[QUOTE=xtisme]
Dude…you mistake me for someone who made this theory. It’s not MY theory…I just happen to like it. Afaik there are no reputable physicists who claim a herring is created every time we time travel (or every time the gods fart). Conversely, while this may not be the current main stream view (depends…is M Theory mainstream?), it’s not exactly on par with, say, creationism.
[/QUOTE]
Fair enough; why do you like it more?
(And as far as I know, time travel (as it is normally thought of) is still squarely in the realm of fiction. The question is which is better, more plausible/less impossible fiction.)
[QUOTE=xtisme]
Because I’m not a physicist, nor do I play one on TV…and I LIKE the theory, what little I grasp of it. It is simple and elegant (though I admit I haven’t represented it well here…and I have no idea if the multi-universe theory corresponds to time travel in the way I laid it out…my guess is it doesn’t).
[/QUOTE]
Why is it simpler or more elegant to create a whole new universe and jump to it’s past, than to jump to your own universe’s past?
[QUOTE=xtisme]
You are trying to reason this from a view point as if the universe HAS a point. What does it give you? What does water expanding when freezing give you that water contracting doesn’t? Why is it wet? What does gravity give you? Why don’t humans have tails or horses horns in the center of their foreheads?
-XT
[/QUOTE]
Um, I’m not trying to reason as though it has a point. I’m trying to use reason to find the least silly theory. And you have to be doing that if you’re going to compare theories at all.
[QUOTE=Polerius]
Well, multiple universes, if they are correct (and they seem more like science fiction than science to me), give you a way that makes time travel to the past “feasible” in some sense.
Staying in our universe and “re-writing history” is, as I’ve tried to explain in the OP and later posts, not possible for anyone that is living within our spacetime continuum.
Your ‘metatime’ concept might help allow time travel to the past, but it has as much validity (and lack of evidence) as the multiverse idea.
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There’s no evidence for any of this time-travel stuff, as far as I know. It’s just mental entertainment. And, I did not see where you convincingly argued against changing the past. I mean, that’s usually the point of time travel, isn’t it? Changing the past? So what if you didn’t meet your future self as a kid this time around. Things be different in take two.
[QUOTE=Polerius]
Even then, I see problems with it
Even if any outside entities could alter our trajectory through spacetime, so that in their frame of existence they could change your 1995 experience from eating a hot dog on June 5 1995 to eating a burger on that day (much like an artist can delete a line he drew and draw it again a bit differently), there are problems with this:
- It raises serious questions about “free will”, i.e. are our everyday actions remote-controlled by entities outside our universe?
[/QUOTE]
I don’t see why extrauniversal entities imply you don’t have free will any more than intraversal (ie: normal) entities in the universe do. I can grab you and stop you from moving; does that mean you lack free will? No; it just means that some other agent is interfering with your actions. The same would theoretically apply to extrauniversal entities that might mess with you as well.
Now, all extrauniversal interference aside, free will is an interesting question when you talk about time travel regardless; presumably, yourself-of-the-past doesn’t have free will; the past is as a rule locked into whatever happened. So, if there’s free will happening, it’s happening only on the ‘front edge’ of the space-time continuum, which would correspond to the ‘present time’. This would therefore imply that the space-time continuum was being created as it went along. This also would imply that every time somebody traveled to the past, they’d “move back” the “print head” 
of time, re-engaging free will at the point in time they arrived at, and thus, essentially priming all of future time to unravel ahead of it preparatory to being rewritten into a new version that now has the arrived time-traveler added to it. (Time-traveling forward would involve ‘hopping off’ the space-time continuum, allowing the ‘present’ to advance, creating history behind it, until it reached the destination time, and re-adding the time-traveler to the continuum at that point, to join in with the free will that’s creating the ‘present time’.)
If there’s no free will, then there are two possibilities: either it’s about the same as described above, except all the agents creating history in the present are just going through free-will-less actions like robots, or things are pre-determined and all time-travel is pre-accounted for, so all trips to the past that could ever happen are already in the time stream the whole time, and none of them ever actually change the past or make contradictions (this is the “Bill and Ted” model). In this case, there’s no meaningful ‘print head’ or ‘present’; all history always exists, and our perception of a present or the passage of time is just an illusion, an impotent artifact of the system.
[QUOTE=Polaris]
2) Even if entities outside our space-time continuum could change your trajectory through space-time, that does not mean that agents inside our space-time continuum could do they same thing to their own space-time trajectories (and the space-time trajectories of people they interact with)
- Even if entities outside our space-time continuum could change your trajectory through space-time, that does not mean they could “invent a time machine”, because any changes that the outer entities make (even if they make self-consistent time travel loops), would prevent you from building a machine to travel to wherever/whenever you wanted to and do whatever you wanted to there (which goes back to the point in (1), i.e. whether our actions are remote-controlled by the outer entities).
So, the time travel machine you may build will not be a traveling machine in any meaningful way.
As I mentioned above, we, on the outside, can alter the timeline of events in a movie, but that does not mean that any character in any movie can change the timeline of the movie they are in.
You can remake the Matrix, but Neo in the Matrix cannot change the sequence of events in his own movie.
[/QUOTE]
I think the premise of time travel -any model of it, presupposes that you can ‘pop yourself off’ the space time continuum at one point, and ‘drop yourself back on’ at another point, without actually passing through all the times inbetween. (You’d instantly smack into yourself if you didn’t pop off, of course.) I think this fact resolves all of your complaints here all on its own.
