Universe expanding

[ogwen]

Theres been something I've been wonderin about for a while now and though it might be a silly question i hope someone can answer it .

The scientists say our universe is rapidly expanding and that galaxies are moving further apart from each other, so how come they also know that in millions of yrs time our galaxy is going to colide with another (andromeda I think.)? I can't quite work it out, though i might just be being dense :P

[shadowx]

On average galaxies are moving apart, but due to the nature of the universe and the immense number of objects in it sometimes things will and do collide. Think of it like a grenade exploding, although the shrapnel is generally expanding and moving away from both each other and the point of the explosion sometimes two bits of shrapnel might hit each other.

It's sort of like that!

[ogwen]

hehe thats rather a good way of explaining it . Makes a lot of sense. Is it andromeda that will collide with the milky way by the way?

[shadowx]

It sure is!

But the timescales and distances are too big to even imagine!