According to the “many worlds” theory of quantum mechanics (if I'm understanding it rightly), an alternate universe is spun off, in all its multitudinous glory, whenever a single electron changes its energy state. In other words, there is an entire separate universe created to embody every conceivable quantum state of this universe. And these universes go on to create separate world-lines for their fragmenting realities as well.
That’s the theory, anyway. Unfortunately it remains a theory, because to date we’ve no empirical proof. We don’t have a “timer” that lets us pop from one world-line to the next, a la Sliders. And one of the theory’s main postulates (as I understand it; correct me if I’m wrong), is that there’s no way the “walls” separating this world from the others can be breached.
But hang on -- aren’t the amount of decoherent histories thusly created infinite (or at least close enough for all intents and purposes)? And in an infinity of possibilities, aren’t all permutations by definition possible? And, if so, doesn’t that mean that a finite number (at least one, possibly n) of alternate world-lines have to be somehow connected?
Works for me. (And the reason I’m posting it is because it isn’t my idea. My twelve year-old son came up with it. Which definitely makes me feel a little chesty in the Daddy Department ...)