Aether theories which are experimentally indistinguishable from SR.

[quantumdude]

From [URL='https://www.physicsforums.com/insights/author/john-baez/']John Baez[/URL]’ page on the experimental basis of Special Relativity, he says that:

John Baez[/URL]]
The existing experiments put rather strong experimental constraints on any alternative theory. In particular, Zhang showed that these experimental limits essentially require that any theory based upon the existence of an ether be experimentally indistinguishable from SR, and have an ether frame which is unobservable (the only alternative is for a theory to "live in the error bars" of the experiments, which is quite difficult given the high accuracies achieved by many of these experiments).

and

John Baez[/URL]]
These theories share the property that the round-trip speed of light is isotropic in any inertial frame, but the one-way speed is isotropic only in an ether frame. In all of these theories the effects of slow clock transport exactly offset the effects of the anisotropic one-way speed of light (in any inertial frame), and all are experimentally indistinguishable from SR.

My question pertains to the remarks in blue: aether theories that are experimentally indistinguishable from SR. Where are these theories published? One member (Yogi) makes reference to the so-called Selleri (sp?) transformations, saying that they lead to the same predictions as SR, but are predicated on different premises. The problem is that no one who advocates the “alternative to SR” view ever presents the alternative in sufficient detail. So I’d like to know where Selleri’s theory can be found. I tried Googling it, but there’s nothing out there.

Baez makes reference to “Test Theories” of SR. Might I find what I am looking for here?

Thanks,

 

[yogi]

Hi Tom - Happy Holidays

I will post some links Re Selleri - I can tell you it is basically a theory that derives from assuming the over and back velocity of light as a fact - but it rejects the notion that the one way velocity of light is true. Since you have mentioned Zhang, here is another quote from him. He has three books out - I have one on order - but have not received it yet - when I do I will be happy to discuss his experiments. Anyway, here is what he says in his teaser to his first book entitled: Special Relativity and its Experimental Foundation

"...In the second part, variant types of experiments performed up to now are analyzed and compared to the predictions of SR. This shows that the experiments are a test of the two-way speed of light, but not the one-way speed of light"

Regards

Yogi

 

[yogi]

Tom - here is one citation - don't get the idea I totally endorse everything this guy says - I think he is wrong on his views about Sagnac and GR - but - anyway:
http://redshift.vif.com/JournalFiles/V11NO1PDF/V11N1SEL.pdf.

 

[pervect]

John Bell, in an essay in "Speakable and unspeakable in quantum mechanics" (this essay is the one that introduces the Bell spaceship paradox), is the only example that comes to my mind for an "ether theory that's indistinguishable from SR".

Garth provides another reference inthis thread

There are a lot of non-credible references on the WWW for "ether theories", of course.

 

[Aether]

My question pertains to the remarks in blue: aether theories that are experimentally indistinguishable from SR. Where are these theories published?

Classical electrodynamics is an aether theory:

J. Clerk Maxwell, A dynamical theory of the electromagnetic field, Philos. Trans. Roy. Soc. 155, pgs 459--512 (1865). Abstract: Proceedings of the Royal Society of London 13, pgs 531--536 (1864)

"..we are obliged to admit that the undulations are those of an aethereal substance, and not of the gross matter, the presence of which merely modifies in some way the motion of the aether."

More recently Paul Dirac published this:

P.A.M. Dirac, A new classical theory of electrons, Proc. Roy. Soc. A, 209, 291 (1951).

And in a follow-up letter published in Nature, he said this:

"...It was soon found that the existence of an aether could not be fitted in with relativity, and since relativity was well established, the aether was abandoned...If one re-examines the question in light of present-day knowledge, one finds that the aether is no longer ruled out by relativity, and good reasons can now be advanced for postulating an aether...We can now see that we may very well have an aether, subject to quantum mechanics and conforming to relativity, provided we are willing to consider the prefect vacuum as an idealized state, not attainable in practice. From the experimental point of view, there does not seem to be any objection to this...Thus with the new theory of electrodynamics we are rather forced to have an aether."

P.A.M. Dirac, Nature, 168, 906 (1951).

(as attributed to John Baez) The existing experiments put rather strong experimental constraints on any alternative theory. In particular, Zhang showed that these experimental limits essentially require that any theory based upon the existence of an ether be experimentally indistinguishable from SR, and have an ether frame which is unobservable (the only alternative is for a theory to "live in the error bars" of the experiments, which is quite difficult given the high accuracies achieved by many of these experiments).

What about gravity, all of the matter in the universe, and all of the energy in the universe? Substitute any (or all) of these for "ether" in the above quotation, and see for yourself how utterly misleading such statements are.

I respectfully object to this editorial statement by PF which appears at the head of Special & General Relativity: "Space and time are relative concepts rather than absolute concepts". The Space-time of SR is a relative concept, but it is only valid in the limit as the space-time volume under scrutiny approaches zero. Clearly, it is not valid anywhere in the real world. For example, cosmological time is an absolute concept that is consistent with GR.

 

[yogi]

Another type of aether theory that is gaining a growing number of advocates is the ether inflow theory of gravity. Persons interested may want to read some of Tom Martin's papers on the interent. Tom has proposed a number of tests that would distinquish "in flow" from GR. What is most significant about inflow theory is that it correlates the clock rate given by the LT for the influx velocity with the gravitational slowing of clocks a la GR at the same radius from the mass center.

 

[Garth]

Another aether theory is called "subquantum dynamics" a paper can be found http://home.earthlink.net/~gravitics/Downloads//M-L/M-L.html ,
does anybody understand what it is about?

Garth

 

[wisp]

The jury is out on whether special relativity passes the one-way test. Although the list of references look impressive there are serious misgivings as to whether these are as accurate as they claim to be or indeed if they even qualify for one-way tests.

From John Baez’s post of an article by Tom Roberts in 2000 (Original by Siegmar Schleif and others, 1998).

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. These theories share the property that the round-trip speed of light is isotropic in any inertial frame, but the one-way speed is isotropic only in an ether frame. In all of these theories the effects of slow clock transport exactly offset the effects of the anisotropic one-way speed of light (in any inertial frame), and all are experimentally indistinguishable from SR. All of these theories predict null results for these experiments. See Test Theories above, especially Zhang (in which these theories are called "Edwards frames").
Cialdea, Lett. Nuovo Cimento 4 (1972), p821.
Uses two multi-mode lasers mounted on a rotating table to look for variations in their interference pattern as the table is rotated. Places an upper limit on any one-way anisotropy of 0.9 m/s.

Martin Miller suggests that this test for the anisotropy of light is misguided due to nature not synchronizing clocks according to Einstein’s way. If Martin is right then this test is invalid and cannot be used to qualify as a one-way test. See

http://www.geocities.com/antirelativity/Rotating_Clock_Analysis.html

http://www.geocities.com/antirelativity/

Krisher et al., Phys. Rev. D, 42, No. 2, pp. 731-734, (1990).
Uses two hydrogen masers fixed to the Earth and separated by a 21 km fiber-optic link to look for variations in the phase between them. They put an upper limit on the one-way linear anisotropy of 100 m/s.

Note: In 1990 Krisher et al performed a one-way light experiment by using two hydrogen-maser standards separated by 21km. The light from each maser is split and one-half modulates a laser light that travels one-way along a fibre optics (fiber optics) cable, and the other sent to a local detector. The relative frequency of the local and laser light are compared, and a variation in the frequency should show up due to the ether flowing passed the rotating Earth.
However, the experimental noise is too large to detect an ether flow - that is at rest with respect to the microwave background radiation - of the magnitude suggested by Dayton Miller, and the 5-day duration of the experiment was perhaps too short to detect the sidereal period variation. The experimental result was inconclusive.

Gagnon, Torr, Kolen, and Chang, Phys. Rev. A38 no. 4 (1988), p1767.
A guided-wave test of isotropy. Their null result is consistent with SR.

In 1988 Gagnon, Torr, Kolen and Chang, published the results of their experiment "Guided-wave measurement of the one-way speed of light".
Although they reported, "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", Harold Aspden's considers their work important, as their experimental data clearly shows an eastward motion effect. And so it is possible to sense the speed of a test device using optical speed-of-light sensing wholly confined within the enclosure housing the apparatus.
See Harold Aspden's Lecture No IIIb - One-way speed of light.
http://www.aspden.org/books/Poc/IIIb.html


Other works not covered by Baez are:

Silverthooth’s work puts a stronger case against SR.
In 1986 E W Silvertooth claimed to have measured the 378 km/s cosmic motion using an optical sensor that measures the spacing between standing wave nodes. Although the experiment has not been confirmed, see
See Harold Aspden's Lecture No IIIb - One-way speed of light
http://www.aspden.org/books/Poc/IIIb.html

And Dayton Miller's work, see http://www.orgonelab.org/miller.htm

Clearly there is a need to carry out more one-way tests, in which clocks are not forced into synchronization by Einstein’s way.

 

[Aether]

The jury is out on whether special relativity passes the one-way test. Although the list of references look impressive there are serious misgivings as to whether these are as accurate as they claim to be or indeed if they even qualify for one-way tests...Clearly there is a need to carry out more one-way tests, in which clocks are not forced into synchronization by Einstein’s way.

Cosmological clocks are theoretically ideal for carrying out such one-way tests, but the technology isn't advanced far enough for that quite yet.

The speed of light is locally Lorentz invariant, and is presumed not to vary with the speed or direction of any photon emitter or photon detector whatsoever. Nevertheless, proper time is definitely not Lorentz invariant, and $$\frac{d\tau}{dt}$$ may very well be found to exhibit a dipole anisotropy when the precision of our cosmological clocks becomes good enough to detect it. If so, a locally preferred frame will be identified which corresponds to that frame in which $$\frac{d\tau}{dt}$$ is isotropic.

 

[jtbell]

Tom Roberts has posted extensively in sci.physics.relativity on the subject of ether theories that are experimentally indistinguishable from special relativity. See for example

http://groups-beta.google.com/group/sci.physics.relativity/msg/f46b785e80425dd7

It's the first in a series of three postings. The other two are

http://groups-beta.google.com/group/sci.physics.relativity/msg/dc860f85451a0e54

http://groups-beta.google.com/group/sci.physics.relativity/msg/a6f110865893d962

 

[wisp]

Thanks for the links. I will study this fully, but I can see things are not right from the start. From “Why the Ether is Unobservable” dated November 21, 1999:

The ether has been absent from mainstream physics for almost a century.
There are good reasons for this, the foremost being that the ether is unobservable -- that is, there is no conceivable experiment using light, which could detect its presence.

This opening paragraph is a bit controversial, suggesting that there is no proof of the ether, when there is real evidence to suggest that the detection of the ether is possible, the latest example being the Dewitte experiment.
It also says that there are no ether theories with address the propagation of light that could devise an experiment to detect the ether. This is not true. A one-way experiment similar in nature to the DeWitte experiment would reveal the existence of the ether.

Much of the comments about there being no viable ether theory that can meet the stringent conditions imposed is just not the case.

The closest ether to the truth is:

1.1 Rigid Ether
The original ether theory is that of Fresnel, Maxwell, Michelson and
others, in which the ether permeates all of space, objects move freely
through it without resistance or any other interaction with it, and the
speed of light is c in the rest frame of the ether (because of the
structure of Maxwell's equations). The ether is assumed to be at rest
in some still-to-be-determined global inertial frame.
This theory is refuted by the MMX (and repetitions) and by any
measurement of the speed of light on Earth (which is moving wrt
the ether).

But his comments on the MMX are incorrect.

 

[Aether]

This opening paragraph is a bit controversial, suggesting that there is no proof of the ether, when there is real evidence to suggest that the detection of the ether is possible, the latest example being the Dewitte experiment.

It also says that there are no ether theories with address the propagation of light that could devise an experiment to detect the ether. This is not true. A one-way experiment similar in nature to the DeWitte experiment would reveal the existence of the ether.

wisp, where can I get the complete details on how to reproduce the DeWitte experiment?

 

[russ_watters]

There has got to be an aether theorist willing to fork over the $10,000 or so required to do a tabletop 1-way test. Why hasn't one been done yet? Are they afraid of the answer?

 

[yogi]

Russ - you might be right. But On the other hand there are a number of publications that claim we cannot detect one way velocity using terrestrial sources. There were however some experiments by Silvertooth - discredited of course by mainstream physics - if I am not mistaken he measured the Earth velocity wrt to space as being very close to what we determine from the CBR - but I believe his experiments were performed before the CBR anisotrophy was detected. On the other hand, if his tests really showed what he claimed - why have they not been repeated? Something definitely missing in this story.

wisp -
Would totally concur that anyone who makes a statement that MMx refutes the existence of an ether has no knowledge of the subject matter. Einstein himself stated it had no bearing on the issue - only that it was not necessary to consider it in his derivation of the transforms

 

[yogi]

Russ - one more point. As between SR and LR, there would be nothing proved by such a test since both predict that light is one way isotropic in the Earth frame - SR because of Einsteins postulate, LR because the gravitational field is postulated to create an isotropic local ether that masks the Earth's motion relative to the universe.

 

[russ_watters]

Russ - one more point. As between SR and LR, there would be nothing proved by such a test since both predict that light is one way isotropic in the Earth frame - SR because of Einsteins postulate, LR because the gravitational field is postulated to create an isotropic local ether that masks the Earth's motion relative to the universe.

This just seems too convenient to me - assuming that reality resides in a loophole. Anyway, slowly but surely, the loopholes that aether theories can fit in are getting closed. Eventually, the "local ether" will be the entire universe. In any case, you can see why people would have trouble with this, can't you? Aether theories are predicated on the assumption of an unobserved (and possibly unobservable) flaw in a highly successful theory.

 

[pervect]

One way velocities are strictly a statement about coordinate systems. Coordinate systems don't have any ultimate physical significance - that's why one-way velocities don't, either.

So basically getting hung up on the issue of one-way velocities is a dead end. It doesn't tell you anything more, or different, about what you can measure. Furhtermore, systems with non-isotropic one-way velocities are more complicated to deal with. As I've remarked in another thread, there can be some justification for changing units or coordinates to make the mathematics and the exposition of a theory simpler. In this case, changing to non-isotropic coordinates makes the math and the exposition of a theory harder, not simpler. So it's pretty much a lose-lose proposition.

 

[wisp]

Would totally concur that anyone who makes a statement that MMx refutes the existence of an ether has no knowledge of the subject matter. Einstein himself stated it had no bearing on the issue - only that it was not necessary to consider it in his derivation of the transforms.

I didn’t make this statement; it was quoted by from an article by Tom Roberts in 2000 (Original by Siegmar Schleif and others, 1998) as being the reason why rigid ether was ruled out. I know Einstein claimed that the MMx had no bearing on the development of SR, but it is generally acknowledged as being the main experimental proof that supports the principle of relativity – the speed of light being constant…

A link to the Roland DeWitte experiment (a one-way electrical pulse experiment) is

http://home.planetinternet.be/~pin30390/belgacom.htm

The important points are:
Only something that has a galactic origin can cause a sidereal period variation in the results.
He used three sets of atomic clock standards to ensure accuracy of measurements.
A similar experiment using a laser and two atomic clocks would produce similar findings.

I’m reading Tom Roberts’ three articles about the ether.

 

[pervect]

I'll begin to get excited about the DeWitte experiment when someone replicates it. Besides the total lack of replication, it would be important to rule out effects due to the solar day. One of the first effects that come to mind is very simple, the temperature.

The argument that the period is the sidereal day rather than the solar day does not seem to me to be very a very strong argument, as the periods are very close, and it is unclear that the experiment is really capable of distinguishing between them.

 

[yogi]

Wisp - I know you didn't make the statement - it was a quote - but I am surprised that Tom Roberts would endorse it.

 

[wisp]

Tom Roberts has posted extensively in sci.physics.relativity on the subject of ether theories that are experimentally indistinguishable from special relativity. See for example

http://groups-beta.google.com/group/sci.physics.relativity/msg/f46b785e80425dd7

It's the first in a series of three postings. The other two are

http://groups-beta.google.com/group/sci.physics.relativity/msg/dc860f85451a0e54

http://groups-beta.google.com/group/sci.physics.relativity/msg/a6f110865893d962

I’ve reviewed Tom Roberts’ three articles about the ether and have made the following observations.

Response to article 1 - Theories equivalent to SR.
Tom has classified ether theories into two classes. But there is a third class of ether theory from which the equations used by special relativity can be derived as a limit case. In this class, experiments made by Earth bound observers are approximately equal to the predictions of SR - not exactly equal. And contrary to the claim that no one has found any differences, the work of Dayton Miller, Silvertooth, DeWitte, etc, suggest otherwise.

By limiting the scope to two classes that are exactly equivalent to SR, he then shows that the use of an arbitrary parameter q, together with the use of Lorentz Transformations, results in the inability to measure the anisotropy of the one-way speed of light. This argument is correct, but he has not included the third class, which is the more important, and so missed the point.

Other points about the third class, which are important, are:
The use of Lorentz Transformations is unnecessary, and lengths do not contract.
The mathematical and experimental equivalence becomes closer at low ether speeds, but deviates more at higher speeds. It is never 100% equivalent.

Response to article 2 – Why the ether is Unobservable.
Since this article is based on the first, which misses out the third class of ether theories, it is of limited value. Even so, many of the paragraphs contain factually incorrect statements. And again, he fails to recognize the work of those scientists who have measured the speed of the ether relative to the earth.

Response to article 3 – Why the ether is not part of modern physics.
The third article is based on the author’s opinion of the first and second articles, which are incomplete.
The key word is that SR has symmetry, whereas ether theories do not.
This is false, as ether theories of the third class do have symmetry.

To conclude.
The three articles by Tom Roberts do not include a third class of ether theories from which equations of special relativity can be derived. His articles ignore the work of those scientists whose experiments have detected ether flow.
The assumption that it is not possible to measure the anisotropy one-way speed of light is false.
Of the current one-way tests that Tom references as being supportive of SR, several do not qualify for one-way tests and those that do are not accurate enough to determine whether the ether or SR is true.

Modern experiments to test the anisotropy of the one-way speed of light are needed to determine whether ether or SR is true.

 

[Aether]

A link to the Roland DeWitte experiment (a one-way electrical pulse experiment) is

http://home.planetinternet.be/~pin30390/belgacom.htm

The important points are:
Only something that has a galactic origin can cause a sidereal period variation in the results.

This link doesn't work for me.

In using the specific term galactic origin, I presume that you do not mean to rule out signals having a more general cosmological origin?

 

[Chronos]

Pardon the characterization, but Tom Roberts is about as credible as Setterfield and Van Flanders. What is the point of 'discovering' an aether theory that is experimentally indistinguishable from SR?

 

[yogi]

Chronos - because it may lead to an understanding of what space is, e.g., a physical dynamic that explains the difference in aging as opposed to kinematical relationships

 

[wisp]

This link doesn't work for me.

In using the specific term galactic origin, I presume that you do not mean to rule out signals having a more general cosmological origin?

I've rechecked the link and it's correct, but it's off line at present. Try again in a day or so. The DeWitte experiment ran for 178 days and used 6 atomic clock standards. The results showed that there was a clear sidereal period variation, which was not the same as the solar period. So what caused the change was not due to something on the Earth (solar period) but something of cosmological or galactic origin (sidereal period).

Thanks for the correction.

 

[Aether]

I've rechecked the link and it's correct, but it's off line at present. Try again in a day or so. The DeWitte experiment ran for 178 days and used 6 atomic clock standards. The results showed that there was a clear sidereal period variation, which was not the same as the solar period. So what caused the change was not due to something on the Earth (solar period) but something of cosmological or galactic origin (sidereal period).

Thanks for the correction.

My pleasure, and thanks for the link. I am interested in personally carrying out a modernized version of De Witte's experiment, but can't make a solid reference to his work using just this feeble web link. There needs to be a permanent record of the experiment somewhere like arXiv.org so that there is something to shoot at. Until then, there is no De Witte experiment, is there?

 

[wisp]

My pleasure, and thanks for the link. I am interested in personally carrying out a modernized version of De Witte's experiment, but can't make a solid reference to his work using just this feeble web link. There needs to be a permanent record of the experiment somewhere like arXiv.org so that there is something to shoot at. Until then, there is no De Witte experiment, is there?

Within the last day or so the link to the DeWitte experiment has moved. It is now at

http://www.ping.be/~pin30390/belgacom.htm

 

[Aether]

Cosmological clocks are theoretically ideal for carrying out such one-way tests, but the technology isn't advanced far enough for that quite yet.

The speed of light is locally Lorentz invariant, and is presumed not to vary with the speed or direction of any photon emitter or photon detector whatsoever. Nevertheless, proper time is definitely not Lorentz invariant, and $$\frac{d\tau}{dt}$$ may very well be found to exhibit a dipole anisotropy when the precision of our cosmological clocks becomes good enough to detect it. If so, a locally preferred frame will be identified which corresponds to that frame in which $$\frac{d\tau}{dt}$$ is isotropic.

1) New interpretation of the result of my experiment performed at Belgacom in 1991.

With the hypothesis that the electromagnetic radiations propagate at the same velocity in the coaxial cable while seen from the rest frame, an anisotropy of the speed on Earth is expected, but unfortunately this anisotropy is not directed towards Leo (11 h), but out of phase of 6 hours of right ascension.

Here, with the new hypothesis, that the velocity in the cable is invariant in the moving frame, we are led to affirm that it is not the anisotropy of the light speed which has been detected, but the absolute time dilation. This time, the anisotropy is in agreement with the frequency anisotropy of the microwave background.

Great! De Witte has come to interpret his results as a confirmation of the one-way isotropy of the speed of light, and an anisotropy of proper time. What of this, wisp?

 

[wisp]

Aether

I believe the DeWitte results support anisotropy in the one-way speed of light, but I do not believe his new interpretation is correct.
I will get back to you with an answer soon (I broke my arm on Friday and I am in some pain).

 

[Aether]

Aether

I believe the DeWitte results support anisotropy in the one-way speed of light, but I do not believe his new interpretation is correct.
I will get back to you with an answer soon (I broke my arm on Friday and I am in some pain).

Best wishes for a speedy recovery, wisp.

 

[yogi]

Yes Speedy recovery - last time that happened to me it was because I was patting myself on the back.

 

[quantumdude]

Tom - here is one citation - don't get the idea I totally endorse everything this guy says - I think he is wrong on his views about Sagnac and GR - but - anyway:
http://redshift.vif.com/JournalFiles/V11NO1PDF/V11N1SEL.pdf.

Thanks, that looks like one example of what I was asking about. If I don't find what I need in the text, then the bibliography looks like it will lead to a fruitful paper chase.

 

[quantumdude]

Classical electrodynamics is an aether theory:

Not in the sense that I am talking about it isn't. In the context of this thread an "aether theory" is a theory that asserts the existence of a preferred frame of reference, but still yields experimental predictions that match those of SR. Suggesting that EM fits the bill is like giving me an an orange when I asked for an apple.

"...It was soon found that the existence of an aether could not be fitted in with relativity, and since relativity was well established, the aether was abandoned...If one re-examines the question in light of present-day knowledge, one finds that the aether is no longer ruled out by relativity,

I think that anyone who understands the material knows that neither SR nor MMX rules out an aether. They just render the aether unnecessary.

and good reasons can now be advanced for postulating an aether...We can now see that we may very well have an aether, subject to quantum mechanics and conforming to relativity, provided we are willing to consider the prefect vacuum as an idealized state, not attainable in practice. From the experimental point of view, there does not seem to be any objection to this...Thus with the new theory of electrodynamics we are rather forced to have an aether."

P.A.M. Dirac, Nature, 168, 906 (1951).

And what transformations for spacetime intervals arise from this "aether"?

See, this was exactly what I was complaining about in my first post when I said that no Aether proponent wants to provide any nuts and bolts to their preferred alternative theory. It's usually just a smokescreen using passages taken out of their context and with no mathematical detail.

What about gravity, all of the matter in the universe, and all of the energy in the universe? Substitute any (or all) of these for "ether" in the above quotation, and see for yourself how utterly misleading such statements are.

This doesn't make any sense to me. None of the terms you mention are used as the basis of competing theories against SR, but the aether is.

 

[quantumdude]

As to the rest of the "DeWitte" discussion: It's way off topic.

I have asked for something very specific in the title. Either you have information on it, or you don't. If you have it, then I'll thank you to post it. If you don't have it, then I'll thank you to make your posts elsewhere.

 

[Aether]

And what transformations for spacetime intervals arise from this "aether"?

See, this was exactly what I was complaining about in my first post when I said that no Aether proponent wants to provide any nuts and bolts to their preferred alternative theory. It's usually just a smokescreen using passages taken out of their context and with no mathematical detail.

I cited the references, and never said that this was my preferred alternative theory. Nevertheless, I agree whole-heartedly that a successful alternative theory should describe a more interesting space-time interval invariance. The transformations would be of the same general form as the Lorentz transformation, but the cosmological line element should exceed the F(L)RW in predictive power. For example, if it made "dark matter" and "dark energy" go away, that would be nice (for starters).

I don't feel guilty of launching "just a smokescreen using passages taken out of their context", but if you can show a better context for these passages then please do.

(as attributed to John Baez) The existing experiments put rather strong experimental constraints on any alternative theory. In particular, Zhang showed that these experimental limits essentially require that any theory based upon the existence of an ether be experimentally indistinguishable from SR, and have an ether frame which is unobservable (the only alternative is for a theory to "live in the error bars" of the experiments, which is quite difficult given the high accuracies achieved by many of these experiments).

This doesn't make any sense to me. None of the terms you mention are used as the basis of competing theories against SR, but the aether is.

Since gravity, all of the matter in the universe, and all of the energy in the universe, for example, "live in the error bars" of all SR experiments, then it is misleading to suggest that "the high accuracies achieved by many of these experiments" has somehow foreclosed on the possibility of ever detecting a locally preffered frame.