Leo Szilard

CODEX Entry 5801: Leo Szilard


A Jew, born in Hungary in 1898. He was the first to theorize correctly the nuclear chain reaction in 1933, and patented the idea of a nuclear fission reactor in 1934. In 1939, after the war had started, he wrote the letter for Albert Einstein’s signature that resulted in the Manhattan Project, to build the first atomic bomb. Leo Szilard was one of the Hungarian scientists known as The Martians. He wrote his doctoral thesis on Maxwell’s demon, a long-standing puzzle in the philosophy of thermal and statistical physics, and was the first to recognize the connection between thermodynamics and information theory. Szilard also patented the electron microscope, the linear accelerator, and the cyclotron. He worked with Einstein on the development of the Einstein refrigerator. After Adolf Hitler became chancellor of Germany in 1933, Szilard moved to England, where he discovered a means of isotope separation. Foreseeing another war in Europe, Szilard moved to the United States in 1938, where he worked on creating a nuclear chain reaction, which was achieved at the Chicago Pile-1 on December 2, 1942. He worked for the Manhattan Project on the nuclear reactor design.

After the war, Szilard switched to biology. He invented the chemostat, discovered feedback inhibition, and was involved in the first cloning of a human cell. He publicly sounded the alarm against the possible development of salted thermonuclear bombs, a new kind of nuclear weapon that might annihilate mankind. Diagnosed with bladder cancer in 1960, he underwent a cobalt-60 treatment that he had designed, and died in his sleep of a heart attack 4 years later.