Corbin Allardice and Edward R. Trapnell

In 1942, a group of scientists headed by Enrico Fermi and Arthur Compton was building an atomic pile that they hoped would become the first nuclear reactor. This reactor consisted of a stack, or pile, of graphite blocks with lumps of uranium spaced throughout. The graphite served to slow down the neutrons emitted by the uranium so that they would be absorbed by the next lump of uranium and cause it to fission. It was hoped that this process would continue until the overall reaction became continuous and self-sustaining.

The atomic pile was built under the squash courts in the stadium of the University of Chicago. Movable rods of cadmium were inserted into the pile. These rods could absorb the uranium emissions and could speed up or shut down the reaction. By December 1, everything was ready for...