Talk:Woldemar Voigt

Single source problem

This page contains a number of errors, as it heavily leans on a paper by Ernst and Hsu which is easily shown to be misguided. However, I don't know another paper that correctly summarizes Voigt's undertaking and if there isn't another one, I guess we'll just have to wait for someone to do the effort, while some additional facts may be added to compensate a little. It would be helpful if another peer reviewed paper is known that discusses Voigts work on "Doppler" in detail. Harald88 12:02, 6 January 2006 (UTC)

Harald, why don't you easily show Ernst and Hsu to be misguided and publish your argument. At the moment we have a refereed paper (Ernst and Hsu) and your assertion, so at the moment it is no contest, as you realise. It is easy to critize and ask others to prove you are right, but is it going to happen? Have you checked if someone else has already refuted the "easily shown to be misguided" paper? E4mmacro 13:40, 7 January 2006 (UTC)

Harald, I wrote the article page and I wasn't aware that I relied heavily on Ernst and Hsu. I mentioned them because they give an English translation, but I see that I did take the following from them "he stated the universal speed of light and demonstrated that Maxwell's equations are invariant under his transformation". I checked (perhaps my check was wrong), that the speed of light was preserved. I first saw Voigt's paper probably 23 years ago in German, probably didn't understand it. I worked from the transformation itself, those few lines in the article page, and if I erred it was in accepting Lorentz's opinion that the transformation could have been important in special relativity if it had been known earlier. Didn't Lorentz mean by this that they preserved Maxwell's equations, something I haven't checked? At the time I wasn't aware of your contrary opinion that the transformation has nothing useful to say about relativity (if I have understood you correctly). Even if I had known of your opinion, it would have been your opinion versus Lorentz and also Ernst and Hsu, hardly enough to stop me writing something I thought interesting. I treated it as just another form of the Lorentz transformation. If, as you say elsewhere, it is only about acoustics, then it is even more interesting that Lorentz said what he said about it. Maybe the LT is not as mysterious as is sometimes thought, no more mysterious than acoustics. I wonder what Lorentz was getting at? E4mmacro 13:40, 7 January 2006 (UTC)

Hi E4mmacro, Maybe I should write a critical note about that paper but then, there are dozens of such papers that I know of, all poorly researched. I don't want to waste my time on such matters.

Voigt treated light and sound on the same basis, and provided preliminary solutions for both, using his transformation as an intermediate calculation tool. In essence, he obtained that wave velocity is not independent of the source velocity, but just as Lorentz he neglected such second order effects. As such, reporting the claim that "he stated the universal speed of light" can be immediately debunked for intelligent readers by the factual statement that his calculations were for waves in general, including sound.

I'm afraid that Lorentz didn't think much farther than Ernst and Hsu: he used it as a mathematical tool, without carefully analysing what he exactly calculated, even not grasping the essence of what Poincare talked about, until he finally understood it from Einstein. But we shouldn't be hard on him, as he achieved a whole lot and while he was developing his theories, Poincare and Einstein pondered about the consequences. Harald88 14:49, 7 January 2006 (UTC)

E4mmacro 22:13, 7 January 2006 (UTC) Hi Harald, I think we are getting somewhere. I think the point for me and Lorentz is this. If when we moved through air, our clocks ran slow by the factor $\gamma ^{-2}$, and our rulers expanded in the direction transverse to the motion by the factor $\gamma ^{-1}$ and were unchanged in the direction of motion, and if our clcoks were syhchronized by the exchanging sound waves assumed to travel with the same speed in the out and back directions, (and if air were an inviscid fluid, there were no boundary layers and separation and hence no aerodynamic drag and lots of other things) then everything would be consistent, the Voigt transformation would hold, and we couldn't detect motion thru air by accoustic experiments. But let's not talk about air and accoustics too seriously. What Lorentz meant, I think, is that, if, when we moved through the ether, the clock rates and ruler dimensions changed as above, and we used the time transformation of Voigt (established simultaneity by Poincare/Einstein light exchanging procedure) then Lorentz (and I) thought that everything would be pretty much the same as in SR, except of course now experiment would show the time diltaion in the Voigt transformation to be wrong. In other words it is an argument about what transformations could hold for light, and at the time (1909) when Lorentz said what he said, there was no experiment to decide one way or the other. You could say it is now useless speculation, but I think the following point is worth thinking about:

What puzzled me a bit about Ernst and Hsu, if they are correct about Maxwell's equations being invariant under Voigt transformations, is why Larmor and Einstein, when finding the transformation that made Maxwell's equation invariant, did not hit upon Voigt's version, if what Ernst and Hsu said about invariance were true (can you forget about their other statements and accoustic etc and verify or refute this purely mathematical argument by doing the maths, I have only checked quickly that the speed of light is isotropic under the transformation and your maths would be better than mine).

I happen to know a practical answer to that question: As measurement of the lateral coordinates cannot be affected by speed, their transformation must be unity; otherwise the POR could be broken for a bullet that one shoots through a hole. But I now see below that you also discovered that, thus I didn't understand the question. For the speed of light to be constant, any transformation of that kind would do; that was also known at the time. Harald88 04:18, 8 January 2006 (UTC)

Lorentz in 1899 had his transformation with the RHS as now multiplied by an undetermined factor, say $\ell$, and I think he was open to the possibility that $\ell$ might be a function of velocity. If $\ell =\gamma$ then Lorentz would have had Voigt's transformation. Lorentz apparently spent from 1899 to 1904 before deciding that $\ell =1$. I think he had a proof, but I can't remember what it was. You will notice on the time dilation page there is the familar derivation/demonstration of time dilation by bouncing light transversely between two mirrors. This implicitly assumes that length transversely is unchanged, something required by the principle of relativity I guess since it would be detectable, at first glance, if it happened. Anyway, assuming transverse length is unchanged, you get time dilation of the Lorentz factor, not the "Voigt" factor (I use the terms "Voigt" tranformation or factor without saying anything about Voigt's opinions or ideas or motives)). So I certainly wonder now, if Maxwell's equations can be invariant under a transformation which does not satisfy the principle of relativity. E4mmacro 22:13, 7 January 2006 (UTC)

I had not thought about it but I suppose that you already gave the answer here above, from alone those equations apparently the factor $\ell$ is undetermined (if wrong, please someone else correct this!). Harald88 04:18, 8 January 2006 (UTC)

I would like to suggest that for the convenience of Wikipedia readers the following references should be added: A.G. Gluckman, "Voigt Kinematics and Electrodynamic Consequences", Found. Phys. 6, 305 - 316 (1976); Alfred O'Rahilly, "Electromagnetic Theory" (Dover, 1965), Vol. I, Chap. IX; Oleg D. Jefimenko, "Electromagnetic Retardation and Theory of Relativity" (Electret Scientific Company, Star City, 1997). Referring to the paper by Ernst and Hsu, yesterday I sent a letter to Prof. Hsu, pointing out that I don't agree with his interpretation. In my opinion, Voigt's eq.(2) is the general form of the Galilei transformation, which accounts for both a constant time delay and a rotation of coordinate axes (compare the Wikipedia article on the Galilei transformation, please). Since the Voigt transformation is said to be equivalent to the Lorentz transformation, there should therefore be no basic contradiction between the Galilei transformation and the Lorentz transformation. 62.245.207.10 14:14, 23 March 2006 (UTC)KraMuc 10:14, 15 April 2006 (UTC)

I had sent a copy of my letter (to Prof. Hsu) to Andreas Ernst, Heidelberg, Germany. I received today a written reply from Mr. Ernst, in which he confirms that my interpretation of Voigt's equation (2) is correct (which implies that the interpretation in the paper by Ernst and Hsu is incorrect): Voigt employed the general version of the Galilei transformation, which accounts also for rotations and for a constant time delay. The general Galilei transformation used by Voigt is the equation (1) on p. 73 of the following recent review article: C. Lämmerzahl, "Special Relativity and Lorentz Invariance", Ann. Physik 14, No. 1 - 3, pp. 71 - 102 (2005). Physicists should read articles and comments on the Voigt transformation with some caution, especially if they are written by mathematicians. An example of a well written (anonymous) comment on the Voigt transformation, in which the Galilei transformation used by Voigt is not interpreted correctly, may be found in the Internet in the "MathPages" ("Reflections on Relativity", Sec. 1.4: "The Relativity of Light"). I like the "MathPages", however, and I recommend to male physicists, who are not yet married, to read in the Chapter "Probability & Statistics" the instruction "Optimizing Your Wife". Let me come back to Woldemar Voigt and be serious again. In the literature sometimes the impression is given that Voigt's work of 1887 on the Doppler effect had been forgotten around the turn to the 20th century. As a matter of fact, this conjecture is highly unlikely: I found Voigts paper cited on the front page of an article on the Doppler effect by E. Kohl, Ann. Physik 11, 96 (1903). His article is cited there together with articles on the Doppler effect by Mach and Michelson. 84.154.86.135 18:59, 24 March 2006 (UTC) KraMuc 18:00, 14 April 2006 (UTC)

What was known about Voigt

In his interesting article "Henri Poincaré: a decisive contribution to relativity" (available in the Internet), C. Marchal states on p. 5: "In 1895 Lorentz noticed that the first-order of Voigt transformation preserves the first-order of Maxwell's equations. Larmor gave the second order a little later". However, no reference is given, so that it is not clear to me whether a) Lorentz actually has cited Voigt in some publication, b) this information may be found in the correspondence of Lorentz with other physicists, such as Poincaré, or whether c) this is the author's personal interpretation. 84.154.76.78 16:51, 26 March 2006 (UTC)KraMucKraMuc 10:26, 15 April 2006 (UTC)

We have Lorentz's testimony that he (Lorentz) did not know of Voigt's paper until 1906-1909, see the footnote in the article, so I guess (c) is the your answer. Lorentz 1895 in a book "Versuch ..." had first order Lorentz transformations. You can find some info on Larmor in the article cited in the footnotes (Brit J Phil Sci)E4mmacro 20:12, 26 March 2006 (UTC)

From the paper by Ernst and Hsu and from the Internet article "A Brief History of Special Relativity" by O'Connor and Robertson it is known that Lorentz had corresponded in 1887 and 1888 with Voigt on the Michelson-Morley experiment of 1886. In the year of 1887 Voigt had published in the Göttinger Nachrichten not only his famous paper on the Doppler effect, Göttinger Nachr. No. 2 of 10 March 1887, p. 41 ff. (originally presented at the session on 8 January 1887) but also a second paper entitled "Theorie des Lichts für bewegte Medien" ("Theory of light for moving media"), Göttinger Nachr. No. 8 of 11 Mai 1887, pp. 177 - 238 (originally presented at the session of 10 July 1886), where he discussed both the Michelson-Morley experiment of 1886 and the Michelson experiment of 1881. When Ernst and Hsu wrote their paper, they had been unaware of the existence of Voigt's second article of 1887. At the end of the latter article (p. 233 ff.) Voigt had arrived at the conclusion that the Michelson experiment, in the way in which it had been carried out, must necessarily give a null result, independently of whether the light aether is at rest or moves. Lorentz had not been cited in Voigt's lengthy second paper, although Lorentz had worked on the same subject and published a similar review article (in French) of about the same length in 1886. Apart from his well known apology to Voigt, published as a footnote in his book on electron theory (1909), Lorentz stressed the priority of Voigt also in Chapter 3, p. 52, of his book Die Relativitätstheorie für gleichförmige Bewegungen (1910-1912), Vorlesungen über Theortetische Physik an der Universität Leiden", Band IV, Leipzig 1929.KraMuc 15:16, 7 April 2006 (UTC)KraMuc 13:44, 13 April 2006 (UTC)

That's interesting! Could you send me a copy of that article, or at least provide a reference? Harald88 16:12, 8 April 2006

Sorry, but I thought that we were discussing Voigt. I have some of those papers by Lorentz, but I'm interested in that less known paper by Voigt. That reference should next also be added to the article. Harald88 20:18, 10 April 2006 (UTC)

The less well known paper by Voigt is the second one mentioned in my message of 7 April 2006. All details of the reference had been stated there. The article may be ordered from Göttinger Digitalisierungszentrum (GDZ), Göttingen State and University Library, 37070-Göttingen, Germany; e-mail address: gdz@www.sub.uni-goettingen.de. Publications by Lorentz on the same subject in the year 1886 and before might be of historical interest in this context, since Lorentz had not been cited in Voigt's second article. Lorentz's "testamony" (compare footnote # 4 and the message of 26 March 2006 by E4mmacro) obviously implies that also all of his research students as well as his closer scientific friends (and their research students too), such as Henri Poincaré (who spoke German as Lorentz did), had over decades continuously "overlooked" Voigt's work on the Doppler effect as well as all papers on the Doppler effect, in which Voigt's article of 1887 had been cited, such as the article by E. Kohl in Annalen der Physik of 1903. It can perhaps not be excluded that C. Marchal's view is more realistic.KraMuc 14:28, 13 April 2006 (UTC)84.153.99.195 16:46, 18 April 2006 (UTC)