Is Time Travel Possible?

[Sophid]

Whatcha all think?

[Petter Sandstad]

Nope, it is impossible. Time is just a quantification of motion. Once a given motion is done, it is. One cannot use one motion (time travel) to errase a historic motion. The only thing one can do is slow down the motion in one area in relation to a different area. i.e. by making the motions in the one area slower or faster, through for instance very high speeds (as in space travel).

[Arakasi Takeda]

Whatcha all think?

Do you have a poll selection for "I don't know?"

There are a number of intriguing possibilities for causal violations arising in both String Theory and Quantum Mechanics, but neither of those theories are 'complete' within the realms of the phenonenom they describe. As such, conditions under which causual violations or closed space-like loops occur cannot be judged without further research.

Nope, it is impossible. Time is just a quantification of motion. Once a given motion is done, it is. One cannot use one motion (time travel) to errase a historic motion. The only thing one can do is slow down the motion in one area in relation to a different area. i.e. by making the motions in the one area slower or faster, through for instance very high speeds (as in space travel).

If time is just a 'quantification' of motion, do you ascribe to an idea that observable effects such as twin paradox or the tilt of the light cone on the edge of supermassively curved space is just some kind of illusion? Do you feel the measurement of time is absolute, or fluid? If it is an absolute measurement, how can it change, as it observably does in Relativistic experiments? If it is fluid, how can one logically rule out a case where the measurement changes sign or becomes imaginary (as in imaginary numbers, as is sometimes the case in descriptions of certain quantum effects)? How do you explain quantum entanglement effects, if time is 'just a measurement'?

[And no, I can't answer these myself, because I don't know that the science is settled on any of them. You seem to be much more certain in your statement though, so I'm curious of your insights]

AT

[blunereid]

I agree with Petter's statement. This is what current proven science shows. There is no evidence that there is any way for you to go backwards in time. Anyone touting that time travel is possible needs to prove it before they can claim it is possible. The burden of proof is on them to prove it.

A moment is over once it has happened and you can never get back to that moment. Time is linear, like said above in the poll. It goes like this, moment, moment, moment, moment, moment..... you get my point. How can you go back to a moment that has already passed? If so, it would bring about a paradox (a contradiction). And since contradictions cannot exist....

I am not a scientist, so I dont know what any of those things that you mentioned above are, let alone the cause of them. I doubt it leads to time travel. More than likely it is just that we dont currently know the cause of these phenomenons.

[musashi]

I voted “last Tuesday” – but I didn’t time travel last Tuesday. I do believe technology could one day make time travel a possibility. I think that the technology is a long way off right now. Actually the theoretical physicist and mathematicians are making break throughs regarding time with membrane theory (an extension of string theory) .

Do you feel the measurement of time is absolute, or fluid? If it is an absolute measurement, how can it change, as it observably does in Relativistic experiments?

Einstein’s theory of special relativity claims that absolute measurement would only be possible in systems where motion is uniform. If the system begins to move at different rates or in different directions measurements become relative to the frame of reference.

I believe that space time is curved by a magnetic field. If that field can be strong enough to bend space time back on itself, then why wouldn’t time travel be possible? Of course there would be a few simple challenges like pin pointing exact space and time coordinates – seems like an almost infinite number of permutations there. And then the system would have to compensate for an almost infinite number of parallel universes – we do want to reach our specific timeline. From the outside time travel may seem impossible. I’m not so sure.

Time travel is a part of the futurist novel I am currently writing, so I've had a head-start thinking about this question.

[Arakasi Takeda]

agree with Petter's statement. This is what current proven science shows. There is no evidence that there is any way for you to go backwards in time. Anyone touting that time travel is possible needs to prove it before they can claim it is possible. The burden of proof is on them to prove it.

A moment is over once it has happened and you can never get back to that moment. Time is linear, like said above in the poll. It goes like this, moment, moment, moment, moment, moment..... you get my point. How can you go back to a moment that has already passed? If so, it would bring about a paradox (a contradiction). And since contradictions cannot exist....

I am not a scientist, so I dont know what any of those things that you mentioned above are, let alone the cause of them. I doubt it leads to time travel. More than likely it is just that we dont currently know the cause of these phenomenons.

I certainly agree that everything I mentioned is _highly theoretical_; none of it is a proven scientific fact. Various phenomenon are predicted in general relativity and quantum mechanics that give the impression that time is NOT just a measurement of moment to moment, as you described, but is, in some way, a physical quantity.

I'm sure many of you have heard of time as the 'fourth' dimension, or, perhaps you've heard the term space-time; we tend to think of 'space' as existent in three dimensions, like Cartesian coordinates. Relativity includes motion in a fourth dimension whose properties we would call time. When describing events taking place in relativistic space-time, they use diagrams called light cones to represent a transition through the three dimensions of space -and_ the temporal dimension (past/future). It's called the 'Light cone' because the geometric space is bounded by a measurement of the fastest speed any 'obect' or 'event' could propogate through the universe - the speed of light.

Every in event taking place within the light cone is transitioning at a speed less than light. These events are called 'time-like', because they occur in a fashion we would see perceive as traveling forward in time - one event causes another causes another, etc. - the line of cause and effect is bounded within the light cone.

Any event which took place faster than the speed of light would exists outside the cone. Such events are called 'space-like' and would appear to exist 'outside of time'. The complex mathematics dealing with the events outside this boundary can be modeled by computer, and appear like an object traveling forward or backward in time, outside our normal understanding of causation.

This is the genesis of the phrase, traveling faster than the speed of light is 'traveling through time', which you might have heard in common science ficton settings.

The question is, can anything actually travel faster than light (i.e. exist outside the light cone). Physicists, in studying quantum mechanics, have theorized the existence of at least one type of particle, called the tachyon, whose quantum properties seem to suggest that it travels as speeds faster than light. We have not, however, ever detected a tachyon in experiments meant to search for exotic cosmic particles. If one were detected, it would challenge the idea that time travel is impossible.

Things get even messier when you start including General Relativity into the light cone diagrams. Regions of extreme gravitation 'warp' space-time - for instance, in a region of infinite density, like a black hole. Warped spacetime does bizarre things to the geometry of light cones, resulting in a phenomenon known as 'tiping'. Tiping the light cone has the effect of distorting the boundary between time-like and space-like events. On the edge of a black hole, space can become so distorted that space-like events and time-like events become the same, and then swap each other. The result is the well documented prediction that, as one approaches the event horizon of a black hole, time seems to slow down and then stop all together. Time becomes meaningless - causality breaks down at the edge of a black hole (just like all other physical laws).


I know that what I wrote above probably doesn't make much sense to the non-scientist. It is a highly theoretical subject, and really needs a deep grounding in General Relativity and differential calculus to give an accurate and precise discussion of. But the fact remains that General Relativity, a theory with strong evidentiary support, does predict that regions of space exist where time stops and even reverses (they just all happen to be spaces of infinite or _near infinite_ space-time curvature, such as black holes).

And as weird as General Relativity seems, Quantum mechanics makes it even worse. If you really want to see something that will make you question your understanding of Causality as a 'real' phenomenon, you should google the words 'quantum entanglement'. Scientists have begun to actually do experiments with quantum entaglement which seem to turn causality on its head - effects happening 'before' their cause.

I'm attaching a URL for an 'introductory paper' on quantum entanglement. It is not a simple read. It demonstrates a little of the basic issues around the phenomenon, but quickly jumps into the actual mathematical derivations of the idea from Relativity and Quantum Mechanics. If you can get over some of the math, it might explain some of what I'm getting at in stating there really are instances where well examined, well evidenced theories (like Realtivity and Quantum Mechanics) that make particular predictions 'at their fringes' which suggest time travel _might_ be possible.

http://fergusmurray.members.beeb.net/Causality.html


AT