But if the reversal were perfect, there wouldn't be any effect, right? I mean, going back in time would be rewinding, and you wouldn't remember that you time-traveled and you would relive the reversed years almost precisely the same as they had gone the first time.
Not quite. The way that it would work, you would remove yourself from the cause-effect chain. While everything else rewinds, your cause-effect chain goes forwards. In other words, as the world around you gets younger, you still get older.
OH ok! So I stand by my earlier post, traveling back in time a few years would result in teleporting your bones out of your prior self's body.
You said, "...we would allow one thing to go forward while the rest of the universe goes backwards." Would not those that are "going backwards" not realize they are going backwards? It seems to me that from their perspective time would be going forward.
This sounds right to me; if I used this method of time travel I would see stuff rewinding around me but me, or a bubble around me, would be 'normal time'. Well' that's assuming I can see anything at all. Some backwards-traveling light would probably hit my eyes but who knows whether it would get absorbed right?
I think I understand this idea well enough to say a bit about whether it's physically plausible now.
The closest thing to this method that I've actually heard about is the idea that all antimatter is simply matter which is currently traveling backwards in time. So what we perceive as matter and antimatter meeting each other and cancelling out in a burst of energy is, in reality, a piece of matter reversing the direction in which it's travelling. For some reason, forward-traveling matter
generates a burst of energy when it's turned backwards in time whereas 'catching' antimatter and turning it back forwards
requires energy (we perceive this as a high-energy collision producing a matter-antimatter pair). This is fortunate because otherwise time travel would be a source of free energy! And free energy would (obviously?) unravel spacetime.
Anyway, this time travel method is strange because the first step in accomplishing it is building the receiving machine, and using a huge burst of energy to produce a matter copy of yourself and an antimatter copy of yourself. You then keep the antimatter copy of yourself isolated from any real matter for the duration of its time travel, and then at the end you annihilate yourself using this copy, which is the 'turning around' event.
The existence of the antimatter pair essentially 'balances out' the surplus of you's for the duration of any overlap, which makes a bit more sense to me than the matter being moved to a different location by the time travel.
Naturally we don't know how to create very much antimatter at a time, and creating matter and antimatter duplicates of yourself is no easier than creating, say, an antimatter Klingon, or anything else which doesn't literally come from the future. So for all this to actually retrieve a copy of you from the future, rather than just your best guess at what you-from-the-future is like, the antimatter would have to somehow remain in a state of quantum superposition throughout the whole trip; like Schroedinger's cat only from the future. Looking into the box makes it impossible for the information to have come from the future so prevents time travel.
Since the matter copy of yourself carries the same information as the antimatter copy (at least at the moment of creation), this has a very interesting consequence! The copy of you who travels back in time
also has to remain in an isolated box, immune to all measurement, after being created. Only after the original is destroyed or 'turned around' in time to begin the journey could the time traveler actually come out of isolation! Therefore the antimatter method doesn't allow for the time traveler to actually see the past. Instead he just gets some time to himself to think, in a box insulating him from the rest of the Universe.
