I’ve always been bugged by the concept of time travel. It is so preposterous to me that its really hard for me to enjoy stories that use it, even if they’re otherwise interesting.
Off the top of my head I can think of the Terminator movies, Planet of the Apes, and many episodes of Star Trek. In both case it seems to me that the future justifies itself by its influence on the past. I can think of so many other logic problems that I don’t understand how the concept has not been disposed of already.
I still hear from time to time about people saying time travel would be scientifically possible. I only need one word: causality. I don’t know of a single story that uses the concept of time travel logically. Of course you can only hope so much out of work of fictions, but how come the concept is still going around like it has any validity.
Does anyone have a valid theory of how time travel would be possible? An explanation as to why it can’t be ruled out would be fine too. Do you think time travel belongs in the same category with cold fusion and Ether?
In any case, that just confirms my belief. I honestly tried to find it with a search, but I guess I don’t know how to use it 'cause I didn’t even come close to something that was relevant.
In any case, this is still a valid thread (even if a similar one already exists). I included the original link in case you weren’t aware of it. I wasn’t trying to nip this discussion in the bud.
In direct response to your OP, I think the answer to your final question is “yes.”
Yes. Causality is lost if you have time travel. That’s one reason why scientists don’t like the concept. It’s also a reason why science fiction authors love the concept.
However, there are conditions where time travel seem to have a solid theoretical basis, though in order to take advantage of the conditions would be economically unfeasable.
There are many first-class time travel books and stories that handle the paradoxes well; your mistake is going to movies instead of the literature. Off the top of my head, I’d suggest the stories “Hobson’s Choice” or “The Men Who Murdered Mohammed” by Alfred Bester, “The Weed of Time Bears Bitter Fruit” by George Alec Effinger, all of which give explanations ranging from logical to fanciful for why the paradoxes don’t occur. David Gerrold’s THE MAN WHO FOLDED HIMSELF probably covers the problems and paradoxes with the most rigor. Another good choice is MILLENNEUM by John Varley, with serves up a good adventure that takes into account the possible paradoxes (don’t see the movie, though, which is really second rate).
You also should read “Sundials” in the next issue of ABORIGINAL SF.
I once had an excellent SF novel about time travel. Unfortunately, I can’t recall the title or author. (My roommate loaned it to someone who never returned it. Grrr…)
In it, every time someone went back in time, they created a separate branch of reality. But, if they came prepared, they could create a gateway between the two realities, even across time.
It started in the 1970’s, with the US still fighting WWII. President J.F. Kennedy, and his advisors determine that someone with time travel techology helped the Germans in the 1930’s with rocketry and electronics. Finding some of the time travel equipment, a team goes back to help the Allies. But once back, they find that they can’t return to the 1970’s they knew.
AWB, I don’t recall reading the specific story you speak of, but something with a similar plot is Lightning by Dean Koontz, who comes up with a neat wrinkle. In his book, the Nazis develop time travel, but only to (and from) the future.
Saying “causality would be broken!” as a reason why time travel can not take place is circular argumentation. Causality and forward movement through time are two sides of the same coin. It would be like saying “you can’t time travel because that would be breaking time!”
Relativity shows that anything with mass necessarily moves forward through time as a function of having mass – in normal space-time. The ‘normal space-time’ is the important part. Theoretical speculation and calculations show that it may be possible, with the right amount of mass and the right type of mass in the right configuration to twist space-time so much that you travel through the ‘wormhole’ to a point in space-time that is actually pastward (same place but earlier) of where you once were in space-time.
Thus, it would be, in fact, time travel (through spatial travel in twisted-up time-space). And thus, causality can be broken. Causality would be twisted up as much as the wormhole has twisted up space-time. Just as a line in twisted space-time can become a loop, so too can causality become loop (the classic time-loop paradox).
Another good S/F book about this is The TimeGod by L. E. Modesitt Jr.
Deals with time travel from the point that the characters can’t travel back and forth on their timeline, but can visit other planets at different points in time…to collect different technology…the book is so-so, but I liked the concept behind it.
<i>I haven’t lost my mind, I have a tape backup around somewhere.</i>
RealityChuck gives a good start at a bibliography but missed a couple: one that might be the best paradox story ever, All You Zombies by Robert Heinlein, and one of the best-written, The Garden of Forking Paths by Jorge Luis Borges.
Bob the Random Expert
“If we don’t have the answer, we’ll make one up.”
Well, not totally. But to avoid that, you need to accept one of two principles, neither of which are very acceptable scientifically. You could accept that all events are predestined, thus time-travel will only result in previously established causes. You can also accept that there is some sort of magical causality protecting nature of the universe that protects us from our murderous posterity.
Of course these ideas don’t generally fly to well.
It seems that every vaguely reasonable time travel theory that I have heard revolves around wormholes, and they are all major long shots.
Carl Sagan threw a time travel idea out in the '80s, that is conceptually fairly simple. Of course it sure as heck isn’t simple in the practical sense.
Here’s Sagan’s idea
First you need a stable wormhole that somehow you can travel trough without getting ripped to pieces. That’s a pretty severe condition as it is, that probably can’t happen.
Second, you need to have the ability to move one of the ends of a wormhole in circles at close to the speed of light. Your pilot enters the wormhole at the non-moving end and returns at the moving end. If the distance between the two ends of a wormhole are close enough, the pilot could emerge at an earlier time and get back to his starting point before he started.
Of course Sagan didn’t even begin to suggest a way of moving a wormhole at close to the speed of light. This would be comparable to moving a black hole around at nearly the speed of light.
I also forgot one of the most memorable of all (with the most ummemorable title, since everyone asks about it): Ray Bradbury’s “A Sound of Thunder.”
Another great Time Travel (sort of) is Ken Grimwood’s REPLAY, which takes the question “What if you could live your life over?” and comes up with some surprising answers.
“The Weed of Crime Bears Bitter Fruit” forms the first part of THE NICK OF TIME or THE BIRD OF TIME, I forget which one. And I wrote both of them. A long time ago.
(signed) “Time is the simplest thing/unless your short-term memory has been misplaced”
I believe Stephen Hawking suggested time travel must be impossible (now and forever) because if it weren’t, we’d be seeing a lot of tourists, explorers, etc. from the future now, in our present.
You can’t logic your way through time travel. Just because we don’t appear to see time travelers, that doesn’t mean time travel is impossible.
It probably is, but that doesn’t mean we can’t write and read stories about it. There’s no reason not to write a “first landing on the moon” story, either, just because we’ve been there and done that. Make it an alternate universe.
Speaking of which, one solution of a bit of Einstein says that parallel universes MUST exist. That’s the good news. The bad news is that we can’t get to them.
Much like the airport at rush hour.
(signed) “I have enough trouble in three dimensions, especially if there is no escalator”