927 and accepted an assistant professorship at the University of Michigan where he, together with Uhlenbeck, Dennison, and Laporte formed the core of a world-leading group in theoretical physics. In 1930 Goudsmit and Linus Pauling published The Structure of Line Spectra, this followed in 1932 with the publication of Atomic Energy States” by Goudsmit and his student Robert Bacher who was later to become president of CalTech.

During World War II Goudsmit worked at the Massachusetts Institute of Technology. After the war he was the scientific leader of the mission that successfully captured the German group of nuclear physicists who had been working to develop their own atomic bomb. He described this experience in his 1947 book Alsos

After the war he was briefly a professor at Northwestern University and from 1948-1970 was a senior scientist at the Brookhaven National Laboratory, chairing the Physics Department 1952-1960. He became editor-in-chief of the Physical Review, and in 1958 he started the journal Physical Review Letters. On his retirement as editor in 1974, Goudsmit moved to the faculty of the University of Nevada in Reno, where he remained until his death four years later.

His had a deep interest in Egyptology: The Samuel A. Goudsmit Collection of Egyptian Antiquities is at the Kelsey Museum of Archaeology at the University of Michigan




George Uhlenbeck (1900-1988) was born in what was then Batavia, Java. In 1907 the family resettled in Holland. He did his doctoral thesis on statuistical mechanics under Paul Ehrenfest at Leiden. Soon after coming to Ann Arbor he established the Wednesday Colloquium, following the Ehrenfest model in Leiden. Together with colleagues Samuel Goudsmit, David Dennison and Otto Laporte and under the leadership of Chairman Harrison Randall they organized and participated in the famous Summer Schools that attracted world leaders in Theoretical Physics to Ann Arbor. In 1935 Uhlenbeck left to become professor at Utrecht, returning in 1939. From 1943 to1945 he took leave to direct the theoretical group at the MIT Radiation Laboratory in Cambridge, MA. Their wartime research, largely devoted to waveguide theory and noise in radar systems, is summarized in the book “Threshold Signals” edited jointly with J.J. Lawson. In 1960 he left Ann Arbor for Rockefeller University. In a long career George Uhlenbeck made important contributions to atomic, molecular and nuclear physics and above all to statistical mechanics. He was a superb lecturer and expositor with a deep grasp of his subject and an orderly delivery of great clarity, spiced with subtle humor.


Although their names are frequently mentioned together, they pursued distinctively different research problems, Goudsmit on atomic structure, Uhlenbeck on statistical mechanics and nuclear theory.