Undergrad Interstellar Travel vs Universe Expansion: Is Andromeda Reachable?

[kent davidge]

I read in a so called sci-fi website from my country that as the universe is expanding we may not be able to get to certain galaxies in a possible interstellar travel. That information seems ok for me. But then there was a comment by a reader concluding from the website post that there is coming a time when we won't be able to get to any galaxy, even Andromeda, he says.

I guess that's not valid for Andromeda or other nearby galaxies as I have the impression that the universe expansion is felt in large distances only, and because it's said that the Milky Way is on a collision route with Andromeda...

I just want to confirm if my thought is correct...

 

[phinds]

The expansion is only for groups larger than a galactic cluster so you are correct that it wouldn't be true even for Andromeda although that point is moot since Andromeda is going to collide with the Milky Way LONG before it becomes true that our local cluster is the only stuff in the observable universe. So yes, you are correct.