Edwin Hubble's discovery reshapes understanding of galaxies a century ago

A century ago, astronomer Edwin Hubble made a groundbreaking discovery that changed our understanding of the universe. He identified Cepheid variable stars in the Andromeda Galaxy, proving it was a separate galaxy, not part of the Milky Way. Before Hubble's work, astronomers debated whether the universe contained multiple galaxies or was limited to the Milky Way. Harlow Shapley and Heber Curtis had differing views, but neither could provide conclusive evidence. Hubble's findings, announced in 1924, confirmed that galaxies are vast, distant collections of stars. This discovery significantly expanded the known scale of the universe and established Hubble's legacy in modern astronomy.