> > If we found out that in about 500 years this was going to happen to our galaxy (that another galaxy was going to come crashing through it) what do you think would change?
>
> Nothing. If another galaxy crashed into the Milky Way, it's extremely doubtful it would affect life on this planet at all. In fact, the odds are strongly against ANY two stars colliding, let alone one colliding with our sun.

I may have over-estimated the effect of another galaxy hitting ours, but there are many ways we could be effected other than stars colliding (which wasn't what I was implying would happen in my original post anyways). I'd think that just the gravity involved would effect us a lot. If our galaxy has enough gravity to keep us orbiting around the center of it, how would doubling that gravity effect us? We're a pretty delicate species, and it wouldn't take a big orbit change to kill us. That's what it seems like to me, at least.