Astronomer Edwin Hubble was born on this date in 1889.
During the past 100 years, astronomers have discovered quasars, pulsars, black holes and planets orbiting distant suns. But all these pale next to the discoveries Edwin Hubble made in a few remarkable years in the 1920s. At the time, most of his colleagues believed the Milky Way galaxy, a swirling collection of stars a few hundred thousand light-years across, made up the entire cosmos. But peering deep into space from the chilly summit of Mount Wilson, in Southern California, Hubble realized that the Milky Way is just one of millions of galaxies that dot an incomparably larger setting.
Hubble went on to trump even that achievement by showing that this galaxy-studded cosmos is expanding — inflating majestically like an unimaginably gigantic balloon — a finding that prompted Albert Einstein to acknowledge and retract what he called “the greatest blunder of my life.” Hubble did nothing less, in short, than invent the idea of the universe and then provide the first evidence for the Big Bang theory, which describes the birth and evolution of the universe. He discovered the cosmos, and in doing so founded the science of cosmology.
Source: TIME 100: Edwin Hubble