Canadian-born American mathematical astronomer. At the US Naval Observatory's Nautical Almanac office, of which he became head in 1877, he initiated an extensive project to refine the orbits of the Moon and planets. (G. W. Hill was assigned the motions of Jupiter and Saturn.) The project involved the use of historical data, from which he discovered the non-Newtonian component of the advance of the perihelion of Mercury's orbit that was later accounted for by the general theory of relativity. Newcomb improved the value of the solar parallax and other astronomical constants, and worked with A. A. Michelson on a method for measuring the speed of light.
Subjects: Astronomy and Astrophysics.