Yesterday was the 98th anniversary of the discovery of galaxies, which has always seemed to me to be an odd way of putting it. For years, astronomer Edwin Hubble had been looking at nebulas which he believed were inside our galaxy, because he thought everything was in our galaxy. All astronomers believed that everything they were looking at was in our galaxy. That was the accepted wisdom of their time.
But 98 years ago Hubble figured out that some of the nebulas he was looking at were too far away to be inside our galaxy. That’s when he had his smack-my-head moment and “discovered” other galaxies. What Hubble actually discovered was that, up until that point, astronomers had been stupid.