Question: is it possible for the big bang to happen again and if so when and how and why?

Edward Bovill answered on 20 Mar 2013:

It is possible that the big bang might happen again.
There is a theory that says that the universe is expanding away from us all the time out from the point where the Big Bang happened. However, one day gravity will cause the expansion to slow down and the stars and galaxies will start falling back towards the same point in space. All the matter in the universe will be squashed back together at this one point – like a reverse big bang! After a while another Big bang will happen and the whole process will repeat itself.
We don’t know if this will happen yet – there are other theories that say that the universe will continue expanding forever, or that it will get to a certain size and stay there. We just can’t say for sure yet which will happen.