Radioactive elements were first isolated and studied around 1900. In 1933, Leo Szilard, a Hungarian physicist, was the first to suggest that the chain reaction of radioactive elements could be used to construct a bomb. He left Hungary for Berlin in 1919 and studied at the Institute of Technology under people like Albert Einstein. He got his doctorate in physics in 1923 from Humboldt University of Berlin. He worked as a physicist and inventor in Berlin for the next decade.
On a trip to London in 1933, Szilard read a paper that was critical of the idea that atomic physics could be harness to produce energy. He was so annoyed with the tone of the article that he conceived of the idea of a nuclear chain reaction. If a neutron could trigger a nuclear reaction that produced a neutron, a self-sustaining chain reaction could occur. He returned to Berlin and began research to produce such a chain reaction. In 1036, he filed a patent for his idea with the British Admiralty.
In 1938, Szilard was invited to do research at Columbia University in Manhattan, New York. He was shortly joined by Enrico Fermi who he knew from Berlin. In 1939, a group of researchers in Germany announce that they have achieved nuclear fission with uranium. Szilard and Fermi conducted their own experiments with uranium and were soon able to produce neutrons that multiplied as the reaction progressed, proving that a nuclear chain reaction was possible.
The knowledge the Germans were working on a nuclear chain reaction that could be used to create a devastating weapon was a great concern to Szilard. He drafted a letter to the U.S. President, Franklin D. Roosevelt. He talked Albert Einstein in to cosigning the letter. This was ironic because Einstein was a famous pacifist. The letter outlined the possibility of nuclear weapons, the fact that the Nazis were working on the problem and the need for a nuclear research project in the United States to develop such a weapon. The letter was drafted in August of 1939. In September of 1939, Germany invaded Poland. This invasion is often seen as the start of World War II. The letter was not presented to Roosevelt until October of 1939.
Upon receiving the letter from Szilard and Einstein, Roosevelt created the Advisory Committee on Uranium. The Committee met quickly and authorized six thousand dollars for Fermi to do neutron experiments at the University of Chicago. The Committee did not pursue uranium research vigorously. Other organizations took over control of the research. Meanwhile the Germans were getting close to a controlled chain reactions but they made a mistake in the composition of the graphite rods they were trying to use to absorb neutrons and control the reaction. Szilard realized that the problem was impurities and made graphite rods that were free of the impurities. The new rods worked as expected and in December of 1942, his team produced the first human controlled chain reaction. In 1942, the Manhattan Engineering District took over the program which became known as the Manhattan project and was dedicated to the create of nuclear bombs.
Leo Szilard:
