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Thread: Measuring the One-Way Speed of Light: Special Relativity, and "Test Theories"

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    Measuring the one-way speed of light, SR, and "test theories"

    This thread is a continuation of a discussion that began here: http://www.bautforum.com/showpost.ph...3&postcount=33

    I contend that all one-way speed measurements, including measurements of the one-way speed of light, are always coordinate-system dependent measurements. I do not believe that this is really an ATM concept at all, but recognize that (at first glance) it could have the appearance of being an ATM concept.

    There are two completely separate issues here: 1) that the various "test theories" of special relativity are typically applied to guide the design of experiments that probe for violations of Lorentz symmetry, and 2) that the interpretation of any one-way speed measurement is always coordinate-system dependent. Although I am personally interested in designing experiments that probe for unique violations of Lorentz symmetry, whether or not any such violation exists is not the primary issue here. For the purposes of this thread, we are only concerned with understanding the coordinate-system dependent (or otherwise) nature of one-way speed of light measurements.

    Here are some of the relevant statements that I have already made on this subject within the parent thread:
    "Special Relativity is just a coordinate system in which the one-way speed of light is defined to be isotropic. This coordinate system (inertial reference system) is convenient in that it can be realized today in any laboratory. An alternate coordinate system in which the one-way speed of light is defined to be anisotropic is just as valid as SR (when both systems are properly specified: see Y.Z. Zhang, Special relativity and its experimental foundations, (1997); http://www.worldscibooks.com/physics/3180.html)." -- http://www.bautforum.com/showpost.ph...3&postcount=33

    The speed of light isn't a measurable quantity within an inertial reference system, it is defined as a constant c. -- http://www.bautforum.com/showpost.ph...3&postcount=20

    The one-way "speed of light" isn't measurable in any coordinate-independent way whatsoever. There is no experimental basis at all for supposing that the speed of light is a constant; such a statement is coordinate-system dependent. -- http://www.bautforum.com/showpost.ph...3&postcount=29

    I referenced a text book in my first post that fully supports what I have said. Here's another well-known reference where you will find this quote on page 499: "When clocks are synchronized according to the Einstein procedure the equality of the velocity of light in two opposite directions is trivial and cannot be the subject of an experiment." -- R. Mansouri & R.U. Sexl, A test theory of special relativity: I. Simultaneity and clock synchronization, General Relativity and Gravitation, Vol. 8, No. 7 (1977). -- http://www.bautforum.com/showpost.ph...3&postcount=31
    Last edited by Aether; 2006-Mar-02 at 10:21 PM.

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    Wrong. Have you read the Gagnon paper?

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    Quote Originally Posted by clj4
    Wrong. Have you read the Gagnon paper?
    I've only skimmed the abstract so far. In the abstract they say "Our results have not yielded a measurable direction-dependent variation of the one-way speed of light. A clear null result is obtained for a hypothesis in which anisotropy of the cosmic background radiation is used to define a preferred reference frame." I can totally buy their null result in terms of "no violation of Lorentz symmetry detected", but as I said in the OP, "whether or not any such violation exists is not the primary issue here".

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    Quote Originally Posted by Aether
    I've only skimmed the abstract so far. In the abstract they say "Our results have not yielded a measurable direction-dependent variation of the one-way speed of light. A clear null result is obtained for a hypothesis in which anisotropy of the cosmic background radiation is used to define a preferred reference frame." I can totally buy their null result in terms of "no violation of Lorentz symmetry detected", but as I said in the OP, "whether or not any such violation exists is not the primary issue here".
    Read the paper, get back to us when you have a clear notion of what your objection to one-way light speed measurements is or what is that you want to communicate to us. So far, neither is clear

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    Actually I am finding your ideas to be very interesting Aether, and I'm trying to understand better. My first question is, are you talking strictly about inertial frames here? Or you would say that inertial frames are defined as frames where the speed of light is isotropic? I would tend to want to define them as frames where no mysterious ficticious forces appear. If you are saying that a nonisotropic speed of light should not be viewed as mysterious, nor should any other consequence of that on the motion of matter, then I fully agree that all coordinate systems are fair game. But is it not normal to expect that anisotropic behaviour should be viewed as mysterious when reference frames exist that give isotropic results? In other words, I'm wondering if we are not all saying the same thing here, that the guts of relativity is not that the speed of light has to be isotropic, it's that there is a whole class of reference frames in which it is isotropic, and how surprising and powerful that is. Perhaps you are correct in your statements about the first part of this sentence, but it's really the latter part that has the physical significance.

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    Lightbulb One-way lightspeed

    In Van Flandern’s paper The Speed of Gravity - What the Experiments Say, the section on “Constancy with Special Relativity”, he says:
    That the speed of light is independent of the speed of its source is unremarkable, since that is a property of all wave motion. However, being independent of the speed of the observer is special. Choosing to synchronize clocks using the Einstein convention automatically makes one-way speed of light independent of the speed of the observer because that assumption is built into the Einstein synchronization method.
    So if the observation of one-way lightspeed is "built in", hence modified by the relativistic factor y = sqrt(1-v^2/c^2) for time and length, then irrespective of the real speed of light, it will appear constant for observers in all reference frames. That is a special characteristic of SR. It further goes on:
    If some other convention were used to synchronize clocks, such as synchronizing them to an underlying common inertial frame (as is done for the Global Positioning System satellites, or when astronomers synchronize phenomena to a barycentric frame using time provided by distant pulsars), then the one-way speed of light would be different in each direction when measured by observers moving with respect to that special frame. The round-trip speed of light uses a single clock to measure elapsed time, and so does not depend on synchronization. But if the rate of an ordinary clock is affected by its speed in a Lorentzian way, which we now know to be the case, then the measured speed of light will appear to be an invariant in all directions. Using a clock whose rate is not affected by its translational speed, for example pulses in the strength of the gravitational field from a compact, massive binary star, would apparently allow the speed of the observer relative to the local mean gravity field to be detected.
    So it will appear that c is invariant. The fact that pulsating clocks will slow traveling through a gravitational field (with the local gravitational field being the preferred reference frame) may be a parallel issue, that such slowing is a physical phenomenon only mimicking SR, so it appears to be compatible. In fact, this may be an unrelated coincidence.

    There is also the possibility, which may be supported by experimental evidence (though I don’t know this), that all measurements of lightspeed will always register as c by our measuring instruments due to the nature of how photons interact with the instrument’s receptors. But that would be another issue, if so. Or, as Ken G said above: ” I'm wondering if we are not all saying the same thing here, that the guts of relativity is not that the speed of light has to be isotropic, it's that there is a whole class of reference frames in which it is isotropic, and how surprising and powerful that is.” That appears to be closer to what the experimenters see.

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    Quote Originally Posted by Ken G
    Actually I am finding your ideas to be very interesting Aether, and I'm trying to understand better.
    Thanks Ken G. I'm not trying to present anything new or ATM in this thread, only trying to understand and teach what is already well-known and accepted.

    My first question is, are you talking strictly about inertial frames here?
    No, I'm talking about coordinate systems in general. However, there are two well-known and empirically equivalent coordinate systems that are particularly interesting (e.g., inertial frames and Lorentz ether frames).

    Or you would say that inertial frames are defined as frames where the speed of light is isotropic?
    Inertial frames are defined as frames wherein the one-way speed of light is isotropic.

    I would tend to want to define them as frames where no mysterious ficticious forces appear. If you are saying that a nonisotropic speed of light should not be viewed as mysterious, nor should any other consequence of that on the motion of matter, then I fully agree that all coordinate systems are fair game. But is it not normal to expect that anisotropic behaviour should be viewed as mysterious when reference frames exist that give isotropic results? In other words, I'm wondering if we are not all saying the same thing here, that the guts of relativity is not that the speed of light has to be isotropic, it's that there is a whole class of reference frames in which it is isotropic, and how surprising and powerful that is. Perhaps you are correct in your statements about the first part of this sentence, but it's really the latter part that has the physical significance.
    There are two empirically equivalent coordinate systems to choose from, and it often does make quite a lot of sense to use inertial coordinates rather than Lorentz ether coordinates; but this is not necessarily so when probing for possible violations of Lorentz symmetry is the issue. In particular, casual users of inertial coordinate systems typically harbor a false belief that the isotropy of the one-way speed of light is an empirically determined fact...it isn't.

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    Quote Originally Posted by nutant gene 71
    So if the observation of one-way lightspeed is "built in", hence modified by the relativistic factor y = sqrt(1-v^2/c^2) for time and length, then irrespective of the real speed of light, it will appear constant for observers in all reference frames. That is a special characteristic of SR.
    Gamma is used in precisely the same way for both inertial coordinates (SR) and Lorentz ether coordinates, so that isn't what makes the one-way speed of light different between these two coordinate systems.

    It further goes on: So it will appear that c is invariant. The fact that pulsating clocks will slow traveling through a gravitational field (with the local gravitational field being the preferred reference frame) may be a parallel issue, that such slowing is a physical phenomenon only mimicking SR, so it appears to be compatible. In fact, this may be an unrelated coincidence.
    The author seems to be proposing a mechanism for absolute time-keeping. Isn't this the same guy who claims that gravitational forces propagate instantaneously? If so, then I think that's implicit within his proposal here. Nevertheless, even if we had an instantaneously propagating signal with which to synchronize spatially separated clocks, the coordinate-system dependent nature of all speed measurements would still be an issue.

    There is also the possibility, which may be supported by experimental evidence (though I don’t know this), that all measurements of lightspeed will always register as c by our measuring instruments due to the nature of how photons interact with the instrument’s receptors. But that would be another issue, if so.
    No, measurements of light speed always register as c when we synchronize our clocks using the Einstein clock synchronization convention (or by a different procedure called "slow clock transport").

    Or, as Ken G said above: ” I'm wondering if we are not all saying the same thing here, that the guts of relativity is not that the speed of light has to be isotropic, it's that there is a whole class of reference frames in which it is isotropic, and how surprising and powerful that is.” That appears to be closer to what the experimenters see.
    I hope that we can reach a consensus on this here, but everyone isn't on the same page yet.

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    Quote Originally Posted by clj4
    Read the paper, get back to us when you have a clear notion of what your objection to one-way light speed measurements is or what is that you want to communicate to us. So far, neither is clear
    I have read the paper: D.R. Gagnon et al., Guided-wave measurement of the one-way speed of light, Physical Review 38A(4), 1767 (1988); http://imaginary_nematode.home.comca...et_al_1988.pdf.

    In Eq. (8) of the paper, the authors show correctly (for absolute motion in the x-z plane) how a waveguide cutoff frequency in the laboratory frame transforms into a cutoff frequency in the absolute frame . Although this was proven using Eqs. (5), (6), and (7), please note that it is also fully consistent with Eqs. (1) and (4); and in fact, all frequencies transform between these two coordinate systems quite simply according to .

    These authors run into trouble, however, in the last sentence of the first paragraph on p. 1769 where they claim this:
    "...if the phase of the wave on an ideal waveguide at cutoff is compared with the phase of a plane wave in free space, it is found that the phase difference is linearly dependent on the absolute velocity of the experimental reference frame."

    No, it isn't. The frequency of the plane wave in free space transforms between the two coordinate systems in precisely the same way as the frequency of the wave on the ideal waveguide at cutoff. Therefore, the measurable phase difference between these two waves is unaffected by a transformation of coordinates.

    Let's get something straight: a transformation of coordinates simply can't change the outcome of an experiment.

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    Quote Originally Posted by Aether
    I have read the paper: D.R. Gagnon et al., Guided-wave measurement of the one-way speed of light, Physical Review 38A(4), 1767 (1988); http://imaginary_nematode.home.comca...et_al_1988.pdf.

    In Eq. (8) of the paper, the authors show correctly (for absolute motion in the x-z plane) how a waveguide cutoff frequency in the laboratory frame transforms into a cutoff frequency in the absolute frame . Although this was proven using Eqs. (5), (6), and (7), please note that it is also fully consistent with Eqs. (1) and (4); and in fact, all frequencies transform between these two coordinate systems quite simply according to .

    These authors run into trouble, however, in the last sentence of the first paragraph on p. 1769 where they claim this:
    "...if the phase of the wave on an ideal waveguide at cutoff is compared with the phase of a plane wave in free space, it is found that the phase difference is linearly dependent on the absolute velocity of the experimental reference frame."

    No, it isn't. The frequency of the plane wave in free space transforms between the two coordinate systems in precisely the same way as the frequency of the wave on the ideal waveguide at cutoff. Therefore, the measurable phase difference between these two waves is unaffected by a transformation of coordinates.

    Let's get something straight: a transformation of coordinates simply can't change the outcome of an experiment.

    Aren't you missing a very important point?
    The sentence that you quoted above is taken out of context. The whole theoretical underpinning of the paper is the "test theory" developed by the authors. In this theory, called GGT (somewhat similar to Robertson-Mansouri-Sexl), only one frame exhibits light speed isotropy. So, the statement that you just quoted out of context referrs to GGT, not to SR as you would want us to believe it. Starting from equation (1) the whole background is GGT.
    The authors proceed with running the experiment, comparing the results against the predictions of GGT and conclude with disproiving GGT.

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    Quote Originally Posted by clj4
    Aren't you missing a very important point?
    The sentence that you quoted above is taken out of context. The whole theoretical underpinning of the paper is the "test theory" developed by the authors. In this theory, called GGT (somewhat similar to Robertson-Mansouri-Sexl), only one frame exhibits light speed isotropy. So, the statement that you just quoted out of context referrs to GGT, not to SR as you would want us to believe it. Starting from equation (1) the whole background is GGT.
    What I said applies just as well to the Lorentz transform as it does for the GGT/Mansouri-Sexl transform.

    The authors proceed with running the experiment, comparing the results against the predictions of GGT and conclude with disproiving GGT.
    If my analysis is correct, then GGT predicts a null result.

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    Quote Originally Posted by Aether
    What I said applies just as well to the Lorentz transform as it does for the GGT/Mansouri-Sexl transform.

    If my analysis is correct, then GGT predicts a null result.
    Both above statements contradict the paper (which was fully refereed). Can you prove it mathematically, not with words?
    If you manage to prove it mathematically you could have a paper worth publishing.

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    Quote Originally Posted by clj4
    Both above statements contradict the paper (which was fully refereed).
    Yes, I challenge the veracity of the paper. I have looked for subsequent papers referencing this one, and haven't found any. D.R. Gagnon's name isn't to be found anywhere at www.arxiv.org, nor in Zhang's book which references 236 other papers/books.

    Can you prove it mathematically, not with words?
    Prove what? That if you transform the coordinates from one-half of your experiment into a different frame, then you should also transform the other one-half of your experiment's coordinates into that same frame?

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    Quote Originally Posted by Aether
    Yes, I challenge the veracity of the paper. I have looked for subsequent papers referencing this one, and haven't found any. D.R. Gagnon's name isn't to be found anywhere at www.arxiv.org, nor in Zhang's book which references 236 other papers/books.

    Hey, the paper was published in Physical Review A, fully refereed. When you start with the type of arguments like the one above, the discussion is closed.

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    Quote Originally Posted by clj4
    Hey, the paper was published in Physical Review A, fully refereed. When you start with the type of arguments like the one above, the discussion is closed.
    OK.

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    Testy, testy, guys. I for one hope the discussion stays open, as this is a very interesting issue. I note that having a paper refereed is certainly an important issue and basically means there are no obvious errors, but it doesn't mean there are no subtle errors. Can we find a simple explanatory case there the two points of view would make different predictions in a nicely intuitive gedankenexperiment, even if we can't carry it out?

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    Quote Originally Posted by Ken G
    Testy, testy, guys. I for one hope the discussion stays open, as this is a very interesting issue. I note that having a paper refereed is certainly an important issue and basically means there are no obvious errors, but it doesn't mean there are no subtle errors.
    I'm new here. Doesn't this forum have any policy that requires a poster to defend the reference(s) that they cite? It seems to me that by refusing to defend your own reference(s), then you have necessarily forfeited your right to rely on it/them. I wouldn't be completely averse to writing a rebuttal to this particular paper and submitting it to Physical Review A, but we would be stuck here for years if I have to do that for every paper on this list (see esp. sec 3.2 One-Way Tests of Light-Speed Isotropy): "Note that while these experiments clearly use a one-way light path and find isotropy, they are inherently unable to rule out a large class of theories in which the one-way speed of light is anisotropic...All of these theories predict null results for these experiments." --http://math.ucr.edu/home/baez/physic...ne-way%20tests.

    Can we find a simple explanatory case there the two points of view would make different predictions in a nicely intuitive gedankenexperiment, even if we can't carry it out?
    These two coordinate systems (or "points of view") are empirically equivalent as far as classical physics goes. There is no (classical) case in which the two points of view would make different predictions. Different (classical) predictions are made only when Lorentz symmetry is violated, and as I said in the OP "whether or not any such violation exists is not the primary issue here".

    Some people assume that because these two coordinate systems are empirically equivalent (classically) then any distinction between them is irrelevant, but that's not true. For example, there are some indications "...that a consistent formulation of quantum mechanics demands the existence of a preferred frame.":

    From the abstract:
    "In this paper the relativistic quantum mechanics (QM) is considered in the framework of the nonstandard synchronization scheme...Our results support expectations of other authors [J.S. Bell, in Quantum Gravity, edited by C.J. Isham, R. Penrose, and D.W. Sciama (Oxford University Press, Oxford 1981), p. 611; P.H. Eberhard, Nuovo Cimento B 46, 392 (1978)] that a consistent formulation of quantum mechanics demands the existence of a preferred frame.",

    and, from the first page:
    "The formulation of the Poincare-covariant quantum mechanics presented here seems to have a number of advantages over the standard formulation. First of all, the conflict between the causality and the quantum theory disappears. Second, the localization problem is solved." -- P. Caban et al., Lorentz-covariant quantum mechanics and preferred frame, Physical Review A 59(6), 4187 (1999); http://www.arxiv.org/abs/quant-ph/9808013.

    So, although these two coordinate systems are empirically equivalent as far as classical physics goes, the alternate system may turn out to be ultimately superior.

    If we were to assume that simply because these statements were published in Physical Review A then they are beyond questioning, then relativity is toast.

    Also, note that Eq. (5) of (D.R Gagnon et al., 1988) gives the vacuum wave equation obtained from Maxwell's equations formulated "in a reference frame moving with absolute velocity v.". This paper references another paper (T. Chang, Maxwell's equations in anisotropic space, Physics Letters 70A(1), 1 (1979)) wherein not only are Maxwell's equations in anisotropic space given in Eq. (10), but also the contravariant metric tensor is given in Eq. (6).
    Last edited by Aether; 2006-Mar-04 at 11:11 PM.

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    OK, that's a little technical, but I have a sense of what you're saying. What I meant by a gedankenexperiment would be a challenge for the other view, that there is an experiment where a formulation with a nonisotropic speed of light would make an incorrect prediction. Aether has claimed that no such experiment exists, so I would rather think the burden of proof falls on those who would claim it does. Aether, have you looked at the thread under Q&A that talks about the explanation of geostationary orbits? This is a look at the role of coordinate systems in a purely nonrelativistic context, and I for one would like to know how your point of view projects onto the nonrelativistic scene. Specifically, it seems to me that noninertial reference frames do have a meaning in nonrelativistic contexts, and you get the conclusion that inertial frames are those in which there are no strangely behaving forces that break action/reaction symmetry, etc. Why is it not relevant to consider the extension of such a definition into the relativistic realm, and then look at the ramifications for the one-way speed of light? I feel that Occam's razor plays a key role in the pedagogical choices we make in regard to the one-way speed of light in the reference frames of greatest interest.

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    one way speed of light

    Quote Originally Posted by Ken G
    OK, that's a little technical, but I have a sense of what you're saying. What I meant by a gedankenexperiment would be a challenge for the other view, that there is an experiment where a formulation with a nonisotropic speed of light would make an incorrect prediction. Aether has claimed that no such experiment exists, so I would rather think the burden of proof falls on those who would claim it does. Aether, have you looked at the thread under Q&A that talks about the explanation of geostationary orbits? This is a look at the role of coordinate systems in a purely nonrelativistic context, and I for one would like to know how your point of view projects onto the nonrelativistic scene. Specifically, it seems to me that noninertial reference frames do have a meaning in nonrelativistic contexts, and you get the conclusion that inertial frames are those in which there are no strangely behaving forces that break action/reaction symmetry, etc. Why is it not relevant to consider the extension of such a definition into the relativistic realm, and then look at the ramifications for the one-way speed of light? I feel that Occam's razor plays a key role in the pedagogical choices we make in regard to the one-way speed of light in the reference frames of greatest interest.

    I believe I chased down, many moons ago, an article on the one way speed of light, by Stephan (Stefan?) Marinov...a Hungarian physicist. His theoretical rationale on the subject was realistic. Much controversy surrounded his thinking...circa 1982.. It might be helpful here though. Pete.

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    Quote Originally Posted by trinitree88
    I believe I chased down, many moons ago, an article on the one way speed of light, by Stephan (Stefan?) Marinov...a Hungarian physicist. His theoretical rationale on the subject was realistic. Much controversy surrounded his thinking...circa 1982.. It might be helpful here though. Pete.
    Yes, look at 6-th entry from the top. No one managed to duplicate his "experiment"

    http://www.crank.net/einstein.html

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    Ok

    Quote Originally Posted by clj4
    Yes, look at 6-th entry from the top. No one managed to duplicate his "experiment"

    http://www.crank.net/einstein.html
    OK. I generally try to stay out of SR disproofs, as I believe it's valid. The only thing I remember from his article then was that nobody had ever attempted the one-way measurement. Has that changed?

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    Quote Originally Posted by Aether
    I'm new here. Doesn't this forum have any policy that requires a poster to defend the reference(s) that they cite?
    No, the forum requires that you defend your statements. For the time being you haven't done it.


    It seems to me that by refusing to defend your own reference(s), then you have necessarily forfeited your right to rely on it/them.
    This is a diversion. I refused to continue the conversation when your "argument" was nothing but an attack on the paper author. Reminder:

    http://www.bautforum.com/showpost.ph...3&postcount=13


    I wouldn't be completely averse to writing a rebuttal to this particular paper and submitting it to Physical Review A, but we would be stuck here for years if I have to do that for every paper on this list
    No, you were asked to defend your (incorrect) statements about ONE specific paper. In writing, on this website and with math, not with words. What I told you is that IF you managed that, THEN you MIGHT have a paper worth publishing.


    (see esp. sec 3.2 One-Way Tests of Light-Speed Isotropy): "Note that while these experiments clearly use a one-way light path and find isotropy, they are inherently unable to rule out a large class of theories in which the one-way speed of light is anisotropic...All of these theories predict null results for these experiments." --http://math.ucr.edu/home/baez/physic...ne-way%20tests.
    Yes, the famous Tom Roberts quote. Taken out of context (again).
    If you look down the list, you see all the experiments that :

    1. managed to measure one way speed of light with very high degree of precision
    2. found anisotropies of the level of 3 to 100ms, well within very tight error bars

    All the test theories were created for this purpose, they cannot be refuted, they are MADE to look exactly like SR. Otherwise Robertson, Mansouri and Sexl would have been laughed at.

    These two coordinate systems (or "points of view") are empirically equivalent as far as classical physics goes. There is no (classical) case in which the two points of view would make different predictions. Different (classical) predictions are made only when Lorentz symmetry is violated, and as I said in the OP "whether or not any such violation exists is not the primary issue here".
    So, what are you trying to prove? There is no way of disproving RMS, all the experiments on OWLS come back showing violations well within the error bars.
    Do you want us to suggest an experiment that would separate SR from RMS?
    If we knew about it, we wouldn't tell you, we would try to run it, write a paper and become famous

    Some people assume that because these two coordinate systems are empirically equivalent (classically) then any distinction between them is irrelevant, but that's not true. For example, there are some indications "...that a consistent formulation of quantum mechanics demands the existence of a preferred frame.":

    From the abstract:
    "In this paper the relativistic quantum mechanics (QM) is considered in the framework of the nonstandard synchronization scheme...Our results support expectations of other authors [J.S. Bell, in Quantum Gravity, edited by C.J. Isham, R. Penrose, and D.W. Sciama (Oxford University Press, Oxford 1981), p. 611; P.H. Eberhard, Nuovo Cimento B 46, 392 (1978)] that a consistent formulation of quantum mechanics demands the existence of a preferred frame.",

    and, from the first page:
    "The formulation of the Poincare-covariant quantum mechanics presented here seems to have a number of advantages over the standard formulation. First of all, the conflict between the causality and the quantum theory disappears. Second, the localization problem is solved." -- P. Caban et al., Lorentz-covariant quantum mechanics and preferred frame, Physical Review A 59(6), 4187 (1999); http://www.arxiv.org/abs/quant-ph/9808013.

    So, although these two coordinate systems are empirically equivalent as far as classical physics goes, the alternate system may turn out to be ultimately superior.

    If we were to assume that simply because these statements were published in Physical Review A then they are beyond questioning, then relativity is toast.
    What is the connection to our subject? Is SR "toast" and we don't know about it?????? Why don't you stick to the subject?

    Also, note that Eq. (5) of (D.R Gagnon et al., 1988) gives the vacuum wave equation obtained from Maxwell's equations formulated "in a reference frame moving with absolute velocity v.". This paper references another paper (T. Chang, Maxwell's equations in anisotropic space, Physics Letters 70A(1), 1 (1979)) wherein not only are Maxwell's equations in anisotropic space given in Eq. (10), but also the contravariant metric tensor is given in Eq. (6).

    Again, your point????

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    Quote Originally Posted by Ken G
    OK, that's a little technical, but I have a sense of what you're saying. What I meant by a gedankenexperiment would be a challenge for the other view, that there is an experiment where a formulation with a nonisotropic speed of light would make an incorrect prediction. Aether has claimed that no such experiment exists, so I would rather think the burden of proof falls on those who would claim it does.
    I'm claiming that there is no classical experiment for which a different outcome is predicted by the two coordinate systems. The absolute coordinate system is precisely equivalent in every case to doing two Lorentz transforms instead of one. Pick a first arbitrary inertial frame, and define that as the preferred frame. Then use the Lorentz transform to convert coordinates from a second arbitrary inertial frame into the coordinates of the preferred frame, and from there use the Lorentz tranform again to convert the coordinates of the preferred frame into those of a third arbitrary inertial frame. It is only the definition of this arbitrarily preferred frame that differentiates the two systems. In SR the step(s) of transforming coordinates through the preferred frame is skipped, and the transform happens directly between the second and third arbitrary frames.

    Aether, have you looked at the thread under Q&A that talks about the explanation of geostationary orbits? This is a look at the role of coordinate systems in a purely nonrelativistic context, and I for one would like to know how your point of view projects onto the nonrelativistic scene. Specifically, it seems to me that noninertial reference frames do have a meaning in nonrelativistic contexts, and you get the conclusion that inertial frames are those in which there are no strangely behaving forces that break action/reaction symmetry, etc.
    I haven't looked at it. There are lots of "ugly" side-effects to using this alternate coordinate system: for example, momentum is anisotropic in these coordinates and isn't conserved in the same way as with inertial coordinates.

    Why is it not relevant to consider the extension of such a definition into the relativistic realm, and then look at the ramifications for the one-way speed of light?
    It is perfectly reasonable to do that for many practical purposes, but it becomes unreasonable when (false) claims are made that "we have measured the one-way speed of light, and we have found that it is isotropic". Such a (false) claim represents an unfair threat to anyone who would postulate otherwise.

    I feel that Occam's razor plays a key role in the pedagogical choices we make in regard to the one-way speed of light in the reference frames of greatest interest.
    Occam's razor is a razor; not a clock, and not a ruler. It's perfectly reasonable to use inertial coordinates for many things, but that doesn't mean that the one-way speed of light actually is isotropic.

  24. #24
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    Quote Originally Posted by trinitree88
    OK. I generally try to stay out of SR disproofs, as I believe it's valid. The only thing I remember from his article then was that nobody had ever attempted the one-way measurement. Has that changed?
    Sure:

    http://math.ucr.edu/home/baez/physic...ne-way%20tests

  25. #25
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    Quote Originally Posted by clj4
    No, the forum requires that you defend your statements. For the time being you haven't done it.
    OK, I would like to do that, but can't proceed past "discussion is closed". If you object to something, then let's just quarantine that rather than stop everything.

    This is a diversion. I refused to continue the conversation when your "argument" was nothing but an attack on the paper author. Reminder:

    http://www.bautforum.com/showpost.ph...3&postcount=13
    This isn't a diversion, and I certainly was not attacking the paper author. I was just saying that I had made an effort to find references to this paper and author (because presumaby anything that they had to say about this paper would be quite relevant here).

    No, you were asked to defend your (incorrect) statements about ONE specific paper. In writing, on this website and with math, not with words. What I told you is that IF you managed that, THEN you MIGHT have a paper worth publishing.
    OK, I would like to do that, but can't proceed if the discussion is terminated prematurely.

    Yes, the famous Tom Roberts quote. Taken out of context (again).
    If you look down the list, you see all the experiments that :

    1. managed to measure one way speed of light with very high degree of precision
    2. found anisotropies of the level of 3 to 100ms, well within very tight error bars
    I have seen things written by Tom Roberts that I would argue with, but this paper is listed there on Baez' site.

    All the test theories were created for this purpose, they cannot be refuted, they are MADE to look exactly like SR. Otherwise Robertson, Mansouri and Sexl would have been laughed at.
    Exactly. For the purposes of this thread, that is all that is important.

    So, what are you trying to prove? There is no way of disproving RMS, all the experiments on OWLS come back showing violations well within the error bars. Do you want us to suggest an experiment that would separate SR from RMS? If we knew about it, we wouldn't tell you, we would try to run it, write a paper and become famous
    As I said in the OP, "For the purposes of this thread, we are only concerned with understanding the coordinate-system dependent (or otherwise) nature of one-way speed of light measurements."

    Your point ??????
    Again, your point????
    That even though for the purposes of this thread there is no possible classical experiment to distinguish between SR and RMS, that there is still a reason to allow the RMS coordinate system to be discussed, used in research and publication, etc.. False claims that experiments rule-out the RMS coordinate system can be quite damaging and are unfair to those of us who would use/research this coordinate system.

  26. #26
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    Well, answer the questions in a mathematical way. Let's see it.

    That even though for the purposes of this thread there is no possible classical experiment to distinguish between SR and RMS, that there is still a reason to allow the RMS coordinate system to be discussed, used in research and publication, etc.. False claims that experiments rule-out the RMS coordinate system can be quite damaging and are unfair to those of us who would use this coordinate system.
    No one made any "false claims" (or otherwise) relative to RMS. RMS is used routinely in research and in publications.
    I take this as another diversion. Try to stick to the subject.

  27. #27
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    Quote Originally Posted by clj4
    Well, answer the questions in a mathematical way.
    OK, ask me a question in a mathematical way, and then I'll try to answer it in a mathematical way.

    I will try to put something together tomorrow. If you have any questions about it, then please try to be more specific about what it is that you are asking.

    Let's see it.
    Is there a way to make LATEX work here?

    No one made any "false claims" (or otherwise) relative to RMS. RMS is used routinely in research and in publications.
    I take this as another diversion. Try to stick to the subject.
    Any claim that the one-way speed of light is measurable in a coordinate independent way is false.
    Last edited by Aether; 2006-Mar-05 at 02:07 AM.

  28. #28
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    This is starting to sound a little heated, guys...

    Really, what this comes down to is: You have made a claim in your OP, Aether. Can you show us mathematically how your claim works? Further, can you show it to be at least as accurate (if not more) than the mainstream understanding of one-way measurements?

  29. #29
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    Really, what this comes down to is: You have made a claim in your OP, Aether. Can you show us mathematically how your claim works?
    Yes:

    These are the Lorentz transformation equations for relative motion along the x-axis:



    These are the RMS transformation equations for relative motion (with respect to a preferred "ether" frame) along the x-axis:



    Only the time-coordinate differs between these two sets of coordinates.

    In the RMS coordinate system, there is one frame (the preferred "ether" frame) in which the one-way speed of light is defined to be isotropic. In SR the one-way speed of light is defined to be isotropic in all (inertial) frames. There is no (classical) experiment that can distinguish between these two points of view unless Lorentz symmetry is violated.

    Further, can you show it to be at least as accurate (if not more) than the mainstream understanding of one-way measurements?
    What I am talking about is the mainstream understanding of one-way speed measurements, if by "mainstream" you mean fully informed scientists (including, I hope, all readers of this thread by the time we're done). All that I intend to show here (in this thread) is that it the RMS (Robertson-Mansouri-Sexl) coordinate system is empirically equivalent to the inertial coordinate system of SR.

    Note: All I am saying is that measurements of the one-way speed of light are necessarily "coordinate dependent" (e.g., inertial reference frames are "coordinate systems").

  30. #30
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    Quote Originally Posted by Aether
    Yes:

    These are the Lorentz transformation equations for relative motion along the x-axis:



    These are the RMS transformation equations for relative motion (with respect to a preferred "ether" frame) along the x-axis:



    Only the time-coordinate differs between these two sets of coordinates.
    Neither the Lorentz nor the RMS transforms look right, this may be an artifact of the fact that tex didn't work.
    What would have been interesting is your taking the Gagnon experiment through the two sets of transforms to show us how they predict the same exact results (not that I doubt it). This would have been an interesting exercise. For example, Gagnon took his experiment through the GGT transforms and found out that GGT is wrong.
    Brecher, in a different paper took an astronomical experiment through the
    Ritz ballistic theory (c'=c+kv, c"=c-kv) and proved the ballistic theory wrong.
    Can you take us through the computations? It may not be optimal within this thread, maybe putting a short pdf on the web and giving us the link only in this thread.


    In the RMS coordinate system, there is one frame (the preferred "ether" frame) in which the one-way speed of light is defined to be isotropic. In SR the one-way speed of light is defined to be isotropic in all (inertial) frames. There is no (classical) experiment that can distinguish between these two points of view unless Lorentz symmetry is violated.
    Yes, and there was violent agreement throughout the thread. RMS has been "designed" specifically with this in mind. This is a well known fact.

    What I am talking about is the mainstream understanding of one-way speed measurements, if by "mainstream" you mean fully informed scientists (including, I hope, all readers of this thread by the time we're done). All that I intend to show here (in this thread) is that it the RMS (Robertson-Mansouri-Sexl) coordinate system is empirically equivalent to the inertial coordinate system of SR.
    Again, there was violent agreement throughout the thread.
    Where the disagreement lies is in your attempt to discredit the experiments I've sent you starting with the Gagnon (see the misunderstanding on the framework of the Gagnon et. al and the attack on his person). So, a very basic question here: do you agree that the OWLs experiments listed prove that there is no detectable light speed anisotropy?

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