Preferred Frame Theory indistinguishable from SR
in [Relativity]
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From: Edward Green on 8 Jul 2010 21:34 On Jul 8, 1:06 pm, stevendaryl3...(a)yahoo.com (Daryl McCullough) wrote: > Edward Green says... > > > > >On Jul 8, 6:28=A0am, stevendaryl3...(a)yahoo.com (Daryl McCullough) wrote: > > ><...> > > >> Physicists *DO* reject the generalized principle of relativity expressed > >> as the requirement of general covariance because it is physically vacuous > > >Aha. That's exactly what I was trying to express when you asked me to > >elaborate. Just how long have "physicists" felt this way, and when did > >they start reading my Usenet posts? :-) :-) :-) > > The position I'm quoting was in Misner, Thorne and Wheeler's "Gravitation", > which is at least 30 years old. Drat. I guess I'll have to give them priority. ;-) > >(I had an argument along these lines with John Baez years ago. > > I think it must have been subtly different, because John certainly > knows that every theory can be made generally covariant. There is > a related property that *isn't* vacuous, that I mentioned, which is > the lack of non-dynamic scalar, vector, or tensor fields. In GR, > all fields are dynamic. I haven't fully digested your insight here. Still, it doesn't sound like anything I remember John Baez saying. BTW -- do you claim priority for this insight, AFAYCT, or is that from MTW also? What I specifically remember John saying, was that in SR a certain class of coordinate systems were equivalent, whereas in GR _all_ coordinate systems are equivalent (I have the feeling of deja vue ... I think I just made that comment several posts ago). That seems to leave one open to the charge of vacuity. There is definitely something subtly different about the equivalence of coordinate systems under Lorentz transformation and the equivalence under general homeomorphisms ... now I know I'm repeating myself ... one predicts the equivalence of physical experiments in closed rooms, the other speaks of the prowess with tensorial calculus. Being able to handle rotating and non-rotating coordinate systems in the same mathematical framework does not mean you couldn't tell if you were in a rotating laboratory or not from purely internal measurements. Just for the sake of argument, let me suggest two things in GR which aren't dynamic... or hint at something that isn't dynamic, I should rather say: acceleration and rotation (well, OK, linear acceleration and rotation). With regards to the former, you may perhaps mention the equivalence principle, but I've recently finished a book which says that the equivalence principle is scaffolding, and not strictly true. I tend to agree, because if you can measure the local curvature of space, you can tell if you are in a gravitational field or an accelerating elevator, and I think this is true even assuming away tidal effects and curvature of the gravitational field itself. And nobody would claim that rotation is "relative" in GR. I've certainly long held a position which could be translated "general covariance is vacuous", if I were clever enough to use such big words. Even in Newtonian dynamics, we could, as you say, posit a field which measures the local velocity wrt the rest frame -- oh, wait... even in Newtonian dynamics, there is no detectable rest frame, is there? Well, say there was for the sake of argument... an aether frame. We could still readily make a theory dealing with this "generally covariant" by inserting the local velocity of the aether frame as a parameter. Physics still looks exactly the same to all observers, once they measure and put in the appropriate value of this parameter; the same way physics looks the same to all yachtsmen once they put in the water and wind direction. If they don't have the concept of such things, then they are all going to have different "theories" of how their yachts handle. In fact, I really can't imagine a kind of theory which would not allow this maneuver. Physics _always_ looks the same to all observers once they understand what factors tend to make things look different, and correct for them. This is on an entirely different page from the strict equivalence in closed laboratories demanded by SR (and Galilean invariance over its realm of accuracy, too). > Roughly speaking, the way to make an arbitrary theory generally > covariant is to stick in extra fields to correct for whatever > changes in the theory occur when you do a coordinate transformation. > But in general, those extra fields are non-dynamic. > > So I would like to know exactly what the argument was with John. <futilely snip the usual cross-posts>
From: colp on 8 Jul 2010 21:59 On Jul 9, 10:09 am, PD <thedraperfam...(a)gmail.com> wrote: > On Jul 7, 5:43 pm, colp <c...(a)solder.ath.cx> wrote: > > > > > On Jul 7, 8:52 am, PD <thedraperfam...(a)gmail.com> wrote: > > > > 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: > > > > > 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.. > > > I haven't discounted them. > > > > For example, he makes note of specific events, rather than just making > > > the general statement that "moving clocks" run slow. > > > The description of the specific events only serves to illustrate that > > it is the moving clock that runs slow compared to the stationary > > clock. > > Then you have misunderstood what he said. The EVENTS do more than > that. How, exactly? > > > > > > Furthermore, he > > > makes EXPLICIT mention of the statement that the clocks at points A > > > and B are initially synchronized IN THE K FRAME. > > > Assuming that they weren't synchonized in my general description of > > "the moving clock runs slow" would be arbitrary and illogical. > > They are synchronized in the K frame. They are not synchronized in the > K' frame. This is essential and cannot be dismissed. If they are not synchronized in the K' frame, then the K frame becomes the preferred frame of reference, which contradicts Einstein's first postulate. > > > Remember I was talking about _the_ clock, in reference to the moving > > clock described in "Electrodynamics of Moving Bodies", not to a clock > > in an arbitrary system. > > I understand that completely. There are two clocks involved here: One > that moves from A to B and one that remains at B. There is a frame K > in which points A and B are at rest, and there is a frame K' in which > points A and B are moving and the first clock above is at rest. Yes, I agree. > > > > > > 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. > > > No, it isn't a missing detail, it is an implication of Einstein's > > first postulate of relativity. > > WHAT is an implication of the first postulate? That they are also > synchronized in K'? No. The implication is that if there is no preferred frame of reference then predictions made in one inertial frame will be just as valid as predictions made in any other inertial frame, and if it is possible to synchronize clocks in one inertial frame them it is possible to synchronize clocks in any other inertial frame. > > > > > > > Here is Einstein's description of the clocks: > > > "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 ..." > > > Let us call the moving system K', in which the moving clocks at A' and > > B' are synchronized for an observer in K'. The stationary system K > > also has two clocks, but these two clocks are synchronized for an > > observer in K. Frames K and K' move at a constant velocity with > > respect to each other. > > > If there is no preferred frame of reference then there is no reason > > why the clocks at A' and B' cannot also be synchronized for an > > observer in K', just as the clocks at A and B are for an observer in > > K, due to the symmetry of the two frames and their respective clocks. > > Yes, that is true but the clock that is synchronized with B in K will > not initially show the same time as the clock that is synchronized > with B in K'. Are you saying that the clock at A in K (that is synchronized with the clock at B in K) will not initially show the same time as the clock at A' in K' (that is synchronized with the clock at B' in K'? > > Now YOU are the one that is adding things beyond what Einstein > actually said. What I am adding (two more clocks in K') does not change Einstein's postulates. Neither does making predictions from the point of view of an observer in each frame affect the postulates. > > There are only TWO clocks in Einstein's paragraph. One that moves from > A to B and one that remains at B. In the frame K, the clocks are > synchronized when the clocks are at A and B. Right. > In the frame K' that you > propose, those same two clocks are not synchronized when the clocks > are at A and B. I'm not talking about the same two clocks. I'm talking about two frames which are the same in all respects except for their relative motion (in order to establish symmetry). Thus in the K frame the clock at A' moves from A to B. When point A = point A', the clocks at these points are synchronized, just as Einstein's clock at A was synchronized with B before it moved towards B. Looking at the situation from the point of view of an observer in K', the clock at B moves from B' to A'.
From: Tom Roberts on 9 Jul 2010 00:57 Daryl McCullough wrote: > I think what he is complaining about is that people like me > are wedded to relativity theory, even though there has never > been a wedding ceremony. It's a common law marriage. Well, I am not "wedded" to relativity in any way. At present it is the best theory we have within its rather large domain, so SR and GR are the theories I use in their domains. And relativity is complex and interesting enough to sustain long-term interest and study. But I strongly suspect that relativity will be overthrown when we find a good theory of quantum gravity. Personally, I'm partial to "Doubly Special Relativity" or perhaps some variation of it.... Tom Roberts
From: Tom Roberts on 9 Jul 2010 01:04 Edward Green wrote: >> On Jul 7, 10:06 pm, Tom Roberts wrote: >>> Yes, I know you claim the CMBR dipole=0 frame is the >>> ether frame. But that is not LET. Lorentz obviously had >>> no knowledge of the CMBR, and could not possibly have >>> put it into his theory. Moreover, while there might be >>> some merit to your claim if relative to that frame the >>> CMBR was isotropic, it isn't. > > Really? That's very interesting. Would you care to elaborate? Wilson and Penzias discovered the CMBR in the 1960s; Lorentz died in 1928. The CMBR has a rich and varied multipole structure, as any good reference on it will show. There are maps of CMBR temperature in all directions, and they have LOTS of structure; ironically, they are invariably displayed in the dipole=0 frame (because otherwise the dipole would obscure the structure because the dipole is by far the largest multipole present). Selecting the frame in which its dipole moment is zero cannot cancel all the other multipoles, and thus it is not isotropic in that frame. Tom Roberts
From: Koobee Wublee on 9 Jul 2010 01:43
On Jul 8, 10:04 pm, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: > Wilson and Penzias discovered the CMBR in the 1960s; Lorentz died in 1928. That is indeed history. <shrug> > The CMBR has a rich and varied multipole structure, as any good reference on it > will show. There are maps of CMBR temperature in all directions, and they have > LOTS of structure; Playing down the insignificance of the dipole of CMBR due to it leading to non-politically conclusions. <shrug> > ironically, they are invariably displayed in the dipole=0 > frame (because otherwise the dipole would obscure the structure because the > dipole is by far the largest multipole present). But still cannot ignore this experimental result. <shrug> > Selecting the frame in which > its dipole moment is zero cannot cancel all the other multipoles, and thus it is > not isotropic in that frame. In another words, the Doppler shift in CMBR is indeed very significant. It hints at unveiling the absolute frame of reference as predicted by the MMX. <shrug> The team that discovered this Doppler dipole in CMBR should be awarded with the Nobel Prize. <shrug> |