In the early 20th century, astronomers marvelled at the abundant and beautiful “spiral nebulae” that flecked the night sky. But they had few clues about the nature of these lovely objects. Were they new solar systems forming within our own Milky Way? Or were they galaxies in their own right, separated from our own galaxy by immense distances?
A hundred years ago, no one knew. But a diligent and unassuming Indiana farm boy made a fundamental discovery that hinted at the nature of the spiral nebulae, and laid the framework for understanding the nature of our universe.