Hans Bethe and American Physics

1. Hans Bethe and American Physics William H. Ingham Department of Physics James Madison University Harrisonburg, VA 22807 CS-AAPT Meeting Radford University

2. Abstract Hans A. Bethe was part of what has been called the “intellectual migration,” leaving his native Germany and resettling in the United States as a young man. Over the decades since his arrival, Bethe has had a profound effect on physics and the American physics community. This presentation recounts some of the achievements of his extraordinarily long and productive career. CS-AAPT Meeting Radford University

3. Early Life (1906-1924) • Born July 2, 1906 in Strasbourg, Germany • His father was a lecturer in physiology at University of Strasbourg. • His mother was an accomplished musician and the daughter of a professor. • In 1915, family moved to Frankfurt where Hans attended the Goethe Gymnasium from 1915 to 1924. • A fellow student remembers Hans as uncoordinated in physical education but the most gifted student in every academic class and very helpful to classmates. CS-AAPT Meeting Radford University

4. Education & First Academic Jobs (1924-1929) • University of Frankfurt, 1924-1926 • University of Munich, 1926-1928 • Studied with Arnold Sommerfeld • Ph.D. thesis on the diffraction of electrons by crystals • University of Frankfurt and then Technical College of Stuttgart (one semester each as an instructor) • It was Paul P. Ewald who invited Bethe to Stuttgart as his assistant. (Bethe would marry Ewald’s daughter Rose 11 years later.) CS-AAPT Meeting Radford University

5. “European Tour” (1929-1933) • Sommerfeld reclaimed Bethe from Ewald in Fall 1929. • That winter Bethe wrote what he considers his best paper: “The Theory of the Passage of Swift Corpuscular Rays through Matter.” • In May 1930, he became a Privatdozent (unsalaried lecturer) at the University of Munich. • During 1930-32, he did postdoctoral studies in Cambridge and later in Rome with Enrico Fermi. • In 1932, Bethe and Sommerfeld wrote a famous review article “The Electron Theory of Metals” for the Handbuch der Physik. • During the winter of 1932-1933, he was Acting Assistant Professor at the University of Tubingen, where Hans Geiger was the Professor of Experimental Physics. CS-AAPT Meeting Radford University

6. Emigration (1933-1935) • The Reichstag fire occurred on February 27, 1933 and soon Hitler became Chancellor in Germany. • In April 1933, Bethe learned that he had been dismissed from his teaching position at Tubingen. • Sommerfeld invited him back to Munich and worked hard during the summer of 1933 trying to find jobs for various displaced academics. • Bethe realized that it was time to leave Germany and took a temporary lectureship at the University of Manchester for the 1933-34 academic year. • After spending Fall 1934 at the University of Bristol, he accepted a job as an assistant professor at Cornell University in Ithaca, NY. Cornell University has been his home institution ever since! CS-AAPT Meeting Radford University

7. Hans Bethe in Ann Arbor, Michigan (1935) CS-AAPT Meeting Radford University

8. Nuclear Reactions and Sunshine • In 1936-37, Bethe wrote three articles on nuclear physics for the journal Reviews of Modern Physics. These articles were very thorough and extremely valuable to the nuclear physics community – collectively they became known as “Bethe’s Bible.” • In April 1938, Bethe attended a small conference in Washington, DC (organized by George Gamow and Edward Teller) on unsolved problems regarding the internal constitution of stars.This motivated him to carefully examine possible thermonuclear reactions in stars. His 1939 paper “Energy Production in Stars” describes the two basic sets of reactions (the p-p reaction and the CNO cycle) by which hydrogen is converted to helium in the cores of the sun and other stars. He eventually received the Nobel Prize for this work. CS-AAPT Meeting Radford University

9. Marriage and Citizenship • Hans Bethe and Rose Ewald were married at a civil ceremony on September 14, 1939 in New Rochelle, New York. Among those attending were Edward Teller and his wife and the mathematician Richard Courant. Hans and Rose Bethe have two children, a son Henry and a daughter Monica. • Bethe had relatives in Germany and could not be cleared for classified work until after he became a citizen in 1941. He received his security clearance on the “Day of Infamy” --December 7, 1941. CS-AAPT Meeting Radford University

10. War Work • Bethe’s first classified project was microwave radar. He worked at the MIT Radiation Laboratory from early 1942 to March 1943. • During the summer of 1942, Bethe was part of a study group assembled at Berkeley by J. Robert Oppenheimer, who had been appointed to lead the theoretical side of the effort to develop a fission bomb. • By December 1942, Oppenheimer was suggesting to Bethe that he join the bomb-building facility planned for Los Alamos. In April 1943, just as the Los Alamos laboratory was beginning to function, the Bethes relocated to New Mexico. Hans was appointed Chief of the Theoretical Division. He remained at Los Alamos until January 1946. CS-AAPT Meeting Radford University

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12. Post-war: Academic • Bethe returned to Cornell when he left Los Alamos, in spite of a lucrative offer from the University of Rochester. • Bethe, Robert Bacher, and other members of the Cornell physics department persuaded Cornell’s president and board of trustees build a particle accelerator and to establish the Newman Laboratory of Nuclear Studies. Many excellent physicists have trained there as graduate students or postdocs. • Hans Bethe did not stop doing “pure” physics in spite of the many other opportunities and demands. In 1947, he produced the first theoretical calculation of the Lamb shift in hydrogen. Soon thereafter Schwinger at Harvard and Feynman at Cornell produced a general theory of quantum electrodynamics. • As a departmental leader during the McCarthy era, Bethe helped to protect politically liberal faculty members (notably Philip Morrison) from attacks by powerful and zealously anti-Communist benefactors. CS-AAPT Meeting Radford University

13. 1947 Shelter Island conference (Bethe at window on right) CS-AAPT Meeting Radford University

14. Post-war: Consultant and Advisor(partial listing) • Consultant: • Los Alamos Scientific Laboratory, 1947- • Avco Everett Research Lab, 1955-87 • Government advisor: • Member, President’s Science Advisory Committee, 1956-59 • Member, US Delegation to Discussions on Discontinuance of Nuclear Weapons Tests, 1958-59 CS-AAPT Meeting Radford University

15. Presidential Gratitude “You are not only an outstanding scientist, you are also a devoted public servant. “The nation has asked for your help many times and you have responded selflessly. You have made profound contributions in the fields of atomic energy, arms control and military technology. And you have been an important source of the immense contribution which science and the university community are making to society as a whole. “Our country is deeply indebted to you.” --letter from President Lyndon Johnson to Hans Bethe on the occasion of Bethe’s sixtieth birthday (1966) CS-AAPT Meeting Radford University

16. Hans Bethe, lecturer extraordinaire CS-AAPT Meeting Radford University

17. The 1967 Nobel Prize “Professor Bethe, you may have been astonished that among your many contributions to physics, several of which have been proposed for the Nobel Prize, we have chosen one which contains less fundamental physics than many of the others and which has taken only a short part of your long time in science. . . . . . Your solution of the energy source of stars is one of the most important applications of fundamental physics in our days, having led to a deepgoing evolution of our knowledge of the universe around us.” -from the presentation speech of Professor Oskar Klein, member of the Swedish Academy of Sciences CS-AAPT Meeting Radford University

18. Bethe receiving the 1967 Nobel Prize for Physics CS-AAPT Meeting Radford University

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20. An Active Retirement • Bethe became professor emeritus at Cornell University in 1975. He has continued to work at physics, collaborating with John Bahcall on several papers dealing with solar neutrinos. He has also published several papers on models of supernova explosions. • During the 1980’s, he publicly opposed Edward Teller’s ambitious strategic defense proposals (“Star Wars”). In 1992, he called on the US and Russia to reduce their arsenals to a thousand warheads each. In 1996, he wrote an open letter calling on all scientists in all countries to “cease and desist” from work to create, improve, or manufacture nuclear, chemical, and biological weapons. CS-AAPT Meeting Radford University

21. Hans and Rose Bethe with luncheon companion at APS (Atlanta) CS-AAPT Meeting Radford University

22. Bethe at a celebration of his 90th birthday (1996) CS-AAPT Meeting Radford University

23. Sources • Jeremy Bernstein, Prophet of Energy: Hans Bethe (Basic Books, 1980) • Hans A. Bethe, The Road from Los Alamos (AIP, 1991) • Laura Fermi, Illustrious Immigrants (U. of Chicago Press, 1968) • Galison and Hevly (eds.), Big Science (Stanford U. Press, 1992) • Daniel J. Kevles, The Physicists (Harvard U. Press, 1995) • Richard Rhodes, The Making of the Atomic Bomb (Simon & Schuster, 1986) • Richard Rhodes, Dark Sun (Simon & Schuster, 1995) • S. S. Schweber, In the Shadow of the Bomb (Princeton U. Press, 2000) • Various biographical references • Various internet resources, including • the Nobel e-Museum: www.nobel.se • Cornell University: www.cornell.edu • www.phys-astro.sonoma.edu/BruceMedalists/Bethe/BetheRefs.html CS-AAPT Meeting Radford University