[quote=thewizardguy]
Or, we could be simple. Time travel by Tardis only works in the Doctor Who Universe, and outside they simply teleport. Due to Dimensional Rules and stuffs. Also, time travel in the Doctor Who Universe functions according to Doctor Who rules, which basically means I get to make up whatever I feel like applying to the situation.
[/quote]

That too, but I hadn't taken that into account. I have this annoying idea stuck in my head that all the universes would have the same physics and scientific truths as our own, though I know that isn't true as you could change anything.