dave blacker wrote:
If the Universe is expanding, then all the galaxies must be moving
away from one another.

In general, yes. Imagine a load of black dots on an elastic sheet that
is being stretched....

So how come there are such things as 'colliding galaxies'?

Because the expansion is not the *only thing happening. In your mind,
turn those black dots into (live) ants...

(OK, I know it's a lousy analogy, but it ought to do the trick! g)



Best,
Stephen

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