Andromeda Collision VS Expansion

[newrd]

Hi Folks,
I've read that by the time mankind is ready for intergalactic travel, our nearest galactic neighbour will be too far to even travel to. But I've also read that Andromeda is on a collision course with the Milky Way. Which is correct? And if the universe is expanding and everything is moving apart, how come we're not moving away from Andromeda?
Thanks!

 

[Ibix]

I've read that by the time mankind is ready for intergalactic travel, our nearest galactic neighbour will be too far to even travel to.

Where did you read that? Quoting sources helps us help you - if you've got something wrong, we can see if it's because you've misunderstood something, or if the author of what you read misrepresented something.

I tend to suspect whatever you were reading was a bit fanciful. "When we'll be ready for intergalactic travel" simply isn't something we can know. But anyway, nearby galaxies aren't moving that fast on the kind of time scale we're likely to be around.

But I've also read that Andromeda is on a collision course with the Milky Way.

Andromeda is certainly coming towards us.

And if the universe is expanding and everything is moving apart, how come we're not moving away from Andromeda?

On small scales (less than a hundred million light years), plenty of stuff is moving in all directions relative to us. It's only beyond that kind of distance that you see the overall picture of "everything moving away from us". This is, basically, because the "speed" with which things recede from us grows with distance. At low distances, random velocities of the galaxies can be larger than the average expansion motion.

 

[kimbyd]

Hi Folks,
I've read that by the time mankind is ready for intergalactic travel, our nearest galactic neighbour will be too far to even travel to. But I've also read that Andromeda is on a collision course with the Milky Way. Which is correct? And if the universe is expanding and everything is moving apart, how come we're not moving away from Andromeda?
Thanks!

Honestly, there's just no possible way to make any statement about when intergalactic travel may or may not happen.

Interstellar travel looks to be so unimaginably difficult that it might well be impossible. We have no idea when interstellar travel might happen (if ever), let alone intergalactic travel. You just can't put a timeline on something when you have no idea how it can ever occur.

 

[newrd]

Thanks guys, Ibix your answer that its on a small scale explained it perfectly, cheers!