Edwin Powell Hubble November 20, 1889 – September 28, 1953 was an American astronomer. He profoundly changed our understanding of the universe by demonstrating the existence of other galaxies besides the Milky Way. He also discovered that the degree of redshift observed in light coming from a galaxy increased in proportion to the distance of that galaxy from the Milky Way. This became known as Hubbles law, and would help establish that the universe is expanding.

Website: http://en.wikipedia.org/wiki/Edwin_Hubble