In 1919, Edwin Hubble (1889-1953) went to work at Mount Wilson Observatory near Los Angeles. At the time, Mount Wilson was a lonely outpost on the outskirts of a small city. Today it has been engulfed by the Los Angeles metropolitan area, but in those days it afforded astronomers a chance to look at the sky through clear, unpolluted air. It had what was then the world's largest telescope, whose mirror measured 100 inches across.
He received a Ph. D. in astronomy from the University of Chicago in 1919. At age 30 he began a career that was to change forever our view of humanity's place in the universe.
By the time Hubble began working at Mount Wilson, astronomers has been debating for almost a century about the nature of the universe we live in. They had known for a long time that the Sun is one of a large collection of stars in the Milky Way. Is this collection just one f many “island universes” in the vastness of space, they asked, or is the Milky Way all there is? Throughout the latter part of the nineteenth century and the early part of the twentieth century, the debate raged, for one simple reason: While it was evident that stars in the Milky Way are no more than 100,000 light years away, no one could prove an accurate measurement of the distance of any object that might lie outside the Milky Way.