William Wallace Campbell (1862-1938), American astronomer. After studying civil engineering Campbell taught astronomy at the University of Michigan, USA, from 1888-1891. He became director of Lick Observatory in California in 1900, a position he held until 1930. He did a great deal of spectroscopic work, and headed the observatory's programme of using photographic methods to measure the radial velocities of stars. He was also led several expeditions to observe solar eclipses. In 1922 one of these expeditions generated data on the bending of starlight, which confirmed Einstein's theory of general relativity. He won the Gold Medal of the Royal Astronomical Society in 1906.