Enrico Fermi

Enrico Fermi was an Italian physicist who created the first nuclear reactor and made decisive contributions to the development of quantum theory, nuclear physics, and particle physics. He is one of the few physicists to have worked with both theoretical and experimental methods at the highest level.

Early Life and Education

Fermi was born in Rome in 1901, the son of a railway official. He showed an early aptitude for physics and built his own electrical and mechanical devices as a boy.

He studied at the Scuola Normale Superiore in Pisa and took his doctorate in 1922. He later studied with Max Born in Göttingen and with Paul Ehrenfest in Leiden.

He was appointed professor of theoretical physics at the University of Rome in 1926. He gathered around him a group of young physicists who became known as the Via Panisperna boys.

The Fermi Statistics and the Theory of Beta Decay

Fermi developed a statistical theory of particles that obey the exclusion principle. The particles are now known as fermions and the statistics as Fermi-Dirac statistics.

He formulated a theory of beta decay in which the neutron emits an electron and a neutrino. The theory introduced the weak interaction and was later developed by other physicists.

He introduced the constant that governs the strength of the weak interaction. The constant is known as the Fermi constant and remains a fundamental quantity of physics.

The Discovery of Nuclear Reactions

Fermi began to experiment with the bombardment of heavy elements by neutrons after 1934. He found that the results were best explained by the capture of the neutron and the emission of a gamma ray.

He discovered that the neutrons were more effective when they passed through paraffin or water. The effect was caused by the slowing of the neutrons by the hydrogen nuclei.

He received the Nobel Prize in Physics in 1938 for his work on induced radioactivity. He used the occasion to leave Italy with his family and to settle in the United States.

The Manhattan Project and the First Reactor

Fermi joined the Manhattan Project and worked at the University of Chicago. He directed the construction of the world's first nuclear reactor, known as Chicago Pile-1.

The reactor went critical on 2 December 1942 under the west stands of the Stagg Field stadium. The event demonstrated the controlled release of nuclear energy for the first time.

Fermi was present at the Trinity test of the first atomic bomb in 1945. He observed the explosion and estimated the yield by dropping scraps of paper into the shock wave.

He continued to work on the development of nuclear reactors and on the design of the hydrogen bomb. He opposed the development of the thermonuclear weapon on moral grounds.

The Later Years and the Legacy

Fermi returned to fundamental research after the war. He worked on the origin of cosmic rays and on the interaction of pions with nucleons.

He was a professor at the University of Chicago and trained a generation of physicists. His lectures on thermodynamics, mechanics, and quantum mechanics were widely admired.

He died in 1954 in Chicago. The element fermium and the Fermi National Accelerator Laboratory in Illinois are named in his honour.

Fermi is remembered for the breadth of his work and for the elegance of his methods. The problem-solving approach known as the Fermi estimate is named after him.

The Fermi Paradox

Fermi is associated with the question of why the universe appears to be devoid of the intelligent life. The question is known as the Fermi paradox.

The argument holds that the galaxy is very old and very large, and that the civilisations should have colonised it by now. The absence of the evidence is a puzzle.

The paradox has been discussed by the astronomers and the philosophers. It remains an unresolved problem of the search for the extraterrestrial intelligence.

The Style and the Method

Fermi was known for the clarity of his thought and for his direct approach to the problem. He preferred the simple estimate to the elaborate calculation.

The method of the order-of-magnitude estimate is known as the Fermi problem. The technique is used in the teaching of the physics.

He was admired by his students and his colleagues for his breadth and his generosity. He was a central figure of the physics of the twentieth century.

The Honours and the Memory

Fermi received the Nobel Prize in Physics in 1938 for the demonstration of the existence of the new radioactive elements and the discovery of the nuclear reactions caused by the slow neutrons.

He was a member of the Royal Society and of the National Academy of Sciences. He received the Max Planck Medal and the Hughes Medal.

The element fermium and the Fermi National Accelerator Laboratory are named in his honour. The Fermi level and the Fermi surface are named after him in the physics of the solid state.

See also

• Nuclear fission
• Manhattan Project
• Fermi-Dirac statistics
• Weak interaction