Talk:Time dilation/Archive 2

message: I think that I would like it better if it did not make this article look more like a used book store than a well organized article.  I won't contest its restoration, but this article needs to have someone "take the bull by the horns" and really redo it a ways.  (I regret that I am too busy for that at this time.) --EMS | Talk 06:00, 27 October 2005 (UTC)
thread_title:  Restoration of Eitology section 

message: Is the idea that at the speed of light no time passes and time travelled = distance in light years? So if you travelled to the end of the universe (15 billion light years) at light speed it would seem instantaneous for you, but you would arrive in 15,000,002,005 AD ??? Astrokey44 11:29, 2 December 2005 (UTC)
replies: text: They seem to only talk about speeds which approach light speed, what about travelling at light speed itself. looking through that led me to this table from an older version of the page, would this be any use in the current article? Astrokey44 14:41, 2 December 2005 (UTC)
thread_title:  question 

message: It says now: "Time dilation is the phenomenon of proper time passing at a different rate for a remote and/or moving object than it does locally. " That's certainly not yet optimal, for here "proper" and "local" mean effectively the same thing, similar to writing "local position is measured far away at a different location than locally".
That may be an improvement, but I'm sure we can do better than that. For example:
"Time dilation is the phenomenon of time passing at a different rate for a remote and/or moving clock than it does locally and/or in rest." 
or, IMO again better:
"Time dilation refers to the phenomenon that the proper time rate of a remote and/or moving clock differs from that of a reference clock."
Cheers, Harald88 18:28, 12 December 2005 (UTC)
replies: text: Regretfully, I find the last proposal insufficient: in the phrase
"Time dilation is the phenomenon of proper time being observed to pass at a different rate for a remote and/or moving object than it does for the observer", 
the words "observed" and "observer" may cause confusion. On top of that, "observer" is jargon that risks to be interpreted at face value, causing considerable misunderstandings. Thus I'll do an attempt to do better. Harald88 08:35, 13 December 2005 (UTC)

text: I think that you have done a good job of capturing the essense of my sentence, so I will not quibble.  You are however quite right that proper time needs to be mentioned here somehow.  (At the least we have gotten beyond the weird edit whereby the into was talking about "accelerated clocks".) --EMS | Talk 19:15, 13 December 2005 (UTC)
thread_title:  "proper time locally" 

message: In my previous entry I used the expression 'accumulation of time dilation'. That needs some clearing up, I think.
In the case of time-dilation-in-transversal-motion (depicted in the GIF) there is not a one-on-one relation between red proper time and green proper time. The situation is symmetrical however; red is to green what green is to red. What is compared in the GIF is rate of lapse of proper time, and the determining factor is relative velocity. 
In the a-symmetrical case of one space-ship in inertial motion, and another space-ship using rocket thrust to circle around it, there is a non-symmetrical time dilation and consequently a buildup of difference in amount of elapsed proper time. For difference in amount of elapsed proper time the determining factor is difference in pathlength.
Earlier I glossed over that by using the expressions 'less lapse of proper time' and 'more lapse of proper time', not specifying whether it referred to 'comparative rate of proper time' or 'amount of proper time'.  
Presumably the symmetrical time dilation and the a-symmetrical time dilation are different aspects of the same thing, but I find it not straighforward to envision how they are related. The a-symmetrical time dilation is still somewhat intuitive, it's the symmetrical time dilation that boggles the mind. 
I concentrated on the symmetrical case because (1) the muon example (2) generally, symmetry is the physicist's best friend. --Cleon Teunissen | Talk 12:39, 16 December 2005 (UTC)
replies: text: There is in principle no difference between "symmetrical time dilation" and "a-symmetrical time dilation": they are both calculated with the same equations, relative to inertial frames. Harald88 12:50, 16 December 2005 (UTC)
thread_title:  Rate versus amount of lapse of proper time 

message: I copy and paste from above:
:I don't know if it's much of a reference, since I wrote it, but the math you deleted the first time I edited this page about 2 months ago, which I've seen in several reputable sources, states that the GPS system's time dilation is a combination of 3 factors, SR, GR and something I am wholely unfamilar with, the Sagnac effect. Jok2000 20:34, 16 December 2005 (UTC)
thread_title:  Time dilation aspects of the GPS technology