Talk:Length contraction/Archive 2

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.


 * 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)

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)

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)


 * Reference_desk/Archives/Science/2013_November_4
 * Wikipedia_talk:WikiProject_Physics/Taskforces/Relativity
 * Apparently, your views were not supported in the previous discussions. --D.H (talk) 09:30, 12 November 2013 (UTC)


 * Wikipedia is not censored, but there usually is a proper place for encyclopedic content that can be properly sourced. "The Philosophy of Relativity" is much too broad in scope for being a subsection here on this particular article. Although I've seen books on this subject while browsing the library (these are the sort I usually skim past though) there is likely enough material to constitute an entire article. For whatever portion of such critique is germane to this article, it's best to provide a large number of accurate secondary reliable sources that support the content.  Since SR is mainstream, views critical of length contraction are likely to come across as fringe and excluded or regulated to separate articles even if notable. In fact, I just took a brief look at our article on relativity and under its subsection "Status" it provides a link to Criticism of the theory of relativity. I haven't the inclination to wade through that long history though, but it's not uncommon for people to view relativity as an extension of Galilean relativity rather than as its antithesis. --Modocc (talk) 13:07, 12 November 2013 (UTC)


 * I do object to the recent deletion of correct and properly source material on this subject. Roger (talk) 06:20, 13 November 2013 (UTC)
 * I only put this page on my watch page as of yesterday, so perhaps you could provide a link or diff to that. --Modocc (talk) 09:07, 13 November 2013 (UTC)


 * I think he's referring to this addition and its deletion. See discussion above in section and the subsequent  as well.--D.H (talk) 09:40, 13 November 2013 (UTC)

Someone check Roger Penrose's Road to Reality book to verify the citation given!
Please check this. I checked my copy of Roger Penrose's Road to Reality book and couldn't find what is claimed in the article. Cogiati (talk) 13:24, 24 November 2013 (UTC)


 * In the caption of Fig. 18.15 of my copy (ISBN 0-679-45443-8) Penrose says that "... the image is compensatingly stretched in the direction of motion." In the footnote [18.13] he instructs the reader: "Develop this argument in detail, to show why the Fitzgerrald-Lorentz flattening exactly compensates for the effect arring from the path-length defference. Show that for small angular diameter, the apparent effect is a rotation of the sphere, rather than a flattening." (emphases mine). Our article says: "... demonstrating that length contraction instead actually shows up as elongation or even a rotation in a photographic image." This is indeed not backed by this source. The source says that the image will show no contraction and no elogation, just rotation. I don't have access to the other two refs. Anyone? - DVdm (talk) 18:56, 24 November 2013 (UTC)


 * Yes, the current references are insufficient, since there are many more aspects concerning the visible shape of moving bodies. For instance, see:
 * U. Kraus: Brightness and color of rapidly moving objects: The visual appearance of a large sphere revisited, American Journal of Physics, Volume 68, Issue 1, pp. 56-60 (2000).
 * She gave the following historical overview: p. 56: It was subsequently shown that the apparent length of a meter stick in a visual or photographic observation is not the Lorentz-contracted length1–4 and that quite generally, objects subtending a small solid angle appear rotated but otherwise undistorted,2,5 whereas objects subtending a large solid angle are seen as both rotated and distorted. A particularly intriguing result of these considerations is the fact that a sphere always presents a circular outline whatever its speed and its angular size may be.4,6–9
 * and the following sources:
 * 1 A. Lampa, ‘‘Wie erscheint nach der Relativitätstheorie ein bewegter Stab einem ruhenden Beobachter?’’ Z. Phys. 72, 138–148 1924͒.
 * 2 J. Terrell, ‘‘Invisibility of the Lorentz Contraction,’’ Phys. Rev. 116, 1041–1045 1959͒.
 * 3 R. Weinstein, ‘‘Observation of Length by a Single Observer,’’ Am. J. Phys. 28, 607–610 ͑1960͒.
 * 4 M. L. Boas, ‘‘Apparent Shape of Large Objects at Relativistic Speeds,’’ Am. J. Phys. 29, 283–286 ͑1961͒.
 * 5 V. F. Weisskopf, ‘‘The visual appearance of rapidly moving objects,’’ Phys. Today 139, 24–27 1960͒.
 * 6 R. Penrose, ‘‘The Apparent Shape of a Relativistically Moving Sphere,’’ Proc. Cambridge Philos. Soc. 55, 137–139 ͑1959͒.
 * 7 G. D. Scott and H. J. van Driel, ‘‘Geometrical Appearances at Relativistic Speeds,’’ Am. J. Phys. 38, 971–977 ͑1970͒.
 * 8 D. Hollenbach, ‘‘Appearance of a rapidly moving sphere: A problem for undergraduates,’’ Am. J. Phys. 44 ͑1͒, 91–93 ͑1975͒.
 * 9 K. G. Suffern, ‘‘The apparent shape of a rapidly moving sphere,’’ Am. J. Phys. 56, 729–733 ͑1988͒.
 * Maybe we should only mention the above source (Kraus 2000) and leave the rest to the main article on Terrell rotation.
 * PS: An excellent website written by experts on this field (Kraus, Weiskopf, Zahn) can be found here:
 * http://www.spacetimetravel.org/
 * Regards, --D.H (talk) 19:39, 24 November 2013 (UTC)

Relevance of "Philosophical Realism" to the "Reality of Length Contraction" subsection
Wiki: "Philosophical realism, belief that reality exists independently of observers." Length contraction is presented in the lead of the length contraction section as an observer related phenomenon and so affirmed by Einstein in his reply in the "reality of length contraction" subsection here. Further, in the Paradoxes subsection the relativity of simultaneity (RoS) is invoked as an explanation of the barn and pole paradox, i.e, that the observer's perspective sees the longer ladder fitting into the shorter barn as a function of his relativistic observational perspective. The RoS (basic to length contraction) denies a "real world" in which two events objectively happen at the same time, because relativity insists that when events happen depends on when different observers see them happen. All of the above denies the realism which states that reality exists independently of observers. Einstein himself said, ..."I am not a realist." He was the "father of relativity," and it is not based on realism. I think that readers of Wiki deserve a clear presentation of the fact that variations in measurement (from different frames of reference) do not reflect objective differences in objects and distances measured, in "the real world" independent of observers. LCcritic (talk) 20:09, 28 November 2013 (UTC)


 * See previous discussions at
 * Wikipedia talk:WikiProject Physics/Taskforces/Relativity#Criticism of relativity not allowed
 * Wikipedia:Requests for comment/Request board#Non-mainstream views of relativity
 * Wikipedia:Reference desk/Archives/Science/2013 October 31#Contracted Earth diameter and atmosphere depth
 * Talk:Length contraction#Physical?
 * DVdm (talk) 20:57, 28 November 2013 (UTC)


 * I ask editors here to reconsider Einstein's reply to Varicak's assertion in the "Reality of length contraction" section as follows: "In 1911 Vladimir Varićak asserted that length contraction is "real" according to Lorentz, while it is "apparent or subjective" according to Einstein.[17] Einstein replied: "The author unjustifiably stated a difference of Lorentz's view and that of mine concerning the physical facts. The question as to whether length contraction really exists or not is misleading. It doesn't "really" exist, in so far as it doesn't exist for a comoving observer; 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.[18] —Albert Einstein, 1911." This clearly states his opinion that the phenomenon depends on the observer ("for a co-moving observer" vs "by a non-comoving observer.") Realism states that objects exist and have intrinsic properties independent of observation. Einstein said (in his letter to Eduard Study), "I am still not a realist." Yet editors here will not allow this discussion in the section dedicated to the "Reality of Length Contraction." If not here, where?LCcritic (talk) 19:51, 16 February 2014 (UTC)


 * Probably nowhere in Wikipedia. Einstein saying in some context that he is not a realist is not necessarily related to length contraction. Your linking one the other is a schoolbook example of wp:SYNTH and wp:OR, as was explained to you in many places and many times before. As every idealist and every realist will agree, "proper length" is an intrinsic property, whereas coordinate length is not, just like rest energy of an object is intrinsic, whereas kinetic energy is not.
 * See more previous discussions at
 * Wikipedia:Help desk#Dispute Resolution is a Sham opened 27-Jan-2014, closed 28-Jan-2014
 * Dispute resolution noticeboard/Archive 85 Close as failed on 27-jan-2013: WP:SYN, sources appear to be unsuitable.
 * Talk:Criticism of the theory of relativity ended 4-jan-2014.
 * Talk:Criticism of the theory of relativity ended 16-nov-2013.
 * Reference_desk/Archives/Science/2013_November_4
 * Wikipedia_talk:WikiProject_Physics/Taskforces/Relativity
 * - DVdm (talk) 20:59, 16 February 2014 (UTC)


 * Why is this so contentious? Students of relativity commonly ask whether the contraction is real or apparent or what. Textbooks address the issue. Other WP pages address the reality of fields, wave functions, quarks, etc. The geometrical diagram and explanation in the article probably will not satisfy anyone. I say that the article should give the mainstream textbook explanation, but also mention others that are historically significant or currently viable, according to the reliable sources. Roger (talk) 04:57, 17 February 2014 (UTC)
 * This was already discussed in an archived discussion (Talk:Length contraction/Archive 2). There is no agreement to include philosophical debates like that of Brown et al. here. --D.H (talk) 14:48, 17 February 2014 (UTC)
 * Roger, we already have a section 'Reality of length contraction' which gives the current mainstream science view on the subject. This is exactly what students of the subject will want. Martin Hogbin (talk) 17:25, 17 February 2014 (UTC)

The subsection is about the "reality of length contraction." The quotes address the question of real vs apparent. The reader will expect that question to be addressed. The example given quotes Varacak as asserting that Einstein has it as apparent. Einstein denies the assertion, but then clearly says that it is observer dependent, i.e., that it depends on how it *appears* differently to different observers. Wikipedia editors must disambiguate this obvious contradiction for the benefit of its readers. Einstein's philosophy that what different frames observe are all equally valid, equally "real" is at the core of disambiguating this confusion, as it is the background context for the *reality* of length contraction. Citing "wp:SYNTH" and "wp:OR" simply says that wp policy makes the above disambiguation impossible. Nonsense. LCcritic (talk) 19:13, 17 February 2014 (UTC)


 * You are free to go to the policy talk pages of wp:SYNTH and wp:NOR (Wikipedia talk:No original research) and propose a change to the policy. - DVdm (talk) 19:23, 17 February 2014 (UTC)


 * LCcritic, you do really need to try to understand what relativity (and Einstein) say. He does not say that reality appears differently to different observers but that it is different (his words 'in such a way that it could be demonstrated in principle by physical means') to different observers.


 * It is no different to asking what the kinetic energy of a cricket ball really is in Newtonian mechanics. In different frames it has different values.  This is not just a matter of appearance but of simple fact.  In its own rest frame it always has zero kinetic energy. Martin Hogbin (talk) 19:34, 17 February 2014 (UTC)


 * "... you do really need to try to understand what relativity (and Einstein) say." I have studied relativity (as a philosopher of science) with a focus on Einstein's philosophy for over 18 years. You continue to insult me personally by assuming my ignorance because I do criticize length contraction (and NO criticism of relativity is "mainstream" by definition.) Yes, he does say that reality "is different" *to different observers.* "To different observers" means that each observation is equally valid. An Earth with a 4000 mile diameter is "equally valid" with the proper diameter length of nearly 8000 miles. But the latter is Earth's "real" diameter and the former is is Earth's **apparent** diameter as measured from a "frame of reference" approaching Earth at .866c, as per the "physics" of relativity according to the Lorentz transformation. Do not assume ignorance because of all the widespread disagreement with the absurd philosophy of shrinking physical objects. Clarity is required to distinguish between differences in the appearances of physical objects and the objects themselves, which do not shrink as observed from relativistic frames. LCcritic (talk) 00:34, 18 February 2014 (UTC)


 * Sorry if you find my comment insulting but it is clear from what you say that you no not understand what relativity says. The word 'apparent' is not used in relativity in the way that you have used it.  In the moving frame the length of a rod really is shorter.  That is to say any physical measurement of the rod made in the relatively moving frame, after allowing for the time it takes light to travel in that frame, will give a shorter length than the proper length.


 * You continually put up Aunt Sally (strawman) arguments and then prove them wrong. I am not going to respond to any further arguments by you that are based on you misunderstanding of the subject as I suspect other editors are getting fed up with this discussion, which is not about improving the article. Martin Hogbin (talk) 11:54, 18 February 2014 (UTC)


 * It is about improving the article. The subsection's title promises to clarify whether length contraction is real (physical shortening of an object) or just apparent shortening. Then Einstein is quoted as affirming that changes as seen from different frames are real changes. So, as per my obvious example, length contraction must claim that Earth's diameter "really" contracts in thousands of different ways, depending on the velocity and direction of thousands of different observers, i.e., that its diameter "really is" 4000 miles as measured from the frame approaching at .866c. Whatever applies to the length of a rod must also apply to the length of Earth's diameter. No "straw man" about it. Do not continue to mistake such criticism for ignorance. LCcritic (talk) 18:56, 18 February 2014 (UTC)


 * We cannot add our personal criticisms to the article. Wikipedia is not a place for us to vent our criticisms, as was explained many times in many places—see above. - DVdm (talk) 19:10, 18 February 2014 (UTC)

As I have said many times, this is not my "personal criticism" of SR. Still you ignore that and claim that it is about me promoting a personal point of view. This is intellectually dishonest of you, because you must know that such criticism (of the shrinking object relativity philosophy) is very widespread even though it is not allowed as testimony in criticism of SR in this encyclopedia. I hope to improve Wikipedia's tolerance for (and inclusion of) reasonable criticism of length contraction. But before that, I hope to change this subsection to reflect the debate about physical vs apparent contraction. LCcritic (talk) 23:45, 18 February 2014 (UTC)


 * I agree with LCcritic that his proposed edit is not SYNTH or OR. He is just quoting Einstein on an issue that is commonly discussed in textbooks. Roger (talk) 17:47, 19 February 2014 (UTC)


 * LCcritic's propsal is based on a misunderstanding of the subject. Einstein was quite clear on the subject and his view is still in agreement with mainstream physicists.  Objects, including the Earth, really do shrink (along the line of relative motion) when measured from a frame in relative motion.  That does not change their dimensions when viewed in their rest frame.


 * The spatial dimensions of an object are not invariant. Their actual values really do change depending on the frame in which they are measured.  It is just like a cricket ball in Newtonian physics; its kinetic energy is not a fundamental property of the ball it depends in the frame in which it is measured, just like the size of the Earth in SR has in infinite number of values depending on the frame in which it is measured.  If course, for those of use roughly at rest with respect to the Earth nothing changes.  Just as the kinetic energy of a cricket ball that you are holding in your hand is not affected by the fact that it has a higher value for someone in a passing car.


 * When LCcritic understands and accepts this simple, but unintuitive, fact he will realise that his arguments about 'shrinking object relativity philosophy' are meaningless. Martin Hogbin (talk) 18:11, 19 February 2014 (UTC)


 * Roger, the Einstein quote—about length contraction—is already in the article and speaks for itself. Any extrapolation of it—about the alleged realism or idealism of the theory as a whole—would be SYNTH/OR. - DVdm (talk) 18:21, 19 February 2014 (UTC)


 * My mistake. I thought that he was proposing to add the quote. I guess I misunderstood him. Roger (talk) 18:51, 19 February 2014 (UTC)


 * "LCcritic's propsal is based on a misunderstanding of the subject." In his opinion. Criticism of the claim that objects actually do physically shrink when (if) they are (were) so observed to shrink is not my misunderstanding but a clear expression of widespread criticism of the claim that all observed relativistic differences reflect real, physical differences in the objects measured. Regarding "Objects, including the Earth, really do shrink...," This is the core of the false assertion, confusing physical contraction with apparent contraction, as does the Einstein quote in the article, which clearly requires disambiguation. Earth's diameter IS and remains just under 8000 miles ("proper length": 7918 mi. equatorial; 7901 mi. polar) regardless of all possible frames approaching at all possible velocities from all possible directions i.e., "when measured from a frame in relative motion." A nutshell version from the Realism article: How is this NOT relevant to the "reality of length contraction" discussed here? It is of course, and should be included in any discussion of the *reality* of length contraction. LCcritic (talk) 20:40, 19 February 2014 (UTC)


 * LCcritic, length contraction is real. Relativity does not imply that the nature of reality is dependent on the observer. The theory is very precisely mathematically defined, and makes very concrete predictions of what each observer in each frame of reference should observe. To give you an intuitive, and very closely related analogy to length contraction, let me ask you the following question. When you look at an object from a different direction, has the object really rotated, or is the rotation just apparent? In your new frame of reference, the object is rotated, but we know that the same physical reality of the orientation and position of the object is being described, regardless of how angle you view it from. In relativity, there is an expanded set of transformations that involve not only the three spatial dimensions, but also the time dimension. The transformations that involve only the spatial dimensions are called rotations and translations, and these are what you're familiar with in your everyday life. You would never think to claim that because you can change your frame of reference and see an object from a new perspective, that physical reality does not exist. The transformations that involve the spatial and time dimensions are called boosts, and just like rotations, they just say how the same physical reality will appear from different frames. In this case, rather than rotated frames where the position or orientation of objects look different, we are discussing boosted frames, in which the lengths of objects and simultaneity of events are different. But the exact same physical reality exists, regardless of how you see it. This isn't a matter of debate in physics. -Thucydides411 (talk) 21:53, 19 February 2014 (UTC)


 * Hi Thucydides411, thanks for jumping in here, but please note that article talk pages are not for discussions about the subject. This was explained to LCcritic many times before in many different places. This talk page is not for teaching or explaining the basics of special relativity to the interested amateur. That too was explained to LCcritic many times before in many different places. Cheers - DVdm (talk) 22:05, 19 February 2014 (UTC)

Thucydides411, That was a long lecture for me to patiently endure, having studied the subject for nearly two decades, and having taught philosophy of science with a focus on relativity. "...they just say how the same physical reality will appear from different frames." Yes, I understand the Lorentz transformation concept as a tool of math. Maybe you should read my contributions before you jump in with yet another mainstream lecture. The issue is whether physical objects actually, physically contract (as so observed to contract from theoretical high speed frames) or whether they only might appear to contract as measured from frames moving at near 'c' relative to the object observed. "length contraction is real" is a meaningless statement until you address the physical vs apparent issue and understand the difference. Btw, "talk" pages are indeed for talking about the issues relative to the articles discussed. Do not let DVdm intimidate (bully) you. We are trying to improve the article via conversation about its content. Wikipedia's policies pertain to another issue, to be addressed in the right place (later, for me) in this extremely complex labyrinth of library protocol. LCcritic (talk) 02:00, 20 February 2014 (UTC)


 * Thucydides411, I am as guilty as you of using this talk page to try to educate LCcritic but I think if we are going to proceed with this discussion it should be in someone's user space. Martin Hogbin (talk) 10:07, 20 February 2014 (UTC)


 * Putting the POV lectures which don't belong here aside, LCcritic did not indicate that he is proposing new text by marking them off with italics or additional quotes. Instead, LCcritic, you offered an editorial, but we don't publish these. -Modocc (talk) 14:54, 20 February 2014 (UTC)


 * I thought it might help to explain to LCcritic why the criticisms they want to include in the article don't actually make sense, but if LCcritic is just here to endlessly debate the subject, I agree that we should just wait for some proposed text before continuing any discussion. -Thucydides411 (talk) 18:20, 20 February 2014 (UTC)


 * I propose adding the following (except the parenthetical) to the "reality of length contraction" subsection: Reality is a philosophical issue. (from Wiki (From Wikipedia's Reality article. Need help noting this quote.) As Einstein said above, special relativity considers different object lengths as measured from different observational frames to be "real," while philosophical realism disagrees, i.e., that physical objects do not actually shrink as observed from various relativistic frames. (Any objections?)LCcritic Ps; "Objects, including the Earth, really do shrink..." Really?! The qualifier clearly states thaser talk:LCcritic|talk]]) 19:12, 20 February 2014 (UTC) Ps, as to Martin Hogbin's assertion above, "t this "reality" is observer dependent, i.e, not based on realism as Wiki- defined above: "... "when measured from a frame in relative motion."LCcritic (talk) 19:31, 20 February 2014 (UTC)


 * The objection is simple: wp:SYNTH and wp:OR. - DVdm (talk) 19:36, 20 February 2014 (UTC)

From "Criticisms of the theory of relativity" lead: “Even today there are some critics of relativity (sometimes called "anti-relativists"), however, their viewpoints are not accepted by the scientific community.” Two sources are cited as legitimate mainstream spokesmen for “the scientific community” excluding such criticism. There are dozens of critics of selected parts of relativity (like length contraction), but the editor of the lead generalizes that no such criticism is accepted. How is it that this generalization is allowed, as it is definitely a “synthesis” drawing a conclusion on the part of the editor as gleaned from his understanding of the history of relativity. Again in the "Philosophical criticisms" subsection of that article the editor generalizes to a conclusion based on a synthesis of his (mis)understanding and exclusion of contributions from the field of philosophy of science. I offered the example of Kelly Ross’s excellent historical and technical understanding of the transition from Euclidean to non-Euclidean geometry/cosmology as the basis for relativity, but Paradoctor, in absolute authoritarian fashion, *forbade* me from mentioning him again. If “SYNTH” and “OR” are to be enforced as excluding my proposed addition, then the same must apply to the above and, no doubt, many other examples of synthesis/conclusion by editors here.LCcritic (talk) 18:37, 21 February 2014 (UTC) Ps, my mention of Paradoctor reminded me of a quote from him which should have long ago settled this issue, since he presents himself as a mainstream authority on length contraction: "Please note that I'm not talking about proper length, which is a physical property, and does not undergo contraction." So length contraction is not a physical phenomenon according to Paradoctor, but "Objects, including the Earth, really do shrink..." according to Martin Hogbin. Does anyone besides me see a screaming need to "disambiguate" this issue? LCcritic (talk) 18:57, 21 February 2014 (UTC)


 * Note: I just gave you a fourth level warning for this addition (against consensus) of unsourced content: see . - DVdm (talk) 20:47, 23 February 2014 (UTC)


 * Realism is a slippery subject. Any attempt to disambiguate should refer to outside sources so the reader can learn whatever philosophical point you are trying to make. Roger (talk) 06:17, 24 February 2014 (UTC)


 * The point that I am trying to make was made very clearly and concisely by Thucydides411 above: "But the exact same physical reality exists, regardless of how you see it." This contradicts the mainstream insistence, as articulated above by Martin Hogbin: "Objects, including the Earth, really do shrink..." The meaning of "really do" is contradicted by his qualifier, "..."when measured from a frame in relative motion." This clearly says that length contraction is observer-dependent, whereas philosophical realism (as per Wiki"s Reality article) says, "Philosophical realism, belief that reality exists independently of observers." I don't know how to make an editorial attempt at disambiguation any more clear. The Wiki nutshell version of philosophical realism could not be more clear, nor can the concept that frame/observer dependent measurements are not based on philosophical realism. But DVdm obfuscates this attempt at disambiguation every time. Finally, those editorial conclusions I cited above were in fact made on the basis of synthesis, which is allowed in support of the mainstream but not allowed for critics. If the policy is to be enforced (I am about to be banned) it should be enforced for all editors equally, including those who generalize from a synthesis of cases as they understand them in support of mainstream relativity. LCcritic (talk) 19:11, 24 February 2014 (UTC)


 * Like it or not Wikipedia has a section on the "Reality of length contraction," and the issue can not be swept under the rug (unless the whole section is deleted, as well as "criticisms" article.) The search for "acceptable sources" in an encyclopedia which accepts no criticism of special relativity is made impossible by that policy. Yet supporters of mainstream length contraction continue to admit the same principle as cited by the ubiquitous community of critics. The most recent example is the quote from Thucydides411 cited above. Another clear example was given by editor Red Act with the approval of mainstream supporters here ('talk' 22:28, 5 November 2013 ; reference desk): “As is common sense, none of Earth's geometric properties change at all due to what coordinate system the geometric properties are expressed in, if any, or what velocity some human or some inanimate object is traveling at relative to the Earth, or what's going on in the brain of some human.” Further, I have quoted the famous particle physicist and accelerator designer Delbert Larson as follows (not allowed as a legitimate source): “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.*” (My * emphasis.) Either length contraction is physical or only apparent, an artifact of measurement from different frames. It can not be both ways. Wikipedia claims to endorse disambiguation as an important concept in service to clarity for the reader, yet no one will touch my last post (or this one, I expect) with a ten foot pole. That would be five feet if observed approaching at .866c they claim. Not just "apparent" they claim, as the 'proper' 10 ft pole "really will" fit into a five foot barn at that speed. But no one can explain the physical shrinkage... and then apply the same principle to Earth's diameter. The issue will not go away even after I am banned. It behooves the editors of this encyclopedia to deal with it and quit disqualifying sources on the very grounds that they are critical of length contraction.LCcritic (talk) 20:44, 27 February 2014 (UTC)


 * LCcritic, I have some sympathies for you because I inserted a minority interpretation of the contraction, and had it reverted. But I do not claim that there is anything wrong with the mainstream interpretation, and I gave reputable sources. An alternate view can be valuable for historical, philosophical, or pedagogical purposes, even if it is not the preferred view.
 * You say, "Either length contraction is physical or only apparent, ... It can not be both ways." Yes, it can be both ways. More than one view is possible. But it is no use arguing with anyone here about philosophical realism. They are going to go with what the textbooks say, even if they think that you are right. You have to have some realiable sources. Roger (talk) 23:08, 27 February 2014 (UTC)


 * Regarding your opinion that, "Yes, it can be both ways," of course an infinite variety of views are possible, but science must be objective in its investigation of the nature of the cosmos. Individual differences in perception are collectively another field of study, well known among psychologists and philosophers of science. I especially refer to those who know the difference between idealism and realism. One depends on individual differences in perception as describing "reality." The other is physics, before it became RELATIVITY, beyond challenge, now all about frames of reference/ points of view as dictating multiple "realities." Realists disagree with that philosophy, but we are not allowed to edit here.  — Preceding unsigned comment added by LCcritic (talk • contribs) 01:20, 28 February 2014 (UTC)


 * Roger, you must understand that relativity can not claim both, that physical objects shrink and also that they do not shrink. Clarity lies in distinguishing artifacts of measurement at high speed relative to objects (and distances) measured (*apparent* contraction) and *physical* shrinking of objects themselves and distances between them, as per interstellar travel thought experiments.(The claim is false that the faster one travels the shorter the distance traveled.) The apparent/physical distinction must be made clear to all readers of the "reality of length contraction" section. 71.215.180.32 (talk) 19:21, 1 March 2014 (UTC)


 * You are advocating a philosophical opinion, with no support from sources. Roger (talk) 17:00, 2 March 2014 (UTC)

As I said above, the search for "acceptable sources" in an encyclopedia which accepts no criticism of special relativity is made impossible by that policy. Yet editors here in support of mainstream SR admit that physical objects do not shrink. See examples quoted above, leaving length contraction as an apparent phenomenon, an artifact of measurement, not a change in objects measured. Even Delbert Larson, a recognized expert in the field concludes that there is no experimental evidence for physical contraction. Not allowed. It's not about "no support from sources." It is about no criticism allowed. Einstein said, "I am still not a realist." That was his philosophical disavowal of realism, also not allowed. Same with Godel... that relativity is based idealism. Not allowed. Same with Henry Lindler, that Einstein was "a subjective mathematical idealist." Not allowed. Same with Lewis and Tolman, that length contraction effects are "not physical changes in the body itself." Not allowed. Same with Kelley Ross's excellent philosophical understanding and critical analysis of the basis of relativity. Not allowed. If critical, not allowed. Some way to run an encyclopedia which actually includes an article on "Criticisms" of relativity and a section on the "Reality of length contraction!" LCcritic (talk) 21:08, 2 March 2014 (UTC)


 * This has all been discussed dozens of times before—see pointers above. You are disrupting this talk page. There is no consensus for what you like to add. Please stop now. See wp:DEADHORSE. - DVdm (talk) 22:00, 2 March 2014 (UTC)


 * Roger declared that I have no support from sources, so I cited those sources again as an appropriate reply. They speak directly to the subject, "the reality of length contraction," not a disruption of conversation on the subject, which is your often stated opinion, also not a statement of fact. In fact, no editing of the text on the subject of "reality" vis-s-vis length contraction is allowed if it disclaims the reality of physical contraction. You are the primary enforcer of this *opinion* forbidding any actual discussion of reality pertaining to LC by published sources. It is you who are disrupting the editorial process on this subject/subsection. Please stop. LCcritic (talk) 18:45, 3 March 2014 (UTC)


 * Your sources and your interpretations were already dismissed:
 * Henry Lindler was dismissed here.
 * Delbert Larson was dismissed here.
 * Kelley Ross was dismissed here
 * Your interpretation of Lewis and Tolman, Einstein, and Godel was dismissed in User talk:Modocc/Archive 1.
 * See wp:DEADHORSE and wp:GETOVERIT. - DVdm (talk) 19:40, 3 March 2014 (UTC)


 * I will formally request arbitration regarding the grounds for these dismissals. In preview, my first request will be in regard to the Lewis and Tolman source from the following quote from the "Full text of 'The Principle of Relativity, and Non-Newtonian Mechanics'": “The distortion of a moving body is not a physical change in the body itself, but is a scientific fiction.” This must not be dependent upon the mere opinions of editors who participated in those dismissals. Let the discussion here also consider the following from Wikipedia's article, "Trouton–Noble experiment": “Following this line of reasoning, Rohrlich (1966) distinguished between "apparent" and "true" Lorentz transformations. For example, a "true" transformation of length would be the result of a direct application of the Lorentz transformation... On the other hand, *length contraction would be an example of an apparent transformation*, since the simultaneous positions of the endpoints in the moving frame must be calculated in addition to the initial Lorentz transformation. “ (My * emphasis) Consider also this quote from "Science and Cultural Crisis..." by Maila L. Walter: "To (Lewis and Tolman) the distortion of a moving body could not be an actual physical change, but only apparent." LCcritic (talk) 20:13, 3 March 2014 (UTC)


 * Yes, please, do formally request arbitration, because this is going nowhere. - DVdm (talk) 20:44, 3 March 2014 (UTC)


 * LCcritic, you should be aware that Arbcom do not arbitrate content disputes but only deal with user behaviour. In this case you may well find that your continual attempt to edit against mainstream science and the strong consensus of editors here backfires and you are sanctioned for tendentious editing.


 * If you really want to know why it is that practically every other editor here disagrees with you I suggest that you invite further discussion on your talk page. Other editors may lose interest though if you do not listen to what they are telling you and try to understand it.  Martin Hogbin (talk) 09:27, 4 March 2014 (UTC)

Martin Hogbin, Thanks for the information that there is no arbitration available on the issue of dismissal of sources. I will not waste effort seeking such arbitration. Editors are always welcome to "talk" on my talk page, but this article talk page is for discussion of (in part) "the reality of length contraction." So far, no one has addressed those cases where editors do agree with realism on the core of the issue, as follows: Thucydides411; “But the exact same physical reality exists, regardless of how you see it.” Red Act (with the approval of some mainstream supporters here): “As is common sense, none of Earth's geometric properties change at all due to what coordinate system the geometric properties are expressed in, if any, or what velocity some human or some inanimate object is traveling at relative to the Earth, or what's going on in the brain of some human.” Also, still no comment on the acceptability of Lewis and Tolman as sources: “The distortion of a moving body is not a physical change in the body itself, but is a scientific fiction.” Also no comment on the quote above from the “Trouton–Noble experiment" article, distinguishing between apparent and true length contraction. And, 'from the horse's mouth,' "I am still not a realist." There is no way to misunderstand that. Einstein meant what he said. SR is in fact based on observer dependent measurements as illustrated in the text quoting Einstein, and idealism is the philosophy that "reality" is observer dependent. This directly addresses the section, “the reality of length contraction." Finally, you said, "Objects, including the Earth, really do shrink...," (promoting your take on "reality") and then added the qualifier, "...when measured from a frame in relative motion." That latter asserts observer/frame dependence (idealism, not realism) as defining that "reality." Finally, what was the reason for dismissing Delbert Larson's conclusion, as a recognized expert in the field, that there is no evidence for length contraction? I insist that all the above not be swept under the rug, and this is the place to "talk" about "the reality of length contraction." LCcritic (talk) 19:24, 4 March 2014 (UTC)


 * Repeating—3rd time:
 * It is commonly agreed that relativity is very much a realist theory. For example (with emphasis added):
 * "It is commonly agreed that neither special relativity theory nor general relativity theory contains any compelling argument against an Einsteinian metaphysical realism. An interpreter of these theories may have philosophical reasons against this epistemology, perhaps in the form form of doubts about the correspondence theory of truth, but on physical grounds alone he can stay with objectivity in the strong sense. On the other hand, the relativity theories distinguish sharply between relative properties, dependent on the reference frame, and absolute ones, independent of it."


 * See Dispute resolution noticeboard/Archive 85 which was closed as failed on 27-jan-2013 by : "WP:SYN, sources appear to be unsuitable."
 * Time to let it rest. I propose that we WP:JUSTDROPIT - DVdm (talk) 07:33, 5 March 2014 (UTC)
 * LCcritic, I have copied this to your talk page, please respond there. — Preceding unsigned comment added by Martin Hogbin (talk • contribs) 09:38, 5 March 2014‎ (UTC)


 * The philosophy of shrinking objects based on "Einsteinian *metaphysical* realism" (my *) or so called "scientific realism" (in which reality is determined by variations in observation) does not in fact constitute the "commonly agreed" definition of realism, so the subject can not be "just dropped" there. Examples: Encyclopedia Britannica: “Realism, in philosophy, the viewpoint which accords to things which are known or perceived an existence or nature which is independent of whether anyone is thinking about or perceiving them.” Wikipedia: “Contemporary philosophical realism is the belief that our reality, or some aspect of it, is ontologically independent of our conceptual schemes, perceptions, linguistic practices, beliefs...” Wikipedia; Realism: “Philosophical realism, belief that reality exists independently of observers.” The Basics of Philosophy: “Realism, at it simplest and most general, is the view that entities of a certain type have an *objective reality, a reality that is completely ontologically independent of our conceptual schemes*, linguistic practices, beliefs, etc. Thus, entities (including abstract concepts and universals as well as more concrete objects) have an existence *independent of the act of perception*, and independent of their names.” (My *...*) The above posts ignore all points made in my last edit. Absolute stonewalling, not discussion of the topic at hand. The most obvious example that physical objects do not contract as a result of theoretical changes in frames of observational reference remains the unchanging diameter of Earth. Simply repeating various versions of physical length contraction, like, "Objects, including the Earth, really do shrink..." does not make it so. The above definitions of realism are in fact the "commonly agreed" definitions. Neither censorship of true realism or inventing new definitions of it to suit SR will change that. LCcritic (talk) 18:41, 5 March 2014 (UTC)Ps; That said in clarification of common definition of realism and for closure on this page, let's continue any further discussion, as suggested, on my talk page. LCcritic (talk) 18:49, 5 March 2014 (UTC)

Deformation of Objects
When the length contracts, I assume that things like volume and surface area are affected.

In every day life, I mean I guess where both the observer and the object are not moving relative to each other, if you deform an object, it will resist this depending upon how rigid it is. Also, applying force to it will change its temperature and permanently affect its structure.

Does relativistic length contraction work this way? Would, for example, a more-rigid object deform less than a less-rigid object? Does the object's temperature increase due to the mechanical force applied? And does the object permanently change, once it slows down relative to the observer are there measurable effects that remain?--Jrm2007 (talk) 05:30, 19 April 2014 (UTC)


 * You'll have to go to our wp:reference desk/science with this. Here we discuss the article, not the subject. See wp:talk page guidelines. Cheers - DVdm (talk) 07:50, 19 April 2014 (UTC)


 * Or ask on my talk page. Martin Hogbin (talk) 08:57, 19 April 2014 (UTC)


 * I am confused by the difference between the article and the subject discussions. I ask a question implicitly so that the answer to it potentially may be included in the article. Is that not a valid usage of this page?--Jrm2007 (talk) 09:30, 19 April 2014 (UTC)


 * That you proposed adding to the article was not obvious from your question. To answer it: No, none of these things happen. To mention this in the article, we need reliable sources stating this. This will probably require some searching, but I think that some textbooks discuss this specific question. Paradoctor (talk) 09:56, 19 April 2014 (UTC)

If the answers to the questions asked are not apparent to Jrm2007 from reading the article then there is an argument that the article should be improved so that the answers to at least some of these questions are made clearer. That could be discussed here or, as I suggest above, in user space somewhere.


 * I'm not aware of saying anything to the contrary. I even suggested a set of possible sources. When it's about article content, this talk page is the right place for discussion. Paradoctor (talk) 19:57, 19 April 2014 (UTC)
 * Paradoctor, my comments above were not aimed at you or anyone in particular, which is why I have reverted to my original indentation. The point is that by answering Jrm's questions here we may discover deficiencies in the article that will suggest ways that it can be improved.

Jrm2007, relativity seems to be a subject that attracts more than its fair share of people who appear to wilfully misunderstand the subject or demand to be allowed to propagate their own idiosyncratic understandings of the subject in WP. Discussions with these people have wasted much time of editors here, who are working to genuinely improve the article. For that reason many here regard questions about the subject itself with some suspicion and tend to want to enforce the rule that the talk page should be used only for discussions about improving an article rather more strictly than it is for other articles. Martin Hogbin (talk) 18:36, 19 April 2014 (UTC)
 * Yep. I don't think we're particularly strict, though. Relativity articles just offer more opportunities to point out the rules. Paradoctor (talk) 19:57, 19 April 2014 (UTC)
 * See my reply above. By answering Jrm's questions here (which we assume to be asked in good faith and with a view to improving the article) we may discover ways in which some things can be made clearer to the general reader. Martin Hogbin (talk) 22:36, 19 April 2014 (UTC)
 * Perception seems to contain idiosyncrasies to some extent. On that note, the article seems to suggest that length contraction would be accompanied by an increase in density (relative to the observer) or if density is assumed to stay constant, a decreasing in length in the direction of propagation would be accompanied by an increase in length along the transverse axis..RotogenRay (talk) 19:30, 29 July 2014 (UTC)

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Clarify length measurement.
The following in the intro is unclear to me: “…by subtracting the simultaneously measured distances of both ends of the object.” Distances of both ends from what? I think the author meant the distance from one end of the object to the other, at a single point in time. This is as opposed to an observer, in parallel motion relative to the object, marking one end when passing it by and then marking the other end when passing that end a moment later. Since the measurement IS to be simultaneous, I think the observer would have to measure the object when reaching its midpoint, and with a measuring rod long enough to capture the entire length in one measurement – at a single point in time. No subtraction would be necessary, as one end of the rod is zero. Bfishkin (talk) 06:31, 2 December 2017 (UTC)


 * The sentence in the article says: "For the observer in relative movement, the length of the object is measured by subtracting the simultaneously measured distances of both ends of the object." The distances of both ends of the object are measured from the origin of the coordinate system in which the object is moving, and thus they are the endpoint distances from the observer (sitting at his coordinate system origin) who is doing the measurement. This is made clear later in the article in the derivation section. - DVdm (talk) 12:00, 2 December 2017 (UTC)

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What's up with the picture captions?
The captions for both of the pictures in the "Minkowski diagram" box and the one labeled "The muon-atmosphere-scenario" don't make any sense. What happened there? --uKER (talk) 19:25, 1 February 2018 (UTC)
 * A real mess indeed. Feel free to prune. - DVdm (talk) 08:17, 2 February 2018 (UTC)

Advanced Mathematical Considerations and Limitations of Use
The reason to take second look at special relativity is because it's symbols are so much used in books and to explain so many phenomenon.

Einstein's achievement of using $$\gamma$$ was one of canonicalizing variables and $$\gamma$$ was not his only achievement. The use of $$\gamma$$ is extremely limited but extremely handy. Keep in mind it is only useful as a magnitude and only under limited conditions.

We've probably heard light can take years to arrive from afar and some stars are expired by the time their light arrives.

Imagine the problem of realizing a measurement that was the elapse of time and stored as an image to find dimensions of a distant fast moving object; that of tracing each light wave and time of arrival back to a moving object and correlating. Solving partial differential equations (light wave equation) with conditions. The problem can turn to be of tracing a grid of Electromagnetism waves. Light waves on the right of the grid arrive later than central waves and the object spends more time on the left then it does on the right because its moving. Add to this having to equate optical Diffraction and finally Field_of_view for large objects. And because of all that the resulting image would certainly not be "smooth" or a real 1-1 image but one of overlaps and mystery. Obvious a simpler tool - one that simply yields only the length in the simplest of situations (ie, if orthogonal and midpoint to view), is more handy.

The Length Contraction formula (the geometric triangle of equalities of all vectors involved in the simplest solution) can be shown to use special velocity and time difference and positions so that the object passes it's own length through the midpoint of observation during the time it takes for light to reach the observer on the shortest path, and the astute observer (Einstein) finds that the same small equation applies equally well to any length once derived. This also means time dilation and length contraction are virtually same problem.

Back to Limitations: the above note of "fully calculations of an image" shows more limitations than one can plainly mention. This matches perfectly the fact it is a small math equation: it should be treated as such.

The definition of Canonical variable. A canonical variable has it's units re-arranged (i.e. length, time, mass) for a math equation so that un-necessary factors or loose terms that would carry a large penalty while solving are minimized (by legitimate substitutions): the Wave Equation of light is one such PDE. — Preceding unsigned comment added by 2601:143:400:547B:94F6:2347:9F50:AC34 (talk) 01:36, 30 August 2019 (UTC)

Considerations and Limitations and Canonicalization of Variables for PDE
I can't say the section above duly matches Wikipedia's preference for both describing well enough and for staying brief as these are subjective and involve topic splitting.

But I would like that Canonicalization of Variables for partial differential equations be mentioned*, that there is a severe limitation of use, and even indication (as to limitations) that "linear algebra sheering" is certainly not "a full solution". (because the PDE wave equation for E&M is terribly more difficult and sometimes impossible to solve without canonicalization - and Einstein would have had motivations in that direction. that is, the use of gamma was not to avoid a simple math triangle to include light vectors:  but to make certain PDE possible to solve that he worked with)).

Furthermore the article mentions setting t1=t2, but properly there are 2 times and they cannot be equal unless V*T was specially chosen (if one is solving the problem from scratch, that is, as in the boxcar problem).

And the article seems to say position (left to right end position) is corrected by "extending the correect side by v*dt": but infact only magnitude is corrected: the actual tip and tail positions must be treated separately once actual length is known and the problem at hand is considered to be a position vector problem (for example:  v is squared so to apply a vector direction sign to it will be deleted, and that must be considered). — Preceding unsigned comment added by 2601:143:400:547b:94f6:2347:9f50:ac34 (talk) 13:39, 30 August 2019 (UTC)


 * Please sign all your talk page messages with four tildes ( ~ ) — See Help:Using talk pages. Thanks.
 * All new content in Wikipedia must be reliably sourced. Please read wp:verifiability and wp:no original research. - DVdm (talk) 07:56, 30 August 2019 (UTC)

Lorentz length contraction
Is Lorentz length contraction spatial or temporal in nature? Furyan5 (talk) 13:58, 19 November 2019 (UTC)
 * You can ask at the wp:Reference desk/Science. Here we can only discuss the article, not the subject—see wp:Talk page guidelines. Good luck! - DVdm (talk) 14:18, 19 November 2019 (UTC)

The very first sentence "Length contraction is the phenomenon that a moving object's length is measured to be shorter than its proper length" is incorrect — Preceding unsigned comment added by 2A01:36D:A007:8F04:35AF:B49:3DD7:CB92 (talk) 15:24, 15 February 2021 (UTC)


 * The literature contradicts you — see Google Scholar and Google Books. - DVdm (talk) 16:03, 15 February 2021 (UTC)

POR
Changed and removed the “..laws of physics must assume the same form..” for the Principle of Relativity, which is false. That statement is one of General_covariance, and has no physical meaning. Any set of equations may be put in Covariant form. Kevin Aylward 15:53, 2 June 2020 (UTC)


 * The literature contradicts you — see Google Scholar and Google Books. - DVdm (talk) 16:03, 15 February 2021 (UTC)