The physicist Albert Einstein did not directly participate in the invention of the atomic bomb. However, as part of his Special Theory of Relativity in 1905, he made the intriguing point that a large amount of energy could be released from a small amount of matter. This was expressed by the equation E=mc2 (energy = mass times the speed of light squared). The atomic bomb would clearly illustrate this principle, although bombs were not what Einstein had in mind when he published his equation. In fact, he considered himself to be a pacifist.
Einstein’s position would change in 1933, as the result of Adolf Hitler’s ascent to power in Germany. Einstein’s greatest role in the invention of the atomic bomb was signing a letter to President Franklin Roosevelt urging that the bomb be built. The splitting of the uranium atom in Germany in December 1938 plus continued German aggression led some physicists to fear that Germany might be working on an atomic bomb.
On August 2, 1939, a letter was sent to President Roosevelt with Einstein’s signature on it. Germany had invaded Poland the previous month, and because of the potential for creating a Nazi atomic bomb, Einstein pushed for the development of an atomic bomb for the Allies. Einstein biographer Ronald Clark observed that the atomic bomb would have been eventually invented without Einstein’s letter, but that without the early U.S. work that resulted from his letter, the atomic bombs might not have been ready in time to use during the war on Japan.
Ironically, Einstein later wrote, “I have always condemned the use of the atomic bomb against Japan.” In November 1954, five months before his death, Einstein summarized his feelings about his role in the creation of the atomic bomb: “I made one great mistake in my life… when I signed the letter to President Roosevelt recommending that atom bombs be made; but there was some justification – the danger that the Germans would make them.”(http://www.doug-long.com/einstein.htm)
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