Epstein, Paul S. (Paul Sophus), 1883-1966

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Physicist, California Institute of Technology, 1921-1953; taught the advanced courses in mathematical and theoretical physics. First European-trained physicist to come to Caltech on a permanent basis; recruited by Robert A. Millikan in 1921, a mathematical physicist among the generation who laid foundation for modern atomic physics. Studied in Munich under Arnold Sommerfeld; early research in theory of electromagnetic waves, particularly theory of their diffraction. Studied quantum theory of atomic structure based on classical mechanics; applying quantum theory to optics; Bohr's form of quantum theory; development of quantum mechanics. Also interested in psychoanalysis, helped establish the Los Angeles Institute of Psychoanalysis.

From the description of Papers, 1911-1966. (Unknown). WorldCat record id: 80301618


Epstein was the first European-trained physicist to come to Caltech on a permanent basis. Recruited by Robert A. Millikan in 1921, he was one of a generation of prominent mathematical physicists who laid the foundations for modern atomic physics. Having studied and worked in Moscow, Munich, Zurich and Leyden before settling permanently in the United States, Epstein had wide personal and scientific contacts.

Epstein was born in 1883 in Warsaw to a moderately well-to-do Jewish family. He grew up in Minsk and later attended the Imperial University of Moscow, where he received B.S. and M.S. degrees. Foreseeing the Russian Revolution, he left Moscow to continue his studies in theoretical physics in Munich under Arnold Sommerfeld. His early research was in the theory of electromagnetic waves, particularly the theory of their diffraction. He received his Ph.D. at the outbreak of World War I, with the thesis "Über die Beugung an einem ebenen Schirm unter Berücksichtigung des Materialeinflusses" ("Diffraction from a Plane Screen...," 1914).

Though held as a civil prisoner in Germany during the war, he nonetheless continued to do research in the problems of the quantum theory of atomic structure based on classical mechanics. An important paper from this period is "Zur Theorie des Starkeffektes" ("The Theory of the Stark Effect," Ann. der Physik 50, 1916). In 1919, with the end of the war, Epstein was able to take up an appointment as Privatdocent at the University of Zurich. Upon applying for this position he wrote a paper (Habilitationsschrift) applying the quantum theory to optics, which caused a stir ("Anwendungen der Quantenlehre in der Theorie der Serienspektren," Die Naturwissenschaften 17, 1918).

As early as 1910 or 1911, Epstein had become interested in pyschoanalysis as a remedy for depression and associated physical symptoms. This interest eventually led to a meeting with Freud in Switzerland, circa 1911-12. Later Epstein was instrumental in founding the Los Angeles Institute of Pyschoanalysis. His knowledge of and practical involvement in this field lasted throughout his life.

Having lost most of his inherited means during the war and in need of a paying position, Epstein went to Leyden in 1921 to become assistant to H. A. Lorentz. There he met Millikan, who invited him to come to the newly created California Institute of Technology. Epstein arrived in Pasadena on a blistering September day in 1921, knowing very little English. He was to remain at Caltech until his retirement in 1953 at the age of 70. During this time he taught substantially all of the advanced courses in mathematical and theoretical physics.

At Caltech Epstein's research continued on Bohr's form of the quantum theory, which culminated in 1922 with the publication of four papers, three in the Zeitschrift für Physik and one in The Physical Review . Later he participated in the development of quantum mechanics. An important paper in this connection appeared in the Physical Review in 1926: "The Stark Effect from the Point of View of Schrödinger's Quantum Theory." In 1930, Epstein was elected to the National Academy of Sciences.

Epstein's range of interests was wide. He devoted considerable attention to borderline problems involving physics and other sciences, for example, his papers "Zur Theorie des Radiometers" (1929), "Reflection of Waves in an Inhomogeneous Absorbing Medium" (1930), and "On the Air Resistance of Projectiles" (1931). He wrote two important articles on general subjects outside of physics, both published in the Los Angeles literary/philosophical journal Reflex : "The Frontiers of Science" (June, 1935) and "The Uses and Abuses of Nationalism" (November, 1935). He also maintained a number of literary and artistic contacts, including Upton Sinclair.

Although not a Zionist, Epstein was deeply interested in Jewish affairs. He was a friend and supporter of the mathematician Abraham Fraenkel, a longtime resident of Jerusalem, who played a major role in the organization of secondary and advanced education in Israel. Epstein was active for many years in the Friends of the Hebrew University of Jerusalem and was President of the Southern California Chapter.

After his retirement from Caltech, Epstein served as a consultant to several large industrial firms. Among the many reports written by him at this time, especially significant is his "Theory of Wave Propagation in a Gyromagnetic Medium" ( Reviews of Modern Physics 28, 1956).

Paul Epstein died at his home in Pasadena on February 8, 1966, at the age of 83.

From the guide to the Paul Sophus Epstein papers, 1898-1966, (California Institute of Technology. Archives.)

Archival Resources
Role Title Holding Repository
referencedIn Ewald, Paul Peter, 1888-1985. Oral history interview with Paul Peter Ewald, 1962 March 29 and 8 May. American Institute of Physics, Niels Bohr Library
referencedIn Wooldridge, Dean E. Oral history interview with Dean E. Wooldridge, 1976 August 21. American Institute of Physics, Niels Bohr Library
referencedIn Landé, Alfred, 1888-. Papers, 1915-1970. American Institute of Physics, Niels Bohr Library
referencedIn Franck, James, 1882-1964. Oral history joint interview with James Franck and Hertha Sponer-Franck, 1962 July 9 to 14. American Institute of Physics, Niels Bohr Library
referencedIn Oppenheimer, Frank, 1912-1985. Oral history interview with Frank Oppenheimer, 1984 November 16. American Institute of Physics, Niels Bohr Library
referencedIn Von Kármán, Theodore, 1881-1963. Oral history interview with Theodore Von Karman, 1962 June 29. American Institute of Physics, Niels Bohr Library
referencedIn Jordan, Pascual, 1902-1980. Oral history interview with Ernst Pascual Jordan, 1963 June 17 to 20. American Institute of Physics, Niels Bohr Library
creatorOf Epstein, Paul Sophus, 1883-1966. Papers, 1911-1966. American Institute of Physics, Niels Bohr Library
referencedIn Crane, H. R. (Horace Richard), 1907-2007. Oral history interview with H. R. Crane, 1973 March 28 and 18 June 1974. American Institute of Physics, Niels Bohr Library
referencedIn Courant, Richard, 1888-1972. Oral history interview with Richard Courant, 1962 May 9. American Institute of Physics, Niels Bohr Library
creatorOf Wise, W. Howard. Howard W. Wise lecture notes, 1926. UC Berkeley Libraries
referencedIn Eckart, Carl, 1902-1973. Oral history interview with Carl Henry Eckart, 1962 May 31. American Institute of Physics, Niels Bohr Library
referencedIn Bohr, Niels, 1885-1962. Bohr scientific correspondence, supplement, 1910-1962. American Institute of Physics, Niels Bohr Library
referencedIn Boris Souvarine papers, 1915-1984 (inclusive), 1940-1984 (bulk). Houghton Library, , Harvard College Library, Harvard University
referencedIn Archive for the History of Quantum Physics, 1898-1950 (bulk), 1898-1950 American Philosophical Society
referencedIn Friedrich, Walter, 1883-1968. Oral history interview with Walter Friedrich, 1963 May 15. American Institute of Physics, Niels Bohr Library
referencedIn Rubinowicz, Wojciech. Oral history interview with Wojciech Rubinowicz, 1963 May 18. American Institute of Physics, Niels Bohr Library
creatorOf Paul Sophus Epstein papers, 1898-1966 California Institute of Technology. Archives.
creatorOf Epstein, Paul Sophus, 1883-1966. Oral history interview with Paul Sophus Epstein, 1962 May 25 to 2 June. American Institute of Physics, Niels Bohr Library
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associatedWith Benedicks, Carl Axel Fredrik, 1875-1953 person
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associatedWith Wooldridge, Dean E. person
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Place Name Admin Code Country
Electromagnetic theory
Quantum theory
Nuclear physics
Mathematical physics
Atomic theory
Physics--Study and teaching
Quantum mechanics


Birth 1883-03-20

Death 1966-02-08





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