Edwin Powell Hubble

The American astronomer Edwin Powell Hubble, b. Marshfield, Mo., Nov. 20, 1889, d. Sept. 28, 1953, was a pioneer in the study of extragalactic astronomy. He composed (1925) the classification scheme for the structure of galaxies that is still in use today and provided the conclusive observational evidence for the expansion of the universe. A graduate of the University of Chicago, where he studied physics and astronomy and excelled as a heavyweight boxer, Hubble obtained a law degree at Oxford and briefly practiced law before earning his Ph.D. in astronomy at Chicago in 1917. After World War I, Hubble went to Mount Wilson Observatory, where in 1923 he settled a long debate by demonstrating that the Andromeda nebula was far outside our galaxy. This discovery established the so-called island universe theory, which states that galaxies exist outside our own. Hubble's study of the distribution of galaxies resulted in the discovery (1929) of Hubble's law, from which the fundamental cosmological quantity known as Hubble's constant is derived.