A few days left to check this film out...

[Darwinian]

Because gravity should be just as strong as all the other forces. This is one of the problems with trying to come up with the theory of everything.

At the moment the two theories which explain the universe on the very large scale, general relativity and on the very small, quantum mechanics don't get on very well with each other and one of the main problems is that of gravity. It 'should' be just as strong as the other forces but it is not. That's the mystery.

NO, the universe is not expanding into space. I agree that it's a very tricky concept to get your head around but it is simply the space itself that is expanding. i.e. the distances between points that are getting larger. Space, by definition, cannot be expanding into anything as it is space itself.

It's easier to understand the other way around, in fact I put this theory on the science forums with no real objection. Instead of space expanding, imagine that all the matter in the universe is shrinking. So, from our point of view, everything is getting further and further away from everything else.