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#280 by kamill85 on 06 Sep, 2017 19:45
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(...)
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.(...)
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.(...)
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.(...)
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.
The only case that results in a time-travel that I can see could be illustrated using a traversable worm hole, where both ends are at coordinates that are at different relative velocities. Say A is at rest B is moving towards (or away from) A at 0.XXc. You cross the tunnel at T=0 from A to B, spend 10 years at B, go back to A at T'=10years and you can either end up at time T=10+(0..N) years or T=10-(10-(10/N)) years (yeah, this can never go negative, but can come infinitely close to zero. At best, you can almost instantly leave A and arrive back, or leave A and come back billion years later. Never in the past though. -
#281 by aceshigh on 07 Sep, 2017 01:25
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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"), etc
Skip 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.
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#282 by meberbs on 07 Sep, 2017 03:41
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All reference frames agree on the causality violation which you would see if you ever actually did the math. They disagree on which leg of the trip time travel happens during, but they agree on the net result. When you refuse to consider the second FTL jump from its own rest frame.(...)
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.
When you don't have a single technical argument against them, and they have spent their life studying the topic? Note that I used the word arrogance, you brought up ignorant.(...)
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.
I said this repeatedly, but you seem to have missed it: all calculations are done before/after the jumps so that the nature of the jumps doesn't matter. What does matter is that since all reference frames are equivalent, you should use the rest frame of the ship just before the jump for consistency.(...)
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.
If you turn off the warp drive, and then the ship is stationary, this means it obviously has a different reference frame than the other ship if the other ship is still moving. If you then accelerate it to 0.7 c or stop the other ship then they have the same reference frame. I seriously don't have a clue how you think this changes or counters anything about what I said.(...)
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. -
#283 by kamill85 on 07 Sep, 2017 10:32
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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"), etc
Skip 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.
Can't find that video, but it sounds like he meant that the Observer could only draw such conclusion, that some event happened way before it could have, ergo time travel, but in reality this would be just a distorted view. If such observer then navigated to a location and asked the inhabitants around, he would learn that all events happened in proper, causally correct order.
That being said, there are few other examples that could fool the Observer, for instance, an A-FTL ship (with instant jumps), could calculate a set of points in a spherical configuration around the Observer and jump to each one at slightly decreased distance, each time generating a flash of lower intensity & wavelength. Observer would then see the same flash appear all at once everywhere around him. To scientist on board it would be hard to figure the event order. Point being, doesn't matter what the Observer can see, reality might be completely different. -
#284 by aceshigh on 07 Sep, 2017 20:28
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here the video, forgot the link
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#285 by WarpTech on 13 Sep, 2017 20:18
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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?
Time dilation in GR is due to the equivalence principle. It is not symmetrical. Someone in a gravity well, will look up and see time moving faster in the rest of the universe, not slower. In general, if anything is "accelerated" to a relativistic velocity delta, "v - v0", it is equivalent to a gravitational field and changing the (Newtonian) gravitational potential. In which case, when it stops accelerating it is at a lower gravitational potential than where it started from.
Nobody would use Lorentz transformations to compare two inertial reference frames that have "different" gravitational potentials. But, that is precisely what we are doing when we assume SR is symmetrical and there is no experiment that can be done to tell which one is moving. I can't find any "relativistic" experiment that actually verifies this assumption. Lorentz transformations are based on it. It is "Math" but has such symmetry been verified physically?
Any assistance or references would be appreciated. -
#286 by 1 on 13 Sep, 2017 21:33
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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?
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. -
#287 by WarpTech on 15 Sep, 2017 04:11
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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?
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.
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#288 by meberbs on 15 Sep, 2017 04:50
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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?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?
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.
Otherwise you are just asking for a wild goose chase, since these experiments solidly confirm the symmetry of special relativity.In 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. -
#289 by WarpTech on 21 Sep, 2017 04:11
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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.In 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;
ds2 = (1/A)*c2dt2 - A*(dx2 + dy2 + dz2)
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. -
#290 by dustinthewind on 21 Sep, 2017 05:24
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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.In 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;
ds2 = (1/A)*c2dt2 - A*(dx2 + dy2 + dz2)
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.
I would be interested to see the rate at which a clock on a space probe ticks that moves to reduce the dipole shift of the CMB as opposed to a clock on a probe which moves to increase the CMB dipole shift. I would wonder if it would be similar to the planes that when moving around the earth in the direction of earth rotation as opposed to a plane moving to oppose earth rotation.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.
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#291 by wavelet on 21 Sep, 2017 07:20
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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, it means that an infinite number of 3-branes can be piled up one over the other along the 4th dimension without us observing this possibility by our eyes.
At relativistic speed it is possible to move into these parallel branes.
It seems that all logical paradoxes of relativity are resolved if this possibility is real.
The actual mechanism has been discussed here:
http://aip.scitation.org/doi/10.1063/1.1867271
Available on ArXiv.
Comments?
I have one: the theory is correct, our present ability to observe reality is very limited...
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#292 by meberbs on 21 Sep, 2017 07:46
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The Hafele and Keating experiment supports no-reciprocity. Even the Michelson-Moorley experiment does not demonstrate reciprocity.
Please demonstrate that this is actually consistent with the Michelson Morley experiment. It seems that anything other than A = constant would basically say that you are no longer dealing with flat spacetime. Michelson Morley experiment, Hafele-Keating, and general synchronization of atomic clocks on the surface of the Earth (and with those on GPS satellites) demonstrate the accuracy of the special relativity portion of time dilation that has A be a constant equal to 1. If you think otherwise, demonstrate how this could possibly not be the case and explain the results of all of these using a variable A between different inertial reference frames.
...
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;
ds2 = (1/A)*c2dt2 - A*(dx2 + dy2 + dz2)
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.
Possibly the clearest demonstration is in the decay times of moving particles. Particles moving in opposing directions in the lab frame would be measured to have different decay times if reciprocity was not true. (If reciprocity was not true then the 2 particles would not see symmetrically the same behavior from the other particle. This would then clearly translate to non-symmetric measurements of them in the lab frame.) Instead experiments all confirm decay times to be dilated consistent with relativity.
Also, units of force scaling consistently does not mean that all the other units do. You made similar claims earlier in the thread, and I demonstrated that other units like velocity did not scale consistently in your system.In the latter time is slow, in the former it's not. No reciprocity, no paradox.
Your last sentence is simply a logical fallacy. Just because reciprocity results in a paradox, does not mean lack of reciprocity can't also result in a paradox. Looking it up, this fallacy is common enough someone gave it its own name: https://en.wikipedia.org/wiki/Denying_the_antecedent
As I have explained before, general relativity and curved spacetime reduce to special relativity in flat spacetime. since things are nice and smooth, slightly curved spacetime will behave very similarly to flat spacetime. If you are lucky, this reduces the amount of time travel in the paradox, but it wouldn't just make it instantly all go away. In fact there are quite a few solutions to general relativity known to be able to produce closed timelike curves.As far as I'm concerned, until someone shows evidence of reciprocity, it is by no means proven.
You have not described what the requirements of such an experiment are. As far as I can tell the listed experiments should cover any reasonable requirements, but it appears you are choosing to not fully consider them because you refuse to accept that flat spacetime is inherently reciprocal. -
#293 by meberbs on 21 Sep, 2017 07:55
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You look for a resolution?
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.
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,
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. -
#294 by wavelet on 21 Sep, 2017 08:18
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"FTL drops you off in another universe" looks like a good answer.
Having x, y, z filled with matter and t almost empty except for t=present time looks like a waste of resources.
In addition "something" should leak out because of quantum indeterminacy.
So if this is true the problem is resolved.
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." -
#295 by meberbs on 21 Sep, 2017 14:33
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Having x, y, z filled with matter and t almost empty except for t=present time looks like a waste of resources.
Even if this was true, it wouldn't make sense to call it a waste of resources. If there is an object at coordinates (x,y,z,t) = (1,2,3,0) (in some arbitrary coordinate system) and then that object moves so that at t = 10, its coordinates are (5,6,7,10). The answer to the question what is at the spacetime coordinates (1,2,3,0) the answer is still "that object"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."
I had only read the abstract of the paper which seemed fine. Looking at the rest, it does not actually support most of its arguments. It does not actually add an extra dimension, but tries to swap the roles of the invariant spacetime interval and time. This does not do what they claim, or really make any sense at all.
They also say:QuoteDespite its success, SR is often affected by ambiguities of interpretation of the results.
They do not actually list a single example where this is true, and I know of no such case. There are results that are unintuitive, but the unituitive results have been experimentally confirmed which they even stated in the previous sentence.
Their conclusions paragraph goes even more off the rails, claiming that there are only 4 "electromagnetically orthogonal" spacetimes, despite never even having defined that term, and the fact that they clearly need an infinite number of "universes" for their theory to hold water.
And then they say:QuoteGravitational 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.
This is the part where in a consistent paper, they would be stating exactly what experiment would need to be done to demonstrate their theory is correct. Technological limitations are irrelevant. -
#296 by RSE on 21 Sep, 2017 20:54
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You look for a resolution?
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.
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,
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)? -
#297 by meberbs on 21 Sep, 2017 21:02
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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.
It is no different than picking the x, y, and z coordinates. All space is just as relative to the particular inertial coordinate system as time is.
How can you define a co-ordinate system without any fixed co-ordinates (along the time axis)?
If you are having trouble recognizing time as a valid dimension, you should first think about it from the perspective of Galilean relativity rather than special relativity. -
#298 by dustinthewind on 22 Sep, 2017 02:05
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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.In 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;
ds2 = (1/A)*c2dt2 - A*(dx2 + dy2 + dz2)
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.
I guess I know Puthoff wrote this equation this way. https://scholar.google.com/scholar?cluster=17157422968110203841&hl=en&as_sdt=0,26
ds2 = (1/K)*c2dt2 - K*(dx2 + dy2 + dz2)
where A=K
I am not sure why he converts c_o*t_o to c*t/K when it seems the conversion should be K*c=c_o and t*sqrt(K)=t_o so c_o*t_o=c*t*K .
However, I found it a bit easier to think of it in terms of the shrunken ruller. For the distance that light traverses over a time in a polarized vacuum greater than 1 or K>1 . (c2/K2)(t2*K)=(c*t)2/K . In that space a person with a ruler measures light but their ruler shrinks by Puthoff's equatons such that dx2/K is the non local length of the persons modified ruler. As a result their ruler scales exactly with the distance traversed by light so that they measure the same exact local speed of light as a person with a non-contracted ruler.
This of course scales the metric such that the metric near gravitational sources shrinks. The gradient in the metric forces a curvature on space and time.
For a non gravitational source that accelerates to reach some relativistic velocity it should gain effective mass , slow in time, and experience length contraction. In their immediate local metric they might even measure the speed of light and still observe a constant speed though with extra Doppler shifting. With Doppler shifting do we have conserved force from photons?
Along with a constant measured speed of light we have other conserved quantities such as Force and something else I am forgetting. Momentum?
This modification of their local metric seems to suggest a frame in which their ruler is normal to a distant observer. Accelerated objects gaining in energy and actually traveling through time unlike non-accelerated objects and hence the twin paradox.
In the case of the plane that moves in the opposite direction of rotation of the earth, it actually decelerates to a lower velocity to go around the earth. As a result its clock speeds up instead of slowing down. Hence my curiosity about a distant space probe moving to reduce the dipole shift of the cmb, away from our local vacuum.
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#299 by Nomadd on 22 Sep, 2017 02:38
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Ask Heisenberg.
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)?
