Glashow was born in New York City and graduated from the Bronx High School there in 1950. He went on to Cornell University, where he gained his bachelor's degree in 1954. His MA (1955) and PhD in physics (1959) were gained at Harvard University, and his postdoctoral research took him to the Bohr Institute, the European Organization for Nuclear Research (CERN) in Geneva, and the California Institute of Technology. After a year at Stanford he joined the faculty of the University of California at Berkeley (1961–66). In 1967 he returned to Harvard as a professor of physics, and has remained there since.

The award of the 1979 Nobel Prize, shared with Abdus Salam and Steven Weinberg, was for the explanation of the forces that bind together elementary particles of matter. The citation was “for their contribution to the theory of the unified weak and electromagnetic interaction between elementary particles, including inter alia the prediction of the weak neutral current.”

The Weinberg–Salam theory was a major step in unifying two of the four fundamental forces of physics: the electromagnetic interaction and the weak interaction. The theory was originally applied only to the class of particles known as leptons (electrons and neutrinos). Glashow extended the theory to other elementary particles (including the baryons and mesons) by introducing a new property that he called ‘charm’. The quark theory of Murray Gell-Mann could be extended by the introduction of a fourth quark – the ‘charmed quark’ – and combinations of the four types of quark could lead to a group of particles with symmetry SU4. The idea of charm can be used to explain the properties of the J/psi particle, discovered in 1974 by Burton Richter and Samuel Ting.

Other extensions of the quark theory have since been made involving ‘colored quarks’ – the theory is known as quantum chromodynamics.