 He was a postdoc from 1955 to 1956 at MIT, from 1956 to 1957 at the University of California, Berkeley, and from 1957 to 1958 at Stanford University, where he was an assistant professor from 1958 to 1960.In 1960 he joined the faculty of Caltech and remained there until he retired in September 1999 as professor emeritus.In 1960 he was a Sloan Research Fellow.