Talk:Special relativity/Archive 18

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Archive 17 Archive 18 Archive 19

Postulates revisited

Although Einstein derived his theory from 2 axioms mentioned in this article, it has been shown later that in fact only first of them is necessary. That is, special relativity can be derived only from Galileo's indistinguishability of reference frames and uniformity/isotropy of space. It can be shown then that transformation law between moving reference frames must have Lorentz form, with c being an arbitrary parameter characterizing our timespace (possibly c=∞). It is then a matter of experiment to determine the exact value of this parameter, and it turns out that it coincides with the speed of light.

I believe this purely-mechanical derivation of special relativity should be mentioned somewhere. Firstly because it is rarely taught, and thus most students never learn this fact; secondly because it implies that relativity could have in principle be discovered even in Newtonian times. —Preceding unsigned comment added by 128.12.157.38 (talk) 10:10, 12 September 2007 (UTC)

No, not Newtonian times, Maxwellian times. SR requires Maxwell's equations to be invariant under a shift of inertial frames. That was how Einstein derived SR. After he had derived SR (by his own account) he realised that the constancy of the speed of light was sufficient and that the rest of Maxwell's equations were superfluous to his purposes.--Michael C. Price talk 03:44, 16 February 2008 (UTC)
See section Alternate Derivations of Special Relativity in article Postulates of special relativity and section From group postulates in article Lorentz transformation. DVdm 10:21, 12 September 2007 (UTC)
This issue has been discussed before repeatedly. You are wrong. The second postulate is necessary. c could also be imaginary, i.e. spacetime could be Euclidean (time being a space dimension) if one drops the second postulate. JRSpriggs 00:41, 13 September 2007 (UTC)
The assumption is not one of the isotropy of space, but rather of the isotropy of spacetime! If one assumes the isotropy of space and the universal uniformity of time (as Newton did), then you end up with Newton's Laws uniquely. The assumption that you are making, that space and time co-exist as part of a Lorentzian manifold, is peculiar to relativity, and ends up being a different (and less specific) form of the second postulate.
As JRSpriggs noted, we have been through this silliness before. I hope that this satisfies you that the so-called one-postulate approaches really hide instead of eliminating the second postulate. --EMS | Talk 20:02, 5 October 2007 (UTC)
JRSpriggs and yourself are completely wrong. SR can be derived from the 1st postulate alone, since Maxwell's equations imply a fixed value for the speed of light. Arguments that c could have been imaginary and space Euclidean is complete bonkers, since c is set by Maxwell's equations. And BTW the idea that there is a "modern" form of Maxwell's equations (as the latest revisions imply) is erroneous. There is just Maxwell's equations, period, as laid down by Maxwell, and compacted by Heaviside, a long time before Einstein arrived on the scene. --Michael C. Price talk 03:37, 16 February 2008 (UTC)
To Michael C. Price: Notwithstanding that Maxwell's equations are consistent with SR, Maxwell's equations are a separate theory from SR. You should not just arbitrarily import them into it and use them instead of the second postulate. Although historically Maxwell's equations came before SR, SR (as a second-order theory) is logically prior to them. JRSpriggs (talk) 07:59, 16 February 2008 (UTC)
Your last sentence is gibberish to me. But it is irrelevant to the history of the development of SR. Einstein developed SR by studying Maxwell's equations. The idea that we should magically pluck the constancy and real value of the speed of light from nowhere to "explain" SR is unphysical and ahistorical -- and unpedagogical. I do not think explaining this POV (the truth, BTW) should be met with the response "You are wrong. "--Michael C. Price talk 09:36, 16 February 2008 (UTC)

I think we should have a small discussion section about this issue in the article, because different physicists have different opinions on this matter. Clearly, before Relativity, Maxwell's equations were assumed to be valid only in the rest frame of the "aether". But if one assumes the validity of Maxwell's equations in any inertial frame then that implies special relativity and vice versa. You can take Coulomb's law for electrostatics and assume the validity of Special Relativity and derive Maxwell's equations from that.

Another issue that is not explained well in this article is that Lorentz invariance is more fundamental than Maxwell's equations for electromagnetism. This is an artifact of deriving relativity from the two postulates. Hypothetically, suppose that the photon has a tiny mass, so that electromagnetism is described by Proca's equations instead of Maxwell equations. This, of course, would not affect Special Relativity at all! Count Iblis (talk) 13:32, 16 February 2008 (UTC)

I agree. Yes, the article should explain both POVs. And yes, if the photon had a mass that would not matter, since the Proca equations are also Lorentz invariant.--Michael C. Price talk 16:00, 16 February 2008 (UTC)

Improving this Article

It is difficult to improve on such a knowledgeable and well-written article. In the interests of journalistic fairness and balance, I only add a section on Criticisms of Special Relativity by qualified scientists. I hope other editors will respect my viewpoint as I respect yours. —Preceding unsigned comment added by RAmesbury (talkcontribs) 14:36, 10 December 2007 (UTC)

Your viewpoint of the STR is irrelevant as is a section on criticism (there is a separate article for that). The fact that you have added the same material to four different articles on relativity reveals your true intention of using Wikipedia as a soapbox. You are transparent. Alfred Centauri (talk) 21:48, 10 December 2007 (UTC)
Out of curiosity, which is the "separate article for" criticism of relativity? Perhaps we should have a link to it here. That said, I do not think that the "criticism" added by RAmesbury is proper even for such an article. It is just a statement of hostility and suspicion of relativity without any attempt at rational argument. JRSpriggs (talk) 03:32, 11 December 2007 (UTC)
Ooops, apparently I'm becoming senile. It's not a separate article but is instead a section of a separate article History_of_special_relativity#Criticisms_of_special_relativity —Preceding unsigned comment added by Alfred Centauri (talkcontribs) 03:54, 11 December 2007 (UTC)
Section to which, by the way, he already tried to add his message on 24-Sep. Check his early history. This clearly is a special purpose anti-relativity soapbox sockpuppet account. His other edits clearly are decoys for his main activity. I think we can expect attempts to restore his message by other sock- and meatpuppets, and, of course, admin counter-intervention requests. DVdm (talk) 12:07, 11 December 2007 (UTC)

Besides the information collected by RAmesbury I think the time formula in STR is not correct. The correct time formulas are [1] and [2]. Please let me know if you can prove that the formula [1] or [2] is wrong. Thanks. Here are the formulas:

The correct time formula should be:

Ta' = Ta + (ao/C) ----- [1]

Ta represents the time of an event started at point a and Ta' stands for the time recorded by the camcorder at point o for the same event started at point a. ao stands for the distance from point a to point o and C represents the speed of light.


The proof for formula [1] is very simple. Since the 'picture of the event-starting' takes time to travel from point a to point o, when the camcorder recorded that 'picture of event-starting' the time should be (ao/C) after the actual starting time. Ta' = Ta + (ao/C).


The time formula for a period of time should be:

Tab' = Tab + ((bo-ao)/C) ----- [2]

Tab represents the time period of the event started at point a and ended at point b and Tab' is the time period recorded by a camcorder at point o for the same event. John C. Huang (talk) 06:20, 4 January 2008 (UTC)

Please read the welcome and warning comments on your talk page. Thanks, DVdm (talk) 09:11, 4 January 2008 (UTC)

Based on FACT, for an event started Ta at point a and ended Tb at point b, the time period Tab = Tb-Ta is recorded as Tab' = Tab+((bo-ao)/C) by a camcorder at point o. When a person walks at a constant speed 0<V<C away from the camcorder, bo-ao = ba, so that the recorded time period is larger than the actual time period, time formula in this case is T' = ((C+V)/C)T. When V is approaching the answer of (V^3)+2C(V^2)-2(C^3) = 0 then T' = ((C+V)/C)T will be approaching the time formula in STR. That particular V is about 0.85C. I think the time formula in STR is just a special case of the correct time formula. John C. Huang (talk) 04:54, 12 January 2008 (UTC)

Time Formula in STR

Based on FACT, for an event started Ta at point a and ended Tb at point b, the time period Tab = Tb-Ta is recorded as Tab' = Tab+((bo-ao)/C) by a camcorder at point o. When a person walks at a constant speed 0<V<C away from the camcorder, bo-ao = ba, so that the recorded time period is larger than the actual time period, time formula in this case is T' = ((C+V)/C)T. When V is approaching the answer of (V^3)+2C(V^2)-2(C^3) = 0 then T' = ((C+V)/C)T will be approaching the time formula in STR. That particular V is about 0.85C. I think the time formula in STR is just a special case of the correct time formula. John C. Huang (talk) 04:54, 12 January 2008 (UTC)

John C. Huang (talk) 20:15, 16 February 2008 (UTC)

Small discussion of classical limit c ---> infinity after mentioning postulates could be helpful

I don't have the time to do that myself today. The first postulate alone would be consistent with classical mechanics, if c were infinite. Of course, an infinite speed in classical mechanics is invariant for all inertial observers too :). We should make these comments and mention that the limit c --> infinity is the classical limit. We should also point out that changing the value of c amounts to changing the units we use for measuring time or distances, so that it is not unphysical. So, the limit c ---> infinity can be interpreted as just an infinite rescaling of space relative to time. In this asymmetric scaling limit the relativistic universe becomes classical. Count Iblis (talk) 13:38, 18 February 2008 (UTC)

Second postulate following from first

Sorry, accidentally cut off my own edit summary just now. What I meant to say was that if it was just about a misreading of the German, then it was a misreading that the German Wikipedia has also made. ("Da die Gesetze der Elektrodynamik in jedem Bezugssystem gleichermaßen unverändert gelten, gilt insbesondere auch ihre Vorhersage für eine konstante Vakuum-Lichtgeschwindigkeit in jedem Bezugssystem.") The important thing in the intro isn't exactly how Einstein presented the postulates in his first paper on it, but how we now understand special relativity. — Laura Scudder 18:16, 18 February 2008 (UTC)

It is not a matter of misreading of German, it is a matter of seeing the wider historical context and understanding how that helps many people to understand the subject. IOW understanding the origins of SR from MEs is helpful as well as being historically correct. Those that don't understand the past are condemned to repeat it. --Michael C. Price talk 09:47, 19 February 2008 (UTC)
I'm not saying that we shouldn't discuss how it was historically understood and developed, just that in the very first paragraph the most important thing is the current understanding. That's why I'd support stating that the constancy of the speed of light follows from the first postulate in the intro. — Laura Scudder 00:53, 21 February 2008 (UTC)
Thanks. I agree the current understanding is important, as well as the historical origins -- but then there's never been a conflict between them. We were taught at school how to derive c from Maxwell equations, and at college how to derive SR from Maxwell. Anyone who thinks they understand SR without understanding that is deluded. It's like trying to understand QM without the deBroglie hypothesis.--Michael C. Price talk 03:43, 21 February 2008 (UTC)

Article about postulates

There is already a separate article Postulates of special relativity. Would it not be more appropriate for a lot of the discussion under postulates in this article (including any mention of possible redundancy, and historical details) to be moved to the other article and a much simplified summary be written for this article? Then add {{main|Postulates of special relativity}} to this article's postulates section. --Dr Greg (talk) 18:14, 20 February 2008 (UTC)

Capital suggestion. A summary is all that is needed. I suggest:
Some people (including Einstein at times[1]) believe that the second postulate is redundant because it follows from the first postulate applied to Maxwell's equations; other people (again including Einstein at times[2]) prefer to start by postulating Lorentz invariance or constant lightspeed.
to replace the long-winded polemic that exists at the moment.--Michael C. Price talk 23:57, 20 February 2008 (UTC)

Possibly the existing article devoted to the Postulates (or better yet, an article on the axiomatic basis of special relativity) would be a better place for much of the discussion presently contains in the Postulates section of this article. However, much of this discussion has simply been driven by attempts to prevent erroneous POV from over-running the article. The main problem seems to be one of reading comprehension. Einstein wrote the following words

"The principle of the constancy of the velocity of light used there [i.e., in his derivation of special relativity] is of course contained in Maxwell's equations."

Now, some editors wish to paraphrase this by saying "Einstein dropped the second postulate" in this paper. Needless to say (or so one would have thought), the above quote from Einstein says exactly the opposite of this paraphrase. The quote says that by assuming the validity of Maxwell's equations he is NOT dropping the lightspeed postulate, because the principle of invariant light speed is contained in Maxwell's equations. Hence he is not dropping anything, he is adding all the rest of the content of Maxwell's equations, and by the way, he is doing this (in contrast to the prior paper in which he derives the Lorentz transformation) in order to present a heuristic argument for mass-energy equivalence, and he apologized for stooping to assume Maxwell's equations considering that it was already clear they were invalid. Anyway, his statement says that he is NOT dropping the lightspeed principle. I object to paraphrasing this by saying he WAS dropping the lightspeed principle.Denveron (talk) 23:22, 20 February 2008 (UTC)

Despite the fact that no second postulate appears in the second paper, eh, since, as Einstein says, the constancy of the speed of light is implied by Maxwell's equations? --Michael C. Price talk 23:40, 20 February 2008 (UTC)
The principle of lightspeed invariance DOES appear in Einstein's paper on mass-energy equivalence, in the very sentence that you quoted. In that sentence he is re-asserting the fact that the derivation of the Lorentz transformation (and hence special relativity) in his paper devoted to that subject relies on this principle, and moreover that his heuristic argument for the equivalence of mass and energy also relies on that principle, as well as additional features of Maxwell's equations.
Look, read Einstein's 1907 paper on special relativity, and then read his 1909 paper on the derivation of special relativity, and then read his 1912 paper on the derivation of special relativity, and then read his 1916 book, and then read his 1921 Princeton lectures, and then read his 1922 lectures in Japan on the origin of special relativity, and then read his Nobel Prize acceptance speech (1922)... etc. etc.... and then read his 1936 essay on Relativity and Physics, and then read the discussion of the derivation of special relativity in The Evolution of Physics (1938), and then read his 1949 autobiography in which he discusses the derivation of special relativity, and then read all the other miscellaneous articles and notes he wrote on the foundations of special relativity. When you've done then, you will see that he steadfastly maintained that special relativity was founded on two principles, that of relativity and lightspeed invariance. Then if you read the four papers he wrote over the years given various heuristic arguments for mass-energy equivalence (which is a different subject from the derivation of special relativity) you will see he consistently invoked Maxwell's equations, but only reluctantly, and always noting that this entailed the lightspeed principle, so it was simply adding other postulates to the two needed for the derivation special relativity. If you insist, exact citations and quotations from all these references can be inserted into the article, but it's rather ridiculous, since it is quite well known and uncontroversial that special relativity does NOT follow from the principle of relativity alone. That principle allows only the derivation of the space-time transformation up to a constant whose value many be positive, zero, or negative, corresponding to Euclidean, Galilean, or Minkowskian relativity, and to quantify the relations in physically meaningful terms it is necessary to associate the constant with some physically identifiable value, which Einstein did by associating it with the speed of light. This is not controversial. Every reputable source, both historical and modern, agrees with this. I urge you to acquaint yourself with the vast literature on this subject, and to stop trying to insert your erroneous and unsourced POV assertions into the article. Thanks. 63.24.104.19 (talk) 07:29, 21 February 2008 (UTC)
The principle of lightspeed invariance DOES appear in Einstein's paper on mass-energy equivalence, in the very sentence that you quoted. Yes, of course it does, as a consequence of Maxwell's equations, as Einstein says: ""The principle of the constancy of the velocity of light is of course contained in Maxwell's equations." There really is no disagreement here. --Michael C. Price talk 10:05, 21 February 2008 (UTC)
I think there is a fundamental disagreement here, because you say Einstein "dropped" the second postulate in papers where he postulated the entirety of Maxwell's equations relativistically interpreted, despite the fact that he explicitly noted that this postulate includes the invariant lightspeed postulate as a subset. The very sentence that you cite in support of your claim that Einstein dropped the lightspeed postulate says explicitly that he did no such thing. My preference is for the article to accurately represent the sourced material. I believe this is in accord with Wikipedia policy, and I intend to continue correcting inaccurate statements, and I will try to remember in each case to give properly sourced citations. (Sometimes I assume all this stuff is so well known that it doesn't need to be sourced, but I can see that this article will never be untangled until we begin to strictly enforce the sourcing policies of Wikipedia. No more of this "Some people believe this, and other people believe that" nonsense. Stick to published material from reputable sources, and do not paraphrase. And do not claim X and cite as a reference a statement that says not-X.Denveron (talk) 03:21, 22 February 2008 (UTC)
You're right, some things do have to be spelt out in painful detail: The very sentence that you cite in support of your claim that Einstein dropped the lightspeed postulate says explicitly that he did no such thing. This sentence is gibberish. Einstein dropped the lightspeed postulate by noting that it could be derived by the application of the principle of relativity to Maxwell's equations. Ergo it was no longer a lightspeed postulate. Ergo Einstein had dropped the lightspeed postulate. Okay?
Oh, and BTW, it is quite okay in Wikipedia to say "Some people believe this, and other people believe that" provided sources are cited for all POVs. Glad you agree that Einstein relativistically interpreted Maxwell's equations -- but please note that he did not introduce them as an explicit postulate, any more than he did the rest of classical physics. --Michael C. Price talk 08:03, 22 February 2008 (UTC)
He did not introduce Maxwell's equations as a postulate in any of his derivations of the Lorentz transformation, but of course he did make use of the principle of lightspeed invariance. He did this consistently and without exception from 1905 to his death in 1955, as is fully documented in the NPOV version of the article (the one you keep vandalizing), and he specifically avoided assuming the validity of Maxwell's equations, for the reasons explained in the NPOV article with full citations. On the other hand, in his heuristic arguments for the transmutability of energy and mass he DID postulate Maxwell's equations ("we base ourselves on Maxwell's equations", mass-energy equivalence "follows from the principle of relativity and Maxwell's equations", and so on), or rather, he postulated the relations involving the momentum and energy of electromagnetic waves implied by Maxwell's equations, in addition to the invariance of the speed of light. These facts are reported accurately and with full sourcing in the NPOV article that you keep vandalizing. I realize that these facts don't harmonize with your pre-conceived notions, but this does not entitle you to violate Wikipedia policy by inserting your own (erroneous) original research into the article.
Based on your latest bizzare claim ("Einstein did not postulate Maxwell's equations" in his mass-energy arguments), I can see I will now have to provide the exact quotes where he repeated says that he needs to assume Maxwell's equations for these arguments, which he would prefer not to do, but he had no choice at the (then) existing state of knowledge of electrodynamics. This is really tedious. Can't you just stop vandalizing the article with your crackpot POV?Denveron (talk) 18:43, 22 February 2008 (UTC)
I see you ignore the word explicit when it suits you. I repeat, Einstein did not introduce the constancy of the speed of light as an explicit postulate in his 2nd paper. Instead he derived it from Maxwell's equations -- which he did not raise to the status of an explicit postulate. --Michael C. Price talk 19:21, 22 February 2008 (UTC)

Historical approach to the postulates

Perhaps we need to abandon the historical approach, see e.g. here in particular point 3  :) Count Iblis (talk) 18:57, 22 February 2008 (UTC)

This would lead to even more disputation.--Michael C. Price talk 19:21, 22 February 2008 (UTC)
Giving a complete history would be very long and very confusing. But if one carefully selects those historical statements or discoveries which are still considered correct today, then it might be useful. Whether we begin with a selected history or just try to give the modern view, either way, we will still have a dispute because we differ over what the modern view is (or should be). JRSpriggs (talk) 20:02, 22 February 2008 (UTC)
I agree that abandoning the "historical approach" would lead to even more problems. Basically, Wikipedia policy mandates the "historical approach", in the sense that Wikipedia is not supposed to be arguing or judging the correctness of things, but simply reporting views that have been published by recognized experts in reputable sources... which amounts to a "historical approach"... although the vintage of the sources need not be so ancient.
I think the only viable solution is to strictly adhere to Wikipedia rules designed to exclude "original research". The rules state that the views expressed in the article must be views published in reputable sources. We will need to insist that every clause of every sentence has a reference, and the reference must very explicitly state the thing stated in the article. It was claimed by one of the editors above that it's okay in Wikipedia to say things like "Some people believe this and others believe that", but this misses the point. Sure, it is acceptable to state various views, but the point is that these must be views that have been published in reputable sources, not just views of Wikipedia editors. We can't just vaguely claim "some people believe X", we need to cite references in reputable sources stating X. Any statements that are unsupported by such explicit citations will have to be deleted from the article.
In the version of the article that I just edited, I've made a good faith effort to thoroughly source every assertion. This contrasts with other versions, which still contain unsourced "some people believe" statements. In my opinion, those statements violate Wikipedia policy.Denveron (talk) 20:53, 22 February 2008 (UTC)
Your opinion is not the final word. I have explained where and why you are mistaken about policy. As for reliable sourcing then what better source on the subject is there than Einstein, who in the second paper only had one explicit postulate?--Michael C. Price talk 22:31, 22 February 2008 (UTC)
First, the paper you are referring to does not present a derivation of the Lorentz transformation or special relativity, it discusses (in a speculative way, per the question mark in the title) the transmutability of mass and energy, which does not follow as a logical consequence of special relativity (see the reference to Rindler). Second, and just as importantly, you are factually wrong in your claim that it uses only one explicit postulate. Here is the full quotation, with the footnote included inline for clarity:
"The results of an electrodynaraic investigation published by me recently in this journal [On the Electrodynamics of Moving Bodies, 1905] lead to a very interesting conclusion, which shall be derived here. There I based myself upon the Maxwell-Hertz equations for empty space along with Maxwell's expression for the electromagnetic energy of space, and also on the following principle:
The laws governing the changes of state of physical systems do not depend on which one of two coordinate systems moving in uniform parallel translation relative to each other these changes of state are referred to (principle of relativity).
Based on these fundamental principles [The principle of the constancy of the velocity of light used there is of course contained in Maxwell's equations], I derived the following result, among others...
Now, do you see the word PRINCIPLES? Do you understand that appending an "s" to the word principle signifies plurality? Do you understand that when you claim Einstein's "second paper had only one explicit postulate" that you have omitted the "s" and are claiming that Einstein derived the result of that paper on the basis of just a single principle, when Einstein himself EXPLICITLY state that he derived the result based on at least TWO "fundamental principleS", and he even identifies one as "The principle of the constancy of the velocity of light", which is a subset of the premises underlying Maxwell's equations. Do you understand that he said exactly the opposite of what you claim he said? Sheesh....Denveron (talk) 04:08, 23 February 2008 (UTC)

Basically, Wikipedia policy mandates the "historical approach", in the sense that Wikipedia is not supposed to be arguing or judging the correctness of things, but simply reporting views that have been published by recognized experts in reputable sources... which amounts to a "historical approach"... although the vintage of the sources need not be so ancient.

But this is not (necessarily) the historical approach. E.g. we could have decided to present the theory of relativity in this article in the way Warren Siegel (the author of the critique on the historical approach) teaches it. You can find that in many textbooks, so it would be well sourced.
If one follows an historical approach to physics then one has to take into account that the discovered laws cannot be rigorously derived. There is always a lot of heuristics involved. But in the modern approach, we can simply define the law of physics we are talking about and then we can derive some important results/predictions of that theory. Because this is a rigorous mathematical approach, there shouldn't be any disputes. Count Iblis (talk) 22:56, 22 February 2008 (UTC)
The current NPOV version of the article notes that there are many possible sets of postulates for special relativity, so the whole section on postulates is really just of historical and methodological interest. I wouldn't mind deleting the entire section. But what I don't want is to have a section that asserts blatent falsehoods. The only problem with omitting the discussion of the postulates and the foundations of special relativity altogether is that the axiomatic aspect of special relativity was one of (if not THE) most salient features of the theory, and accounts largely for its larger significance in physics, that goes beyond its own technical results. But after seeing some of the editorial activity here, I fear this kind of material is beyond the grasp of some (highly determined) editors here, so the only solution may be to delete the section entirely - at least for 6 months or a year, until certain OR contributors lose interest.Denveron (talk) 04:08, 23 February 2008 (UTC)
The solution is to engage in honest debate with an open mind. Answer the questions raised. Try this one: where does the explicit light speed postulate appear in Einstein's 2nd paper?--Michael C. Price talk 07:24, 23 February 2008 (UTC)
Already asked and answered multiple times. As explained in the previous comments, Einstein paper on the inertia of energy was not a re-derivation of special relativity, it was an extension of special relativity, making use of results from special relativity derived, based on the two fundamental postulates, in the previous paper. He wrote:
Based on these fundamental principles [The principle of the constancy of the velocity of light used there is of course contained in Maxwell's equations], I derived the following result, among others...
This points explicitly to his use of the lightspeed principle to derive the basic results that he then proceeded to use in order to argue heuristically for the transmutability of energy and mass. Now, the question YOU have not answered is why Einstein wrote "Based on these fundamental principles" (plural), rather than "principle" (singular). What "principleS" was he referring to? You have claimed that in this paper he derived special relativity based on just a single principle (relativity), and yet this is flatly contradicted on two counts: (1) he is not deriving special relativity in this paper, and (2) he refers here to the paper in which he DID derive special relativity and says explicitly that it was based on multiple principleS, one of which he acknowledges was lightspeed invariance.

Let me try to address what I suspect is the source of your misunderstanding. Maxwell's equations, per se, are just a set of symbols, and have no physical meaning unless we assign to them some definite operational significance. It is entirely possible to reconcile "Maxwell's equations" with the principle of relativity. In fact, Maxwell himself did this. He believed with near certainty that electromagnetic effects were fundamentally mechanical, and that the mechanical basis of electromagnetism would eventually be discovered. He certainly proposed mechanical models that he hoped would lead eventually to an understanding of the ether. He also firmly belived in the principle of relativity, and wrote about it at length. Of course, he had in mind Galilean relativity, but the point is that the principle of relativity is not irreconcilable, a priori, with some construal of Maxwell's equations, because the meanings of the symbols are open to interpretation. In particular, Maxwell's equations are expressed in terms of space and time coordinates, but the operational meanings of these coordinates were ambiguous. Einstein saw that it was necessary, before we can even interpret Maxwell's equations, we must agree on what coordinate systems they apply to, and how those coordinate systems are operationally defined. This ambiguity also appears in the parameters representing the properties of permittivity and permeability. Maxwell's equations, themselves, don't tell us what these are properties OF. Maxwell (and Lorentz and everyone else before Einstein) regarded them as properties of the ether (which for all they knew was fundamentally mechanical entity). Likewise Maxwell's equations involve a parameter with units of a speed, but doesn't tell us the operational meaning of this parameter.

Prior to Einstein it was believed this speed was relative to the ether. This is perfectly consistent with the principle of relativity, provided we regard the ether as possessing physical properties and participating in physical processes somewhat like ordinary matter. But of course this view suggests that we can have different speeds relative to the ether (unless it is totally dragged with us, in which case there are other difficulties), so it ought to be possible to determine our speed relative to the ether. But, as Einstein noted, efforts to do this were consistently unsuccessful. The way out was to adopt this inability as a principle (like to inability to make a perpetual motion machine is a principle of thermodynamics), and this amounts to assigning a particular operational meaning to Maxwell's equations, which requires an operational definition of the space and time variables appearing in those parameters. Einstein saw that the stipulation of c (the operational speed of light) as a universal constant, independent of the state of motion through any hypothetical ether (or the vacuum), along with the stipulation of relativity, is sufficient to operationally determine the meanings of the space and time variables, as well as the parameters appearing in Maxwell's equations.

So this is why Einstein could not simply postulate Maxwell's equations, he saw that he needed a fundamental principle that would give unambiguous meaning to Maxwell's equations, and more generally to all physical laws involving space and time coordinates. Furthermore, he already knew Maxwell's equations themselves were not fundamentally correct (because they can't account for radiation), which explains why he said "it was as if the ground had been taken out from under us", and the only way forward was to identify some fundamental principle, in addition to the principle of relativity, that would suffice to establish the operational meanings of the variables and parameters appearing in physical laws. The necessary and sufficient principle is the invariance of lightspeed with respect to states of motion.

Of course, once we have established the Lorentz transformation and the meanings of the space and time variables for different frames of reference, it is then trivial to say "assume Maxwell's equations are valid in all frames of reference", but this has meaning only because we have previously defined how space and time coordinates transform from one frame of reference to another. Without that, the application of the principle of relativity to Maxwell's equations is hopelessly ambiguous.

Look, I'm not saying anything new or novel here. This is all yawningly old-hat to anyone who is acquainted with the vast literature on this subject. It is somewhat more subtle and complicated than newbies are often led to believe by their freshman physics instructors, but the above considerations are why people regard Einstein as genius, rather than an idiot, for basing special relativity on the principles of relativity and lightspeed invariance, which have survived all the subsequent advances in physics, because they weren't tied to any particular physical law (e.g., Newton's laws or Maxwell's laws), but to the most basic and assured principles, necessary and sufficient to give operational meaning to ANY physical law. This was such a brilliant insight that it seems a shame to bastardize it by the "original insights" of certain Wikipedia editors who frankly don't understand the first thing about theoretical physics.

Having said all this, let me also point out that it is all irrelevant. Wikipedia policies were designed specifically to avoid the kind of "honest debate" that some editors propose. Per Wikipedia policy, Wikipedia is NOT the place for debate (honest or otherwise) of the subject matter. Jimbo Wales realized that physics cranks can NEVER be convinced. That is essentially the DEFINITION of a physics crank. Hence, the Wikipedia rule is to base decisions for inclusion not on whether something is true or false, but whether it has appeared in a reputable published source. The version of the article I favor is FAR more sourced than the original research version ("some people think") that other editors are promoting. I contend that the fully sourced NPOV version is the one that should be adopted.63.24.122.252 (talk) 18:31, 23 February 2008 (UTC)

Tackling the only substantive point you make: the plurality of "principleS", as you put it. Einstein is quite explicit. One principle is the principle of relativity, the other is Maxwell's equations. He is quite explicit. Here are paragraphs 2 & 3::

I based that investigation on the Maxwell-Hertz equations for empty space, together with the Maxwellian expression for the electromagnetic energy of space, and in addition the principle that:--

The laws by which the states of physical systems alter are independent of the alternative, to which of two systems of coordinates, in uniform motion of parallel translation relatively to each other, these alterations of state are referred (principle of relativity).

With these principles[The principle of the constancy of the velocity of light is of course contained in Maxwell's equations], I derived........

I do like the "of course" bit. Note that he is saying this is how he produced the results appearing the first paper as well. --Michael C. Price talk 21:38, 23 February 2008 (UTC)

You previously claimed that "Einstein did not introduce [Maxwell's equations] as an explicit postulate, any more than he did the rest of classical physics", but now you conceed (finally!)that he adopted Maxwell's equations as one of his "principleS" in his paper giving a heuristic argument for mass-energy equivalence, and you also conceed (presumably) the obvious fact that this is (as Einstein noted with the "of course" that you're so fond of) tantamount to adopting the principle of lightspeed invariance.

If you're still having trouble grasping this, ask yourself what it means to adopt Maxwell's equations as a principle. Those equations can be reconciled with the principle of relativity in (infinitely) many different ways. To give this principle meaning, we must assert (among other things) that the parameters appearing in those equations take the same numerical values when evaluated with respect to any system of inertial coordinates, as operationally defined. Now, the parameters characterizing Maxwell's equations are the electrostatic and magnetic units, whose ratio is the speed of light, so the only way of postulating Maxwell's equations in a sense compatible with special relativity is to assert that the speed of light has the same numerical value with respect to any system of inertial coordinates. If you do not explicitly stipulate this, the postulate of "Maxwell's equations" is hopelessly ambiguous, and does not suffice to single out the Minkowski metric. Conversely, if you DO stipulate the invariance of the ratio of electric to magnetic units, then none of the remaining assumptions entailed in Maxwell's equations (some of which are invalid) are needed. This is why, as Einstein specifically said, he avoided postulating Maxwell's equations in the derivation of the Lorentz transformation.

Look, the result from the first paper on which he bases the second paper is the equation for the energy of an electromagnetic wave with respect to relatively moving systems of inertial coordinates. This comes from Section 8 of the first paper, which is in the "Electrodynamic Part" of that paper, in which he applies the Lorentz transformation - derived in the "Kinematic Part" of the paper, based on the two postulates - to Maxwell's equations. At the conclusion of the Kinematic Part he says

We have now derived the required propositions of the kinematics that correspond to our two principles, and we will now proceed to show their application in electrodynamics.

So you see, he has already derived the Lorentz transformation, which as he repeatedly stressed is the entire content of special relativity, and he is proceeding to apply this to one particular class of physical phenomena, namely, Maxwell-Lorentz electrodynamics. In this part of the paper he derives the relativistic expression for the energy of an electromagnetic wave (in accord with Maxwell's equations), and it is this result that he uses in the second paper. This is why he says in the second paper, referring to the first, "There I based myself on the Maxwell-Hertz equations". He is saying this was the basis of the expression for the energy of an electromagnetic wave, but of course the relativistic form comes from applying the kinematics of special relativity, which was derived in the first part of the earlier paper based on the two postulates of relativity and lightspeed invariance.

If you have any understanding at all of the actual content of those two papers, his statements are perfectly clear and cannot possibly be mis-interpreted. Your claims are falsified in so many different ways that is becomes ever more tedious to enumerate them. And you conspicuously decline to reconcile your claims about Einstein "dropping the second postulate" with the fact that in over a dozen papers written over the next fifty years of his life he consistently asserted the primacy of the lightspeed postulate, often listing it first rather than second (which is why it's not good to refer to them as "first" and "second" postulates). And you refuse to comment on why he repeatedly made statements explaining why he based special relativity on those two postulates and NOT on Maxwell's equations. And on and on.

All we're doing here is proving the wisdom of the Wikipedia rules designed to suppress physics cranks. It does no good to argue with physics cranks. All we can do is insist that the article contain ONLY sourced statements from reputable publications. My version is thoroughly sourced. The alternate version is essentially just an unsourced statement of some editors opinions. The repeated reversions to that unsourced POV original research is beginning to look a lot like vandalism.Denveron (talk) 00:57, 24 February 2008 (UTC)

All we can do is insist that the article contain ONLY sourced statements from reputable publications. So why do you repeatedly delete the sourced statement The principle of the constancy of the velocity of light is of course contained in Maxwell's equations.? Note that I previously said that Einstein no more postulated Maxwell's equations than he did the rest of classical physics. However, if you wish to interpret that as postulating Maxwell's equations (despite them already being accepted physics), I don't care. Let's stick with the sources. BTW if you continue to label anyone who disagrees with you as a crank you will be reported. Your relativity activities got you banned before; will happen again. --Michael C. Price talk 04:12, 24 February 2008 (UTC)
Already asked and answered (multiple times). The paper you are referring to does NOT present a derivation of the special relativity or the Lorentz transformation, so the principles on which the argument in that paper are based are not relevant to the principles on which the derivation of Lorentz invariance (which is the content of special relativity) is based. Now, Einstein does refer back to the earlier paper, but as I've already taken the trouble of explaining in detail, he is referring to the basis of the expression for the energy of an electromagnetic wave, which was derived in Part 2 of the previous paper, where he applies the Lorentz transformation to Maxwell's equations. This is the meaning of the sentence you keep quoting. Your claims are false because you present the quotation as if it was describing the principles for deriving the Lorentz transformation, which it very clearly was not. Please re-read the previous discussion which explains exactly what that sentence was referring to. This is not a controversial point. Any Einstein scholar will tell you the same thing.
The only thing I can think of that somewhat resembles what you've been claiming is the following:
In his discussion of the energy and momentum of electromagnetic waves, which Einstein began in Part 2 of his first paper, and continued in a subsequent paper, Einstein applied the Lorentz transformation (derived on the basis of the two fundamental postulates) to the energy and momentum of electromagnetic waves based on the assumption of the validity of Maxwell's equations. Of course, the assumption of Maxwell's equations (in this context) entails among other things the assumption of the constancy of the speed of light.
So, to be as accommodating as possible, I've added this kind of verbiage to the article.Denveron (talk) 04:53, 24 February 2008 (UTC)
The paper you are referring to does NOT present a derivation of the special relativity or the Lorentz transformation, -- another of your typically irrelevant half-truths, since Einstein is referring to his first paper which he says is based on Maxwell's equations. But I give up -- no one here seems particularly interested in presenting relativity in a way readily comprehensible to newbies. You're right, it is so much easier to present the idea that the constancy of the speed of light dropped out of heaven into Einstein's brain -- why mention the preceding work of Maxwell which implied this? After all Einstein wasn't standing on the shoulders of giants, was he? --Michael C. Price talk 06:09, 24 February 2008 (UTC)
Please look again at what I wrote. I specifically addressed your complaint (for the third time). For your benefit, I'll repeat it (again), with the answer to your objection bolded this time:
"The paper you are referring to does NOT present a derivation of the special relativity or the Lorentz transformation, so the principles on which the argument in that paper are based are not relevant to the principles on which the derivation of Lorentz invariance (which is the content of special relativity) is based. Now, Einstein does refer back to the earlier paper, but as I've already taken the trouble of explaining in detail, he is referring to the basis of the expression for the energy of an electromagnetic wave, which was derived in Part 2 of the previous paper, where he applies the Lorentz transformation to Maxwell's equations. This is the meaning of the sentence you keep quoting. Your claims are false, because you present the quotation as if it was describing the principles for deriving the Lorentz transformation, which it very clearly was not."
After supposedly reading the above, you accuse me of ignoring the fact that Einstein referred back to the first paper, but of course the entire bolded text addresses that very point.
I'm sorry, but it simply is not possible to credibly account for the documentary evidence with any novel narrative of the kind you are trying to insert into the article. Einstein based his derivation of the Lorentz transformation on the principles of relativity and lightspeed invariance. He did this in every single presentation of that derivation he ever published over 50 years (which amounts to at least a dozen papers, articles, and books). Your attempt to contradict this well-established fact by quoting his comment from a paper on a different subject, and trying to mis-lead the reader by calling it "his second paper on special relativity", and presenting this as if he was talking about deriving the Lorentz transformation, is both dishonest and misleading. I explained above that the result from the first paper that he used in the second paper to argue for mass-energy equivalence was the expression from Part 2 of the first paper, AFTER deriving the Lorentz transformation, where he applies the principles of special relativity to the subject of Maxwell's equations. Hence the reference in the second paper to the use of Maxwell's equations in deriving that result. I don't know how to say this any more clearly. I can only suggest that people read both papers for themselves. Look at the result that Einstein is referring to in the second paper, and note that it comes from Section 8 of the first paper, which is in Part 2, AFTER the derivation of the Lorentz transformation. I think anyone who reads those papers (with comprehension) will have no trouble understanding the meaning of the sentence in question.63.24.48.65 (talk) 07:34, 24 February 2008 (UTC)
You are tilting at windmills. The points you make that are correct are irrelevant. You and number of other editors continue to not see the wood for the trees, arguing about issues that are not relevant (and accepted by everybody) while ignoring the issues that are relevant (and also accepted by everybody). See Wikipedia_talk:WikiProject_Physics#Edit_war_over_postulates_of_special_relativity --Michael C. Price talk 07:18, 26 February 2008 (UTC)

The statements you've been trying to insert into the article ("Einstein dropped the lightspeed postulate", and "Einstein believed the lightspeed postulate was redundant to Maxwell's equations") are both technically wrong and historically incorrect. The quotation you cited in support of these statements actually contradicts them. This has all been thoroughly explained on this discussion page (see above), with abundant references to reputable sources. Your proposed words constitute a "novel narrative" and therefore are not admissible per Wikipedia policy.Denveron (talk) 21:05, 27 February 2008 (UTC)

So what is it that you disagree with? That Einstein was inspired by Maxwell's equations; that there was no explicit 2nd postulate in his second paper; that the speed of light can be derived from Maxwell's equations? --Michael C. Price talk 03:43, 29 February 2008 (UTC)
Each of your questions has already been asked and answered several times, in considerable detail on this discussion page. (See above.) It has been thoroughly shown that your proposed text for the article is inadmissible per the Wikidia policies regarding "original research", "novel narratives", and verifiability.Denveron (talk) 03:28, 1 March 2008 (UTC)
My points have not been addressed by you and some others -- you're assuming I'm a relativity crank and not paying attention. I'm talking about the origins of the theory -- you and some others are taking about the current status of the theory. As Einstein said in a letter to the Michelson Commemorative Meeting of the Cleveland Physics Society (as quoted by R.S.Shankland, Am J Phys 32, 16 (1964), p35, republished in A P French, Special Relativity, ISBN 0177710756)
"What lead me more or less directly to the special theory of relativity was the conviction that the electromotive force acting on a body in motion in a magnetic field was nothing else but an electric field."
--Michael C. Price talk 07:12, 17 March 2008 (UTC)
To MichaelCPrice: You said "I'm talking about the origins of the theory...". In that case, would your point not be more appropriately made in History of special relativity which is linked from this article? JRSpriggs (talk) 07:28, 17 March 2008 (UTC)
Good suggestion. And of course a summary would appear in this article as well. --Michael C. Price talk 07:31, 17 March 2008 (UTC)

please fix ref

Something has gone wrong with reference no. 10, it's full of unprocessed tags and none of the references below 10 are showing. Has somebody forgotten to close </ref>? 131.111.8.102 (talk) 19:39, 24 February 2008 (UTC)

Someone added a second <ref> tag in that section. I removed it. -- Ricky81682 (talk) 19:45, 24 February 2008 (UTC)

The section ?3 of the 1905 paper

The second equation in the section ?3 of the1905 paper is established on the assumption that when Einstein used the method defined in the section ?1 to synchronize all clocks in the stationary system K he could still use the method ?1 to synchronize a slave clock S in system k to a master clock M at the origin of system k. System k is moving away from system K at constant velocity v with axes y’ and z’ parallel to axes y and z, and axes x’ lay on axes x. We also let all clocks be in all respects alike. We will look into that assumption in 3 situations:

1. For the situation when the stationary system K is not moving at all. It is easy to prove above assumption is invalid. We will prove Regulation one and use it to verify the situation 1. In method ?1, let the emitting point be O, the reflecting point be R, and the ending point be O’. Let OR and O’R represent the distances between related two points.

Regulation one: If we can use method ?1 to synchronize the slave clock B to the master clock A then OR=O’R. To prove it we start from the given condition that the clock B can be and is synchronized to the clock A by method ?1. That means at the time the clock A showed tA when the ray emitted the clock B would also show tA and both clocks showed same time for tB and tA’ too. Since tB-tA=tA’-tB, to both clocks A and B, the light ray spent equal time from point O to R and from point R to O’. Since the speed of light is not related to the speed of the emitter we time the same speed by the same time period and get the same distance OR=O’R. Regulation one is proved. Logically speaking, the reverse of this regulation is also true: if OR is not equal to O’R then we cannot use method ?1 to synchronize the clock B to the clock A.

If the system K is not moving at all then the system k is moving. Let the ray emitted at point Om and reflected at point Rs then ended at point Om’. Since the system k is moving along x axes, we have point Om’ in between points Om and Rs. That means OmRs>Om’Rs. According to Regulation one, we are not allowed to use method ?1 to synchronize the clock S to the clock M in the system k.

Under this first situation, the assumption Einstein used to derive the second equation in the section ?3 of the1905 paper is not valid. Hence the proof of Lorentz Transformation in the section ?3 following that second equation in the section ?3 is not valid. Now, let us look into more complicated situation 2.

2. For the situation when the system K moves and we can use method ?1 to synchronize clocks in any system to master clocks in the system K. We will prove that the system K cannot move. For a given master clock N in the system K, let the clock N emit two rays at point On to two clocks S1 and S2 in the stationary system at locations point R1 and R2 where point On is the center point of the segment connecting R1 and R2. We have OnR1=OnR2. Let the ending points be O1’ and O2’ then we have OnR1=O1’R1 and OnR2=O2’R2. That means the point O1’ is on the sphere of radius OnR1 and center R1 while the point O2’ is on the sphere of radius OnR2 and center R2. Since On is the only point on both spheres, it is impossible for the clock N to move to one sphere and receive both reflection rays. That means, the clock N cannot move. That means any point of the system K cannot move and the system K is not moving at all. We proved that the situation 2 has the same result as situation 1.

3. For the situation when the system K moves and we can use method ?1 to synchronize clocks in the system K to each other. I have solved only part of the solution that is when all clocks in the system K are moving slower than 0.7C related to the emitting point O, reflecting point R, and ending point O’ in the synchronization, where C is the speed of light.

Regulation two: I will prove that within above situation if all clocks in the system K can be synchronized to each other by the method ?1, then the system K cannot not move at all.

If no clock is moving, Regulation two is proved. If some clocks are moving, we select the one with fastest moving speed and name it the master clock A, the moving speed of the clock A is smaller than 0.7C as we assumed. Our next step is to build a coordinate system with point O as the origin and select the direction where the clock A is moving to, when the ray emitted, as positive direction of x axes. Let us synchronize the clock X located at U(1,0,0) to the master clock A at O(0,0,0). That means, we emit the light ray at point O to the expected reflecting location of clock X. Let the reflection point be R then the end point of the synchronization be O’. We will prove that if the moving speed of the clock A is smaller than 0.7C then to synchronize the clock X to the master clock A is impossible so long as the moving speed of the clock X is not faster than the clock A.

To make the proof easier, we reduce the unit length so that the end point O’ will be so close to the point O that it is on the x axes with coordinate (ox,0,0) and the moving speed of the clock A is a constant speed in that period of time. Let P be the center point between O and O’, then (ox/2, 0,0) is the coordinate of the point P. If we can synchronize the clock X to the clock A, then there is a reflecting point R that OR=RO’ and we have PR=OU=1. When the clock A moved from the point O to P, the clock X moved from the unit point U(1,0,0) to R and the ray moved from the point O to R. If the speed of the clock A is less than 0.7C, we have UR>1>OP. However, that is against to our selection that the clock A has the fastest moving speed. That means whichever clock has the fastest speed would not be able to synchronize a clock X at the direction of its moving. That means to synchronize all other clocks in the system K, a master clock cannot have moving speed at all if it is not faster than or equal to 0.7C.

The second equation in the section ?3 of the1905 paper is not true when all clocks in the system K have moving speed less than 0.7C. Because in that case we have proved that the system K is not moving at all, related to the event points, so that according to situation 1, the method ?1 could not be used for the system k.

4. For the situation when some clocks in system K is moving faster than 0.7C related to the emitting point O, reflecting point R, and ending point O’ of the synchronization, where C is the speed of light, I don’t have a solution yet. I have to think about it.

John C. Huang (talk) 01:16, 17 March 2008 (UTC)

4. I have found the solution. For the situation that clocks in the system K have moving speed less than the speed of light we will prove that if all clocks in the system K can use the method ?1 to synchronize each other then clocks in the system K cannot move at all.

In situation 3, let the moving speed of the master clock A be smaller than the speed of light and let another slave clock Y at (1/2,0,0) be synchronized by the clock A at the same time. Let the reflecting point be Ry and the ending point be Oy(oy,0,0) so that the point Py(oy/2,0,0) is at middle of points O and Oy. Compared with the clock X, the clock Y is closer to the clock A so that we should have oy<ox.

When the clock A moved from point O to Py, the clock Y moves from (1/2,0,0) to Ry. Since the clock Y is always staying at the middle of clocks A and X at any time in any way the system K moves, when the clock A was at point Py and the clock Y was at point Ry we could locate the clock X at a point Rx, PyRx=1. Now, let us look into the way the clock X moved when we synchronized it to the clock A. The clock X moved away from x axes up to the reflecting point then started moving back to x axes after that so that in the whole process of synchronization, the distance between the clock X and x axes is less than 1 except at the reflecting point that the distance is equal to 1. We proved that the point Rx is the same as the point R, so that the point Py is the same as the point P and oy=ox. That is conflict to the fact that oy<ox.

We have proved that the clock A with the fastest moving speed in the system K cannot use the method ?1 to synchronize both clocks X and Y at the same time. That means to use the method ?1 to synchronize all clocks in the system K to each other, every clock in the system K cannot move at all. Per situation 1, Einstein could not use the method ?1 to synchronize two clocks in the moving system k.

John C. Huang (talk) 16:30, 2 April 2008 (UTC)


"This theory has a wide range of counterintuitive consequences, all of which have been experimentally verified." This is an extremely dubious statement. To be as generous as I can possibly be. It ought not be in the article. —Preceding unsigned comment added by 122.148.183.191 (talk) 11:17, 12 April 2008 (UTC)

Please clarify with which part do you disagree: That the consequences are counterintuitive? That there is a wide range of them? That they have all been verified? Or what? JRSpriggs (talk) 12:55, 12 April 2008 (UTC)
The statement that the consequences are counterintuitive is debatable and probably not universally agreed upon - it's certainly subjective and depending on the way of thinking of the reader. Harald88 (talk) 16:11, 12 April 2008 (UTC)
To Harald88: Agreed. I changed the sentence to "This theory has a wide range of consequences which have been experimentally verified.". So it no longer claims that the consequences are counterintuitive nor that all of them have been verified (because not all may have been tested). JRSpriggs (talk) 07:12, 13 April 2008 (UTC)


The second postulate

Carnildo's statement is: "The second postulate is three separate claims:

1. The speed of light is the same to all inertial observers 2. The speed of light is the same in all directions 3. The speed of light does not depend on the velocity of the emitter

The second claim was verified by the Michelson-Morley experiments, and the third was verified by the experiments that disproved emitter theory. For the third claim, [1] cites Alvager et al., Physics Letters 12, 260 (1964) as being the definitive study. I don't know of any experiments that that have verified the first claim, but I'm sure they're out there. --Carnildo 22:46, 10 Dec 2004 (UTC)" and he provided some verification about "one way" speed of light for the second claim.

I will try to make a test for the first claim and hope Carnildo can help to make it better or make it not valid:

We need 3 timers which are able to record nanoseconds. One built into a switch on-off red light bulb, one built into a switch on-off yellow light bulb, and one built into a camcorder. We synchronize the timers to the best we can and write down their related times: Tr, Ty, and Tc. We let Mr. Cam sets up the camcorder to record two events started from Tc+9 minutes to Tc+11 minutes. Mr. Red put the set of red light bulb on a table 30 meters away from the camcorder performs the first event, sets up the red light bulb be turned on at Tr+10 minutes then turned off at 20 nanoseconds later while Mr. Yel put the set of yellow light bulb on a tea table in between the table and camcorder, 6 meters away from the camcorder, performs the second event, sets up the yellow light bulb be turned on at Ty+10 minutes and 80 nanoseconds then turned off at 20 nanoseconds later.

We don't let Mr. Cam know the starting time of events. At Tc+22 minutes, three workers look at the recorded time which should show that the red light and yellow light were turned on at about Tc+10 minutes and 100 nanoseconds and lasted for 20 nanoseconds. They then calculate the speed of light from the known distance:

Mr. Red has 30 m / (100-0) ns = 0.3 m/ns and Mr. Yel has 6 m / (100-80) ns = 0.3 m/ns but Mr. Cam has some difficulty. The recorded two events happened at the same time means the event-starting pictures arrived the camcorder at the same time, Tc+10 minutes and 100 nanoseconds; but what are the event starting times? What is your answer? There are two answers, general publics will say according to the recorded vedio, both light bulbs was turned on at Tc+10 minutes and 100 nanoseconds; the other answer is don't know, depend on how far away are the light bulbs and since the speed of light is to be decided, unable to calculate the time. If Mr. Cam is one of the general public, then the result of calculation is 30 m / 0 ns and 6 m / 0 ns, unlimited fast. That is different from the results of Mr. Red and Mr. Yel.

(Note: Actually, all photons reach at our eyes are calculated by our brain like running at unlimited speed. :)) John C. Huang (talk) 20:04, 12 January 2008 (UTC)

Please stop adding your original research to article talk pages., DVdm (talk) 10:02, 13 January 2008 (UTC)

Thanks. I would not do it any more. However, could any one provide a verification for the first claim? I realy like to know. John C. Huang (talk) 16:35, 14 January 2008 (UTC)

See the article on "Speed of Light", especially the section on measurements of this speed, which have been carried out in different frames of reference (since the Earth is in different states of motion at different times of the year), and which consistently yield the same value. By 1972 this measured by Evenson as 299792.4574 ± .0012 km/s, regardless of the time of year.
Having said that, I should add that Wikipedia Talk pages are not to be used for asking people to explain the subject. 63.24.99.44 (talk) 06:23, 15 January 2008 (UTC)

Thanks for your concern. People don't know much about C, the speed of light. Photons do not need acceleration to reach C and the only light we can see or a camcorder can record is the light runs directly into our eyes or the lens. If the speed of gravity force and electromagnetic force are C then no matter how strong the electromagnetic force is applied to the electron, the speed of that electron can not be higher than C like a balloon pulled by a train cannot go faster than the train no matter how powerful the train is. We don't know much about C.

The measurements you mentioned about were not designed to verify the first claim. What is the speed of light recorded by a camcorder? Is that C? How do you calculate it? I was not asking for people to explain the subject. I asked people to help to think about it. John C. Huang (talk) 06:15, 24 January 2008 (UTC)

I have found a way to verify that the speed of light is unlimited fast when it runs toward the camcorder and the speed of light is C/2 when it runs away from the camcorder.
We replaced Mr. Yel by Mr. 24m and Mr. 12m, we also replaced the yellow light-bulb by two glass rings of diameters 24 inches and 12 inches both with width of 6 inches. The ring24 had clear bottom half and transitable red upper half (so that some of the red light would go through and some of the red light would reflect) and the ring12 had clear upper half and transitable yellow bottom half. We then replaced the red light-bulb by clear light-bulb and removed the tea table. Let Mr. 24m stretched out his right arm held the ring24 at distance of 24 meters away from the camcorder and Mr. 12m stretched out his left arm held the ring12 at distance of 12 meters away from the camcorder the centers of the clear light-bulb, ring24, ring12, and the lens of the camcorder were about on one straight line. Then Mr. Cam started recording and Mr. Red turned on the clear light-bulb for 20 ns. Then we reviewed what was recorded. The result should be quite like all the center light, upper red, and bottom yellow all lighted up at Tc+10 minutes and 100 ns and lasted for 20 ns. That verified that the speed of light from ring24 to ring12 is unlimited fast to the observer.

Then, we let Mr. Cam moved to under the table to record both rings. We let Mr. Cam started recording from Tc+29 minutes to Tc+31 minutes. Let Mr. Red turned on the clear light-bulb from Tr+30 minutes to Tr+30 minutes and 20 ns. After that, we reviewed the recorded result. We should see ring24 lighted at around Tc+30 minutes and 40 ns, lasted 20 ns; then ring12 lighted at around Tc+30 minutes and 120 ns, lasted 20 ns. The calculated speed of light from ring24 to ring12 is about (24m-12m)/(120ns-40ns)=0.15m/ns and that is about C/2. Do you think this experiment make sense?

Please help. Thanks. John C. Huang (talk) 17:34, 26 January 2008 (UTC)

This is not an original research, it is a fact. John C. Huang (talk) 17:47, 26 January 2008 (UTC)

But Einstein is the one who said the speed of light is the one constant in the universe and travels at the same speed in all reference frames so unless you think he is wrong, that can't be right. Skeletor 0 (talk) 16:31, 3 June 2008 (UTC)

Maxwell's Equations are NOT a Postulate of Special Relativity

Some editors have suggested inserting claims in the article to the effect that the lightspeed invariance postulate follows from Maxwell's equations, and that therefore the lightspeed postulate can be replaced by simply postulating Maxwell's equations. This is not accurate either technically or historically. As Einstein later explained, he already knew by 1905 (see his 1905 paper on light quanta) that Maxwell's equations were not fundamental, and in fact were wrong. He very specifically avoided basing special relativity on Maxwell's equations. Of course, he also explained in several places that if we assumed Maxwell's equations had the same form in all systems of inertial coordinates then the lightspeed postulate follows, but this is to assume much more than is needed. Also note that Lorentz assumed Maxwell's equations too, but only for the system of space and time coordinates at rest in the ether, and hence Maxwell's equations need not be understood to imply lightspeed invariance. Maxwell himself understood this and wrote about it. Look, whole books have been written about why Einstein specifically chose to base special relativity on the two postulated that appear in the 1905 paper. It would bog down the article to explain all this in detail. But the article needs to be written in a way that is consistent with both the technical facts and the historical facts, and this can only be done by people who are acquainted with both. Notice that the claims inserted in the article about special relativity being based on Maxwell's equations are unsourced. This is because the editor(s) inserting those claims are really just inserting (erroneous) "original research", i.e., their own (mis)conceptions. It would be beneficial to the article (in my opinion) to remove those erroneous and misguided statements.Denveron (talk) 15:51, 17 February 2008 (UTC)

It is not OR - I have read many times that Einstein derived SR from MEs. BTW no one is claiming that "ME are a postulate of SR", so I don't what the point of the section title is. --Michael C. Price talk 16:37, 17 February 2008 (UTC)
I believe you're mistaken when you say no one is claiming ME are a postulate of SR. Here is what you inserted into the article in a recent edit: "Einstein derived the second postulate about the invariance of the speed of light from the first postulate, by applying the principle of relativity to Maxwell's equations". Needless to say, this is a weird statement in several respects... for example, it talks about "deriving" a postulate. But even if we overlook this weirdness, your assertion is clearly that the foundation of special relativity is the principle of relativity combined with Maxwell's equations, from which (you assert) the lightspeed postulate is "derived". Hence you are making Maxwell's equations an underlying postulate, smuggling it in through the back door. This, as I explained above, is wrong. Einstein specifically avoided basing special relativity on Maxwell's equations, because he already knew Maxwell's equations were not fundamentally correct. Of course, he also knew they contained an important kernal of truth, which he extracted in the form of the lightspeed invariance postulate, which is just as valid in quantum electrodynamics as it was in Maxwellian electromagnetism.
To say "Einstein derived special relativity from Maxwell's equations" is so vague as to be neither true nor false. Certainly the Lorentz invariance of Maxwell's equations was a crucial fact, so in that sense it is true. But Maxwell's equations were already known to be not fundamental, so it was necessary to identify the key feature of those equations, and the single simple fact that must underly any successful theory of electromagnetism. This was the principle of lightspeed invariance. It is formally a principle that was inferred from (among other things) the success of Maxwell's equations, but this principle cannot be "derived from" Maxwell's equations unless we first postulate Maxwell's equations, which we know are wrong at the fundamental level.
I would just say that any claims in the article ought to be supported by direct quotes from reputable sources, and not just paraphrases based on editors assurances that they have "read many times that Einstein derived SR from MEs". The undeniable fact is that Einstein's 1905 paper explicitly derives special relativity not from Maxwell's equations, but from two principles, one being lightspeed invariance. This has proven to be a sound basis, even after Maxwell's equations were shown to be wrong. Claims that special relativity assumes the validity of Maxwell's equations are simply wrong. This is one of the great features of special relativity... the solidity of its premises.63.24.127.205 (talk) 17:18, 17 February 2008 (UTC)
There is nothing "weird" about my claim, nor is it an isolated claim of a relativity crank: Einstein's first postulate is that the physical laws of nature are the same in all inertial reference frames. His second postulate is simply a consequence of applying this principle to the laws of electricity and magnetism......Einstein's first postulate seems perfectly reasonable. And his second postulate follows very reasonably from his first. How strange that the consequences will seem so unreasonable. --Michael C. Price talk 17:41, 17 February 2008 (UTC)
As for sources, look at the footnote from AE's 1905 relativity second paper, which never mentions the second postulate, only the first, instead saying: "The principle of the constancy of the velocity of light is of course contained in Maxwell's equations." So there you have it, from the horse's mouth itself! --Michael C. Price talk 17:44, 17 February 2008 (UTC)
First, one does not derive postulates, so the weirdness (to put it kindly) of your assertions is beyond dispute. Second, the point of view you are expressing is a well-known and (unfortunately) fairly common misunderstanding among relativity newbies. When you say the lightspeed postulate follows from applying the relativity postulate to the laws of electricity and magnetism you are assuming those laws are given in advance, just as you could assume the laws of mechanics were given in advance. However, both the Newtonian and the Maxwellian laws are wrong (as we now know). Einstein says the relativity postulate must apply to the laws of electrodynamics as well as to the laws of mechanics - whatever those laws may be. In point of fact, it turned out that the laws of both mechanics and electrodynamics had to be modified in order to make them consistent with the principle of relativity and the principle of lightspeed invariance. The laws of mechanics were modified immediately beginning in 1905, and the laws of electrodynamics were modified when quantum mechanics was finally reconciled with special relativity by Dirac, eventually resulting in quantum electrodynamics. The point is, neither the laws of mechanics nor the laws of electrodynamics are premises of special relativity. Rather, special relativity imposes conditions on the form those laws must take.
Of course, it is true that Einstein included a footnote about Maxwell's equations in the "Inertia of Energy" paper in 1906, but that footnote does not say that special relativity is based on Maxwell's equations. It merely observes (correctly) that if Maxwell's equations are valid in terms of every system of inertial coordinates, then the lightspeed invariance follows. But as Einstein already knew, Maxwell's equations are NOT valid in ANY system of inertial coordinates, so it would have been considerably less brilliant of him to found special relativity on those equations. In the "Inertia" paper he is simply trying to make the lightspeed principle seem more plausible to people who were not accoustomed to it by relating it to Maxwell's equations, with the tacit proviso that they are held to be valid in terms of all systems of inertial coordinates.
This is why I didn't want to get into this in detail, because to give an accurate representation of the fact, you must include not just the footnote in one paper that doesn't even support your point, but the texts of the dozens of presentations of special relativity that Einstein wrote over his lifetime, in which he clearly and repeatedly emphasized that special relativity is based on lightspeed invariance, NOT on Maxwell's equations. You are obviously intent on inserting your POV into the article, and it will be quite easy to bury you in citations proving you wrong, but is this really a good use of anyone's time? Why not go and acquaint yourself with the vast literature?63.24.32.26 (talk) 20:07, 17 February 2008 (UTC)
One more point - the quotation of the footnote you gave was incorrect, as it omitted the two crucial words "used there". You aren't entirely to blame for this, because those words were omitted from the Dover booklet translation that most newbies read. To see what Einstein actually wrote, see the original German, or read the English translation in the Collected Papers (Princeton University Press). By saying "the principle of the constancy of the velocity of light USED THERE" he is re-affirming that this is the principle on which special relativity is founded, and then going on to add in a comforting way (for people who have more faith in Maxwell's equations than in Einstein's lightspeed principle) that Maxwell's equations imply the lightspeed invariance... with the tacit assumption that Maxwell's equations are valid with respect to every system of inertial coordinates, but since c appears in Maxwell's equations (as the ratio of electrostatic to magnetic units), this tacit assumption is tantamount to the assumption of lightspeed invariance. So lightspeed invariance follows from the assumption of lightspeed invariance. This is the only aspect of Maxwell's equations on which special relativity is founded. Hence your insistence on trying to give readers the impression that special relativity is based on some feature of Maxwell's equations other than lightspeed invariance itself is both technically wrong and historically inaccurate. Please stop.63.24.105.109 (talk) 20:38, 17 February 2008 (UTC)
  1. The inclusion of the words "used there" makes no difference to the meaning (which is why it probably was left out by the translators).
  2. I am not a relativity "newbie", so you can stop all the insinuations. I have a BSc (physics) and MSc (quantum field theory).
  3. I guess it was naive of me to think that presenting you with the source you asked for would actually change your mind, but that isn't important; what is important is that my POV (as you call it) has an unimpeachable source.
  4. And please give up all the elementary physics lessons about Maxwell's equations not being fundamental -- a complete red herring, since we are talking about classical mechanics here, not quantum mechanics. It is your position that is sounding like original research, not mine.
  5. Please provide sources for your claim that Einstein sought to avoid basing SR on MEs. The two foundational 1905 papers do not provide any evidence to support this view. Quite the contrary, they make continual reference to Maxwell and "electrodynamics". --Michael C. Price talk 20:55, 17 February 2008 (UTC)

Answers: 1) The words "used there" obviously make a very significant difference, which is why the more careful translators DID include it. Your (incorrect) version of the quote was the basis of your (erroneous) claim that the lightspeed postulate was not contained in the Inertia paper, but then you quoted the note that contained it, referring back to the foundational paper. 2) Don't care. 3) You call your mis-contrual of a mis-quotation an "unimpeachable source". I would hate to see what you consider an impeachable source. 4) You are confused. The topic here is special relativity, which is just as valid in quantum electrodynamics as in mechanics. Of course, neither of these are in their classical form, but that's the whole point. They had to be modified to be consistent with special relativity. If we took Maxwell's equations for granted (as you suggest we should do in founding special relativity), it would be incompatible with quantum electrodynamics. Fortunately, special relativity is not founded on Maxwell's equations, it is founded on the existence of an invariant speed. Your efforts to conflate these two things are not helpful. 5) Done. See the edited article.63.24.112.17 (talk) 23:31, 17 February 2008 (UTC)

Your entire position is one of OR, since the quotations provided do not demonstrate your case, only the lack of your ability to see both sides of the argument. The fact remains that back in 1905 Einstein dropped the 2nd postulate because he could derive it from the principle of relativity applied to Maxwell's equations. Here I quote the opening of his 2nd paper with the footnote inserted:

The results of the previous investigation lead to a very interesting conclusion, which is here to be deduced.

I based that investigation on the Maxwell-Hertz equations for empty space, together with the Maxwellian expression for the electromagnetic energy of space, and in addition the principle that:--

The laws by which the states of physical systems alter are independent of the alternative, to which of two systems of coordinates, in uniform motion of parallel translation relatively to each other, these alterations of state are referred (principle of relativity).

With these principles (The principle of the constancy of the velocity of light used there is of course contained in Maxwell's equations.) as my basis I deduced .....

What could be clearer! Three references to Maxwell. No second postulate.--Michael C. Price talk 00:11, 18 February 2008 (UTC)

Maxwell's equations are both too much and not enough to serve as a foundation for special relativity, and this is clear from all the vast literature on this subject. They are not enough because it is entirely possible to reconcile a Lorentzian view of Maxwell's equations with the principle of relativity without implying invariant light speed. (See Lorentz's theory.) They are too much because if you add the (necessary) stipulation that they must apply in the same form, with the same ratio of electric to magnetic units, in terms of all inertial frames, then they not only imply the invariance of light speed, they also imply a whole lot of other things... many of which are not true. Furthermore, to say that you can eliminate the second postulate by substituting another postulate (Maxwell's equations) and declining to call it a postulate is just, well, I'll refrain from characterizing it. 63.24.118.18 (talk) 02:39, 18 February 2008 (UTC)

Again, irrelevant OR. It doesn't alter the fact that Einstein used Maxwell's equations to derive c, and dropped the 2nd postulate in his 2nd paper. What he did towards the end of his life doesn't alter the historical record for 1905. --Michael C. Price talk 08:35, 18 February 2008 (UTC)
Einstein's paper on the inertia of energy is not a second attempt to derive special relativity, it is an attempt to show that at least some forms of energy have inertia, and for this limited derivation he stipulated Maxwell's equations (as covariant laws). Of course, this postulate contains as a subset the postulate of invariant lightspeed, so it in no way obviates the lightspeed postulate. It augments the lightspeed postulate with even more postulates, some of which Einstein already knew to be false, but which he needed in order to make his argument for the inertia of energy. Now, this particular derivation of mass-energy equivalence was criticized by many scientists, including Planck, not least because of its reliance on Maxwell's equations. (This derivation has also been assessed as circular reasoning, even by some admirers of Einstein.) In his 1907 paper Einstein felt compelled to apologize for having based his argument on Maxwell's equations, which was unnecessary, and which he already knew to be wrong, but he justified it by saying that he thought the use of Maxwell's equations would lead to reasonable results in the particular cases where he used them. But the point is that it's utterly idiotic to say that Einstein "dropped the 2nd postulate" when he (on these rare occasions) postulated Maxwell's equations. Those equations are then "the 2nd postulate", and they contain the invariant lightspeed postulate (which we already know is sufficient to derive the Lorentz transformation) PLUS many more individual postulates. It's as if you brought a cow, two horses, and three pigs into the barn, and then you claim that you didn't bring a cow into the barn. Please. It is very well known that the principle of relativity, alone, is not sufficient to single out special relativity. Some other postulate is required. Now, it is certainly true that there is a wide choice of possible 2nd postulates to augment the relativity postulate, but they all amount to lightspeed invariance. See, for example, the discussion in Rindler. This is all very old hat, and goes all the way back to the early days of relativity, with the likes of Ignatowsky arguing with Ehrenfest. I urge you to acquaint yourself with the literature on this subject.63.24.124.104 (talk) 04:04, 19 February 2008 (UTC)

Once again an irrelevant response that shows your total inability to see both sides of an argument. Again, it doesn't alter the fact that Einstein used Maxwell's equations to derive c, and, for this reason, dropped the 2nd postulate in his 2nd paper. What he did towards the end of his life doesn't alter the historical record for 1905, nor does it diminish the utility of understanding the origins and motivation of SR (or any subject) as a modern day pedagogical tool. --Michael C. Price talk 08:35, 18 February 2008 (UTC)

Einstein certainly claimed in the 27th September addendum to his 1905 paper that he drew heavily upon Maxwell's equations. And he did state in that paper that the constancy of the speed of light was inherent in Maxwell's equations.
But it is a matter of opinion as to whether the content of Maxwell's original works bears any relationship whatsoever to Einstein's works. Nobody having studied Maxwell's original works would see the slightest similarity between what he was doing and what Einstein was doing. It is likley that Einstein misunderstood Maxwell's equations. David Tombe (talk) 11:39, 8 June 2008 (UTC)
I hardly think that it is a matter of opinion as to whether the content of Maxwell's original works bears any relationship whatsoever to Einstein's works. Any relationship? As for It is likley that Einstein misunderstood Maxwell's equations. You must be kidding or very ill-informed. Please enlighten us as to how "Einstein misunderstood Maxwell's equations". --Michael C. Price talk 14:06, 8 June 2008 (UTC)

Michael, there is not the remotest similarity between Maxwell's work and Einstein's work.

I agree with you that Einstein claimed to have drawn on the so-called Maxwell-Hertz equations. But in what respect? It is true that the E = mc^2 can be derived from a lesser known equation by Maxwell that is connected with radiation pressure. But that radiation pressure equation never appears in either modern sets of Maxwell's equations or in Maxwell's original eight equations.

Maybe it is the radiation pressure equation that Einstein is referring to but he doesn't make that clear.

At any rate, there is nothing at all in Maxwell's original works that says that the speed of light is a universal constant.

I had always assumed that the constancy of the speed of light was an Einstein idea which he derived from the Michelson-Morley experiment.

Perhaps you would like to tell me what exactly Einstein saw in Maxwell's equations that led him to his theory of relativity. For Maxwell, the speed of light was the mach number in a sea of elastic molecular vortices and it never possessed any of the special relativity properties that Einstein later attributed to it. David Tombe (talk) 09:53, 9 June 2008 (UTC)

Perhaps you would like to tell me what exactly Einstein saw in Maxwell's equations that led him to his theory of relativity. Again, I quote Einstein 1905:

::With these principles (The principle of the constancy of the velocity of light used there is of course contained in Maxwell's equations.) as my basis I deduced .....

BTW Einstein probably never heard of the Michelson-Morley experiment at the time.--Michael C. Price talk 10:38, 9 June 2008 (UTC)

Michael, we had already agreed that Einstein said that in his 1905 paper. But it just goes to show how little Einstein understood Maxwell's equations. because they don't imply the universal constancy of the speed of light. If you read Maxwell's papers, you will see that he calculated that speed using Newton's eqation for the speed of sound in connection with an elastic medium. He saw the speed of light as the mach number for that medium measured at a stationary point in that medium. David Tombe (talk) 11:39, 9 June 2008 (UTC)

David, Maxwell's interpretation of his equations are irrelevant: we are talking about Einstein's interpretation. No one disputes that the two interpretations are different. See also DH's comments below. --Michael C. Price talk 12:16, 9 June 2008 (UTC)
Regarding to some discussions above: Einstein's 2nd postulate and his view of Maxwell's equations was based on Lorentz's formulation of Maxwell's theory (the so called "Maxwell-Lorentz equations").
  1. Einstein said in his 1909-paper: "According to Lorentz's theory, if a light beam propagates through space, it does so with a speed c in the resting frame K of the ether, independently of the state of motion of the emitting object. Let's call this the invariance of the speed of light principle."
  2. And in his 1912-paper Einstein wrote: "It is widely known that based on the principle of relativity alone a theory of transformation laws of space and time can not be established. It is known that this is connected with the relativity of "simultaneity" and "the shape of moving bodies". To fill this gap, I borrowed from H.A. Lorentz's stationary light-ether theory the principle of constancy of the speed of light, which like the relativity principle is a physical condition that is only justified by the pertinent experience (experiments by Fizeau, Rowland, etc.)."
  3. And in his nobel lecture (1921), he said: "The special theory of relativity is an adaptation of physical principles to Maxwell-Lorentz electrodynamics...From Maxwell-Lorentz electrodynamics it takes the postulate of invariance of the velocity of light in a vacuum (light principle).
See also History of special relativity and the works of Holton, Miller, Stachel...--D.H (talk) 12:01, 9 June 2008 (UTC)

Well of course that would make alot more sense. In other words Einstein wasn't referring to Maxwell's original works at all. Fair enough. We all knew all along that Einstein was influenced by Lorentz, and the connection is indeed clear.

It still however leaves a mystery as to what he meant by the Maxwell-Hertz equations in the 27th Sept. Addendum to his 1905 paper. The only Maxwell equation that could possibly be relevant to E = mc^2 is Maxwell's radiation pressure equation which never appears alongside Maxwell's equations. David Tombe (talk) 13:10, 9 June 2008 (UTC)

Einstein talked about "Maxwell-Hertz equations for empty space together with the Maxwellian expression for the electromagnetic energy of space". Those things were discussed in §§ 6-8 in the electrodynamics paper. BTW: As shown by Miller (1981), Einstein took many expression from Max Abraham, who was the first to use the terms "Maxwell-Hertz" and "Maxwell-Lorentz" equations, or "longitudinal" and "transverse" mass.--D.H (talk) 15:29, 9 June 2008 (UTC)

But basically Einstein doesn't appear to have had any direct knowledge of Maxwell's actual works. He seems to have worked on other people's developments of Maxwell's works. David Tombe (talk) 16:25, 9 June 2008 (UTC)

So when Einstein said "The principle of the constancy of the velocity of light used there is of course contained in Maxwell's equations." he was just talking through his arse, right? --Michael C. Price talk 16:31, 9 June 2008 (UTC)

@David Tombe: Holton (1973, 1988) points out that August Föppl's (1894) book on electrodynmics was Einstein's most important source for Maxwell's theory. Föppl presented Maxwell's theory in the formulation of Heaviside and Hertz and discussed the important moving magnet and conductor problem. Later, other possible sources for (variations) of Maxwell's theory were some papers of Boltzmann, Helmholtz, Drude, Lorentz, Abraham. So there were many different versions of "Maxwell's" theory - at the end Lorentz's formulation was the winner. ;-) --D.H (talk) 16:55, 9 June 2008 (UTC)

And Heaviside's. Don't we use Lorentz–Heaviside units today? My understanding is these were just different formulations of the same theory.--Michael C. Price talk 17:51, 9 June 2008 (UTC)
The key point here is that Maxwell's original works did not imply that the speed of light is constant. If you look at Maxwell's 1865 paper A Dynamical Theory of the Electromagnetic Field you will see how he derived the electromagnetic wave equation. He specifically dropped the vXH term from his electromotive force equation because he was referencing the wave from a fixed point in his dielectric aether. Hence his speed of light was very much on the same lines as the speed of sound. It was based on the density and transverse elasticity of a physical medium.
In fact, in his 1861 paper, he actually used Newton's equation of the speed of sound to calculate the speed of light. There are links to all of these papers available from some of the wiki articles.
One thing is sure, and that is that if Einstein thought that Maxwell's equations implied the constancy of the speed of light as is understood in special relativity, then Einstein was very much mistaken.
But we are not really sure exactly what Einstein was talking about when he refers to the Maxwell-Hertz equations. It certainly can't have been Maxwell's original works. David Tombe (talk) 08:18, 10 June 2008 (UTC)
@David Tombe: Einstein's thoughts on Maxwell's theory were presumably based on the descriptions by Föppl, Hertz, Abraham etc.. Whether Einstein read Maxwell's original papers or not, I don't know. But I don't think the question is very important. --D.H (talk) 10:05, 10 June 2008 (UTC)
Agreed. They were all singing from the same hymn sheet. --Michael C. Price talk 16:18, 10 June 2008 (UTC)
@MichaelCPrice: Both Heaviside and Hertz (1889, 1890) assumed the existence of a fully dragged ether, therefore they failed to explain the optics and electrodynamics of moving bodies. This was done by Lorentz (1892, 1895). So their formulations of Maxwell's theory were similar, but not the same.--D.H (talk) 10:05, 10 June 2008 (UTC)

It's only important in so much as Einstein's references to the Maxwell-Hertz equations and their supposed connection with the constancy of the speed of light gives the false impression that Maxwell's equations imply that the speed of light is constant in the relativistic sense.

Maxwell's original equations certainly don't imply anything of the sort. However the constancy of the speed of light might indeed be inferred from the Heaviside versions since Heavisde dropped the vXH term and wrote the equations in partial time derivative format. The Heaviside versions are what we get in modern textbooks. If we look at them in isolation, we have equations involving the speed of light that seem to be frame independent, and so one might be forgiven for drawing the conclusion that Maxwell's equations imply the constancy of the speed of light. That might be what Einstein was using. I have read somewhere recently that the Maxwell-Hertz equations is the name that Einstein gave to the Heaviside versions.

At any rate, we wouldn't be able to draw that conclusion about the constancy of the speed of light if we traced back to the origins of the equations. They are based on experiments which took place in the laboratory frame and they originally contained a convective vXH term. Heaviside removed the convective vXH term which is why nowadays we have to supplemnt Maxwell's equations with the Lorentz force in order to get the vXH term.

I would guess that the material that Einstein drew on mostly was Lorentz's material. I'd be very surprised if Einstein hadn't heard about Michelson-Morley. I would say it was probably a combination of watching how Lorentz was struggling with Michelson-Morley, and Einstein's own mis-reading of the Heaviside verisons of Maxwell's equations that lead him to his postulate about the universal constancy of the speed of light.David Tombe (talk) 16:18, 10 June 2008 (UTC)

I don't think there was a "misreading". That the speed of light is constant in all reference frames was a direct consequence of Lorentz ether theory, which was already noted by Poincaré in 1904. However, while Lorentz and Poincaré arrived at this result via a constructive approach, Einstein used this as a postulate and derived the rest of the theory in a remarkable easy way. --D.H (talk) 17:05, 10 June 2008 (UTC)
I agree; no "misreading" by Einstein. --Michael C. Price talk 18:52, 10 June 2008 (UTC)

We can't ascertain whether or not there was any "misreading" by Einstein until we know exactly what he was reading. David Tombe (talk) 14:56, 17 July 2008 (UTC)

You were the one that accused Einstein of "mis-reading", not us. --Michael C. Price talk 22:35, 17 July 2008 (UTC)

Michael, we need to know what Einstein meant by the Maxwell-Hertz equations. In his 1905 paper, he claims that the Maxwell-Hertz equations imply that the speed of light is a universal constant.

All I know for certain is that Maxwell's original equations as are found in Maxwell's original works, do not imply anything of the sort.

So until we get see see exactly what Einstein was talking about when he referred to the Maxwell-Hertz equations, we cannot take the matter any further. David Tombe (talk) 10:27, 18 July 2008 (UTC)

Einstein disagrees with you since he said (1905) "The principle of the constancy of the velocity of light is of course contained in Maxwell's equations." . So if you maintain your claim then you are the one claiming that Einstein is misreading "Maxwell equations", not us.--Michael C. Price talk 11:05, 18 July 2008 (UTC)
In the preface to his 1905 paper, Einstein said "These two postulates suffice for the attainment of a simple and consistent theory of the electrodynamics of moving bodies based on Maxwell's theory for stationary bodies." (emphasis added). He was not working with the full Maxwell theory. He was just using the special case when the medium is not moving. JRSpriggs (talk) 13:19, 18 July 2008 (UTC)
Hmmm.... well, that not what he said, though. He said the bodies weren't moving, not the medium; i.e. he was starting from the theory of electrostatics and trying to derive a theory of electrodynamics (i.e. what we now call electromagnetism). As he later said: What lead me more or less directly to the special theory of relativity was the conviction that the electromotive force acting on a body in motion in a magnetic field was nothing else but an electric field. (Letter to the Michelson Commemorative Meeting of the Cleveland Physics Society as quoted by R.S.Shankland, Am J Phys 32, 16 (1964), p35, republished in A P French, Special Relativity, ISBN 0177710756).--Michael C. Price talk 14:25, 18 July 2008 (UTC)

I would say that Einstein has totally misinterpreted Maxwell. As regards the electromotive force acting on a body in motion in a magnetic field, Maxwell deals with that at equation (5) in his 1861 paper which is available on-line. The third and fourth terms on the right hand side of this equation are the relevant terms. In the discussion, Maxwell explains this force in terms of centrifugal aether pressure coming from the equatorial plane of his solenoidally aligned molecular vortices.

Interestingly, I was just about to bring up this very point with Ancheta Wis on the talk pages of Maxwell's equations. Ancheta Wis has told me that Maxwell considered the electric motor to be the greatest invention of the 19th century. Ancheta then went on to tell me that the electric motor works on the principle of the Lorentz force and not Faraday's law.

In Maxwell's 1861 paper, equation (77) corresponds to the Lorentz force and it contains a vXH term. The parts of equation (5) that are relevant to the electric motor is also a vXH term. In equation (5), Maxwell attributes vXH to centrifugal force. However, in equation (77) it is almost certainly a Coriolis force.

At any rate, the curl of vXH leads directly to the convective term in Faraday's law of electromagnetic induction. Ancheta Wis has simply failed to see how Faraday's law can be extended to cater for electric motors in the zero-curl scenario.

Einstein on the other hand appears to have totally failed to grasp anything that Maxwell said at all. David Tombe (talk) 17:00, 18 July 2008 (UTC)

Dear David, please do not interpret the lack of any substantive response as indicative of agreement in any form or to any degree. --Michael C. Price talk 18:12, 18 July 2008 (UTC)

Michael, Maxwell and Einstein weren't even remotely working along the same lines. If Einstein is claiming to have drawn on Maxwell's work as an inspiration for his theories of relativity, then he clearly didn't have the slightest grasp of what Maxwell was saying. David Tombe (talk) 11:51, 19 July 2008 (UTC)

  1. ^ Einstein dropped the second postulate in his second 1905 relativity paper noting that "The principle of the constancy of the velocity of light is of course contained in Maxwell's equations."
  2. ^ In a letter to Carl Seelig in 1955, Einstein wrote "The new feature of [the 1905 relativity theory] was the realization of the fact that the bearing of the Lorentz transformation transcended its connection with Maxwell's equations and was concerned with the nature of space and time in general. A further new result was that the "Lorentz invariance" is a general condition for any physical theory. This was for me of particular importance because I had already previously found that Maxwell's theory did not account for the micro-structure of radiation and could therefore have no general validity."