June 24: Martin Perl and Subatomic Particles

Physicist Martin Perl, who shared the 1995 Nobel Prize in Physics with Frederick Reines for their discovery of subatomic particles, the tau lepton (Perl) and the neutrino (Reines), was born to Polish Jewish immigrants in New York on this date in 1927. Perl earned his Ph.D. at Columbia in 1955 and studied particle physics for eight years at the University of Michigan before moving to Stanford, which had built a two-mile-long particle accelerator in 1963. The particle he discovered is 3,500 times as massive as an electron but exists for only a third-trillionth of a second before “decaying into a spray of its lighter brethren and the ghostly particles known as neutrinos,” writes Dennis Overbye in the New York Times. Perl was an active opponent of the Vietnam War and a co-founder of Scientists and Engineers for Social and Political Action. “He always advocated,” said his son, “that you should look at what the crowd is doing and go in a different direction.” Perl died at 87 in 2014. “When he began the series of experiments that would lead to the Nobel Prize, the Standard Model that describes the fundamental particles and forces of nature seemed to be complete, with matter divided into two classes: quarks and leptons. For many years Perl maintained there was no good reason for there to be two families of leptons, rather than three or even four; and when the SLAC linear accelerator turned on in the early 1960s, he immediately attempted to find a third family...” —Glennda Chui, Stanford News