Leo Szilard

Leo Szilard was a Hungarian-American physicist and inventor who conceived the nuclear chain reaction and helped initiate the Manhattan Project.

Albert Einstein: Albert Einstein was a German-born theoretical physicist who developed the theory of relativity. Szilard persuaded Einstein to co-sign a 1939 letter warning Franklin Roosevelt about uranium weapons.
Nuclear chain reaction: A sequence in which reactions produce particles that trigger further reactions. Szilard conceived how neutrons from one fission could sustain successive fissions.
Manhattan Project: The U.S.-led wartime program that developed the first atomic bombs. Szilard’s 1939 warning and subsequent lobbying helped bring the project into existence.
Budapest: The capital of Hungary and Szilard’s birthplace. Szilard was born and educated in Budapest before leaving Hungary for Germany.
Scientists' responsibility: The ethical and civic obligations scientists face for the foreseeable uses of their work. Szilard moved from urging bomb development to campaigning against its use and proliferation.
Enrico Fermi: Enrico Fermi was an Italian-born physicist who led the first controlled nuclear chain reaction. Szilard worked with Fermi to design the graphite-moderated reactor that achieved the first sustained chain reaction.
Nuclear fission: The splitting of an atomic nucleus into lighter nuclei, often releasing neutrons and energy. Fission supplies the neutrons and energy needed for the chain reaction Szilard proposed.
Einstein–Szilard letter: A 1939 letter to President Franklin D. Roosevelt warning that Nazi Germany might develop uranium weapons. Szilard drafted the letter and arranged for Einstein to sign it.
University of Berlin: A German university founded in 1810, now known as Humboldt University of Berlin. Szilard studied physics there and worked with leading physicists before fleeing Nazi Germany.
Atomic bombings of Hiroshima and Nagasaki: The U.S. atomic attacks on Hiroshima and Nagasaki in August 1945, which killed tens of thousands immediately. Szilard opposed using the bomb against Japan without first demonstrating its destructive power.

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History of nuclear weaponsRelated: His 1939 letter to Franklin Roosevelt helped prompt American research into an atomic bomb.