Emilio G. Segrè, Italian-American physicist and academic, Nobel Prize laureate (b. 1905)

Emilio Gino Segrè, born on February 1, 1905, in Tivoli, a picturesque town near Rome, Italy, was a distinguished figure whose scientific journey profoundly impacted physics in both Italy and the United States. A truly remarkable Italian-American physicist and Nobel laureate, Segrè is celebrated for his groundbreaking discoveries that include the elements technetium and astatine, and perhaps most famously, the antiproton—a subatomic antiparticle that confirmed a fundamental aspect of the universe. For this latter discovery, he was jointly awarded the prestigious Nobel Prize in Physics in 1959 with his colleague, Owen Chamberlain.

Segrè’s academic path initially led him to engineering at the esteemed University of Rome La Sapienza. However, his intellectual curiosity soon drew him to the captivating world of physics, a field he officially embraced in 1927. His early career saw him appointed as an assistant professor of physics at the University of Rome in 1932, a position he held until 1936. During this pivotal period, he became an integral member of a brilliant cohort of young scientists known as the "Via Panisperna boys," led by the legendary Enrico Fermi. This group made significant strides in nuclear physics, particularly in the study of neutron-induced radioactivity. Following his tenure in Rome, Segrè took on the directorship of the Physics Laboratory at the University of Palermo from 1936 to 1938, continuing his prolific research.

A pivotal moment in Segrè's career, and indeed in the history of chemistry, occurred in 1937. After a visit to Ernest O. Lawrence's pioneering Berkeley Radiation Laboratory in the United States, Segrè was sent a molybdenum strip that had been irradiated by the laboratory's cyclotron accelerator. This seemingly ordinary strip was mysteriously emitting anomalous forms of radioactivity. Through meticulous chemical and theoretical analysis, Segrè conclusively demonstrated that some of this radiation originated from a previously unknown element. He named this new element technetium, a monumental discovery as it marked the first artificially synthesized chemical element that does not naturally occur on Earth, thus expanding our understanding of the periodic table.

Tragically, 1938 brought a profound personal and professional upheaval for Segrè. Benito Mussolini's fascist government in Italy enacted draconian antisemitic laws, which explicitly barred Jews from holding university positions. As a Jew, Segrè was suddenly rendered an indefinite émigré, effectively exiled from his homeland and his academic career there. Fortuitously, Ernest O. Lawrence, recognizing Segrè's exceptional talent, extended an offer for a research assistant position at the Berkeley Radiation Lab. This provided a crucial lifeline and allowed Segrè to continue his vital scientific work in a new country. While at Berkeley, his groundbreaking research continued; he was instrumental in the discovery of the element astatine and the significant isotope plutonium-239, an element that would later play a critical role in the "Fat Man" nuclear bomb detonated over Nagasaki during World War II.

With the escalation of World War II, Segrè's expertise became indispensable to the Allied war effort. From 1943 to 1946, he joined the highly secretive Manhattan Project, the ambitious research and development undertaking that produced the first nuclear weapons, at the Los Alamos National Laboratory. As a group leader, he made a crucial discovery in April 1944: the presence of plutonium-240 impurities would render the "Thin Man," a proposed plutonium gun-type nuclear weapon, unworkable due to premature detonation. This critical finding necessitated a complete redesign of the plutonium bomb, leading to the more complex, yet ultimately successful, implosion-type device. His commitment to his adopted nation was solidified in 1944 when he became a naturalized citizen of the United States. After the war, Segrè returned to Berkeley in 1946, where he embarked on a distinguished academic career as a professor of physics and, uniquely, of the history of science, serving in these capacities until his retirement in 1972.

It was back at the Lawrence Radiation Laboratory that Emilio Segrè, alongside Owen Chamberlain, co-led a research group that achieved another monumental scientific feat: the discovery of the antiproton. This discovery, which provided empirical evidence for the existence of antimatter as theorized by Paul Dirac, earned Segrè and Chamberlain the shared 1959 Nobel Prize in Physics, cementing their place in scientific history.

Beyond his formidable contributions to physics, Segrè possessed a deep appreciation for history and a passion for photography. He diligently captured countless moments, documenting significant events and the influential people who shaped the history of modern science. After his passing on April 22, 1989, his invaluable collection of photographs was generously donated to the American Institute of Physics (AIP). In a fitting tribute to his dedication to preserving scientific heritage, the AIP proudly named its comprehensive photographic archive of physics history in his honor, ensuring his unique perspective on scientific progress continues to inspire future generations.

Frequently Asked Questions About Emilio Gino Segrè

What were Emilio Segrè’s most significant scientific discoveries?

Emilio Segrè is renowned for discovering the elements technetium (the first artificially synthesized element) and astatine, and most notably, the antiproton. The discovery of the antiproton, a subatomic antiparticle, earned him the Nobel Prize in Physics in 1959, shared with Owen Chamberlain.

Why did Segrè leave Italy?

Segrè was forced to leave Italy in 1938 due to the antisemitic laws enacted by Benito Mussolini’s fascist government, which prohibited Jews from holding university positions. He subsequently emigrated to the United States.

What was the "Via Panisperna boys" group?

The "Via Panisperna boys" was a brilliant group of young Italian scientists led by Enrico Fermi at the University of Rome in the 1930s. Emilio Segrè was a key member, and they made pioneering discoveries in nuclear physics, particularly concerning neutron-induced radioactivity.

What role did Segrè play in the Manhattan Project?

During World War II, Emilio Segrè worked as a group leader at the Los Alamos National Laboratory for the Manhattan Project. His critical discovery that plutonium-240 impurities would prevent the "Thin Man" gun-type bomb from working led to the redesign of the plutonium weapon into the more effective implosion-type "Fat Man" bomb.

What is the significance of the antiproton discovery?

The discovery of the antiproton provided crucial experimental verification for Paul Dirac's theoretical prediction of antimatter. It confirmed the existence of a particle identical to a proton but with an opposite electrical charge, marking a fundamental advance in particle physics and our understanding of the universe.

Is technetium found naturally?

No, technetium is primarily an artificially synthesized chemical element. While trace amounts can be found naturally as a product of uranium fission, Segrè's discovery was significant because it was the first element created in a laboratory, demonstrating that elements beyond those found naturally could be produced.

What happened to Segrè’s photographs?

Emilio Segrè was an avid photographer who documented many significant events and figures in the history of modern science. After his death, his extensive collection of photographs was generously donated to the American Institute of Physics (AIP), which subsequently named its photographic archive of physics history in his honor.