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The creation of a nuclear physics laboratory at Cornell

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Hans Bethe Scientist
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The reason for testing it at that date was that only then was [there] enough material available to serve for one test and have another equal amount of material available to actually use in the war against Japan. The test worked beyond all expectations. I had calculated, or rather Serber had calculated, it would give 8 kilotons of energy. But one of Serber's young men had calculated it might give 20. And, of course, I believed the authority, I believed Serber, so I said it would give 8 kilotons, and it gave 20. So it was successful beyond all belief. And thereby established the Plutonium Nuclear Weapon. It was then... a duplicate of that, that was then dropped on Nagasaki a little later.

[Q] The... so you were at Los Alamos essentially till the end of '45.

I was there to the end of '45, the end of the war was about one September, '45, so this was after the war. We were, however, now working on further improvements of the nuclear weapon. It was obvious that it would be more efficient to go back to our original design, namely have a shell of plutonium inside natural uranium and then implode that. And it would, at the same time, it became obvious that plutonium was more expensive to produce than uranium-235, so we were interested in a combined weapon with plutonium in the center and 235 around it, and then natural uranium around that. So this is what we worked on in the later months of 1945. I had got another group leader by then, namely Placzek, who... who had been my friend before. He had been in a project in Canada and brought with him a Canadian physicist, Carson Mark, who, after a while, became Placzek's successor as group leader and then my successor as leader of the Theoretical Division.

The late German-American physicist Hans Bethe once described himself as the H-bomb's midwife. He left Nazi Germany in 1933, after which he helped develop the first atomic bomb, won the Nobel Prize in Physics in 1967 for his contribution to the theory of nuclear reactions, advocated tighter controls over nuclear weapons and campaigned vigorously for the peaceful use of nuclear energy.

Listeners: Sam Schweber

Silvan Sam Schweber is the Koret Professor of the History of Ideas and Professor of Physics at Brandeis University, and a Faculty Associate in the Department of the History of Science at Harvard University. He is the author of a history of the development of quantum electro mechanics, "QED and the men who made it", and has recently completed a biography of Hans Bethe and the history of nuclear weapons development, "In the Shadow of the Bomb: Oppenheimer, Bethe, and the Moral Responsibility of the Scientist" (Princeton University Press, 2000).

Tags: Japan, WWII, Nagasaki, Los Alamos, 1945, Robert Serber, George Placzek, J Carson Mark

Duration: 3 minutes, 42 seconds

Date story recorded: December 1996

Date story went live: 24 January 2008