The U. S. patent for a neutronic reactor has on it the names of two immi­grants: Leo Szilard from Hungary and Enrico Fermi (1901-54), a leading nuclear physicist from Italy. It was originally Szilard’s fanciful idea to cre­ate a sustained chain reaction of nuclear fission even before fission was discovered, but it was Fermi’s genius that reduced the concept to a work­ing, physical machine, capable of releasing power from the atomic nucleus. In doing so, he originated the discipline of nuclear engineering. Although the patent application was made in 1944, as World War II raged on, the document remained secret for 11 years, and the patent was not awarded until 1955, a year after Fermi died of stomach cancer. The nuclear reactor is considered one of the most important inventions in U. S. history. It won Fermi a place in the National Inventors Hall of Fame. In a recent poll by Time magazine, he was listed among the top 20 scientists of the 20th century.

The invention of the nuclear reactor was not necessarily Fermi’s great­est accomplishment. In 1933, before he came to the United States, Fermi had formulated a theory of the beta decay of elements. To electromag­netic force, gravitational force, and the strong nuclear force that holds the nucleus together, he added a weak nuclear force, responsible for the break­down of neutrons and protons and the release of electrons and positrons as radiation, or negative and positive beta particles.

Enrico Fermi was born on September 29, 1901, in Rome, Italy, to Alberto, a chief inspector of the Ministry of Communications in Rome,

and Ida de Gattis. His immersion into the study of physics probably began at 14, when his older brother, Giulio, died unexpectedly during surgery for a throat abscess. The boys had been very close. The death hit young Enrico hard, and he sought a diversion. Soon after, he was browsing in the stalls of the Campo dei Fiori in Rome and discovered two volumes of Elemen­tary Mathematical Physics, written in 1840 by a Jesuit physicist. He used his entire allowance to purchase the books and read them cover to cover multiple times. A friend of his father loaned him many books on physics and mathematics, and he studied each of them thoroughly. By the time he graduated from high school a year early, he had decided to dedicate him­self exclusively to the study of physics.

Fermi was accepted at the Scuola Normale Superiore in Pisa, where he earned his undergraduate and doctoral degrees in physics. His entrance essay was considered exemplary and of Ph. D. thesis quality, and in college he became a great propagandist for quantum mechanics. In 1924, while working on his doctorate, he spent a semester in Gottingen, Germany, working with Werner Heisenberg (1901-76), the notable theorist in quan­tum mechanics, finding the philosophical, nebulous bend of this branch of physics hard to swallow. Fermi developed a style demanding concrete­ness and rigorous simplicity, inclined toward physical phenomena that could be confirmed by direct, unambiguous experimentation. He became a rare specimen of physicist, one who straddles the worlds of theoretical and experimental science with perfect balance. As a fellow physicist once remarked, “He was simply unable to let things be foggy. Since they always are, this kept him pretty active.”

From studies in Germany, Fermi plunged into a professorship in phys­ics at the University of Rome-La Sapienza in 1926. This would prove to be a challenging position, as Italy had a poor reputation in the physics com­munity, and facilities and funding were at a subsistence level. Stepping boldly into the job, Fermi selected a competent team, soon nicknamed the “Via Panisperna boys.” The men in his research group counter-nicknamed Fermi “the Pope.” By 1933, Fermi had completed a detailed, quantitative study of beta decay in radioactive materials, complete with a fundamental theory of beta radiation. His paper describing this work, “Tentativo di una Teoria dei Raggi в” (An attempted theory of beta rays), was rejected by the journal Nature as being too removed from physical reality, so he published it in an Italian journal, Ricerca Scientifica (Scientific research). It would be six years before the editors at Nature realized their profound mistake and finally published the paper in English.

At the age of 33, Fermi and his team then engaged in one of the most important research efforts in the history of nuclear power. Using hand — built Geiger counters and neutron sources, they measured the interactions of neutrons with almost every element on the periodic table. One result of neutron bombardment to be measured was activation, in which a mate­rial absorbs a neutron and becomes radioactive. Some elements are very sensitive to activation, and some are not. When measuring the activation of silver, by accident the team found a puzzling effect. The intensity of the activation apparently depended on where in the laboratory the experiment was conducted. Most of the laboratory benches were topped with fine, Italian marble, but one bench had a wooden top, and this bench seemed