A lot of empty space
The closest galaxy, Andromeda, to ours, the Milky Way, is about 2.5 million light years away. Now, that’s pretty far, but it’s also moving at a rate of over 110 kilometers per second our way. In about 4.5 billion years, our galaxies will collide to create a super-galaxy we’re calling The Milky Andromeda.
If you’re concerned that our planet will crash into another from Andromeda, don’t be. Our galaxies are so spacious and empty that there’s a very minuscule chance of collision. Oh, yeah, and also, that’ll be about 180 million generations after us, so that’s a problem they’ll have to worry about, not us.