Its true, time travel to the past seems an unreal possibility…however, time travel to the future makes intuitive sense even without invoking wormholes, etc. You do have to reference relativity.
We do it all the time when we accelerate to some higher speed than everyone else (air travel). We are then in slower time mode than everyone sitting on the ground and thus we make a slight leap into the future. Yes?
I’m traveling into the future right now, sitting on my couch. (1:1 ratio)
I don’t mean to be a nay-sayer, but it looks Cecil doesn’t have a solid handle on this time travel causality thing. If we can travel to the future, then back to the present, that enables us to travel to the past. What would prevent someone from the future going to the past through that same wormhole? If they could, then our present is their past. Creating this kind of time machine would enable you to travel to any point in the past after the machine was invented.
So, clearly we can’t make causality problems right now, but if we invented a time machine, we could cause it in the future.
Since Einstein, the only logically consistant view of “time” has been this: Every moment has existed and exists forever. You yesterday is just as real right “now” as is the moment Caesar was killed.
Thus, even with time travel, you could not change anything. If you “went back” to when your father was a child, you could not kill him (engendering paradox). If you “went back”, it means that you were already there. And you didn’t kill your father-to-be.
Steven Goldberg (AKA Estes)
That brings up an interesting metaphysical question: If every moment exists, then in sense is everyone and everything that has ever lived still alive?
That sounds like Stephen Hawking’s “Arrow of Time” theory which makes sense.
So, where does a person’s consciousness reside? I think it is here today: January 11, 2008 at 1:27pm.
Where is my consciousness from June 14, 1987 at 1:11pm?
To which column does this refer?
There have been hundreds of logically consistent view of time that have been proposed in the last hundred years. They are wildly at odds with one another. The majority of scientists may have a preference for one or another but there is no mathematical or physical proof that can be given to distinguish among them (or at least the non-crazy ones) and no philosophical reason that requires the grandfather paradox to be true or not true.
There are hundreds of books that talk about various theories of time, scientific attempts to make sense of time, and philosophical and literary speculations about the nature of time.
Paul Nahin’s Time Machines: Time Travel in Physics, Metaphysics, and Science Fiction is probably the classic book on the subject, an attempt to look at every major variation. It’s been out in several editions so you can ignore the high price at Amazon. It is not the clearest or best written book but it probably covers the most ground.
A more recent book by a scientist who is also a good writer is Time: A Traveler’s Guide, by Clifford A. Pickover.
So new that while I bought it, I haven’t had a chance to read it yet, but the reviews have been great is The New Time Travelers: A Journey to the Frontiers of Physics, by David Toomey, which supposedly covers the very latest theories.
Any of these books should shatter any notion that there is only one view of time or that anyone agrees on any answer.
I disagree.
(Sorry, couldn’t help it)
Almost certainly. Thanks.
And so, Caesar was unavoidably approaching a preexisting moment in the same way he might have approached a boat waiting for him at a pier?
Likewise, if I were to go back to the afternoon before my Tequila bender that ended in a scuzzy hotel room snorting crank while one of the girls lay passed out on the bed, I would only be able to relive it and not change anything since I had already been there and done that?
In addition to the quantum approach Cecil describes in the column, there is also another approach possible via General Relativity, given in Tipler’s “Rotating Cylinders and the Possibility of Global Causality Violation”. It is limited in that you can’t to back to a time before the time machine was built, and the engineering problems are at the “godlike” level, but the math seems to work.
There is always Larry Niven’s theory: if someone ever invents a time machine, then, eventually, some joker will use it to stop it from being invented. A somewhat less pleasant version occurs in William Tenn’s “It Ends with a Flicker”.
We had two threads on the same subject, so I’ve merged them into one.
bibliophage
moderator CCC
There is no real evidence that time travelers are not here now, but saying that proves time travel is not possible doesn’t make sense.
Maybe they aren’t here because humans don’t have long to go, so there aren’t any of “them” to be here. Maybe they aren’t here because there is more interesting stuff happening over there.
Any visitors from the future would have to go to absurd lengths to not have any impact whatsover on us, which would mean no interaction, so maybe we’re in “view only” mode for them.
Maybe they are god.
Doc Brown asked me to say that we’ve all got it wrong. But he says teh maths is too much for us to understand just yet.
[ul]
[li]There is always the route taken by “Superman” comics when I was a kid. You can go into the past, but if you try to change it, Murphy’s Law will stop you every time.[/li][li]C. S. Lewis describes a story he once read, but could not identify, about a time traveler who found that raindrops affected him like machine-gun bullets, because nothing in the past could be changed.[/li][li]I’m not sure what the “god” reference above is meant to signify, but it is small-o orthodox Christian doctrine that Time is one of the things that God created, and He is outside of it.[/li][/ul]
The reason you can’t use the wormhole to travel in the past is because the wormhole didn’t exist in the past. No matter what time you went through the “enter to the past” side of the wormhole you couldn’t go back further than when the “enter to the future” side of the wormhole had been built. You wouldn’t have an exit. Likewise, if 45 years from now someone destroys the “exit to the future” side of the wormhole you couldn’t travel that far into the future via the wormhole.
(I can see Phillip K. Dick warming up his pen for a stroy of a guy who goes into the future to destroy the wormhole that prevents him from going in the past to incite the apocolypse in the present, starring Ben Affleck.)
Cecil skips over it but there would be a far easier, if not more time consuming, to create a exit to the wormhole that is actually in the future. Bring it within the gravitational field of a more dense planet. Gravity affects time, the less gravity the faster time progresses. So you put one wormhole in the vacuum of space where gravity has little affect on it, and you put the other over by jupiter, or some other large dense planet. Wait for 10 years to pass, then fetch both wormholes back to earth. The wormhole in space will only have aged like 5 years and the wormhole from jupiter will have aged like 20 (speaking in general theory not specifics). And there you have your time-wormholes, without the pesky trouble of having to speed something up to lightspeed.
Sorry to double post but I wanted to respond to this and I couldn’t figure out how edit my previous post to include it. This isn’t a doctrine limited to Christian faith, but pretty much all religions that believe in the existence of a “creator.” Said “creator” would need to exist outside of time and thus be eternal or else it begets the question of who created this creator. In order to solve the problem of infinate regress there needs to be something that exists outside the jurisdiction of the physical boundry of time.
The reason is entropy-chemical reactions don’t run backwards, and humans don’t get young. The past destroys itself so that the present can exist. think about it-the atoms making up your body were once part of something else. ergo, you cannot visit the past, because it doesn’t exits anymore. Time’s arrow has one direction only-in the direction of increasing entropy.