Can Exceeding the Speed of Light Really Mean Time Travel?

[Austin0]

Hi Austin0.

I don't think I understand the question. Since you mentioned absolute simultaneity, you seem to be asking about instantaneous messages in Galilean spacetime. If there's absolute simultaneity, the question of "simultaneous in what coordinate system?" doesn't even arise. So if t=0 at the departure, then isn't t=0 at the arival too, by definition of "instantaneous".

"Proper time" is a property of a curve in Minkowski spacetime, not a point. The concept of proper time isn't needed in Galilean spacetime. (We would have to define it as the coordinate time difference between the endpoints).

The post I linked to in #6 deals with instantaneous messages in Minkowski spacetime.

Hi The question is purely in the context of SR It seems to me that the term proper time is frequently used to mean the observed reading on the local clock and not necessarily an interval. If this is technically incorrect then it's commonly incorrect and I will curb the habit.

So the absolutely instantaneous definition is applied to the phenomenon of teleportation.

So are you saying here that in a SR context the arrival time would be t=0 ??

Thanks

 

[Nysgjerrig]

Is there anyone who have looked into this mysterious particle called bosson singlet? According to some scientist it should be possible to use those particles as tool to send message back in time with LHC (CERN). I find that interessting in terms of particles that can exceeding the speed of ligth or at least find "a loop hole" so it outmatch the speed of ligth.

 

[Fredrik]

Hi The question is purely in the context of SR It seems to me that the term proper time is frequently used to mean the observed reading on the local clock and not necessarily an interval. If this is technically incorrect then it's commonly incorrect and I will curb the habit.

So the absolutely instantaneous definition is applied to the phenomenon of teleportation.

So are you saying here that in a SR context the arrival time would be t=0 ??

Thanks

Many people define proper time as what a clock measures. I don't like that actually. I prefer to define the term only as referring to a mathematical property of the curve that represents the motion of the clock. The statement that clocks display proper time is then a correspondence rule, i.e. an assumption that tells us how to interpret a piece of mathematics as predictions about results of experiments.

I still don't quite understand your teleportation question. If you are talking about messages that are instantaneous in the coordinate system in which the emitter is stationary, then this is covered by the post I linked to in #6.

 

[GeorgeDishman]

So the absolutely instantaneous definition is applied to the phenomenon of teleportation.

So are you saying here that in a SR context the arrival time would be t=0 ??

The definition I understand of "teleportation" is moving from one location to another without passing through intervening locations, for example in quantum tunneling.

In SR, there is no such thing as absolute simultaneity so if your form of teleportation existed, SR would not be applicable, you would need to discard SR for some other theory that supported absolute simultaneity.

 

[Austin0]

The definition I understand of "teleportation" is moving from one location to another without passing through intervening locations, for example in quantum tunneling.

In SR, there is no such thing as absolute simultaneity so if your form of teleportation existed, SR would not be applicable, you would need to discard SR for some other theory that supported absolute simultaneity.

Hi Thank you .I am in complete agreement. That is exatly the point.
I have the same understanding of what is meant by teleportation. I also don't consider it a very plausible possible reality but in an imaginary thought experiment it can be well defined so the same conditions pertain as if it was a reality. Which, as you say would mean that SR was not applicable.
That to simply assign the time according to coordinate simultaneity, isotropically to its arrival anywhere within a frame, is to implement an implicit assumption of absolute synchronization of the clocks in that system. Which we know is not a valid assumption in SR.

Without this initial assumption and the consequent spacetime location of its arrival or hypothetical arrival, in the initial frame, there is no basis whatsoever for any prediction of where or when it might arrive in another frame.
WOuld you agree?

I agree the idea of a universal simultaneity according to Galilean clocks was actually eliminated by SR but the idea of restricted absolute simultaneity as, for exsample EPR , is not mentioned or excluded.
As far as my understanding of the QM concept and the current state of experimentation it appears to be (or at least promise) a means of establishing absolute simultaneity between two locations. I myself, don't see this as a problem or a detraction from SR as the phenomenon doesn't entail motion per se , through spacetime, so is outside the domain of SR or perhaps more correctly would simply be a physical phenomenon within SR but would not necessarily change the structure.
Thanks

 

[harrylin]

[..] As far as my understanding of the QM concept and the current state of experimentation it appears to be (or at least promise) a means of establishing absolute simultaneity between two locations. [..]

That is inexact, and here it is necessary to be exact. From Bell's theorem and the current status of experiments one may infer the existence of an absolute simultaneity, but other explanations have been given. And the main point here: if it would be possible to determine absolute simultaneity, that would break the relativity principle. According to all the currently discussed explanations it will not be possible to determine absolute simultaneity.

 

[GeorgeDishman]

The definition I understand of "teleportation" is moving from one location to another without passing through intervening locations, for example in quantum tunneling.

Hi Thank you .I am in complete agreement. That is exatly the point.
I have the same understanding of what is meant by teleportation. I also don't consider it a very plausible possible reality but in an imaginary thought experiment it can be well defined so the same conditions pertain as if it was a reality.

Let me give a crude sci-fi example of what I mean. Suppose a human could be frozen in liquid helium and later thawed as the cryonics industry is attempting. The frozen person could be dismantled atom by atom here with the relative location of each particle noted. That data could be emailed to Mars and the person reassembled using locally sourced atoms. When thawed, they would have traveled between the planets without passing through the space between them in physical form. That technique could be extended to distant stars if unmanned probes could be sent there to build the receiver. That would essentially provide "teleportation" at the speed of light.

In SR, there is no such thing as absolute simultaneity so if your form of teleportation existed, SR would not be applicable, you would need to discard SR for some other theory that supported absolute simultaneity.

Which, as you say would mean that SR was not applicable.

The assumption of absolute time would mean SR is philosophically wrong (IMHO) though still mathematically valid, the assumption of teleportation does not.

That to simply assign the time according to coordinate simultaneity, isotropically to its arrival anywhere within a frame, is to implement an implicit assumption of absolute synchronization of the clocks in that system. Which we know is not a valid assumption in SR.

Without this initial assumption and the consequent spacetime location of its arrival or hypothetical arrival, in the initial frame, there is no basis whatsoever for any prediction of where or when it might arrive in another frame.
WOuld you agree?

Not quite. The question of "where" is easy, you arrive wherever the receiver is located. If the teleport works at or below the speed of light, normal physics applies. If it is FTL then the actual speed in any frame tells you when and the where/when coordinates can be transformed by Lorentz as usual, you just get an FTL result in all frames, but as has been discussed, you also get the ability to move back to your own past.

I agree the idea of a universal simultaneity according to Galilean clocks was actually eliminated by SR but the idea of restricted absolute simultaneity as, for exsample EPR , is not mentioned or excluded.
As far as my understanding of the QM concept and the current state of experimentation it appears to be (or at least promise) a means of establishing absolute simultaneity between two locations.

From Bell's theorem and the current status of experiments one may infer the existence of an absolute simultaneity, but other explanations have been given.

I don't follow that. For example, you can measure the state of two entangled particles at spacelike separated events and find they are correlated but that doesn't define a surface of simultaneity. You know when you measure a particle but you cannot distinguish between (a) whether you are the first or second to make a measurement and (b) whether the value was determined by your measurement or had already been forced some time earlier. This means that although it appears to imply there is a linkage which is FTL, all FTL values are equally valid, and since no information is passed, SR is not invalidated that way either.

Obviously, an absolute frame is one approach to understanding the behaviour of entangled systems but I don't think it can be "inferred", only postulated.

I myself, don't see this as a problem or a detraction from SR as the phenomenon doesn't entail motion per se , through spacetime, so is outside the domain of SR or perhaps more correctly would simply be a physical phenomenon within SR but would not necessarily change the structure.
Thanks

If an absolute frame defines the rate of physical processes, then SR becomes only an emergent description of something else IMHO, but nothing I've seen so far provides any evidence for that.

Incidentally, this experiment looks as though it could send data into the past (by binary modulation of Victor's decision measured by correlation of Alice and Bob's results) which, combined with the "teleportation" method outlined above would allow us to visit the past any time after the first receiver is built:

http://www.sciencedaily.com/releases/2012/04/120423131902.htm

The preprint is available here:

http://arxiv.org/abs/1203.4834

 

[harrylin]

[about Bell theorem]
I don't follow that. For example, you can measure the state of two entangled particles at spacelike separated events and find they are correlated but that doesn't define a surface of simultaneity. [..] SR is not invalidated [..]

Yes, you elaborated on what I stated in the part that you snipped.

[..] Obviously, an absolute frame is one approach to understanding the behaviour of entangled systems but I don't think it can be "inferred", only postulated.

Such a postulation is not based on nothing. Again: that is one of a few possible explanations that may be inferred (http://dictionary.reference.com/browse/infer?s=t ) from observations; other proposed explanations are conspiracy, non-reality or many worlds. Elaborating would be off-topic both in this forum and in this thread, but see the last part of http://cdsweb.cern.ch/record/142461?ln=en

 

[GeorgeDishman]

Yes, you elaborated on what I stated in the part that you snipped.

Such a postulation is not based on nothing. Again: that is one of a few possible explanations that may be inferred (http://dictionary.reference.com/browse/infer?s=t ) from observations; other proposed explanations are conspiracy, non-reality or many worlds. Elaborating would be off-topic both in this forum and in this thread, but see the last part of http://cdsweb.cern.ch/record/142461?ln=en

OK, I think I was reading too much into your use of "infer", no problem.

 

[Austin0]

[

As far as my understanding of the QM concept and the current state of experimentation it appears to be (or at least promise) a means of establishing absolute simultaneity between two locations.

That is inexact, and here it is necessary to be exact. From Bell's theorem and the current status of experiments one may infer the existence of an absolute simultaneity, but other explanations have been given. And the main point here: if it would be possible to determine absolute simultaneity, that would break the relativity principle. According to all the currently discussed explanations it will not be possible to determine absolute simultaneity.

Certainly I have drawn no conclusions. And the current state of the technology and implementation don't seem to allow for any determination as they all seem to be essentially fuzzy, timewise. Not discrete events but statistical aggregates of events over some interval.
But it is early days and based on the concept it still appears to hold the possibility of eventual definite determination. As for that occurence breaking the relativity principle I am not sure how to interpret your point:

It is safe to assume it won't happen because of RoS?

If it did happen SR would be less valid??

Other??

As I interpret it, RoS said nothing about the possible actuallity of absolute simultaneity or even its possible future determination.
It said that our past conception and assumption of universal clock synchronization and determinate simultaneity where false. That at the time there was no method of real determination and no valid assumption of actual simultaneity between disparate events.

So even if determination was possible through later science and technology it could not invalidate a claim that was never made. And it would certainly not invalidate conventional clock synchronization.

 

[harrylin]

[..] But it is early days and based on the concept it still appears to hold the possibility of eventual definite determination.

The correlations can only be established afterwards, by means of signalling at <=c. There is no proposal of how the PoR could be broken in principle.

It is safe to assume it won't happen because of RoS?
If it did happen SR would be less valid?? [..]
As I interpret it RoS said nothing about the possible actuallity of absolute simultaneity or even its possible future determination.

Special relativity says that absolute simultaneity cannot be determined. A recent, very elaborate discussion about RoS is here:
https://www.physicsforums.com/showthread.php?t=575332

 

[Austin0]

That to simply assign the time according to coordinate simultaneity, isotropically to its arrival anywhere within a frame, is to implement an implicit assumption of absolute synchronization of the clocks in that system. Which we know is not a valid assumption in SR.

Without this initial assumption and the consequent spacetime location of its arrival or hypothetical arrival, in the initial frame, there is no basis whatsoever for any prediction of where or when it might arrive in another frame.
WOuld you agree?

Not quite. The question of "where" is easy, you arrive wherever the receiver is located. If the teleport works at or below the speed of light, normal physics applies. If it is FTL then the actual speed in any frame tells you when and the where/when coordinates can be transformed by Lorentz as usual,

yes the where in the other frame is decided but the spacetime location of that point in the other frame at the exact instant you teleport is not. The normal procedure is to calculate the spatial coordinate in the initial frame (with the same time reading) that is proximate to the destination coordinate in the other frame. But the site on the other frame could only actually be there at that absolute instant if your system clocks were absolutely simultaneous.
If the clocks are not absolutely simultaneous there is no basis to assign a location or a local time to the arrival event of a absolutely simultaneous translation.
I am picturing something along the lines of electron tunneling. A quantum device that manipulates the probability of your waveform being detected at some distant location. ;-).

 

[GeorgeDishman]

yes the where in the other frame is decided but the spacetime location of that point in the other frame at the exact instant you teleport is not. The normal procedure is to calculate the spatial coordinate in the initial frame (with the same time reading) that is proximate to the destination coordinate in the other frame.

No, you would normally add a delay dependent on the speed of your teleporter communication channel to the time at the source to find the time at the destination in your original frame. (In fact if the distance between the source and destination is constant, you don't even need to change frames.)

But the site on the other frame could only actually be there at that absolute instant if your system clocks were absolutely simultaneous.
If the clocks are not absolutely simultaneous there is no basis to assign a location or a local time to the arrival event of a absolutely simultaneous translation.
I am picturing something along the lines of electron tunneling. A quantum device that manipulates the probability of your waveform being detected at some distant location. ;-).

There is no such thing as absolute simultaneity in quantum tunneling phenomena, they can be described by QED which is entirely relativistic. However, if you tunnelled to Alpha Centauri, you might find the particles of your body randomly strewn over ±4 years, even if they're all at the same location ;-)