Enrico Fermi
Fermi, Enrico (1901-1954) was an Italian-born American physicist who made fundamental contributions to nuclear physics. He was the first scientist to split the atom, although he did not realize at the time that he had done so. He designed the first atomic pile, or nuclear reactor, and produced the first nuclear chain reaction in 1942. This event led to the successful testing of the first atomic weapon. He won the 1938 Nobel Prize in physics.
Fermi was born in Italy in 1901. When Fermi was 13 years old, Adolfo Amidei, a family friend and engineer, recognized the teen's aptitude for mathematics and physics. Amidei guided Fermi's studies. Fermi progressed rapidly. He received his Ph.D. degree magna cum laude in 1922 from the University of Pisa. He was 21 years old at the time.
Fermi taught mathematical physics and mechanics at the University of Florence and then theoretical physics at the University of Rome, where he served as chair of theoretical physics. In 1928 he married Laura Capon. The couple had two children.
The years between 1926 and 1938 were very productive for Fermi. He and a group of students and collaborators—including Edoardo Amaldi, Oscar D'Agostino, Emilio Gino Segré, and Franco Rasetti—published nearly 100 scientific papers during this time.
Around 1927, Fermi developed a statistical model of the atom, which is now known as the Thomas-Fermi model. He developed a theory known as Fermi-Dirac statistics; which is a method of analyzing a system of indistinguishable particles to determine the probability of the energy distribution. And, most important, he constructed a theory of nuclear beta decay, in which a neutron changes to a proton and emits an electron and a particle called a neutrino.
In 1934, the French physicists Frédéric Joliot-Curie and Irène Joliot-Curie produced artificial radioactivity by bombarding elements with alpha particles. Fermi wanted to build on this experimental work. He used slowed-down neutrons to bombard most of the elements in the periodic table. This proved a very effective method to release radioactive particles from the bombarded material. When Fermi used uranium (atomic weight 92) as the target, however, he obtained unexpected radioactive substances. Fermi's co-workers thought the new substances might be a new element of atomic weight 93. In 1934, he announced what he thought were elements lying beyond uranium, not realizing that what he had done in his experiment was actually split the atom. A few years later, Otto Hahn and Fritz Strassman of Germany performed a similar experiment. Lise Meitner and Otto Frisch showed that the uranium atom had been split, a process called nuclear fission. Scientists soon realized that if many uranium nuclei could be made to fission, a tremendous amount of energy would be released. This energy could be used to make a powerful bomb as well as for other applications, such as producing electric energy.
In 1938, Fermi won the Nobel Prize in physics for “his discovery of new radioactive elements produced by neutron irradiation, and for the discovery of nuclear reactions brought about by slow neutrons.” He and his family went to Stockholm, Sweden, where he accepted the award. The Fermis then immigrated to the United States to escape Italy's Fascist regime. Fermi became a professor of physics at Columbia University in 1939.
In New York, Fermi heard about the conclusions that Hahn, Strassmann, Meitner, and Frisch had reached. The experiments were repeated at Columbia University with similar results and conclusions, suggesting the possibility of a nuclear chain reaction.
Meanwhile, Fermi and two other scientists, Leo Szilard and Eugene Paul Wigner, became concerned about the possibility that scientists in Nazi Germany might achieve a chain reaction and develop an atomic weapon. World War II (1939-1945) had begun in September 1939, when Germany invaded Poland. The group of scientists drafted a letter to President Franklin Delano Roosevelt expressing their concerns about Adolf Hitler using atomic weapons should they become available. Albert Einstein signed the letter and presented it to the president. Out of this event developed the Manhattan Project, code name for a top-secret scientific team assembled in 1942 to develop an atomic bomb for the United States.
Fermi was asked to direct the construction of the first atomic pile. He and other key scientists, including Szilard and Wigner began work at the University of Chicago in the spring of 1942. Under the scientists' direction, workers built an atomic pile, or reactor, beneath the stands of the university's athletic field. On Dec. 2, 1942, this reactor produced the first artificial chain reaction. This reaction lasted 28 minutes and produced 200 watts.
In September 1944, Fermi moved to Los Alamos, New Mexico, to assist in the final stages of constructing an atomic bomb. The bomb was exploded as a test in the desert near Alamagordo, New Mexico, in July 1945. Fermi was present at the test, conducting a very simple test to determine the explosive power by dropping small bits of paper. (He compared the displacement of the papers at the time of the blast with the displacement earlier when the air had been still.) The next month, the United States dropped two atomic bombs on Japan, which contributed to Japan's surrender and the end of World War II.
Fermi became a U.S. citizen in 1944. In 1946, he returned to the University of Chicago as the Charles H. Swift Distinguished Service Professor in Physics and a member of the university's newly established Institute for Nuclear Studies (now named the Enrico Fermi Institute). The topics of Fermi's theoretical and experimental research during his tenure at the University of Chicago included nuclear and neutron physics, cosmic-ray physics, and particle physics. He influenced the development of the synchrocyclotron at the university. At the time of its completion, this machine was one of the most powerful cyclotrons in the world. Fermi used the synchrocyclotron in his research into the means by which the nucleus is held together in a stable configuration.
After World War II, Fermi and other scientists argued against the United States development of a hydrogen bomb when that project was debated. Their advice was ignored, and the United States exploded the first hydrogen bomb in 1952 and so achieved the world's first large-scale thermonuclear reaction.
In 1954, Fermi was diagnosed with stomach cancer, and he died that same year. During his lifetime he was made a member of several academies and learned societies in Italy and abroad, including the Royal Academy of Italy and the National Academy of Sciences (United States). He received honorary doctorates from several institutions, including Harvard and Yale universities.
After his death, the Enrico Fermi award was established. Fermi was awarded the first Enrico Fermi award posthumously. Now administered by the U.S. Department of Energy, the award recognizes scientists of international stature for their lifetimes of exceptional achievement in the development, use, or production of energy.
The element of atomic number 100 is named fermium in Fermi's honor, as is a unit for nuclear dimensions, the fermi. Scientists use the term fermions to describe particles obeying Fermi-Dirac statistics. An eminent atomic research laboratory near Batavia, Illinois, bears Fermi's name; it is known as the Fermi National Accelerator Laboratory.