I know that there are several theories out there about how old the Universe is and how big, etc. I also know there are theories related to Mbranes (string theory?) that state that there are "pages" of universes that sit side by side (that's the easiest way for me to think of it) and that there are millions and millions of these "pages" of universes. My question is what twofold: 1. What are some of the current theories on where our Universe ends and related to that, what comes after the end of our Universe? 2. What are some of the current theories on Mbrane or string theory in terms of how these Universes line up? By this I mean, do physicists think the membranes or Universes sit one on top of another on top of another, etc. or are they "pages" sitting side by side by side making a blanket of Universes, so to speak? I also saw a physicists this weekend who theorized that the big bang, was really two of these universal membranes hitting each other, causing a fantastic release of energy and voila' our universe was born. My question would be, how do two membranes of "nothing" collide to cause "something?"