Preferred Frame Theory indistinguishable from SR
in [Relativity]
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From: Daryl McCullough on 6 Jul 2010 11:18 harald says... >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. What does that mean? As I said, proper acceleration (as measured by an accelerometer) is absolute, but coordinate acceleration is certainly not. >He argued that these absolute effects detect the ether (what you call >a "preferred frame"). If that's what he argued, then he was wrong. The fact that acceleration is measurable does not imply the existence of a preferred rest frame. Here's an analogy: A flat Euclidean plane has no notion of a preferred direction. Any direction is as good as any other. But it certainly has a notion of a *change* of direction. If you draw a path on the Euclidean plane, then you can unambiguously determine whether the line is straight or curved, because a straight line connecting two points is shorter than any curved line connecting the same two points. If you measure the lengths of two curves, you can determine which one is straight. A rest frame in Einstein's spacetime is analogous to a direction in Euclidean space. There is no preferred rest frame in spacetime any more than is a preferred direction in the Euclidean plane. But a *change* of rest frames is certainly detectable, in the same way that a change in direction is detectable in the Euclidean plane. >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. As I said, proper acceleration is definitely *not* relative, but coordinate acceleration trivially *is*. But proper acceleration is measuring acceleration relative to *freefall*. >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 I would like to hear any coherent explanation of why it looks like a contradiction. The bare statement "The laws of physics must be of such a nature that they apply to systems of reference in any kind of motion" is not a contradiction---on the contrary, it is nearly a tautology. You can always write the laws of physics so that you can use an arbitrary coordinate system. To derive a paradox from the twin thought experiment, you need to reason something like this: 1. There exists two coordinate systems, C1 and C2, such that the path of the traveling twin, as described in C1, is the same as the path of the stay-at-home twin, as described in C2. 2. Therefore, the predicted age of the traveling twin, computed using C1, must be the same as the predicted age of the stay-at-home twin, computed using C2. I don't see how 2 follows from the general principle of relativity, as expressed in the sentence "The laws of physics must be of such a nature, blah, blah, blah." From the latter, it follows that one can use either C1 or C2 to compute the ages of the two twins, but it *doesn't* imply that the ages will be the same. To be able to conclude that, you need to assume a very specific form for the laws of physics. -- Daryl McCullough Ithaca, NY
From: Edward Green on 6 Jul 2010 12:33 On Jul 6, 12:34 am, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: > In modern physics the essence of SR is summarized thus: all theories of physics > must be locally Lorentz invariant. I've said the same -- only I forget to use the qualification "local".
From: colp on 6 Jul 2010 16:03 On Jul 7, 3:07 am, PD <thedraperfam...(a)gmail.com> wrote: > > > 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. Yes it does. If a clock in a moving frame runs slow, then a clock in a stationary frame runs fast when viewed from the moving frame. If that were not the case then you would get paradoxical outcomes. > > I suspect that you believe that it is because you believe the > statement made by relativity is that "moving clocks run slow". Relativity makes a statement that means exactly the same thing. "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 > You > hear this to mean that "Clock A is running slower than clock B, and > clock B is running slower than clock A." No, B only runs slower than A if there is no preferred frame of reference. > 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." O.K. > The problem, you see, is that the comic-book statement you are using > as your launching point belongs in COLP's Oversimplified Relativity. It's not a comic book statement any more than Einstein's statement that a moving clock lags behind a stationary clock is a comic book statement. > > Relativity doesn't make that statement as carelessly and loosely as > you're using it. There is nothing careless or loose about my statement. > > 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. So why can't you say what the difference is if it exists? Some vague reference to "events" doesn't cut it.
From: colp on 6 Jul 2010 16:07 On Jul 6, 10:47 pm, harald <h...(a)swissonline.ch> wrote: > On Jul 6, 12:27 pm, colp <c...(a)solder.ath.cx> wrote: > > > > > On Jul 6, 10:07 am, Edward Green <spamspamsp...(a)netzero.com> wrote: > > > > Exploring backwards to the beginning of this thread, I find that on > > > Jun 25, 9:14 am, 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. > > > If you don't use a preferred frame then the Hafele-Keating experiment > > doesn't give the correct results. > > > > 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? > > > The first postulate of Einstein's first paper on SR says that there is > > no preferred frame. Unless that postulate is seriously revised your > > get bogus answers from SR. > > > > <reluctant snip> > > > > > Note: 1-3 only captures the aspects of relativity that involve > > > > length, time and motion. Those things are called "kinematics". > > > > That's not all of relativity, because it doesn't have > > > > any *dynamics*. It doesn't say anything about forces, or about > > > > how electromagnetism affects charged particles, or vice-verse. > > > > However, for most thought experiments exploring SR, 1-3 is > > > > completely adequate. > > > > Is the assumption of a hidden rest frame somehow inconsistent with > > > relativistic dynamics? > > > Why assume it when you can prove experimentally that it exists? > > What some people accept as conclusive proof, other people reason away. > For example, for Creationists the existence of dinosaur skeletons > isn't conclusive proof for the old age of the earth. And only one > century ago, Mach held that atoms don't really exist. Sure, standards of proof vary. If the Michelson Morely experiment had shown cycles which had a length of a sidereal day, would you consider that to be proof of a preferred frame of reference?
From: PD on 6 Jul 2010 16:52
On Jul 6, 3:03 pm, colp <c...(a)solder.ath.cx> wrote: > On Jul 7, 3:07 am, PD <thedraperfam...(a)gmail.com> wrote: > > > > > 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. > > Yes it does. If a clock in a moving frame runs slow, then a clock in a > stationary frame runs fast when viewed from the moving frame. If that > were not the case then you would get paradoxical outcomes. See below. It'd be a good idea to read my whole post before opening your yap. > > > > > I suspect that you believe that it is because you believe the > > statement made by relativity is that "moving clocks run slow". > > Relativity makes a statement that means exactly the same thing. No, it does not. See below. > > "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 > > > You > > hear this to mean that "Clock A is running slower than clock B, and > > clock B is running slower than clock A." > > No, B only runs slower than A if there is no preferred frame of > reference. > > > 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." > > O.K. And this is part of your problem. > > > The problem, you see, is that the comic-book statement you are using > > as your launching point belongs in COLP's Oversimplified Relativity. > > It's not a comic book statement any more than Einstein's statement > that a moving clock lags behind a stationary clock is a comic book > statement. Not so. Einstein's statement included things that you have discounted. For example, he makes note of specific events, rather than just making the general statement that "moving clocks" run slow. Furthermore, he makes EXPLICIT mention of the statement that the clocks at points A and B are initially synchronized IN THE K FRAME. A contradiction would arise by making the clock at B the moving clock only if the clocks are claimed to be intially synchronized also in the K' frame -- but they are NOT, and this is the essential detail that you have missed. Yes, in the K' frame, the B clock runs slower than the A clock, but when A arrives at B, it is STILL behind the B clock because in the K' frame the clocks are not initially synchronized. There is no contradiction. The observation that when the clock from A arrives at B, the former is behind the latter is a completely consistent observation in both frames. > > > > > Relativity doesn't make that statement as carelessly and loosely as > > you're using it. > > There is nothing careless or loose about my statement. Yes, there is, and I've pointed it out to you repeatedly, and you are ignoring it, preferring to stick to your guns with COLPs Oversimplified Relativity. I agree that COLPs Oversimplified Relativity is contradictory and should be chucked. But relativity does not suffer from that problem. > > > > > 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. > > So why can't you say what the difference is if it exists? Some vague > reference to "events" doesn't cut it. And again, it would help if you would actually READ what relativity says in a book designed to TEACH relativity, rather than just sticking to COLPs Oversimplified Relativity and demanding that people have COR make sense to you. I've already told you what the statement about time dilation is in regard to events. If you've forgotten it, then please reread that. If you don't know what an "event" is to a physicist, then I suggest you look it up, and preferably someplace other than the Internut. PD |