Is time travel possible theoretically ?

I would like to refer to two different links in regard to my previous statements about wormholes and their use as possible time machines : http://www.dd.chalmers.se/~f93jojo/sidan2.htm
gives an argument pro, and claims that possible paradoxes do not arise because as the past, the future is fixed also ! It eliminates all free will and makes the universe a very dull place indeed (for me any way) http://www.aleph.se/Trans/Tech/Space-Time/wormholes.html#4
however holds up a different view as stated by Matt Visser that as wormholes with different propertimes get closer, a stream of virtual particles destroys the two mouths. I haven't found anything that supports my previous explanation but I really don't mind that much because I actually dispise the notion of parallel Plato's mailing to the exosci website. It raises a whole bunch of existential problems and makes more problems then it solves...

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"If I have been able to see further, it was only because I stood on the shoulders of giants."
Isaac Newton

 

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Plato,

Don't take this as if I was denying outcomes of GR; rather, I'm trying to understand exactly what's going on with this "time machine". If you really do understand the derivation, then perhaps you could explain it to me -- because I'm seeing a slew of incongruities here.

First, let's look at what happens in the classical twin paradox. You start out with two twins; one stays on Earth, and another zooms at a relativistic speed to some distant star and back. When the twins meet again, they discover that the one who stayed behind has lived through more years of time than the one that travelled. This is perfectly understandable, and I have no problem with it.

Now, let's look at what happens when the two "twins" are the mouths of a wormhole. The mouth that moves now both experiences time dilation and doesn't (at least as I understand it) -- which is a contradiction! If you merely observe the moving mouth from the reference frame of the stationary mouth, then it is time-dilated. However, if you observe the moving mouth through the stationary mouth, its time flow is exactly the same as in the stationary frame (since the "distance" through the wormhole between the mouths doesn't change.) But only one of the above can be right!! So what the heck is going on here?

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Next, using your own terminology, suppose that at the start of the experiment the time at both D and S is synchronized. Then we move D at relativistic speed for a while, so that in the end the time at S is T, and the time at D is T-deltaT (where deltaT is a positive large number, not an infinitesimal amount). Now, an object from D goes through the wormhole and emerges at S. The question is: why should it emerge at S at time T-dT??? In my view, it should emerge at T -- that is, in S's "present". Similarly, an object entering at S will emerge at D in D's time T-dT; suppose the object then spends some time T' at D, and returns to S. Then the object should emerge at S at time T+T' -- shouldn't it??? So where's time travel here? Sure, if an object originally from S emerges at D, it's own clock will be ahead of D's clock, and if an object originally from D emerges at S, its clock will be behind S's clock. However, just because the clock of the object is different from the clock of the reference frame into which it emerges, that doesn't mean that the object has travelled into <u>its own</u> past or future; all it means is that the object either experienced time dilation and finds itself in a frame that didn't, or the object didn't experience time dilation and the destination frame did. There's no "time travel" here -- or am I missing something?

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I am; therefore I think.

 

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Hi Guys,

Boris the last post from me: I meant to address it to Plato, sorry about the confusion.

Wormholes,
There is a fellow (I have all these links and names somewhere, but I'm doing this from my office at work and don't have any of this stuff here), anyway the paper I read by him (sometime ago now) suggests that you don't need relativistic speeds to achieve time travel through a wormhole. Basically what he said was that all you need is to have one mouth move. Further it would be impossible to hold one end perfectly still and therefore traveling through the wormhole would always result in time travel (always to the past). The reason why time travel would always go backwards is because relative to the traveler only the exit would move no matter which mouth you chose to enter......If I have time I'm gonna dig this stuff up and post some links. I have also very recenlty read something about a successfull quantum scale teleportation. It was a vague article but I believe someone has successfully achieved it. The next step is to move on to atoms rather then quarks, have you guys heard about this. I wonder if its a spin off from wormhole theory.


Beam me up Scotty

 

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I found something on my work PC. I must have saved this text a while back I only just read it, here's a little bit of it.
(I AM NOT THE AUTHOR OF THE FOLLOWING TEXT)

"In his memoirs, Einstein wrote that he was disturbed that his equations contained solutions that allowed for time travel. But he finally concluded: the universe does not rotate, it expands (i.e., as in the Big Bang theory) and hence Goedel's solution could be thrown out for "physical reasons." (Apparently, if the Big bang was rotating, then time travel would be possible throughout the universe!)

Then in 1963, Roy Kerr, a New Zealand mathematician, found a solution of Einstein's equations for a rotating black hole, which had bizarre properties. The black hole would not collapse to a point (as previously thought) but into a spinning ring (of neutrons.) The ring would be circulating so rapidly that centrifugal force would keep the ring from collapsing under gravity. The ring, in turn, would act like the Looking Glass of Alice. Anyone walking through the ring would not die, but could pass through the ring into an alternate universe.

Since then, hundreds of other "wormhole" solutions have been found to Einstein's equations. These wormholes connect not only two regions of space (hence the name) but also two regions of time as well. In principle, they can be used as time machines.

Recently, attempts to add the quantum theory to gravity (and hence create a "theory of everything") have given us some insight into the paradox problem. In the quantum theory, we can have multiple states of any object. For example, an electron can exist simultaneously in different orbits (a fact which is responsible for giving us the laws of chemistry.) Similarly, Schrodinger's famous cat can exist simultaneously in two possible states: dead and alive. So by going back in time and altering the past, we merely create a parallel universe. We are changing someone ELSE's past by saving, say, Abraham Lincoln from being assassinated at the Ford Theater, but our Lincoln is still dead. But does this mean that we are able to jump into H.G. Wells' machine, spin the dial, and soar several hundred thousand years into England's future?

No. There are a number of difficult hurdles to overcome. First, the main problem is one of energy. In the same way that a car needs gasoline, a time machine needs to have fabulous amounts of energy. One either has to harness the power of a star, or to find something called "exotic" matter (which falls up, rather than down) or find a source of negative energy. (Physicists once thought that negative energy was impossible. But tiny amounts of negative energy have been experimentally verified for something called the Casimir effect, i.e., the energy created by two parallel plates.) All of these are exceedingly difficult to obtain in large quantities, at least for several more centuries!

Then there is the problem of stability. The Kerr black hole, for example, may be unstable if one falls through it. Similarly, quantum effects may build up and destroy the wormhole before you enter it. Unfortunately, our mathematics is not powerful enough to answer the question of stability because you need a "theory of everything" which combines both quantum forces and gravity. At present, superstring theory is the leading candidate for such a theory (in fact, it is the ONLY candidate; it really has no rivals at all.) But superstring theory, which happens to be my specialty, is still too difficult to solve completely. The theory is well-defined, but no one on earth is smart enough to solve it.

Interestingly enough, Stephen Hawking once opposed the idea of time travel. He even claimed he had "empirical" evidence against it. If time travel existed, he said, then we would have been visited by tourists from the future, ergo: time travel is not possible. Because of the enormous amount of work done by theoretical physicists within the last 5 years or so, Hawking has since changed his mind, and now believes that time travel is possible (although not necessarily practical.) Furthermore, perhaps, we are simply not very interesting to these tourists from the future. Anyone who can harness the power of a star would consider us to be very primitive. Imagine your friends coming across an ant hill. Would they bend down to the ants and give them trinkets, books, medicine, and power? Or would some of your friends have the strange urge to step on a few of them?

In conclusion, don't turn someone away who knocks at your door one day and claims to be your future great-great-great-grandchild. They may be right."




[This message has been edited by Rambler (edited April 18, 2000).]

 

Boris,
If Hawkin can change his mind, maybe you will too.

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Boris,

I will try and explain but I'm afraid much of your misunderstanding finds it root in the blunt denial of time as an existing dimension.

Let's take the two twins that you understand and place each twin next to a mouth. Suppose one of the twins takes a spaceship and drags a mouth with it. The spaceship flies at relativistic speeds and after 1 subjective year it arrives at Proxima Centauri. This place is 4 lightyears away thus the time passed in the stationary frame is 5 years (4 years plus 1 subjective year). However as you say through the wormhole there has been no timedelation so if the twin at Proxima Centauri goes through the wormhole, he sees his brother again and they are still the same age. This means he has gone back four years in the past, this is the four years it normally takes light to travel from alfa centary to here !
His brother will be very surprised to see him because they can still see his spaceship through their telescope, and it hasn't even crossed a fifth of the distance to alfa centauri...
However there is no real time travel here because both ends of the wormhole are separated by a to large gap to have any danger of the usual paradoxes. The problem begins if (after a consideral amount of refuelling

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) the twin at alfa centauri decides to turn his ship around and head back to earth. He does this again at the same speed and in an other subjective year he is home again ! Upon arrival he finds his brother again, now ten years older (as the normal twin paradox) while he is only two years older. When he enters his mouth (D), for the same reason as the first time he will again emerge from S and find his brother to be the same age as him. He now invites his brother to come with him trough the wormhole and go eight years ahead in the future. They emerge through D and find the future counterpart of the brother... They have gone through a timemachine and here come the paradoxes !

Rambler,

Could you please explain how the Casimir effect (which showed the existence of a zero-point energy as far as I knew) shows that negative energy or mass exists ? Could you perhaps give me a link to some kind of paper who explains it ?
By the way are you citing someone when you say you are an expert in stringtheorie or are you really an expert ? If you are, I love to have a discussion about it...

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"If I have been able to see further, it was only because I stood on the shoulders of giants."
Isaac Newton

[This message has been edited by Plato (edited April 18, 2000).]

 

Plato,

Bear with me...

But the twin doesn't have to go through the wormhole for them to see each other. The stationary twin S can simultaneously observe D through normal space with one eye, and through the wormhole with another eye. And now the question becomes, which one of the two simultaneous and yet contradictory measurements is correct, and in fact is either of them correct? (neither of them is any more "special" than the other -- at least as far as GR is concerned.) This goes to the very core of relativity, which is based on measurement as a means of constructing reality -- here, we have two simultaneous and yet contradictory measurements; twin D simultaneously does and does not undergo time dilation. I mean, if this is not a mathematical contradiction, then I don't know what is! I can't understand why the contradiction is deemed acceptable; in fact, if I were the one trying to formulate GR and came up with this solution in the course of my work, I would probably go back to the drawing board because such a contradiction is a surefire indication that the theory is inconsistent and incorrect!

That's not correct. Even if D travels at 1.0c, by the time it gets to Vega, from Earth we shall observe it to be half-way there. If D travels slower than 1.0c, then from Earth it will appear to be even closer to Vega at the time it actually finishes the trip (e.g. if D travels at 0.33c, by the time it gets to Vega, we will on Earth receive the light it emitted when it was 1- 0.33/(1+0.33) = 0.75 percent of the way there.)

Ah, but therein lies the rub. Why should this particular phenomenon occur here? What prevents twin D from going through the wormhole, and finding twin S to still be 8 years older? In other words, why does the observation through the wormhole suddenly take precedence over observation through normal space, whereas they are supposed to be equipotent? Is the observation through the wormhole only an illusion, and the observation through normal space the true representation of time flow at D? Or, conversely, what if the movement of space (which is essentially what happens when you drag a wormhole mouth around) carries D with it in a way akin to a warp bubble, and the "dilation" observed through normal space is a mirage? As far as I can see, only one of the two can be true at a time; both cannot be correct, or else we have a contradiction!

As for exotic matter and construction of wormholes, I believe I already provided the reference to the article that Rambler seemed to had referred to. Here it is again, in case you missed it: http://www.newscientist.com/news/news.jsp?id=ns223420 It concerns some work done by a Russian theorist that shows existence of traversable wormholes that automatically create their own exotic matter due to the way they are constructed.

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I am; therefore I think.

[This message has been edited by Boris (edited April 18, 2000).]

 

Boris,

I see your problem, I really do, but again I tell you it arises because you don't want to see time as truly existing.

They only seem contradictory while in fact looking through the wormhole is looking through an other kind of space then looking through normal space. In relativity we have to talk about the Worldlines of objects, what the wormhole does is make a shortcut between the two worldlines of both mouths. No matter what happens in normal space with the mouths, they are always linked through wormhole space. No contradiction only two different spacetime contiua...

That is very probable but I was using alfa proxima as my example which is a bit more then 4 lightyears away from us (I thought). I didn't really check my math as I should

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but was using crude approximations, thank you for the correction however.

No rub, see my previous answer. If this is possible to bring two mouths together who are timeshifted relative to each other, then they would still shortcut the two worldlines of the mouths, this shortcut would be more in time in then in space in this particular case. Thus making time a genuin dimension you can travel in OR would consist in the connection of two parallel worlds. Take your pick...

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"If I have been able to see further, it was only because I stood on the shoulders of giants."
Isaac Newton

 

Plato (VERY IMPORTANT),

OOOOOOPS, sorry I wrote that I had this text saved at work. I got it off the net and I'M NOT the author, so not claiming to be an expert. I surfed around and started to read ran out of time and saved the text. I only have a very basic understanding of these concepts. The text i have saved doesn't have the author's name otherwise I would have attached it. Again sorry. I just posted this stuff to show Boris that even Steven Hawkins changed his mind about time travel.

Boris,

you said:
"The stationary twin S can simultaneously observe D through normal space with one eye, and through the wormhole with another eye"

How can the twin view this simultaneously?, the image in normal space would take 4 years to reach him, so the normal space image would NOT have the other twin in it for another 4 years. Looking through the worm hole would then in affect be seing 4 years into the future would it not (if we assume the normal space image is the present rather then 4 year old light, but the former point is the one I'm trying to make this is just a side note).

[This message has been edited by Rambler (edited April 18, 2000).]

 

I have found a website with the correct formulas for a relativistic rocket that is under constant acceleration : http://phyhp.phy.ncku.edu.tw/mirrors/physicsfaq/rocket.html

So my previous problem, assuming there is 4 lightyears difference between Sol and Alfa Centauri and I have a constant acceleration of 1 g and half way I begin braking. It would take 3.56 years shiptime to get to full stop at Alfa Centauri, coming back to earth is again the same amount of years so actually the twins would be almost a year apart now and the wormhole would provide a means to a year in the future or past, depending what mouth you do in.
If I would stick to my previous assumption to brigde the distance of 4 lightyears in 1 year ship time, it would take a bit more then 5 g's. This is a bit to much for the human constitution to undergo for two consecutive years I'm afraid...

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However if we would go much further, we could still do this in one lifetime. Suppose we would go with one g acceleration to the Andromeda Galaxy, which is 2 million lightyears away. Assuming the same procedure with breaking halfway it would only take us a bit more then 28 years ! If you go back then you would have some timemachine taking you 4 million years into the future !

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"If I have been able to see further, it was only because I stood on the shoulders of giants."
Isaac Newton

 

Because everything is made up of straight lines and curves, time travelling is impossible. The physical representaion of time i.e. watches are made up of atoms, protons, neutrons (metals/or whatever). This shows that the fastest anything known can travel is the speed of light. To think differently about how machines are made is the answer to this problem. Think caveman and wheel, egyptians and pyramids.

 

Epitectus,

Ha?

 

Rambler, Plato,

The point is not in the fact that the states represented by photons arriving through the wormhole and photons traversing normal space are not synchronized. The contradiction comes from the fact that judging from photons that come through the wormhole, the moving mouth experiences no time dilation, while the photons arriving through normal space indicate that the moving mouth is time-dilated. Thus, simultaneous observations indicate that the moving mouth is time-dilated and not time-dilated at the same time. (Btw, since the moving mouth starts moving from a vicinity of the stationary mouth, it will be visible during its entire journey, not 4 years later.)

And it's not two distinct spacetime continua; it's one single continuum with a topological twist in it. The contradiction is still there, and it is not at all clear what is really happening with the event rate at the moving mouth.

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I am; therefore I think.

[This message has been edited by Boris (edited April 20, 2000).]

 

Boris,

I think you got the problem of wormholes on the spot, the only way out of it is by saying that or wormholes simply don't exist and won't ever exist or that wormholes connect different universes...
From the moment the wormhole exist, the two mouths we see are not connected at all but each lead to a different universe so actually when you 'make' a wormhole you are making two of them. This last explanation is very awkward I know and I don't like it at all, but to tell you the truth I don't know enough about the details of wormholes to give a sensible answer...

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However I see a small loophole, Since the photons going through the wormhole are with you much faster then the ones going through normal space, we are actually not talking about simultaneously created photons any more. So the image you have through the wormhole will always be younger then the one you have through normal space. This might be a reason why there is no real paradox. Maybe if you stretch the concept of 'simultaneity' enough there will be no such thing as a paradox...

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"If I have been able to see further, it was only because I stood on the shoulders of giants."
Isaac Newton

 

Plato,

If a wormhole links two distinct universes, then it's not truly a wormhole. Real wormholes are just supposed to be topological deformations of one and the same spacetime. And it's hard to say that wormholes don't exist since they arise as solutions to a variety of different scenarios under GR. There has been a time when people couldn't come to grips with neutron stars and black holes, and even Einstein spent a significant portion of his career trying to show why black holes can't exist ("abominations" he called them.) By analogy, a purported inexistence of wormholes would be resting on rather shaky ground.

Finally, the differential reception time scenario you describe doesn't solve the paradox. Imagine a setup where the moving mouth of the wormhole makes a full circle and zooms past the stationary mouth. Then there will be two configurations where the distance photons travel from the moving mouth through the wormhole to the stationary mouth, and from the moving mouth to the stationary mouth through normal space, is the same (i.e. photons emitted simultaneously at the transmitter located at the moving mouth, will arrive simultaneously at the receiver located at the stationary mouth.) So you see, there's no simultaneity trick here. We are concerned with photons emitted in a single reference frame, so we can indeed be sure that within that reference frame the photons were emitted simultaneously, and represented its instantaneous motion. So, the problem still remains: according to the observer at the stationary mouth, the moving mouth simultaneously is and is not time-dilated, which is a logical contradiction. I've searched and thought about this, and I still can't find a way out...other than to say that the "time" in GR (or SR for that matter) is an incorrect construct, and should rather be thought of as rate...and somehow, somewhere, an absolute reference frame must creep in. (did I hear a "DOHHH!"?

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)

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I am; therefore I think.

 

Boris,
I still don't see the paradox. I'm nowhere near Plato's or your level of understanding of GR so bear with me.

Could you eplain to me again (dumb it down as much as you can stomach) how you come to the conclusion that an image on one side of the wormhole would create a paradox to an observer on the otherside. Could you perhaps illustrate your above example with arbitary dimensions like say 100 meter long throught (inside wormhole) and .25 l/year normal space....or whatever you need to explain what make the paradox a little clearer. Also if you have the resources could you post some equations that deal with the dilation issues (Plato if you have them please post, as I have said before I'm at work and don't have the means).

 

Rambler,

First of all, you would be surprised if you would know what I don't know about general relativity. The things I do know are what I remember from my courses in university and the (popularised) articles I read about it. I never really studied it in dept...
Anyway I think you will find http://phyhp.phy.ncku.edu.tw/mirrors/physicsfaq/relativity.html very interesting indeed. It has a whole bunch of formulas and also explanations of weird relativistic effects.

Boris,
what can I say ? I'm as much at a loss as you are. The only thing I can say that to arrive at the paradox that you talk about assumes already a whole bunch of thing of which we don't have any data about !
To begin with is ther such a thing is negative mass ? I agree that wormhole are an essential part of GR but normal wormholes only exist at the quantumscales, we need negative mass to blow them up to our macro world. Then is it possible that timeshifted mouths can come close enough together to make an experiment that you are talking about ? One thing is for sure GR as we know it is certainly not a complete theory, String theory is in the making and I actually have my doubts if that will be the 'ultimate theory' that they want us to believe.
We don't have a wormhole so we can't test it and for me experiment stays the ultimate way to make sure we aren't bullshitting ourselves (pardon the expression) and making up stories about timetravel and wormholes.

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"If I have been able to see further, it was only because I stood on the shoulders of giants."
Isaac Newton

[This message has been edited by Plato (edited April 28, 2000).]

 

Rambler,

The paradox arises because of the way relativity treats reality. In relativity, you cannot assume something exists in some state in any way, unless you receive light (or some kind of signal bearing information) from whatever it is you are interested in describing. Then you could use the signal you received to describe the object it came from (and therefore the state of the object.)

Relativity uses light as a measuring stick both to measure distance and time (since lightspeed is constant and absolute). Because of that, it is fairly easy (well, at least in absense of gravitational mass, meaning a flat spacetime) to derive formulas that show time slowing down in a fast-moving object, as determined by a stationary external observer based on the light emitted by the moving object. This is what we call time dilation.

The paradox arises because, while sitting at the stationary mouth of the wormhole, we observe photons of light simultaneously emitted from something located at the moving mouth. Some of the photons go through the wormhole to reach us, while others traverse regular space. If we take a snapshot of this situation when the moving mouth of the wormhole is just as far away from the stationary mouth along normal space, as it is through the wormhole, we have photons simultaneously emitted from the moving mouth at that moment, traveling through both normal space and through the wormhole, and arriving at the stationary mouth simultaneously. With respect to the stationary mouth, the distance to the moving mouth <u>through the wormhole</u> does not change, while the distance to the moving mouth through regular space is changing since the moving mouth is indeed moving. Now, if the moving mouth is zooming at a relativistic speed, then as observed by the stationary mouth through normal space via photons received from the moving mouth, it is measurably time-dilated (meaning that its time rate has slowed down relative to that of the stationary moutn.) However, judging from photons received through the wormhole, the "moving" mouth is actually standing still, and is not time-dilated at all.

The task of the observer at the stationary mouth is to determine just what is happening with time at the moving mouth. And the point is that if this observer used just the photons that arrived through normal space, he/she would conclude that time at the moving mouth has slowed down. However, if the observer used just the photons that arrived through the wormhole, he/she would determine that time at the moving mouth is synchronized to his/her own time. These are two mutually contradictory conclusions, and yet according to relativity they must both be simultaneously true. So there is something very fishy going on here, and we do indeed have a paradox.

Now, it seems the "solution" to the paradox is to assert that due to the motion of the "moving" mouth, the wormhole establishes a time gradient across itself, so that even though the moving mouth is really time-dilated (as observed through "normal" spacetime), the signals it sends are being squeezed closer together in time as they pass through the wormhole, with the end result being that they appear not at all time-dilated at the stationary mouth (in essense, they travel into the future). What's particularly bizarre about this, is that the space inside the wormhole remains undisturbed through all of this "motion", so it's unclear where the time gradient comes from, as far as that region of spacetime is concerned. And in general, it's not clear why the spacetime inside the wormhole should be any less or more "privileged" than the space outside, in terms of induced time gradients. For example, imagine enlarging the wormhole until its internal volume is larger than "the rest" of the universe -- now what is the "inside" vs. the "outside"?

And at any rate, since I refuse to consider time a dimension, I tend to think that there is something fundamentally wrong with this entire construction...

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I am; therefore I think.

 

Boris,

Thanks for the excellent explanation, hope it wasn't too painfull going into so much detail

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OK,
There is a stationary mouth and a moving mouth. The observer in (or on the edge) of the staionary mouth recieves a photon from the passing exit (through normal space) and concludes that time dilation has indeed occured. However you also say:

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"What's particularly bizarre about this, is that the space inside the wormhole remains undisturbed through all of this "motion", so it's unclear where the time gradient comes from, as far as that region of spacetime is concerned"

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Therefore the observer still sees the exit move at relativistic speed wheather the photon comes through normal space or through the wormhole. Both would appear dilated. If indeed the space inside the hole is the same as that outside and distances are the same. Therefore still no paradox (maybe????, I realise this is too simple to solve the dilema but I thought I'd post it anway)

Also,
The event you describe has one moment where the geometry is such that the photon travels an equal distance. I'm not going to attempt to comprehend the dynamics involved in a system which is being observed with relativitic speeds AND topological twists

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but would I be right in assuming the paradox would only exist for the one moment where the path through the hole or normal space is equidistant. The reason I ask is because for that one moment we can assume the same reference frame wheather looking through the wormhole or through normal space?????????. However I would think that when the distance are no longer the same we would need a seperate reference frame and assume two seperate sytems of events.

On a side note one wormhole solution I have read about (in fact the first I time I had ever heard of them) suggested that if the EXIT is movig relative to the entrance (and this would always occur) then the solution (I suspect over large distance in normal space) as I understood it stated a photon (or whatever) would exit the wormhole in the past. i.e you would always go back in time. I wish I took more notice of the math it would probably come in handy here...



[This message has been edited by Rambler (edited April 29, 2000).]

 

okay, folks, i don't know who all took the time to read that article, but it doesn't say that they observed a wormhole, just that they "mathematically proved" that one could exist. it goes on to say not that it proves exotic matter exists, but that it assumes and requires its existence as a pretense. you can prove virtually anything through high-level math, and you can look in the religious forum under "theomatics" for an entertaining example of how something can be "100% proven" by math.

time travel becomes a possibility once you begin describing time as another physical dimension. although we do currently describe time as another dimension, problems occur when we begin to apply characteristics of our own three physical dimensions. imagine a two dimensional being in his two dimensions, "traveling through" time as a third dimension. you could say that for him, time travel would be possible if he were to bend some of his space three dimensionally back to another one of his two dimensional planes of existence in the past. unfortunately, this requires that we look at time as simply a series of still frames, causing all kinds of problems. furthermore, this requires that his third dimension of time act exactly as the other two, when we have every indication that it acts very differently. the issue is far more complicated than that, but we are bound by the limitations of our universe. we would have nothing to allow us to break those boundries, just as the two dimensional being would have no way of curving his universe in the third dimension as he could apply no force in that direction. no, i do not believe that time travel is possible, and we don't even have any solid theories on how this might be accomplished. however, as an open-minded individual i have to concied that our current understanding of the universe is far from adequate, so i cannot eliminate the possibility.

we have to think of time travel in one of two ways, and the "paradoxes" which are outlined here are only caused when you mix the two. the first way is that you look at it as one continuous timeline, and that anything you do while traveling back in time is included in reaching the time machine and sending yourself back. at this point, everything you do has already happened as determined history, i.e. you already didn't kill yourself when you travel back because you aren't dead now. the second way is to describe it as diverging timelines. at the exact point you travel back to in time, you begin to create a new timeline with potentially different results. at this point, you would completely dissapear from you original timeline never to be heard from again. you could only return to the alternate timeline because your "time-traveled" existence returning to the future requires your "time-traveling" existence in the past; you can't return with a bunch of memories without those memories having happened. in the original timeline, of course, none of those memories happened because you had not yet traveled back in time. this would explain why we have never been visited by time travelers, because we would first have to follow the path leading to that time traveling. however, this also allows you to now go back and kill your parents. you would simply return to a future with no record of your existence.

as for the wormhole discussion, i think this is a case of where we need to differentiate between reality and percieved reality. light does not dictate reality, and should not be treated as any more important than any other object traveling through the wormhole. when i look at a picture of a mountain on my computer, it isn't because i create a small mountain inside my monitor. it is because my video card knows how to create the correct pattern of light to fool my eyes. yes, you could stare through a wormhole and normal space and see two totally different images of the same object. so?

samus