Today we are working on the idea that there was a big bang about 13 billions years ago, and the universe has been expanding from this big bang, ever since. 

Recent experiments seem to show that the universe is actually expanding faster than we initially thought. In fact the universe is actually accelerating in its expansion. There are some people who doubt these results and think they may be wrong, but for now we are working on the idea that the interpretation of the results is correct and we really are in a universe which has an accelerating expansion. Cool.

This causes a bit of a problem though. In a previous post I mentioned Newton's second law. This law basically says that to accelerate something you have to be giving it a shove, thre has to be a force. So the question then arises as to what is actually giving the universe a shove? If it is accelerating then some force must be in play.