Born on 5 February 1915 in New York City, Robert Hofstadter was a Nobel Prize–winning physicist who exposed the structure of the atomic nucleus and its constituent particles. A professor at Stanford beginning in 1950, Hofstadter taught there until 1985. Using a linear electron accelerator, Hofstadter probed atomic nuclei and measured the size and structure of the component protons and neutrons. In 1961 he shared the Nobel Prize in Physics with Rudolf Mössbauer “for his pioneering studies of electron scattering in atomic nuclei and for his thereby achieved discoveries concerning the structure of the nucleons.” Toward the end of his career, Hofstadter contributed to the development of the Compton Gamma Ray Observatory. He died in 1990 at age 75. (Photo credit: AIP Emilio Segrè Visual Archives, Physics Today Collection)
