(1872–1942) American astronomer
Born in Muskegon, Michigan, Curtis obtained his AB (1892) and AM (1893) from the University of Michigan, where he studied classics. He moved to California in 1894 where he became professor of Latin and Greek at Napa College. There his interest in astronomy was aroused and from 1897 to 1900 he was professor of mathematics and astronomy after the college merged with the University (now the College) of the Pacific. After obtaining his PhD in 1902 from the University of Virginia he joined the staff of the Lick Observatory where he remained until 1920 when he became director of the Allegheny Observatory of the University of Pittsburg. Finally, in 1930 he was appointed director of the University of Michigan's observatory.
Curtis's early work was concerned with the measurement of the radial velocities of the brighter stars. From 1910 however he was involved in research on the nature of spiral nebulae and became convinced that these were isolated independent star systems. In 1917 he argued that the observed brightness of novae found by him and by George Ritchey on photographs of the nebulae indicated that the nebulae lay well beyond our Galaxy. He also maintained that extremely bright novae (later identified as supernovae) could not be included with the novae as distance indicators. He estimated the Andromeda nebula to be 500,000 light-years away.
Curtis's view was opposed by many, including Harlow Shapley who proposed that our Galaxy was 300,000 light-years in diameter, far larger than previously assumed, and that the spiral nebulae were associated with the Galaxy. In 1920, at a meeting of the National Academy of Sciences, Curtis engaged in a famous debate with Shapley over the size of the Galaxy and the distance of the spiral nebulae. Owing to incomplete and incorrect evidence the matter was not settled until 1924 when Edwin Hubble redetermined the distance of the Andromeda nebula and demonstrated that it lay well beyond the Galaxy.
Subjects: Science and Mathematics.