Preferred Frame Theory indistinguishable from SR
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From: harald on 6 Jul 2010 03:25 On Jul 5, 8:26 pm, Paul Stowe <theaether...(a)gmail.com> wrote: > On Jul 5, 10:00 am, harald <h...(a)swissonline.ch> wrote: > > > > > On Jul 5, 2:46 pm, stevendaryl3...(a)yahoo.com (Daryl McCullough) wrote: > > > > harald says... > > > > >Acceleration effects are not identified as gravitational fields in > > > >Newtonian physics (which, as you now know, you didn't know); and > > > >neither is that the case in SRT. In those theories acceleration is > > > >"absolute", and no gravitational fields are caused by acceleration. > > > > This is a topic for another discussion, but I'm talking about > > > "pseudo-gravitational" fields, which crop up in both SR and Newtonian > > > physics if you use accelerated coordinates. > > > We agree on "pseudo", while Einstein rejected that. > > > > >> I think it is because you have not made it very well. I still > > > >> have no idea what your point is. > > > > >Just study Einstein's paper carefully, > > > > I want to know what *YOUR* point is. State it in your own words. > > > I did, also in the part of my sentence that you exactly here snipped: > > > *you'll know what theory the paradox challenges*. > > > THAT (and only that) was my point: the clock paradox challenges the > > General PoR. > > > You certainly are aware that, despite Einstein's *suggestion* to that > > effect in the introduction of his 1905 paper, SRT is *not* based on > > the General PoR. > > Strictly speaking the 'domain' of the 'special' theory of relativity > is limited to inertial states. The original principle of relativity > as expressed in Einstein's 1905 work covered only that domain. So > Harald is correct, the paradox is confined to the situation where, you > have identical twins one remain in the original inertial frame, the > other accelerated rapidly (nearly instantaneously) to speed ~c travels > for x time wrt the original FOR, reverses comes to an equally rapid > stop (wrt the original FOR) then returns the same way. Since SRT is > based upon v^2 effects (second order quantities) the directionality of > any asymmetry is lost in the expressions that quantify changes. > However, there is NO! paradox, either in nature, or SRT, once one > understands that limitation. The traveling twin, not the stay at home > twin will be physically younger. On a one-way trip however, we can't > say which one would be for an equal physical duration. That would > depend upon the speeds of both FOR relative to the CMBR... > Directionality does matter. I don't follow your last sentence. Perhaps you mean, as Langevin put it, that a change of direction of speed does matter for the asymmetry. Regards, Harald
From: harald on 6 Jul 2010 03:42 On Jul 5, 8:26 pm, Paul Stowe <theaether...(a)gmail.com> wrote: > On Jul 5, 10:00 am, harald <h...(a)swissonline.ch> wrote: > > > > > On Jul 5, 2:46 pm, stevendaryl3...(a)yahoo.com (Daryl McCullough) wrote: > > > > harald says... > > > > >Acceleration effects are not identified as gravitational fields in > > > >Newtonian physics (which, as you now know, you didn't know); and > > > >neither is that the case in SRT. In those theories acceleration is > > > >"absolute", and no gravitational fields are caused by acceleration. > > > > This is a topic for another discussion, but I'm talking about > > > "pseudo-gravitational" fields, which crop up in both SR and Newtonian > > > physics if you use accelerated coordinates. > > > We agree on "pseudo", while Einstein rejected that. > > > > >> I think it is because you have not made it very well. I still > > > >> have no idea what your point is. > > > > >Just study Einstein's paper carefully, > > > > I want to know what *YOUR* point is. State it in your own words. > > > I did, also in the part of my sentence that you exactly here snipped: > > > *you'll know what theory the paradox challenges*. > > > THAT (and only that) was my point: the clock paradox challenges the > > General PoR. > > > You certainly are aware that, despite Einstein's *suggestion* to that > > effect in the introduction of his 1905 paper, SRT is *not* based on > > the General PoR. > > Strictly speaking the 'domain' of the 'special' theory of relativity > is limited to inertial states. The original principle of relativity > as expressed in Einstein's 1905 work covered only that domain. PS I overlooked the error you made here - a confusion that is often seen. As Eric points out, SRT is *not* (never was!) limited to inertial states. It's the same as for Newtonian mechanics. SRT uses Poincare's PoR, which refers to Newtonian reference systems; and we can switch reference system whenever we like, using the LT. Thus the twin problem is a trivial exercise in SRT. The twin paradox however was aiming Einstein's *General* PoR. Harald
From: Daryl McCullough on 6 Jul 2010 08:27 harald says... >PS I overlooked the error you made here - a confusion that is often >seen. As Eric points out, SRT is *not* (never was!) limited to >inertial states. It's the same as for Newtonian mechanics. SRT uses >Poincare's PoR, which refers to Newtonian reference systems; and we >can switch reference system whenever we like, using the LT. Thus the >twin problem is a trivial exercise in SRT. The twin paradox however >was aiming Einstein's *General* PoR. I still don't know why you say that. Are you interpreting the general principle of relativity to be "absolute acceleration is not detectable", while the limited principle of relativity is "absolute velocity is not detectable"? Depending on what you mean by "acceleration", the general principle may be true or false. If you mean *proper* acceleration, then of course that is detectable: Put a heavy mass on a spring. If the spring is uncompressed and unstretched, then there is no proper acceleration in the direction of the spring. Alternatively, you can set up a rectangular coordinate system with metersticks, and plot the trajectory of a light beam or a tossed ball: if the plotted path is curved, then the coordinate system is accelerating. If by "acceleration", you mean *coordinate* acceleration, then whether you are accelerating or not is relative to whatever coordinate system you are using. In any case, in what way do you think the twin paradox causes problems for the principle of relativity? I think you missed the point of Einstein's dialog that you referenced. I don't see it as an admission that the twin paradox is a consistency challenge for his theory. I take it as a tutorial about his principle of relativity, and the twin paradox is a thought experiment that is used to highlight distinctive features of it. -- Daryl McCullough Ithaca, NY
From: harald on 6 Jul 2010 10:22 On Jul 6, 2:27 pm, stevendaryl3...(a)yahoo.com (Daryl McCullough) wrote: > harald says... > > >PS I overlooked the error you made here - a confusion that is often > >seen. As Eric points out, SRT is *not* (never was!) limited to > >inertial states. It's the same as for Newtonian mechanics. SRT uses > >Poincare's PoR, which refers to Newtonian reference systems; and we > >can switch reference system whenever we like, using the LT. Thus the > >twin problem is a trivial exercise in SRT. The twin paradox however > >was aiming Einstein's *General* PoR. > > I still don't know why you say that. Are you interpreting the general > principle of relativity to be "absolute acceleration is not detectable", > while the limited principle of relativity is "absolute velocity is not > detectable"? > > Depending on what you mean by "acceleration", the general principle > may be true or false. If you mean *proper* acceleration, then of course > that is detectable: Put a heavy mass on a spring. If the spring is > uncompressed and unstretched, then there is no proper acceleration > in the direction of the spring. Alternatively, you can set up a > rectangular coordinate system with metersticks, and plot the trajectory > of a light beam or a tossed ball: if the plotted path is curved, then the > coordinate system is accelerating. > > If by "acceleration", you mean *coordinate* acceleration, then whether > you are accelerating or not is relative to whatever coordinate system > you are using. > > In any case, in what way do you think the twin paradox causes problems > for the principle of relativity? > > I think you missed the point of Einstein's dialog that you > referenced. I don't see it as an admission that the twin paradox is > a consistency challenge for his theory. I take it as a tutorial about > his principle of relativity, and the twin paradox is a thought experiment > that is used to highlight distinctive features of it. > > -- > Daryl McCullough > Ithaca, NY Daryl, the topic of the twin paradox is strongly related to the topic of this thread; to better understand this, a minimal amount of historical understanding is needed. The twin scenario was presented by Langevin in 1911 to show that physical acceleration is "absolute", even more so with SRT than with Newton's mechanics. He argued that these absolute effects detect the ether (what you call a "preferred frame"). However, Einstein (1916) considered that the PoR of SRT has an "epistemological defect", since it relates to a privileged group of "spaces" that cannot be observed. And what he could not observe, he called 'factitious'. In other words, he rediscovered Newtons' argument but he found it unacceptable. He preferred to go the opposite route and extended the PoR as follows: "The laws of physics must be of such a nature that they apply to systems of reference in any kind of motion". As a result, physical acceleration is, according to Einstein's GRT, *relative* - which is just the contrary of what Langevin argued based on his "twins" example of SRT. It should not be surprising that this was not only very confusing for bystanders (who already hardly understood the difference between the two theories), but that it even looked like a contradiction - which is BTW the definition of a "paradox": - http://dictionary.reference.com/browse/paradox We may say that that the clock paradox was unavoidable. As Einstein explains in 1918, it is an "Objection against the Theory of Relativity", in view of the fact that "according to this theory, coordinate systems in arbitrary states of motion are qualified". So far the question "what was the twin paradox". Einstein also comments in that same paper on the ether concept, and concludes: "There is no [...] privileged state of motion,[..] and that is why there is no Aether in the old sense." Harald
From: PD on 6 Jul 2010 11:07
On Jul 5, 12:12 am, colp <c...(a)solder.ath.cx> wrote: > On Jul 5, 7:27 am, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > > On Jul 3, 6:07 pm, colp <c...(a)solder.ath.cx> wrote: > > > > On Jul 4, 2:10 am, PD <thedraperfam...(a)gmail.com> wrote: > > > > > On Jul 3, 1:04 am, colp <c...(a)solder.ath.cx> wrote: > > > > > > On Jul 3, 2:57 am, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > > On Jul 1, 6:25 pm, colp <c...(a)solder.ath.cx> wrote: > > > > > > > > On Jul 2, 2:26 am, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > > > > On Jul 1, 12:53 am, colp <c...(a)solder.ath.cx> wrote: > > > > > > > > > > On Jul 1, 11:37 am, Koobee Wublee <koobee.wub...(a)gmail.com> wrote: > > > > > > > > > > > On Jun 30, 4:20 pm, artful wrote: > > > > > > > > > > > > On Jul 1, 8:47 am, colp wrote: > > > > > > > > > > > > The statement that "moving clocks run slow" isn't an > > > > > > > > > > > > oversimplification, it is directly inferred from Einstein's > > > > > > > > > > > > "Electrodynamics of Moving Bodies". > > > > > > > > > > > > It IS an over simplification. There is more to SR than just clocks > > > > > > > > > > > running slow. > > > > > > > > > > > Nonsense and mysticism. <shrug> > > > > > > > > > > A postulate is just an assumption with better table manners. > > > > > > > > > Yes, indeed. By DEFINITION, a postulate is something that is ASSUMED. > > > > > > > > > In science, the test of a postulate is based on experimental check of > > > > > > > > the *consequences* of postulates. A direct test of the postulate is > > > > > > > > not required. > > > > > > > > One such test is the test for paradoxes arising from one or more > > > > > > > postulates. For example, the following two postulates lead to a > > > > > > > paradox, meaning that not all the postulates are correct: > > > > > > > > 1. Statement 2 is true. > > > > > > > 2. Statement 1 is false. > > > > > > > > The paradox that arises from the postulates of Einstein's > > > > > > > "Electrodynamics of Moving Bodies" can be described as follows: > > > > > > > > "Examples of this sort, together with the unsuccessful attempts to > > > > > > > discover > > > > > > > any motion of the earth relatively to the light medium, suggest that > > > > > > > the > > > > > > > phenomena of electrodynamics as well as of mechanics possess no > > > > > > > properties > > > > > > > corresponding to the idea of absolute rest. They suggest rather that, > > > > > > > as has > > > > > > > already been shown to the first order of small quantities, the same > > > > > > > laws of > > > > > > > electrodynamics and optics will be valid for all frames of reference > > > > > > > for which the > > > > > > > equations of mechanics hold good.1 We will raise this conjecture (the > > > > > > > purport > > > > > > > of which will hereafter be called the Principle of Relativity) to > > > > > > > the status > > > > > > > of a postulate, and also introduce another postulate, which is only > > > > > > > apparently > > > > > > > irreconcilable with the former, namely, that light is always > > > > > > > propagated in empty > > > > > > > space with a definite velocity c which is independent of the state of > > > > > > > motion of the > > > > > > > emitting body." > > > > > > > > Einstien, Electrodynamics of Moving Bodies (Introduction) > > > > > > > > This text describes Einstein's postulate that there is no preferred > > > > > > > inertial frame of reference. > > > > > > > > "If at the points A and B of K there are stationary clocks which, > > > > > > > viewed in the stationary system, are synchronous; and if the clock at > > > > > > > A is moved with the velocity v along the line AB to B, then on its > > > > > > > arrival at B the two clocks no longer synchronize, but the clock moved > > > > > > > from A to B lags behind the other which has remained at B ..." > > > > > > > > Einstien, Electrodynamics of Moving Bodies (Section 4) > > > > > > > > The text describes the time dilation of a clock that moves from point > > > > > > > A to point B. If there is no preferred frame of reference then it is > > > > > > > just as true to say that > > > > > > > the clock is viewed as part of a stationary system and the points A > > > > > > > and B are in a moving system which moves at velocity -v. The > > > > > > > conclusion that time for both systems can be dilated with respect to > > > > > > > the other system is paradoxical. > > > > > > > No, it's not paradoxical at all. > > > > > > It is paradoxical because time for both systems cannot be dilated with > > > > > respect to each other. > > > > > This is your assumption about what can and cannot be. > > > > No, it is a logical inference derived from Einstein's description of > > > time dilation and his postulate that there is not preferred frame of > > > reference. > > > No, I'm sorry, but that is not a good inference. > > Why can't you identify what is wrong with it then? > > > I don't have any idea > > how you conclude from his postulate about no preferred frame that time > > for both systems cannot be dilated with respect to each other. > > That isn't what I am saying. I'm saying that for time for both systems > to be dilated with respect to each other constitutes a paradox, No, it does not. I suspect that you believe that it is because you believe the statement made by relativity is that "moving clocks run slow". You hear this to mean that "Clock A is running slower than clock B, and clock B is running slower than clock A." You furthermore believe that, logically, "Clock A is running slower than clock B" necessarily implies that "Clock B is running faster than clock A" and hence the paradox arises with the combination of sentences "Clock B is running faster than clock A" and "Clock B is running slower than clock A." The problem, you see, is that the comic-book statement you are using as your launching point belongs in COLP's Oversimplified Relativity. Relativity doesn't make that statement as carelessly and loosely as you're using it. Instead, it makes a more precise statement about what it MEANS to say that Clock B is running slower than Clock A. And here is where identification of particular *events* comes into play. And this makes all the difference. PD > and > this situation arises when the idea that no preferred frame of > reference exists is applied to the example. Since we know from > experiment that time dilation is real, the only remaining assumption > is that of the non-existence of a preferred frame of reference; i.e > that assumption is false because it results in a paradox.- Hide quoted text - > > - Show quoted text - |