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LE MONDE SCHIZOPHRÈNE D'EINSTEINIANA
http://www.rehseis.univ-paris-didero...JUMEAUX_A4.pdf
LE PARADOXE DES JUMEAUX Jeudi 16 juin et vendredi 17 juin, 9h-13h Université Paris Diderot, salle Klimt, 366 A "Revenu à la Terre ayant vieilli de deux ans, il sortira de son arche et trouvera notre globe vieilli de deux cents ans" ALLER 16 juin 9h Accueil des participants 9h15 Elie DURING et Alexis de SAINT-OURS Introduction : Histoire d'une fable relativiste 9h30 Jean-Marc LÉVY-LEBLOND (Université de Nice) Peut-on déparadoxifier les jumeaux ? 10h30 Alexis de SAINT-OURS (Université Paris-Diderot / REHSEIS) Accélération et asymétrie 11h30 Thierry GRANDOU (Université de Nice / CNRS) Sur l'origine du paradoxe de Langevin 12h30 Discussion générale RETOUR 17 juin 9h Point d'étape 9h30 Jean-Pierre LUMINET (Observatoire de Paris / CNRS) Si ce n'est toi c'est donc ton frère 10h30 Philippe LOMBARD (Irem de Lorraine / Archives Poincaré) Paradoxe des jumeaux et relativité générale 11h30 Elie DURING (Université Paris Ouest-Nanterre) En quel sens les jumeaux sont-ils "contemporains" ? 12h30 Discussion générale Les conclusions du séminai http://luth2.obspm.fr/~luminet/jumeaux_VF.pdf Si ce n'est toi c'est donc ton frère ? Jean-Pierre Luminet "La vitesse de la lumière dans le vide est la même pour tous les observateurs, quel que soit leur état de mouvement - il s'agit d'un fait observé dont Einstein est parti pour construire sa théorie. (...) L'observateur « en mouvement » se considère, lui, au repos, et voit l'autre système se mouvoir par rapport à lui. Il voit donc les horloges de l'autre système ralentir (donc le temps s'allonger) et ses distances rétrécir. Jusqu'ici, il n'y a pas paradoxe, même s'il paraît curieux que chacun puisse voir l'autre plus « jeune » et plus petit qu'il ne se voit lui-même. (...) Prenons maintenant deux horloges qui sont synchronisées dans le même système de référence. Que se passe-t- il si l'une des deux part à bord d'un vaisseau spatial et revient au terme d'un long voyage ? Einstein montre, dans son article de 1905, qu'à son retour l'horloge voyageuse retarde sur l'horloge au repos. Autrement dit la symétrie est brisée, les deux points de vue ne sont pas équivalents. (...) Prenons deux jumeaux dont l'un part vers une planète lointaine à une vitesse proche de celle de la lumière. A son retour, le voyageur lit sur sa montre qu'il est parti six ans, alors que son frère resté sur terre a vieilli de quarante ans. (...) Y a-t- il pour autant violation du principe de relativité ? Non..." Mais ce sont les vieilles élucubrations de la "fable relativiste", Jean-Pierre Luminet. Rien de nouveau? On n'a pas discuté de l'article de Peter Hayes? http://homepage.ntlworld.com/academ/...elativity.html What is wrong with relativity? G. BURNISTON BROWN Bulletin of the Institute of Physics and Physical Society, Vol. 18 (March, 1967) pp.7177 "A more intriguing instance of this so-called 'time dilation' is the well-known 'twin paradox', where one of two twins goes for a journey and returns to find himself younger than his brother who remained behind. This case allows more scope for muddled thinking because acceleration can be brought into the discussion. Einstein maintained the greater youthfulness of the travelling twin, and admitted that it contradicts the principle of relativity, saying that acceleration must be the cause (Einstein 1918). In this he has been followed by relativists in a long controversy in many journals, much of which ably sustains the character of earlier speculations which Born describes as "monstrous" (Born 1956). Surely there are three conclusive reasons why acceleration can have nothing to do with the time dilation calculated: (i) By taking a sufficiently long journey the effects of acceleration at the start, turn-round and end could be made negligible compared with the uniform velocity time dilation which is proportional to the duration of the journey. (ii) If there is no uniform time dilation, and the effect, if any, is due to acceleration, then the use of a formula depending only on the steady velocity and its duration cannot be justified. (iii) There is, in principle, no need for acceleration. Twin A can get his velocity V before synchronizing his clock with that of twin B as he passes. He need not turn round: he could be passed by C who has a velocity V in the opposite direction, and who adjusts his clock to that of A as he passes. When C later passes B they can compare clock readings. As far as the theoretical experiment is concerned, C's clock can be considered to be A's clock returning without acceleration since, by hypothesis, all the clocks have the same rate when at rest together and change with motion in the same way independently of direction. [fn. I am indebted to Lord Halsbury for pointing this out to me.] (...) The three examples which have been dealt with above show clearly that the difficulties are not paradoxes) but genuine contradictions which follow inevitably from the principle of relativity and the physical interpretations of the Lorentz transformations. The special theory of relativity is therefore untenable as a physical theory." http://www.informaworld.com/smpp/con...ent=a909857880 Peter Hayes "The Ideology of Relativity: The Case of the Clock Paradox" : Social Epistemology, Volume 23, Issue 1 January 2009, pages 57-78 "This first appearance of what has become known as time dilation in Einstein's work requires careful attention. In particular, anyone who assumes that the special theory deals only with uniform movement in a straight line and is thus a precisely delineated subset of the later general theory, will wish to explore why Einstein extends his conclusions to polygonal and circular movements. It is by no means "at once apparent" that what is true for a straight line is true for a polygon, nor that what has been "proved" for a polygon applies to a circle. The principle of relativity introduced at the outset of the 1905 paper implicitly limited the special theory to reference frames moving at a constant speed in a straight line with respect to one another. In later work, Einstein explicitly stated that the special theory applied only to a reference frame "in a state of uniform rectilinear and non rotary motion" in respect of a second reference frame, in contrast to the general theory that dealt with reference frames regardless of their state of motion (Einstein 1920, 61). Acceleration, therefore, would appear to be the province of the general theory. A polygon, however, would seem to necessarily involve acceleration whenever there is a abrupt alteration in the direction of travel. Even more confusingly, a circular path, far from allowing movement at a "constant velocity", has a velocity that continually changes. Einstein, it is argued, wished to minimise the significance of acceleration - as he did not mention acceleration at all in the passage, he could hardly be said to do otherwise (Essen 1971, 13). With respect to the transition from the straight line to the polygon, this assumption is corroborated by comments Einstein made in 1911 when he said that the larger the polygon the less significant the impact of a sudden change of direction would be. Einstein 1911: "The [travelling] clock runs slower if it is in uniform motion, but if it undergoes a change of direction as a result of a jolt, then the theory of relativity does not tell us what happens. The sudden change of direction might produce a sudden change in the position of the hands of the clock. However, the longer the clock is moving rectilinearly and uniformly with a given speed in a forward motion, i.e., the larger the dimensions of the polygon, the smaller must be the effect of such a hypothetical sudden change." (Einstein et al. 1993, 354) (...) The argument that the prediction of time difference between a moving and a stationary clock violates the principle of relativity is well known. Certainly, it must have become known to Einstein, for in 1918 he created a dialogue in which "Kritikus" voiced exactly this objection (Einstein 1918). In response to this criticism, Einstein underwent a volte-face, reversing his reasoning in 1905 and 1911. The sudden change in direction of the moving clock, far from having unknown effects that needed to be minimised, was now said to provide the entire explanation for the change. Instead of imagining a moving clock travelling in a huge polygon or circle to make sudden changes in direction as insignificant as possible or the journey as smooth as possible, Einstein imagined an out and back journey. He then explained that the slow-down in the moving clock occurred during the sudden jolt when it went into reverse. (...) Given Einsteins argument in 1918, it seems inescapable that his 1905 prediction of time dilation was not, in fact, a "peculiar consequence" of his forgoing account of special relativity (Einstein 1923, 49). When it is also remembered that in 1904 Lorentz deduced the existence of "local time", it is reasonable to conclude that the prediction that the clocks would end up showing different times can be reached without entering into Einstein's reasoning on the special theory at all. The supporters of Einstein, however, generally maintain that one needs to move beyond the special theory to the general theory to understand why the times shown by the clocks would be different. However, as Einstein's prediction preceded the general theory, this argument is problematic (Lovejoy 1931, 159; Essen 1971, 14). It has been seen that: (a) in 1911 Einstein explicitly rules out the ability of the special theory of relativity to say what happened if the moving clock suddenly changed direction, and (b) in 1918 Einstein tacitly admitted that his explanation of the clock paradox in 1905 was incorrect by transforming the polygonal or circular journey of the moving clock into an out and back journey. If the general theory is necessary to explain the clock paradox, then Einstein must have (a) predicted the effects of acceleration in 1905 even though he did not incorporate them into his theory for another decade, and (b) hidden his intuition by describing a journey that discounted their significance. (...) There is, nonetheless, some divergence about how to resolve the clock paradox amongst mainstream scientists and philosophers who address the issue. The majority suggest that (a) the general theory is required to resolve the paradox because like "Kritikus" they have deduced - quite correctly - that it cannot be explained by the special theory. However, a minority believe that (b) the paradox can be explained by the special theory because they have deduced - again quite correctly - that it is incredible to suppose that only the general theory can explain a prediction ostensibly arising from the prior special theory. Each deduction, considered in isolation, is allowable within the mainstream; what is not permitted is to bring the two of them together to conclude that ( c) neither the special nor the general theory explains time dilation. (...) The prediction that clocks will move at different rates is particularly well known, and the problem of explaining how this can be so without violating the principle of relativity is particularly obvious. The clock paradox, however, is only one of a number of simple objections that have been raised to different aspects of Einstein's theory of relativity. (Much of this criticism is quite apart from and often predates the apparent contradiction between relativity theory and quantum mechanics.) It is rare to find any attempt at a detailed rebuttal of these criticisms by professional physicists. However, physicists do sometimes give a general response to criticisms that relativity theory is syncretic by asserting that Einstein is logically consistent, but that to explain why is so difficult that critics lack the capacity to understand the argument. In this way, the handy claim that there are unspecified, highly complex resolutions of simple apparent inconsistencies in the theory can be linked to the charge that antirelativists have only a shallow understanding of the matter, probably gleaned from misleading popular accounts of the theory. The claim that the theory of relativity is logically consistent for reasons that are too complex for non- professionals to grasp is not only convenient, but is rhetorically unassailable - as whenever a critic disproves one argument, the professional physicist can allude to another more abstruse one. Einstein's transformation of the clock paradox from a purported expression of the special theory to a purported expression of the much more complicated general theory is one example of such a defence. A more recent example is found in Alan Sokal and Jean Bricmont's scornful account of Henri Bergson's attempt to investigate the clock/ twin paradox. Like "Kritikus", Bergson argued that the asymmetric outcome of the paradox was incompatible with the principle of relativity. Like Einstein, Sokal and Bricmont explain that Bergson has failed to recognise the asymmetric forces of acceleration at work. They go on to claim that the special theory tells us what happens under these circumstances and that the general theory only laboriously leads to the same conclusion. The suggestion that to vindicate this claim would be laborious functions in the same way as Einstein's elusive "calculations"; that is, it is not an explanation but an explanation-stopper. Sokal and Bricmont do not demonstrate how either the special theory or the general theory explain time dilation. Nor do they explain how their claim can be reconciled with Einstein explicitly limiting the special theory to objects travelling at a uniform velocity, nor account for why the circular journey of 1905 became the out and back journey of 1918. (...) Einstein's theory of relativity fails to reconcile the contradictory principles on which it is based. Rather than combining incompatible assumptions into an integrated whole, the theory allows the adept to step between incompatible assumptions in a way that hides these inconsistencies. The clock paradox is symptomatic of Einstein's failure, and its purported resolution is illustrative of the techniques that can be used to mask this failure. To uncover to the logical contradictions in the theory of relativity presents no very difficult task. However, the theory is impervious to such attacks as it is shielded by a professional constituency of supporters whose interests and authority are bound up in maintaining its inflated claims. Relativity theory, in short, is an ideology." Pentcho Valev |
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