Talk:Twin paradox

Section 3

It looks like section 3, "Resolution of the Paradox in Special Relativity", doesn't actually solve the paradox in special relativity - any solution which depends on acceleration uses general relativity. Or do I not understand the proposed solution?

C-14 (talk) 23:14, 27 March 2011 (UTC)

Special relativity can handle acceleration, it's gravity where you need GR.

—WWoods (talk) 23:36, 27 March 2011 (UTC)

Specific Example

In the specific example, the traveler did not calculate the time elapsed in earth using the reference frame of the spaceship. The example suggests that the earth moves at the same speed backward measured in the reference frame of the spaceship. If time elapsed on earth is calculated by the travelers, it will be 2.57 years, half of the time elapsed on the spaceship due to time dilation, which is inconsistent with what the people on earth calculated. So I think this is not a good example. Light Ng Jen Foong (talk) 04:50, 23 April 2011 (UTC)

The people on Earth understand that when 5.14 of their years have passed, the spaceship is at the turnaround point. But it doesn't APPEAR that way because it takes much longer for all of the red-shifted images to get there. Shiggity (talk) 22:57, 2 August 2011 (UTC)

In the paragraph below it is not how the crew calculates their particulars but how their particulars look from Earth so it is wrong: "The ship's crew members also calculate the particulars of their trip from their perspective. They know that the distant star system and the Earth are moving relative to the ship at speed v during the trip. In their rest frame the distance between the Earth and the star system is \epsilon d = 0.6d = 2.4 light years (length contraction), for both the outward and return journeys. Each half of the journey takes 2.4 / v = 3 years, and the round trip takes 2×3 = 6 years. Their calculations show that they will arrive home having aged 6 years." — Preceding unsigned comment added by 24.254.85.164 (talk) 00:59, 26 November 2011 (UTC)

Unacceptable original research

Michael Fontenot (talk · contribs · deleted contribs · logs · edit filter log · block user · block log) is repeatedly inserting original research into this article. His claim that two papers, namely Dolby & Gull and Minguzzi are alternatives and are in conflict is not supported by reliable secondary sources. Not only that, he's wrong in his personal interpretation. Dolby & Gull specifically states (e.g. just before the conclusion) that the result is independent of the coordinate frame chosen. Minguzzi never uses any non-inertial coordinate frame in the cited paper.

It is certainly a conflict of interest and perhaps an ethical breach that Michael Fontenot seems intent on edit warring to include his personal paper from a questionable source (Physics Essays). All of his original research should be summarily rejected from this article. Tim Shuba (talk) 00:19, 14 August 2011 (UTC)

• Note: an expanded version of the same material has been posted at The CADO Reference Frame for an Accelerating Observer and is currently the subject of an AfD here. andy (talk) 00:41, 14 August 2011 (UTC)

(My response to Shuba and Smith):

  

In each of the three references (Dolby&Gull, Minguzzi, and Taylor&Wheeler) that I have cited, in the subsection "Reference frames without fictitious gravitational fields, for the accelerating twin" (which I have added to the "Twin Paradox" Wiki article), the authors explicitly provide their answer to the question: "How does the home-twin's age change, according to the traveler, as the traveler's trip proceeds?". Any rational person reading those references cannot fail to conclude that those authors' three answers are all different. It is absurd to contend that some additional published source is needed, in order to reliably come to that conclusion.

In the section preceding my added subsection, there is a reference cited (Einstein, 1918) which gives the "gravitational time dilation" determination of the traveler's viewpoint. That reference answers the above question with the same answer that Taylor&Wheeler give, although the approach used in Einstein-1918 to get that answer is quite different (fictitious gravitational fields are utilized).

My CADO reference (which I cited in the subsection I added to the "Twin Paradox" article) explicitly gives the same answer that both Taylor&Wheeler and Einstein-1918 got: all three of those references say that the home-twin's age will change abruptly during the traveler's abrupt turnaround.

Dolby&Gull, and Minguzzi, clearly do not get that answer: they say that the home-twin's age changes only gradually, over a prolonged period of the trip, even when the traveler's turnaround is instantaneous. But they disagree with one another about how that gradual "her age versus his age, according to him" curve is shaped.

Michael Fontenot (talk) 16:53, 14 August 2011 (UTC)

The reason I provided links to the arXiv abstracts for the two papers above is so people can check for themselves the veracity of Michael Fontenot's absurd claims. In neither of those papers is anything mentioned about "how does the home-twin's age change, according to the traveler, as the traveler's trip proceeds". This is a fantasy made up out of whole cloth. There is nothing contradictory among Munguzzi, Dolby&Gull, and Taylor&Wheeler. Furthermore and more important for the article, there is no reliable secondary source which says so. This, along with the other blatant fabrications introduced by Michael Fontenot, should be removed, and no mention should be made here or anywhere else in the encyclopedia of his uncited paper from the unreliable source Physics Essays, which has failed for over 10 years to generate the slightest interest from professionals in the field. Tim Shuba (talk) 23:24, 14 August 2011 (UTC)

simple diagram

Consider adding a diagram like this one: http://www.anselm.edu/homepage/dbanach/st10.jpg no fancy colors or animation needed, this is simple and very clear

Can the intro be simplified or explained better?

As a non-expert, the intro doesn't really make sense. I think there should be some explanation added as to why that would happen. Or is it just inherent to Einstein's theory? in which case, that should also be added. --AW (talk) 04:51, 29 November 2011 (UTC)

Similar answer as in Talk:Time dilation#I don't understand this. The idea is not that one understands everything by reading the intro, but (perhaps) after having read the entire article and (probably) a number of linked articles. Don't expect to learn special relativity from an encyclopedia though, let alone from this one. That is impossible. - DVdm (talk) 06:32, 29 November 2011 (UTC)

Propose to remove section

We have this (well sourced) section Twin paradox#The time differential explanation in absolute terms at the end of the article, that i.m.o. has nothing to do with the subject of the article. I propose we delete it altogether. Comments? - DVdm (talk) 11:07, 24 December 2011 (UTC)

I have removed the section. If someone thinks there are compelling reasons to restore it, let's first discuss here. - DVdm (talk) 11:29, 28 December 2011 (UTC)

Apparently user Bernardbet (talk · contribs) has restored the section. I don't see any connection between the content of the section and the subject of the article. There is nothing in Taylor and Wheeler's Spacetime physics on page 88 about the twin paradox. So the entire opening paragraph is wp:original research and wp:SYNT. The second paragraph, with the Poincare source, says nothing about the twin paradox. The next paragraph, sourced by Laughlin, says nothing about the twin paradox.

I agree that the last paragraph, although sourced by a mere footnote in the French source, of the section is really relevant for the article, but then again, it is not at its place in a section with a title ==The time differential explanation in absolute terms==. I propose we keep it with a more appropriate section title, say ==Explanation in terms of Mach's principle==. - DVdm (talk) 10:29, 29 December 2011 (UTC)

The point is that 'ether B' folks do not even speak of a twin paradox, therefore the absence of that particular terminology should not be regarded as a deal breaker. See the rewritten first paragraph of section 12 which makes this more clear. The point of including the references is to give weight to 'ether B' point of view. - Bernardbet (talk) —Preceding undated comment added 12:50, 29 December 2011 (UTC).

If these folks don't speak of a twin paradox, then having it here is an even more outspoken example of wp:original research. Your recent addition is also wp:UNSOURCED. Please have a careful read of these policies. The last paragraph is okay with an appropriate modified section header, but I'm afraid there is no place in Wikipedia for the other paragraphs. - DVdm (talk) 13:19, 29 December 2011 (UTC)

Is it? This is an encyclopedia, not a dictionary. If they're talking about the same thing, the language they use is surely irrelevant... Prof Wrong (talk) 14:32, 29 December 2011 (UTC)

The assumption that it is about the same thing is precisely one of original research. If they are indeed talking about the same thing, a reliable source for that fact should be easy to find, but then again that still would be wp:SYNT. Anyway, nothing in the sources that I consulted (Taylor, Poincare, Laughlin) suggests that they are indeed doing so, except for the last paragraph of course. - DVdm (talk) 14:41, 29 December 2011 (UTC)

Yes it is completely OR if you aren't sure if a reliable source does not indicate that they are talking about the same thing. It seems undue to have the fringe views on the page also. IRWolfie- (talk) 15:28, 29 December 2011 (UTC)

The paragraph is an example of WP:Synth. Poincaré never talked about the twin paradox. The specific Wheeler and Laughlin references concern the ether, and do not directly mention the twin paradox. Btw: "ether B" is Lorentz ether theory. There are in fact some like Dingle, Ives, Builder, or Prokhovnik who favor this view in connection to the twin paradox, but this is outside the mainstream. --D.H (talk) 17:09, 29 December 2011 (UTC)

To DVdm: You wrote "If these folks don't speak of a twin paradox.." The fact that the twin paradox does not come up in 'ether B' is relevant. The reader may want to know that there is an interpretation of relativity which makes the twin paradox a moot point. And your claim that the recent addition is not sourced makes no sense for the same reason. See the paragraph in question. To D.H: "Outside the mainstream" is not a basis for complete omission from a Wikipedia article. I will not prolong the debate. --Bernardbet (talk) 23:53 29 December 2011 (UTC)

As it is clear that the addition is both wp:original research and wp:fringe, and lacks wp:notability, I have made the proposed change. Readdition is welcome with proper solid subject-relevant sources. Thanks all for your input and best wishes for 2012! - DVdm (talk) 10:10, 30 December 2011 (UTC)