Of course I can't say any of what I say is true but the only way a theory can be properly explored is if you assume it is truth for a while. Have you seen sub atomic particles? Yet we take the theory that they exist as truth. If we didn't do that sometimes, then all scientific research would be without direction and pointless.
Heh, there's a slight difference between subatomic particles and alternate realities
From a scientific standpoint, the problem with alternate dimensions is falsifiability;
Subatomic particles are falsifiable; testable predictions can be made that must be satisfied if subatomic particles exist, and finding a result that contradicts the theory negates it. They so far have survived testing, hence it's fine to take them as fact (at least until a better explanation comes along).
Alternate dimensions however are not falsifiable. There are
no known testable predictions that can be made that negate alternate universes. Equally, there are no known phenomena that require alternate universes to exist. As such alt. universes falls into the realm of metaphysics (just like what happened before the big bang, whether or not god exists, etc.).
I think this is what Twiggie is getting at, and if so, I happen to agree. As it stands, the idea of multiple dimensions, while nifty, can't really be used as justification for time travel (or indeed anything), and it can get somewhat silly sometimes. That being said, if someone comes up with a falsifiable theory for alternate universes, well, onya son.