Enrico Fermi | Biography

Fermi was born in Rome, Italy, on September 29, 1901. He became interested in physics at an early age and taught himself the basics of the subject. His textbook was written in Latin because no Italian-language text was then available.

Fermi entered the University of Pisa at the age of seventeen and received his Ph.D. in 1922. He then traveled to the universities of Göttingen and Leyden for graduate study. In 1924, Fermi accepted a teaching position at the University of Florence. Two years later he became professor of physics at the University of Rome, where he remained until 1938. During his tenure at Rome, Fermi was responsible for revitalizing Italian physics, which had been held in low regard among physicists.

Fermi's interests included many aspects of physical theory. As early as 1926, for example, he developed a theory to explain the behavior of "clouds" of electrons in a substance. The theory is now known as Fermi-Dirac statistical mechanics, acknowledging the independent contributions of Paul Adrien Maurice Dirac on this topic.

In 1933, Fermi turned his attention to a second major problem: beta decay. The problem arises because of differences in the way that alpha particles and beta particle s are emitted from a nucleus. In the former case, all alpha particles leaving a particular nucleus have the same energy. But in beta decay, beta particles may have a range of energies.

Fermi developed a theory to explain this phenomenon. He proposed that the beta particle is produced when a neutron in the nucleus decays to form a proton, an electron (the beta particle), and a chargeless, massless particle called the neutrino. Part of the energy released during this process is carried away by the beta particle and part by the neutrino.

The research for which Fermi is perhaps best known involved neutron bombardment of nuclei. In 1934, Irène Joliot-Curie and Frédéric Joliot-Curie had created the first example of artificial radioactivity by bombarding aluminum with alpha particles. Fermi became interested in extending this research to other elements heavier than aluminum. He recognized a fundamental problem with this type of research, however. The nuclei of heavier elements contain more protons and, therefore, carry large positive charges. Alpha particles face a much stronger force of repulsion than they do with smaller nuclei.

Fermi thought that neutrons would be much more effective in bombarding nuclear targets than are alpha particles. The neutron, discovered by James Chadwick in 1932, carries no electrical charge and experiences, therefore, no repulsive force from the nucleus.

In a very short time, Fermi had bombarded sixty-three elements with neutrons. He found that thirty-seven of these could easily be converted to artificially radioactive isotopes. Most of these decayed by beta emission.

This phenomenon presented an intriguing possibility. When an element decays by beta emission, it changes into a new element one place higher in the periodic table. What would happen, Fermi wondered, if one were to bombard the heaviest known element, uranium, with neutrons. Perhaps an isotope of uranium would be produced that would also decay by beta emission. If so, that isotope would change into element 93, an element that does not exist naturally on earth.

When Fermi actually attempted this experiment, he obtained confusing results. He obtained evidence not only for the new element 93, but also for a number of other products that he was not able to identify. He did not understand that he had not only created the first synthetic element, number 93, but also produced the first nuclear fission reaction.

During this research, Fermi made an additional valuable discovery. He found that neutrons that pass through paraffin or water are more effective at initiating nuclear reactions than are those that do not. The former apparently are slowed down as they interact with paraffin or water molecules and are able to spend more time in the vicinity of target nuclei. For his work on neutron bombardment, Fermi was awarded the Nobel Prize for physics in 1938.

After accepting his prize in Stockholm, Fermi and his family left directly for the United States. Benito Mussolini had come to power in Italy and the first rumblings of World War II could be heard. At least partly because his wife was Jewish, Fermi no longer felt comfortable working in Italy.

Fermi reached the United States at about the time that the discovery of nuclear fission was announced. He realized that excess neutrons released in a fission reaction might be utilized in producing a chain reaction in uranium. First at Columbia University and later at the University of Chicago, Fermi worked out the mathematics and mechanical specifications needed for producing a self-sustaining chain reaction in a block of uranium. As part of the Manhattan Project, he and his colleagues built the first nuclear reactor, or " atomic pile," under the squash courts at the University of Chicago. On December 2, 1942, that reactor first "went critical," that is, initiated a self-sustaining chain reaction. The fundamental reaction on which nuclear weapons are based had been demonstrated.

After the war, Fermi returned to the University of Chicago where he remained for the rest of his life. He was diagnosed with stomach cancer in 1954 and died of the condition on November 28 of that year. His contributions have been recognized in the naming of element number 100, fermium, the naming of the National Accelerator Laboratory at Batavia, Illinois, Fermilab, and the naming of a major scientific award, the Fermi Prize.