Preferred Frame Theory indistinguishable from SR
in [Relativity]
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From: kenseto on 6 Jul 2010 08:26 On Jul 6, 12:34 am, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: > Edward Green wrote: > > Is the assumption of a hidden rest frame somehow inconsistent with > > relativistic dynamics? > > In modern physics the essence of SR is summarized thus: all theories of physics > must be locally Lorentz invariant. The problem with this staement is that it ignores the fact that each locality has its own standards for a unit of time and distance. In other words, locally Lorentz invariant cannot be applied globally. Ken Sedto > > Relativity itself has no dynamics, and it kinematic content is contained in the > above aphorism. The use of any special or unique inertial frame that is > referenced in the dynamic equations of a theory is inconsistent with local > Lorentz invariant. > > So, for instance, LET violates the above requirement, as does the theory derived > from the preferred-frame postulates Daryl gave. This is so even though both of > those theories are experimentally indistinguishable from SR, and both of them > have an unobservable preferred frame. > > Tom Roberts
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: Daryl McCullough on 6 Jul 2010 09:06 Edward Green says... > >Exploring backwards to the beginning of this thread, I find that on >Jun 25, 9:14=A0am, stevendaryl3...(a)yahoo.com (Daryl McCullough) wrote: > >> There is a variety of anti-relativity dissident that consists of >> people who accept length contraction and time dilation, but don't >> accept the relativity principle. They assume something along the >> lines of: >> >> There is a preferred frame, F, and there is an associated >> coordinate system such that >> >> 1. Light travels in straight lines at speed c, as measured in F's >> coordinate system. >> 2. An ideal clocks in motion relative to F has an elapsed time >> given by dT/dt = square-root(1-(v/c)^2), where t is the time >> coordinate of F's coordinate system, and v is the velocity of >> the clock, as measured in F's coordinate system, and T is the >> elapsed time on the clock. >> 3. An ideal meterstick in motion, with the stick aligned in the >> direction of its motion, will have a length given by >> L = square-root(1-(v/c)^2). > >I am that crank ;^} ! > >Actually, I'm not sure there is a preferred absolute frame, but I >think there may be something very much like one lurking about. > >You go on to assert that the acceptance of rules 1-3 is tantamount to >acceptance of SR. I do not deny it. So now where are we? What I said was that 1-3 were sufficient for deriving the SR results for the various thought experiments involving clocks, rulers, twins, light signals, pole-vaulters, etc. So if there is something inconsistent about SR, then 1-3 would have to be inconsistent. -- 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 - |