system
Given the following post, respond as if you're commenting on Reddit:
human
If The Big Bang happened from a single point, how is it The Milky Way and Andromeda on a collision course?

The way I understand The Big Bang is from a single point, and the universe is expanding from a single point out. So how can 2 large objects like galaxies collide with one another if we are all following angles out from origin. Shouldn't any of that stuff happen in the universes infancy?  

I think of it as a ripple of water from something falling in. That ripple expands out, never colliding with itself, just other ripples.
gpt
Two misconceptions here. The Big Bang didn't expand from a single point, it expanded everywhere at once. Because of the above, things aren't expanding away from a centre, they are expanding away from each other. 

For (relatively) small scales like galactic scales, gravitational forces dominate and there is little to no expansion.