Talk:Postulates of special relativity

I edited the "Postulates of special relativity" after reading this article on PhysOrg.com

http://www.physorg.com/news11829.html

One of the points that Baierlein makes, is that relativity is generally taught using a version of the second postulate which is far less intuitively plausible than the the second postulate as originally formulated by Einstein.

--- —Preceding unsigned comment added by 67.163.106.133 (talk • contribs)

User:Der alte Hexenmeister

It seems that Der alte Hexenmeister (talk · contribs) may be the person known on UseNet newsgroups by such handles as Androcles and Hexenmeister (google on this handles with group:sci.physics.relativity). The first edits of this new WP user unfortunately violated a number of policies; I just noted some of the violations on his user talk page. Please help us monitor to make sure he follows our behavioral rules in future.---CH 04:12, 15 June 2006 (UTC)

==Enormousdude== The repeated edits by Enormousdude can reasonably be considered vandalism and should be reverted without worrying about WP:3RR. (in my opinion) Gnixon 19:18, 14 April 2007 (UTC)

Unencyclopedic paragraph removed

“ Most current textbooks mistakenly include a major derived result, that the speed of light is the same to all inertial observers, as part of the second postulate. A careful reading of Einstein's 1905 paper on this subject shows that, in fact, he made no such assumption. Many textbooks also overlook that the isotropy of the one-way speed of light was introduced by definition and not as postulate. ”

News flash: Most textbooks are wrong, says unsourced Wikipedia article. Please save this kind of opinion for your blogs. Tim Shuba 15:28, 9 October 2007 (UTC)

Bogus Section on Alternate Derivations

The so-called "sourced" section blatently mis-represents the cited sources, none of which say what this section claims. I'll be happy to provide as many solid references as anyone wants for my suggested revision. And my references will actually support what my suggested words say. This is not an obscure issue. Scholars have studied the various possible derivations of special relativity very intensively. Whole books have been written on this specific subject. There is a truly huge literature on this subject. It ALL contradicts the bogus version of this section. No reputable scholar misunderstands the situation in the way presented in the bogus section. Not to mention the fact that the bogus version is self-evident nonsense. It basically says "X" follows logically from "not X". It is a novel narrative and original research based on a Usenet myth from sci.physics.relativity. It doesn't belong in Wikipedia. Lumpy27 (talk) 19:06, 8 January 2008 (UTC)

The section has been here for a while (January 2007) and it is sourced, so whatever you have in mind, in order to remove it or replace it, you will indeed have to provide sufficient counter-sources and/or at least reach sufficient concensus here. I haven't personally checked the first 3 sources, but the first 2 sources are not new. I merely added a 4th source. Have you checked it?

By the way, you'll notice that the section was moved up by Ems57fcva. More history: here and this remark on the special relativity talk page.

If you don't mind, I'd really like to see some more comments on this.

Cheers, DVdm (talk) 19:32, 8 January 2008 (UTC)

Added 5th source (from Morin's book) - See Google Scholar and result. DVdm (talk) 20:26, 8 January 2008 (UTC)

Please take a closer look at the "source" you just added. First it describes how special relativity is based on the classic two postulates. Then it adds the following remark:

"Remark: Given the second postulate, you might wonder if we even need the first. If all inertial frames are equivalent, shouldn't the speed of light be the same in any frame? Well, no. For all we know, light might behave like a baseball. A baseball certainly doesn't have the same speed with respect to different frames, and this doesn't ruin the equivalence of the frames. [In other words, we could have Galilean relativity, not special relativity, just as my proposed words pointed out and you deleted.] It turns out (see Section 11.10) that nearly all of special relativity can be derived by invoking only the second postulate. The first postulate simply fills in the last bit of necessary info by stating that something has the same finite speed in every frame. It's actually not important that this thing happens to be light. It could be mashed potatoes or something else (well, it has to be massless, as we'll see in Chapter 12, so they'd have to be massless potatoes, but whatever), and the theory would come out the same. So to be a little more minimalistic, it's sufficient to state the first postulate as, 'There is something that has the same speed in any inertial frame." It just so happens that in our universe this thing is what allows us to see."

So, your "reference" actually says the opposite of what you claim. The above words say the relativity postulate is NOT sufficient to derive special relativity. It very explicitly says this. (Note the words "Well, no".) If you read this reference (or any of the others, or any of the vast literature on this subject, or if you just think about it for 5 seconds), you will see that the current article is contradicted by all the references it cites, and it makes no sense, and is self-evidently wrong. All the references acknowledge that relativity by itself is NOT sufficient, and that another postulate is needed in order to single out special relativity from Galilean or Euclidean relativity. And of course there are no massless mashed potatoes, so the only thing that can have invariant speed is something massless. The point is that the invariant massless-speed postulate (or something equivalent to it) is indispensible, as your own reference clearly explains.

The one cited reference that makes statements similar to what is said in the article also happens to be the un-vetted preprint from a quasi-crank, that shouldn't be listed here anyway. But even THAT reference (if you read it carefully) admits that its claim is false, because it just notes that we can infer the transformation up to a constant that determines whether its Galilean or Minkowskian (as if this wasn't thoroughly understood by 1908), and then admits that another assumption is needed to determine the constant, which of course is presicely what the lightspeed postulate does... the very thing it claims is not needed... while simultaneously admitting that it is needed. This is why such preprints never get published. Pure idiocy. And setting that one aside, all the other references flatly contradict the novel narrative that is present in the article. This crackpot stuff doesn't belong is Wikipedia. Lumpy27 (talk) 21:11, 8 January 2008 (UTC)

• I have no access to the other refs, so I cannot comment, but in Morin's case, I interpret the entire section as follows:

Keeping common the first postulate and the (originally) tacitly assumed homogeneity, isotropy, etc..., Einstein's second postulate is the invariance of the speed of light. In the other derivations, in order to arrive at the same theory, one takes the approach of using a different second postulate (an unspecified but non-infinite maximum speed, which immediately rules out Galilean relativity), to produce some theory that we could call "LessSpecial relativity. This theory is conceptually broader than (let's call it) "NormalSpecial relativity". It goes over into it when we assume light speed to be that maximum speed. Now, whether we call the latter assumption "another postulate" or not, we have in effect an "alternate derivation" of special relativity, with a different second postulate, plus that extra postulate, expressed by Morin in terms of: "... then you can simply postulate the existence of something that moves with this limiting speed." We can of course also immediately decide to call that broader theory just "Special relativity", and conceptually provisionally (sic!) use light speed for the parameter until some future experiment establishes a lower limit for the anisotropy of light speed, for indeed we only have some upper limits for it. Again, when we take this approach, we have an "alternate derivation" of special relativity.

I don't think that this is "crackpot stuff that doesn't belong in Wikipedia".

• You have replaced a properly sourced section (perhaps with the exception of the unpublished Certik ref) with a statement expressing a personal non-neutral point of view containing an unsourced sythesis of a (de-facto disappeared) neutral section explaining how some authors look at the postulates of the theory. As far as I have understood, this would qualify as original research, and it does not belong in Wikipedia.
• So I have removed your statement and reinserted the original section without the Certik ref. I think that the section contains sourced and verifiable facts - Note the phrases in the original section like "derive the structure of special relativity" and "along with some assumptions", and the differences between the original and the new one.

Let's try to find consensus about this. Cheers, DVdm (talk) 08:59, 9 January 2008 (UTC)

The issue here is the statement in your versions of the paragraph

several authors have shown that it is possible to derive the structure of special relativity from the principle of relativity, along with some assumptions about the homogeneity, isotropy, memorylessness, reciprocity of space and time.

That statement is contradicted not only by all the references cited in support of it, but also by your own statements above. You have acknowledged that the principle of relativity (plus homogeneity, etc) is NOT sufficient, even to derive the generic version (what you call Less special relativity), let alone the actual theory of special relativity. Please note that the question here is not whether valid alternative derivations and sets of postulates exist. Of course they do (although none of them are mentioned in this article that is supposedly devoted to them). The question is whether your version of the section is correct (per reputable sources) in claiming that special relativity follows from the principle of relativity (plus homogeneity, etc) alone. This is what your version claims, and it is a false claim, and the references you have cited to support it actually contradict it, and in fact your own reasoning (above) contradicts it. As I said before, I'll be happy to supply a dozen or more solid references from the most reputable sources (in addition to those already cited) in support of the correct and rational version. I think you should stop reverting to the incorrect and irrational and unsourced version. (I call it unsourced, but it's actually WORSE than unsourced... it is MIS-sourced, i.e., the cited references in your version directly contradict what your version says. Also note that I call it "your version" because you are the only one defending it and rejecting all attempts to correct it.)Lumpy27 (talk) 15:41, 9 January 2008 (UTC)

As I said, I only have access to Morin's book. I think you still didn't get my point, but I'm not going to bother trying to explain again.

So, what we have now:

1. A section trimmed down to essentially nothing that can't be found in the main article.
2. A section with a (-excuse my Flemish-) vaguely sourced soapbox statement about a section that used to be there, attempting to disprove a point that isn't even there anymore. This definitely does not belong in Wikipedia. And it looks really silly :-)
3. A section which, like you hinted before, is unsourced and extremely poorly written.

So, as far as I'm concerned, you can just as well delete the entire article now. I will wholehaertedly support a delete request. If you don't go for article deletion, I suggest you (1) put something worthwhile in the first section, (2) throw away the second section, and (3) start working on the 3rd section to make it Wikigood.

Nice chat :-) Cheers, DVdm (talk) 17:51, 9 January 2008 (UTC)

I would like to revive the discussion about this section. It still seems to imply that special relativity can be derived from the relativity postulate alone:

The numerical value of the parameter in these transformations can then be determined by experiment, just as the numerical values of the parameter pair c and the Vacuum permittivity are left to be determined by experiment even when using Einstein's original postulates.

Reference [9] "Inertial frames without the relativity principle" is not about deriving relativity without the light postulate, but rather an exploration without the relativity postulate. Additionaly it contradicts the claim of the section:

Ever since the work of von Ignatowsky circa 1910 it has been known (if not always widely appreciated) that the relativity principle, combined with the basic and fundamental physical assumptions of locality, linearity, and isotropy, leads almost uniquely to either the Lorentz transformations of special relativity or to Galileo’s transformations of classical Newtonian mechanics.

Let's either remove the whole section as it does not present a complete alternative derivation of special relativity, or edit the current text by removing any misleading claims. We should at least clarify the necessity of the second postulate: uniquely select the right type of relativity from the ones allowed by the relativity postulate: euclidean, galilean and lorentzian. — Preceding unsigned comment added by Real Pattern (talk • contribs) 17:33, 14 March 2021 (UTC)

Please sign all your talk page messages with four tildes (~~~~) — See Help:Using talk pages. Thanks.

I have re-added the Morin reference, mentioned above ([1]). I'll see if I can find proper sourcing for the remaining part. Otherwise we might have to remove some of it. - DVdm (talk) 21:55, 14 March 2021 (UTC)

Thanks for adding [1]. This source as well clearly states that without the light postulate we end up with either the galilean transformation or the lorentzian transformation:

You just have to say whether V is finite or infinite, that is, whether the universe is Lorentzian or Galilean. (p.549)

The light postulate selects the Lorentzian transformation. Real Pattern (talk) 23:20, 14 March 2021 (UTC)

Moreover, see Wiki section [2], addressing the same topic. Real Pattern (talk) 23:43, 14 March 2021 (UTC)

Thanks for signing. Please indent the messages as outlined in wp:THREAD and wp:INDENT — See Help:Using talk pages. Thanks.

Ha yes, indeed, History of special relativity#Lorentz transformation without second postulate addresses the same topic. Good to know . - DVdm (talk) 23:53, 14 March 2021 (UTC)

Another Proposal to Delete this Article?

After reviewing the rest of this article, I see that the whole thing is pretty bad. It seems to be just someone's (unfortunately misguided) summary of special relativity. When you get into the "mathematical defintion of the postulates" section, it just goes completely off the rails, making all kinds of statements that are unsourced (and, incidentally, wrong). Now, we could go through and correct everything, but isn't this already covered in one or more of the numerous other articles on special relativity? Shouldn't the "postulates of special relativity" just be part of the article on "special relativity"?

I see that this article was nominated for deletion about 8 months ago, and the decision was "keep". I wonder if that decision should be re-considered. Maybe I should go read the discussion related to that decision... but I fear the discussion was likely dominated by whoever concocted this misguided article in the first place.

In any case, I definitely think the article must either be deleted or else drastically re-written to eliminate all the mis-statements. Lumpy27 (talk) 05:21, 9 January 2008 (UTC)

Yes, perhaps you could go read the discussion. It wasn't much of a discussion to begin with, but you can always propose to delete the article again, or make it better. Cheers, DVdm (talk) 09:07, 9 January 2008 (UTC)

The article suffers from severe issues; sources are only primary (there should be no problem in finding secondary sources for such a topic!); it is frequently unclear what is derived from what. The paragraph talking about pseudo-Riemannian manifolds is confusing rather than clarifying. I am not a physics myself, and it would take a very long time for me to improve the article, but everyone having a bit of familiarity with special relativity can understand that the article is unclear, incomplete, and partly incorrect. (of course, it should be rewritten, not deleted!)78.15.179.105 (talk) 21:13, 29 July 2015 (UTC)

The two standard postulates are insufficient ... revision, with deeper background and refs

Some discussion of the conventional two-postulate narrative, with sources provided (mostly Einstein). The usual two postulates (plus some reasonable unspoken assumptions, such as classical continuity and wave-compatibility) are not enough to uniquely specify the SR equations: Einstein's derivation also assumes that the relativistic lightbeam geometry derived specifically for empty space (i.e. Minkowski spacetime) still applies when space is not empty. The 1905 paper fails to "flag up" this third (quite important) dependency.

If the presence and relative motion of matter affects the propagation of light in any way, we get a divergence of equations: SR as a "null theory" that only holds for truly empty space, and some other set of different equations that describe signals sent between real lumps of geometry-complicating moving matter. In that scenario, SR is valid geometry but not correct inertial physics.

A historical counter-example to Einstein's derivation would seem to be something like Hertz' earlier (1890) theory of the electrodynamics of moving bodies, which supports both relativity and local c-constancy (for physical observers). Einstein commented that the Hertz theory was logically valid, so he seems to have been aware that his two-postulate narrative was not "airtight", and that at least one other system was available.

With just the two standard postulates, SR risks being a theory of observation that only holds in the absence of physical observers: Some references to this possibility (mainly Wheeler and Einstein) are given. ErkDemon (talk) 23:56, 27 February 2023 (UTC)

Merge

I suggest merging Postulates of special relativity with Alternative formulations of special relativity. The 2-postulate formulation is just one of several. We don't know two articles to say that. Roger (talk) 23:50, 7 July 2023 (UTC)