Edwin Hubble

Edwin Powell Hubble was an American astronomer who fundamentally changed our understanding of the universe — twice. Born in Marshfield, Missouri, he was a gifted athlete and Rhodes Scholar who studied law at Oxford before following his true passion into astronomy. Working at the Mount Wilson Observatory with the 100-inch Hooker Telescope — then the world's largest — Hubble used Henrietta Leavitt's Cepheid period-luminosity relation to measure the distance to the Andromeda "nebula" in 1924. His result showed it was far outside the Milky Way, proving that the universe contained countless separate galaxies — settling the "Great Debate" that had divided astronomy. Five years later, building on work by Vesto Slipher, Hubble discovered that galaxies are moving away from us at speeds proportional to their distance (Hubble's Law), revealing that the universe is expanding. This was the observational foundation for the Big Bang theory. The Hubble Space Telescope, launched in 1990, was named in his honor.

Proved that galaxies are separate "island universes" far beyond the Milky Way (1924). Discovered the expansion of the universe (Hubble's Law, 1929): galaxy recession velocity is proportional to distance. Created the Hubble galaxy classification system (elliptical, spiral, barred spiral, irregular) — the "tuning fork" diagram. His discoveries provided the observational basis for the Big Bang theory. The Hubble Space Telescope, one of the most important scientific instruments ever built, bears his name.