Edwin Hubble
Edwin Powell Hubble was born in Missouri in 1889. To please his father he studied law, but after his father died he returned to university to gain a PhD in astronomy. After serving in World War One, he took up a post at the Mount Wilson Observatory.
At this time it was widely believed that our Milky Way Galaxy was the entirety of the Universe. By studying Cepheid variable stars in faint ‘nebulae’, Hubble proved these were too distant to be part of our Galaxy, instead being galaxies in their own right. In 1929 he observed that the velocity of such galaxies was proportional to their distance from Earth, the first evidence for the expansion of the Universe – although Hubble himself believed his observations pointed to a flat and homogenous Universe and rejected the expansion theory.
One of the Hubble Space Telescope’s primary missions was to build on his work, and accurately measure the distances of Cepheid variable stars and refine the ‘Hubble Constant’ relationship of galaxies’ velocities and their distance from us. By studying distant supernovae, it provided evidence that instead of decelerating under the influence of gravity, the expansion of the Universe was accelerating, an effect now attributed to dark matter.