See, everything that ever could possibly have happened, in the entire history of the universe right from the Big Bang up until now, _did_ happen -- somewhere. And _every_ possible difference means a different universe. Not just if Napoleon lost at Waterloo, or won, or whatever he didn't do here; what does Napoleon matter to the _universe_, anyway? Betelgeuse doesn't give a flying damn for all of Europe, past, present, or future. But every single atom or particle or whatever, whenever it had a chance to do something -- break up or stay together, or move one direction instead of another, whatever -- it did _all_ of them, but all in different universes. They didn't branch off, either -- all the universes were always there, there just wasn't any difference between them until this particular event came along. And that means that there are millions and millions of identical universes, too, where the differences haven't happened yet. There's an infinite number of universes, more than that an infinity of infinities, I mean you can't really comprehend it. If you think you're close then multiply that a few zillion times -- everything is out there.