# Talk:Time dilation

Time dilation was a good articles nominee, but did not meet the good article criteria at the time. There are 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.
 December 16, 2006 Good article nominee Not listed

## 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)
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)

## Overly verbose - and generally poorly worded

This article is likely to scare away any people coming to learn and understand the concepts. I was thinking that maybe I was being picky, but then I read the Plato reference. Yes, Plato understood that something about you relative to me isn't the same as that thing relative to the planet Earth. Relative to you, this may seem very clever. Relative to everyone else on the planet, it just looks like a hopeless attempt at intellectualism.

I will take some time to re-write some of this article tomorrow. I hope that this does not offend anyone emotionally attached to childish wordings, but I am sure that it will vex me little if it does. Jimadilo (talk) 22:56, 23 November 2016 (UTC)

I second your comments. They apply to the Special Relativity pages as a whole. Good luck with your edits. Watch out for the editors though; they are fond of pranking the new girl, in my experience. I've been quite put off attempting to make further improvements for lay readers. They're not supposed to do that - it's against Wikipedia policy. I'm thinking about lodging a formal complaint. The more edits they've made in the history, and the fewer words they use in their replies, the worse they're likely to be, IMHO. Some will even treat you kindly then trip you. Double standards abound. Unless a reader already knows the subject intimately - by which I mean a doctorate in both Maths and Physics - the overall quality of the whole Special Relativity site is just dreadful at the moment. Maybe that's how they like it; a little self-appointed coterie that defends an inaccessible high castle of knowledge. I've seen little to suggest otherwise. I could have written a much more caustic post than this. Knowledge is for everyone. You won't find it here. Beware. Happy Friday 13th. Kebl0155 (talk) 17:48, 13 January 2017 (UTC)

## Re: chapter Relative velocity time dilation

The figure chosen to illustrate time dilation from a special relativity point of view, is irrelevant. As far as I know, time is running faster here on Earth than at the surface of Sun. The red object is simply not running in an inertial frame ..(you didn't think of that, eh?).. ! I will return later to remove this figure if that has not already been done. Hilmer B (talk) 20:18, 16 February 2017 (UTC)

The figure is not necessarily gravity related, so the difference between Earth and Sun is not relevant in the context of special relativity. Moreover, moving inertially is not required in special relativity: see, for instance, Acceleration (special relativity) and Non-inertial reference frame. As seen from the inertial blue dot, the red object is running at contant speed anyway, so in this case the calculation of the integrated red proper time is simple: ${\displaystyle \Delta \tau _{red}=\int {\sqrt {1-(v(t_{blue})/c)^{2}}}\ dt_{blue}=\int {\sqrt {1-(v_{blue}/c)^{2}}}\ dt_{blue}<\int dt_{blue}=\Delta t_{blue}.}$ See also {[1], [2], [3]} etc. I have added a source for the image caption: [4]. - DVdm (talk) 22:34, 16 February 2017 (UTC)

## Due to relative velocity symmetric between observers

This chapter seems rather complicated, just to explain that for everyone, i.e. the very fast moving person and the relative stationary observer, the "other" clock looks like it's going slower than his/her own. Wouldn't it suffice to say, that for the fast moving person it seems like that it's just the entire rest of the universe, that is moving very fast, while he/she is stationary - thus all the clocks in the universe are going slower than his/her own clock...?! --Xario (talk) 21:57, 27 March 2017 (UTC)

That would be misleading, since clocks aren't really "going slower", and certainly don't "look like they are going slower". For instance, due to the Doppler effect, an approaching clock can actually look like it's going faster than the own clock. Careful measurements will indicate that calculated local time between ticks of moving clocks is longer that what the moving clock suggests. That is usually sloppily called "running slow" or "looking like running slow" or "appearing to run slow"—short, but not quite correct. The section does not directly explain all this, but seems to be careful enough not to be sloppy about it. - DVdm (talk) 06:59, 28 March 2017 (UTC)
Sorry, ok, but my point was the explanation of the symmetry. --Xario (talk) 07:08, 29 March 2017 (UTC)

## Time dilation Triangle

According to the article:

From the frame of reference of a moving observer traveling at the speed v relative to the rest frame of the clock (diagram at right), the light pulse traces out a longer, angled path - apothem. Thus the base of the time dilation triangle is AA=s=vt’ where t’ is dilated time.

The velocity of the moving frame relative to the stationary frame is v in time t where t is not dilated. Assume both mirrors of the light clock are permanently attached to the ceiling and floor respectively inside of the moving frame. This means mirrors also move at v in time t (where t is not dilated) relative to the stationary observer.

The spatial distance covered by the moving frame at any time t is s=vt (where t is not dilated) relative to the stationary observer. This means

The spatial distance covered by mirrors of the moving frame is also s=vt (where t is not dilated) relative to the stationary observer.

Since the aforementioned distances (s=vt’ and s=vt) are not equal therefore what would be the real position of mirrors or any stationary object inside the moving frame relative the stationary observer.2001:56A:7399:1200:7CEE:C3BC:325E:2345 (talk) 18:34, 27 April 2017 (UTC)eek

Please note that article talk pages are for discussions about article additions/changes/removals, and not for discussions about the subject—see wp:Talk page guidelines. You are welcome to ask content-related questions at the wp:reference desk. Good luck there. - DVdm (talk) 18:44, 27 April 2017 (UTC)