Talk:Time dilation/Archive 2017

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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: $\Delta \tau _{red}=\int {\sqrt {1-(v(t_{blue})/c)^{2}}}\ dt_{blue}=\int {\sqrt {1-(v_{blue}/c)^{2}}}\ dt_{blue}<\int dt_{blue}=\Delta t_{blue}.$ 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)

Partly undone

I have partly undone these edits for the following reasons:

• "internal mechanics of the clocks becoming deranged" back to "technical aspects of the clocks" because clocks don't have to be mechanical. Particle decay statistics can be used as a clock, and we have no knowledge of there being some internal mechanics in them.
• "from the propagation velocity of light signals (a constant) between sources differing" back to "nor propagation time of signals" because of (1) awkwardness of expression, and (2) the point is not that the speed of the signals is constant, but that the distance they travel is not constant, and that this is taken into account.
• "299,792,458 m/s, or 187,000 miles/sec approx." back to "299,792,458 m/s", because one is exact in m/s, where the other is approx in miles/s, which amounts to comparing apples with pears.
• "further" back to "farther" because "further" was correct per [5] and [6].
• I kept one instance of "local" and changed instance of "the clock" to "this clock".

- DVdm (talk) 08:22, 29 May 2017 (UTC)

I don’t think you will get a response from apologist with brain because time dilation concept (equation) is derived from the simplest mechanical light clock. Also, it is the mechanical clock, which confirmed the TD as mentioned in the article.

Earlier scientists (Einstein) never said, “This effect arises neither from technical aspects of the clocks nor from the propagation time of signals, but from the nature of spacetime” or “clock doesn't have to be mechanical”

Don’t mislead the Wikipedia users.

Wikipedia rules apply to all, therefore, leave the originality of the article, which is still official.

Either cede or create a separate page for your own wizardry on Wikipedia if they allow you or somewhere else. Good Luck 2001:56A:7399:1200:7C16:4242:EBEF:37CB (talk) 00:12, 2 August 2017 (UTC) EEK

Contradictory statements

The opening paragraph states, "a clock that's at rest relative to an observer will be measured by him to tick at a SLOWER rate compared to that of a subject that's in motion relative to him ..." The first sentence in the "Velocity time dilation" section states, "a clock that's stationary relative to him will be measured to tick FASTER than a clock that's in motion relative to his frame of reference." I have capitalized the words SLOWER and FASTER to emphasize the contraditions. The word SLOWER in the opening paragraph is wrong and should be changed to FASTER. Mitguy (talk) 18:01, 3 August 2017 (UTC)

Yes. I made a few changes, making sure not to use the word faster. After all, in an article about time dilation we prefer the word slower: [7]. - DVdm (talk) 18:16, 3 August 2017 (UTC)

The correct time dilation

Here the correct time dilation:

$\Delta t'=\Delta t\cdot {\sqrt {1-{\frac {v^{2}}{c^{2}}}}}.$

This is wrong:

$\Delta t'={\frac {\Delta t}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}.$

— Preceding unsigned comment added by 176.198.150.23 (talk) 06:52, 6 October 2017 (UTC)

Please sign all your talk page messages with four tildes (~~~~) — See Help:Using talk pages. Thanks.

The second equation pertains to two events happening at the same place in the unprimed reference frame ($\Delta x=0$), such as two ticks on a clock at rest in that frame. The first equation (yours) pertains to two events happening at the same place in the primed reference frame ($\Delta x'=0$), such as two ticks on a clock at rest in that frame. These are two different physical situations. Both are used in books, and it doesn't really matter which one is chosen, as long as the actual situation is clearly specified. The circumtances and the meanings of the variables are explicitly and carefully explained and specified in the article. And properly sourced.

Also note that, in order to actually express a dilation, your equation should be turned around to $\Delta t={\frac {\Delta t'}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}.$. Otherwise it would show a shortening. Our article is about time dilation. - DVdm (talk) 08:05, 6 October 2017 (UTC)

Some suggestions.

I am back , for only a short time.

I never understood why you rejected the source (http://fermedesetoiles.com/documents/supports/le-paradoxe-des-jumeaux.pdf) by Levy-Leblond ? You know , even in France we have some good physicists ...

Well , let us make some observations.

1/Simple inference of of velocity time dilation.

The moving observer observes the fixed clock. But that says nothing about the same clock which the same observer could transport which him. I say that these transported clock would tic at the same rate than the fixed clock. That is predicted by the very first rule of relativity !

Definitively , we have just only established the Lorentz formula for a short interval !

2/Reciprocity.

I think it is a very bad idea to show a Loedel Diagram to illustrate that notion. In the contrary it is very easy to demonstrated the true general case.

If $e_{0},e'_{0}$ are the two time unit vectors , we have :

$e_{0}.e'_{0}=\gamma =(1-v^{2})^{-1/2}$

$t=\gamma t'$

$\gamma t''=t'$

where t and t" are the (two) times simultaneous in the $e_{0}$ frame , to t' in the $e'_{0}$ frame.

It would be easy to draw a nice figure ! By the way it is not an effect of perspective , but an effect of parallax.

3/Proper time and Minkowski diagram.

For the same reason the left figure is awful. There is no need to demonstrated the minimum propriety with so clumsy an argument ! I suggest to comment only the twin paradox figure.

4/You should add some short comment of principles of chrono-geometry (refering to Levy-Leblond ,page 34)

Cordially.Chessfan (talk) 10:55, 1 November 2017 (UTC)Chessfan (talk) 16:37, 2 November 2017 (UTC)