Talk:Length contraction

Physical?

The first line of the article refers to a 'physical' effect. What is this intended to mean?

Also, 'according to Hendrik Lorentz', should be part of the history. Martin Hogbin (talk) 10:07, 6 October 2013 (UTC)

Thanks. The term "physical" (which was used in the article for years) can lead to misunderstandings, since in relativity it's only a geometric effect. --D.H (talk) 11:36, 6 October 2013 (UTC)

Evidently the above phrase "only a geometric effect" (meant by me in terms of "frame dependent" or "coordinate dependent") leads to misunderstandings as well. Anyway, whatever word one chooses, the article explains that it is a frame dependent effect based on the Lorentz transformation and certain operational procedures, as described in standard mainstream textbooks. So it's more secure to follow the textbook formulas and to avoid philosophical talking about the meaning of words (physical, geometrical, apparent, real), unless sourced as per WP:Sources and WP:undue. This effect expresses itself in a frame dependent manner in areas such as relativistic electromagnetism (contraction of the Coulomb field); longer travel path of moving muons (in the other frame it's due to time dilation); contracted heavy ions in motion; increased ionization capability of charged particles in motion due to contraction of the Coulomb field; contraction is consistent with the negative result of the Michelson-Morley experiment in relatively moving frames; contraction is consistent with the Ehrenfest rotating disc as viewed in the laboratory frame (in the co-rotating frame general relativity implies non-euclidean geometry in presence of a pseudo-gravitational field) etc. --D.H (talk) 07:53, 16 October 2013 (UTC)

I think you are correct in concluding that we should avoid saying, 'only a geometric effect' as is does lead to misunderstandings, mainly because people will assume a 3+1 geometry rather than 4D spacetime. We could though add a bit more to the 'Reality of length contraction' section. I will start a new section here on that. Martin Hogbin (talk) 08:34, 16 October 2013 (UTC)

The "Reality of Length Contraction" section ends with this quote: "John Bell and Harvey Brown have argued that there are some advantages to explaining relativity in a more constructive way, with the length contraction being caused by electromagnetic forces pulling atoms closer together." This perpetuates the misunderstandings by "explaining relativity in a more constructive way" as physical compression physically shortening objects. Also this Wiki reference to the Ehrenfest paradox insists that there are no rigid bodies in relativity... more of the argument for physical contraction, leading to more misunderstanding: “Another famous paradox is the Ehrenfest paradox, which proves that the concept of rigid bodies is not compatible with relativity.” Length contraction can not have it both ways,..."only a geometric effect" and a physical shortening of objects (and distances between them.)This basic contradiction in presentation of length contraction is in dire need of "disambiguation." LCcritic (talk) 18:23, 10 October 2013 (UTC)

Nowadays (i.e. since a century or so), "physical" and "real" (and even "geometrically") all mean "operationally and reproducibly measurable". Anything beyond that seems to have become what we could call arm-chair philosophy, i.e. wasting one's time on the usage of words. Just like velocity and energy, length is a coordinate dependent property. That does not make it "unphysical" or "unreal" or "merely geometrical". - DVdm (talk) 21:27, 10 October 2013 (UTC)

Maybe Bell and Brown are misleading with their arm-chair philosopher. I have no quarrel with either of you. I put that sentence in because I thought that it is useful to have a reference to how some credible sources have discussed the reality of the contraction. Roger (talk) 23:17, 10 October 2013 (UTC)

Many modern introductory text books have a section where they address the question of whether the Lorentz contraction and other effects of relativity are 'real' or 'physical'. The facts are fairly clear; lengths of objects in relatively moving frames do everything they should do if they were contracted, nuclear bombs really do make big bangs, and the GPS system continues to work. No one argues that a rod experiences any effect in its own rest frame just because it has been observed from another frame. The days when motion through some aether might be considered responsible for 'really' (whatever that means) making rods get shorter for are long past. Whether you chose to call the effects of relativity, 'real', 'physical', or 'geometrical' is purely a matter of taste and, as DVdm says, only of interest to philosophers. Martin Hogbin (talk) 08:37, 11 October 2013 (UTC)

In reference to: "Reality of length contraction

Another issue that is sometimes discussed concerns the question whether this contraction is "real" or "apparent". However, this problem only stems from terminology, as our common language attributes different meanings to both of them. Yet, whatever terminology is chosen, in physics the measurement and the consequences of length contraction with respect to any reference frame are clearly and unambiguously defined in the way stated above.[15] [15]: “^ See for example Physics FAQ: "People sometimes argue over whether the Lorentz-Fitzgerald contraction is "real" or not... here's a short answer: the contraction can be measured, but the measurement is frame dependent. Whether that makes it "real" or not has more to do with your choice of words than the physics."

The above reflects the *opinion* that whether or not length contraction is "real" or physical is merely a philosophical debate about semantics. If a student of special relativity comes to Wiki looking for an answer with that question in mind, what does he find?: The ultimate ambiguity. I have shown two examples of contradictory Wiki answers. I am new here. Wiki talks a lot about disambiguation, but on this issue, the senior editors delete all attempts at such disambiguation, calling it armchair philosophy. Either physical objects shrink or they don't. If they do, physics is required to provide the physical explanation for it. If not, it must be clearly labeled as an observer-dependent phenomenon, and those differeces in observations and measurements must be distinguished from actual physical changes in the objects observed. LCcritic (talk) 18:40, 12 October 2013 (UTC)

The issue is somewhat confusing. If you have any suggestions for improving the article, please propose them. Roger (talk) 23:08, 12 October 2013 (UTC)

Opinions about possible contradictions in the length contraction concept must be based on reputable sources, (WP:Sources, WP:OR), otherwise they are not relevant for the improvement of the article. If someone wants to make substantial additions, one has to cite such sources. --D.H (talk) 08:19, 13 October 2013 (UTC)

It does not require a "reputable source" to have general, reasonable agreement that, as I said, either physical objects shrink or they don't. Wiki on length contraction remains ambiguous on that, and I already cited examples. I would improve the article on length contraction (if I were so allowed) by prefacing the discussion with clarification of the "physical or not" issue. Martin Hogbin asked for clarification on that, opening this talk page. D.H answered that it was "only a geometric effect." Yet mainstream SR still treats length contraction as a physical effect, the most popular example of which may be the "barn and ladder/pole" example, confusing different measurements from relativistic frames with a physical shortening of the ladder or pole. Shortened distances between bodies in space (as measured by theoretical relativistic frames) is also frequently argued by SR physicts. I need feedback on whether or not I am allowed to disambiguate this issue as a preface to the length contraction section. Must I first reveal my credentials as a philosopher of science specializing in relativity? (I value my anonymity very highly.) Thanks ahead for any feedback offered. LCcritic (talk) 19:54, 14 October 2013 (UTC)

Alas, your "credentials as a philosopher of science specializing in relativity" don't mean much at Wikipedia, so really there is no need to reveal them. One of the pilars of Wikipedia is that contributors' credentials are entirely irrelevant. See wp:reliable sources, wp:primary sources and wp:NOR. If I'm not mistaken, I think that, as someone with impressive credentials, you might be welcome at Citizendium, which, as far I as understood, was created because specialists with relevant credentials were not really welcome to expose their work here. - DVdm (talk) 21:23, 14 October 2013 (UTC)

Thanks but Citizendium is 'off the radar' for anyone searching length contraction, and I am not willing to give my real name and credentials as a critic of length contraction anyway. Seems no one here cares about disambiguating whether physical objects actually, physically shrink or not (in the context of length contraction,) much less sort out the philosophical difference between the realism of things and distances with length independent of all differences in observation and the idealism Einstein's world where there is no "reality" independent of differences in observation. Seems that SR could grant that proper length is valid physical measurement and that relativistic measurement requires the Lorentz transformation to achieve the correct and valid value of the length of objects and distances... rather than insisting that all frames yield equally valid measurements of length. I would give it a try (disambiguation) if there were any indication that such a try would not be dismissed and deleted out of hand as irrelevant philosophy. Still open to feedback on that. LCcritic (talk) 19:34, 15 October 2013 (UTC)

I do not understand your point. If you are an expert on this subject, then you know that more than one point of view is possible. I added a sentence so that readers could learn more about the difference between the views. If you are an expert, then you probably know of a better reference on the subject than the one I put in. If so, please add your reference and propose your clarifications.

You say, "either physical objects shrink or they don't." Well, they do for one observer and not for another. Maybe you prefer to think of it as a geometrical or a physical effect, I cannot tell from your comments. Roger (talk) 20:32, 15 October 2013 (UTC)

LCcritic, again, what you first need are relevant, reliable, mainstream, secondary sources (again, see wp:RS and wp:secondary sources). When you have those, you can propose here to make some change or addition to the article. Then perhaps, if the proposed content is sufficienctly relevant (see wp:DUE) and is not fringe (see wp:FRINGE), we can find some consensus (see wp:CONSENSUS) to get it in the article. That's how Wikipedia works. Good luck. - DVdm (talk) 20:52, 15 October 2013 (UTC)

Expansion/reorganisation of the 'Reality of length contraction' section

I think this section might be reorganised and expanded a little to cover this subject.

For a start I think the sentence about Bell and Brown's thoughts should moved from the end of the section be put into a historical perspective. At the moment this sentence suggests that this topic is of interest to physicists and is still under active discussion. Martin Hogbin (talk) 14:48, 16 October 2013 (UTC)

Yes, go ahead. Not really a topic under relevant active discussion anymore. - DVdm (talk) 15:12, 16 October 2013 (UTC)

I think that you are reading too much into that sentence. Brown is a philosopher, and wrote a well-received book on the subject in 2005. Of course philosophers write lots of books on subjects that are not of interest to most non-philosophers. The issue is discussed in textbooks and students often ask about it. Go ahead and add historical perspective. Roger (talk) 16:12, 16 October 2013 (UTC)

Maybe we need to separate philosophical musing on the subject from the physics. Martin Hogbin (talk) 16:28, 16 October 2013 (UTC)

Maybe an introduction to length contraction in Wiki could include this from “The State of Experimental Evidence for Length Contraction, 2002” by Delbert Larson, (renowned physicist and designer of particle accelerators): Abstract: "The idea that physical objects become shorter as they move is now well established in physical theory. Both the classical theories of Lorentz, Larmor, Fitzgerald and Poincare and the more radical special theory of relativity of Einstein incorporate a physical length contraction into their worldview. However, no direct measurement of length contraction has ever been done..." Conclusion: “As of July, 2002, it is still not proven that a length contraction exists.”

Roger, to clarify as you requested: To my, "Either physical objects shrink or they don't," you said, "Well, they do for one observer and not for another." The whole point of my proposed clarification is to distinguish differences "for one observer" vs "for another observer" (no argument on that) from differences (changing lengths) in physical objects themselves, if any.LCcritic (talk) 19:44, 16 October 2013 (UTC)

I don't think that such an addition would be due (see wp:DUE). After all, no "direct measurement" of you or me falling from a tall building when dropped, has been done either. Conclusion: as of October, 2013, it is still not proven that you or I will fall from a tall building when dropped. So what? If some renowned physicist and designer of particle accelerators would write that in some article, would we put that in our article on gravitation? The entire body of physics is consistent with you or me falling under such circumstances, just like that same body is consistent with length contraction. - DVdm (talk) 20:47, 16 October 2013 (UTC)

I agree. this website shows that Larson is far from being a mainstream physicist. Martin Hogbin (talk) 21:27, 16 October 2013 (UTC)

LCcritic, if you want to contradict a century of physics textbooks, it is going to take more than an off-hand comment cherry-picked from an unpublished rant. The paper says, "By looking at all of the experimental evidence, it is clear that Einstein's relativity is the most in doubt, because of the experimental tests (reference 6) of Bell's Theorem (reference 7)." Most of the paper is an analysis of an experiment that is claimed to be inconclusive. The point you want to make about direct experiment seems to be already made in the section on "Experimental verifications". The point about observer dependence is also made. Roger (talk) 21:42, 16 October 2013 (UTC)

There is still no clarification (disambiguation) on whether length contraction is "only a geometric effect," as D.H said or whether a physical ladder 20 feet long will fit inside a physical barn 10 feet long as claimed by length contraction advocates. The physics of such shrinkage must be clarified if the claim is that physical objects do in fact shrink. It must also apply to a shortened Earth diameter as measured by an approaching relativistic frame. Disambiguate that.LCcritic (talk) 19:48, 17 October 2013 (UTC)

Are you saying that some sort of ladder-barn experiment could disprove the view that the contraction is only a geometrical effect? Has anyone done such an experiment, and proven the standard textbooks wrong? As usual, just cite some reliable sources, as WP will normally stick to what the textbooks say. Roger (talk) 21:38, 17 October 2013 (UTC)

LCcritic, why not read some good relativity text books. They will explain why length contraction is a geometrical effect (in 4-D spacetime) as D.H. says and how a 20 foot long rod will fit into a 10 foot barn. Martin Hogbin (talk) 22:21, 17 October 2013 (UTC)

Roger, I am saying that Wiki on length contraction remains extremely ambiguous as to whether length contraction is a *physical phenomenon* (that physical objects/distances actually physically get shorter as in "thought experiments" such as the popular barn and ladder/pole example)... or whether it is strictly an observer/frame-of-reference dependent *appearance* of contraction. I have studied relativity for many years and understand the 4-D spacetime *model* (Martin Hogbin, please note, regarding your false assumption about my knowledge of relativity.) I endorse the latter, i.e., only *apparent*, not physical contraction. If the former (physical shrinkage) were true, physics would be required to give a physical/mechanical explanation for shrinking physical objects and the distances between them as per "length contracted space" between bodies in space... as measured by theoretical relativistic frames traveling through space. My intent as a critic of physical shrinkage of objects is simply to make the above distinction clear in the Wiki spirit of disambiguation.LCcritic (talk) 17:51, 18 October 2013 (UTC)LCcritic (talk) 19:24, 18 October 2013 (UTC)

So, we are full circle now — see [1]. This can continue for ages, and it's called talk page disruption — see wp:talk page guidelines. DVdm (talk) 18:03, 18 October 2013 (UTC)

I just reviewed those guidelines. Thanks. It has never been my intention to disrupt "talk" on length contraction but rather to clarify exactly what it means in the context of 'actual, physical' versus 'apparent, observer-dependent' contraction. This was made clear above. (Edit: That reply to Roger and to Martin Hogbin was deleted, and I re-inserted to clarify the conversation.) Your reply is consistent with your *opinion* that I am an anti-relativity crank whose clarification/contribution you would like to censor (delete) in defense of your idea of "mainstream" SR. I suggest that your opinion/bias in that regard has no place in a discussion of what Wiki presents as Length Contraction.LCcritic (talk) 18:58, 18 October 2013 (UTC)

LCcritic, the length contraction is ambiguous because more than one view is possible. I tried to make that clear by adding a sentence and reference. You say, "physics would be required to give a physical/mechanical explanation for shrinking physical objects". Yes, physics does precisely that in the constructive view. The point is commonly made in philosophical discussions of relativity, and sometimes also in textbooks. The history of this point goes back to Lorentz and Einstein. If you are really a "philosopher of science specializing in relativity", then you ought to be able to provide a reference that supplements or clarifies the article on this point. Or if you have some other suggestion for improving the article, then please tell us. I really don't see what you want to add, because everything you say is already in the article. Roger (talk) 23:41, 18 October 2013 (UTC)

I want to add an historical perspective on the philosophical basis for the assumption that the length of objects and the distance between objects in space "depends on how you look at it"... in denial of an objective world with intrinsic properties independent of observation. Then I would like to point out that the "view" that the "contracted distances" between atoms in a physical object (varying with velocity), as an "explanation" of physical contraction, has no basis in physics, and that it does not address the issue of applying the principle to contracted distances between objects in space. If these suggestions are still considered simply "disruptions" of Wiki's attempts at disambiguation, then I am done, and Wiki will continue to be ambiguous on length contraction. Thanks anyway. I did my best to clarify the contradictions in this subject as presented.LCcritic (talk) 18:03, 22 October 2013 (UTC)

LCcritic, you are as free to add your wisdom as anyone else. But it is not true that the atomic distance contraction explanation has no basis in physics. There are papers showing it to be a completely legitimate explanation of the length contraction. While the view is out of favor today, it is historically important and deserves to be mentioned as a valid alternate view. If you think that I am wrong, just produce a reliable source that shows that I am wrong. Roger (talk) 04:28, 24 October 2013 (UTC)

Roger, I am familiar with what Bell and Brown "have argued" regarding atomic distance contraction. Please cite the papers showing empirical, experimental verification of same (making it a "valid alternative view"), specifically object length varying with velocity. Another similar "argument" is often applied to distances between objects in space, contracted in proportion to the velocity of observing relativistic frames. Shall Wiki also endorse contraction of distances between stars as theoretically measured from such frames as also "legitimate" according to SR theory? Have you no comment on the philosophy that the length of things depends on how you look at them, as the basis of length contraction? That is the historical basis of SR and the "elephant in the living room" being ignored in the Wiki presentation of length contraction. LCcritic (talk) 18:27, 24 October 2013 (UTC)

LCcritic, the article already has a section on "Experimental verifications". Just read that for the empirical evidence. Yes, the contraction also applies to "distances between objects in space", according to all the textbooks. The article does not mention stars, but yes, SR applies to stars also. You want to say that the "length of things depends on how you look at them"? The very first sentence of the article says that the contraction is measured relative to an observer. The concept is then explained in greater detail. I have no idea what you mean by the "elephant in the living room". If there is some aspect to this subject that is in the textbooks but not in the article, you have not told us. Roger (talk) 20:34, 24 October 2013 (UTC)

(My edit did not copy correctly. Another try:

Roger, From the Experimental Verifications section: "In addition, even in such a non-co-moving frame, direct experimental confirmations of Length contraction are hard to achieve, because at the current state of technology, objects of considerable extension cannot be accelerated to relativistic speeds. And the only objects traveling with the speed required are atomic particles, yet whose spatial extensions are too small to allow a direct measurement of contraction."

There is no empirical evidence cited, as there is none available. It should read, "has never been achieved" rather than merely "hard to achieve." The reference to atomic particles is also wrong, because the "pancaked" effect has been detected in "clouds" of subatomic particles, but that is clearly due to extreme electromagnetic force accelerating them to near lightspeed, and no such force is involved in the hypothetical length contraction on macro-scale, as for instance the distance between stars as theoretically observed from relativistic frames. Furthermore, a different distance between stars would be measured by every possible different velocity of observing frames... which is clearly absurd.

I am sorry that I was not more clear about the statement,"the length of things depends on how you look at them." This denies the objective world with properties independent of observation and insists that length of objects and distances between them depends on the observer. This would have stars varying in distance between them and Earth's diameter varying with all varieties of theoretical observing relativistic frames. This is not objective science but rather a consequence of Einstein's philosophy that there is no objective world, and that all "subjective" perceptions (relativistic frames of reference) are equally valid. That is the "elephant in the living room" being ignored by SR. This philosophy is relativity's version of subjective idealism in denial of realism... an objective world independent of how differently the same object/distance might be measured. SR insists that physical objects shrink, as per the MMX example cited: "Therefore, in the longitudinal direction the interferometer is supposed to be contracted, in order to restore the equality of both travel times in accordance with the negative experimental result(s)." Likewise the 20 foot ladder fitting into a 10 foot barn... a common thought experiment perpetuated by physical length contraction advocates. From the Reality of Length Contraction section: ..." though it 'really' exists, i.e. in such a way that it could be demonstrated in principle by physical means by a non-comoving observer.[16]" "By physical means?" Not so. Finally, from the History section:

"Eventually, Albert Einstein (1905) was the first who completely removed the ad hoc character from the contraction hypothesis, by demonstrating that this contraction was no dynamical effect in the aether, but rather a kinematic effect due to the change in the notions of space, time and simultaneity brought about by special relativity." So contraction must be clarified as not a physical, dynamical phenomenon but an imaginary, conceptual result of the 4-D spacetime model, which depends on SR's "notions of space, time and simultaneity," not a shortening of the actual distances between bodies in space or of the physical lengths of ladders, planet diameters or an arm of the MM apparatus. These criticisms of length contraction deserve to be presented in Wiki's treatment of the subject in service to clarification of the difference between an observed image of an object/distance (varying with observational perspective) and actual physical shrinkage of objects and distances. LCcritic (talk) 18:04, 25 October 2013 (UTC)

LCcritic, re "So contraction must be clarified as not a physical, dynamical phenomenon but an imaginary, conceptual result of the 4-D spacetime model", only if you have a relevant non-fringe wp:reliable source for that. Many times you have been asked to provide such. If you cannot do that, you are wasting everone's —including your own— time here, and, per wp:talk page guidelines, abusing this talk page. Please stop. - DVdm (talk) 18:18, 25 October 2013 (UTC)

LCcritic, you say that the length contraction is not physical. Then you contradict yourself by saying that the pancaked ion effect "is clearly due to extreme electromagnetic force". Then you are wrong again by saying "no such force is involved in the hypothetical length contraction on macro-scale", because that same electromagnetic force applies to the rigidity of macro objects. You are also quite wrong when you say that the objective world is denied, as Minkowski space is the objective world. I have wasted my time on you because I thought that you would provide some useful references to philosophical or interpretational views. You have not. Roger (talk) 19:16, 25 October 2013 (UTC)

Roger, I don't think we should point out contradictions in their analysis. Unless they produce a solid source backed article change proposal, I think it's best to just stop responding. I have put a second level chat warning on their talk page. - DVdm (talk) 20:09, 25 October 2013 (UTC)

Apparently I have misunderstood the Wiki guidelines. No reputable encyclopedia would allow a presentation on how modern science theorizes that Earth's diameter physically shrinks or that stars move closer together as a result of being observed and measured from various relativistic frames of reference. So as a philosopher of science with a focus on relativity, I have suggested several changes in the presentation on length contraction in order to point out such nonsense from a philosophical perspective. These suggestions have been disregarded in the same way that science forums ban all critics of SR, as if the constant speed of light requires that physical objects shrink as well as the distances between stars, planets and all objects in space... depending on how each possible frame might see them. (This is just wrong.) This does not serve better understanding of relativity. At least such a presentation should include such a philosophical perspective as I have tried and failed to present here. I'm done. DVdm, Please do not delete this final note to the editors of length contraction here just because you personally think I am a crank. (I was a well respected professor of the philosophy of science.) Such censorship has no place in science. (Ps: There is no evidence of length contraction on macro-scale and no explanation for it in physics. Future... theoretical fast moving frames traveling through space can never make massive bodies move closer together.... or planets shrink... in the direction of the observer's travel, of course... so shrunken differently "for each observer." Such absolute nonsense!) LCcritic (talk) 21:03, 25 October 2013 (UTC)

Yes, you have misunderstood the Wiki guidelines. Speakers' corner is over here. - DVdm (talk) 21:07, 25 October 2013 (UTC)

Philosophy

I have removed the sentence on the philosophical musings of Bell and Harvey because I think it is inappropriate in a physics article (even though Bell was a physicist).

If any editor wants to add it back I suggest that we start a 'Philosophy' section where this unclear and isolated sentence can be better presented. Martin Hogbin (talk) 08:35, 26 October 2013 (UTC)

Agree with the removal per wp:UNDUE, and I don't think such a separate section would be wp:DUE. - DVdm (talk) 08:38, 26 October 2013 (UTC)

I disagree. Those musings directly address the subject of the section, which is on "Reality of length contraction". It is mentioned in historical and textbook accounts of relativity. It is a common source of confusion. Just look at this Talk page. The issue is not just philosophical, as physical arguments are given. I favor reinstating the sentence. Roger (talk) 21:35, 26 October 2013 (UTC)

John Bell and Harvey Brown have argued that there are some advantages to explaining relativity in a more constructive way, with the length contraction being caused by electromagnetic forces pulling atoms closer together. [2]

Physicist no longer discuss this issue. There is no experimental way to tell the difference.

If we are going to add philosophical musings it should be in a section that clearly states what they are. Martin Hogbin (talk) 00:30, 27 October 2013 (UTC)

I do not understand why you want to delete good info. The sentence is from a section that is entirely philosophical musings already. If you think that the sentence is misleading or confusing in some way, then tell us or clarify it.

Earlier the article says, "So length contraction is of kinematic, not dynamic, origin." The references are to Einstein 1905 and two philosophy papers. This is not a scientific fact but a philosophical view that is overwhelmingly accepted. But as you say, there is no experimental way to tell the difference, so the article should explain somewhere that both views are possible. Roger (talk) 05:24, 27 October 2013 (UTC)

I have deleted your quote above too. Can you explain to me what you think it means. Martin Hogbin (talk) 08:45, 27 October 2013 (UTC)

Much of the rationale for crediting Einstein for special relativity is based on an argument that he had a kinematic instead of a dynamic explanation for the contraction. After all, Lorentz had the formulas and the observational understanding before Einstein. But if that is all unscientific philosophical musings that don't belong in a science article, then I suggest deleting all the stuff about Einstein. Roger (talk) 11:27, 27 October 2013 (UTC)

What is the difference between a kinematic and a dynamic explanation? Martin Hogbin (talk) 11:35, 27 October 2013 (UTC)

You are asking the wrong guy. Ask Pais or any of the other historians who over-credit Einstein. The article on the History of special relativity says that Minkowski does not deserve credit because he did not recognize the distinction, and that physicists dropped the term "Lorentz-Einstein-Theory" when they figured out the distinction. If you want to go around deleting references to the distinctioni, you missed a few. Roger (talk) 00:01, 28 October 2013 (UTC)

Mainstream science

WP policy requires us to present scientific topics from the point of view of mainstream scientific consensus. This means that everything that is within the scope of physics (which means anything susceptible to experimental verification) should be presented from the POV of mainstream physics.

I personally have no objection to presenting the views of reputable philosophers on those matters that are outside the scope of physics so long as those views are clearly presented as philosophical thoughts and not as science. Questions about what length contraction 'really' is fall into the category of philosophy and must not be presented in such a way as to give the impression that there is any disagreement within the scientific community about length contraction. The mainstream scientific view on the subject and the resolution of issues such as the ladder paradox are covered in a multitude of modern reliable sources. Anyone who is not clear about this is a advised to read a good physics text book on the subject rather than to increase the confusion of our readers by including philosophical musings within the scientific content of the article. Martin Hogbin (talk) 09:17, 27 October 2013 (UTC)

I agree. In general, the historical passage on Einstein and Minkowski (A. Pais is certainly an authoritative source) should suffice. Maybe another article on the philosophical interpretation called "constructive relativity" would be a better place for further discussion, but before someone (certainly not me) writes such an article, WP:Notability should be considered. --D.H (talk) 09:33, 27 October 2013 (UTC)

You are making a straw man argument. The sentence I proposed said "some advantages to explaining relativity in a more constructive way", and it did not imply any scientific dispute about observable aspects of the contraction. I also did not claim that Bell and Brown had a mainstream view. It is, however, mainstream science that the alternative view is possible. The textbooks have said so for a century. The sentence was in a philosophical section with "reality" in the title. If you object to philosophy so much, then I would expect you to also want to remove the entire reality section and most of the history section. Roger (talk) 11:05, 27 October 2013 (UTC)

So what exactly is the point that you are trying to make? Is it about physics? Is it about how the physics is currently understood? Is it just a historical commentary? Martin Hogbin (talk) 11:33, 27 October 2013 (UTC)

Yes, it is about physics. I cannot explain it any better than Lorentz, Einstein, Bell, or Brown. There is more than one way to understand the physics. Yes, Lorentz's and Einstein's views have fallen out of favor, and Minkowski's view is preferred. However they are all valid views, and an encyclopedia should mention them. Roger (talk) 00:01, 28 October 2013 (UTC)

The article should present the current mainstream view of physicists on the subject. We could present the views of reputable recent philosophers who have shown an understanding of the physics, if there are any, in a 'Philosophy' section . I do not think we should show the views of armchair philosophers in this article. By 'armchair philosophers' I mean those purport to describe the universe in which we live by thought alone and without reference to experiment. There may be a place for such philosophers in WP but this article is not it.

Historical interpretations, such as that of Lorentz, are not in my opinion suitable for inclusion in this article. They may have a place in the history section of a more general article on SR but to add them here will only confuse our readers. Martin Hogbin (talk) 09:11, 28 October 2013 (UTC)

That's not correct, Roger. Einstein's and Lorentz's views are not the same. Einstein's views expressed in the kinematic part of his 1905 paper or his 1908 review paper have never been fallen "out of favor", and are the basis of this article (no aether, no distinction between "true" or "apparent" times or simultaneities, etc.).

This was put in a geometric form by Minkowski in 1907/8, who explicitly applauded Einstein for finding out that the time of one frame is as good as the ones in other frames (Well, Minkowski believed of himself as being the real discoverer of the principle of relativity that implies the "relativity of space" in a 4D-block universe. He also erroneously assumed that the relativity principle is in line with the electromagnetic worldview. The 4D-block-universe is still supported by some philosophers and physicists (Petkov), though the electromagnetic worldview is not and that part of Minkowski's writing was never accepted).

On the other hand, Lorentz's view of a "hidden aether at rest" with "true" and "apparent" times is not taught anymore in modern textbooks. And the views of Brown are not accepted as well. Again, try to write a philosophical article on "constructive relativity", but before you have to find enough peer reviewed sources. --D.H (talk) 09:30, 28 October 2013 (UTC)

D.H, I did not say that Einstein's and Lorentz's views were the same. I used the plural "views". Yes, Minkowski credited Einstein for saying that one electron time is as good as another, and also for clearly presenting Lorentz's relativity postulate. That's all. Minkowski credited Lorentz for many things. The WP article says "Einstein's view was further elaborated by Hermann Minkowski", with Minkowski as the reference. I very much doubt that Minkowski would agree with that, and most scholars say that Minkowski presented a geometric view distinct from Einstein's. So I think that sentence should be corrected. If you really want to just give the modern physics view, then just give the Minkowski geometric view and forget about Lorentz and Einstein. My opinion is that the different views are useful, both conceptually and historically. Lots of other physics encyclopedia articles give alternate views of some phenomenon. And I don't know who you are quoting with "hidden aether at rest", because I doubt that Lorentz ever used that phrase. Roger (talk) 00:11, 29 October 2013 (UTC)

No, we won't forget about Einstein. His connection of the operational definition of simultaneity with length measurements is the basis of the modern understanding, presented in numerous textbooks. This was brilliantly put into a geometric spacetime form by Minkowski, also presented in the same textbooks. But I'm not aware that mainstream opinion says that Minkowski's geometric formulation (at least as it is currently understood) is "distinct" from Einstein's special relativity, especially presented in the kinematic section of the 1905 paper. --D.H (talk) 09:00, 29 October 2013 (UTC)

I agree. Martin Hogbin (talk) 09:47, 29 October 2013 (UTC)

Physics FAQ

The section on the "reality" of length contraction contains a quote from the Physics FAQ. Is that really a suitable reference for Wikipedia? I don't recall ever seeing the Physics FAQ referenced in a Wikipedia article before (although admittedly I haven't read too many Wikipedia articles). Web pages usually aren't considered suitable references, are they? Some parts of the Physics FAQ are pretty good, and some parts are not too good, so I'd be careful. I don't have a problem with that specific quote, but I think the quote by Einstein is probably sufficient.Fiddlefofum (talk) 20:33, 28 October 2013 (UTC)

Yes, both quotes are essentially saying the same, so I removed the FAQ quote. --D.H (talk) 09:02, 29 October 2013 (UTC)

I think we could do with a good modern secondary source. I have looked through everything that I have and found nothing suitable. I think the Einstein quote should stay as it is but anything else we add should be in our own words but supported by good quality reliable secondary sources. Any suggestions? Martin Hogbin (talk) 09:45, 29 October 2013 (UTC)

Notation, Derivation

I've changed the notation in order to use the Lorentz factor throughout the article. Also the existing derivations have been streamlined, and another derivation (from proper length to contracted length) is included (see B. Schutz as reference). Hopefully, everything is comprehensible and useful to the readers. --D.H (talk) 16:19, 4 November 2013 (UTC)

1. 5 Proposal for a new section (and title on this page) called "The Philosophy of Relativity."

Still inept at navigating this site and all the many skills required to edit and contribute here. I would like to introduce a new section to improve Wiki's SR/length contraction information. (I hope to learn how to properly present and label my proposal and present it in "the right place.")

I propose a specific "philosophy of science" sub-section dedicated to "the philosophy of relativity." There, the common objection to the idealism upon which relativity is based could be discussed without the prevailing *censorship* (by all other possible euphemisms) by the relativity theorists here who will not allow such philosophical criticism of Einstein's idealism (as the intellectual basis of relativity... that 'reality' is defined by subjective* variations in perspective.. *.. in the broadest sense as 'frames of reference.') I will work out how to present such a philosophical discussion of relativistic idealism. (Einstein was an idealist, as I will verify by reference in "the philosophy of relativity" if the subheading is allowed.) Comments are welcome as I compose this presentation. (Hopefully not just more personal insults about how well 'proven' length contraction is and how stupid one must be to criticize it. No such critics are allowed so far in wiki's presentation on length contraction. LCcritic (talk) 01:56, 12 November 2013 (UTC)