unless implosion worked, but only plutonium could be produced in quantities that would allow regular production of atomic bombs. Thus, the implosion technique now suddenly stood as the key to production of nuclear weapons. In mid-June 1944, a report from Kistiakowsky to Oppenheimer detailing dysfunctionality within the implosion team led to the ousting of Neddermeyer. He was replaced as the head of the E-5 Group by Kistiakowsky on June 15, 1944, but remained a technical adviser to the implosion program, with group leader status. Neddermeyer was said to have been much embittered by this episode. In Oppenheimer's August 1944 reorganization of the Los Alamos Laboratory, Neddermeyer's group was renamed X-1, with Norris Bradbury as group leader. The implosion method championed by Neddermeyer was used in the first atom bomb exploded (in the Trinity test), the Fat Man bomb dropped on Nagasaki, and almost all modern nuclear weapons. Kistiakowsky later insisted that "the real invention should be given full credit to [Seth] Neddermeyer" (sic). Later years In 1946, after World War II ended, Neddermeyer left Los Alamos to become an associate professor at the University of Washington, where he would spend the rest of his career. In due course he became a full professor. He resumed his studies of cosmic rays using a cloud chamber and a new device that he invented to measure the speed of charged particles known as a "chronotron". He was particularly interested in the properties of the muon, and conducted experiments with muons at SLAC. He participated in the DUMAND Project, for which he helped design large-scale underwater neutrino detectors. Neddermeyer became interested in parapsychology, insisting, in spite of the skepticism of many colleagues, that it warranted proper scientific investigation. He retired in 1973, becoming a professor emeritus, but he continued his research activities for as long as his health permitted. He was afflicted with Parkinson's disease. In 1982, he was presented with the Department of Energy's Enrico Fermi award. His citation read: In later life, Neddermeyer was sometimes troubled by the nuclear weapons he had helped to invent. He told an interviewer in 1983: Neddermeyer died in Seattle on January 29, 1988, from complications of Parkinson's disease. In popular culture Neddermeyer is portrayed by actor Devon Bostick in the Christopher Nolan-directed film Oppenheimer (2023). Notes References 1907 births 1988 deaths 20th-century American physicists Manhattan Project people Stanford University alumni California Institute of Technology alumni University