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Julian Schwinger

Theoretical physicist Julian Schwinger used the mathematical process of renormalization to rid the quantum field theory developed by Paul Dirac of serious incongruities with experimental observations that had nearly prompted the scientific community to abandon it.

Julian Schwinger

For this achievement, which firmly established quantum electrodynamics (QED) as an accurate predictor of the interactions of charged particles, Schwinger won the Nobel Prize in Physics in 1965. Physicists Richard Feynman and Sin-Itiro Tomonaga, who similarly refined QED theory at about the same time as Schwinger, shared the award with him that year.

The son of a manufacturer in New York City, Schwinger was born on February 12, 1918. He became interested in physics from popular science magazines at an early age and tried to quench his thirst for knowledge by scouring the city’s libraries and secondhand bookstores for physics texts. Schwinger quickly absorbed all that he read and was able to skip several grades in high school. At the age of 14, he enrolled at the City University of New York. Just two years later, Physics Review accepted one of Schwinger’s papers on quantum mechanics for publication. The work garnered Schwinger the attention of renowned physicist Isidor Rabi, who taught at Columbia University. With Rabi’s help, Schwinger won a scholarship to study at Columbia. He earned his bachelor’s degree there by age 17, and his Ph.D. a few years later.

Schwinger carried out postdoctoral research at the University of California, Berkeley, under the direction of J. Robert Oppenheimer. Then, in 1941, he accepted an instructorship at Purdue University in West Lafayette, Indiana. Schwinger soon took a leave of absence, however, to assist in research at the University of Chicago Metallurgical Laboratory for the Manhattan Project. He also contributed to the American war effort by improving radar and microwave technologies at the Massachusetts Institute of Technology. After the war, instead of returning to Purdue, Schwinger remained in Massachusetts to join the faculty of Harvard University as associate professor.

The year 1947 was eventful for the young scholar. He was awarded full professorship, a considerable honor for someone not yet 30; he also married Clarice Carrol. That same year he attended an important conference on theoretical physics at Shelter Island, New York, where a hotly-discussed topic was the discrepancy between quantum theory and the results of two recent experiments. Another young American physicist, Richard Feynman, was also in attendance. The meeting inspired both men, working independently, to find a way to reconcile the theory and the experimental findings.

In 1948, the first of a series of papers written by Schwinger and containing mathematical modifications, redefinitions of several terms and extensions of quantum theory appeared in Physics Review. Almost simultaneously, Feynman’s revisions of Dirac’s theory were also published. Both men are recognized equally for their groundbreaking work in quantum electrodynamics. Meanwhile, in Japan, Tomonaga had actually developed much of his version of QED theory earlier than the Americans, but the English translation of his work did not appear until after World War II.

Schwinger’s contributions to QED gained him widespread recognition in the scientific community. In 1949, he received the Nature of Light Award of the U.S. National Academy of Sciences, in 1951 he accepted the first Einstein Prize, in 1964 he won the U.S. National Medal of Science and, finally, in 1965 he became a Nobel laureate. Numerous prestigious universities venerated Schwinger with honorary doctorate degrees.

Schwinger continued to concentrate on particle physics throughout his career, but his research interests varied within the field. In the early 1950s, he proposed what is generally known as the Schwinger effect, in which an electric field can cause electron-positron pairs to be pulled out of a vacuum. Late in the decade, he accurately predicted the existence of two neutrinos that are associated with the electron and the muon. Later work by Schwinger included the development of source theory, the proposal of a precise approximation for the way that atomic ground-state energy and atomic charge vary with one another, and research into the controversial area of cold fusion. After papers he wrote on cold fusion were rejected for publication by the American Physical Society, he resigned from the group in the late 1980s, claiming they repressed academic freedom.

Schwinger was highly regarded not only for his theoretical work but for his gifts as a teacher of physics. Several of his students went on to win the Nobel Prize. Schwinger penned a number of tracts and science books. Most require a thorough understanding of theoretical physics, but a tome on Albert Einstein appealed to a broader readership. In 1972, Schwinger left Harvard to accept a physics post at the University of California, Los Angeles, where he worked until his death on July 16, 1994, from cancer of the pancreas.