Otto Frisch

Otto Frisch was an Austrian-born physicist who, working with his aunt Lise Meitner in late 1938, developed the theoretical explanation for a puzzling experimental result reported by Otto Hahn and Fritz Strassmann in Berlin, that bombarding uranium with neutrons appeared to split the nucleus into much lighter elements. Frisch and Meitner worked out that the uranium nucleus was genuinely splitting into two roughly equal fragments, releasing a very large amount of energy in the process, and Frisch coined the term fission, borrowing the word from biology, to describe this newly understood nuclear process. After emigrating to Britain, Frisch worked in 1940 with fellow refugee physicist Rudolf Peierls on a short but highly consequential report, the Frisch-Peierls memorandum, which calculated that a chain-reacting bomb using a relatively small amount of purified uranium-235 was physically feasible, a conclusion that helped launch the British Maud Committee and, through it, the American Manhattan Project. Frisch himself went on to work at Los Alamos during the war as head of the Critical Assemblies group, carrying out experiments to determine the critical mass needed to sustain a nuclear chain reaction, before returning to Britain after the war to continue a career in nuclear physics.