In collaboration with James Bjorken, Glashow was the first to predict a fourth quark, the charm quark, in 1964. This was at a time when 4 leptons had been discovered but only 3 quarks proposed. The development of their work in 1970, the GIM mechanism showed that the two quark pairs: (d.s), (u,c), would largely cancel out flavor changing neutral currents, which had been observed experimentally at far lower levels than theoretically predicted on the basis of 3 quarks only. The prediction of the charm quark also removed a technical disaster for any quantum field theory with unequal numbers of quarks and leptons — an anomaly — where classical field theory symmetries fail to carry over into the quantum theory.
In 1973,[10] Glashow and Howard Georgi proposed the first grand unified theory. They discovered how to fit the gauge forces in the standard model into an SU(5) Lie group group, and the quarks and leptons into two simple representations. Their theory qualitatively predicted the general pattern of coupling constant running, with plausible assumptions, it gave rough mass ratio values between third generation leptons and quarks, and it was the first indication that the law of Baryon number is inexact, that the proton is unstable. This work was the foundation for all future unifying work.
Glashow is a skeptic of superstring theory due to its lack of experimentally testable predictions. He had campaigned to keep string theorists out of the Harvard physics department, though the campaign failed.[13] About ten minutes into "String's the Thing", the second episode of The Elegant Universe TV series, he describes superstring theory as a discipline distinct from physics, saying "...you may call it a tumor, if you will...".[14]
Personal life
Glashow is married to Joan Shirley Alexander. They have four children.[5]Lynn Margulis was Joan's sister, making Carl Sagan his former brother-in-law. Daniel Kleitman, who was another doctoral student of Julian Schwinger, is also his brother-in-law, through Joan's other sister, Sharon.
In 2003, he was one of 22 Nobel Laureates who signed the Humanist Manifesto.[15] Glashow has described himself as a "practising atheist" and a Democrat.[16]
From Alchemy to Quarks: The Study of Physics as a Liberal Art (1994) ISBN0-534-16656-3
Interactions: A Journey Through the Mind of a Particle Physicist and the Matter of this World (1988) ISBN0-446-51315-6
First Workshop on Grand Unification: New England Center, University of New Hampshire, April 10–12, 1980 edited with Paul H. Frampton and Asim Yildiz (1980) ISBN0-915692-31-7
Third Workshop on Grand Unification, University of North Carolina, Chapel Hill, April 15–17, 1982 edited with Paul H. Frampton and Hendrik van Dam (1982) ISBN3-7643-3105-4
^"[T]here ain't no experiment that could be done nor is there any observation that could be made that would say, `You guys are wrong.' The theory is safe, permanently safe." He also said, "Is this a theory of Physics or Philosophy? I ask you" NOVA interviewArchived 2011-08-30 at the Wayback Machine
^"Notable Signers". Humanism and Its Aspirations. American Humanist Association. Archived from the original on October 5, 2012. Retrieved October 2, 2012.
^Sheldon Glashow, Nobel Prize in Physics for the Electroweak Theory . La Vanguardia, 20 June 2017, raed.academy/wp-content/uploads/2017/06/Sheldon-Lee-Glashow-contraLVeng.pdf.