Einstein signed the letter that warned of an atomic bomb
On this day · 2 August 1939
A two-page letter, signed by the world's most famous physicist, nudged a president toward the nuclear age.
On August 2, 1939, Albert Einstein signed a letter to U.S. President Franklin D. Roosevelt warning that recent physics had made a terrifying weapon thinkable. Drafted largely by the Hungarian physicist Leo Szilard, with help from Eugene Wigner and Edward Teller, it cautioned that uranium could be turned into “extremely powerful bombs of a new type.”
The letter urged the United States to secure uranium supplies and fund research, noting that Germany had already moved to control ore from occupied Czechoslovakia.
“This new phenomenon would also lead to the construction of bombs.”
Roosevelt judged the warning serious enough to act, creating the Advisory Committee on Uranium, which first met that October. That modest body set in motion the chain of decisions that grew into the Manhattan Project. Einstein, a lifelong pacifist, later called lending his name to the letter the one great mistake of his life.
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