The Milky Way Isn't the Only Thing in the Universe

Not everybody was on board with the idea that the milky way is the only thing in universe. Some astronomers noticed that some of these nebulas were shaped like spirals. The fact that they were spiral suggested they were spinning, consistent with the idea solar systems form out of spinning nebula. But not everyone was convinced by this explanation: we could see stars inside some of the nebulas. So some people proposed maybe the spiral nebulas are made of stars too. That would make them like far away versions of the milkyWay. And since the milky Way was often called the universe just an island of stars in the great darkness, the hypothesis grew up that the spiral