If there was a way of measuring RoS, that would prove the RMS theory false. Since "There is no experiment that could prove that theory false", you have just proved to yourself that there cannot be any experimental test for RoS. Congrats!
Is relativity of simultaneity measurable?
- Thread starter Pete
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If there was a way of measuring RoS, that would prove the RMS theory false. Since "There is no experiment that could prove that theory false", you have just proved to yourself that there cannot be any experimental test for RoS. Congrats!
Fair enough. I'm going to hold you to that, though: you think that the one-way speed of light can be determined experimentally (even if it can't be "directly" measured).
Like I said, I can't find those links. Sorry. Please repost them for me, or link back to wherever you already posted them?
Yeah, I already read that link. It's the one that says "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." As in, certain kinds of one-way isotropy cannot be ruled out experimentally. Which is the exact opposite of what you said.
I said that "I'd love a reference proving me wrong", but instead you chose to respond with a flippant dismissal devoid of content. Please provide links to these RMS papers, or at least something that supports your position. In that last post, you only re-provided one link from earlier, and it directly contradicted what you said. Right now, I have no reason to believe that anything you're saying is true, and neither does anyone else reading this thread.
True. But if that theory is correct, Einstein clock synchronization is wrong. What I said is entirely consistent with my position: it's impossible to show RoS in any "absolute" sense, but given a clock synchronization standard (like Einstein clock synchronization), it's easy to show RoS-by-that-standard.
This is not what I am saying, you can't even quote me correctly.
Good, because this is the standard way OWLS anisotropy is constrained. The experimenters assume by reduction to absurd that light speed is anisotropic and they put a constrain on the "amount of anisotropy" $$\frac{c}{c'}$$. You cannot constrain anisotropy unless you assume a theory that includes it, like the RMS. So, you got it backwards. It is funny to see that you ask me to educate you only to become more belligerent with every explanation.
Then, you will have to rely on the fact that you have proved yourself wrong.
Then you will need to continue your education by yourself. You can start by buying the RMS papers, they are about 40 pounds each and there are three of them. While you are at it, continue to ponder why the mainstream physicists have not come up with a RoS test in the list of SR tests. You have steadfastedly avoided this question, now is the time to start reflecting on it.
You cut the next sentence that said this was getting away from RoS.., you also missed the, "If you have more information...". But you are correct that assumptions are required. They always are.
Your argument is based on an unprovable theory, that does not include RoS??? The exploration of alternate theories is another discussion. RoS is introduced early in Einstein's little book, Relativity, the special and general theory. Much of what follows is built upon the assumptions in that hypothetical. It is OK to question wether an assumption can be experimentally verified, but your argument moves to alternate theories, it begins to questions not only RoS, but much if not all of SR.
Fednis, we are talking about two different things. The point I have been trying to make is that RoS is not limited to the conditions of Einstein's hypothetical. The hypothetical was a tool used to introduce and explain a portion of the developement of SR. It represents an ideal case. It was and is not about events that ARE simultaneous, if it were there would have been no need for the train. It is about observations and measurements of events, being frame dependent.., or relative to the frame of the observer.
Einstein used the ideal case of a hypotheical embankment with measurable simultaneous lightning strikes, because it was a usefull tool to introduce both an assumption about OWLS, M was exactly half way between A and B and did observe the flash from the lightning strikes as simutaneous, hense the speed of light was the same from A to M as it was from B to M.., by adding the train observer the hypothetical demonstrated that those simutaneous events, as observed from the embankment frame, we're not simutaneous from the train frame. It is how the measurement of events in one frame, differ from the measurements from another, that lies at the root of RoS.
The only real reason that it was necessary for the lightning strikes to be truly simutaneous in the embankment frame, was to establish the assumption that OWLS is the same in both directions. It was not necessary to demonstrate RoS. To demonstrate RoS, it would have only been necessary for the observer at M on the embankment to observe the flashes as simultaneous. They did not have to be simutaneous, in any absolute sense. He was moving from the Newtonian view, to the view that simutaneity is relative to the observer.., frame dependent.
RoS is not about two events happening at the same time. It is about the observation of simutaneity being frame dependent. The measurement of any two or more events to be simultaneous is frame dependent. RoS is more about the train's measurements than the embankments.
You said it's possible to infer experimentally that OWLS is the same as TWLS, and surely you agree that the value of TWLS can be measured. Therefore, you say that the value of OWLS can be determined experimentally, by determining the value of TWLS and then inferring that OWLS is the same. There's no way out of that.
Again, I have zero reason to believe that this is true. You haven't provided me a link or anything. You've only given the one site that says the various theories with OWLS anisotropy cannot be experimentally distinguished. If you then turn around and tell me, without citation, that other experiments can put constraints on this anisotropy, I have to assume that you're lying. As always, a link proving me wrong would be great.
I already replied to that post. I said "True. But if that theory is correct, Einstein clock synchronization is wrong. What I said is entirely consistent with my position: it's impossible to show RoS in any "absolute" sense, but given a clock synchronization standard (like Einstein clock synchronization), it's easy to show RoS-by-that-standard."
Tach is back to "teacher mode". Rather than citing evidence for his own claims, he is telling me to shell out money for primary sources to teach myself. Pete: I request that he be given a formal warning.
And regarding the "no experimental test of RoS" thing? It's because a rigorous test of RoS would require a test of OWLS, which is impossible. That's my position, and you're welcome to provide evidence (read: math or links) that it's wrong.
So you agree that assumptions are required. I don't think we disagree on anything substantive, then. The only reason that RoS can't technically be tested is because of these assumptions; if we have to assume some aspects of SR (Einstein clock synchronization) to test others (RoS), then it's not really a "test" in the strictest sense of the term.
Yes, my (actually, Tach's really) argument questions SR. Your punctuation tells me you think that's crazy, but look at this page. Specifically the part that talks about a "remarkable result that a theory maintaining absolute simultaneity is equivalent to special relativity." This isn't fringe stuff; as far as I can tell, it's generally accepted that there are other theories with no RoS that make all the same predictions as SR, and there's no way to prove them wrong. Do scientists actually believe these theories? No. Is this whole argument kind of a technicality? Sure. But when proving things, it's important to consider technicalities, and there's no way out of this one.
As for all the other stuff about Einstein's thought experiments and the real meaning of RoS and whatnot, I get that. In the context of assuming SR is right, it's easy to see the effects of RoS, which is what I'm trying to convince Tach of.
Edit: One important thing to note, that I forgot to mention. Like I said earlier, I'm pretty sure Pete didn't specifically say we were assuming SR in the OP. If he had, you'd be entirely right. But since he didn't, the possibility of invalidating RoS tests by questioning SR is a legitimate loophole.
Just think about changing the medium from vacuum to fiber optic cables. The velocity of light in a cable can be known to the same precission as in vacuum. Clocks today reduce the test lengths to mere meters.... Just a thought.
Careful with the alternates, what they are saying is that some are consistent with SR. What they are not saying is that at least some do not transition to include gravity and GR.., like the Lorentz Ether Model. Indistinguishable from SR, but cannot be modified (yet) to include gravity or the success of GR.
The RMS stuff is all interesting but as example, the M&M Experiemnt is explained both by the Lorentz ether model and SR, through the introduction of Lorentz transformations. All it says is that the speed of light is not measured to be different in different orientations, not that it is not different. They are null results. All it does is prove the experiment cannot detect the ether or a change in the velocity of light, not that there is none in either case. That does not mean there is not useful information there, just be careful, I don't think any of the alternates are as rigorous as SR, even if the only test is that SR is a limited case or GR.
His train was inertial but relativistic. He did not state it specifically but it seems implied.., until he corrects my assumption. In any case the whole discussion would be far more complex if gravity were involved. The underlying "real" meaning or purpose of RoS remains valid even within the context of GR. the mechanics would be unworkable. I mean NASA still plots satellite trajectories using Newton's formulas and then adjusts as they go along. There are too many variables for any practical application of Einstein's field equations... You would no longer have a nice flat spacetime to work with. Add to that RoS was introduced within the context of SR.
No, it's not. Robert Close is a crackpot. Reading that would be a waste of time and would actually harm you because you would be exposed to mistakes about basic physics and speculative claims being presented as if they were facts. I suggest taking the time to read actual works of physics all the way through, not quitting on page three like Farsight admits that he did with Einstein's book on General Relativity. (Yet Farsight claims he is the expert on General Relativity despite never having read the content of the theory.)
The link in post 95 shows that E-synch is conventional, so, falsifying it would not falsify SR, contrary to your claims.
In fact, experimentalists rely routinely on either synchronization in their experiments (read on Opera experiment using slow clock transport, for example).
You demonstrate that you do not understand what you are reading. No mainstream physicist questions SR, the link in post 95 shows ROS to be simply an untestable convention. The tests theories of relativity (RMS, SME) are, contrary to your fringe beliefs the very foundations on which the experiments testing SR (and GR).
You are on the fringe side of the argument, there is a very good reason that there is no RoS test in the list of SR tests. Why is that, Fednis? have you thought about the answer?
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I have already proved you wrong, repeatedly. Let's try a different link, that explains to you how the tests theories I cited to you in post 95 (RMS, SME) really work. The theories assume that there are departures from SR, encapsulated in an array of parameters (4 for RMS, 19 for SME) and they use clever experiments in order to constrain the value of such parameters to ever diminishing but NOT zero values. This explains why these theories :
-can never be ruled out (because the parameters are only converging to zero, but not equal to zero)
-are instrumental in testing SR (and GR, in the case of SME)
The test theories of SR/GR operate exactly the same way the Proca em theory operates in setting up experiments for constraining the mass of photon. The Proca theory can never be ruled out as a valid alternative to Maxwell because the experiments on photon mass have the mass only converging to zero but not zero. In fact, RMS, SME are the foundation of all SR/GR tests. You should educate yourself on the subject.
Irrelevant, invalidating E-clock synch method does not invalidate SR. You should have learned by now on the conventionality of clock synch.
You are outright lying, I have given you ample information, both free and not free, it is up to you to pay for the non-free one, I am under no obligation to give you the papers free. The RMS papers are , contrary to your beliefs, classical in mainstream physics, a person that is ignorant of their content cannot argue the issue intelligently, you should make the effort to acquire them. While you are at it, you should also invest in this book. It will explain away your misconceptions on the subject.
Nope, you "forgot" that other synch methods are used routinely in every day experiments, such as slow clock transport. The RMS papers devote equal time to both synch methods, they explain why neither can be tested, you should really make the effort to read and understand the papers.
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The deviations from the two-way (round-trip) speed of light are given by:
$$\frac{c}{c'}\sim1+\left(\beta-\delta-\frac{1}{2}\right)\frac{v^{2}}{c^{2}}sin^2\theta +(\alpha-\beta+1)\frac{v^{2}}{c^{2}}$$
where :
$$\left(\beta-\delta-\frac{1}{2}\right)=(4\pm8)\times10^{-12}\,$$ ,
constrained by Herrmann, S.; Senger, A.; Möhle, K.; Nagel, M.; Kovalchuk, E. V.; Peters, A. (2009). "Rotating optical cavity experiment testing Lorentz invariance at the 10-17 level". Physical Review D 80 (100): 105011.
$$(\alpha-\beta+1)=-4.8(3.7)\times10^{-8}\,$$
constrained by Tobar, M. E.; Wolf, P.; Bize, S.; Santarelli, G.; Flambaum, V. (2010). "Testing local Lorentz and position invariance and variation of fundamental constants by searching the derivative of the comparison frequency between a cryogenic sapphire oscillator and hydrogen maser". Physical Review D 81 (2): 022003. arXiv:0912.2803. Bibcode:2010PhRvD..81b2003T. doi:10.1103/PhysRevD.81.022003.
As explained earlier to you, the above puts a $$10^{-8}$$ aggregate limit on the anisotropy-encoding parameters (when you multiply this by $$\frac{v^2}{c^2}$$, you get an astounding constraint of $$10^{-17}$$ on $$\frac{c}{c'}$$). Thus, according to mainstream physics, the RMS theory puts a very severe constrain on light speed anisotropy, despite your rude, ignorant and unfounded claims that I am lying. Feel free to procure the two cited papers and study them.
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The first paper is available on arXiv, Rotating optical cavity experiment testing Lorentz invariance.
Both of these are essentially repeats of the M&M experiment with newer technology. They return the same results with greater accuracy... Which is to say they do not detect a change in the velocity of light relative to direction... But they do not change the explanation for that result, from that of the Lorentz Ether Theory and SR. Both explain the invariance as the result of Lorentz transformations, thus Lorentz invariance... Both say that the measurements are relative.
The results remain "null" results explained by the theoretical application of Lorentz transformation of velocity dependent length and time.
It is an error to reference this as any definitive experimental proof of OWLS.
These experiments are testing Lorentz invariance, which is an explanation for the "null results" of all of this class of experiment, that I am aware of.
Edit: The sentence highlighted in red and struck out above, is incorrect and the intent unclear, as has been pointed out by others. I left it as I did because it had been referenced a few times before I had time to address the error.
The reference to OWLS in that sentence should have been to "the speed of light" or "TWLS". In addition it appears that what the comment was referring to was not clear. What was in tended is explained in the following.
The "It" in that sentence was referencing the first of Tach's references, from his quoted post. An experiment in the M&M class of experiments comparring the two way speed of light, between two light paths contained in an apparatus that is rotating. So even though the experiment is not measureing the speed of light it is comparring the speed of light, the two way speed of light, traveling two separate paths and rotating. The data improves on the results of earlier experiments, but continues to return an anistrophy in the comparison of the speed of light between the two light paths. The experimental data is collected over a period of time in which the rotation creates a constantly changing inertial frame of reference, for both light paths. It is my belief that the two way speed of light is indeed constant and uniform at least in the locally weak field it has been measured in.., and the anisotropy of the measurements is frame related.., or the measurements in that experiment are frame dependent.
This class of experiment keeps getting better.., more accurate, but has not yet eliminated all inequity in the comparrison of the TWLS of the two light paths.
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What do you mean by "experimental proof of OWLS"? The sentence makes no sense. . Besides, mainstream physicists, as opposed to you, hold these papers as the standard in experimental constraint of light speed anisotropy.
This isn't and has never been the author's intent, you clearly misinterpret the papers. as an aside, they have nothing to do with MMX nor with Lorentz Ether Theory.
The papers' authors are highly respected experts in the field. What credentials do you have to disparage their work?
You clearly do not understand the papers, nor the theory behind them. The papers show exactly the opposite to what you claim, light speed is not frame dependent.
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This is interesting; I hadn't thought about implications for GR. I'll have to ponder this a bit. Either way, though, we're moving well beyond my area of expertise at this point!
Tach, these are quotes from the arXiv paper of your first reference,
Previous measurements testing the isotropy of the speed of light, often referred to as modern Michelson-Morley experiments,...
The experiment presented here improves on this by one order of magnitude, based on an optimized cavity designand rotation on a precision turntable that allows to mini-mize systematic effects.
The experiment presented here improves on this by one order of magnitude, based on an optimized cavity designand rotation on a precision turntable that allows to mini-mize systematic effects.
They don't mention the LET. I mentioned it because it is indistinguishable from SR and both explain the null results in the same manner.., with Lorentz transformations.
(You use the word "mainstream" and "mainstream physicists", so often they begin to erode credibility.)
Try explaining how Lorentz transformations are not the explaintion, for the constancy of measurements of the speed of light, in different inertial frames.
They are testing Lorentz invariance, are they not? As it relates to the speed of light...?
The papers have nothing to do with LET.
I already pointed out the misconceptions in your post. This doesn't mean that your claim is true:
Not only that you are disparaging the authors' work, you are also making false claims as to the meaning of their work, as above.OnlyMe said:
So, once again, what are your credentials enabling you to disparage the authors' work? Do you have any publications that contradict theirs?
Exactly! You say that E-synch is conventional, and that RoS is an untestable convention. They're both conventional for the exact same reason. You need synchronized clocks to find simultaneity, and you need simultaneity to show relativity thereof. In the RMS framework, the parameter e determines clock synchronization, and it's the only untestable parameter in the framework. If we choose e to be consistent with E-synch, there are no free parameters, and we are left with Lorentz transforms, which clearly show RoS.
Because E-synch (and, by extension, slow clock transport) can't be proven correct. Like I said to OnlyMe, if we have to assign an arbitrary clock convention before testing RoS, it wouldn't be much of a test.
There's a huge difference between saying that something is untestable and saying that it can only be tested to finite experimental precision. The parameter e, which defines clock synchronization and makes RoS a convention, is untestable in the former sense. I guarantee you, when physicists say that RoS is untestable, they never mean that in the sense that RoS-testing experiments will always have uncertainty bounds. They mean it in the sense that rigorous tests of RoS can't be performed.
I definitely get that the synch methods can't be tested, and that E-synch is used as the conventional option. But I don't get how you can say that invalidating E-synch wouldn't invalidate SR. From the Wikipedia page on Test Theories of Special Relativity: "The combination of those three experiments, together with the Poincaré-Einstein convention to synchronize the clocks in all inertial frames, is necessary to obtain the complete Lorentz transformation." (emphasis added) As in, you don't get SR unless you add the E-synch assumption to the experimental evidence. Conversely, given the experimental evidence (with the caveat that all experiments have uncertainty bounds), SR is correct if and only if E-synch is correct.
Thank you for the references. It's not immediately obvious to me whether the authors claim to put bounds on the OWLS; I'll look through the papers further. But in the mean time, maybe you can answer the following. The first paragraph of your "conventionality of simultaneity" link says that the E-synch convention is equivalent to the requirement that the OWLS be equal to the TWLS. But you seem to maintain that while E-synch is an untestable convention, the "OWLS=TWLS" hypothesis can be tested to arbitrary precision, limited only by experimental technology. How is this not self-contradictory?
This jives with my understanding of the issue. The error bounds these guys are putting out are impressive, but there's still that class of theories (with different OWLS) that is in principle indistinguishable from SR, so the cited experiment necessarily can't disprove such theories.