(...)You are the one trying to conveniently ignore a reference frame. By only picking one reference frame, you are defining a frame for absolute simultaneity. We know that there is no such thing as absolute simultaneity, and for something to be possible, it has to be consistent in any reference frame. The Lorentz transformations are only being applied to the objects just before/after the FTL jumps, so it does not matter what happens during the jump.

(...)You are disagreeing with someone recognized as one of the world's experts on general relativity, and the entire basis of your objection is that his statements don't allow FTL. Do you see the inherent arrogance in your statement?

(...)The inconsistency is the proof. It is called proof by contradiction. FTL has never been demonstrated, however, special relativity has countless supporting experiments. You cannot have both while also maintaining causality.

(...)What "distance delta"? That is simply not a defined term. There are spacetime coordinates of different events in different reference frames, and the Lorentz transformations describe how to translate between them. The relevant events are all taken just before or after the FTL jump, and there is no relevance to how an object moved between the events.

Quote from: meberbs on 09/06/2017 03:36 PM(...)You are the one trying to conveniently ignore a reference frame. By only picking one reference frame, you are defining a frame for absolute simultaneity. We know that there is no such thing as absolute simultaneity, and for something to be possible, it has to be consistent in any reference frame. The Lorentz transformations are only being applied to the objects just before/after the FTL jumps, so it does not matter what happens during the jump.I'm not picking a frame. I'm merely stating that if you want to prove something wrong, your solution must be self-consistent too, right? So to prove A-FTL results in a time travel, time-travel must be observable from all reference frames, not just one. If it's noticeable only from one, then there is a problem of your proof, thus making it invalid.

Quote from: meberbs on 09/06/2017 03:36 PM(...)You are disagreeing with someone recognized as one of the world's experts on general relativity, and the entire basis of your objection is that his statements don't allow FTL. Do you see the inherent arrogance in your statement?So, these days if you want to disagree with someone with a title, you are automatically ignorant? Do you really think it works that way? Sorry to hear that.

Quote from: meberbs on 09/06/2017 03:36 PM(...)The inconsistency is the proof. It is called proof by contradiction. FTL has never been demonstrated, however, special relativity has countless supporting experiments. You cannot have both while also maintaining causality. That's exactly the case here. Special relativity has countless supporting experiments, and they are all based on data where particles travel at <=c through space. Even Lorentz transformations have this embedded so they are not fully adequate for theoretical A-FTL calculations.

Quote from: meberbs on 09/06/2017 03:36 PM(...)What "distance delta"? That is simply not a defined term. There are spacetime coordinates of different events in different reference frames, and the Lorentz transformations describe how to translate between them. The relevant events are all taken just before or after the FTL jump, and there is no relevance to how an object moved between the events.That's not true. If we take points A and B separated by some distance and use regular 0.7c-capable drive to get there in 10 days, and then A-FTL drive but crank down the engine to go at 0.7c as well, they both end up at B at the same time, but their reference frames are not same. While in your different perspective transformations they would be treated as such. That is why if we add A-FTL the the mix you end up with negative-value transformations that are wrong.

gee... another video, from the Starship Conference... you mostly have guys working with FTL here... including the first talk, by Dr Sonny White (the guy from the Warp Drive NASA "ship"), etcSkip to 59 minutes. Talk by Eric Davies.He shows how the LOCAL LIGHT cone can rotate, so that LOCALLY, in a WARP DRIVE OR WORMHOLE (he specifically mentions both too), FTL and Causality are not violated.But even if the LOCAL causality is not violated, he clearly shows that for an outside observer, the ship WILL BE TRAVELLING BACK IN TIME.

I've been looking for an experiment where SR is tested for symmetry. Have there been any tests, where the "observer" has been accelerated to relativistic speeds, and the clock in the laboratory frame was observed to be time-dilated?

Quote from: WarpTech on 09/13/2017 08:18 PMI've been looking for an experiment where SR is tested for symmetry. Have there been any tests, where the "observer" has been accelerated to relativistic speeds, and the clock in the laboratory frame was observed to be time-dilated? The Hafele-Keating experiment is probably the closest thing to what you're looking for. Not quite the same, as the laboratory frame is defined as that of the center of the Earth at rest; and the Earth-surface frame is actually a third 'observer' frame. That said, the three 'observer' frames all behaved as expected within error limits. More importantly, IMO, is that the duration of the test allowed it to both detect and divorce both types of relativistic effects even though the velocities involved aren't traditionally considered relativistic. In principal, it should be very straightforward to do a twin-paradox-esque experiment with today's technology; though I know of no plans to do so.If we relax our definition of 'clock', then we can consider other experiements such as muon lifetime experiements (e.g., Frisch-Smith), where the half-lives of unstable particles increase drastically at relativistic velocities. Running variations of this experiment is quite popular with students today. Perhaps this is more to your liking, as the very existence of the particle itself confirms that the effect is more than a mere mathematical curiosity.

Quote from: 1 on 09/13/2017 09:33 PMQuote from: WarpTech on 09/13/2017 08:18 PMI've been looking for an experiment where SR is tested for symmetry. Have there been any tests, where the "observer" has been accelerated to relativistic speeds, and the clock in the laboratory frame was observed to be time-dilated? The Hafele-Keating experiment is probably the closest thing to what you're looking for. Not quite the same, as the laboratory frame is defined as that of the center of the Earth at rest; and the Earth-surface frame is actually a third 'observer' frame. That said, the three 'observer' frames all behaved as expected within error limits. More importantly, IMO, is that the duration of the test allowed it to both detect and divorce both types of relativistic effects even though the velocities involved aren't traditionally considered relativistic. In principal, it should be very straightforward to do a twin-paradox-esque experiment with today's technology; though I know of no plans to do so.If we relax our definition of 'clock', then we can consider other experiements such as muon lifetime experiements (e.g., Frisch-Smith), where the half-lives of unstable particles increase drastically at relativistic velocities. Running variations of this experiment is quite popular with students today. Perhaps this is more to your liking, as the very existence of the particle itself confirms that the effect is more than a mere mathematical curiosity.Thanks, but it's not quite what I was looking for. The clocks were compared to determine the elapsed time when they were brought back down to the lab. They apparently were not compared when actually in flight.

In which case, when it stops accelerating it is at a lower gravitational potential than where it started from.

Tests of time dilation using particle lifetimes are comparisons while in flight. The most basic test of the symmetry described by special relativity is the Michelson Morley experiment. Can you describe a theory that can accurately predict the results of the above experiments and Michelson Morley, yet diverges for some other test of symmetry?Otherwise you are just asking for a wild goose chase, since these experiments solidly confirm the symmetry of special relativity.Quote from: WarpTech on 09/13/2017 08:18 PMIn which case, when it stops accelerating it is at a lower gravitational potential than where it started from.An object can be accelerated from the ground to Earth orbit, or from Earth orbit to the ground. How exactly can you say that the end result of an acceleration results in a lower gravitational potential in general?To put things another way: the acceleration only is producing the same time dilation as being stationary in a gravitational field while the acceleration is happening. This different time dilation is what makes the difference between the twins in the "twin paradox" which can be solved using Lorentz transformations. Your description of an accelerated object ending up in a lower gravitational potential does not make sense here.

Quote from: meberbs on 09/15/2017 04:50 AMTests of time dilation using particle lifetimes are comparisons while in flight. The most basic test of the symmetry described by special relativity is the Michelson Morley experiment. Can you describe a theory that can accurately predict the results of the above experiments and Michelson Morley, yet diverges for some other test of symmetry?Otherwise you are just asking for a wild goose chase, since these experiments solidly confirm the symmetry of special relativity.Quote from: WarpTech on 09/13/2017 08:18 PMIn which case, when it stops accelerating it is at a lower gravitational potential than where it started from.An object can be accelerated from the ground to Earth orbit, or from Earth orbit to the ground. How exactly can you say that the end result of an acceleration results in a lower gravitational potential in general?To put things another way: the acceleration only is producing the same time dilation as being stationary in a gravitational field while the acceleration is happening. This different time dilation is what makes the difference between the twins in the "twin paradox" which can be solved using Lorentz transformations. Your description of an accelerated object ending up in a lower gravitational potential does not make sense here.The issue is about "Reciprocity" not symmetry.This page, https://en.wikipedia.org/wiki/Time_dilation has a well written section on Reciprocity in SR, "velocity time dilation". Then in the next section on Gravitational time dilation it says;"Contrarily to velocity time dilation, in which both observers measure the other as aging slower (a reciprocal effect), gravitational time dilation is not reciprocal. This means that with gravitational time dilation both observers agree that the clock nearer the center of the gravitational field is slower in rate, and they agree on the ratio of the difference."The Hafele and Keating experiment supports no-reciprocity. Even the Michelson-Moorley experiment does not demonstrate reciprocity. So far, I have not found any experimental evidence to support a reciprocity effect. Gravitational time dilation is the result of the Equivalence principle alone, not any particular solution of GR. Reciprocity is a requirement of the Lorentz transformation and the Lorentz group, it is assumed in its derivation. Reciprocity is what forces the paradox to happen. Reciprocity is not one of the postulates of SR. It is an assumption that reciprocity is required for "The laws of physics to remain invariant in all inertial reference frames". However, it is trivial to show that the law of physics remain unchanged, even when the flat Minkowski metric is transformed by a constant coefficient "A", in such a way that;ds^{2} = (1/A)*c^{2}dt^{2} - A*(dx^{2} + dy^{2} + dz^{2})Resulting in a scaled system of units where "force" is an invariant wrt the constant "A". Leaving all physical laws and experimental data, including EM fields unchanged, but the transformation from A=1 to A>1 is not reciprocal. In the latter time is slow, in the former it's not. No reciprocity, no paradox. IMO this too is the result of the Equivalence principle, when one body accelerates to velocity v=0.6c and the other does not. The end result is not reciprocal.As far as I'm concerned, until someone shows evidence of reciprocity, it is by no means proven.

Considering the Hafele–Keating experiment in a frame of reference at rest with respect to the center of the earth, a clock aboard the plane moving eastward, in the direction of the Earth's rotation, had a greater velocity (resulting in a relative time loss) than one that remained on the ground, while a clock aboard the plane moving westward, against the Earth's rotation, had a lower velocity than one on the ground.

The Hafele and Keating experiment supports no-reciprocity. Even the Michelson-Moorley experiment does not demonstrate reciprocity. ...Reciprocity is a requirement of the Lorentz transformation and the Lorentz group, it is assumed in its derivation. Reciprocity is what forces the paradox to happen. Reciprocity is not one of the postulates of SR. It is an assumption that reciprocity is required for "The laws of physics to remain invariant in all inertial reference frames". However, it is trivial to show that the law of physics remain unchanged, even when the flat Minkowski metric is transformed by a constant coefficient "A", in such a way that;ds^{2} = (1/A)*c^{2}dt^{2} - A*(dx^{2} + dy^{2} + dz^{2})Resulting in a scaled system of units where "force" is an invariant wrt the constant "A". Leaving all physical laws and experimental data, including EM fields unchanged, but the transformation from A=1 to A>1 is not reciprocal.

In the latter time is slow, in the former it's not. No reciprocity, no paradox.

As far as I'm concerned, until someone shows evidence of reciprocity, it is by no means proven.

You look for a resolution?Here we have one:Our space-time has three space dimensions, it means that "physical objects" are distributed on a 3-brane.General Relativity needs 4 dimensions,

Having x, y, z filled with matter and t almost empty except for t=present time looks like a waste of resources.

BTW the linked paper says: "To ensure agreement with these data and to keep a full agreement with the well-known Special Relativity, the proposed model changes our view of reality by giving to “time” the secondary role of derived coordinate. The overall number of fundamental large dimensions is still equal to the observed four, which have now the properties of spatial dimensions."

Despite its success, SR is often affected by ambiguities of interpretation of the results.

Gravitational phenomena can allow navigation in the 4-space and, as soon as technology will permit, it will be possible to discover the possible real existence and nature of the remaining three space-times.

Quote from: wavelet on 09/21/2017 07:20 AMYou look for a resolution?Here we have one:Our space-time has three space dimensions, it means that "physical objects" are distributed on a 3-brane.General Relativity needs 4 dimensions,Spacetime is 4 dimensions not 3. There are 3 spatial dimensions and time. And time is the 4th dimension in GR. GR does not require any dimensions beyond this.If you actually read what you linked you would see the same thing I just said. What they are proposing is a 5th dimension on top of the 4 we are familiar with. Anyway, I believe "FTL drops you off in another universe" has been suggested a couple times in this thread as a resolution. Presumably any such models would require that attempts at using this to time travel would just end up with you in a different universe.

Time as the Fourth dimension confuses me. In the three spatial dimensions, A co-ordinate (x,y,z) can be defined regardless of the inertial reference frame you are in. Yet, by the same rules, time cannot be given a particular co-ordinate point, as there is no "Universal Time", and ll time is relative to the particular inertial reference frame from which it is being measured. How can you define a co-ordinate system without any fixed co-ordinates (along the time axis)?