Edwin Hubble

Edwin Powell Hubble was born on November 20, 1889, in Marshfield, Missouri. He grew up in Illinois and showed early promise in both athletics and academics. He studied mathematics and astronomy at the University of Chicago, graduating in 1910, and then went to Oxford as a Rhodes Scholar, where he read law at the request of his father. After his father's death, he returned to science, earning his doctorate in astronomy from the University of Chicago in 1917.

Following service in the United States Army during World War I, Hubble joined the staff of the Mount Wilson Observatory near Pasadena, California, in 1919. There he had access to what was then the world's largest telescope, the 100-inch Hooker reflector, which proved decisive for his subsequent discoveries.

In the early 1920s, a major astronomical debate concerned the nature of certain hazy objects called nebulae. Many astronomers believed these lay within the Milky Way; others suspected they were distant systems comparable to the Milky Way itself. In 1923 and 1924, Hubble resolved individual stars in the Andromeda Nebula, including Cepheid variable stars, whose intrinsic brightness was already well-understood. By calculating the distance to these Cepheids, he demonstrated that Andromeda lay far beyond the boundaries of the Milky Way, making it a separate galaxy. This result, announced in 1925, settled the debate and permanently expanded the known scale of the universe.

Hubble went on to develop a classification system for galaxies, organizing them by their shapes into ellipticals, spirals, and irregulars, a framework that remains in use today.

His most consequential discovery came from measurements of the recession velocities of galaxies combined with their distances. In 1929, he published findings showing that galaxies are moving away from the Milky Way and that more distant galaxies recede faster, a relationship now expressed as Hubble's Law. This provided the key observational evidence that the universe is not static but expanding, a finding consistent with solutions to Einstein's field equations and later foundational to the Big Bang model of cosmology.

Hubble also contributed to the classification of galaxy types and continued refining distance measurements throughout his career at Mount Wilson and later Palomar Observatory.

Edwin Hubble died on September 28, 1953, in San Marino, California. In 1990, NASA launched the Hubble Space Telescope, named in his honor.