Talk:Time dilation/Archive 2016

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OMG

I cannot believe my eyes, such a simpile theoretical physics lecture about the time dialation effect made not understandable. So sad... Anonamous guy (talk) 03:29, 21 January 2015 (UTC)

There is always the Simple Wikipedia if you need [1]... Tetra quark ^{(don't be shy)} 03:43, 21 January 2015 (UTC)

Well, if I got it right from the diagram curves, you won't be getting any major time savings on a long space trip unless you're travelling at least at half the speed of light, preferably more than that. :> 83.251.170.27 (talk) 09:52, 11 February 2016 (UTC)

Graph of Time Dilation For Satellites

A fairly minor change but I feel it would be best in the caption of the graph to mention that this is under the Schwarzschild metric. Calculating it more accurately with the Kerr metric actually introduces a pretty non-negligible difference. For an example the point where the gain is 0 in the Schwarzschild metric is 1.497 as stated in the caption, but in the Kerr metric for the Earth this becomes 1.364. 77.98.17.0 (talk) 13:23, 22 May 2016 (UTC)

 Done: [2]. I'm surprised that the difference is that large, by the way. - DVdm (talk) 14:38, 22 May 2016 (UTC)

You're correct, the difference actually is nowhere near that large, I was in error. They are actually the same to more than 16 decimal places. Oops! My apologies. 77.98.17.0 (talk) 16:34, 22 May 2016 (UTC)

No problem . I was just about to go check myself. Thanks for letting me know. We can of course leave the mention in the caption. - DVdm (talk) 17:50, 22 May 2016 (UTC)

On the same note though, I feel that this article could really be improved by a mention of how time dilation differs in other metrics. As it reads now it heavily implies that time dilation is purely affected only by the mass of a gravitating body and distance to it, and the velocity of an observer. I feel at least a mention that the Schwarzschild metric isn't the full story of time dilation would be appropriate and helpful. I've very quickly re-plotted the graph shown in this article for time dilation of satellites, but animated it as the rotational velocity of the Earth is increased ( https://www.youtube.com/watch?v=qHRLubYcWGs&feature=youtu.be ) and compared Kerr, Schwarzschild and Minkowski. I feel something similar to this could improve this article. 77.98.17.0 (talk) 22:00, 22 May 2016 (UTC)

Very nice indeed. Alas, per wp:NOR, I'm afraid we can't include that in Wikipedia, unless of course there's a mention of something similar in the literature somewhere. Probably not, right? - DVdm (talk) 06:27, 23 May 2016 (UTC)

I agree, I definitely don't think that video should be added, it's just something I made quickly to give an impression of what I mean. I'm not sure exactly what would be appropriate for this page, but I definitely believe there should be atleast a brief mention that there is more to time dilation than the schwarzschild metric. 77.98.17.0 (talk) 01:15, 24 May 2016 (UTC)

Pages 178 and 179 of this have some interesting remarks.

Perhaps what follows to p 307 of this shows a result. By changing the page parameter we can read page by page up to p. 310 (308, 309, 310), and then there's a remark about time dilation on p 321. Not much though.

I'll check my copy of EBH later today. The book's essential purpose it to explore the consequences of the Schw metric, but it has a chapter on rotating black holes. Perhaps there's something useful. - DVdm (talk) 07:47, 24 May 2016 (UTC)

Checked the chapter (aka Project F) in EBH. Lots of interesting stuff, but no direct mention of time dilation. - DVdm (talk) 19:28, 24 May 2016 (UTC)

Error in the overview of formulae.

With a simple drawing in Minkowsti-space you will see that the observer for which the events are co-local must be the moving observer. Thus the entire section should be reformulated . Chessfan (talk) 20:07, 26 July 2016 (UTC)

In the section Time dilation#Overview of formulae the so-called "moving observer" (who uses primed time coordinate t' ) is assumed to be moving with respect to an observer (who uses unprimed time coordinate t) for whom two clock tick events are co-local, just like in in the section Time dilation#Simple inference of time dilation due to relative velocity, which has 4 solid reliable sources. That means that for this "moving observer" the two relevant events are not co-local. - DVdm (talk) 20:25, 26 July 2016 (UTC)

Note_1: in the latter section I have replaced ([3]) the two images with one image that does a better job at clarifying the chosen setup. - DVdm (talk) 21:21, 26 July 2016 (UTC)

Note_2: drawing a Minkowski diagram is not straighforward in this case, since with respect to the mirrors, the light signal is moving here perpendicularly to the "moving observer". This would require a two-dimensional projection drawing of a 3-dimensional (t,x,y) space. Not simple. - DVdm (talk) 21:41, 26 July 2016 (UTC)

I had this drawing in mind. It permits also to exhibit the unit vectors, that is the unit clocks. Do not tell me , that is personnel work. It is pure application of the principles of relativity.--Chessfan (talk) 06:46, 27 July 2016 (UTC)

Here the events are co-local in the "primed frame", so that would deviate from the text. It also has irrelevant information (the hyperbola, the unit vectors, the choise of the variable η) that would require too much additional explanation in the text. Wouldn't be helpful here; i.m.o. - DVdm (talk) 08:49, 27 July 2016 (UTC)

The addition of speeds of material objects and light.

Ref. Annalen der Physik 17, 1905, p.891-921, A. Einstein, Zur Elektodynamik bewegter Koerper.The original publication of the Special Relativity Theory. On pages 896-897 Einstein describes a thought experiment in which he measures the length of a moving material beam by sending a light signal from one end of the beam to the other end where the light is mirrored back to the source point, and measures the time reqired for the light return trip. This is done twice, the first time by an observer travelling with the beam and the second by an observer in the frame at rest. The second observer sees a light speed of c + v if beam and light travel in the same direction, and of c - v if they are in opposite direction. Time is then measured in the frame at rest.Sootmaker (talk) 15:11, 7 September 2016 (UTC)

Please note that we are supposed to discuss the article here, not the subject—see wp:Talk page guidelines. If you have a problem with (some aspects of) the subject, you can try the wp:Reference desk/Science. - DVdm (talk) 15:36, 7 September 2016 (UTC)

Simple time dilation

I know this mirror set up appears in a number of places and has probably been around a while - probably all taken from here. But I am troubled (OK I'm dopey). It uses Euclidean geometry to explain a non-Euclidean phenomenon. "From the frame of reference of a moving observer traveling at the speed v relative to the rest frame of the clock" - is this contradictory? It seems to me that the photons only trace out a longer path if the mirrors are moving along the line of surface of the mirrors, in which case the mirrors are moving relative to the photons. If the mirrors move orthogonal to the surface they might trace out a shorter path. What if the observer is moving orthogonal to the mirror surfaces.. Even in the set up you have, what about length contraction affecting the paths. It will take a better person than me to work it all out, so congratulations to you for getting this far. I actually have an interest in it because I am trying to write some similar stuff without using spacetime geometry, and to be honest I would rather battle through spacetime geometry. Foucault (talk) 14:46, 25 September 2016 (UTC)

The content that you are referring to is properly sourced in the article by four accessible sources. If you have problems with some of the content, you should ask at the wp:Reference desk/Science. Surely someone will help you there. Here we must discuss the article, not the subect—see wp:Talk page guidelines. Good luck at the ref desk! - DVdm (talk) 14:54, 25 September 2016 (UTC)

I am discussing the article. I am raising legitimate concerns about the example you have used. Just because there are a zillion others who have used the same example, including umpteen YouTubers, does not mean it should not be questioned. What about all the average Joe's who might think the way I do, but just don't bother making an entry on this talk page. Discussing the article includes discussing how it appears to a lay person. After all the section is titled "Simple..." Foucault (talk) 15:47, 25 September 2016 (UTC)

Please indent the messages as outlined in wp:THREAD and wp:INDENT. Thanks.

I have removed your next comment per wp:Talk page guidelines, and put a formal warning on your user talk page. Continuing using this talk page as a forum will get you blocked. - DVdm (talk) 09:46, 26 September 2016 (UTC)

Reverted edits by 178.199.174.242 (talk): Failure to cite a reliable source (HG) (3.1.21)

Shouldn't we add a precision that an earth core 2.5 years younger (some hours older for mountains) is leading to a paradox of alignement with celestial sphere due to (constant) rotation of earth? 178.199.174.242 (talk) 18:34, 3 October 2016 (UTC)

Not without a reliable and relevant source—see wp:verifiability and wp:BURDEN.

Note that one part of a system being younger or older than another part because local clocks are out of synch, is just a statement about local clock rates and total proper time accumulation. Anyway, we cannot discuss that here per our wp:talk page guidelines. We can discuss additions to the article, but for this one we really first need a reliable source. Otherwise we would be discussing the subject and possibly continue arguing about it ad infinitum. Cheers. - DVdm (talk) 18:43, 3 October 2016 (UTC)

OK, I thought it was obvious and didn't needed any source. Thanks. Sincerely. 178.199.174.242 (talk) 18:47, 3 October 2016 (UTC)