In 1942, the United States government built a top-secret program called the Manhattan Project. Army engineer, Major General Leslie Groves. The point of this project was to create an atomic bomb before the Germans did. They did not want Adolf Hitler to develop an atomic bomb because they"d fear that he would rule the world.
Leo Szilard and Edward Teller were one of the top physicist and scientists. Szilard was born in Hungary but went to a German University. He then moved to the United States in 1938 along with Edward Teller, also from Hungary. A year later in July, both of these men went to Long Island where Einstein had stayed. These two men had told Einstein that they believe that Germany would be able to make an atomic bomb. They asked Albert Einstein to help them and alert the United States. Then Einstein wrote a letter to President Roosevelt saying that an atomic bomb could be made. .
It had been about two or three months later until Roosevelt had gotten the letter. America's early research had already been organized at New York's Columbia University, therefore it was called the Manhattan Project. This top-secret project was not only being researched in New York but also University of California at Berkley and University of Chicago. In 1942, the Manhattan Project moved its headquarters to Chicago. .
In Chicago, Enrico Fermi built a nuclear reactor the size of a house. Fermi was a Physicist from Italy that won a Nobel Prize for his work in nuclear research. Outside of the nuclear reactor was graphite, which is used in pencil lead. Graphite has the property to deflect speeding neutrons. The inside of the structure had 19,000 balls of uranium. The reaction was to be controlled by neutron absorbing rods that were inserted in holes in the graphite house. .
One of Fermi's technicians was to pull out one of the rods, to test the reaction of the structure. The farther the rod was pulled out, the louder the clicking noise got.