Is Einstein's etheric model of GR compatible with modern physics?

[turbo]

As an optician, I am uncomfortable with the concept that photons sail through space on geodesics defined by the masses embedded therein. What is the problem with simple refraction, as explained by classical optics? As it turns out, there is absolutely no problem, according to Einstein. In his 1920 book "Relativity - The Special and General Theory" he claimed that gravitational lensing is due to the variable speed of the propagation of light through space. In other words, c must be variable based on location, else "gravitational" lensing cannot occur. The concept of an invariable speed of light in a vacuum is applicable only to the idealized case of Special Relativity.

In the second place our result shows that, according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity and to which we have already frequently referred, cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity of propagation of light varies with position. Now we might think that as a consequence of this, the special theory of relativity and with it the whole theory of relativity would be laid in the dust. But in reality this is not the case. We can only conclude that the special theory of relativity cannot claim an unlimited domain of validity; its result hold only so long as we are able to disregard the influences of gravitational fields on the phenomena (e.g. of light).

http://www.bartleby.com/173/

This variable c concept is foreign to many people who have not read and reviewed Einstein's later works, but does it have parallels in modern research? Here is a prime example: Fotini Markopoulou-Kalamara of the Perimeter Institute has postulated that GLAST might demonstrate the fine-scale structure of space, by observing wavelength-dependent time delays in the arrival of EM. She believes that higher-energy EM will interact more frequently with the space through which it propagates, and therefore be delayed, compared to low-energy EM. I happen to share her view and eagerly await the science from this instrument. If Einstein were alive and active today, he would be working at Perimeter. They've got his back.

Well, GLAST has not yet launched. Is there presently any experimental data to support the concept that the speed of light in a vacuum may be variable and perhaps even frequency-dependent as our PI researcher proposes? As published in August of this year, the MAGIC consortium has observed an apparent delay of 4 minutes in the arrival time of very high energy gamma rays in a burst from LS I +61 303. The object is at redshift z = 0.034 meaning light travel time of 0.46 billion years and there was a delay of 4 minutes in the high-energy EM arrival time. That's a very tiny delay in a very long column of propagation, but what if it is real and repeatable?
http://arxiv.org/abs/0708.2889

There may well be a mundane explanation for the observed delay, including unmodeled frequency-dependent evolution of the GRB. If, however, this observation is duplicated with MAGIC or with other instruments, AND (critically!) if the delay is shown to be proportional to the redshift of the source, then it is time to consider that Zwickey's "tired light" concept has legs. This has global implications for cosmology.

I will not elaborate further at this time, except to refer interested readers to Einstein's Leyden address of 1920 and to his essay "On the Ether" of 1924. "On the Ether" is chapter 1 of Saunders and Brown's book "The Philosopy of Vacuum". Einstein believed that space is a local and dynamic player in the emergence of gravitational and inertial effects, and that embedded matter conditions the qualities of space to give rise to the effects we observe regarding the propagation of electromagnetic waves.

 

[ZapperZ]

You applied several different and unrelated things inconsistently here and lump them all together as if they all point to what you "believe" in.

1. "What is the problem with simple refraction, as explained by classical optics?"

If you had bothered to read the FAQ, you'd have noticed that even in a "simple refraction", it doesn't mean that the photons aren't moving at c. We know enough on optical transport in dispersive media that we actually USE this knowledge to study the material, such as the phonon structure. Furthermore, even in classical optics, there is such a thing as the group velocity, which is ultimately what instruments measure in the majority of the cases. This has nothing to do with the speed of light, even in dispersive medium.

2. "Here is a prime example: Fotini Markopoulou-Kalamara of the Perimeter Institute has postulated that GLAST might demonstrate the fine-scale structure of space, by observing wavelength-dependent time delays in the arrival of EM. She believes that higher-energy EM will interact more frequently with the space through which it propagates, and therefore be delayed, compared to low-energy EM."

You were using this right after your quote of Einstein. Yet, if you read carefully, this has nothing to do with gravitational lensing. It has more to do with the nature of space. Some even argue that this is more of a "quantum foam" effect. No lensing here, and nothing to do with gravity. Yet, you managed to lump them together as if this somehow give some validation to what you quoted Einstein to have said. They are not compatible and are addressing different issues.

3. "As published in August of this year, the MAGIC consortium has observed an apparent delay of 4 minutes in the arrival time of very high energy gamma rays in a burst from LS I +61 303. The object is at redshift z = 0.034 meaning light travel time of 0.46 billion years and there was a delay of 4 minutes in the high-energy EM arrival time. That's a very tiny delay in a very long column of propagation, but what if it is real and repeatable?"

You should be completely aware that the CALIBRATION of this experiment RELIED on several astronomical observations and implicitly assumed standard astrophysical technique. This is where "God is in the Details"! Read the methodology and figure out what implicit assumption they made regarding their calibration. I would also suggest that you hold off on jumping all over this until (a) this is verified further and (b) that what you claim is the ONLY possible interpretation. I've heard of at least a couple of other possible explanations being offered for such an observation. Furthermore, do you see any of the authors in this paper claiming anything similar to what you had in mind? I don't think so. Not only that, this STILL has nothing to do with your "ether" or anything that Einstein mentioned in your quote. Again, you've put two different things that don't have anything to do with each other.

Zz.

 

[turbo]

Let's take this in pieces. Is the speed of light in a vacuum constant or not? If not, why not?

 

[cesiumfrog]

Yes, the speed of light is locally constant in vacuum, everywhere and always. Nonetheless, on a large scale it may not seem constant in vacuum (when you pretend to treat space-time as flat, especially near a large mass, as in Einstein's example).

--
And now skipping on to other issues... real-life "interstellar space" nor lens media are not vacuum (even the quantum vacuum looks different from the classical vacuum), and so in both cases there may be many small interactions which make it seem, on average, as though the light had a different speed.

 

[ZapperZ]

Let's take this in pieces. Is the speed of light in a vacuum constant or not? If not, why not?

From all that we know, YES, it is a constant.

Zz.

 

[Chris Hillman]

I refuse to be dragged into a discussion of what I regard as fringe physics of little apparent value, but for the record, I do not think that it is historically accurate to speak of "the" [sic] "Einstein aether model of gtr" [sic], and I feel that everything I have seen turbo-1 say on this subject is misleading or even incorrect. I believe it would be fair to characterize his views as idiosyncratic. I see that by failing to clarify the theory-dependence of his assertions, turbo-1 has already caused confusion about what theories he wishes to discuss. (Ditto cesium on what gtr says, which is unambiguous, about speed of EM and gravitational radiation in a vacuum region.) This doesn't bode well for the future of this thread.

For the record, in another recent thread I offered to discuss with turbo-1 a quite different issue, namely how to balance competing desiderata in teaching gtr to physics students, particularly in a first course:

• There is an undeniable human and intrinsic interest in gaining a historical perspective, in particular an in-depth knowledge of the many twists and turns in Einstein's thinking about gravitation, including his work after his heroic struggle towards gtr (mostly c. 1912-1915). But teaching the neccesary historical/philosophical context requires much time and effort, and basically involves getting into the poor student's skull dozens of confusions which plagued the gtr literature before the advent of the Golden Age of Relativity (c. 1960-1975).
• OTH, it is necessary for serious students to master the modern tools which are standard in contemporary gravitation physics; in particular, in the context of gtr, which was completely transformed during the Golden Age with the introduction of
  • such essential mathematical techniques as invariant descriptions of congruences and Carter-Penrose diagrams illustrating conformal structure,
  • correct understanding of the role played by curvature in gtr and of the geometric nature of gravitational radiation,
  • mainstream acceptance of the existence of collapsed objects such as neutron stars and black holes in Nature, plus mainstream acceptance of the now standard hot Big Bang theory of cosmology,
  • etc.
  Mastering the mathematical machinery, including computational skills as well as overcoming numerous common misconceptions, requires much time and effort, leaving very little time for historical background.

To me it seems obvious that while the first is desirable, the second is critically important for future researchers in astrophysics, and thus opting for the second option is, it seems to me, an example of a classic "no-brainer". Even more ironic: it seems perfectly obvious to me (and, I warrant, to anyone else familiar with the modern machinery) that learning the modern way of understanding gtr is also a prerequisite for those historians and philosophers who wish to understand the issues which dominated the early gravitation physics literature. Unfortunately, it is apparent that thus far very few have done so.

Unfortunately, turbo appears to have badly misunderstood what I offered to discuss (or thought I offered to discuss) in the other thread.

If anyone wants to discuss the pedagogical issue of balancing historical perspective versus mastering modern methods of "geometric analysis", I suggest starting a new thread. See [thread=200359]this thread[/thread] for a recent discussion closely related to the one which I suggested to turbo-1(in yet another recent thread). However, this might be moot since I think I just expressed the main point I had in mind.

 

[turbo]

Chris, you invited me to start this thread.
https://www.physicsforums.com/showpost.php?p=1515568&postcount=40

Now, if you refuse to be "dragged into a discussion" that you invited me to start, I have to ask if you why. Did you not want to discuss my opinions in a thread in which they might have been relevant? Did you want me to start a new thread that might have been gang-teamed and killed a-borning? If not, why did you ask me to start a new thread?

 

[Chris Hillman]

Please re-read my "invitation":

I sense that you may have more to say about why you think that understanding the history of physics is important or even essential for understanding modern physics. If so, I request that you start a new thread on that topic, and I will try to drop into explain my more or less opposing view (unless of course your essay is so convincing that I decide to agree with you!).

I refuse to be dragged into an argument over whether or not I have, as you seem to think, reneged on my offer--- which I deny, in fact I just explained my view above. This post ends my contributions to this thread.