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© Copyright 1998, Jim Loy
Near the beginning of World War II, Otto Hahn, a German chemist, discovered the fission (splitting) of the uranium atom, by bombarding uranium with neutrons. He published his findings in Jan., 1939. Soon, many physicists became aware of the possibility of a nuclear chain reaction. This thought led to the idea of an atomic bomb. Leo Szilard, a Hungarian physicist who had moved to the United States, sent letters to scientists around the world, asking them to not publish their experiments on uranium fission. The fear was that Hitler would get the atomic bomb before the allies did. That fear resulted in the Manhattan Project, which produced the atomic bomb. The allies were in a race against Germany, to produce the bomb.
Hahn's experiment involved bombarding uranium with thermal neutrons. These were slow-moving neutrons, moving at speeds that heat could produce with atoms, thermal speeds. He then analyzed the resulting substances, to determine what had happened to the uranium. Physicists showed that neutrons were produced by this process. This is what suggested a chain reaction, neutrons in, neutrons out. The resulting neutrons were fast neutrons. They zipped right through the uranium, and blasted a few atoms to pieces. But, there was no chain reaction. The chain reaction needed slow neutrons.
A slow neutron is absorbed into the uranium nucleus. This makes the nucleus very unstable, more unstable than it was originally. The nucleus splits into two pieces, and gives off several fast neutrons. Physicists then tried to slow these fast neutrons down. Enrico Fermi, an Italian physicist who had moved to the U.S., created the first sustained nuclear reaction, showing that a bomb was possible. He used graphite to slow down the neutrons.
The U.S. went on to build a few bombs. And they blew up two Japanese cities, Hiroshima on Aug. 6, 1945, and Nagasaki on Aug. 9, in order to encourage Japan to surrender. This made WWII our first, and only, nuclear war.
So, what happened to the Germans? To the surprise of the allies, the Germans never got close to producing a bomb. Werner Heisenberg, a very respected physicist, led Hitler's atomic bomb project. Apparently, Hitler was sure that the war would not last long. And, this atomic bomb was going to take many years to produce, if it could be done at all. And so, the project was not supported.
Addendum:
It is well known that the Germans were interested in heavy water. This is water in which one of the atoms of hydrogen is actually deuterium, heavy hydrogen with one proton and one neutron in the nucleus instead of just one proton. This is evidence that they were conducting nuclear experiments, or is it? What does it have to do with the atomic bomb? Well it turns out that heavy water does a good job of slowing neutrons. So, it may indeed have been used for atomic bomb research.