On November 10, 1938, Enrico Fermi was awarded the Nobel Prize in Physics for his "identification of new radioactive elements and his discovery, made in connection with this work, of nuclear reactions effected by slow neutrons." He had previously known of this possibility and had been in contact with American universities about employment possibilities. The Fermi family was given government permission to travel to Stockholm for the Nobel Prize presentation. They did not return to Italy. Instead, after visiting Niels Bohr in Copenhagen, they sailed on December 10 for the United States and Fermi's new professorship at Columbia University.
Meanwhile in Germany, it had been discovered that the neutron bombardment of uranium results in two products of similar atomic weight. The expectation had been one product close to uranium in the Periodic Table plus small disintegration products. The reaction now occurring was more appropriately described as fission, not disintegration.
Fermi began to understand the implications of this news and went on to hypothesize that the splitting of a uranium atom with a neutron results in the release of two neutrons. Each of these neutrons would then split another atom resulting in four neutrons, and so on. This self-perpetuating chain reaction would produce tremendous energy. Its importance was not lost on the scientific community. In an atmosphere of impending war, the possibility of new weapons of unimaginable intensity appeared.
Fermi began to test his hypothesis at Columbia University using the cyclotron there as a neutron generator; within months Fermi's hypothesis was confirmed.
Henry B. Allen Telegram, to Enrico Fermi, Requesting the title of the Medal Day talk for the printed program. (1.5M)
Enrico Fermi Telegram, to Henry B. Allen, Supplying title: "The Future of Nuclear Physics," 3/19/1947. (1.4M)
Enrico Fermi Telegram, to Henry B. Allen, Requesting room reservation information, 4/14/1947. (1.5M)