Physicist Leo Szilard, the scientist who conceived of a nuclear chain reaction, worked on the Manhattan Project when he moved to the United States. *

Photo: Corbis * 1933: Physicist Leo Szilard gets the nuclear age rolling, so to speak, by conceiving the idea of a nuclear chain reaction while standing at a red light.

Szilard, a native of Budapest and a soldier in the Austro-Hungarian army during World War I, left Hungary for Germany to escape the postwar rise of anti-Semitism. Originally an engineering student, he switched to physics after moving to Berlin and studied under Albert Einstein, among others.

His decade in Berlin was fruitful and Slizard was engaged in a number of projects, including development of the linear accelerator, cyclotron and home refrigeration. But with the rise of the Nazis, Slizard found himself on the move again, this time to London.

Not long after his arrival, Slizard read an article in the Times of London rejecting the idea of any practical use for atomic energy. So incensed was Slizard, the story goes, that he stood right there at a traffic signal in Bloomsbury and dreamed up the nuclear chain reaction. A year later he patented the concept.

His early attempts at triggering a reaction, however, failed. He tried using beryllium and indium to no effect and, in 1936, he assigned his chain-reaction patent to the British Admiralty to ensure secrecy. Soon thereafter, Slizard accepted a teaching post at Columbia University in New York, and moved to the United States.

There, he met Enrico Fermi and, reacting to the discovery of nuclear fission in a Berlin laboratory, the two men realized uranium was the agent they needed to produce their reaction. Working at the University of Chicago, they produced the world's first controlled nuclear chain reaction in December 1942.

Both men worked on the Manhattan Project, which developed an atomic bomb for the United States. Slizard agreed to join the project partly out of the belief that the Americans represented the one true moral force in the world. The bombings of Hiroshima and Nagasaki convinced him otherwise, however, especially as he had been a leading "scientist of conscience," an advocate of demonstrating the power of the bomb to the Japanese in some way other than obliterating two population centers.

Following the war, Slizard, remaining true to his belief that scientists are morally responsible for the consequences of their work, switched disciplines, moving to molecular biology. He died in 1964, at the age of 66.

(Source: Various)

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