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This is an old revision of this page, as edited by Redrose64 (talk | contribs) at 10:05, 19 March 2021 (→RfC on Time contraction: WP:RFCBEFORE; and since there is now a discussion at Misplaced Pages:Redirects for discussion/Log/2021 March 18#Time contraction, WP:RFCNOT applies too). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

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	Time dilation was a good articles nominee, but did not meet the good article criteria at the time. There may be suggestions below for improving the article. Once these issues have been addressed, the article can be renominated. Editors may also seek a reassessment of the decision if they believe there was a mistake.
Article milestones Date Process Result December 16, 2006 Good article nominee Not listed

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Dilation in parallel movement

I propose including the case of a moving observer traveling parallelly. Since all calculations are elementary arithmetic operations, I would like to invoke WP:CALC. Anyway, readers need more mathematical knowledge to understand the orthogonal case. 84.120.7.178 (talk) 05:05, 31 August 2020 (UTC)

We could only add that other case if there is a reliable source. Otherwise it is wp:original research, and this is way beyond wp:CALC. But the idea of the section is to give a simple inference of time dilation as a consequence of the invariance of light speed, and orthogonal movement w.r.t. to the light signals is the way it is almost always done in the literature. So I don't think we need another way here. - DVdm (talk) 06:35, 31 August 2020 (UTC)

1. You should undo your reversion because the edit is independent of this discussion. It is not original research, but a clarification of the described case. It does not reach any conclusion about the parallel case.

   It is as in Lorentz factor: "The simplest case is a boost in the x-direction."

2. Misplaced Pages asserts that time dilation is:

   ${\displaystyle \Delta t'=\gamma \Delta t}$

   This insinuates that it is always true, so WP:NPV is broken.

3. Why do you say this is way beyond WP:CALC? Do you know the result? Do you not understand the calculations? 84.120.7.178 (talk) 14:30, 31 August 2020 (UTC)

1. I undid your edit because it is irrelevant in the context of the section.
2. Without specification of the physical meanings of the variables and the context, that equation is meaningless. This is physics, not mathematics.
3. Yes, I understand the calculations, but what you have in mind, aren't just routine calculations: again this is about a physical situation with a relevant physical context, and a source is needed to establish (1) correctness of the physical reasoning, and, just as importantly, (2) whether the content is wp:noteworthy to be included in Misplaced Pages to begin with. If no textbook ever mentions it in the context of time dilation inference from light speed invariance, then it has no place in Misplaced Pages—by design. I don't recall having seen in the literature any inference of time dilation from LS-invariance with a light clock and an observer moving non-perdendicularly w.r.t. the clock. - DVdm (talk) 15:35, 31 August 2020 (UTC)

You say that you understand the calculations. Tell us what is the time dilation in parallel movement and I will be convinced. 84.120.7.178 (talk) 16:15, 31 August 2020 (UTC)

Alas, that is off-topic here on the article talk page per wp:Talk page guidelines; here we cannot discuss the subject, but only the article and proposed changes to it, based on wp:reliable sources.

I know there are many webpages out there where the time dilation of the "horizontal" light clock is shown as some sort of verification, where the reasoning also relies on length contraction of the clock, derived from the Lorentz transformation. But the idea in this section in this article is to infer time dilation from LS invariance (and the Pythagorean theorem) only, in other words, where length contraction is not yet known, let alone the Lorentz transformation. - DVdm (talk) 18:21, 31 August 2020 (UTC)

So you do not understand the calculations after all. Someone should publish the research for the general case first. Thank you for your time . 84.120.7.178 (talk) 22:55, 31 August 2020 (UTC)

Yes, someone should publish the research for the general case first, generating a wp:primary source—that Misplaced Pages does not really want. As soon as that primary source is discussed and cited in the established literature, there will be wp:secondary sources establishing the noteworthyness of the research—which is what Misplaced Pages really needs, by design. So patience is what you probably need here. And some luck. - DVdm (talk) 23:07, 31 August 2020 (UTC)

I still believe the section could be improved now. I would add this sentence to the end:

In this reasoning, L is perpendicular to v; thus, it is not affected by length contraction.

Then I would remove length contraction from "See also". 84.120.7.178 (talk) 23:10, 1 September 2020 (UTC)

The reasoning does indeed not depend on length contraction, but neither does it depend on relativity of simultaneity, or on temperature or on atmospheric pressure . But all that is irrelevant in the context of the section. Remember, the section is about inference of a phenomenon (time dilation) from first principles (light speed invariance). Bringing in length contraction here would be wp:original research, and even with a source, it would still be a school book example of wp:synthesis. Unless of course you find a source that —in the context of this particular reasoning— states that LC is not applicable due to the perpendicularity of the clock. None of the four cited sources mention this. The see also entry for length contraction is there because length contraction is another consequence of the postulates. - DVdm (talk) 09:14, 2 September 2020 (UTC)

I disagree with your argument, but do as you wish. You are negligibly benefiting the not-so-smart reader at the expense of not heavily penalizing the smart one. If you had some people reading that section, you would understand my suggestion. Thanks again. 84.120.7.178 (talk) 04:50, 3 September 2020 (UTC)

This explanation of what SYNTH is not may be useful to editors with time travel capabilities. 84.120.7.178 (talk) 08:30, 4 September 2020 (UTC)

Is this source good enough 4U? 84.120.7.178 (talk) 09:35, 5 September 2020 (UTC)

I hadn't seen that before and it looks correct, thanks for sharing. It is not widely cited () but it is indeed a nice thought experiment to independently infer both length contraction and time dilation from first principles. It is of course a different thought experiment (with a more complicated physical setup) than the usual standard "vertical" clock. Perhaps we can include a little sourced remark at the end of the subsection. Something along the lines of this: "In a thought experiment using a square light clock, both time dilation and length contraction can be independenly infered from fist principles.

References

1. Galli, J. Ronald; Amiri, Farhang (2012). "The Square Light Clock and Special Relativity" (PDF). AAPT. 50. American Association of Physics Teachers: 212. doi:10.1119/1.3694069. Retrieved 5 Sep 2020.

Afaiac, go ahead... - DVdm (talk) 11:01, 5 September 2020 (UTC)

I would also like to include the part that compares a vertical clock to a horizontal one. I will edit the article later. 84.120.7.178 (talk) 08:40, 6 September 2020 (UTC)

I have added the remark: . For the horizontal clock we need a source. And, of course for a comparison with the vertical clock, we need another source. To make sure we don't anything wp:UNDUE, let's first discuss before we add anything here. - DVdm (talk) 09:13, 6 September 2020 (UTC)

Note, actually, I think that the addition I just made, might be borderline undue—as in hardly covered in the relevant literature—so I undid that (). I think the section is sufficiently complete. Any addition about different types of light clocks would only add needless complication and would surpass the intention of the section. Others, feel free to comment. - DVdm (talk) 09:29, 6 September 2020 (UTC)

You requested a source. I presented you one that supports the comparison explicitly. Are you telling me now that one reliable source is not enough? 84.120.7.178 (talk) 00:29, 7 September 2020 (UTC)

The only things the source says about the vertical clock, are "A thought experiment that includes a square light clock is similar to the traditional vertical light beam and mirror clock, except it is made up of four mirrors placed at a 45 angle at each corner of a square of length L0, shown in Fig 1." and "The traditional “vertical light clock” and “horizontally moving train” are combined into a single device where the horizontal length of the square light clock is measured independent of time dilation." I.m.o. these are just an introductory statement and a remark, and not really much of a comparison. And again, there are tons of sources for the vertical clock, but just this one (with its few independent cites) for a square clock, and none for the horizontal clock. So I think mentioning it in the context of this section in this article is a bit wp:UNDUE. - DVdm (talk) 10:16, 7 September 2020 (UTC)

Perhaps the article would be best placed in the "Further reading" section. Regardless of how the analysis/comparison turns out, because of the relativity of simultaneity a horizontal light clock in the same frame and spatial location and with the same period as the vertical light clock must exhibit the same time dilation. A comparison might be interesting as a physics exercise, but the result has to be the same in the end, so I agree that a mention in this article would appear as undue weight. --FyzixFighter (talk) 13:39, 7 September 2020 (UTC)

I do not suggest including any physics exercise, but the result you are trying to describe. It is not undue weight. 84.120.7.178 (talk) 02:40, 8 September 2020 (UTC)

• I do not want to talk about square clocks. Please read the source, page 212, paragraph The assertion that T_V = T_H follows from the first principle. 84.120.7.178 (talk) 02:40, 8 September 2020 (UTC)

Yes, T_V = T_H. I don't see how that would be helpful or clarify anything in the context of the section. - DVdm (talk) 08:56, 8 September 2020 (UTC)

I asked you to read the paragraph. I will edit the article in order for you to see the proposal. 84.120.7.178 (talk) 03:45, 9 September 2020 (UTC)

Here is the proposal. 84.120.7.178 (talk) 04:35, 9 September 2020 (UTC)

Ok, unless anyone else objects, I have no problem with that. - DVdm (talk) 09:53, 9 September 2020 (UTC)

It is settled then. Thank you. 84.120.7.178 (talk) 01:05, 11 September 2020 (UTC)

Rescue section "Time dilation in popular culture"

This section would be good for the article to be broad in its coverage, but only if there are secondary sources. List of time travel works of fiction mentions time dilation without references. Planet of the Apes (1968 film), The Ice Pirates, and Andromeda (TV series) do not mention it. Flight of the Navigator, Time Trap (film), and Gunbuster mention it without references. Interstellar (film) has one reference from Jean-Pierre Luminet.

Thus, I would add this small section with the source for Interstellar. I would also move here the sentence about fiction from the lead section. 84.120.7.178 (talk) 08:11, 12 September 2020 (UTC)

This other source if from The New York Times. 84.120.7.178 (talk) 08:34, 12 September 2020 (UTC)

This source is recent. It is from Inverse (website) regarding Time Trap. 84.120.7.178 (talk) 08:50, 12 September 2020 (UTC)

One from North by Northwestern and another one from BBC regarding Interstellar. 84.120.7.178 (talk) 09:10, 12 September 2020 (UTC)

One from Den of Geek that also mentions Planet of the Apes and another from Scientific American and Jon Spaihts about Passengers (2016 film). I think this section is justified. 84.120.7.178 (talk) 09:30, 12 September 2020 (UTC)

For the record, this edit was no Easter egg; look at the source. 84.120.7.178 (talk) 23:40, 28 September 2020 (UTC)

I have looked at the source. Nothing in it warrants a hidden, piped link of the page number, "42", to 42 (number). I have never seen this done for any other reference. Also, this seems contrary to MOS:EGG (hence why I called it an "easter egg"). What is the purpose of linking the page number to 42 (number)? What in the source warrants that hidden, piped link? --FyzixFighter (talk) 00:01, 29 September 2020 (UTC)

"I cannot say what it is" 84.120.7.178 (talk) 00:30, 29 September 2020 (UTC)

Regarding this edit, I would like to point out that I generally use references from sources already present in Misplaced Pages. 84.120.7.178 (talk) 22:55, 30 September 2020 (UTC)

Not a good idea. It's not because a bad source (a blog) is used somewhere, that it can be used again. Read some thoughts about this in wp:otherstuffexists, so I undid the edit. As a bad wp:primary source, blogs are at best just someone's personal, irrelevant opinion. And the replies shouldn't even be looked at. - DVdm (talk) 23:24, 30 September 2020 (UTC)

I disagree: it is a good idea when combined with other reasons. 84.120.7.178 (talk) 23:40, 30 September 2020 (UTC)

IMO, DVdm is correct. Context matters for sources, especially for blogs and other self-published sources. If Regehr were a known expert on modern science fiction literature, WP:SPS might allow it; or if this were an article on compiler correctness or undefined behavior or on Regehr himself, it might as well. However, I don't see how his blog for this article fits the allowed exceptions of WP:SPS. --FyzixFighter (talk) 01:55, 1 October 2020 (UTC)

... because science fiction writers know more about physics than computer science professors. 84.120.7.178 (talk) 12:05, 1 October 2020 (UTC)

I have finished this section. Expansion should focus on new media, like theater plays or paintings, rather than adding more than three examples per medium. Interstellar and Tau Zero are exceptions because of their coverage; perhaps someone can find similar coverage for other works. 84.120.7.178 (talk) 22:15, 9 October 2020 (UTC)

• Extraordinary claims need a secondary source (t · c) buidhe 04:48, 23 October 2020 (UTC)

Time contraction

Regarding this reversion, what is this arXiv excuse? What is wrong with a source from American Journal of Physics? 84.120.7.178 (talk) 21:00, 11 October 2020 (UTC)

Every once in a while, a bad paper slips through the review process. J. H. Field is a respected experimental physicist who, unfortunately, has turned his hand to theoretical work, publishing in arXiv a series of fringe articles. In arXiv:1405.5174, he says that the Hafele-Keating experiment was incorrectly analyzed and that length contraction is false, thus resolving the Ehrenfest paradox. In arXiv:1307.7962, he claims that length contraction is spurious. In arXiv:1210.2270, he claims that relativity of simultaneity is unphysical. In arXiv:0811.3562, he claims that the conventional analysis of the twin paradox is full of holes. Naturally, he has self-published (arXiv:physics/0612041) an "Einstein was wrong" paper. And so on and so forth. He also has a lot of fringe stuff in arXiv on quantum mechanics. Prokaryotic Caspase Homolog (talk) 22:15, 11 October 2020 (UTC)

... which is one of the many reasons why WP:Reliable sources/Perennial sources says that "arXiv is a self-published source, and is generally unreliable..." - DVdm (talk) 08:09, 12 October 2020 (UTC)

I rephrase the question: On what grounds an article from J. H. Field that is published in American Journal of Physics is deemed as unreliable? 84.120.7.178 (talk) 11:34, 12 October 2020 (UTC)

By reason of the fact that a consensus of Misplaced Pages editors consider it so. WP:RELIABLE provides guidelines, which are interpreted and enforced by Misplaced Pages editors in a consensus process. You will find not find it possible to overturn this consensus, so I would advise you to just drop the matter. Prokaryotic Caspase Homolog (talk) 13:41, 12 October 2020 (UTC)

Really? By WP:CCC, I request that you point me to the discussion which establishes that an article from J. H. Field that is published in American Journal of Physics is unreliable. 84.120.7.178 (talk) 14:00, 12 October 2020 (UTC)

This is the discussion. I consider the article, by a known fringe contributor to arXiv, to be unreliable. DVdm also considers it to be unreliable. I suspect that you have some personal stake in seeing the reverted material going into Misplaced Pages, in which case, WP:CONFLICT may bear on this topic. Prokaryotic Caspase Homolog (talk) 15:07, 12 October 2020 (UTC)

Not much to be found on the topic: Google Books: mostly off-topic, other wp:FRINGE, so definitely wp:UNDUE here. - DVdm (talk) 16:02, 12 October 2020 (UTC)

For the record, I also consider articles by a known fringe contributor (in this case J. H. Field) published at arXiv to be unreliable. Coldcreation (talk) 17:00, 12 October 2020 (UTC)

I ask for the last time here: What does arXiv have anything to do with American Journal of Physics? 84.120.7.178 (talk) 17:15, 12 October 2020 (UTC)

As I stated before, occasional mistakes happen in the review process, and bad papers do get published in reputable journals. That is one reason why Misplaced Pages also includes recommendations to avoid primary sources whenever possible, but to instead use mainly secondary sources so that primary source material can be put into proper context.

We have so far, without any attempt at "canvassing" on my part, three editors (including me) who agree that material based on J. H. Fields' work should not be in Misplaced Pages. It will not be allowed in, so give it up. Prokaryotic Caspase Homolog (talk) 18:47, 12 October 2020 (UTC)

So you are implying that this source from Am. J. Phys. is unreliable without any reliable source proving this is the case indeed. I propose a compromise: I will use conditional tense, like "Time contraction would be a similar special relativistic effect", to soften the certainty of the claim. If you disagree and feel we have discussed enough, I will continue to the dispute resolution noticeboard. 84.120.7.178 (talk) 23:35, 12 October 2020 (UTC)

By itself, the unconditional would stack wp:original research on top of an wp:unreliable source, making the edit even worse. - DVdm (talk) 09:00, 13 October 2020 (UTC)

I guess you mean "the conditional would stack". No problem, I will not use conditional. We are not going to reach a compromise. Are we done discussing here? 84.120.7.178 (talk) 14:15, 13 October 2020 (UTC)

Indeed, the conditional, yes. Struck the un. - DVdm (talk) 14:56, 13 October 2020 (UTC)

Note: anon filed Misplaced Pages:Dispute resolution noticeboard#Time dilation without notifying community. - DVdm (talk) 08:59, 15 October 2020 (UTC)

Note: RFC closed: . - DVdm (talk) 21:46, 21 October 2020 (UTC)

It has now been brought to Misplaced Pages:Reliable_sources/Noticeboard#J._H._Field_on_American_Journal_of_Physics. Plumbum208 (talk) 09:18, 22 October 2020 (UTC)

The IP editor has been extremely persistent in the discussion on the Reliable Sources Noticeboard. Prokaryotic Caspase Homolog (talk) 03:12, 29 October 2020 (UTC)

• Misplaced Pages:Fringe theories/Noticeboard#Time contraction --Guy Macon (talk) 19:44, 29 October 2020 (UTC)

RfC on Time contraction

How should we solve the WP:R#PLA in Time contraction? 84.120.7.178 (talk) 22:40, 18 March 2021 (UTC)

• As there is no such thing as time contraction, and as this was discussed here, let's get rid of that redirect. - DVdm (talk) 23:00, 18 March 2021 (UTC)
• From the WP:RFC

Before using the RfC process to get opinions from outside editors, it's often faster and more effective to thoroughly discuss the matter with any other parties on the related talk page. Editors are normally expected to make a reasonable attempt at resolving their issues before seeking help from others. If you are able to come to a consensus or have your questions answered through discussion with other editors, then there is no need to start an RfC.

I have seen no prior discussion on the fate of the redirect Time contraction and the proper place to discuss that is at RfD. Consensus at this page and in related discussions seem to fall against including a mention of the idea in this page. The RFC is beginning to look a bit pointy. --Salix alba (talk): 09:20, 19 March 2021 (UTC)

"Time contraction" listed at Redirects for discussion

A discussion is taking place to address the redirect Time contraction. The discussion will occur at Misplaced Pages:Redirects for discussion/Log/2021 March 18#Time contraction until a consensus is reached, and readers of this page are welcome to contribute to the discussion. DVdm (talk) 23:03, 18 March 2021 (UTC)

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