Edwin Hubble

By Julien Moreau

He looked through the largest telescope on earth and discovered that the universe is vastly larger than anyone had imagined — and that it is flying apart. Edwin Hubble was born in 1889 in Missouri, a tall, athletic Rhodes Scholar who studied law at Oxford to please his father, then abandoned it for astronomy, as if the sky had been calling all along. At Mount Wilson Observatory in California, he had the great 100-inch Hooker telescope, the most powerful eye on the heavens then existing. In 1923 he photographed a pulsing Cepheid variable star in the Andromeda Nebula and used Henrietta Leavitt's period-luminosity law to calculate its distance: it lay far beyond the Milky Way. Andromeda was not a cloud inside our galaxy — it was another galaxy, an island universe unto itself. Overnight the cosmos grew from one galaxy to billions. Hubble then measured the light of distant galaxies with Milton Humason and found their spectra shifted red — receding from us — and in 1929 announced the velocity-distance relation: the farther a galaxy, the faster it flees. The universe was expanding. Hubble himself, cautious to a fault, refused to draw the cosmological conclusion, but the implication was inescapable and Georges Lemaître and others drew it: the universe had a beginning. Hubble spent the war years running ballistics research at Aberdeen, returned to champion the 200-inch Palomar telescope, and lobbied, unsuccessfully in his lifetime, for astronomy's inclusion in the Nobel Prizes. He died in 1953 of a cerebral thrombosis. The space telescope that bears his name has since photographed the deep field he only dreamed of — galaxies upon galaxies, receding exactly as he measured. His name now measures the universe's expansion rate — the Hubble constant — and its precise value is modern cosmology's sharpest dispute, the so-called Hubble tension. He would have relished the fight: the cautious observer who started it all, still setting the agenda from beyond the grave.

Impact on civilization

Hubble gave humanity its true address: one galaxy among hundreds of billions in an expanding universe. The Hubble law is the observational foundation of modern cosmology and the Big Bang. He ended the era when the Milky Way was the universe, and opened the era of deep time and deep space — the largest expansion of the human world-picture since Copernicus. The orbiting telescope that bears his name has extended his work to the edge of the visible universe, photographing galaxies whose light left them when the cosmos was young.