I think I've figured out a way that time travel could actually work. Of course, we'd need an
ansible first, but all
sci-fi novels seem to have those, so I think we can safely assume they'll be invented by the time
time travel is a real
necessity.
Erwin Schroedinger theorized that the universe is infinite. As such, every possible scenario, ever imagained by anyone, has been played out somewhere. So, given this, we can assume that there are infinite worlds identical to earth, only they happened to be offset by one second. Or two. Or three. And so on.
So, we just hop into our ansible-enabled spaceship and scan for the earth which happens to be offset such that the present is equal to the time we want to visit. Say, the fall of the Roman Empire. We find a world the same as earth, only it happened to be formed a few centuries later, so it's still at that point in history. We then open a material ansible connection to it, zip on over there, and there we are!
We don't even need to worry about the time traveler's worst nightmare, changing the past, because we have our own world safe and sound, several thousand lightyears away. Furthermore, if we stay too long, we can return not to own world of birth, but to a world identical the one of our birth, including the event of our time traveling. Only set back to the point where we would arrive say, five minutes after we left. It would be handy if you don't want to miss, like, tonight's episode of Futurama.
In fact, you could even go back to a world where some minor thing is different. Like, a world where All Your Base Are Belong To Us never came to the public attention.
Kind of selfish of us though, to leave our loved ones back home on the original world, never to see us again. It evens out though, because while our loved ones on the original world never see us again, neither do the ones on the infinite number of other worlds, with the exception of the one that we do return to.
It sort of gives you a sense of just how insignificant you are, and why human cloning would be a idea. Imagine that, time travels proves that cloning is a Bad Thing. More at 11.