His great accomplishment ushered in the modern nuclear age—giving humankind the ability to release the energy within the atomic nucleus in a controlled manner and to produce a wide variety of important new radioactive isotopes. Fermi was born on September 29, 1901, in Rome, Italy. The son of a railroad official, he studied at the University of Pisa from 1918 to 1922. After receiving his Ph.D. in physics in 1922, Fermi conducted postdoctoral studies at the universities of Leyden and Göttingen. In 1926, he discovered the statistical laws, now referred to as Fermi-Dirac statistics, that govern the behavior of particles subject to the Pauli exclusion principle.
In 1927, Fermi became professor of theoretical physics at the University of Rome; he retained that position until 1938. He made significant contributions to both theoretical and experimental physics—a unique feat in an age when scientific endeavors tend to emphasize one or the other. Between 1933 and 1934, he developed the theory of beta decay, combining previous work on radiation theory with Wolfgang Pauli’s idea of the neutrino. Fermi postulated that during beta decay a neutron was transforming into a proton and an electron (beta-minus particle). Also released in beta decay was a tiny subatomic particle, the neutrino (from the Italian for “tiny neutral”), as previously suggested by Pauli. The theory developed to explain this decay reaction later resulted in recognition of the weak nuclear force.
During the early 1930s, Fermi and his colleagues at the University of Rome used a variety of interesting experiments to investigate the characteristics and behavior of neutrons. Following the discovery of artificiall induced radioactivity by Frédérick and Irène Joliot-Curie in 1934, Fermi’s team in Rome used neutrons to bombard most of the known elements. Fermi soon demonstrated that nuclear transmutations took place in almost every element bombarded. Not only did he produce many new radioactive isotopes with his neutron bombardment experiments, but he also made the very important discovery in 1934 that slow neutrons exist and greatly improve the rate of neutron-target nucleus interaction. The slow neutron was the key to the discovery of nuclear fission and the production of new elements beyond uranium in the periodic table. After four years of such intense experimentation, Fermi became the world’s expert on the neutron and how it interacted with matter.
However, by 1938, life in fascist Italy had become intolerable for Fermi. When the Italian government headed by Benito Mussolini instituted anti-Semitic laws, Fermi feared the worst for his Jewish wife, Laura, and their two children. He used the opportunity provided by his trip to Stockholm to accept his 1938 Nobel Prize in physics, awarded for his “demonstrations of the existence of new radioactive element produced by neutron irradiation and for his discovery of nuclear reactions caused by slow neutrons,” to flee.
Mussolini had ordered Fermi to give the fascist salute when he received his award from the Swedish king. When the time for the presentation came, the gentle physicist simply bowed in respect before the king, like the other recipients that day. In further defiance of fascism, he took his wife and children and fled by ship to the United States, where a professorship in physics awaited him at Columbia University in New York.
By the time Fermi and his family settled in New York, word reached him from Europe that the German scientists Otto Hahn (1879–1968) and Fritz Strassmann (1902–1980) had achieved nuclear fission in their laboratory in Berlin. Other refugee scientists quickly approached Fermi to express their growing concerns that Nazi Germany might be able to use this reaction to construct a superweapon.
Fermi immediately recognized the potential of fission and linked it to the possibility of the emission of secondary neutrons and a chain reaction. He encouraged the Hungarian-American physicist Leo Szilard (1898–1964) to meet with Albert Einstein (1879–1955) and send a letter of concern to President Franklin Roosevelt. Fermi then proceeded to work with tremendous enthusiasm on constructing the world’s first nuclear reactor (then called an “atomic pile”). He performed a series of important preliminary experiments at Columbia University and then relocated to the University of Chicago to work with Arthur Holly Compton’s (1892–1962) group during the Manhattan Project.
Fermi’s work at the University of Chicago was the first critical step in the production of a U.S. atomic bomb. Working tirelessly day and night, often covered with black graphite dust, he supervised the design and assembly of Chicago Pile One (CP-1)—the world’s first self-sustaining fission chain reaction. The momentous event took place on December 2, 1942, in the squash courts under the west stand of the university’s Stagg Field. Through Fermi and his dedicated team, the modern nuclear age was born in unassuming surroundings. From that moment on, humankind could control the release of energy from within the atomic nucleus.
Ernest Orlando Lawrance (1901 – 1958)
