
Philosophers, mathematicians, and astronomers across cultures and centuries have long debated and theorized about the night sky. But in the early 1920’s, building on the work of Henrietta Swan Leavitt and others, astronomer Edwin Hubble produced the first clear evidence that the swirling clusters visible through telescopes were actually distant galaxies, comparable to our own Milky Way. By capturing detailed, long-exposure images of space features like pulsing, Cepheid variable stars, Hubble confirmed the true nature of the Andromeda Nebula and others. These weren’t just nearby gas clouds, but far away islands of worlds and stars.