Freedom in New York
Sheldon Lee Glashow was born in Manhattan on December 5, 1932, the youngest son of Lewis Glashow and Bella (Rubin) Glashow, Jewish immigrants from Bobruisk in what is now Belarus. In his Nobel autobiography he wrote that his parents found in New York the freedom and opportunity denied to Jews in Czarist Russia. After years of struggle his father, born Gluchovsky, became a successful plumber, and the family could enjoy the comforts of the middle class. Neither parent had been able to go to university, but they were adamant that their children would.
His brothers, Samuel and Jules, were eighteen and fourteen years older and became a dentist and a physician, to their parents’ satisfaction. Sam interested ten-year-old Sheldon in the laws of falling bodies, and when he was fifteen his father and brother helped him equip a chemistry laboratory in the basement, where he became skilled at making selenium compounds; never again, he joked, would he do such dangerous research. His parents encouraged him throughout, apart from the occasional suggestion that he become a doctor and do science in his spare time.
The Bronx High School of Science
Glashow attended the Bronx High School of Science, a selective public school whose class of 1950 turned out to be remarkable. His friends included Gary Feinberg, who also became a physicist, and Steven Weinberg, with whom he would one day share a Nobel Prize. The boys spurred each other to learn physics while commuting on the New York subway, and another classmate, Daniel Greenberger, taught Glashow calculus in the school lunchroom.
He went on to Cornell University with Weinberg, graduating in 1954, and then to Harvard for graduate work under the brilliant and overstretched Julian Schwinger, who had about a dozen doctoral students at a time. Glashow’s thesis, on the vector meson in elementary particle decays, already showed his interest in unifying the weak and electromagnetic forces. He and Schwinger planned a paper together on the subject, but one of them lost the first draft and it was never written.
Waiting for a visa
With a National Science Foundation fellowship, Glashow planned to work in Moscow with the physicist Igor Tamm. The Soviet visa never came, so he spent the fellowship from 1958 to 1960 at the Niels Bohr Institute in Copenhagen and at CERN in Geneva. Perhaps it was all for the best, he wrote later, because in those years he discovered the mathematical structure of the theory that would make his name.
Physicists then knew four fundamental forces: gravity, electromagnetism, the strong force that holds atomic nuclei together, and the weak force that causes some kinds of radioactive decay. The weak force seemed utterly different from electromagnetism; it acts only over tiny distances and is far feebler. Glashow proposed that the two are aspects of one underlying interaction, described by a symmetry pattern known as SU(2) × U(1). In his 1961 paper this framework required, besides the photon that carries electromagnetism, heavy charged carriers of the weak force and a new neutral one, now called the Z boson.
While he was in Europe, Murray Gell-Mann heard of his ideas, presented them at a major conference in 1960 and brought him to the California Institute of Technology. Gell-Mann then invented the eightfold way, a scheme for classifying the strong-force particles, which kept Glashow and his friend Sidney Coleman busy for years. Glashow taught at Stanford and then at the University of California, Berkeley, from 1962 to 1966. At Berkeley and elsewhere he kept working on why the symmetries of particle physics are not exact, a theme that ran through much of his later work.
The electroweak theory
Glashow’s scheme had a problem: it did not explain why the weak force carriers were so heavy while the photon has no mass. In 1967 Steven Weinberg, and independently Abdus Salam, showed how a mechanism of spontaneous symmetry breaking, involving what is now called the Higgs field, could supply those masses within Glashow’s structure. In 1971 the Dutch physicist Gerard ’t Hooft proved the theory mathematically consistent.
Experiments followed. In 1973 physicists at CERN found the first evidence of weak neutral currents, the interactions carried by the Z that the theory predicted, and later experiments at Fermilab and Stanford confirmed them. In 1979 Glashow, Salam and Weinberg shared the Nobel Prize in Physics for their contributions to the theory of the unified weak and electromagnetic interaction. Four years later CERN discovered the W and Z particles themselves, with the masses the theory had led physicists to expect, and in 2012 the discovery of the Higgs boson completed the picture.
Charm and grand unification
Glashow’s second great contribution was the charm quark. In 1964, with James Bjorken, he suggested that a fourth quark should exist to match the four known leptons. In 1970, working at Harvard with John Iliopoulos and Luciano Maiani, he showed that a fourth quark would explain why certain particle decays were far rarer than expected, an argument known as the GIM mechanism. In early 1974 he and Alvaro De Rújula predicted where charm would show up. Later that year the J/psi particle, made of a charm quark and its antiquark, was discovered, and many strands of physics suddenly converged on a single theory.
Also in 1974, Glashow and Howard Georgi proposed the first grand unified theory, fitting the strong, weak and electromagnetic forces into a single larger symmetry and predicting that protons might eventually decay. At the time, he recalled, they were regarded as mad. Proton decay has not been seen, but their work set the direction for decades of attempts to unify the forces of nature.
Why it matters
The electroweak theory is part of the Standard Model, humanity’s most precisely tested description of the particles and forces that make up everything around us. The weak force it explains is not remote from daily life. As the Nobel committee pointed out, the first step in the chain of nuclear reactions that powers the Sun is caused by the weak force; it governs the radioactive decays used in medicine and technology, and the decay of carbon-14 that lets archaeologists date ancient remains. Understanding the weak force precisely underpins nuclear and particle physics, astrophysics and the design of experiments at every large accelerator.
In 1959 Glashow also predicted that a high-energy antineutrino striking an electron could create a W particle at one precise energy, far beyond any human-made accelerator. In 2021 the IceCube observatory, buried in the ice of Antarctica, reported a particle shower from a cosmic antineutrino at exactly that energy, the so-called Glashow resonance, sixty years after his prediction. The event, recorded in December 2016 and nicknamed Hydrangea, carried an energy of about 6.3 peta-electronvolts. Glashow was characteristically cautious: to be absolutely sure, he said, physicists should see another such event at the very same energy.
Teacher and citizen
Glashow returned to Harvard in 1966 and became Eugene Higgins Professor of Physics. He believed physics belonged to everyone, and in 1979 he helped inaugurate Harvard’s Core Curriculum with a course for non-scientists, From Alchemy to Quarks, which later became a textbook. He wrote popular books, including Interactions (1988) and The Charm of Physics (1991). He later moved to Boston University as Metcalf Professor of Mathematics and Physics.
He also used his standing for human rights. In 1981 he headed an international group of scientists that raised money for a scholarship fund in honour of the Soviet physicist and dissident Andrei Sakharov, then in internal exile, to reward students and scientists devoted both to science and to human liberty. He has been a member of the board of sponsors of the Bulletin of the Atomic Scientists and in 2008 joined other American physics laureates in urging more federal funding for basic science.
Family and identity
Glashow’s Jewishness is rooted in his parents’ escape from the restrictions of Tsarist Russia and in the immigrant New York that gave their sons free schools and open doors. Like many scientists of his generation he is secular; he has described himself as a practising atheist and signed the Humanist Manifesto in 2003. He appears on the standard lists of Jewish Nobel laureates, alongside his schoolmate Weinberg.
In 1972 he married Joan Alexander, and they raised four children in Brookline, Massachusetts. Through his wife he became the brother-in-law of the biologist Lynn Margulis and of the mathematician Daniel Kleitman, his own college classmate. He regretted only that neither of his parents lived to see him accept the Nobel Prize in Stockholm.
Legacy
Glashow helped turn a jumble of particles and forces into an orderly theory. The electroweak unification he began, the charm quark he predicted and the grand unified theory he proposed with Georgi shaped the Standard Model and the questions physicists still pursue. He has also been an outspoken critic of theories, such as string theory, that he believes have drifted away from testable predictions, insisting that physics must stay tied to experiment.
His own career illustrates his favourite lesson about science: that today’s strange idea can become tomorrow’s textbook. A plumber’s son who learned calculus in a school cafeteria, he helped show that two of nature’s forces are really one.
Sources & further reading
Sheldon Glashow, Biographical, NobelPrize.org · Press release: The Nobel Prize in Physics 1979, NobelPrize.org · Glashow resonance is spotted in a neutrino detector at long last, Physics World · Scientists Raise $3000 for Sakharov, The Harvard Crimson, 1981 · Sheldon Glashow, Boston University Department of Physics · Sheldon Glashow, Wikipedia · Researched from the sources above and checked against them. Spotted an error? Tell us.
A life of tikkun olam. This is part of tikkun olam, the Jewish idea of repairing the world, and every one of us can add to it.