Gravity

[lukman]

how gravity from distant matters (galaxies etc) interact to each other where they are separated by distance of million/billion of light years, then space in the universe is expanding FTL, and gravity only travel at speed of light. I have seen a TV show once illustrate how gravity work like two person exchaning ball or sort of, how can gravity exchange happens at vast distance? So that big crunch by gravity pull will not possible. :? ahh why gravity is never to be understood.

 

[BoJangles2]

Interesting question.

The program you’re thinking of is the Elegant Universe hosted by Brain Greene.

If expantion as caused by dark energy is correct then there is a point at which matter stops interacting through gravity on other matter in the universe, at that point you will lose all reference to that matter due to a cosmological horizon caused by the finite speed at which these affects travel as explained by relativity.

As for the big crunch, its only one of the possible ultimate fates of the universe, at the moment I believe it’s the less accepted model.

Ps I'm not sure if my terminology was 100% correct, though if you’re lucky someone else may contribute and extrapolate in more detail.

You might want to check out the lectures and documentaries thread, it has a wealth of information that may help you in your quest.