WILLIAM A. FOWLER (1911-1995) INTERVIEWED BY JOHN GREENBERG & CAROL BUGÉ May 3, 1983 – May 31, 1984, October 3, 1986 ARCHIVES CALIFORNIA INSTITUTE OF TECHNOLOGY Pasadena, California Subject area Astrophysics, nuclear physics, physics Abstract Interview conducted in eight sessions between May 1983 and May 1984 with Willy Fowler, Nobel laureate and Institute Professor of Physics, emeritus. In a career in nuclear physics and nuclear astrophysics that spanned more that sixty years, Fowler was primarily concerned with nucleosynthesis—that is, the creation of the heavy elements by the fusion of the nuclei of lighter elements. In 1957, with Fred Hoyle and Geoffrey and Margaret Burbidge, Fowler coauthored the seminal paper “Synthesis of the Elements in the Stars,” now known as B2FH. In it, they showed that all the elements from carbon to uranium could be produced by nuclear processes in stars starting only with the light elements produced in the Big Bang. In the interview, Fowler discusses his early education as a physicist at Ohio State; his work with Charles C. and Tommy Lauritsen at Caltech’s Kellogg Radiation Laboratory; the history of nuclear physics and nuclear astrophysics at Caltech; and the evolution of nucleosynthesis. There are recollections of many of his mentors and colleagues, including Robert A. Millikan, Hans Bethe, J. Robert Oppenheimer, the Lauritsens, Fred Hoyle, the Burbidges, Jesse Greenstein, A. G. W. Cameron, Richard P. Feynman, and H. P. Robertson. A 1986 Supplement contains http://resolver.caltech.edu/CaltechOH:OH_Fowler_W an interview on Fowler’s work for the Naval Bureau of Ordnance and the Manhattan Project during the Second World War. Administrative information Access The interview is unrestricted. Copyright Copyright has been assigned to the California Institute of Technology © 1986, 1987, 2005. All requests for permission to publish or quote from the transcript must be submitted in writing to the University Archivist. Preferred citation Fowler, William. Interview by John Greenberg and Carol Bugé. Pasadena, California, May 3, 1983-May 31, 1984; October 3, 1986. Oral History Project, California Institute of Technology Archives. Retrieved [supply date of retrieval] from the World Wide Web: http://resolver.caltech.edu/CaltechOH:OH_Fowler_W Contact information Archives, California Institute of Technology Mail Code 015A-74 Pasadena, CA 91125 Phone: (626) 395-2704 Fax: (626) 793-8756 Email: [email protected] Graphics and content © 2005 California Institute of Technology. http://resolver.caltech.edu/CaltechOH:OH_Fowler_W (Above) Willy Fowler celebrates the news of his Nobel Prize (physics, 1983) with well- wishers at Caltech. Photo by Robert Paz. (Below) Willy Fowler lands a prize-winning seat at the Nobel banquet next to Sweden’s Queen Sylvia (December 1983). Svenskt Press Photo. http://resolver.caltech.edu/CaltechOH:OH_Fowler_W CALIFORNIA INSTITUTE OF TECHNOLOGY ORAL HISTORY PROJECT INTERVIEW WITH WILLIAM A. FOWLER BY JOHN GREENBERG SUPPLEMENT BY CAROL BUGÉ Caltech Archives, 1986, 1987 Copyright © 1986, 1987, 2005 by the California Institute of Technology http://resolver.caltech.edu/CaltechOH:OH_Fowler_W Fowler–ii TABLE OF CONTENTS INTERVIEW WITH WILLIAM A. FOWLER Session 1 1-22 Interest in science begins at Lima, Ohio, high school; high regard for Caltech and R. A. Millikan; lack of scholarship aid; enrolls at Ohio State (1929); switches to new engineering physics program; work in advanced laboratories; seminars on nuclear physics including C. Anderson’s discovery of positron, Cockcroft and Walton’s work on disintegration of nuclei; 1933 graduate assistantship at Caltech; engineering backgrounds of Caltech physicists; book on photoelectric phenomena by L. DuBridge and A. L. Hughes. Graduate life at Caltech; assignment to Kellogg Radiation Laboratory under C. C. Lauritsen; nuclear physics burgeoning; H. R. Crane and Lauritsen’s first papers; Millikan’s visits to lab; bombardment of light nuclei with accelerated particles; recollections of Millikan; graduate courses and influential teachers; F. Zwicky’s Socratic method; friendship with W. Houston; J. R. Oppenheimer and Kellogg Lab; financial situation as graduate student; social diversions; Lauritsen’s seminars on radioactivity. Session 2 23-42 Lauritsen shares R. Sorensen’s High Potential Research Laboratory in Kellogg, designs and builds high-voltage X-ray tubes; W. A. F. and L. Delsasso work at night taking cloud chamber pictures. By 1940, Lauritsen’s million-volt X-ray tube for cancer research converted to positive ion accelerator for nuclear physics experiments; Lauritsen and English researcher J. Read demonstrate correctness of Klein-Nishina formula for scattering and absorption of X rays and gamma rays; cloud chamber at Kellogg used to measure energy of gamma radiation from nuclear reactions. Graduate student A. Tollestrup’s introduction of scintillation counters; development of Lauritsen electroscope, cloud chambers, lab equipment in 1930s; Lauritsen’s skill as designer, expertise in fine shop work. Kellogg group’s race for publications with Berkeley Radiation Laboratory and Dept. of Terrestrial Magnetism at Washington; E. O. Lawrence’s cyclotron vs. Van de Graaff electrostatic accelerators; the prewar Pasadena-Berkeley-Washington axis in nuclear physics supplemented by new centers; W. A. F. thesis on the production of radioactive elements of low atomic number, conclusion that nuclear forces were charge symmetrical; improvement of cloud chamber resolution. Session 3 43-64 Papers on gamma rays by Crane, Delsasso, Fowler, and Lauritsen (1934-38); overcoming uncertainties in gamma ray lines; Lauritsen and Crane’s discovery of resonance effect in bombarding carbon-12 with protons; Dept. of Terrestrial Magnetism physicists’ initial skepticism; E. Fermi’s bombardment of nuclei with neutrons; W. A. F. and T. Lauritsen build http://resolver.caltech.edu/CaltechOH:OH_Fowler_W Fowler–iii Van de Graaff accelerator on R. Herb model (1938-40); Berkeley as nuclear physics capital; studies on proton-proton scattering; N. Bohr’s concept of a compound many-bodied nucleus, explaining sharp resonances. Kellogg Lab’s experimental approach to search for basic nuclear forces contrasted with present-day application of theoretical knowledge to predict nuclear properties and energies; importance in 1930s of H. Yukawa’s discovery of behavior of short-range forces; Anderson and S. Neddermeyer’s discovery of muon; Lawrence prods Millikan to take Caltech into high-energy research; Kellogg group’s postwar commitment to low-energy field; Lauritsen recommends Caltech undertake high-energy work on appropriate scale; R. Langmuir arrives to build synchrotron, followed by R. Bacher and R. Walker; Lauritsen’s involvement in national science (late l940s); W. A. F.’s interest in solar nuclear reactions; offers from other labs (1938); values collaboration with Lauritsens; C. C. Lauritsen the experimentalist’s experimentalist. Oppenheimer at Kellogg; his grasp of quantum mechanics and relativity; explains significance of reactions in excited-state nuclei; Caltech’s role in mirror nuclei, resonance in proton capture, overlooked in nuclear physics literature; rivalry among theorists; less exchange between Caltech physics groups than now; W. Elsasser’s attempts to apply shell model, useful only for low-energy nuclei; Oppenheimer’s scorn for Houston’s nuclear model with springs. Session 4 65-79 Corrects record on Kellogg Lab’s early role in nuclear physics; review of papers; Lauritsen and Crane’s discovery of resonance effects in nuclear reaction yields with AC-powered accelerator; argument at 1934 Physical Society meeting; M. Tuve concedes Lauritsen’s results; G. Breit and F. Yost’s corrected model; Oppenheimer’s reluctance to believe evidence on resonance from radiative capture; Breit-Wigner 1936 formula a numerical expression of resonance effect; H. Bethe and M. S. Livingston’s 1937 report on nuclear physics; earlier detection of resonances with alpha particles (1929). Session 5 80-99 Concluding record on radiative capture and resonances; B. Cassen’s letters to Lauritsen (1930-31) on early model of Van de Graaff accelerator; Fowler and Lauritsens’ 1940 paper summarizing work on new pressurized accelerator; carbon and nitrogen isotopes’ interaction with protons; serious experimentation on CN cycle at Kellogg deferred until postwar lab rebuilt; experiments meanwhile (1946-49) on new problems raised by Bohr and Fermi. T. W. Bonner and W. M. Brubaker’s prewar work at Kellogg on nuclear reactions producing neutrons, same time as Fowler-T. Lauritsen experiments with reactions producing gamma rays; H. Staub and W. E. Stephens (and independently J. Williams at Minnesota) show no stable nucleus at mass 5, obstacle to G. Gamow’s later theory of origin of the elements; distinction between electron-positron pairs produced by gamma rays and pairs emitted from nuclei; Oppenheimer and J. Schwinger’s theoretical explanation (1939); W. A. F.’s eagerness to tackle complex nuclear states, test predictions of spin and parity, discover relation between Bohr model and shell model. Friendship with H. P. Robertsons; interplay between physicists and pure mathematicians at http://resolver.caltech.edu/CaltechOH:OH_Fowler_W Fowler–iv Caltech, late 1930s; M. Ward’s and A. Michal’s interest in applications of mathematics to physics; separation of two fields in 1950s; R. Feynman’s influence as theorist; individual mathematicians helpful over the years; high activity in other fields at Caltech in 1930s. Oppenheimer