system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Do other galaxies in the sky move?

Since the Earth spins, the sky appears to rotate around us throughout the year. Our galaxy is also spinning, so do objects beyond our galaxy (other galaxies and nebulae) rotate relative to the stars (in our galaxy) we can see in the sky?
gpt
Other galaxies are as "fixed" in the sky as the stars are. The galaxies are of course moving -- most of them away from us, and all of them very very fast -- but their movement isn't noticeable within the span of human civilization. The galaxy M31, for instance, is called the Andromeda Galaxy because it's in the constellation Andromeda. It's always been there, in that spot, and always will...moving into the far future, it will be the stars making up the constellation that will drift away before M31 does.

Here's an analogy: put an object in the center of the room and pretend it's the sun. Now walk around the object, pretending you're the Earth. At one point, the "sun" will be in front of the door, then later it will be in front of the couch, then the window, then the TV, and so on. Those things in the background are the stars or constellations that the sun moves through over the course of the year (the series of constellations that the sun passes through are called the zodiac). But if there's a window in the room, you are able to see a mountain fifty miles away. That's a galaxy. The mountain is *always* going to be in the window...it won't be "in" the couch or the TV.