Talk:Length contraction

Visual effects/optical predictions

The recent contribution that User:DVdm reverted in this edit is a mixture of documentable fact on the one hand, ... User talk:Prokaryotic Caspase Homolog

... which User:DVdm deleted anyway ... ErkDemon (talk) 21:13, 20 January 2025 (UTC)

... and unsourced assertions ... User talk:Prokaryotic Caspase Homolog

... which, where they showed any indication of being "controversial", were sourced to respectable peer-reviewed papers, mostly published in Am.J.Phys. , which is the journal of the American Association of Physics Teachers. The Gamow narrative is simply wrong. This was a controversy that was supposed to have been finally settled scientifically sixty years ago, but some people are still fighting for the right to present the bad science that was taught to them as kids as being the real deal. It's not. ErkDemon (talk) 21:13, 20 January 2025 (UTC)

... intended to cast doubt on (1) the reality of length contraction, (2) current interpretation of the phenomenon, and (3) the legitimacy of experimental verifications of length contraction. ... User talk:Prokaryotic Caspase Homolog

According to the main papers published on the subject of SR optics from Terrell and Penrose in 1959 onwards, the then-current "popular" interpretation of the phenomenon was, actually, mathematically wrong. The popular narrative did not agree with the theory's actual math. The Gamow mis-interpretation was supposed to have been dropped in 1959, but resurfaced in the Bronowski documentary, and was still being taught by some rogue professors at major universities as late as 1994.

This is a situation where the "popular" interpretation and the "scientific" interpretation diverged irrevocably sixty years ago.

Rather than accept the historical record, and allow it to be documented, encyclopaedically, User:DVdm simply deleted everything that didn't agree with what they were taught when they were younger.

Science sometimes makes mistakes ... but it tries to correct them. The people who try to defend science by pretending that no mistakes are or were ever made, and who try to delete all evidence of those known mistakes, are actually enemies of science. They corrupt critical information, and corrupt the process. ErkDemon (talk) 21:13, 20 January 2025 (UTC)

I would suggest that someone take the valid portions of User:ErkDemon's contribution and add those portions to the article on Terrell rotation. Prokaryotic Caspase Homolog (talk) 15:36, 20 January 2025 (UTC)

Except that Terrell rotation is only a small, specific part of the larger story. and some would argue that even Terrell's wording still wasn't quite right. Terrell rotation doesn't cover the Bronowski episode, or the Moreau reboot of the subject.

You know what? I was going to let this lie, but on consideration, I'm undoing the revert. If you want to tailor or trim the section, fine. But don't delete correct equations or referenced accepted peer-reviewed historical record, just because it disagrees with what you were taught as a kid. Don't censor history or destroy valid data just because you don't like what it says. ErkDemon (talk) 21:13, 20 January 2025 (UTC)

Unless you want to get blocked for edit warring, you better discuss here and get consensus before you revert again. - DVdm (talk) 21:53, 20 January 2025 (UTC)

Dear DVdm, I have no intention of getting into an edit war with you.

I have done one revert, on this article, you have done two. You justified your repeated deletion by writing "Undo almost entirely unsourced expansion" ... so ... was my increasing the number of sources in the section from four to twelve not enough? What If I gave you twenty ... would you then be happy? I can satisfy your objection by doing that if you want ... but the significance of each additional source saying the same thing will get rather repetitive. ErkDemon (talk) 18:53, 22 January 2025 (UTC)

@ErkDemon: That is not how edit warring works. You added new content, almost entirely unsourced, and others agree here. Then I reverted for the reasons stated. Then you reverted my revert. That is how edit wars begin: instead of reverting again, you should have started a discussion - see WP:BRD. Removing unsourced content multiple types, as I did, is not edit warring, it is protecting the project. See WP:NOCONSENSUS: "When discussions of proposals to add, modify, or remove material in articles end without consensus, the common result is to retain the version of the article as it was prior to the proposal or bold edit." The version prior to your bold edit is the version without your addition, so it can and shoud be removed, pending possible consensus. - DVdm (talk) 20:16, 22 January 2025 (UTC)

Resorting to insults about how reviewers of your work supposedly are not able to let go of what we "were taught as a kid" does not enhance your chances of getting your changes accepted. You have an attitude issue which permeates your proposed contribution to the article. Prokaryotic Caspase Homolog (talk) 23:21, 20 January 2025 (UTC)

... whereas you don't feel that DVdm is showing an aggressive and authoritarian attitude in saying: "Unless you want to get blocked ... you better ... " ?

Bear in mind that WP says that one should try to improve rather than delete. Salvage rather than burn. DVdm deleted an expansion that you yourself agree contained sourced material that may be appropriate for WP. So that was wrong. Time and effort permitting, the better thing for you to have done would have been for you to undo your friend's deletion action, and then trim off the parts that you considered inappropriate. It was helpful for you to suggest that some of the information could be reused ... but that's a reason for editing down, not full deletion. ErkDemon (talk) 20:01, 22 January 2025 (UTC)

@ErkDemon: The key point is "time and effort permitting". Due to age and health, I no longer am as active on Wikipedia as I once was. I might once have been very interested in performing salvage operations on your proposed contribution, since I am the dominant contributor to Special_relativity#Measurement_versus_visual_appearance (possibly around 90% my verbiage, but the edit history of this section is broken due to the text having been moved from Spacetime). I am the creator of both animations (one under a previous user name), and I have had another animation in progress illustrating mixed longitudinal and transverse effects, but I haven't really touched the animation for several years. So no, I have neither the time nor the energy to separate fact from personal agenda in your proposed contribution. Neither does DVdm, whose mission has been to protect this and many hundreds of other articles from dubious edits. The most efficient way for him to perform his self-appointed task is simply to revert objectionable content, leaving it up to the Wikipedia community in its consensus process to work out what ultimately gets added to an article. Prokaryotic Caspase Homolog (talk) 09:26, 23 January 2025 (UTC)

@Prokaryotic Caspase Homolog: Consensus process usually means "discussion before deletion". You appear to agree that your friend dVdm has deleted sourced content. Which is wrong. And dVdm has also declared that the information deleted wasn't sourced. Which we both know is at least partly untrue. If you are suggesting that dVdm does not have sufficient time or energy to protect "many hundreds" of articles with the care and attention that one is supposed to take, then perhaps dVdm should be reducing their own self-appointed workload, and patrolling fewer articles and applying sufficient care and attention to do the job properly, rather than spreading themselves too thinly and doing it badly. Perhaps they should step back and let other younger folk with more time and energy pick up the slack. Perhaps doing this for twenty years is enough.

Regarding peer-reviewed consensus, everyone who has followed the subject and kept up to date (at least as far as the end of the C20th!) knows that the standard narrative that used to be taught regarding length contraction was simply wrong. It was a mistake based on humans misunderstanding ambiguous human-language descriptions. But the math and geometry regarding "photographable" images and views is not ambiguous. The picture in Gamow's book of an approaching cyclist being seen to be contracted was very much NOT what the SR equations predicted, although it might seem to correspond to the accompanying Einstein SR texts. The current edition of the book now has a foreword by Roger Penrose warning that the descriptions in the book should not be treated as being literally correct. This is old news. Gamow released another book just after the Penrose-Terrell corrections, repeating the old, wrong narrative. There are stories (unconfirmed, and so not mentioned in the edit) that some people in the community were so annoyed and frustrated with Gamow at having to clear up his mess and protect his reputation that he might have missed out on a Nobel because of it.

The Penrose paper says that the visible outline of a moving sphere remains a sphere. Mary Boas' followup (Am.J.Phys. 1961) explains (and illustrates!) that the correct prediction, including timelag effects, is that an approaching train is seen to occupy more track, and a receding train is seen to occupy less track. It we take a photograph of a passing train, appearing-part-contracted and part-elongated, using a 180-degree fisheye lens, then whether the photo shows an overall Lorentz elongation or contraction depends on whether we choose to press the shutter when the pre-marked centre of the train passes our position (overall elongation), or when the receding and approaching ends are seen to apparently have the same length, in the viewfinder (overall shortening). For simple recession or approach, the degree of photographable, apparent contraction or elongation is governed by the same equation that gives the Doppler effect (visible length-change obeys the same law as visible frequency-change). So the visible apparent contraction or elongation can be considered "the spatial analogue'' of the Doppler effect (Penrose, 1959).

The (1973) Bronowski "Ascent of Man" episode, as originally broadcast, repeats the Gamow error, made even more compelling with computer graphics. The episode has since (2007!) been digitally remastered to be correct, and to instead conform to the 1961 Boas description. The cost of the remastering probably explains why the series was reshown so rarely, and the additional 3+ decades it took for the series to be released on DVD -- it couldn't ethically be released on DVD in its original broadcast form, because of the faulty SR episode. I watched the original broadcast. Getting hold of a pirate copy is difficult, but I do have a physical copy of the original book accompanying the series, and it clearly shows the Gamow-style mistake.

Terrell's further paper "The Terrell Effect" (Am.J.Phys., again, 1989) was supposed to be the definitive retrospective paper that cleared all this up once and for all. But apparently dVdm doesn't accept mainstream peer-reviewed histories if they disagree with dVdm's own beliefs about physics.

The final(?) twist (which helps explain the earlier misconceptions) is Moreau's 1994 paper (Am.J.Phys., yet again), which bothers to actually calculate the propagation progress of an outgoing spherical wavefront under SR when the source is reckoned to be moving. It turns out that the resulting shape is an elongated ellipse. Which, with hindsight is screamingly obvious, because the spreading wavefront needs to be a "conical section" of a Minkowski lightcone, and of course, if you remember introductory geometry, conical sections elongate (rather than contract!) as the tilt angle is increased. So in Moreau's final explanation, the "purpose" of the Lorentz contraction, which happens when we take this elongated ellipse in spacetime and tilt it a second time, is to contract the otherwise-expected elongated shape to fit back into the the original spherical outline. The Moreau ellipse is arguably the fundamental expression of special relativity, as not only do the rays correspond to the relativistic angle aberration formula, but each ray's length expands or contracts according to the SR predicted wavelength-change. It's the essentials of the entire theory in a single diagram, and if you plot multiple versions and intersect them correctly, the conic sections combine to reconstruct the Minkowski future lightcone. It's beautifully simple, and IMO it's the way we should have been teaching special relativity for the last thirty years.

The Moreau narrative takes us all the way back to the original Fitzgerald hypothesis, which was not that we see or measure moving things as Lorentz-contracting, but that a proposed hypothetical contraction would explain why we can't see or measure certain things as a result of motion. In other words, Fitzgerald contraction was not supposed to be a thing that you can measure unambigously, it was supposed to be the reason why you cannot unambiguously measure something else.

Doing the Boas propagation-timelag exercise, a receding body is photographed as apparently contracting by length'/length = (c-v)/c if the speed of light was fixed for the emitter, and length'/length = c/(c+v) if the s.o.l. was fixed w.r.t. the observer. By measuring the degree of photographable contraction (or photographable elongation, for an approaching body), one would be able to tell whether one was "really" moving or stationary, violating the PoR. What the Lorentz-Einstein approach does is to "split the difference" between the two conflicting predictions, taking their geometric mean, giving the new intermediate "relativised" prediction of length'/length = sqrt[ (c-v) / (c+v) ] . The "new" prediction differs from both earlier predictions by a Lorentz factor. So if we obtain an SR-compatible photo of a moving object, we can interpret it as being length-contracted if we believe the SOL is fixed in our frame, or interpret it as showing a Lorentz elongation if we believe that the s.o.l. is fixed in the other guy's frame. The contraction is the difference between SR reality and our expectations, depending on personal beliefs. But since we can never prove which frame the s.o.l. is "really" fixed in, we can never isolate the propagation and Lorentz components, to tell whether the Lorentz correction is a contraction or an elongation. So while we can experimentally test the overall equation's prediction, we cannot isolate the contraction component, on principle. Because if a muon was really physically-unambiguously length-contracted or time-dilated, then we could unambigously prove that it was "really" moving. Since SR is based on the principle of global lightspeed constancy, it can only achieve internal consistency via a certain degree of necessary ambiguity. I think you probably already understand this.

If you care about SR, and haven't yet seen or done the Moreau exercise, I very strongly suggest that you give it a go. I think you'll like it, and it may change the way that you see the subject. I could knock up some diagrams and an explanation for the SR page, but if I do, on past experience "the dVdm monster" will simply pop up and delete them, and claim that everything is unsourced or misrepresented ... so there's probably not a lot of point in my trying. ErkDemon (talk) 21:49, 6 August 2025 (UTC)

@Prokaryotic Caspase Homolog: Oh, and by the way, well done for the SR article's "Relativistic longitudinal Doppler effect" section. You're the first person I've seen that has commentated on Einstein's 1905 "section 7", who hasn't screwed it up. The problem is the position of the right-left page break in the Dover Press edition.

Normally, "experts" will look at page 56 of the Dover Press edition and copy the equation, and say that obviously the top part is the observer-fixed-c Doppler equation, and obviously the bottom part is a Lorentz redshift (because that's the normal narrative), and they absolutely refuse to budge, or to accept any correction. Linguistically-oriented brains. They don't think to actually look at the equations and see that Einstein has written the Lorentz factor as a blueshift, or turn back to page 55, and read that this is being calculated for a moving observer. I seemed to spend ten years of my life arguing fruitlessly with dim-witted relativity academics and graduates who couldn't get the fixed-emitter and fixed-observer Doppler relationships the right way round, all because of laziness, misplaced trust in what they'd been mistaught, and that damned Dover page-break. They would point-blank refuse to accept the possibility that they might have made a mistake. You're the first person in thirty-five years that I've seen get it right. Now that it's on WP, maybe the list of "standard stupid mistakes" will reduce by one. Thanks. ErkDemon (talk) 22:42, 6 August 2025 (UTC)

Please post personal correspondence on User talk pages. Please consider a series of shorter, focused edits. Large replacements of content routinely lead to reverts in my experience out of the practical reality that disagreement of any one aspect will condemn the whole. Johnjbarton (talk) 13:55, 7 August 2025 (UTC)