We all love time travel, judging from how many books and movies use it. Time travel is certainly a great plotting device. But is time travel plausible? Is it fair game for SCIENCE-based SF -- or is it a trope?I’m limiting this post to travel backwards in time. Many time-travel stories revisit a past event, whether to view, alter, or safeguard the event. And most forward-traveling stories involve a return to the time traveler’s present.
The case against travel to the past as real physics? One (and a biggie): Travel backward in time eliminates causality. Two (also known as the Fermi paradox of time travel): If travel to the past is possible, then why aren’t we, at least near pivotal historical events, knee-deep in time travelers?
IMO, the best argument for the feasibility of time travel is the symmetry of basic physical laws. The equations (of, say, ballistics) work equally well whether time flows forward or back. Hence, some would argue, the so-called arrow of time is strictly perceptual. Hence (here comes the leap of faith) time is just another dimension that – if we but learn how – one can traverse.
Of course those direction-of-time-symmetric equations can’t be solved exactly for more than one or two of anything. Deal with lots of molecules – say, cream poured into a cup of coffee – and anyone can see whether film of the event runs forward or backward. Hence, I find the symmetry argument unconvincing.
So that’s three strikes. Yer ... a trope. Now excuse me while I TiVo The Sarah Connor Chronicles.
(And yes, I’ve perpetrated a couple time-travel stories [anyone out there know which?]. As I said, we all love time travel stories.)