Four years earlier the Italian scientist received the Nobel Prize for Physics. Planning to defect, Fermi attended the award ceremonies in Stockholm with his wife and children. Like so many intellectuals who left fascist Europe, Fermi came to the United States and worked at Columbia University.
At a physics conference in the U.S., Nobel Prize wining physicist Niels Bohr told Fermi about the findings of Lise Meitner and her nephew Otto Frisch. Meitner worked in Germany with physicists Otto Hahn and Fritz Strassmann until fleeing to Sweden to escape Nazi persecution. From her work in Germany, Meitner knew the nucleus of uranium-235 splits (fission) into two lighter nuclei when bombarded by a neutron. Interestingly, the sum of the particles derived from fission are not equal in mass to the original nucleus. During a visit with her nephew, Meitner speculated that release of energy--energy a hundred million times greater than normally released in the chemical reaction between two atoms--accounted for the difference. Returning to his lab, Frisch explained the theory to Bohr.
Within days, Fermi and exiled Hungarian physicist Leo Szilard, realized the first split or fission could cause a second, and so on in a series of chain reactions expanding in geometric progression. They agreed not to publish their findings, lest Germany use them to produce a super weapon. Instead, Szilard and émigré Eugene Wigner persuaded Albert Einstein to write President Franklin D. Roosevelt and request atomic research receive high priority.
Preparing the nation for war, Roosevelt agreed. In December 1941, as the U.S. entered World War II, the project moved to Chicago where Fermi, Walter Zinn, Herbert Anderson, Arthur Compton, and Leo Szilard were the principal team members. Within four years, the Manhattan Project, supervised by J. Robert Oppenheimer, Compton, and Fermi, developed the atomic bomb.
