Sheldon L. Glashow | Biography

During the late 1960s, Steven Weinberg and Abdus Salam independently proposed a theory that linked two fundamental forces of nature, electromagnetic, and weak forces. The new electroweak theory was regarded as a major breakthrough in physicists' efforts to link all four of the fundamental forces of nature, an objective that had occupied the efforts of the greatest scientists from Isaac Newton to James Clerk Maxwell to Albert Einstein.

One problem with the original Weinberg-Salam theory, however, was that it applied to only one of the two basic types of particles, leptons. This problem was resolved by Sheldon Glashow. Glashow showed that the Weinberg-Salam theory could be extended to the second basic class of particles, quarks, by introducing a new physical concept, the charm quark.

In the early 1960s, Murray Gell-Mann had proposed that all forms of matter can be described as being composed of either leptons or quarks. As it was later developed, the Gell-Mann theory required the existence of three types of quarks: up, down, and strange quarks. To this list, Glashow added the charm quark. The existence of this fourth type of quark, he showed, would make possible the application of the electroweak theory to quarks as well as to leptons.

Glashow's prediction was soon confirmed by research at the European Center for Nuclear Research (CERN) in Geneva, Switzerland and Fermilab in Batavia, Illinois. Further confirmation was obtained in November 1974 with the discovery of the J/&psgr; particle, a particle composed of a charm quark and its antiparticle, an anticharm quark.

Sheldon Glashow was born in New York City on December 5, 1932. He attended the Bronx High School of Science, where he was a classmate of Steven Weinberg's. Glashow earned his bachelor's degree in 1954 from Cornell (where Weinberg was also a student) and his master's (1955) and doctorate (1958) from Harvard. He did post-doctoral research at the Bohr Institute in Copenhagen, at CERN, and at the California Institute of Technology, before taking a teaching assignment at the University of California at Berkeley in 1962. In 1967 he returned to Harvard as professor of physics. Glashow shared the 1979 Nobel Prize in physics with Weinberg and Salam.

In 1974, Glashow collaborated with Howard Georgi to produce a unified theory that ties together the strong and electroweak theories. Georgi and Glashow attempted to show how both forces can be thought of as manifestations of a single basic force by applying a gauge theory known as SU(5). A gauge theory is a mathematical theory that shows how some physical property remains constant in two or more widely different frames of reference. To date, the Georgi-Glashow theory has provided a fruitful basis for further research and debate although its validity has not been confirmed.