The Atomic Age: Far More Than Explosions and Electricity

Scientists witness the first nuclear fission chain reaction. (Credit: John Cadel/Chicago History Museum) Seventy-five years ago, the world officially entered the Atomic Age. Henceforth, it would never be the same. In October 1942, as part of the Manhattan Project, Enrico Fermi assembled a crack team of physicists for an urgent, top-secret government mission: Conduct the first man-made, self-sustaining nuclear chain reaction to prove it was indeed possible to build an atomic weapon—and do it before the Germans. For months, Fermi’s team toiled away on a squash court tucked beneath the western grandstand of Stagg Field at the University of Chicago. The team milled 45,000 graphite bricks and shaped uranium oxide powder into 22,000 baseball-sized spheres. They took those graphite bricks and stacked them—with the help of broad-shouldered football players and laborers—into a 57-layer pile, positioning the uranium oxide balls in the middle, and wrapping the whole thing in wood. This is how they hoped it would work: Free neutrons, produced by the decay of uranium, would be absorbed by other uranium atoms and kick-start a self-sustaining fission reaction. In all, the Chicago Pile-1 (CP-1) contained 400 tons of graphite, 6 tons of uranium metal and 45 tons of uranium oxide. Fermi would later describe the reactor as “a crude pile of black bricks and wooden timber.”