Today is the birthday of Edwin Hubble, an American astronomer born in 1889 who is famous for discovering that the universe contains galaxies outside of our own and is expanding. After stints as an amateur heavyweight boxer, a lawyer, and a soldier, Hubble turned to astronomy and began observations at Mount Wilson Observatory in Pasadena, California. He discovered the Andromeda galaxy and eight others that, from his calculations, appeared to exist far beyond the edges of the Milky Way. He announced the findings in 1924, settling a long-standing debate over the existence of other galaxies.
Hubble also observed that a number of galaxies appeared to be zooming away from the Milky Way, which led him to develop a mathematical concept now known as Hubble's Law: The more distant a galaxy is, the faster it is moving away from us. That planted the seeds for the theory that the universe is expanding and was created in a big bang. The Hubble Space Telescope is named in his honor. He died in 1953.
[Source: Emily McMurray, Ed., Notable Twentieth Century Scientists (Gale Research Inc., ITP, 1995).]