Talk:Twin paradox

From Wikipedia, the free encyclopedia

	Physics Portal This article is within the scope of WikiProject Physics, which collaborates on articles related to physics.
B	This article has been rated as B-Class on the assessment scale.
Mid	This article is on a subject of Mid importance within physics.
Help with this template Comments: edit – history – watch – refresh I have given this article "Mid" level importance in part due to the context being physics instead of relativity. Although the twin paradox is most well-known of the relativity paradoxes, its understanding is not as essential as the fundamentals of relativity are. The "B"-class assessment is due to this article needing extensive work to be a quality article. Perhaps once the current edit cycle is complete, it may be appropriate to reconsider this designation. --EMS | Talk 05:24, 30 November 2006 (UTC)

•Because of their length, the previous discussions on this page have been archived. If further archiving is needed, see Wikipedia:How to archive a talk page.

Archives
/Archive 01: 2004 to December 2005 /Archive 02: December 2005 to April 2006 /Archive 03: April 2006 to September 2006 /Archive 04: September 2006 to October 2006 /Archive 05: November 2006 to December 2006 /Archive 06: December 2006

Contents 1 The accelerating twin's "gravity field" 2 What are the basics, we undoubtedly agree upon? 3 Note for Harald 4 Section Discussion: "Resolution of the Paradox in General Relativity" 5 Removal of content 6 12/12/06 This article should be reverted to the version of 1 month ago 7 NPOV removal 8 Message from Moroder 9 More trolling 10 The purpose of the talk pages 11 Semi-protection 12 Does the spaceship twin catch up upon arrival? 13 Einstein article 'Dialog' 1918, available on wikisource 14 Subhash Kak

[edit] The accelerating twin's "gravity field"

"Green" wrote above:

Einstein assumes that the traveler knows he is accelerating (which is OK), but then misapplies the EP to erroneously infer the instantaneous (or even lightspeed) existence of a non-local gravity field.

Let me take a crack at demonstrating the flaw in this logic. First of all, let we need to consider what is meant by a "gravity field" or rather a gravitational field. In general relativity, gravitational fields exist due to spacetime curvature. When a mass is accelerated, this information must be propagated through spacetime as a corresponding change in the spacetime curvature. Such changes are known to theoretically propagate only at the speed of light. That obviously in the genesis of the above complaint.

The problem is that in relativity, a gravitational field can also be present in an accelerated frame of reference, as indicated by the equivalence principle. However, this is a very different type of field, as it is based on the observer's view of spacetime instead of being part of the structure of the spacetime itself. In this case, there is no change in the structure of spacetime, and therefore there is no field to propagate. In fact, nothing is being propagated.

Except for the caveat noted below I am in agreement and stated much the same in different words. green 12.30.216.138 02:48, 11 December 2006 (UTC)

The gravitational field of the accelerating twin is of the second kind, and exists only in that twin's frame of reference. For the same events, no gravitational field exists for the stay-at-home twin! What has changed in the traveling twin's view of the universe, not the universe itself! There is no problem with the traveling twin's description of the universe changing for everywhere in the universe instantaneously, as what has changed is the traveler and not the universe.

I agree except for one important, perhaps crucial point; the fact that the twin is accelerating will objectively slow his clock as compared to the stationary clock. This is because the traveling clock now defacto exists in a frame-localized gravity field. green 12.30.216.138 02:48, 11 December 2006 (UTC)

You really don't understand gravitational time dilation. That is a change is in the rate of a distant clock as observed by an accelerated observer. It does not affect the local clock, and for the traveling twin his clock is the local clock. So we see clocks at higher potentials ticking faster than our own (if there is no velocity time dilation involved). Similarly, from the viewpoint of an observer at a higher potential, our clocks tick slow. To be considered as tickng slow due to gravitation, the stay-at-home twin must see the traveling twin as being in a gravitational field. That is not the case as the traveling twin's acceleration is due to his firing his rockets. For the stay-at-home twin, no gravitation field exists and therefore SR's velocity time dilation is all that is applicable to the traveling twin's clock rate.

I hope this settles the issue. --EMS | Talk 03:27, 11 December 2006 (UTC)

You presume too much, way too much. I do understand, quite clearly in fact, that the local clock always appears to 'tick' normally. I also understand that for the traveling twin, his clock is the local clock. (Btw, I think you have a typo in your second sentence of longer paragraph above. I think you mean that the time dilation is the change in the clock rate as observed by the non-local observer; that is, the observer in a different frame who may or not be accelerating.) As for your analysis that follows, except for your concluding comments, you seem to be arguing against a strawman since I never claimed that the non-traveling observer sees the traveler in a gravitation field. In fact, I explicitly denied it! I wrote what you are now concluding; that for the stay-at-home no gravitational field exists (because there's no field propagation resulting from firing rockets). Well, in your effort to correct my allegedly unenlightened (idiotic?) views, you have essentially repeated what I earlier wrote on this subject. green 12.30.216.138 06:03, 11 December 2006 (UTC)

However, your concluding remarks contain an analysis that shows a major divergence of our viewpoints. You claim that for the stay-at-home twin, since no gravitation field exists, SR's velocity time dilation is "all that is applicable to the traveling twin's clock rate". I strongly disagree because the traveler's acceleration -- which can be ascertained to exist by internal measurements -- not only has an objective reality because of this measurement fact, but exists asymmetrically by virtue of the statement of the Twin Problem. That is, the asymmetry of the acceleration is the only asymmetry in the problem, and therefore the only factor capable of destroying the kinematic symmetry which leads to the paradox. Hence, from a logical pov, this asymmetry is indispensible in resolving the paradox. But you defacto claim it is irrelevant. Further, since the acceleration is an objectively existing phenomenon, one cannot explain away its local effects as merely perceptual. That is, I believe there is an objective effect on the traveler's clock (via the EP) even though the traveler observes his clock ticking normally. Although the stay-at-home does not observe any resultant field propagate in his direction or any resultant change in spacetime in his vicinity, he has knowledge of the acceleration's objective effect on the traveler's clock, and from this information he can and will conclude that the traveler's clock rate is slower in comparison to his stationary clock. This probably departs from orthodox GR but this what I think is the reality. I could be totally in error, but this is how I presently see it. green 12.30.216.138 06:03, 11 December 2006 (UTC)

As an aside, the reason these issues are worth discussing here is because if we are going to write about relativity, it would be nice to have confidence that we know the material. In a free discussion, points of contention invariably arise, among them, e.g., my belief that the CMBR can be used to define absolute, or if your prefer, universal rest, and yet does not contradict the Principle of Relativity. I was looking forward to your response to my explanation, but have yet to receive one. green 12.30.216.138 06:03, 11 December 2006 (UTC)

One final note: The "field" in this case does not have its change propagate instantaneously anyway. Instead it "propagates" backwards in time along the past light come leading to the event of the change of acceleration! EMS | Talk 01:49, 11 December 2006 (UTC)

The field either propagates, or it does not. I say it does not. Time reversed scenarios are generally not plausible. E.g., we don't observe anything from the future, so why should this case be an exception? green 12.30.216.138 02:48, 11 December 2006 (UTC)

---

Green - I am done with this. If you do not accept that only the speed of the traveling twin is relevant to computing the time dilation experienced by that twin in the reference frame of the stay-at-home twin, then you do not accept relativity theory. I am not accepting any more of this B.S. about general relativity being relevant to this issue. I wasted too much time explaining why it is not relevant. For anyone proficient in GR, what I am stating is obvious. For those not proficient in GR, the issue is not relevant. It's that simple, and I am now done arguing with you about this. --EMS | Talk 06:24, 11 December 2006 (UTC)

Hey, as long as we're on the subject of "BS", where does your reversed time causality scenario for solving the twin problem fall on the credibility scale? green 12.30.216.138 07:26, 11 December 2006 (UTC)

See light cone, and remember that an acceleration chenges the view of the universe, not the universe. Once you have read that, the answer should be obvious. --EMS | Talk 15:53, 11 December 2006 (UTC)

Don't patronize me with trivial links. I know about light cones. They don't justify reversed time causality. Have we ever detected a signal from the future? green 12.30.216.138 19:36, 11 December 2006 (UTC)

Imo, you have a totally wrong-headed view of acceleration. At every level -- galaxy clusters, galaxies, star systems, planetary systems, planets, asteroids, and on down to the molecular, atomic and subatomic levels -- we see systems that are rotating; that is, accelerating. Acceleration is a truly fundamental phenomenon in the universe, not merely someone's "view". green 12.30.216.138 00:24, 12 December 2006 (UTC)

P.S. Green wrote above:

This probably departs from orthodox GR but this what I think is the reality.

Let me put it to you this way: If it departs from the orthodox GR view, then is makes no difference if it is real. Unless it is documented in the literature and accepted by a subtantial minority in the relativity community, it does not belong here, even in this discussion page. See WP:NPOV. I don't bring my theory into either the articles or their talk pages, and IMO you should abide by the same rules with your views. --EMS | Talk 06:43, 11 December 2006 (UTC)

On the other hand, some of what I believe might indeed be in the literature. Iirc, in the old version of the GR section, there were references criticizing the "perceptual" solution of the paradox. Builder comes to mind, but there were other references, e.g., Moller. In any event, I might accept a viable argument disproving my pov -- why not? -- this is what I seek -- the truth as they say. But in the final analysis all you are really capable of offering are pronouncements from on-high. I was looking for something richer -- like some attempt at explaining how your proposed "perceptual" solution using SR-only velocity-induced time dilations overcomes the kinematic symmetry that is causative of the paradox in the first place. If Einstein got his GR solution wrong as some contend, maybe you have as well. Relativity, along with QM, has brought us to a dead-end. Maybe the politically correct word is "impasse". A little thinking out of the box might help. green 12.30.216.138 06:58, 11 December 2006 (UTC)

The question here is what was being validated by which reference. I don't believe that the Moller reference related to this issue at all.

I know for a fact that Builder was dead wrong about the "propagation" of the gravitational field perceived by the accelerated observer being an issue.

Didn't Builder criticize Einstein's claim that the traveling twin was at a higher potential than the stay-at-home (in context of Einstein's proposed GR solution of twin problem in his 1918 paper) since it would imply or require an instantaneous propagation of the "field" allegedly created, via the EP, by the traveler's acceleration? If so, whatever else Builder might have thought, his view here is the same as yours! Is he still "dead wrong" or do I have my facts confused? -- which is possible since most of what I believe on this issue is second hand from the older version of the GR section. green 12.30.216.138 19:36, 11 December 2006 (UTC)

Btw, I've managed to disentangle myself from the disinformation and arrogant polemics received on the issue we've been discussing lately -- mostly from wannabe physicist Moroder -- wrt his "answer" to my question about the whether the SR calculation he provided is approximate or exact. Maybe he's just a lousy teacher who didn't completely understand my question. You did much better, but still fell short of greatness since there's a straightforward answer to my question that someone intimately familiar with GR could have offered at the get-go! NO CALCULATIONS REQUIRED!!! Stay tuned. Preview below. green 12.30.216.138 19:36, 11 December 2006 (UTC)

THE PRINCIPLES OF GENERAL RELATIVITY STATE THAT THE GEOMETRY OF SPACETIME, AKA GRAVITY, IS CAUSED BY THE MATTER-ENERGY DENSITY, NOT BY THE EQUIVALENCE PRINCIPLE. green 12.30.216.138 19:36, 11 December 2006 (UTC)

See general relativity#Fundamental_principles. Also see my above comments on this issue. The "AKA GRAVITY" part of the capitalized mtext is just plain wrong.

If you wish to show otherwise, get me citations of articles in the literature. Kindly note that the issue is what is known and/or beleieved to be true in the field, not what either of us believes to be true. --EMS | Talk 21:33, 11 December 2006 (UTC)

LOL. You're going trivial on me. The principles you cite (and wrote?) in the article are old hat. I don't disagree. I'm referring to the deeper principles that should also be described as such since they're not derivable within the theory, but assumed; e.g., what the article states later on, and so forth: "The Einstein field equations (EFE) describe how stress-energy causes curvature of spacetime ... " Btw, wrt "AKA GRAVITY", all I was trying to get across is that what was formally thought-of as the gravitational force or field, is now interpreted geometrically as the curvature of spacetime. Maybe you could express it better, but "wrong" it is not. green 12.30.216.138 00:41, 12 December 2006 (UTC)

I am not here to indulge your ignorance. Curvature is not gravitation, but instead is a cause gravitation. You seem to have no concept of that, or of how a gravitational field which can be turned off legitimately exists for an observer in an spaceship firing its engines. I'm here to edit Wikipedia, not to be your relativity teacher. Giving you some advice and help dealing with subtle points is one thing. This continuous sparing is another. --EMS | Talk 04:39, 12 December 2006 (UTC)

Curvature is the cause of gravitation. That's what I meant, obviously, because without curvature, we have a flat geometry, SR, wherein gravity is absent. You ought to give other people more credit. Who knows, you might learn something now and then. green 12.30.216.138 04:45, 12 December 2006 (UTC)

I also accept that my opinion must be secondary to the current state of opinion in the field as it is documented. However, the only current support for this view that Harald could name for Builder's opinion was the Unnikrishnan article. Note that Unnikrishnan's article is blatantly anti-relativity, published in an obscure journal, and uncited elsewhere, such that is is not a reliable source. Without anything usable documenting current (or at least long-term) support for Builder's view, I cannot in good faith allow it be in this article. I am happy to yield to reality if my current understanding of the views in the field is mistaken, but at this time I have no data on which stand by if I am to support inclusion of Builder's view in this article. --EMS | Talk 15:53, 11 December 2006 (UTC)

Within 10 hours 40 edits! ErNa 06:48, 11 December 2006 (UTC)

And your point is what? Think of it as an orgasm. It will peak and you can go back to sleep if you wish. green 12.30.216.138 06:58, 11 December 2006 (UTC)

Maxwell tried to find a mathematical description of electro magnetical behaviour. His sketches show, that he was thinking in mechanical models. But he was aware of the fact, that the (as a function of time and distance) oscillating medium couldn't be normal matter. Sometimes, the unknown was given the name of ether (in greek mythology a personalised cosmic idea). His set of equations -or physical laws- was dependend of the inertial frame used, that is: galileian tranform changed the phyics. Therefore there had to be a special frame of reference at absolute rest. Experiments showed: velocity of light is always the same. It was discovered, that Lorentz transformation makes Max.Equ. independent of a special frame at rest. Now the physical laws are independend of absolute movement. I believe, that this does not imply, that there is no absolute rest. The twin paradox arises from the fact, that one says: if I do not know for sure, if and how I move, every assumption is correct. Tis is just plain nonsence. Before Einstein, time was absolute. But not the actual value of time was absolute, only the distances in time between to events were equal for all observers. This setting was replaced by: the (spacial) distance between to events, measured by independend observers, which don't feel acceleration, reduced by the time distance, multiplied with a constant of dimension velocity, is equal. There is one impreciseness: we can not feel gravitational forces. Therefore, gravitational forces have to be excluded from our thought experiment. (And this implies: there is no need for GR to "explain" twin paradox.) What is the impetus to argue against SR: 1. people fight SR, for they are confused. 2. SR is not complete, and some people prefer special store (tiffanys) from general stores, the cannot see, that SR is worse than GR. (Aren't they true? who can profit from GR?)

And what is the impetus to fight against those, that argue against SR? To me it seems, most just defend a holy gral! Every thing is relative. Even friendly fire!

Two object moving inertialy can not meet twice! Therefore you either have to change direction -this obviously is non inertial movement- or you have to install another ability. ErNa 10:22, 11 December 2006 (UTC)

[edit] What are the basics, we undoubtedly agree upon?

Let' produce a piece of peace! Calm down. If you understand, why I cannot follow your arguments, that is, why YOU are not understandable, you can express yourself more simple, so that even the biggest dummy can learn from You, and You are the most profound teacher! But have have to begin from the very beginning!

Sorry, ErNa. Your words are rough enough so I am ABSOLUTELY NOT interested in such discussion. I beg your pardon for being not understandable. Happy New Year. JM3

Sorry, JM3. Everything is relative. So I understand: you are not interested in discussions, where every side fixes his point of view step by step more precise, but You are interested to take part in discussions, that turn round and round and round, endlessly. Good luck, but You're welcome.

I am not interested in discussions where people are humiliating each other, ErNa. You are treating me as if I were a foolish kid. Anyway, thanks for the welcome and good luck to you too. JM3

Object exist and they pass time and they are not united and they communicate by light and they have size. Is this ok? ErNa 11:18, 11 December 2006 (UTC)

See and comment: http://cmapspublic.ihmc.us:80/servlet/SBReadResourceServlet?rid=1165836351303_1869226839_30184&partName=htmltext

and let us go on step by step until we agree on our differences ;-)

You can edit this map by using CmapTools ErNa 11:44, 11 December 2006 (UTC)

We have to fix our starting point. This is absolutely necessary, if we see this statement: In special relativity, the time dilation effect is reciprocal: as observed from the point of view of any two clocks which are in motion with respect to each other, it will be the other party's clocks that is time dilated. found in time dilation! Undisputed! ErNa 19:40, 11 December 2006 (UTC)

How do You vote?

The statement is correct:

The statement is false: ErNa 19:45, 11 December 2006 (UTC)

[edit] Note for Harald

http://simple.wikipedia.org/wiki/Special_relativity

"In 1908, Max Plank endorsed Einstein's theory and named it "relativity". In that same year, Minkowski gave a famous speech on Space and Time in which he showed that relativity is self-consistent and further developed the theory."

green 12.30.216.138 01:14, 12 December 2006 (UTC)

Fine; But sorry, I have no clue why you bring this up. Which paragraph is concerned? Harald88 19:59, 12 December 2006 (UTC)

Earlier on this page you expressed an interest in Einstein's displeasure with the name given to his theory, and I told you that he preferred "Theory of Invariances". I then stated that I thought Minkowski gave the name, but it was Planck. green 12.30.216.138 20:54, 12 December 2006 (UTC)

[edit] Section Discussion: "Resolution of the Paradox in General Relativity"

I just read the revised version of this section and I think it should be clearly specified what problem is being solved! When the article refers to "the Earth", should we take this to mean a gravitating body, or are we in fact considering two observers floating in inertial space, separating and returning due to the acceleration of one only? When this is clarified, I will have additional comments, but as a preview I get the feeling that it is important to comment in the article on the consensus view of Einstein's 1918 solution. If the twins are in inertial space, there is something awry with this application of GR; without mass-energy, there can be no spacetime curvature, hence no "gravity", hence no gravitational dilation (used to solve the problem). green 12.30.216.138 02:57, 12 December 2006 (UTC)

I understand that my views concerning the weirdness of the GR "solution" are irrelevant wrt what should be in the article. However, I get the feeling that some of these weirdnesses were recognized earlier on, and therefore are relevant from an historical perspective, certainly for those readers who wish to pursue the subject to the next, deeper level. That said, it is certainly weird to assume -- as the article does -- that a traveler who fires a rocket producing, say, one g acceleration, would conclude (even if only "perceptually") that a body with the Earth's mass had just been created, or spontaneously appeared in his vicinity by virtue of his action. There's nothing logical about this conclusion except that the traveler had lost his marbles. Would really he apply the EP to infer a gravitational field when he knew he had just fired his rocket? Yet the article claims that this is what the observer would do in order to apply GR. Makes no sense whatsoever. green 12.30.216.138 04:30, 12 December 2006 (UTC)

If you are saying that firing ones engines does make this a GR solution, I agree with you 100%. Maybe the section should be retitled. Maybe I should just drop it again. However, the gravitational time dilation does exist, but the cause of it is not GR's spacetime curvature at all. --EMS | Talk 04:52, 12 December 2006 (UTC)

[edit] Removal of content

As of now, I am removing new content by "green" added to this talk page. This silliness on his part needs to stop. We must discuss that article, not the theory, and most certainly not green's research. --EMS | Talk 06:06, 12 December 2006 (UTC)

This is shameful. I answered a question you (defacto) asked me wrt the GR section and the solution you wrote up. The value of thinking through these issues, aka, "research", would be to suggest that valid contentions exist in the literature that should be cited, since I don't think I am unique in raising them. But you knew that already. green 12.30.216.138 06:31, 12 December 2006 (UTC)

I agree. The discussion goes forth and back and green gives clear statements. But I am disappointed. Nobody here is ready to give a clear statement, what the basis of his thinking is. My question above is not answered. The twin paradox has so many weak points. For example, the relevance of GR. If we do not focus on the core, we will discuss for ever and I will have much more opportunity to improve my english ;-> ErNa 06:33, 12 December 2006 (UTC)

What EMS deleted, was a summary of conclusions I reached, and why, in my discussion with Moroder, and its relevance to the GR section. I learned a lot in the process. green 12.30.216.138 06:40, 12 December 2006 (UTC)

EMS, If you had more integrity, you would simply cross out what I wrote and let others decide whether it has value, for the article and inherently. green 12.30.216.138 06:38, 12 December 2006 (UTC)

Green - It would be irresponsible of me to let you continue to persue your personal research here. Wikipedia is not a debating society. You are claiming that the SR twin paradox result is "inexact" for reasons that appear nowhere in the literature. I have tried to tell you why that is the case, and you have refused to listen. BTW - Do note that I added this message so that others would be aware of my actions, and not believe that you had not tried to respond to my last posting. --EMS | Talk 15:32, 12 December 2006 (UTC)

No, he is not claiming this! He just says: there is no twin paradox. As Einstein did! The simple truth is: there is no absolute time, that can be measured, for time is measured by clock and clocks tick in dependance of their state of movement. You can not convince him, so answer simple questions of simple people. There is a spectrum of colours. ErNa 15:43, 12 December 2006 (UTC)

[Removed more inappropriate content. This is not Wikipedia U.] --EMS | Talk 16:48, 13 December 2006 (UTC)

[edit] 12/12/06 This article should be reverted to the version of 1 month ago

Oh dear oh dear oh dear. Geometer 14:38, 12 December 2006 (UTC)

B Class is generous! This article is totally misleading at present. It should be ignored by students. Geometer 14:43, 12 December 2006 (UTC)

To reach this state 1 month later again? I would like very much be able to follow all these arguments. But I do not understand what is meant. And we are jumping where we should walk. I own a clock and a pocket rule. The clock is always with me. The clock is connected to one end of the pocket rule. I do not feel any force and I can not see any mass close to me, therefore I believe, I am not accelerated. The clock ticks by flashing. At the other end of the rule is placed a mirror. The reflected light of the flash conincides with the light of the next flash in a detector, which is a integral part of the clock. To me, this is a setup to ask a question. Or is there any degree of freedom to misinterpret, what was stated? ErNa 15:18, 12 December 2006 (UTC)

Please give us a link to the version you want to revert to, so that this can be judged. (I have done "major reverts" in the past. Oddly, they tend to stick.) --EMS | Talk 15:35, 12 December 2006 (UTC)

BTW - Are you complaining about the "Alternate resolution" section? If so, I have just removed it. It was added earlier today by a user named "DingleGhost". Given who Dingle was, I need to keep an eye on this ghost. --EMS | Talk 15:44, 12 December 2006 (UTC)

Why does this article attract so many crackpots? Thank you for dealing with Dingle's disciple. For your enjoyment, here is Dingle's error: http://www.mathpages.com/home/kmath024/kmath024.htmMoroder 16:02, 12 December 2006 (UTC)

This page has been fairly "safe" in the past, but it was also ignored. I'm not sure what to make to the current crop of editors here at this time. Green should take his concerns to USENET as I cannot get him to see his error. I will admit that we are close, but he has no concept of how curvature, acceleration, gravitational fields, and the equivalence principle relate. Without that I cannot communicate effectively with him, and I am done with trying. The Pound-Rebka experiment is enough to show that the traveling twin will observe gravitational time dilation, but Green has no concept of how the equivalence principle equates ourselves with an accelerating observer, nor is he aware that gravitational time dilation is not a curvature effect. --EMS | Talk 17:03, 12 December 2006 (UTC)

I just read the link. Gravitational red shift was confirmed. I know about this result. On its face, however, it doesn't relate in any obvious way to the question of whether an accelerating twin in inertial space will "experience" gravitational time dilation. If it's not a curvature effect, why does the adjective "gravitational" appear in its description? green 12.30.216.138 20:37, 12 December 2006 (UTC)

Apriori, your claim makes no sense (which doesn't mean it's wrong). In the Hafele-Keating experiment, to calculate the gravitational time dilation, they needed to use the difference in gravitational potentials. How could the potentials exist without gravity, that is, without spacetime curvature? If the difference in potential were zero (no gravity, no curvature), there would have been no gravitational time dilation. green 12.30.216.138 20:48, 12 December 2006 (UTC)

In Einstein's lexicon, a "gravitational field" exists whenever one finds that inertially moving objects are accelerating with respect to one's self. So "centrifugal force" is evidence of a gravitational field according to Einstein, along with other fictitious forces. If the gravitational field exists locally, the observer is in an accelerated frame of reference. What curvature does is to make it so that the gravitational field varies in strength and/or direction based on one's position. In SR, the only permitted gravitational field is one due to the observer's acceleration, and in that case the field is of a single strength and direction throughtout the past light cone leading to any given event on the observer's worldline, and comes and goes (or changes strength and direction) with the acceleration.

That is, what I mean, when I say: "precision" . Long ago, David made use of centrifugal forces and that had nothing to do with gravitational field. Gravitational field took care for Goliath falling down to earth! Centrifugal force's counterpart is centripedal force. And this force can be gravitational force, but that is not a must. We would have less to discuss, if Einstein had written everything, what he did not write and gave us the task, to find the rest. ErNa 22:00, 12 December 2006 (UTC)

On the surface of the Earth, we are in an accelerated frame of reference according to the equivalence principle. So the Pound-Rebka experiment measured the gravitational redshift which exists due to our physical acceleration. That is exactly the same gravitational redshift that I am saying the traveling twin observes during turnaround.

Feel free to ask more questions, but I do not want to start going in circles again with you like we did before. If I don't continue making good progress with you, I am closing this down again FAST. --EMS | Talk 21:00, 12 December 2006 (UTC)

Firstly, a note about the politics of discusssion. All along we have been discussing twins in inertial space and Einstein's proposed GR solution using the EP. But when you and Moroder appeal to authorities to disprove some of my beliefs or conjectures, you use experiments performed in non-inertial space where gravitational fields exist, e.g., the Hafele-Keating experiment and Pound-Rebka experiment. For this reason, I have referred to such references as inapposite, since they don't prove what is alleged by those offering them. An unkinder view would interpret such a methodology as manipulative. green 12.30.216.138 01:08, 13 December 2006 (UTC)

That said, I'm still thinking about your preceeding comments, but one issue that immediately comes to mind is this; do they reflect plain-vanilla GR, or one of the perhaps several existing interpretations of the theory? I raise this question because if appealing to experiments is legitimate, I can ask whether a test mass used by the stationary twin would detect a gravity field as he observes the acceleration of his twin at turnaround. You claim that a gravity field exists in SR whenever an observer sees an accelerating object. But what kind of field can this be if experiment will almost certainly falsify its existence? green 12.30.216.138 01:08, 13 December 2006 (UTC)

Further, assuming a "real" field exists and is of a single strength throughout as you allege, then its potential must be constant. Why would the stationary observer claim that a non-zero gravitational time dilation exists when comparing his clock to the traveling twin, if theory told him that he is at the same potential as the traveling twin? green 12.30.216.138 01:08, 13 December 2006 (UTC)

I can't respond to you further here. Either get an account or e-mail me, but this discussion does not belong here. (These questions are no all that bad, but the level of misunderstand of GR that they reveal just makes it clear that I cannot respond to you furhter here after this.) For the record, two simple answers will do:

1. This is "plain vanilla GR" that I am refering to. There are no disagreements on this issue amongst relativists.
2. There is no gravitational field for the stay-at-home twin: That twin is never in an accelerating frame of reference. Only the traveling twin at turnaround is in that situation.

--EMS | Talk 03:50, 13 December 2006 (UTC)

That's OK. Would email be acceptable? I will keep the questions to a minimum and very focused. My email address is edward.greenberg@netzero.com .

Wrt the article, I strongly disagree about the relevance of this discussion if we are to produce a coherent article. E.g., if the GR section is to remain, I think the readers will want to know -- the thoughtful ones that is -- why the accelerating twin would calculate the time dilation of the stationary twin's clock based on a gravity field that an experiment would obviously show is nonexistent -- and that he knows is nonexistent because it defies logic to assume that his local action could have such a profound non-local consequence -- since he would have to convince himself that firing his puny rocket, creates the effect of an Earth-sized mass (if he accelerates at one g). If this is the consensus view of relativists as to what relativity theory implies in this situation (as you allege), it is legitimate to wonder if the fundamental concept of falsification of theories via measurements and (in some cases) thought-experiments has been thrown out the window. This is breathtaking.

Wrt the EP, from what you write I suppose I was mistaken in what it means. I always thought, using the elevator that Einstein made famous, that if the occupant could not look out, it would be impossible via internal measurements to distinguish the effects of acceleration from gravity (for infinitesimal displacements). I never imagined that if the occupant directly caused his acceleration -- and therefore had no issue distinguishing it from gravity -- that the EP allowed him to infer the (perceptual-only?) existence of a nonlocal gravity field. I know relativity is difficult and subtle, but I had no idea it had apparently lost touch with reality as quantum theory has -- e.g., in its many-worlds interpretation. Again, breathtaking. green 12.30.216.138 05:26, 13 December 2006 (UTC)

First of all, I see the GR section as baggage that does not help the reader. I can be mentioned in a history section, but I now feel that if is to be covered in any detail then it should be an article on its own. As for the EP: It only applies locally, but in SR the infered field is global in extent. I will e-mail you on the issue of how an accelerated observer must perceive a gravitational time dilation effect. There is no loss of contact with reality here, just a theory that does not behave as you expect it to. --EMS | Talk 06:22, 13 December 2006 (UTC)

Reset indent: (Inappropriate response from "green" removed. This page is for discussing the article, not the theory.) --EMS | Talk 16:38, 13 December 2006 (UTC)

For anyone interested in thinking for themselves, I copied below what EMS deleted. It should have been obvious to EMS that what I wrote was my final statement of the state of things from my pov, and that I planned to continue any further discussions in private email. I am sure there are serious issues about the so-called GR "solution" that exist in the literature, and it is inconceivable that anyone who reads the GR section will understand or believe it. That was one of the main motivations for my discussion. But it is painfully clear that EMS has the mind-set of a conformist who cannot stand contrary opinions -- and here I am referring not to my opinions but to documented ones in the literature. This is why he removed Builder's reference. I won't be partipating here in the future. green 12.30.216.138 17:33, 13 December 2006 (UTC)

Theories can behave in any which way. However, if a theory is falsified by experiment, or in this case by two thought experiments as described above when applied to a particular situation, one has no alternative but to reject that it can be applied to that particular situation. If it cannot, it might have broader negative implications for the theory. As to the EP, it has been my understanding all along that it applies locally. However, it seems clear that the traveling twin applies it globally to infer the speeding up of the stationary twin's clock. So until I see something that makes sense, I hold to my position that the GR solution of the twin problem is nonsensical because it applies and depends upon an erroneous application of the EP. Fwiw, this was my position in my summarizing statement of conclusions from exchanges with Moroder (which you deleted), with the additional point that the SR calculation is exact because there is no EP effect. Nonetheless, I am open to the possibility of having my conclusions falsified, and I look forward to your subsequent analyses of these issues. green 12.30.216.138 07:03, 13 December 2006 (UTC)

---

The mainstream called Boltzmann a crackpot. And he became insane. Newton was crazy. Obviously it is ennobeling to be called "mad". RIP, I can't ErNa 18:26, 12 December 2006 (UTC)

I support a revert to a past version. I liked the old one with a GR section and a short critique of it. Tailpig 20:02, 12 December 2006 (UTC)

I submit we revert to this version oldid=63968684. Tailpig 20:08, 12 December 2006 (UTC)

I don't see that is buys us anything to do this. What this article needs is a careful rewrite, but I don;t have time for that now. --EMS | Talk 03:54, 13 December 2006 (UTC)

[edit] NPOV removal

The article's neutrality is just fine. Trolls in the talks page need to get a newsgroup. Keep the theoretical work off of this space. Tailpig 19:28, 12 December 2006 (UTC)

Instead, please address the issues in the section above where it is being discussed. Harald88 19:56, 12 December 2006 (UTC)

The discussion lacks from precision. For example (from time dilation, easy to see): The formula for determining time dilation in special relativity is:

where

Δ t  is a time interval measured by an observer in a stationary frame of reference,

Δ t₀  is that same time interval as measured by an observer in the moving frame,

Do you know why the twin paradox is called a paradox? It's called paradox since one cannot solve it using methods of special relativity theory. The twin paradox includes both acceleration of inertial frames and gravitational time-dilation; the special relativity theory explains none of that, to actually solve this paradox one will have to use the general theory of relativity. Lady Stardust 12.29, 24 february 2007

These equations are incomplete. No information, which time interval is measured and how. This to causes confusion. ErNa 20:13, 12 December 2006 (UTC)

Irrelevant! Go write a paper and get it peer reviewed. As indicated on the page, "This article or section is in need of attention from an expert on the subject." Tailpig 20:23, 12 December 2006 (UTC)

Irrelevant indeed: The discussion happens to be about opinions as expressed in peer reviewed papers! Several experts on the different subtopics are participating in this discussion already, but much clutter is added by non-experts. The discussion is fresh and ongoing but is now moved to the archives [1].

Here follows a copy of the start of the discussion, but more open pieces of the discussion are scattered above. Harald88 07:56, 13 December 2006 (UTC)

---

While the "GRT solution" is notable, also notable criticism must be mentioned with some of the best examples. Einstein's "GRT" solution was never published in the English literature except in discussions and criticisms; nowadays that solution is rarely advocated. Those facts must be mentioned and explained, citing peer reviewed sources following WP:V. This is both required by WP:NPOV and out of respect for the readers who should be properly informed. Similarly, the different notable explanations must be cited in stead of suppressed; I notice now that also Langevin's explanation has been so much truncated that it is effectively suppressed, while also the reference has been deleted against WP:V (see Wikipedia:NPOV_tutorial#Information_suppression). Harald88 14:56, 2 December 2006 (UTC)

Correction: it was never published in an English language journal, but I now found that an English translation of Einstein's 1918 paper exists. Harald88 07:56, 13 December 2006 (UTC)

I've reproduced (in italics) the deleted paragraphs below for reference. The first paragraph is not clear and therefore difficult to evaluate as to content. Personally I am not totally convinced by the alleged solutions using SR. Although I have yet to carefully read the SR solutions in the article, from my previous studies and presumption as to the article's content, I am not sure about their validity. E.g., when using the frame jumping method, is the behavior of the traveler's clock adequately analyzed at the instantaneous turnaround, or is this issue swept under the rug? ... Concerning the critique below of Einstein's GR solution, I am not sure I understand the claim that using the equivalence principle requires the assumption of an instantaneous propagation of the gravity field to the stationary twin. Whether one uses SR or GR, one always calculates based on local observations, and then applying the principles and transformation equations of the theory being used. Otoh, for there to be a real difference in clock readings, we must be dealing with bonafide differences in gravity fields. In this view, Builder's critique would seem to have merit. ... In sum, I think this entire issue needs to be thought through with much care before we leave the GR section trucated. green 12.30.216.138 04:20, 1 December 2006 (UTC)

It is sometimes claimed that the twin paradox cannot be resolved without the use of general relativity, by which it might be meant that age difference cannot be calculated by the travelling twin without general relativity, something we have tried to show can be done. On the other hand, the claim that general relativity is necessary, may be a claim that someone who doesn't believe the argument which rejects the first (erroneous) calculation by the space-ship crew is strong enough to convince the crew that they should perform the second correct calculation instead. The general relativity explanation says: if you are going to claim your reference frame is good, and deny the implications of changing reference frames, you will need to consider the inertial forces as equivalent to gravity forces and then account for the physical effect of gravity.

This explanation was popular among a number of physicists (Møller 1952) and continues to find adherents today. However, that calculation and its related interpretation have met with serious criticism. For example, after remarking that the general relativity calculation only corresponds to perceived reality for the traveler, According to Builder (1957)[1], Einstein's solution of the twin paradox is invalid because the induced field must appear everywhere at the same time:

The concept of such a field is completely incompatible with the limited value c for all velocities [...], so that the specified field would have to be created simultaneously at all points in S' and be destroyed simultaneously at all points in S0. Thus the principle of equivalence can contribute nothing of physical significance to the analysis.

Similar opinions have been expressed more recently by others[2].

Thus in later years, physicists have increasingly treated general relativity as a theory of gravitation, while including acceleration with special relativity; consequently, acceleration is commonly regarded as "absolute" after all.

I see that the neutrality issues have not been corrected but the banner has been removed. Please don't remove the banner without addressing these issues, thanks! Harald88 22:41, 5 December 2006 (UTC)

I see neutrality issue with the included text. It gives Undue weight to an opinion that is held by very few people in the field. Builder's objection is known to be mistaken, and the second citation is for the Unnikishkan (sp?) article that you have been told over and over again is anti-relativity and wholely unaccepted in the field. You have also been told over and over again why the Unnnikrishkan article is not a reliable source due to its being published in an obscure journal with minimal peer review. Yet you seen to feel that this viewpoint deserves prominent billing because you have found citations.

You need to realize that it is very important to put material like this in context. Wikipedia is not an attic. --EMS | Talk 15:24, 13 December 2006 (UTC)

Builder's objection to Einstein/Moller's argument of the relativity of acceleration (where is Einstein's POV now?) happens to be the one that you yourself also expressed by not even considering what you both reject; thus either you are both mistaken or both not. The Unnikrishan article isn't an issue since we unanimously agreed to scrap it.

I suggested to add references to writings by for example Janssen, and I now provided a reference to an overview article that happens to refer to Builder as well.

As you claim that this article now fairly discusses the different opinions as required by WP:NPOV, please show that by citing the fair descriptions of the different opinions, since I dont't see them but I could have overlooked the new passages that do so. Thanks in advance.

Harald88 21:44, 13 December 2006 (UTC)

Harald - NPOV does not require that any alternate viewpoints be listed unless they are held by a "significant minority". The "Alternate theories" section of black hole does reflect that such a minority exists in opposition to the black hole concept, yet at the same time the size of that section says much about the size of that group. You don't have that level of discomfort with regard to the twin paradox. Certainly once I got more oriented I realized that the viewpoints being presented in opposition to the Einstein/"GR" solution represented a misunderstanding of relativity.

If you want to document a significant counter-view, then be aware that the twin paradox has been used down through the years as a disproof of relativity theory. It may be worthwhile to document that stream of opinion and the counter-arguments to it. Just be aware that it must be made clear that this view is universally panned in the scientific community today.

Beyond that, I would appreciate your indicating what the overview article that you are refering to above is and how I can either read or obtain it. Indeed, listing your suggested sources here may be worthwhile and could give us a framework for discussing this issue more productively. --EMS | Talk 02:56, 14 December 2006 (UTC)

---

In a nutshell: Mention of other opinions has been deleted including the opinions as expressed in some cited papers. Instead, only the "apparent paradox" -as one recent review paper calls it- is discussed and only the popular POV is mentioned.

I propose to shortly mention that in the course of time other viewpoints have been offered and debated, and link to an overview in an article "History of the Twin paradox". Harald88 07:56, 13 December 2006 (UTC)

A history article or section may be worthwhile. At least it can put material into its proper context, and there can be discussion as to what has become over viewpoints like Builder's. (Unnikrishkan you should never mention again.) --EMS | Talk 15:24, 13 December 2006 (UTC)

Harry, why do you keep trying to introduce your OWN biased POV at any expense. What you are trying to do is very transparent, you are trying your darnest to cast doubt on the validity of relativity, all your "interventions" reek of that. Do you really think that we are THAT naive? Please stop slapping NPOV tags on all the items that don't conform to your attempts to bring back Lorentz aether theory over the Einstein relativity. Please stop this barrage of obscure antirelativity papers. Yours is the most biased POV, far from a neutral one Moroder 16:03, 13 December 2006 (UTC)

It hardly needs mention that user:Morodor is still trying to block any mention of notable minority views (including Einstein's) in Wikipedia articles, which is against WP:NPOV policy. Harald88 21:51, 13 December 2006 (UTC)

Harald - I will support Moroder's advice but not his words. The Unikrishkan article is the only anti-relativity one that I have seen you hype like this, but you have failed to put it in its proper context. I understand your being upset at what you perceive as its inappropriate removal, but your not getting your way does not mean that an NPOV violation exists. --EMS | Talk 19:03, 13 December 2006 (UTC)

EMS, I already agreed repeatedly with the non-inclusion of that article for the reasons discussed earlier (Pjacobi's argument). You may have overlooked that due to the enormous amount of clutter on this page.

If you read my explanation again with the knowledge that your preconceived idea is mistaken, you may understand why I put the NPOV tag here.

For a fair presentation of views, only a few lines are required that mention the different views (even the mainstream view about the deeper issue was not and still is not explicitly mentioned!), similar to for example the Black holes article.

A more elaborate overview of the different debates (which, BTW, according to the scientific literature still are going on -incl. the American journal of physics) can then be given in a separate article that discusses the deeper, philosophical issues.

Regards, Harald88 21:44, 13 December 2006 (UTC)

Hmm, Harry left the same "marks"(NPOV tags, inclusion of antirelativistic papers) on the Maurice Allais, Dayton Miller and until recently, Luminiferous aether articles.Moroder 19:39, 13 December 2006 (UTC)

Yeah and guess why? See the Talk pages, and look at the recent actions of Morry! Harald88 21:44, 13 December 2006 (UTC)

[edit] Message from Moroder

"green" you are also "sock pupeteering" by using a second account : 4.227.136.248 Moroder 16:21, 12 December 2006 (UTC)

The wireless server connection I usually use stopped working for awhile, so I used the phone line with my other server. Is this a problem for you? green 12.30.216.138 21:08, 12 December 2006 (UTC)

Then get a user name like everyone else. Moroder 16:47, 13 December 2006 (UTC)

I see no need for one. green 12.30.216.138 16:58, 13 December 2006 (UTC)

Here's a good reason to get an account. green 74.101.25.251 03:51, 14 December 2006 (UTC)

Moroder, I was software engineer. What you did takes little creative effort. Is this what's called "cock suckerteering"? green 12.30.216.138 04:07, 14 December 2006 (UTC)

You just demonstrated that you are a disgusting troll and should be banned. Moroder 04:31, 14 December 2006 (UTC)

I think that you are both making yourselves look silly. BTW - I will wait a day and then either archive, delete, or move this thread to the IP's talk page. --EMS | Talk 04:54, 14 December 2006 (UTC)

Troll? Who sent the message in the first place? What is a "sock pupeteering", really? What does it sound like? Is this the level of "deep thought" you apply to Einstein's GR solution? green 12.30.216.138 05:26, 14 December 2006 (UTC)

A sock puppet is a second account meant to look like another user but which is in fact just you again. This is most often done by a user attempting to evade a block, but there are other illegitimate uses for sock puppetry and even a few legitimate ones. I for one find it a little disingenuous to accuse an anon of "socking" when they end up with a different IP. While we would much rather you get an account, I for one think that we must respect it when an editor is operating within the rules.

As for trolling, please see the last message I left you on your de-facto talk page. --EMS | Talk 05:42, 14 December 2006 (UTC)

Reset Indent: I'm not a troll and not a "sock puppet". I am sick and tired of any and all accusations. I am just someone interested in physics, who has formally studied it (but not GR) who sees no need for a Wiki account, and disagrees with you on some basic relativity issues (which you find intolorable), and how this disagreement should effect the article. I am not trying to change a Wiki article to include my research, but merely to make the case that if your evaluation is wrong, it will bias the article in a way that does a disservice to the readers. But to show you, that notwithstanding your expertise you are likely wrong, there was no alternative but to engage a discussion. The discussion is over. Check the equivalence principle as discussed below, and, if you wish, indicate to the editors here whose position it supports. green 12.30.216.138 06:52, 14 December 2006 (UTC)

[edit] More trolling

Green - I am going to continue to remove content until and unless you stop pushing your own personal viewpoint here. Your questions are good, but they belong on USENET, not here. That article has major issues, including obtaining the proper citations. You have become a major distraction from the issue of editing the article, and that is the issue I have with you now.

I may or may not e-mail you. You have no comprehension of what I have been trying to tell you, and instead have shown that you lack the conceptual framework needed to bridge the gap between our positions. I am not here to be your personal relativity teacher. --EMS | Talk 16:57, 13 December 2006 (UTC)

Please be advised that I am not interested in any email contact with you, or any editing of the article. I am also sick and tired of your attitude, accusations, and censorship. green 12.30.216.138 17:06, 13 December 2006 (UTC)

If you are not interested in editing the article, you definitely shouldn't be contributing to its talk page.

Apologies to everyone for this comment - it is not about the article either. It belongs on a meta-talk page.

DVdm 17:31, 13 December 2006 (UTC)

I put it here because I wasn't sure how to get the message to EMS. I also wanted everyone to see what a control freak he is. I won't be a thorn in his side any more, as I have no intention of further participation here. green 12.30.216.138 17:46, 13 December 2006 (UTC)

I gather that you never noticed the "talk" link in my signature. you also could have edited your own IP's talk page to respond. Either is standard procedure here. (To all: This was originally posted on the talk page for "green"-s IP. He has no concept of user talk pages or watchlists I see. Then again, as he refuses to get an account, he has neither.) --EMS | Talk 17:57, 13 December 2006 (UTC)

I've noticed the "talk" link, of course, but I wasn't sure if it would allow me to communicate with you if I didn't have an account. Since I didn't feel like researching this issue I posted here. To repeat, I am sick and tired of your "trolling" accusations, self-serving censorship and misinterpretations of my intent, so I've decided to cease further interaction with you. green 12.30.216.138 19:09, 13 December 2006 (UTC)

[edit] The purpose of the talk pages

Green - You may not be intending to troll, but even so your actions do amount to trolling. I see where you are coming from: You want the content of the article to be mathematically and conceptually vetted. That is all fine and dandy, but that is not what the talk pages exist for. The issue is what the content of the article should be, and that is fundamentally driven by what the literature on the issue says. Whether of not the view in the literature is correct is a whole other issue which is beyond the scope of Wikipedia.

You still don't get. Sure I want the article conceptually vetted at a minimum. This means that I want Einstein's solution presented as he stated it. However, since in this particular case the argument against it has such a high degree of plausibility despite your "expert" claims to the contrary, the counter-arguments must surely be in the literature and should be found and presented as well (a balanced view as it were). I posed some probing questions and know enough about the subject to see that your rebuttals are not at all convincing. As long as you remain convinced, e.g., that the EP is used appropriately in Einstein's GR solution, you will insist on the omission of the critiques, to the detriment of the reader. Now don't give me a load of bull that I don't know what I am talking about. As a exercise, please review equivalence principle and be sure to report back (one way or the other) if you find anything in the article remotely suggesting that the EP can be used as described in the GR solution. I've also read parts of Rinder's discussion of the EP in "Essential Relativity" and the same conclusion applies; i.e., I've never read anything that remotely suggests it is applicable globally -- which indeed is how it is applied in the GR solution. I know enough physics to know the difference between "local" and "global". If your turnaround twin believes that the gravity field extends to the stationary twin for the purpose of calculating the gravitational time dilation, then, defacto, he is applying the EP globally. Never, except in Einstein's GR solution, have I come across the claim that it applies in a case where acceleration is caused through a conscious act of the observer. The main form is always stated in terms of an impossibility -- of the observer to locally distinguish the forces of acceleration from gravity. green 12.30.216.138 06:37, 14 December 2006 (UTC)

To help to orient a newbie on the technical aspects of a subject like the twin paradox is one thing. However, going in circles over whether the GR solution is correct or not is another. The issue here is whether the GR solution should be presented, and if so how the related facts should be presented. If you lack the knowledge needed to make sound judgements on those points, you should not be discussing that aspect of the subject. --EMS | Talk 05:10, 14 December 2006 (UTC)

I have little interest in communicating with someone who persists in the illusion of knowing somewhat more than he does, while consistently under-evaluating others (who now and then have useful insights). I make errors as I go along due to lack of technical knowledge, as GR is not one of branches of physics I formally studied, but the main thrust of my argument on this issue is likely correct. Please stop sending me private messages. I don't need your ill-conceived put-downs (which is not to say you're wrong in every instance) and rationalizations for censorship. Do as you wish with the article. green 12.30.216.138 06:37, 14 December 2006 (UTC)

To further clarify, the misapplication of the EP is not "global versus local" as I stated above, as the fact that the EP is MISinterpreted by the turnaround -- and hence those advocating the GR "solution" -- to mean that gravity and acceleration are identical phenomena. That is, when the turnaround sees the stationary or inertial twin accelerating, he interprets this observation to mean, ipso facto, that a gravitational field exists. HOWEVER, as a reading of equivalence principle makes clear, the EP makes a much weaker assertion; namely, that in a specific circumstance, the phenomena of gravity and acceleration are indistinguishable. Obviously, of course, for the turnaround, they are NOT indistinguishable since he knows that by firing his rocket he has caused the stationary twin to appear to be accelerating. In summary, the claim that the EP is applicable in the GR solution is one of those "sleights of hand" that is based on a sloppy inference of what "equivalence" means. But don't take my word for it. Read the referenced Wiki article. green 12.30.216.138 18:21, 15 December 2006 (UTC)

So what? What's your purpose? What do you hope to achieve with this paragraph? Is there a change you would like done to the article? Perhaps an additional external reference? State your intentions clearly and provide proper sources. Tailpig 21:19, 15 December 2006 (UTC)

What's my purpose? I stated it clearly in my first paragraph in this section. How can you guys edit anything when you can't read plain English? green 12.30.216.138 23:19, 15 December 2006 (UTC)

Tailpig - "Green" wants the "GR" solution to be conceptually and mathematically validated to him before he will accept its correctness. There are two difficulties that I have with this. The first of is that it is not our job as editors to validate the work of others, but instead to report what that work is. Einstein did this "GR" solution, and it should be reported on as such.

Green also misses the meaning of the equivalence principle. I have tried to show him his error, but have only ended up with the point he has chosen to make above getting more and more shrill. Because of that, I now prefer to fall back one the basics of what Wikipedia is. If "green" can show me reputable sources that back his position, then it will be considered. Otherwise, "green" should not be trying to act like a reputable source for the content of this article. --EMS | Talk 03:47, 16 December 2006 (UTC)

I rendered this point moot. See the peer-reviewed paper (Foundations of Physics Letters 2006) that gives the complete SR and GR treatment and shows that they give identical answers[2]Moroder 16:14, 18 December 2006 (UTC)

I noticed it. It certainly helps to nail the case that the two are identical. Maybe we can now return to the issue that bug me: Should that section even be there? I keep seeing something that is very advanced and very subtle. I understand how it works and why it works, but is it fair to expect others to understand that? I honestly suspect that the difficulties that "green" has with this are indicative of what we can expect from the average reader. Maybe that should be a seprerate article, if it is to be present in Wikipedia at all. --EMS | Talk 21:53, 18 December 2006 (UTC)

The treatment should be at the highest possible level, I feel that the addition of the paper by the two college professors has just attained that. People can elect to read the prose or, if they are more advanced, they can read the paper. I think the section should stay where it is. Moroder 00:53, 19 December 2006 (UTC)

Reading the above comments, I sense that the "experts" do not deeply understand much of what I have been complaining about.

Firstly, the section on Einstein's GR solution appeals to the equivalence principle, but if the reader goes to that article, he will find nothing in the statements of any version of the principle that implies what EMS added in response to my comments on this Talkpage, namely, "It is important to note that any accelerated frame of reference has a gravitational potential associated with it." Iow, a ubiquitous gravity field is implied by the EP for any accelerating frame, but there's nothing in the statements of the forms of the EP that contain this key point. If this is "shrill", so be it. Istm, there's something fundamentally deficient in the EP article, given that something as important as EMS's addition does not follow from, or is not explicitly stated, in any version of the equivalence principle. This state of affairs will surely confuse the average reader, but he/she will likely not know the source of his/her confusion when trying to connect the EP as stated in Wiki, with the static homogeneous gravity field implied by the EP, due to the turnaround twin's acceleration. As distinguished from an "average reader", it was clear to me that Einstein's GR solution as stated in the TP article, when juxtaposed to the EP article which it references, causes Einstein's solution to take on an ad hoc appearance -- that is, un-principled as in not following from basic principles.

Secondly, the fact that the SR and GR solutions are identical is obviously important and the article Moroder found should be an included reference. However, this was not an issue I was addressing, so I fail to see what point Moroder thought he had rendered "moot". My issue all along was the nature of the gravity field implied by the turnaround's accelerating frame and its justification based on the EP, and whether Builder's critique of Einstein's GR solution was worthy of inclusion. I've been looking over his 1957 paper and find some compelling issues. green 4.227.130.159 07:56, 25 December 2006 (UTC)

Looking again at the article on the equivalence principle, near the beginning, it seems that in his 1911 paper, Einstein postulated what I would call a general equivalence principle, that does go beyond what is contained in, or implied by, the three forms of the principle given prominence in the article. I find it misleading that the three forms that are usually given prominence, seem less powerful than the one stated in Einstein's 1911 paper, and this has been a source of my confusion on this issue. green 12.30.216.138 07:09, 29 December 2006 (UTC)

Btw, for those interested, Einstein was NOT using the Weak Equivalence Principle when analyzing the twin at turnaround, as EMS claimed. He was using the more general EP, stated in 1907 and/or in 1911, which is not featured in the EP article. This looks like another case of the "experts" giving misleading information and explanations. green 12.30.216.138 15:30, 29 December 2006 (UTC)

[edit] Semi-protection

This talk page has been semi-protected due to block evasion by a chronically disruptive unregistered editor. Durova^Charge! 15:09, 16 December 2006 (UTC)

Semi-protection lifted. Durova^Charge! 17:52, 20 December 2006 (UTC)

[edit] Does the spaceship twin catch up upon arrival?

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).

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)

[edit] Einstein article 'Dialog' 1918, available on wikisource

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)

[edit] Subhash Kak

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)

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)

since the claim is that this paper has been "electronically published in the International Journal of Theoretical Physics", can anyone of you get a look at it? We should call it for what it is on the Subhash Kak article, but we obviously cannot do that before we've seen it. All we can say so far is that the LSU press release is utter gibberish. I am also under the impression that the IJTP is a serious journal, and I find it difficult to believe that they would accept a paper that can be recognized as bogus at a glance by any physics graduate, so that there is the possibility that just the press release, but not the article, may be bogus(?) dab (𒁳) 10:25, 19 February 2007 (UTC)

I think it is this one. Rasmus (talk) 12:50, 19 February 2007 (UTC)

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)

uh, this dates from May 2006, and judging from the abstract, he is not claiming to have made any great progress, just that he did some calculation exercise on the topic. Maybe the hype isn't Kak's fault after all? dab (𒁳) 15:48, 19 February 2007 (UTC)