Talk:Twin paradox/Archive 6

Why should the CMBR frame be the absolute frame ?
''Why cannot the CMBR frame be considered the frame defining absolute motion? green 12.30.216.138 23:20, 4 December 2006 (UTC)''


 * Why should the CMBR frame be the absolute frame? Because it exists everywhere (unlike the Earth), is the same everywhere, and can therefore be used as a universal reference. green 12.30.216.138 04:06, 5 December 2006 (UTC)

This morning, I first want to thank You all for the friendly atmosphere! Normaly, discussions on the topic of theory of relativity end in a battlefield ;-). In the german version is written: "Nach der Relativitätstheorie schließt jeder Zwilling aus seinen


 * Even if the symmetry were broken, I infer you would still claim that no clock is ever running "absolutely" faster or slower than any other clock. If so, what you would be claiming is the conventional wisdom based on what we have all been taught about relativity. But it's not true. The CBMR frame defines a universal clock -- the uniform background temperature of the universe which is slowly cooling -- and it could be used to determine that the traveling twin's clock is running slower than the stay-at-home twin, and absolutely so since both clocks can be referenced to the universal clock of the CMBR. But again, one need not use this clock in an analysis of the twin problem. green 12.30.216.138 06:31, 6 December 2006 (UTC)


 * I never claimed that the asymmetry is caused by the absolute frame. Classically, it's caused by forces experienced only by the traveling twin. A frame is used to measure the asymmetry, but doesn't cause it. green 12.30.216.138 06:31, 6 December 2006 (UTC)


 * I fail to see what Mach has to do with this discussion. I am just pointing out that there is a frame of reference that contradicts the tenets of relativity -- it can be used to define rest and the same time everywhere in the universe for all observers. So it seems to satisfy the conditions for calling it an "absolute" frame of reference. Don't shoot the messenger if you don't like the message. green 12.30.216.138 18:37, 6 December 2006 (UTC)


 * What do you disagree with? The CMBR exists and can be used to define universal rest and a time that is the same throughout the universe. Whether this qualifies it as an "absolute" frame depends on one's definition of absolute. Maybe, in Lorentz's version of relativity, when the ether was vogue, an absolute frame was conceived as the unique frame in which the speed of light is c. I think you need to specify your definition of an "absolute" frame before you can argue that the CMBR is not that very thing. green 12.30.216.138 23:47, 6 December 2006 (UTC)


 * Agreed. This is in last paragraph of Introduction to article. To put it another way, kinematics alone leads to a paradox since it implies symmetry, and symmetry implies that each twin sees the other as younger when they are united. green 12.30.216.138 23:47, 6 December 2006 (UTC)


 * I don't see the relevance of the so-called Mach "principle" (which, btw, was never precisely stated). If you want to imagine nothing in the universe except the twins, one of which accelerates, and no CMBR, one can still determine the asymmetry if each twin carries an accelerometer. Remember, the twin problem assumes that one twin leaves and returns, and both twins are aware of this fact. So it isn't disallowed to assume each has an accelerometer. green 12.30.216.138 23:47, 6 December 2006 (UTC)


 * Green - The asymmetry is caused by the acceleration of the traveling observer independent of the forces which caused that acceleration.


 * Of course. It doesn't matter what the cause of the acceleration is; it's the fact of its existence that allows us to say that the twin frames are not symmetric. green 12.30.216.138 20:00, 6 December 2006 (UTC)


 * In GR, the acceleration could be caused by the traveling twin passing close enough to a neutron star or black hole. In that case, the traveling twin would have felt no forces on the spaceship, but would none-the-less have had his trajectory and frame of reference changed. --EMS | Talk 17:37, 6 December 2006 (UTC)


 * For simplicity I was thinking about the SR situation to make the point that the frame of reference is not the cause of the asymmetry. As you correctly point out, for GR there are no forces. In that case, the cause of the asymmetry would be the change of geometry caused by the neutron star. green 12.30.216.138 18:37, 6 December 2006 (UTC)

-

Is Relativity a Kinematic Theory?
I see no basis for the claim that SR or GR are kinematic theories. The Twin Paradox resoundly disproves this claim. In fact, the name of the theory, "Relativity", is misleading insofar as it lends credence to the claim. green 12.30.216.138 19:40, 5 December 2006 (UTC)


 * I don't think that that is something to be put into this article (possibly interesting for relativity). However, I vaguley remember that some people (maybe even Einstein) disagreed with calling the theory "relativity". If someone finds such a reference, it could no doubt be helpful for readers. I also vaguley remember having read somewhere that "spacetime" is very much "absolute" (maybe that was jansen?); and such a reference may be appropriate for this article when describing the absolute spacetime explanation of the Twin paradox. Harald88 15:41, 9 December 2006 (UTC)


 * I recall reading, but can't remember where, that Einstein preferred calling it a "theory of invariances". I think Minkowski named it "relativity" but I am not absolutely certain. green 12.30.216.138 07:07, 11 December 2006 (UTC)

Last paragraph of Introduction edited
Let me know if there are any problems with Introductory section. green 12.30.216.138 05:25, 6 December 2006 (UTC)


 * I agree. We know, SR is incomplete, so is GR. The obviously wrong perception can be seen at JM3's contribution. At least, I can not follow him. Also, "It is a common belief that the universe is finite but unbounded" is not related to SR, could be a solution in agreement with GR but to me it is fantasy, and doen't solve any problems. You say: "is caused by the error of assuming that relativity implies that only relative motion between objects ..". Can we set up an experiment that shows, why this is an error?


 * At least, I can not follow him you wrote. How can you say that I have "the wrong" perception if you recognize that you haven´t understood me? Should I consider that you did' understand me and that sentence is at least rough? 89.26.180.131 01:41, 9 December 2006 (UTC)


 * We have a thought experiment that demonstrates the error. It is called the twin paradox. green 12.30.216.138 01:43, 7 December 2006 (UTC)


 * You are right. But all the discussion comes from the fact, that even physicist struggle on it. Just now, in the german wikipedia is written: Nach der Relativitätstheorie schließt jeder Zwilling aus seinen Beobachtungen. And more nonsense follows. It comes from the LT, which seems to give the same results, for both observers. The following experiment should be able to determine which object was accelerated. I don't see an error, but that doen't mean, that there is none. ErNa 07:06, 7 December 2006 (UTC)


 * There is no doubt that each twin observes the other accelerating. This is inherent to the way the problem is stated and therefore would be an undeniable observation if the experiment were performed. The question for us and the German author is this; does relativity gives us reason to believe that this fact is sufficient for the analysis; or to put it another way, that kinematics alone is sufficient for the analysis? green 12.30.216.138 16:25, 7 December 2006 (UTC).


 * I argue as follows: Let be a situation without any preasumptions. Now we introduce: a system, consisting of a light source, a grating, detector, shutter, comparator, telescope. We clone this system. The telescopes receive the others light. The grating deflects the own light and the others light. The detector compares the deflection. The shutter switches the lightsource on off. The relative pulse width is equivalent to the relative deflection, determined by the detector. The comparator determines which ones relative pulse width is greater. If the own PW is greater, the light is lit. Everything is at relative rest and symmetrical. One system pushes the other system, they now move relative one to another. Still everything is symmetrical. Now we change the setup. The systems differ only in mass. After they push each other, the will gain relative speed inverse to their mass, due to conservation of momentum. Now, what happens? The lights shine on, one is lit, both are lit? This experiment takes place in an empty univers, the physical laws are: conservation of momentum, constant speed of light, a closed system can not determine absolute movement from a single measurement. ErNa 08:58, 6 December 2006 (UTC)


 * The situation you describe is not the standard twin problem which assumes that the twins are independent -- that the traveling twin can move away without effecting the stay-at-home. In your version, both twins will actually be accelerating due to the forces acting on each, whereas in the standard problem only one twin is really accelerating although both observe acceleration of the other. For the stay-at-home twin, the observation of acceleration of the traveler is real because the traveler can confirm it, say using an on-board accelerometer, whereas for the traveler, the acceleration of the stay-at-home is only apparent, that is, the stay-at-home can confirm through internal measurements that he is not accelerating. green 12.30.216.138 16:53, 7 December 2006 (UTC)

Einstein also said: nature doesn't jump :-) What I want to show with this experiment is: First, I set up a symmetric experiment. In this case both twins underly the same processes. Therefore it should be right to say: both make the same observation. Then I change the preconditions slightly by giving one system a bit more of mass. If both still see exactly the same, why should something happen, if I increase the mass difference. In the end, one twin has the mass of earth, the other still only his mass and still both see the same. It is just not understandable, that to experiments with dramatically different setups should show the same results. ErNa 19:59, 7 December 2006 (UTC)


 * This may help. Consider two spacecraft juxtaposed in empty space, relatively at rest, with one having, say, three times the mass of the other. An astronaut onboard the more massive craft, of mass m1, pushes against the less massive craft, of mass m2. Note that the force acting on each craft is the same via the law of equality of action and reaction, and that the acceleration of the less massive craft is greater than that of the more massive craft in inverse proportion to their masses. E.g., using the original point of juxtaposition as a reference and assuming m1 = 3*m2, the ratio of accelerations of the smaller to larger craft in reference to the originating point, is 3 to 1. Hence, from the pov of either craft, their observed accelerations away from each other are identical. That is, unlike what I believe you conjecture above, kinematic symmetry continues to exist even if the masses are unequal (and, of course, net momentum (of zero) is conserved). green 12.30.216.138 00:40, 8 December 2006 (UTC)

What Do I want: I want to understand, why the world could never exist without a invariant speed of light, which can not be reached by matter.


 * Fwiw, the speed of light is invariant in SR but not in GR, although it still has a maximum speed of c. In SR, it can be shown that it would require an infinite amount of energy to accelerate a material particle to speed c. However, SR does not preclude particles that move at speeds greater than c, and cannot move slower than c. They're called Tachyons and have never been detected. green 12.30.216.138 08:12, 8 December 2006 (UTC)


 * Ok, ok, I love Ockham! To me, Tachyons are mathematical object without physical relevance. My questions are more basic. Relations can be differently expressed. Let there be two worlds and you can not travers the boundery: Then it doesn't matter, what happens in the other world. The only influence You feel is: your world is not unlimited. Therefor it makes no difference, if this other world exists or not. For simplicity I say: nothing is outside. That limits the number of movie plots, but that not my world. ;-) Let's make simple, but self consistent models. ErNa 09:39, 8 December 2006 (UTC)

It is hard to follow the threads of discussion and I did not study the links to kinematics. But I have a question: does kinematic symmetry mean: every observer measures the same in terms of time and distance or: they measure the same relative velocities? ErNa 07:29, 8 December 2006 (UTC)


 * Check the link kinematics. I think it means each twin observes (that is, measures) the same relative motion with respect to velocities and accelerations, although equal and opposite in direction. green 12.30.216.138 08:12, 8 December 2006 (UTC)


 * Without checking the link: Yes, I agree. And, the invariance of speed of light allows them to express the measured value as an relative number (and to communicate this information with a PWM-Signal of modulated light). But they also can send information about the measured distance. And now we have to agree: Do complete the experiment, it needs time. And during this time -the time span is: start experiment, stop experiment on both sides the do not measure local accelations, therefor the velocity doesnt change. Even more: we exclude gravitational forces, for these change velocity without being detectable by local accelerometers.
 * The main point in all these discussion is: is absolute space compatible to SR? Most physicists I get to know say "NO". Lets have to twins on inbound journey: They measure relative velocity and communicate the value. Equal. Both can determine their time span until they meet and the relative distance in the moment of determination of that time span. When they meet, they want to drink a beer. So they have to bring their relative velocity to zero. This can be done in a multitude of ways, that is, each one uses a certain amount of energy to break. They compare time spans and measured distance and they will be different (in general). Is it right to say: the one, who measured the greater value had a smaler velocity relative to an absolute frame and if they predicted the same timespan and distance and decelarated symmetrical, than they are at absolute rest in the sense, that every accelaration now dilates local time? Complicated! May be, not suffient ?ErNa 09:39, 8 December 2006 (UTC)


 * See the discussion higher on this page on CMBR. As Einstein already calculated in 1905, with SRT you obtain the same prediction for the clock indications on the clocks that the twins carry with them (assuming ideal clocks and negligible gravitational fields), no matter what inertial frame you chose (CMBR/sun/Sirius,...). Harald88 15:52, 9 December 2006 (UTC)

NPOV tag
Harald -

You see to be the only person around who considers the Unnikrishnan paper to be significant in the least. I especially refer you to the refutation of it as a reasonable source presented in talk:luminiferous aether. What I have come to conclude is that articles in marginal journals such as Indian journal in which Unnikrishnan published and the Australian journal in which the other counter-opinion was published are not reputable sources unless they are referenced in articles in mainstream peer-reviewed journals. You acknowledge that Unnikrishnan's paper is not cited elsewhere. How about the other one?

You have a case to make for the idea that there is any notable counter-opinion on the twin paradox, or than Einstein's view is of anything more than historical interest. Either do so or remove that tag. Otherwise I will remove it for you again. --EMS | Talk 22:36, 7 December 2006 (UTC)


 * EMS, as explained above (several times!), that paper is irrelevant for the NPOV tag. Do I need to copy the discussion that accompanies that tagging here? That issue started with  and was specified in [ :: As by now the discussion has become scattered, I'll copy the relevant parts again below in this section. [[User:Harald88|Harald88]] 10:54, 9 December 2006 (UTC)
 * BTW, you strangely claim to disagree with Builder on a point where you say quite the same as him; but in the article we should cite him on that as we can't cite you. And apart of your claim that the Australian journal of physics is not "reputable" being baseless, I also referred you to a similar, more condensed article by Builder in the American Journal of Physics that referred to the first. In that article he similarly rejected the GRT solution as bringing nothing new - but perhaps you are going to regard that journal also with suspicion from now on. Will you end up with claiming that only your favourite American journals are "mainstream" and "reliable"? Harald88 16:40, 9 December 2006 (UTC)


 * I am unfamiliar with the Unnikrishnan article. Nonetheless, I think the tag should remain because of the GR issue -- my contention that Einstein's solution in GR should be presented, with its warts, if any, discussed, and your contention that the twin problem is not an GR problem. I also am not convinced of the validity of SR solutions that fail to carefully analyze the behavior of the traveler's clock at turnaround. green 12.30.216.138 23:34, 7 December 2006 (UTC)


 * Green - I repeat that you are free to restore or replace the GR section if you like. I am largely going to defer to you on this page at this time.  You seem be a responsible editor, and I am happy to work with you.


 * I appreciate your comments, but from your previous statements concerning your professional background, I believe you are more knowledgeable concerning GR and its solution of the twin problem. For this reason, I hope you can find the time to add an informed GR discussion to the article. I will try to look over the other solutions, to see if they meet my "no handwaving" requirements. green 12.30.216.138 00:14, 8 December 2006 (UTC)


 * As for SR solutions that "ignore" the behavior of the traveler's clock at turn-around: They are assuming an instantaneous acceleration.  Whether that is physical or not, it is workable under SR and eliminate a lot of unnecessary and nettlesome details.


 * An instantaneous acceleration is definitely not physical, but this is not my issue. It is, rather, the requirement of some argument to justify what happens to the traveler's clock during this instant. green 12.30.216.138 00:14, 8 December 2006 (UTC)


 * Obviously those details get covered somewhat in the (now removed) "GR" section. Do note that the traveller's clock behaves as expected.  During acceleration it speeds up in the stay-at-home twin's reference frame until the traveling twin is at rest with respect to the stay-at-home twin, and then slows down as the relative speed builds up again.  I find that detail kind of trivial myself.


 * I'm probably wrong but I see it otherwise. Suppose both twins are in empty space and one uses a rocket to leave and return. This is still the same twin problem but I model it this way to get rid of a possible confusion; namely, the Earth's gravity field. If the traveling twin sudddenly screetches to a halt, I would imagine that he is momentarily in an intense gravity field (via the equivalence principle) and therefore his clock would effectively slow or stop! You claim the opposite; that from the pov of the stationary twin, the traveler's clock speeds during one acceleration and then inexplicably slows down on the reverse acceleration. I see no justification for the claim that the traveler's clock speeds up during periods of intense acceleration and then slows down during another intense acceleration in the reverse direction. That is, your claims makes no sense from the standpoint of the equivalence principle, and hence GR. I've no clue what we must appeal to if we wish to implement a pure SR solution. So now you see why I work on this article -- to see if anyone has really solved it! green 12.30.216.138 00:14, 8 December 2006 (UTC)


 * YES - The traveling twin is in a "gravitational field", at least in their own perception. However, in so far as an inertial observer is concerned, this is just the traveler firing their engines.  There is no spacetime curvature here, and no static gravitational potentials.  Therefore GR is useless here, and the twin's clock speeds up and slows again as a matter solely of SR, at least in the view of the stay-at-home twin.  Now if we revive my modified GR section, there is a description of how the traveling twin perceives the stay-at-home twin's time.  In that view, the stay-at-home time is hugely sped up during turn-around.  This asymmetry is present (once again) because the traveler is accelerated but the other twin is not.  I hope this clears things up. --EMS | Talk 04:50, 8 December 2006 (UTC)


 * Firstly, I revised my immediately preceding paragraph so I urge you to read it again. I think you will still say "YES" -- meaning that in your opinion there is no solution of the twin problem in GR. If so, I still think we need to include Einstein's "solution" and comment as its efficacy or lack thereof, and possibly discuss other proposed solutions in GR. Otherwise, the article is seriously incomplete. Secondly, as a factual matter, I am virtually certain you are mistaken in your claim that there is no solution in GR. I am aware of experiments with GPS clocks in which an orbiting clock is compared to an Earth-bound clock, and iirc, it was reported that the results confirmed the prediction of GR. Thirdly, if you are correct that GR is useless in solving the twin problem, then something is seriously awry. I can certainly pose the problem of a clock being moved in a gravity field and returned to its original location. It seems utterly implausible to conclude that such a "simple" problem cannot be solved in GR, when the very same theory is applied to all kinds of deep questions in cosmology and astrophysics. Fourthly, I do not understand the "perceptual" aspect of your solution. The fact that one twin accelerates and other does not, is not a state secret. Both twins know what the other is experiencing in terms of accelerations or not, so analyses dependent on mere "perceptions" seem wrong-headed. Iow, certainly for the GR case, the traveler is compelled to use the EP without assuming he is in a gravity field. He knows he is not in a gravity field because he surely knows the cause of his acceleration; namely, say, firing a rocket. Fifthly, and finally, I do not see how SR can be used to speed up and slow down accelerating clocks. Perhaps, this is explained in the article. In any event, I think we need to re-introduce the entire section of GR that was deleted, and try to determine what is valid and what should be revised and/or deleted. I am not at all confident in your claims, but I am looking forward to your edits of the GR section. Regards, green 12.30.216.138 08:00, 8 December 2006 (UTC)


 * Green - FIRST of all, you need to revise your way of responding to me.  YOU CANNOT edit your previous postings in a way that changes the meaning.  Even then, except for blatant typos, you should strike out the old text (using and ) and follow that with the new text.  You habit of inserting responses in the middle of another person's posting is also disruptive to following the flow of a thread.  If you want to clarify what you meant, then please DO SO IN A NEW RESPONSE!


 * Inserting responses within a paragraph is a fairly standard way of conducting a discourse on most message boards I have participated in. This is particularly useful if the original paragraph is of a compound nature. In such cases, I make an effort to keep all content of the compound message at the same indent level to allow the reader to see the original. However, I will try to miminize this practice. green 12.30.216.138 22:19, 8 December 2006 (UTC)


 * SECONDLY, it is way past time for you to get an account. It takes only a few minutes, and gives you a stable ID.  (If you go to another machine, your IP address will change.)


 * Perhaps it's an idiosyncrasy, but I don't want an account. However, I always use the same name. I try to indent my responses so the reader can easily see which comments I am responding to. I agree I should not edit previous comments in a way that changes their meaning. I didn't think I did that in the case above, but perhaps I did. green 12.30.216.138 17:49, 8 December 2006 (UTC)


 * THIRDLY, the twin paradox is fundamentally an SR exercise. See time dilation:  A moving clock ticks at a rate of $$t' = t \sqrt{1 - v^2/c^2}$$.  ALSO NOTE THAT THIS EFFECT IS FRAME-DEPENDENT, and I did specify that the effects on the traveler's clock were with respect to the stay-at-home twin's frame of reference.  In the traveler's frame-of-reference, his clock is always ticking at the "right" rate.  So as the traveling twin accelerates, the time dilation on their clock dimimishes for the first half of the acceleration (as the velocity away from the stay-at-home twim is diminished), and reappears during the second half of the acceleration (as velocity towards the stay-at-home twim builds).  Note that in the absense of massive objects acting as sources of gravitation, GR is idential to SR.  So this description is in fact a GR solution too.


 * Defacto, you have a succession of inertial frames of different velocities and the time dilations in these frames change as you allege. However, SR is a theory about transformations between inertial frames. If the frame velocity is varying, and you want to imagine a succession of frame changes, you need to explain the behavior of traveler's clock during the various accelerations. You can't have it both ways -- that is, use SR but have your clocks in one or several accelerating frames. Those that want a rigorous solution of the problem will demand that this issue be dealt with; not swept under the rug. I wonder what Harald thinks. green 12.30.216.138 17:49, 8 December 2006 (UTC)


 * Btw, even assuming several frames for the traveling twin and one frame for the stay-at-home, what in your analysis precludes a reversal of roles for each calculation, having a paradox as a result? green 12.30.216.138 19:12, 8 December 2006 (UTC)


 * Forget previous paragraph. The length contraction as seen by the traveling twin must be taken into account. green 12.30.216.138 19:24, 8 December 2006 (UTC)


 * FOURTHLY, while GR can be used to describe what the traveling twin sees during turn-around, it must dovetail with the results to the SR exercises. Once again, in this exercise, GR and SR coincide.


 * I strongly advise that you stop confusing yourself by worrying about GR. I know GR, and edit the general relativity article.  I see its use here as equivalent to swatting a fly with a sledge hammer:  It will work, but does so at a price. --EMS | Talk 16:19, 8 December 2006 (UTC)


 * With all due respect, unless you are willing to ignore the behavior of the traveler's clock at the turnaround and indeed during all accelerations, the twin problem cannot be solved solely in SR. Completeness demands a discussion of the traveler's clock during accelerations. Imo, this can only be done via an appeal to the EP. If the turnaround, say, is modeled as instantaneous and the acceleration infinite, I believe that the traveler's clock momentarily stops, and the numerical results of the calculations using SR are uneffected. green 12.30.216.138 21:52, 8 December 2006 (UTC)


 * I will find and provide you with the link to the Unnikrishnan article. It is in the history of several articles, including this one. --EMS | Talk 23:45, 7 December 2006 (UTC)

Green - You are getting yourself more confused as you go. The first issue is how the traveling twin is seen by the stay-at-home twin. That is a trivial SR exercise since the traveling stay-at-home twin remains in a single frame of reference the whole time.

The second issue is how the stay-at-home twin is seen by the traveling twin. That is also an SR exercise, with the change of reference frames at turnarounds needing to be accounted for. The accelerating observer view is needed if you want a detailed accounting of what happens to the traveling twin's view of the stay-at-home twin during turn-around. This accelerated observer view is what is often called the "GR solution", but in my mind is another variation on the SR solution. However, it does include the gravitational time dilation effect, which is strongly associated with GR but in fact was originally derived using SR. --EMS | Talk 20:39, 8 December 2006 (UTC)


 * You must mean above that the stay-at-home twin remains in a single frame throughout. Also, the exercise is "trivial" via SR provided you simply ignore that the stay-at-home sees, and knows, that the traveler experiences acceleration. I think the net result of how this effects the stay-at-home's calculation of the traveler's time dilation is zero for the reasons stated in my last comment above. Nonetheless, I don't regard it as a rigorous methodology to sweep this issue under the rug, which is the usual procedure if one wants to claim that SR is sufficient to fully solve the problem. green 12.30.216.138 22:08, 8 December 2006 (UTC)


 * SR is sufficient to fully solve the twin paradox. Period.  GR is a theory of gravitation due to spacetime curvature.  There is no gravitation due to spacetime curvature in this exercise, and for that reason GR is not needed here.  That said, there is a separate issue of whether this article is complete without the GR section, but that is an editorial concern instead of a theoretical one. --EMS | Talk 22:36, 8 December 2006 (UTC)


 * You are in error. Unless you are willing to deal with the acceleration of the traveling twin in a forthright manner, you are indulging defacto handwaving. I repeat; SR is a theory about how events transform between inertial frames, and any analysis that departs from using only inertial frames requires justification. Oh, I know; "the jump" is not a frame of reference. Let's call it by its right name -- a CLUDGE! What is in evidence here is something I see all-too-often on other message boards -- a slipshod approach by professionals to fundamental questions. It seems to characterize the culture of physics, particularly those who write books for the public. green 12.30.216.138 00:35, 9 December 2006 (UTC)


 * Unfortunately -- and no disrespect intended -- you apparently have little understanding of the issues we are discussing, and certainly not my position. E.g., I didn't write that I disbelieve SR (meaning the theory, as distinguished from some of Einstein's motivational statements); nor have I denied the famous equation; nor did I originate use of the phrase "(frame) jumping" to describe a common cludge for solving the twin problem using only SR; and so on. A good theorist asks himself the question as to what happens to the traveler's clock when he jumps frames, often modelled as instantaneous. Afaict, the EP provides a very plausible explanation. You and EMS enthusiastically offer no explanation other than defacto handwaving (not a good methodology imo) -- because you are both in denial. Gravity exists at the turnaround because the traveler is accelerating. green 12.30.216.138 05:33, 9 December 2006 (UTC)


 * Please sign your name even you don't have an account, if for no other reason than to create continuity with your previous statements. Perhaps English is not your native language which may account for the difficulty I have understanding your words. In any event, I never wrote, and did not intend to suggest that I reject the basic assumptions of relativity, so I see no relevance to your discussion about the famous formula. Also, for the clarity, my present opinion is that one needs SR and GR in combination to solve the twin problem. EMS says that Einstein dealt with the acceleration at the turnaround in 1907. Perhaps he could explain how. I see the need to use the EP, which I am assume came later. green 12.30.216.138 19:27, 9 December 2006 (UTC)


 * For clarification, I should add that I am convinced that some of Einstein's motivational statements for relativity are incorrect. E.g., we now know that absolute rest can be defined (wrt the CMBR frame). Although I accept the main results of SR including the Principle of Relativity, I am troubled by the clock paradox (which, btw, is distinguishable from the twin paradox notwithstanding what the Introductory section states). This is the case of twins separating symmetrically (equal and opposite accelerations) and returning. green 12.30.216.138 05:48, 9 December 2006 (UTC)


 * Green - I am rapidly reaching the end of my rope with you. I thought that you could help with this page.  Now I find that
 * You accept the anti-relativity notion of a prefered reference frame. (The CMBR frame is special, but it is not prefered.)
 * Abuse the correct notion of the traveling twin detecting a gravitational field during turn-around to create the incorrect conclusion that only general relativity can solve the twin paradox. (The only part of GR that is needed, gravitational time dilation, is derived from SR!)
 * Worry that the symmetric twin paradox could pull the rug out from under the whole business. (BTW - If you treat the symmetric version as a "triplets paradox" with the thrid triplet staying at home, the answer to the symmetric twin paradox becomes obvious.  The turn-around viewpoints do get interesting, but the end results are consistent.)


 * If you cannot accept the principle of relativity, or the work that has been done to date on this problem, then you have no business being here. --EMS | Talk 06:18, 9 December 2006 (UTC)
 * One does not need to agree with a theory in order to edit an article about it. Instead Wikipedia editors can edit any article and WP:sympathetic view was rejected. Wikipedia articles should reflect the "Neutral view" by correctly mentioning notable opinions as found in the peer reviewed literature. The debate above appears to have deviated from the purpose of this Talk page, which is for discussions about how to fairly describe these opinions in the article about them. Harald88 12:05, 9 December 2006 (UTC)


 * The debate is largely about what the solutions are, and whether their presentations are rigorous, so I don't see that we have deviated to any great extent about what this Talk page is for. green 12.30.216.138 12:55, 9 December 2006 (UTC)

--


 * EMS:


 * Wrt 1): Whether the CMBR is a preferred frame or not depends on a definition. I believe I defacto dealt with this issue when I stated that it can be used to define absolute rest (and universal time as well), but is NOT the unique frame in which the speed of light is c. So it definitely differs from the concept of preferred frame imagined by Lorentz when ether theories were in vogue.


 * Wrt 2): Fundamentally, my demand was (and remains) that one needs to forthrightly deal with the issue of gravitational time dilation. I did so using the EP. If there are other methods, or if it is actually dealt with in SR (where non-inertial frame are disallowed), the article should reflect and explicate this issue. Instead, the issue is generally shoved under the rug and the question never asked -- and surely not answered -- regarding the behavior of the traveler's clock at turnaround. Technically, I never claimed that only GR can deal with the twin problem. I inferred that both SR and GR seem necessary, but if this isn't the case, the argument must be made. Actually, this entire issue is one of rigor. I don't see why you resist it.


 * Wrt 3): I don't wish to get into this issue at this time. In my own work, I feel it is necessary to validate the consistency of SR wrt the symmetric twin paradox. You seem to hold it against me that I am asking myself a question.


 * Concerning your concluding remark, you should hold your head in shame -- not just for your blatant display of an attitude that discourages any line of thought that hints at non-conformism -- but also for your inability or unwillingness to read plain English. I wrote above that I accept the Principle of Relativity.


 * green 12.30.216.138 12:46, 9 December 2006 (UTC)


 * Green - Your saying the you accept the principle of relativity is just a bunch of useless words to me if then turn around and state that you accept the existence of an absolute rest frame. The two concepts are diametrically opposed.  I may as well say that I accept that the Earth is round, but I still worry about falling off of it's edge.


 * In accepting the PoR I am affirming that the laws of physics are frame independent. Iow, they have the same mathematical form in all frames. However, istm that the CMBR frame can be used to define absolute rest -- or if you prefer, universal rest. But afaict the CMBR frame has no preferred status wrt the laws of physics. Instead of sloganeering, please elaborate on the precise nature of the contradiction you allege that exists between the two concepts. Iirc, Einstein used the impossibility of defining absolute rest as a motivation for SR, but not expressly in any derivation. So the belief that absolute or universal rest cannot be defined is really part of the folklore of relativity imo, and its falsification does not, ipso facto, falsify relativity. green 12.30.216.138 00:45, 10 December 2006 (UTC)


 * As for non-conformism: If you take a look at my user page you will see that I am also something of a non-conformist.  However, I take great pains to distinguish between my ideas and those of the mainstream, and do not inject those ideas into content discussions.  I have no qualms about considering ideas that are outside of mainstream (or even mainstream consideration) to be inappropriate.  Wikipedia is not a soapbox.  I will tell you right now that my edits to general relativity survive becuase I do not inject my view that it is not completely right into the page.  Even The "Status" section of that article is defended by the scientists who edit here because it is a fair statement of the overall mainstream view of general relativity.  So I am asking no more of you in your editing and discussions than I am asking of myself! --EMS | Talk 22:30, 9 December 2006 (UTC)


 * What you state above is inapposite to the issues here. I'm not demanding anything that any rigorous thinker wouldn't expect. You're asking me to go away because I refuse to accept SR solutions that fail to explain what happens to the traveler's clock at turnaround, or that even acknowledge that there's a loose end that needs to be dealt with. Iiuc, you claim that Einstein discussed this in a 1907 paper. If so, then include a discussion of it as part of the "frame jumping" scenario; or minimally, let the reader know that an issue exists about the traveler's clock at turnaround. Instead, you aparently prefer to get on your soapbox and insist there is no issue. green 12.30.216.138 00:45, 10 December 2006 (UTC)


 * Einstein's GR turn-around discussion is in the 1918 article referenced in this article. The 1907 article only derived time dilation using SR.  Einstein did another variation on the theme in 1911, and that article may be found in, which is available in many larger bookstores.


 * As for the "issue" of the traveler's clock at turnaround: Wikipedia has a rule against original research.  You need to show me in the literature that there is an issue in this regard.  I can tell you right now that any accelerating observer is obliged to treat their clock as being at zero potential, and therefore locally experiences no gravitational time dilation.  So there is no clock issue for the traveling twin due to gravitational time dilation.  Instead, gravitational time dilation affects how the traveling twin perceives the behavior of the stay-at-home clock, and that is documented in the article.  Look at it that way:  It is not that your opinion is getting "swept under the rug" so much as Wikipedia cannot document one everyday man's view that a certain thing is wrong. --EMS | Talk 03:19, 10 December 2006 (UTC)


 * I think Harald can document critiques of the frame-jumping scenario. Hopefully, he will get back to us on this. Wrt gravitational time dilation, I assume it means that a clock in an accelerating frames will be calculated to run slower than, say, a clock in an inertial frame, as calculated by both twins. I don't understand your conclusion that gravitational time dilation is purely perceptual. Both twins know that the traveler is accelerating, so both should conclude that the traveler's clock will run behind the inertial clock if only acceleration effects are taken into account. green 12.30.216.138 06:00, 10 December 2006 (UTC)

-

Retake (edited copy-paste) of the neutrality disagreement as I brought up higher on this page.

I fully agree with EMS that Einstein's GRT solution is incorrect and that was also indicated as being the mainstream opinion. Nevertheless it is a notable (Einstein's!) opinion, it is still held by a number of teachers (I happen to know one) and it is still discussed in the peer-reviewed literature; it is also (although less accurately) discussed in the physics FAQ (The "General Relativity" Explanation, ; it has also been established that it is strongly connected to the origin of the paradox (see Herbert Dingle etc.). In short, it is necessary to include it. Details of Einstein's "GRT solution" can be moved to a separate history section or article but should not be removed from Wikipedia.

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 NPOV_tutorial).

Higher up on this page I already expounded that I don't care too much which articles are selected, as long as key opinions are justly represented. I know of no earlier modern mainstream opinion than the 1957 article by Builder according to which GRT "brings nothing", so that to me it looks most appropriate to at include at least that one. It's irrelevant if EMS thinks that Builder, Baez, Jansen etc. are mistaken and that their opinion should not be mentioned, their opinion is very notable to say the least. Similar with Einstein's "general POR" opinion without which this whole paradox wouldn't have taken off, and with which they disagree.

The most notable explanations that have been proposed in the scientific literature must at least be mentioned in order to be fair and as required by WP:NPOV. That includes Langevin's (Lorentz-based) absolute space explanation, Einstein's induced gravitational field explanation, and of course the Minkowski-based physical spacetime explanation (he was dead when this came up), which until now was only implied in the article instead of clearly attributed and which should be presented as the currently most common view.

And in answer to green: Like you, I also object to shoveling notable opinions under the rug. Upon instigation by Moroder, EMS and Shuba appear to attempt to limit the discussion to the textbook calculation exercise, which can hardly be called "paradoxical". The paradox touches the foundations of physics and caused intense debates. As a result, textbook authors may justify to themselves that the real issues are too difficult for the students or not important for their training. Still, during half a century it has caused much contention among physicists, so much that it requires to spend a lot of time just reading the literature about it. Presenting such a key contention piece as a (rather basic) calculation exercise in SRT, carries the suggestion that people who thought more of it -such as Einstein- either misunderstood the paradox or special relativity. Such a superficial discussion of the issue unfairly treats the different opinions that have been brought forward in the literature.

Harald88 17:23, 9 December 2006 (UTC)


 * Harry, what the three of us objected to is your tireless (and futile) attempt to cast doubt on Einstein's relativity. If you want a return to Lorentz's relativity, the time is past and putting your NPOV tags all over articles doesn't change the realty. Your tireless digging up "proofs" from obscure or blatantly incorrect papers and the attempt to include these papers in favor of YOUR OWN POV has become clear to quite a few of us (EMS,Shuba,DVdm,Moroder). So, it is really funny to see you claiming NPOV when your edits reek of POV :-) Moroder 17:25, 9 December 2006 (UTC)


 * Harald -- Thanks for your comments. I think we're in basic agreement here. The article needs to be comprehensive and this requires a summary of the basic issues of contention. It might turn out to be a long article, but so what. Many articles in Wiki are lengthy. If well-organized, the reader can pick and choose without getting confused. About the textbook solutions -- iirc, the ones using SR alone (which is most, of course), indulge the "cludge" and handwave or ignore the issue of acceleration at the turnaround. EMS claims to be a physicist, so I don't understand why he doesn't see the insufficiency of this approach and the need to be rigorous. green 12.30.216.138 19:38, 9 December 2006 (UTC)


 * Green, the hard fact is that a large group of physicists (represented on Wikipedia by Moroder,EMS,Shuba,DVdm) think that the Twin paradox is just about calculations in special relativity and ignore the differing POV's that Einstein and Langevin were exposing regarding the Twin paradox. For that reason a large part of this article must be accorded to that superficial view. Moroder nevertheless shows to have heard about the differing POV's; and he is kindly requested to help fairly describing them as is required on Wikipedia, in stark contrast with his above comments.
 * The twin paradox is one of the trickiest ones around; people typically go through different levels of understanding of it, every time changing their opinion, but many don't get further than the first or second level of understanding. For that reason it is totally unaceptable that some authors who never deeply studied this subject make claims about Truth in this matter -in complete defiance of Wikipedia policy.
 * Note that I still agree with EMS and Tim Shuba that the historical aspects don't need as much coverage on the entrance page of this article; most readers will just want to know the textbook solution of the problem, and the history that reveals the deeper issues can be discussed separately. Harald88 18:06, 10 December 2006 (UTC)


 * There are quite a few of us, professional physicists that see no reason for your speculations about "points of contention". Wiki is not a blog, nor is it about speculation, EMS has done a very good job and I have shown the rigorous treatment of "acceleration at turnaround". See below. Moroder 20:34, 9 December 2006 (UTC)


 * I think that Moroder has hit the nail on the head here. I admit that I did think that Einstein's GR solution was mistaken at first, but on closer inspection found that I had been mistaken on that point instead.  My current objections to Einstein's "GR" solution are that it goes twice around Robin Hood's Barn to get to the same place, and fails to use GR itself in the process.  My objection to the articles refuting Einstein's view is that they raise a very silly point (questioning how a purely perceptual field can instantaneously vanish everywhere in the universe when the observer's perception changes), and are published in obscure journals whose peer review is apparently quite minimal.


 * So I agree with Moroder that we have no business declaring that "points of contention" exist which are not accepted as such in the mainstream at all. The existence of a "significant minority" which holds those views need to be shown, and this includes showing that those articles are being cited elsewhere. --EMS | Talk 03:32, 10 December 2006 (UTC)


 * EMS, please stop with claiming that articles are wrong and journals are poor just because you don't understand their arguments which actually correspond to yours. Apart of that, it will be no problem to provide a citation list, especially the American Journal of Physics paper should have quite some thanks to its higher distribution. Harald88 16:57, 10 December 2006 (UTC)


 * My take is slightly different from EMS's above, though the conclusion is the same. We already have the problem set up and resolved in special relativity.  This means we are implicitly assuming that curvature can be neglected.  In the context of general relativity, this means that the manifold is flat and that the Riemann tensor is zero.  Therefore the "GR" solution has to be the same as the "SR" solution.  This is a mathematical fact.  Whether or not Einstein in 1918 made some conceptual or other mistake is at best a historical curiousity.  The physics is clear - if there is a "SR" solution, it has to be computationally identical to the "GR" solution. Tim Shuba 04:38, 10 December 2006 (UTC)


 * As I argued below, earlier, there is a bug in the argument that the twin problem can be solved by complete reliance on SR. Also, wrt to Einstein's GR solution, to the extent that it depends on the instantaneous (or even lightspeed) propagation of the gravity field when the traveler accelerates -- which is what I recall reading in the old GR section -- this is not correct and stems, I believe, from a misapplication of the EP. Basically, the EP is a local principle and states that absent any additional knowledge, an observer cannot distinguish the effects of gravity from acceleration. However, in the twin problem, the traveler knows he is accelerating. Therefore, the most anyone who knows about the traveler's acceleration can conclude (both twins btw), is that clocks will slow down in the accelerating frame, as compared, say, to an inertial frame. The acceleration is absolute and known to both twins. There's no instantaneous propagation or vanishing of a non-existent gravity field. And the discussion about "perceptual fields" to fix the error (which is misapplication of the EP) only compounds the confusion. green 12.30.216.138 05:47, 10 December 2006 (UTC)


 * Green, Einstein asserted that the traveller could claim to be "in rest" all the time, so that acceleration is relative. That is at the basis of the Twin paradox, as he himself indicates in his paper. Harald88 16:57, 10 December 2006 (UTC)


 * What, some more stories from harry and green? No math? Let me help you out a little.Now, there is an easy way to deal with the "Green effect": please calculate on your own what the effect would be (hint: make use of the fact that the rocket accelerates from 0 to v with constant acceleration +a and decelerates symmetrically from v to 0 with constant acceleration -a). This calculation should take care of the sequential transition thru frames. What do you get as a net effect? Moroder 17:11, 10 December 2006 (UTC)


 * To Harald: Sure, but going beyond the kinematic symmetry, my point was that in his alleged GR solution, 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. I explained why this is the case in my comments above. Let me know what you think. green 4.227.136.248 19:50, 10 December 2006 (UTC)

I now have a first feedback to EMS about the opinion of Builder that he deleted: According to Web of Science, Builder's article "The Resolution of the Clock Paradox" in Aus.J.Ph 1957 has been cited 12 times, and his summary of it with the same name in the Am.J.Ph. 1959 10 times (Amer.J.Phys.1959, 27, p.656.). He also published that year a paper with that title in Philosophy of Science. Interestingly, one of the people referring to it is Hafele (of the Hafele-Keating experiment).

I now also discovered a good overview article of the paradox that will be valuable for fairly describing the different opinions: we can largely follow its summary of the history of this paradox as he needed to provide a full historical context. It is CHANG HS, A MISUNDERSTOOD REBELLION - THE TWIN-PARADOX CONTROVERSY AND HERBERT DINGLE's VISION OF SCIENCE, STUDIES IN HISTORY AND PHILOSOPHY OF SCIENCE 24 (5): 741-790 DEC 1993. Harald88 20:22, 12 December 2006 (UTC)

Shuba
The term "special relativity" is the name of a particular theory, not any theory. It's not generic. Hence, it is a proper noun and therefore should be capitalized. Also, SR predicts differential clocks rates. "Differential aging", which is explicitly stated immediately thereafter, follows from the differential clock rates. Please revert to what you edited. green 12.30.216.138 05:45, 8 December 2006 (UTC)


 * Green - There are very explicit rules for capitalization in scientific journals. What they state is that the names of theories (or rather the words in the names of theories) are not to be capitalized unless they are a proper noun or are derived from a proper noun.  "Special relativity" is just a noun, not a proper noun.  (The word "special" was capitalized in the previous sentence because the rule that the first letter in a sentence is capitalized takes precedence.)  Examples are general relativity, time dilation, and even the twin paradox.  Capitalization examples include the Lorentz tranformations, Minkowski metric, and Einstein tensor.  I also think that the term "differential aging" serves the reader better.  At the least, you and Tim should hash this out.  Often a resolution is found that satisifes both parties but which neither one thought of at first. --EMS | Talk 22:29, 8 December 2006 (UTC)


 * If the rules in scientific journals are as you claim, they are in error. A proper noun is the name of something specific. Why is "Lorentz transformation" capitalized? Because it is a specific type of transformation. Why is "time dilation" not capitalized? Because it refers to something non-specific -- what we find in GR or SR. In any event, it's not an important issue. Wrt your other point, I made the edit partially in response to something you previously wrote on this mb. I give the reader credit for being able to think and chew gum at the same time. Thus, it is better imo to state that SR predicts "differential clock rates", as this is what it specifically does! But for those who find obscure the relationship of differential clock rates and aging, I linked the ideas directly in the text. Again, this is not an important issue and we can leave the text as is. green 12.30.216.138 00:35, 9 December 2006 (UTC)


 * Huh? "Lorentz" is capitalized because it's a man's name. Ditto for Minkowski, and Einstein. —wwoods 03:08, 9 December 2006 (UTC)


 * Please see proper noun. The gist is that while the names of people and places are proper nouns, the names of scientific theories are not. --EMS | Talk 06:25, 9 December 2006 (UTC)


 * The link does not necessarily imply what you attribute to it. green 12.30.216.138 13:03, 9 December 2006 (UTC)


 * I won't speak for the link itself (as a theory can be considered an entity under the definition given there). What I can tell you is the scientific journals have chosen not to consider the names of theories to be proper nouns.  --EMS | Talk 22:11, 9 December 2006 (UTC)

Confusion
I can not decide who else is confused besides me! I make no progress and retire! ErNa 21:37, 8 December 2006 (UTC)

Proper mathematical treatment of the paradox for accelerated rockets
Reading the never ending debates on the lack of proper treatment of the acceleration at the turnaround point I decided to give one. This excellent treatment belongs to User:DVdm and I only made a few minor corrections. I suggest that it gets recast in math format and it gets included in the main body of the Twins paradox. Please check the math:

We have a clock K associated with the "stay at home twin". We have a clock K' that whizzes by at some speed v when both clocks are set to show 0.

Phase 1: Clock K' keeps coasting at this speed during some time T according to clock K.

Phase 2: Clock K' fires its engines in the opposite direction of K, during a time A according to clock K until it is at rest w.r.t. clock K.

Phase 3: Clock K' keeps firing its engines in the opposite direction of K, during the same time A according to clock K, so K' regains the same speed v w.r.t. K, but now towards K

Phase 4: Clock K' keeps coasting at speed v during the same time T according to clock K until it passes by K so they can compare times. Knowing that the clock K remains inertial (stationary), the total accumulated proper time of clock K' will be given by the integral $$\int \sqrt{ 1 - [v(t)/c]^2 }dt \ $$where v(t) is the velocity of clock K' as a function of t according to clock K.

This integral can easily be calculated for the 4 phases:

Phase 1 ==> $$T * \sqrt{ 1 - v^2/c^2 }$$

Phase 2 ==> $$c / a * \text{argsinh}( a A/c )\,$$

Phase 3 ==> $$c / a * \text{argsinh}( a A/c )\,$$

Phase 4 ==> $$T * \sqrt{ 1 - v^2/c^2 }$$

where a is the proper acceleration, felt by clock K' during the acceleration phase(s).

There are the following relations between v, a and A:

$$v = a A / \sqrt{ 1 + (a A/c)^2 }$$

and solving for v,

$$a = v / ( A \sqrt{ 1 - v^2/c^2 } )$$

$$A = v / ( a \sqrt{ 1 - v^2/c^2 } )$$

So the travelling clock K' will show an elapsed time of

$$2 T \sqrt{ 1 - v^2/c^2 } + 2 c / a * \text{argsinh}( a A/c )$$

whereas the stationary clock K shows an elapsed time of

$$2 T + 2 A\,$$ which is, for every possible value of a, A, T and v, larger than the reading of clock K'.

The above treatment accounts properly for the acceleration at the turnaround point.Moroder 16:13, 9 December 2006 (UTC)


 * Thank you for this presentation. Iiuc, according to SR the proper acceleration of the traveler is required to fully and correctly calculate his time dilation as seen by the inertial observer. If so, is this result consistent with models of instantaneous frame jumping, where, iirc, the instantaneous infinite acceleration is claimed to have no effect on the time dilation? I believe that this is indeed the case, and we get the correct answer in the jumping scenario because the accumulated infinitesimal accelerations represented by the integrand, are compensated for by the resultant larger net velocities back and forth. If so, EMS is correct that SR is sufficient to solve the problem, but the frame jumping model is seriously misleading in its suggestion that the acceleration at turnaround has no impact on the final result. If my assessment is correct, this is not at all surprising since frame jumping is a cludge applied to simplify the calculation, but does so at the expense of real understanding. green 12.30.216.138 01:13, 10 December 2006 (UTC)


 * The frame jumping can be obtained immediately from the complete treatment I gave above. One needs to take the limit for A (the time used for acceleration) to 0. In this case one gets the well-known result $$2T \sqrt{ 1 - v^2/c^2}$$ . So, User:EMS is correct. Can we put this issue to rest now? Moroder 01:40, 10 December 2006 (UTC)


 * The issue, as always, is the article, and whether it adequately addresses this issue. To apply frame jumping without adequately explaining its justification is, imo, unacceptable. green 12.30.216.138 03:06, 10 December 2006 (UTC)


 * After considering this issue further, it seems that the integrand represents a succession of inertial frames, each differing from its successor by a small but finite change in velocity. When we go to the limit and integrate, we now have an infinite set of such frames differing by infinitesimal velocities. In effect, we have an infinity of infinitesimal frame jumps. The problem here is not mathematical. The integral converges and we can show that this is equivalent to, say, one macro frame jump at the turnaround. Correct me if I am wrong, but to conclude that the full integration over the phases you've defined above represents the actual time dilation of the traveler's clock as calculated by the stay-at-home, we must assume that the traveler's clock remains uneffected by the jumps. That is, if we rely exclusively on SR, we are making a physical assumption concerning how accelerating clocks behave in the absence of any theoretical justification. In sum, although I find your calculations of interest, I am now of the opinion that one needs GR to rigorously solve the twin problem. green 12.30.216.138 05:27, 10 December 2006 (UTC)


 * This is the standard treatment of slowly uniformly accelerated motion in SR. It appears in most grad textbooks on relativity, I could give you several links to the classnotes at Texas U, Harvard and Cornell that treat the subject in detail. It is pretty much mainstream physics, if you wish to speculate otherwise...This is also the foundation of the "slow transport" clock synchronization, clocks that are accelerated slowly are left unaffected by the slow acceleration/deceleration incurred when bringing them together. As to whether this phenomenon is physical, it was fully verified by the Haefele-Keating experiment and by its reenactments as well as by the GPS. When it comes to physics nothing is more compelling than experimental confirmation. If you wish to further dispute this issue, you know the path: you will have to find or setup and experiment that contradicts the theory of slowly accelerated bodies in SR. If you do that, all the textbooks will have to be re-written :-) Moroder 05:47, 10 December 2006 (UTC)


 * Are you sure you're not stretching the truth when you claim that a slowly accelerated clock is uneffected by the acceleration? This is puzzling since GR predicts that clocks will run slower due to gravity (compared, say, to inertial frames). Has your experiment falsified the EP? Moreover, iiuc the SR calculation above indicates a net time dilation that is dependent on changes in velocity (velocity is explicitly time dependent), even small ones. In any event, I was not disputing that the SR calculation gives the correct answer; rather, I was pointing out that frame jumping has no theoretical justification within SR. The king has no clothes! I think we need GR, and if the treatment is careful it will presumably give a result that is identical with SR. It's not that the SR treatment would now have theoretical justification because GR presumably gives the same answer, but rather the reverse; that GR provides the theoretical justification and we have serendipidously found a shortcut for calculating it using SR. I am aware that the texts generally use frame jumping, but I believe that there's contention about this procedure in the literature. I hope Harald can document it. green 12.30.216.138 06:37, 10 December 2006 (UTC)


 * Yes, I am sure. You conveniently ignored my references to experiments. You also ignored the fact that if you dispute this, you will need to run your own experiments. As an aside, the title of the treatment says nothing about SR vs. GR, it just says that is the standard relativistic treatment for accelerated bodies. BTW, "we have not calculated anything", you have not written one line of calculations, you simply write philosophy, in the end you are arguing semantics : whether the solution belongs to SR or to GR. Since SR is included in GR, you can take your pick...If the textbook explanation of uniformly accelerated motion via the succession of inertial frames offends your senses , feel free to call the solution a GR solution. Moroder 07:04, 10 December 2006 (UTC)


 * Your resounding "Yes" is, to say the least, puzzling, because it would falsify the EP if slowly accelerating clocks experienced zero time dilation effects. But why worry about trifles? ... The reason I think the SR calculation works and is confirmed by experiments is because it implicitly assumes that the traveler's clock is uneffected by frame jumps, aka accelerations, and this assumption is likely an excellent approximation to physical reality even though, as I have stated, it is neither affirmed nor denied by the theory we call "SR". That is, the calculation is likely an excellent approximation because the SR effects swamp the GR effects by many orders of magnitude. In this connection, the GPS experiments with atomic clocks must require the disentangling of the SR and GR effects. ... Oddly, you now insist that the calculation is not SR or GR, when it clearly uses the SR formula for time dilation, and integrates for a time dependent velocity in the absence of gravity. Mere semantics? ... The textbook explanation and some of the conventional wisdom offered here offends my sense of rigor since the assumptions are not clearly spelled-out, to our collective detriment and the readers as well. It doesn't offend yours because your haughty attitude is indicative of someone who defacto supports the "shut up and calculate" school of physics, and anyone who does otherwise indulges (by your lights) mere "philosophy". green 12.30.216.138 08:28, 10 December 2006 (UTC)


 * If you bothered to read Neil Ashby's paper on GPS or wiki's article on the Haefele-Keating experiment you would have found out that indeed, the gravitational effects are being considered and are orders of magnitude smaller than the acceleration effects. In either case, the exerimental results agree with a very high level of precision with the calculations. So, one last time, if your "senses are offended" feel free to run an experiment that refutes this mainstream application of relativity. This is the only way to prove your point. Good luck Moroder 15:54, 10 December 2006 (UTC)


 * I didn't need to read the paper on GPS. As you presented the results, it appears to falsify the EP and you have not responded to this issue. This is the way it goes in the physics culture today. It's worse than a bad political debate. Fwiw, I read years ago about GPS experiments that confirmed time dilation for atomic clocks. I don't recall whether the confirmation was for SR, GR, or the composite of both theories because I think the effects are in opposite directions; that is, SR predicts the orbiting clock slows down due to its high velocity but GR predicts it speeds up (both results compared to the stationary clock) due to the lower gravity field in orbit. In any event, what we're discussing now is whether slowly accelerating clocks show absolutely no evidence of time dilation. There has to be some effect due to acceleration or else the EP has been falsified. I see you conveniently ignored this point and I have to conclude you are likely misrepresenting the result. Perhaps the experiment was not sensitive enough or simply not designed to see the EP effect. I'll try to look at your link later today. You also have not dealt with my contention that the SR calculation presented above works because it is an excellent approximation that ignores gravitational time dilation effects. green 12.30.216.138 16:22, 10 December 2006 (UTC)

Of course, why read when you can shut your eyes and ears? From the Haefele-Keating experiment page:

The equations and effects involved in the experiment are:

Total time dilation
 * $$\Tau = \Delta\tau_v + \Delta\tau_g + \Delta\tau_s$$

Velocity
 * $$\Delta\tau_v = - \frac{1}{2c^2} \sum_{i=1}^{k}v_i^2 \Delta\tau_i$$

Gravitation
 * $$\Delta\tau_g = \frac{g}{c^2} \sum_{i=1}^{k} (h_i - h_0) \Delta\tau_i$$

Sagnac effect
 * $$\Delta\tau_s = - \frac{\omega}{c^2} \sum_{i=1}^{k} R_i^2 cos^2 \phi_i \Delta\lambda_i$$

Where h = height, v = velocity, $$\omega$$ = Earth's rotation and τ represents the duration/distance of a section of the flight. The effects are summed over the entire flight, since the parameters will change with time.

See, they calculated the independent effects. Now, you came up with an additional effect, we will call it the "Green effect" : uniformly accelerated clocks exhibit a slowdown. OK, calculate its order of magnitude and add it to the above effects.The Neil Ashby's paper on GPS can be found here: http://relativity.livingreviews.org/open?pubNo=lrr-2003-1&page=node5.html Now, there is an easy way to deal with the "Green effect": please calculate on your own what the effect would be (hint: make use of the fact that the rocket accelerates from 0 to v with constant acceleration +a and decelerates symmetrically from v to 0 with constant acceleration -a). What do you get as a net effect? Moroder 16:35, 10 December 2006 (UTC)


 * After posting my last comment above I looked at the link you provided, Haefele-Keating experiment, and immediately confirmed my suspicion that you egregiously misrepresented the reported experimental result. The experimenters claimed to have confirmed the combined predictions of SR and GR, calculating each independently. This is surely not what you claimed they verified. Here is YOUR ORIGINAL COMMENT: "... clocks that are accelerated slowly are left unaffected by the slow acceleration/deceleration incurred when bringing them together." Although this result might conceivably occur for the combined effects in the context of the particular magnitudes of the velocities and accelerations used in the experiment, there is nothing in this result to prove or even remotely suggest the general conclusion you presented as proven fact. Let me state it again since you apparently didn't get it notwithstanding two attempts on my part; if what you claim were true, it would mean that the EP has been falsified. It is foolish to mockingly refer to the "Green effect" as meaning that "uniformly accelerated clocks exhibit a slowdown". The uniform acceleration produces a phenomenon indistinguishable from gravity via the EP. Hence, a clock in such an acceleration-induced gravity field should run slower than a stationary clock if the EP is true. I advise anyone interested in this discussion to read the link and verify my conclusion. green 12.30.216.138


 * Ah, the art of diversion. We are so lucky that physics is based on math and not on never ending blabber. So, once again (with all the hints) : please calculate on your own what the effect would be (hint: make use of the fact that the rocket accelerates from 0 to v with constant acceleration +a and decelerates symmetrically from v to 0 with constant acceleration -a). Additional hint : this calculation in no way invalidates EP, quite the opposite, it should make good use of it. What do you get as a net effect? Moroder 19:12, 10 December 2006 (UTC)


 * I find it hard to believe you're a physicist (one of your claims iirc). Why bother calculating what the experiment allegedly measured -- clocks exhibiting the time dilation predicted by relativity. Further, what you originally wrote was erroneous. If there were no GR time dilations on the cumulative round-trip that summed to a non-zero value (ignoring SR velocity-dependent effects), the EP would be falsified. Note that these dilations do not distinguish between accelerations and decelerations since both produce a gravity type time dilation effect. green 4.227.136.248 20:02, 10 December 2006 (UTC)


 * Ha,ha,ha. We were discussing your "green effect", i.e. your contention that there is a series of infinitesimal "frame jumps" that are unaccounted for, remember?.We are not discussing the GR explanation of TP. This is why I gave you the simple exercise above. But you are still waffling, no way that you would do any calculation, with all the hints I gave you. One last hint: apply EP to the "green effect", in the sequence of frames that vary from +a to -a . So how about you grace us with some computations?Moroder 20:12, 10 December 2006 (UTC)


 * Your use of language and links is so convoluted that I confess I am no longer certain exactly what you are claiming or disputing. I stated awhile back that the SR frame jumping calculation works because it assumes -- without theoretical justification -- that the clock remains unchanged during jumps, and that this is likely an excellent approximation because the SR velocity effects swamp the GR acceleration effects. I also (implicitly) claimed that there is a non-zero gravitational time dilation for the round-trip -- which is my current best candidate for what you energetically disputed via use of a totally inapposite link, and then labeled, I think, the "Green effect". Correct so far?


 * Assuming we are now recalibrated, since changes in velocity during jumps, aka accelerations. produce the effects of gravity wrt time dilation, and since the effect does NOT depend on whether the traveling twin is leaving or returning, I see absolutely no plausibility in your claim that the GR time-dilation effects could sum to zero on the round-trip. You really need to offer a plausibility argument before I would consider doing a calculation. Please be advised that what you call "blabber" is what Einstein and other competent physicists referred to, and still do, as a "thought experiment". green 4.227.136.248 20:38, 10 December 2006 (UTC)


 * Let me make it really simple for you: the rocket flies in a straight line and passes thru a sequence of IRF's at acceleration +a for a distance D/2 and thru another sequence of IRF's at acceleration -a for the same distance D/2 (this describes the rocket accelerating from 0 to v over D/2 and decelerating from v to 0 over D/2). Using EP (and some little calculus) what is the accumulated time delay? You challenged the validity of the textbook infinitesimal calculation approach, I am asking you to prove your challenge with calculations. Enough prose Moroder 22:57, 10 December 2006 (UTC)


 * Off the top of my head I don't know what the accumulated time delay is, nor does it matter. I am merely claiming that if there is a persistent, albeit changing acceleration during the journey -- one way or round-trip -- by the EP the traveler's clock rate will be slower (by varying amounts) as compared to the stationary clock. This, of course, will be a GR effect only, and although I am unfamiliar with the GR calculation, it is independent of the SR calculation according to literature on the subject; e.g., your link has it independently calculated! At the conclusion of the journey, GR related clock rates will be identical but not the elapsed times as measured by both clocks. The number calculated is irrelevant. If you find any of my assumptions incorrect, please state which ones and cease your petulant demand for a calculation. Thought experiments were not scorned by the great physicists and I am losing patience with this discussion. green 12.30.216.138 23:34, 10 December 2006 (UTC)


 * I don't know what your game is. Above you reproduced from your link the equations for the SR, GR, and Sagnac effects on time dilation and they are clearly independent effects. One of my claims, confirmed by your link, is that the effects are independent and therefore an SR-only calculation would be insufficient, albeit a good approximation. If I have erred in some conceptual way, please indicate where and in what manner. green 12.30.216.138 23:45, 10 December 2006 (UTC)


 * Ah, the never ending diversions, the discussion is about the usage of accelerated IRF's, try to stick to the topic. There is no Sagnac effect and we can safely neglect the gravitational effect as well. You challenged the textbook treatment that uses the infinitesimal approach. You claimed and continue to claim that using the sequence of IRF's is prone to some error due to "frame jumping", this is what I am trying to discuss with you. I challenged you to prove it experimentally - no dice. So, I tried to help you giving you different hints (for example, the Pound-Rebka experiment contains a very useful formula, this is why I quoted it, not in order to show that there is a superposition of effects but you didn't get the hint). I gave you a very simple exercise to calculate but you wouldn't do any calculation. Is it because you are unable to? You cannot disprove a method unless:


 * -you run an experiment (which you wouldn't do)


 * -you write a mathematical disproof (which you wouldn't do either)


 * Repeating the same mantra wouldn't cut it. All prose and no math makes for a zero argumentMoroder 23:59, 10 December 2006 (UTC)


 * It's unproductive to ask me in this format to do an experiment. We can't get anywhere if you take this approach. Further, if the SR formula is sufficient to account for the GR gravitational dilation effect, why did the experimenters in your link calculate the SR and GR effects independently??? Odd, to say the least. Maybe they don't know what you know. Let's forget about anything I believe, wrote, or claim. Instead, given your knowledge of the subject, please explain -- based on first principles -- how an infinitesimal approach using SR formulas alone, can account for the GR effect of gravitational time dilation. Why would it? Perhaps it does, but one needs an argument. Apriori, I would think the SR calculation is an approximation, and your link confirms my intuition. Finally, I think you need to be reminded that the mathematics follows from the argument or assumptions, not the reverse -- something they don't teach in the "shut-up and calculate" schools of physics. If we get our assumptions right, there's really no need to do any calculations. green 12.30.216.138 00:32, 11 December 2006 (UTC)


 * No, we cannot forget "anything I believe, wrote, or claim" . You claimed that there is a residual effect due to acceleration and that the textbooks are wrong. Once you back up your claim (with math, not with more prose), I will answer your new and unrelated question. So, stay on topic, stop shifting subject, prove your point or concede and I will answer your question Moroder 00:39, 11 December 2006 (UTC)


 * LOL! A "new and unrelated question?" Hardly. Btw, I didn't claim that the textbooks are wrong; only that they present an SR-only calculation that imo is an approximation. GR is usually above the reader's level. Maybe I rely too much on experts. I've read lots of stuff over the years that claim that the SR and GR effects are independent, and your link is another of many data points in this connection. I don't know how to use the EP to do the calculation, so I await your pearls of wisdom. I want to see not only that it gives the same result as the SR calculation, which is what I think your claim is, but how the SR calculation can magically account for the GR effect. As I said, this seems apriori implausible. I have nothing to concede because I stated what I believe, and continue to believe, is the case, even if I am unable to prove it at this time -- that the SR calculation is an approximation that doesn't include the GR effects. If you can prove me incorrect, so be it. green 12.30.216.138 01:12, 11 December 2006 (UTC)

Here is exactly what you wrote:

"After considering this issue further, it seems that the integrand represents a succession of inertial frames, each differing from its successor by a small but finite change in velocity. When we go to the limit and integrate, we now have an infinite set of such frames differing by infinitesimal velocities. In effect, we have an infinity of infinitesimal frame jumps. The problem here is not mathematical. The integral converges and we can show that this is equivalent to, say, one macro frame jump at the turnaround. Correct me if I am wrong, but to conclude that the full integration over the phases you've defined above represents the actual time dilation of the traveler's clock as calculated by the stay-at-home, we must assume that the traveler's clock remains uneffected by the jumps."

So yes, the traveller's clock is unaffected by the succession of frame jumps as a net effect, i.e. after integrating the whole path of the traveling twin. This is the core of the discussion. Since you cannot prove the opposite mathematically (at least you admitted that you don't know how to apply EP and simple integral calculus to do this) and since you would not concede that what you claim is wrong and you "LOL", I will leave you "LOL"-ing Moroder 01:40, 11 December 2006 (UTC)


 * You missed my points entirely; namely, 1), that since the traveler's clock time is undefined at the multitude of jumps, the method itself needs additional theoretical justification (a foundational type issue they don't consider in the "shut up and calculate" school); and 2), an explanation is needed as to how the gravitational dilation effect is included (if it is) in the SR-only calculation. You seem to think that because the traveler is uneffected by the succession of frame jumps, that you have therefore answered point 2). Btw, I am now somewhat tending to the opinion that it might just be so. If I were certain I was wrong, I would certainly concede. However, the fact that I cannot do the EP calculation does not thereby create in my mind the certainty that would imply the outcome of your desire. green 12.30.216.138 02:35, 11 December 2006 (UTC)

Argh, another attempt to a diversion, now you say:


 * You missed my points entirely; namely, 1), that 'since the traveler's clock time is

undefined at the multitude of jumps'

How do you know it is undefined? Please spare me the standard crank answer : "because my intuition is... ". You need experimental proof for that. Which you don't have Moroder 03:17, 11 December 2006 (UTC)


 * I know it's undefined because you have not defined it. As you go to the limit in your model, that is, as the number of inertial frames goes to infinity, you, the unconscious model-maker, have not specified whether the twin's velocity is the higher or the lower at each jump point. This is not an experimental issue, but a conceptual one having to do with your model. green 12.30.216.138 06:26, 11 December 2006 (UTC)


 * I don't have to define anything, the onus is on you to prove that it ain't so. I gave you all kinds of hints but since you cannot calculate, you will resort to this never ending bartering. The origin of your cofusion is that you identify the sequence of "frame jumps" with a discontinuity in the functionality of the rocket clock notwithstanding that experiment (Haefele-Keating experiment,GPS) shows that nothing like that occurs. The constantly accelerated motion does not result in speed discontinuities (another hint : a=const means v=at/sqrt(1+(at/c)^2) which is a continous function). To recap, in order to prove your point you need to:

-disprove existent experimental knowledge (good luck with this one)

-disprove that uniformly accelerated motion results into a continous transition between IRFs (good luck with this one)

-run at least one experiment that would prove your "gut feel" (which you wouldn't and couldn't do, by your own admission)

-prove mathematically that acceleration has anything to do with the corectness of the textbook method of accelerated IRFs (we already know that you don't even know where to start calculating on this one, by your own admission)

Where does this " I am not sure that the books get this problem right" leave your theories? Moroder 07:28, 11 December 2006 (UTC)


 * Moroder - Kindly can this. "Green" really does not "get it" with relativity.  Let's see if what I wrote just now in the new thread settles this issue.  If it dies not, then it is better if we just stop responding to "green".  This is not USENET.  We are here to edit, not to educate.  (It is reasonable to answer a thoughtful question, but not to discuss an obscure and non-notable issue ad-infinitum as we are doing here.) --EMS | Talk 03:35, 11 December 2006 (UTC)


 * You are right, I just noticed your post. I stop, there is no use educating trolls. Moroder 07:28, 11 December 2006 (UTC)


 * Imo, at best you're a highly educated jerk who still does not have the slightest inkling of the basic question I have brought to the table, not to mention how to resolve it. Essentially all points you have raised above are irrelevant. All I wanted to know is how, if the EP stands as an independent physical principle, why it does not effect the time dilation calculated using the principles and formulas of SR -- which does not expressly contain that principle -- in the sense of adding an additional time dilation effect? Or equivalently, on the basis of what logic and principles does the calculation you previously outlined, include the effects of the EP even though said principle is not one of the principles of SR? Or equivalently, from the principles of SR, can you derive the EP? I don't believe you have the depth to offer a clear and concise answer to these essentially equivalent questions, from a principled pov. If you did, presumably you would have already done so. In responses, you limited your meager offerings to irrelevant comments, calculational power games, and references to inapposite experiments and links. If you're really a physicist, I can't imagine that you're associated with any academic institution of any calibre, e.g., like my alma mater, Cornell University. EMS is no better -- in spirit a handwaving conformist, with you as his toady. green 12.30.216.138 10:49, 11 December 2006 (UTC)


 * EMS, I know more about relativity than you give me credit for, and I suggest you know somewhat less than you give yourself credit for. As for Moroder, I asked him to explain from first principles how the GR related gravitational time dilation can be included in the SR-only formulation. If he wasn't prone to game-playing, he would have given a concise answer. I think I can do what he refused to do, but there are a few subtle issues I am still contending with (as I am coming to the opinion that the SR-only calculation might not be an approximation). green 12.30.216.138 06:26, 11 December 2006 (UTC)

Disruption of this talk page from IP address 12.30.216.138
It has become increasingly difficult to attempt to have or to follow any sort of meaningful discussion on this page due to the ongoing antics of 12.30.216.138. If others agree with me on this point, perhaps we can take action, up to requesting administrative involvement, if needed, to end this disruption. If others disagree with me, that's perfectly okay as well. I won't cry over it. Tim Shuba 02:50, 10 December 2006 (UTC)


 * I agree, he continues the BS even after he was given a step by step proof, must be one of the trolls "I understand but ..." Moroder 04:52, 10 December 2006 (UTC)


 * I kindly ask (again!) that people (specifically Green and Morodor) abstain from discussing the Twin paradox itself on this page while this page is for discussing how to fairly describe the notable differing POV's about the Twin paradox as found in the scientific literature. Harald88 17:01, 10 December 2006 (UTC)


 * Name is Moroder, as in Giorgio. And "discussion" without math is simply worthless. Maybe you can help "green" with the little calculation I asked about. Hint: it is like a Pound-Rebka experiment where you run the elevator in both directions. What do you get? Moroder 17:14, 10 December 2006 (UTC)
 * And FYI (again), my user name is not harry but Harald88 or if you wish, Harald: as in king of Norway. Do you want to become "morry"? ;-)
 * Editors are easily drawn into long debates while the purpose of Wikipedia is to fairly describe the opinions (incl. debates and calculations) as found in the literature, and not to add our own original opinions and debates, see WP:TPG. Harald88 17:36, 10 December 2006 (UTC)


 * Well, "green" complained about the mainstream explanation in textbooks and class notes, so I decided to have him calculate the effect he claims that all these books are neglecting. Would you care to help him out? Moroder 17:44, 10 December 2006 (UTC)
 * I have not followed that discussion. In the past I have had lengthy discussions with someone that led nowhere due to mutal misunderstandings, and if he is that one, I will not volonteer. I would advice him to bring it up in a discussion group. Harald88 18:03, 10 December 2006 (UTC)


 * No idea what you are talking about, just an observation : when you ask a true physicist to start calculating, he/she does exactly that. Does not turn tail and run Moroder 18:11, 10 December 2006 (UTC)


 * I am talking about the fact that Wikipedia Talk pages are not meant for such discussions, we get all the time people who want to debate calculations and other stuff. Don't you understand [[WP:TPG]? And if green is the one I think he is, I have already had lengthy discussions with him about time dilation.
 * However, this Talk paqe is meant for discussions about the quality of the article and how to improve it. That includes discussions about lack of clarity. Apparently the article still (or again) is lacking clarity; but as the subject matter is confusing for many people incl. physicists, it may be hard or even impossible to make it understandable for everyone. Harald88 12:31, 11 December 2006 (UTC)

I couldn't follow the different conclusions, for one point is not clearly defined. Infinitesimal calculus is only possible, if infinitesimal small elements exist (lim dx->0). This is not the case for materialistic object, not for electromagnetic fields, .. Is it possible to change velocity in an infinitesimal step? If not, we have to agree if every possible finite change of velocity shows the same result as if this finite step was done with an infinite number of infinitely small steps. Only then we have reason to say, how much time it takes for both observers to make this step. The smallest difference can accumulate to any value during by adding infinitely. In short: is infinitesimal calculus applicable? ErNa 20:35, 10 December 2006 (UTC)


 * Frame jumps are definitely unphysical. No question on this point. However, if you want to use one, several, or an infinite set of jumps, you can surely do so and get some number. The question here is the meaning and reliability of the resultant number. If you believe in rigor, a subtle question arises as to the reliability of such a method. It seems somewhat squeaky to me because, e.g., when using calculus, at each stage in the limiting process the clock being modeled has numerous undefined values. What is the clock reading during a jump, and why does it read what it reads? Jumps or step functions are OK in pure mathematics because they are well-defined, but in physics we have no theory for the clock value during a jump. LOL!


 * Further, if you convince yourself that the jump method is acceptable, another question arises as to whether applying a formula used in SR, can adequately account for another, apparently independent effect; namely, the gravitational time dilation. Even if I could do an EP-based calculation (in effect, GR) and get the same result as the SR calculation using calculus, the question remains exactly how the SR calculation is able to account for the GR effects. One needs an argument based on first principles, but Moroder insists that a calculation is, ipso facto, sufficient. I hope this helps. green 12.30.216.138 00:55, 11 December 2006 (UTC)


 * At this point, I think that some action is needed to deal with both "green" and Harald88. Green started out making some productive edits, but now is introducing one concept that are blatantly anti-relativistic (namely the absolute rest frame), and is demanding that a GR viewpoint completely of his own invention be discussed in violation of WP:NOR.  I have little use for either.


 * You really ought to learn to read with perspicacity. I haven't made any edits of the type you allege, and I explained my concept of absolute frame and I don't see any willingness on your part to rationally critique it. In any event, I didn't include it in the article. So, in sum, please cease the BS'ing. green 12.30.216.138 03:01, 11 December 2006 (UTC)


 * One other thing; I stated a preference, along with Harald, to include a discussion of Einstein's GR solution, and perhaps others in the literature. I didn't demand that my critique of it be included in the article. You really ought to get your facts straight before making irresponsible comments. green 12.30.216.138 03:05, 11 December 2006 (UTC)


 * The issue is what you are putting here. I thank you for not disrupting the article itself, but you are messing things up here. On GR, we are not discussing Einstein's "GR" solution at all, but instead your misunderstanding of what would constitute a GR solution. If anything, your confusion illustrates the reason why I don't want GR mentioned in the article at all:  The issues involved are highly subtle and once you have succeeded in finally sorting them all out they bring you out at the same place anyway.  IMO, it is hard enough to deal with the twin paradox without bringing in a viewpoint such that one almost needs a Ph.D. to comprehend it. --EMS | Talk 03:46, 11 December 2006 (UTC)


 * EMS, It is a fact that the issues that are raised by the paradox go deep; but I think that you are too pessimistic in your thinking that it can't be explained in clear language. Harald88 12:31, 11 December 2006 (UTC)


 * The real issue, indeed the only issue imo, is your intolorance (notwithstanding denials) of any discussion that expresses views that might be wrong ... or perhaps partially right but deviating to some extent from the conventional wisdom. Wrt GR, I am not necessarily certain of the precise flaws in the solution allegedly advanced by Einstein, both as a matter of physics and wrt what his actual position was, since I am assuming that what I read in the earlier version of the GR section is historically correct. Some of my ideas are definitely correct -- e.g., the fact that the field does not propagate -- some probably not. Oddly, what I wrote was largely in agreement with your position albeit not fully. But it really doesn't matter since I expressly told you that I didn't want to edit the GR section since I am not expert enough. I disagree with your attitude about the GR section. It doesn't matter if some of the issues are subtle. It doesn't justify ignoring them and I am fairly certain that many readers would be interested in the history. green 12.30.216.138 04:43, 11 December 2006 (UTC)


 * Green - We will be doing the readers a real disservice if we deviate from conventional wisdom here, unless it is done to reflect a genuine disagreement in the field. I repeat:  I am not demanding anything more of you than I demand of myself with respect to original research.  I am being intolerant, and IMO for good reason.


 * I never suggested wrt to the article, that we should depart from what's in the literature. green 12.30.216.138 06:10, 11 December 2006 (UTC)


 * As this page is to discuss the contents of the article, it makes little sense to discuss positions that deviate strongly from the literature here either. --EMS | Talk 06:17, 11 December 2006 (UTC)


 * If you want to research and write up the history of the twin paradox, that would be very welcome. Some of it is in the discarded "Origins" section and I have no objection to the relevant material being restored. --EMS | Talk 05:50, 11 December 2006 (UTC)


 * I think Harald is better qualified, but I will be available for critical input. green 12.30.216.138 06:10, 11 December 2006 (UTC)


 * Harald88 is little better, as he seems to have little concept of what makes an article notable under WP:NPOV and WP:RS. This is the third run-in I have had with him on relativity-related issues, and this one is just as silly as the previous two.  He has been citing as sources articles from obscure overseas journals that are not cited elsewhere.  Now above he makes a claim that a viewpoint in the American Journal of Physics (which is a respectable journal) is being ignored, but fails to cite the relevant article.  Even here, I would need to see evidence that the field currently considers the viewpoint presented to be a valid point of contention.  (It is easy to use old publications as evidence of a disagreement when in fact the issue was settled long ago but still after the article was published.) --EMS | Talk 02:52, 11 December 2006 (UTC)


 * I agree that we had silly run-ins in the past, but no hard feelings! I didn't have the exact reference at hand; in a rewrite I'll surely add that reference as well. I'll also provide citation lists when I find the time at the office to do so. Please take into account that Wikipedia is not limited to your region: what is "overseas" for you is on this side for others - that's called regional bias. Moreover, I agreed with Pjacobi that we preferably not reference papers that have not been cited at all in the literature, and I found that so far the Unnikrishan paper has not been cited; moreover, I also pointed out that I welcome better references, and I suggested to include Baez and Janssen, it's just a matter of finding the most appropriate articles (did Baez publish the same in a journal?). Harald88 12:31, 11 December 2006 (UTC)