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Szilard and Fermi can’t agree on whether to keep the uranium discoveries secret. Szilard fears the Germans will get wind of it and start a program to develop a bomb; Fermi believes the chance of success is only 10%, and it’s less suspicious to downplay the possibility than try to hide it. Uranium with an atomic weight of 238 is common; less than one percent of uranium has an atomic weight of 235. U238 will fission only after being struck by a high-energy neutron, but the U235 isotope will fission after accepting a neutron of any energy. Bohr realizes that U-235 is much more likely to form a chain reaction.
At Columbia, Szilard, Fermi, and Walter Zinn run a test that proves U235 emits twice as many neutrons during fission as it receives. A chain reaction is doable: “That night,” says Szilard, “there was very little doubt in my mind that the world was headed for grief” (292). Szilard and Fermi now support a military program to develop an atomic bomb, kept secret from the Germans, but Bohr thinks separating enough U235 will be nearly impossible, and he doesn’t want the openness of Plus, gain access to 8,650+ more expert-written Study Guides. Including features: