I was reading an article in the NYT about the Mayans and the 2012 thing.  The Mayans thought that time ran in a loop.  I think some of string theory says that some of the dimensions could be loops, so this could be possible.  Maybe time is a giant loop, the big bang could be the beginning and then at some point in the future the universe could condense to a small point and the big bang would happen again.  One of the most interesting questions about time is why we only travel through it one direction, while we can travel freely in both directions in all the other dimensions.  I suggested before that maybe its just that our brains are unable to comprehend time all at once so we perceive it as flowing smoothly in one direction.  But if time is a giant loop, maybe it could also be that we can only spin around that loop in one direction.  Like how water going down a drain always goes one direction in the northern hemisphere and the other direction in the southern hemisphere, maybe time can only go in one direction around this loop.  Just an idea.