Carl Anderson

It’s the birthday of Carl Anderson, who was born in 1905 in New York City. Anderson studied physics and engineering at Caltech. In 1932, just two years after he had earned his PhD, he discovered in a cloud chamber experiment a particle that had the same mass as the electron but an equal and opposite charge. Anderson recognized the particle as the positron, whose existence Paul Dirac had predicted four years before. In 1936 Anderson, with his graduate student Seth Neddermeyer, made another lepton discovery: the muon, a negatively charged particle that is 207 times more massive than the electron. That same year Anderson was awarded the Nobel physics prize. In 1979 he told an oral history interviewer: “The ideal student would be one who was not working for grades but was working because he was interested in the work and not trying to compete with fellow students.”

Date in History: 3 September 1905