what was done in physics today

On this day in 1933, while standing on the sidewalk where Southampton Row joins Russell Square in London, Leó Szilárd conceived the idea of a nuclear chain reaction. The idea made use of neutrons, which James Chadwick had discovered one year earlier, but not nuclear fission, which Otto Hahn, Lise Meitner and Fritz Strassmann would discover five years later. Szilárd proposed that if neutrons could trigger a nuclear reaction that both produced energy and further neutrons, the reaction would be self-sustaining. By 1939 Szilárd and Enrico Fermi had discovered neutron multiplication in uranium. Three years later, they and their collaborators built the world's first artificial self-sustaining nuclear reactor at the University of Chicago.