# Isotropic and anisotropic propagation of light

1. Feb 20, 2006

### bernhard.rothenstein

Do you aggree that there is an inertial reference frame in which light in free space propagates isotropically whereas in all other inertial reference frames its propagation is anisotropic?

2. Feb 20, 2006

### JesseM

Not if you use the Einstein clock synchronization convention when defining your coordinate system. Also, if you have two observers in windowless boxes which are both moving inertially at different velocities, then if each observer measures the velocity of light in the same way within their box, they will both get the same answer.

3. Feb 20, 2006

### pervect

Staff Emeritus
No, light propagates isotropially in all inertial frames. This is fundamental to relativity.

4. Feb 21, 2006

### Garth

The question is a little ill defined.

Does it not depend on how the light originated? i.e. The CMB was emitted by the Surface of Last Scattering (SLS). An observer co-moving with that SLS sees the CMB isotropically whereas all others, including ourselves moving relative to the SLS at about 0.1%c, sees a dipole anisotropy of 10-3.

Garth

5. Feb 21, 2006

### Jorrie

Observing the CMB as isotropic is not the same thing as observing light propagation to be isotropic. Observers moving relative to the SLS will observe anisotropy in the CMB, but they will still observe light propagation (i.e. speed) as isotropic.

6. Feb 21, 2006

### wisp

Yes, I fully agree with this.

Others that agree are:

1991 Roland DeWitte (Ether wind detected using an electrical one-way test).

1988, Gagnon, Torr, Kolen and Chang (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).

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.

Dayton Miller's ether drift experiments (similar to Michelson-Morley type experiments but more sensitive) A review of his work by James DeMeo shows indisputable evidence that data collected by Miller was affected by the sidereal period and this is clear proof of a cosmological ether drift effect.

It will be interesting to see if the newer more accurate clocks in space detect anisotropy in the one-way speed of light. My bet is they will.

7. Feb 21, 2006

### Garth

In which case I have read the question wrongly, I was confused as to this use of the word "isotropic" in regard to radiation.

I see what Bernhard means now and I have to say that I disagree with his statement.

Garth

8. Feb 21, 2006

### bernhard.rothenstein

9. Feb 21, 2006

### Garth

Okay, my slip of the tongue/finger, your question was, "Do you agree..." I was simply saying (IMHO) that I didn't.

Garth

Last edited: Feb 21, 2006
10. Feb 21, 2006

### clj4

This is the assumption of the test theories of Robertson-Mansouri and Sexl.
It has been disproved by experiment multiple times.

11. Feb 21, 2006

### clj4

The above is wrong and misleading. Given your views about relativity is within character. You have been told repeatedly (by several people) that:

1. One way light speed experiments have proven the isotropy
2. Quoting scandal writers like DeMeo is not proof, moreover Dayton Miller has been completely refuted by the modern reenactments of his experiment.
3. De Witte experiment is a hoax
4. Silvertooth experiment could not be duplicated by anybody (including himself)

12. Feb 24, 2006

Yes, I do, Bernhard. You are absolutely right!
One way light speed is relative. It is equal to c in the reference system K, that is at RELATIVE rest, and is different in different directions in the systems, which are moving RELATIVE to the system K.
Einstein absolutized the rest state of the own systems of the different observers. Einsteins observers have fear of moving. They think, as the people on Earth before Copernicus, that they can ONLY rest and NEVER move.
The people, who write that “One way light speed experiments have proven the isotropy”, do not read good books. Nobody never measured one way speed of light. Einstein understood it and wrote that it was impossible. But the people don’t read Einstein. They read only the interpreters of Einstein.
Einstein understood the problem with one way speed of light, but he did not understand that one way speed of light is relative. You do!
Do I right understand you?

13. Feb 24, 2006

### clj4

First off, you did not understand Bernhard's question so you twisted it into your own question, exactly as "wisp" tried it.

Secondly, contrary to what you think, one way speed of light has been measured repeatedly to be equal to c INDEPENDENT of the RELATIVE movement of the observer and the source. Just go take a class in relativity before posting all this nonsense.

http://math.ucr.edu/home/baez/physics/Relativity/SR/experiments.html#one-way tests

There are many more experiments like this.

Last edited: Feb 24, 2006
14. Feb 24, 2006

### ZapperZ

Staff Emeritus
I will caution you to re-read (since you are emphasizing about reading here) our Guidelines that you have explicitly agreed to. If you believe that there are evidence contrary to the standard interpretation of physics, then it is your burden to provide valid citations to reputable work.

Things have CHANGED since the last time you posted here.

Zz.

Last edited: Feb 24, 2006
15. Feb 25, 2006

### bernhard.rothenstein

I respect your point of view but i do not aggree with it

16. Apr 7, 2006

### wisp

I've just come across this paper (published yesterday) on another forum and I believe it answers Bernhard's question.

http://arxiv.org/PS_cache/astro-ph/pdf/0604/0604145.pdf [Broken]

It supports my view that there is a preferred reference frame and observers moving through this frame measure anisotropy in light's oneway speed.

Quoted from the paper: -
"The main objective of this paper is to present experimental results on an “one-way light path” laser diffraction experiment mounted in the shell of the TUPI muon telescope [7] and that shows clearly that the speed of light depends on the propagation direction."

also

"The analysis of The Global Positioning System (GPS) carried out by Hatch [10] provides also strong indirect evidence for the presence of an ether-drift velocity."

Last edited by a moderator: May 2, 2017
17. Apr 7, 2006

### clj4

While the link is certainly interesting, you forgot to mention that:

The Hatch paper was published in...Galilean Electrodynamics, a well known venue for crank publications. This in itself makes the paper you just quoted very questionable.

As to the link above, why don't you wait until there is :

1. independent experimental confirmation (this is the standard)

2. publication in a refereed journal?

As an aside, it looks as if the authors have "forgotten" that the speed of Earth exhibits a sine dependency. It may be very well that they are measuring this effect (remember the Dayton-Miller - Maurice Allais fiasco?) instead of measuring the one way light speed anisotropy. Contrary to what the authors show, the SRT prediction is not a horizontal line stuck on 0 but....a sine wave (because the Earth's speed is variable).
Give it a year or so, if the paper is still unpublished, then you have your answer.

Last edited by a moderator: May 2, 2017
18. Apr 14, 2006

### clj4

Last edited by a moderator: May 2, 2017
19. Apr 14, 2006

### Aether

I asked you here to show "Where exactly in the paper you cited do the author's claim that they are measuring the isotropy of the one-way speed of light as opposed to the isotropy of the two-way speed of light?", and you didn't respond. Now you're repeating this apparently false claim here, so I'll ask you again: Where exactly in these two papers you cited do the author's claim that they are measuring the isotropy of the one-way speed of light as opposed to the isotropy of the two-way speed of light?

This appears to be a proposal for a future experiment rather than a report on the results of an already completed experiment. I'll read the paper and comment further after you have answered my question.

Last edited by a moderator: May 2, 2017
20. Apr 14, 2006

### clj4

"Test of the isotropy of the speed of light using a continuously rotating optical resonator"

Last edited by a moderator: Apr 22, 2017
21. Apr 14, 2006

### clj4

Ah, you are again on your crusade on asking for "one way" tests. For that you need to read the other two Gagnon papers, Krisher (and accept it, otherwise there is nothing I can do for you) and, most importantly, C.M.Will (the same applies here).

As an aside, did you figure out how to measure (k'+k)L/2 from the "refurbished" Gagnon experiment? Because I have figured at least two ways. Are you familiar with lab equipment at all ? Or are you just a theorethician?

I get your angle, the new experiments I quoted "may" be two-way measurements, NEVERTHELESS the prove the ISOTROPY of light speed, and this is what counts. Now, the first paper in the list is clearly a one way, so you strike out here. The third paper, while it only "suggests" a means of executing one way light speed measurements looks awfully close in approach to the one way experiment of Gagnon.

I quoted the newest 3 papers to show that RMS (Robertson-Mansouri-Sexl) and SR are NOT equivalent. Actually the field has moved past RMS and into the SME (Standard Model Extension) by A. Kostelecky. Same deal here: "aether" theories can be "made" equivalent to SR provided that their parameters are driven to orders of 10^-15. (i.e ZERO)

You can go on forever denying the obvious and clinging to your "aether" beliefs and to some quotes from Zhang's book. Or you can start understanding test theories. The choice is yours.

Last edited by a moderator: Apr 22, 2017
22. Apr 14, 2006

### Aether

You said "Here are two new experiments on one way light speed isotropy:".

They are two-way tests, and they do tightly constrain the two-way light speed isotropy. It is the "one way" part you added-in that is wrong.

Then answer my question: Where exactly in the paper you cited do the author's claim that they are measuring the isotropy of the one-way speed of light as opposed to the isotropy of the two-way speed of light?

This quote from p. 811 of M-S III direclty applies to the experiments in the first two papers that you quoted (not that the authors claim anything contrary to this quote; rather, it is you who are putting words into the author's mouths to contradict this quote): "Another experiment similar to the Michelson-Morley experiment has been performed by Fox and Shamir [9]. According to these authors this experiment is able to decide between the special theory of relativity and an ether theory incorporating Lorentz contraction and time dilation. As we have shown quite generally in the first and second parts of this paper such a distinction is impossible in principle."

This quote from p. 523 of M-S II directly applies to the third paper (again, not that the authors claim anything contrary to this quote; rather, it is you who are putting words into the author's mouths to contradict this quote): "First-order tests cannot be used to distinguish between special relativity and ether theories, as has sometimes been stated. No such "experimentum crucis" is possible in principle, since the two classes of theories can be transformed into one another by a change of conventions about clock synchronization, as has been shown in I."

Where exactly in the three papers that you cited, all of which cite Mansouri-Sexl, do any of the author's claim that the quotes that I just gave from M-S are not valid?

Yes, it is a very exciting field.

Not exactly. They are empirically equivalent when the $$\alpha$$, $$\beta$$, and $$\delta$$ parameters are driven to the same values as in SR. However, no experiment can constrain the $$\epsilon$$ parameter, and that is the difference between one-way and two-way light speeds.

Last edited: Apr 14, 2006
23. Apr 14, 2006

### clj4

Do you have difficulties reading what I write? The first and third are clearly one-way.

"As we have shown quite generally in the first and second parts of this paper such a distinction is impossible in principle."

Ah, another quote that you take literally. The complete sentence is:
"As we have shown quite generally in the first and second parts of this paper such a distinction is impossible in principle within the framework of our kinematic theory." The moment you step out of the MS theory and into electrodynamics, as C.M.Will and Gagnon clealy show, the situation is reversed, they can tell the difference. Why do you think that all the experiments are electrodynamic? Gagnon and its derivatives should be stuck on your desk, in front of your eyes.

Says who? You? Are you trying to say that the MS and SR are still equivalent when $$\alpha=\beta=\delta=0$$ and $$\epsilon$$ is left unconstrained?

Besides, you seem to insist in missing the main point (this is why you keep fighting Krisher): what happens when
$$\alpha=\beta=\delta$$ are NOT 0? Obviously the two theories ARE NOT equivalent.

The C.M.Will paper is quite clear on the subject.
BTW: you haven't answered my question on the "refurbished" Gagnon. This one is clearly a thorn in your argumentation.

Last edited: Apr 14, 2006
24. Apr 14, 2006

### Aether

The third one seems to be, but the experiment hasn't been carried out yet and I haven't read the paper very closely. Please answer my question with respect to the first two: Where exactly in these two papers you cited do the author's claim that they are measuring the isotropy of the one-way speed of light as opposed to the isotropy of the two-way speed of light?

I have made a correction to that statement. MS and SR are equivalent when $$\alpha$$, $$\beta$$, and $$\delta$$ are the same as in SR and $$\epsilon$$ is left unconstrained.

You mean, what happens when any experiment shows that they are not the same as in SR?

Last edited: Apr 14, 2006
25. Apr 14, 2006