Heh, I totally thought up the exact same scheme when I was writing fiction in high school, except that my '‘turns’ were only 500 years, and I had a ‘limiter’ that prevented any time travel trip that would generate a paradox.
For my thinking, multiple universe theory is ridiculous and unnecessary. Every time you time travel you have to create an entire new separate universe now? To what end? You can’t get back to your original one. It just lingers around to…what? To prevent paradoxes? How could it do that?
In the multiple universe theory, in the “new” universe your dude appears in the past out of nowhere, and then can kill his parents or whatever with impunity. If this is allowed in the new universe, why not let it happen in the old universe? It seems much more economical/likely to just rewrite over the one existing universe’s history than to leave piles of old ‘original copy’ universes scattered about behind you as you go.
Even if we ignore the lack of evidence for this, how is it possible that the action of an agent within one universe creates a whole new universe?
That’s a lot of power in the hands of all agents in each universe!
It’s almost like the characters in a book can, by some action, create a new book. I don’t think that is possible, because the characters are by definition part of the book. They can’t act “outside the book”. Similarly, we are part of or universe. Even if others exist, I don’t think it is possible for use to act “outside our universe”. We are part of the fabric of this universe.
(BTW, how do multi-verse proponents deal with the energy requirements in creating a whole new universe whenever you “branch out”?)
AFAIK, it looks like just another coordinate due to mathematical notation/convenience, but just because it appears in an equation in a fashion similar to the spatial coordinates does not mean that it is similar to a spatial coordinate in any real sense (i.e. in the sense that we can travel through it at will).
I could make a two-coordinate system consisting of a person’s net worth (in dollars) and weight (in kilograms), and plot the trajectory of each person on this two-dimensional plot. Most likely each person would have a unique trajectory in this two dimensional plot.
But, just because I put net worth in one coordinate and weight in another, it has no bearing on whether weight is in any physical sense “similar” to net worth.
I took physics in college but I’m not qualified to answer this. Here is a Wiki article on it if you are interested.
Well, there are an infinite number of them…that’s, well, a lot wouldn’t you say?
I’ve seen various theories…you need to keep in mind that if this theory is true not all (or even a large part) of the total energy in the system is in THIS universe. I’ve seen theories that say this ties into dark energy or the reason why gravity is such a weak force…but again, my own physics doesn’t go this far. I had a very tenuous grasp of even the easier aspects of GR/R let alone stuff like this way out on the bleeding edge.
Oh. I misunderheard you. I’m not sure I see your point. The universe has no purpose…it simply is. It has rules…but rules that are to no specific purpose. If the multi-verse theory is correct universes are constantly splitting off naturally. Why wouldn’t someone be able to manipulate those same rules to deliberately do it? Think of splitting an atom…isn’t that ‘a lot of power in the hands of each agent in each universe’ as well?
Right, but we could think up any sort of stupid useless rules to go along with our time-travel theory. (Every time you time travel, you spontaneously create…a herring! And two cans of spam. And to travel through time travel requires that you bring along… a shrubbery!) Any set of stupid rules is equally valid, as long as it’s not overly self-contradictory.
The real question is, why do you think that the multiple-universe model is a better model than, say, the Python model? What to multiple universes give you that, for example, simply staying in and overwriting history in the same universe does not?
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.
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).
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?
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.
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?
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 you 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.
Well, taking a piss on a wall is a bit different than splitting an atom to, right? Again, you are trying to assert something that SEEMS to you to make logical sense…when in fact logic has nothing much to do with it. The universe IS. It has rules, to be sure…but sometimes those rules don’t really follow logic. Simply look at quantum physics or R/GR…it’s fucking weird and extremely counter intuitive. Even Einstein didn’t grasp all of the implications of his own theory (for instance he never really liked the concept that the universe had a distinct starting point, that it wasn’t eternal)…and this is EINSTEIN we are talking about!
Again, I didn’t create this theory. I just happen to LIKE it…to me it’s elegant and it makes sense (what I grasp of it). That our universe is simply a grain of sand on a beach in a sea of other universes that are constantly being created (and perhaps destroyed)…that our universe is literally a bubble, a membrane between us and all those other universes, that the closer those universes are ‘physically’ to ours the closer they are to ours in a parallel fashion…and the further they are away the further they diverge from our own. I just like it.
Thing is, this IS real physics theory here not something XT made up. I mean, I’m flattered and all…but it’s hardly an original thought (on my part), nor do I take credit for even UNDERSTANDING it conceptually (let alone the math behind all this…and I was a math minor in college)…let alone inventing it.
Maybe one of those physics major 'dopers will wander in and give a better explaination…myself, my major was engineering, and while I took 3 years of physics in college and it barely touched on this stuff. And what little I DID know I have promptly forgotten in the last 25 odd years since I graduated (hell, I flushed most of that stuff out when I was done taking my finals).
(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.)
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?
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.
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.
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.
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.
shrug It captured my fancy I guess. I like the idea and it seems plausible to me, even if from a practical perspective we can never actually do anything about it. Sort of like the idea of quantum tunneling…I just like the concept.
I am not a physicist. However, afaik there is no bar in our current understanding of physics that precluded time travel. Some of my friends that ARE physicists talk about how they HOPE that there is some mechanism that DOES prevent it. They seem quite uncomfortable with the idea for some reason.
Paradox. You eliminate the possibility of paradox if you posit a branching of time. So…it’s more elegant.
Using straight reason one would conclude that the world works best using Newtonian physics and that quantum physics/R/GR is illogical. Sometimes straight reason doesn’t work very well.
Well, I can’t argue with that…but I won’t buy into it either.
Well, it does open up the possibility of you being obliterated entirely out of existence by some random time traveler…and it also opens up the possibility of you being ‘changed’ (as in, replaced by a different time[sub]2[/sub] you), which for some is not appreciably more comforting.
What paradox are you speaking of? The ‘kill your parents’ paradox? That’s no problem with overwriting because you just recognize you can never go back to the same ‘future’ you came from…which you can’t do in the multiple worlds model either.
As far as I can tell, the only difference between the multiple worlds model and the ‘overwrite’ model is that in the latter 1) you don’t end up with a spare, “the time travel didn’t work and he was annihilated” universe lying around (the original one), and 2) the new-universe creation takes place in-place, “conserving memory”. This only matters abstractly, as nobody is likely to be able to observe this. I don’t see any other differences between the models, and thus, no benifits to the ‘exponentially multiplying universes’ model, paradoxical or otherwise.
If this were actually true, we wouldn’t accept quantum physice/R/GR. Or do you think that scientists work themselves into an altered, irrational state in order to be able to accept these thories?
It IS true. Physicists accept quantum physics and the rest not because it’s intuitive (it’s not) but because it’s RIGHT. One of the reasons that most people on the planet don’t understand it is because much of it (even leaving aside the math) is counter intuitive…while Newtonian physics is something that is fairly easy to grasp (even the math isn’t that bad).
One huge difference between quantum physics/SR/GR, and the multiverse idea, is that AFAIK the former ideas, even though “weird” by normal human standards, were proven experimentally “soon” after they were proposed (a physicist can confirm how soon this happened), while the idea of a multiverse with universes coming into existence and branching off of existing universes has been proposed a long time ago and there is not a shred of evidence to support it, and it’s not clear that there ever can be any experiment that will be able to verify it.
If and when someone can at least postulate a doable experiment that can validate the multiverse idea, then we can start talking about it as a scientific theory. Until then, it is purely science fiction and fantasy.
Travel backwards in time IS possible, but it requires travel through space at greater than the speed of light (less than the negative speed of light, actually). So I could travel back in time 100 years, but I’d end up 100+ light years away. Nothing that I do there can affect my origin in space until after the time I left. Makes sense right?
The only thing I can’t figure out is what happens if I turn around. :smack:
You can, but it roughly requires a computer made of a white dwarf star, 3 asteroids and a dutch elm in a klemperer rosette…
Well, the way you can get around this is instead of giving every single quark or subquark or whatever we’re on these days its own identity period, you give each particle its own identity for a given period in its time or “origination” this leads to some terminology issues here but bear with me.
Let’s say the number of particles in the universe now is ϡ (lower case sampi/disigma, because obselete letters are cool). Now given various fundamental laws I’m not… ahem… quite qualified to dispute, this has to remain constant. This is the current understanding at least, using a model where time travel is possible you can postulate that
Ϡ(upper case sampi) = ϡt = constant
ratjer tjam
ϡ = constant
This simply alters it so that the number of particles (and whatever else) for all time together is equivilent rather than needing to have every particle in one time constant. That’s one of the easier things to get around really.
Anyway when we get into Time Travel models and such I always have to bring up this handy list of several models:
Yeah, it says in fiction but we’ve really been in a discussion about what-if scenarios all this time so…
I personally like the “the future is preserved via sheer dumb luck” philosophy myself, but if it happens every time it’s not dumb luck/
I also enjoy one of the other single models:
I’ve never read this book, but the gist I get from wikipedia is the end of the universe occurs, and information/plot events are relayed back and forth via various mediums until the universe reaches a different, more favourable, and now static state (though it could theoretically be changed again I guess).
Also, wasn’t there an article on the Large Hadron Collider possibly screwing with time (locally where the collision happened) a bit or something like that? I seem to recall it being posted once upon a time a few weeks ago.
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’.)