If we could go back 101 years, we would encounter a time when scientists still thought the Milky Way was the entirety of our universe. But, if we went back 100 years instead, we would find most scientists agreeing that this isn't true. Somewhere in between, humans realized the universe is much larger than our Milky Way — that the spiral nebulas visible through telescopes were, in fact, other galaxies in their own right. The scale of the cosmos had expanded dramatically virtually overnight.
According to historical records, we have one man to thank for this: Edwin Hubble. That's certainly partly the truth, but he couldn't have done it without the genius of others around him who paved the way for his discovery.
