Just to clear up a quick point. The idea that there was no time before the big bang was proposed, and then dismissed by Stephen Hawkins. There are a number of theories about what occurred before the big bang, but the concept that there was no time is no longer one of those proposals. In modern physics time is viewed as essentially part of space. As Stephen Hawkins says, it seems silly to view space-time as any other shape than round. Where is the beginning and end of a circle? What about a sphere? What about the 4 dimensional equivalent of a sphere? (Although it's false to think of time as an interchangeable dimension like width, breadth and height).