Talk:Twin paradox/Archive 8

message: This talk page has been semi-protected due to block evasion by a chronically disruptive unregistered editor. DurovaCharge! 15:09, 16 December 2006 (UTC)
replies: text: Semi-protection lifted. DurovaCharge! 17:52, 20 December 2006 (UTC)
thread_title:  Semi-protection 

message: An aquaintance who is a physics major explained to me that the twin in the spaceship would slow his ageing during acceleration, but would regain the lost time during deceleration when arriving back at Earth. Is this accepted theory? If so is it represented in the article? I didn't see it stated simply, if it was there. —The preceding unsigned comment was added by Panserbjørn (talk • contribs) 04:28, 24 January 2007 (UTC)
replies: text: I am afraid that you have misundestood something. The travelling twin remains younger forever according to special relativity. XCelam 05:41, 24 January 2007 (UTC)
thread_title:  Does the spaceship twin catch up upon arrival? 

message: I have uploaded the following article to wikisource:
Dialog about objections against the theory of relativity
This is a translation of the article 'Dialog über Einwände gegen die Relativitätstheorie' by Albert Einstein, published in 'Naturwissenschaften, 1918
In that article the following is discussed: can the Twin scenario be used to expose a self-contradiction in the framework of relativistic physics? Einstein explains why this is not the case.
I emphasize that the aim of the 'Dialog' is not to discuss the twin scenario, the aim is to discuss relativistic physics. The twin scenario is very counterintuitive, and Einstein makes no effort to lessen the experience of counterintuitiveness, no alleviation of the sense of puzzlement. What Einstein is interested in is to address the question whether there is a self-contradiction in relativistic, a self-contradiction that can be exposed with the twin scenario. 
Einstein points out why no self-contradiction can be constructed, and on the basis of that Einstein declares the matter of alleged self-contradiction fully clarified. --Cleonis | Talk 01:12, 25 January 2007 (UTC)
thread_title:  Einstein article 'Dialog' 1918, available on wikisource 

message: Some media have reported that Subhash Kak has "resolved" the twin paradox. All the press releases and related newspaper articles are meaningless. Anyone who would like to edit the time dilation page because of this incident should first read the time dilation page, at least its introductory paragraphs, and the "time dilation" section at the talk page of the Subhash Kak page. There is nothing to "resolve" about the twin paradox. So I encourage everyone to calm down. Also, I have removed the "expert needed" tag from the time dilation page because it satisfies all standards of Wikipedia and doesn't have any major errors or misunderstandings - like embarrassing errors comparable to those found in Kak's press release. Of course, some incremental improvements and perhaps some simplication of the page is needed - but that's the case of other pages, too. Thanks, Lubos Motl, Harvard U., --Lumidek 19:26, 18 February 2007 (UTC)
replies: text: Excellent.  Thanks for the comments.  I do believe you meant to write twin paradox in the three places that time dilation is written above, so you may wish to strike those out and replace them. Tim Shuba 20:10, 18 February 2007 (UTC)

text: I think it is this one. Rasmus (talk) 12:50, 19 February 2007 (UTC)
replies: text: That is essentially correct.  The version as published by the journal is linked from this page, but a subscription is required.  Any differences between the two versions are likely minor.  Tim Shuba 15:01, 19 February 2007 (UTC)
thread_title:  Subhash Kak 

message: Considering that there are about 5 archived pages of discussion concerning this article, it is surprising how little has been done to polish the primary material and make it clearer. I am not specially qualified as a physicist or mathematician, but I have a layperson's interest in the subject, and I'm a good writer and proofreader. Here below are my suggestion for how the first few pars should read. If no one objects, next time I come around here, I will incorporate them, and continue on with the rest. In the meantime, feel free to comment here, or on my page. 
:In his famous work on special relativity in 1905, Albert Einstein predicted that when two clocks were brought together and synchronised, and then one was moved away and brought back, the clock which had undergone the travelling would be found to be lagging behind the clock which had stayed put. Einstein considered this to be a natural consequence of Special Relativity, not a weird paradox as some suggested, and in 1911, he restated and elaborated on this result in the following form: 
:In 1911, Paul Langevin made this concept more vivid and comprehensible by his now-iconic story cum thought experiment of the twins, one of whom is an astronaut and the other a homebody. The astronaut brother undertakes a long space journey in a rocket moving at almost the speed of light, while the other remains on Earth. When the travelling brother finally returns to Earth, it is discovered that he is younger than his sibling, that is to say, if the brothers had been carrying the clocks mentioned above, the astronaut’s clock would be found to be lagging behind the clock which had stayed with the Earth-bound brother, meaning that less time had elapsed for the astronaut than for the other. Langevin explained the different aging rates as follows: “Only the traveller has undergone an acceleration that changed the direction of his velocity”. 
:Langevin means here that while it is doubtless that the twins experienced many things differently to each other in the years they were apart, there was only one event which the astronaut experienced which his brother did not and which had a direct bearing on the time differential between them: the astronaut experienced the acceleration necessary to turn his rocket around and head back to Earth, and his brother on Earth did not.  The significance of the “Twins Paradox” hinges on this one crucial detail of asymmetry between them. (NOTE: Everyday English has "acceleration" as referring to "speeding up" only, but in scientific circles it equally refers to "slowing down" so that all the physical changes in speed and direction necessary to get the rocket to come back - slowing down, stopping, turning around, speeding up again - can be coverered by the umbrella term "acceleration". This is the way the word is used in this article.)
:It should be stressed that neither Einstein nor Langevin considered these deeply counter-intuitive results to be literally paradoxical. A paradox in logical and scientific usage refers to results which are inherently contradictory, that is, logically impossible, and both men argued that the time differential illustrated by the story of the twins was an entirely natural and explainable phenomenon. 
--Myles325a 14:01, 10 April 2007 (UTC)
replies: text: I have now incorporated above pars. How are you loving it so far? Will continue with rest - beginning with the "example" a little later. Comments welcome 
Myles325a 04:27, 14 April 2007 (UTC)
replies: text:  I have not participated for some months, and notice that what now is claimed about Langevin's argument is definitely incorrect (it's for sure not the only error). However, it was almost correct about half a year ago (in fact he did not present them as twins). Often people make changes according to their liking instead of according to the sources. Do you actually have a copy of the article that you paraphrase? Harald88 08:32, 2 May 2007 (UTC)
thread_title:  article needs revision for style, clarity 

message: There was a special Scientific American article of several months ago, actuated by the ongoing controversy over whether the Twin Paradox is a consequence of Special or General Relativity, which gave a detailed and well-graphed account of this problem, noting at the outset that the Twin Parodox could be explained using Special Relativity only, without recourse to General Relativity. I will chase this up. Anyone else rem this? --Myles325a 01:24, 15 April 2007 (UTC)
replies: text: The 1918 article that Cleonis linked here is the oldest mention of the clock paradox; Einstein presented it as a paradox for GRT but not for SRT. And if people mean that the problem can be calculated with SRT, Einstein already showed that in 1905! The main problem is that different people mean different things with the same words. Harald88 08:41, 2 May 2007 (UTC)
thread_title:  Scientific American on twin paradox 

message: I can't think of any reason to not use some simple, round numbers for the twins paradox example. Having decimal points all over the place makes the article difficult to read and understand.
Numbers i'd suggest:
ship velocity = 0.8c
distance from earth to hypothetical nearby point in space = 2.4ly
this makes for much simpler results and therefore discusion:
time passed on ship = 6 years
time passed on earth = 10 years
observed frequency factors = 1/3 and 3
131.227.230.61 13:01, 21 April 2007 (UTC)
thread_title:  why does the example use such complicated numbers?