Notion of Absolute Clock Synchronization in SR
in [Relativity]
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From: Sue... on 11 Apr 2010 04:09 On Apr 10, 10:24 pm, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: > GSS wrote: > > On Apr 9, 1:24 am, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: > >> GSS wrote: > >>> [...] > >> Bottom line: while one can take two clocks at rest on earth's geoid and > >> synchronize them in an inertial frame (e.g. the ECI), one CANNOT treat them as > >> if they were at rest in that inertial frame. Because they aren't. > > > Agreed. That is fair enough. > > >> The method used by the GPS to synchronize clocks in the ECI works in a way that > >> relies on each clock moving at a constant speed wrt the frame, and at a constant > >> gravitational potential. For a set of clocks at rest on the geoid, those > >> conditions hold for the ECI frame. They do NOT hold for the BCRF frame, which is > >> why it is not possible to synchronize them in that frame. > > > That is if we 'set' or 'adjust' or 'synchronize' each of the two > > clocks to the 'coordinate' time of that frame (BCRF) then the two > > clocks will no longer remain mutually synchronized. > > Yes. Such clocks on the geoid will not be mutually synchronized IN ANY INERTIAL > FRAME. You keep forgetting that "synchronized" must INHERENTLY be qualified with > an inertial frame -- that is part of the definition. > > > After all, when the two clocks A and B under consideration, are > > mutually synchronized to UTC time through GPS, these clocks are > > actually, physically located in (a) their local or lab frame, (b) ECI > > frame, (c) BCRF frame and the (d) Galactic reference frame. That is > > these clocks are simultaneously located in ALL of these frames ALL the > > time. > > Hmmm. "physically located in frame X" really makes no sense -- frames are merely > a way of describing locations (via coordinates). Objects are "physically > located" in the WORLD, not any particular frame; but the coordinates of any > frame can be used to describe the location of a given object (relative to that > frame, of course). This is sort of what you said, but the implications are quite > different. > > Frames are a "point of view", and not any "physical" entity at all. They are, at > base, an artifact of human minds, as are the coordinates of any frame. Nature > herself uses no frames or coordinates; nature herself synchronizes no clocks -- > these are all HUMAN ARTIFACTS. > > We often use a physical object, such as a lab, to define a > frame. It is the physical object that is physical, not the > frame. > > > Only when you have to force the application of the second > > postulate of SR in different inertial frames, perforce you have to > > bring in the notion of coordinate time and hence need to 'adjust' the > > clocks accordingly in each frame. > ============= > > Not true. As I said before, the clocks are synchronized in ONE AND ONLY ONE > inertial frame because THAT IS HOW THE WORLD WE INHABIT WORKS [#]. This has > nothing directly to do with the second postulate of SR. But, of course, that > postulate was formulated because it, too, reflects how the world we inhabit > works [%]. > Tom, That is how the world constructed by Einstein and Minkowski works. http://en.wikipedia.org/wiki/Einstein_synchronisation Even putting it bold capital letters is unlikely to get nature's attention. Before wasting your money on a flashing billboard to bend nature to your will it might be helpful if you review the e-sync procedure to access how its assumptions differ from our current understanding of light propagation. The relativity principle http://farside.ph.utexas.edu/teaching/em/lectures/node108.html Actual measurements [*] ... http://en.wikipedia.org/wiki/De_Sitter_double_star_experiment ....do not support the light propagation model that the synchronisation method assumes. <<Once clocks are synchronized one can measure the one-way light speed.>> http://en.wikipedia.org/wiki/Einstein_synchronisation How much mass does a photon have to couple to the inertial field in the year 2010 ? Sue... http://en.wikipedia.org/wiki/Emission_theory > I cannot help it if you do not understand this and refuse to accept it. You need > to STUDY basic physics and LEARN what is known about the world we inhabit.. > > [#] Actual measurements show this. > > [%] Actual measurements show this. But their accuracy is not > perfect, and better data could force revisions in the theory. > > The difference in these two footnotes is that [#] is a > statement about measurements, while [%] is a statement about > a theory (i.e. a synthesis from imperfect measurements). > > > Let us suppose you have set the offsets of two precision clocks A and > > B so as to mutually synchronize them in some inertial reference frame > > say ECI. We can arrange to let their output in the form of 1PPS > > recorded in the associated computers. This 1PPS data from both clocks > > can be recorded for a 24 hour period for its detailed analysis later > > on. This recorded data is a physical record which CANNOT CHANGE > > whether we consider the clocks to be physically located in their lab > > frame, or ECI frame or BCRF or even the Galactic reference frame. > > Sure. Except as I said before, we cannot "consider" them to be "physically > located" in any frame, they are physically located in the WORLD. > > But the issue is about SYNCHRONIZATION, not any sort of historical record like > this. That requires some method of comparison other than merely looking at a > "record" of each clock's ticks. You'll necessarily find that whether they are > "synchronized" or not depends INHERENTLY on the method of comparison. And for > any approach you choose, you will necessarily have to select an inertial frame > in which to perform it. > > If you don't perform the comparison in an inertial frame, nobody > would call the result "synchronization". This is at base why > qualification with an inertial frame is required. > > > Don't you agree that the digital recording of the clock outputs is a > > physical phenomenon which is not influenced by the fact that the two > > clocks are actually, physically located in ALL of the above mentioned > > frames ALL the time. > > No. The record is a record, not any sort of "physical phenomenon". As I said > before, we cannot "consider" them to be "physically located" in any frame, they > are physically located in the WORLD; but yes, the record depends on the > computers' relationships to the clocks, not any frame. > > Bottom line: that "record" is a HUMAN ARTIFACT of what was recorded. Nature > herself uses no such artifacts, and the phrase "physical phenomenon" refers to > Nature, not human artifacts. > > [This is getting overly repetitive. Don't expect me to continue until and unless > you LEARN something, and recognize the inherently HUMAN nature of clock > synchronization. Ask yourself: who is it that pushes the reset buttons on the > clocks at specified times, in order to synchronize them? Who is it that > determines WHEN to do so (for each)? How is that "when" determined (for each)? > -- the answer to each involves humans and their rather arbitrary choices; nature > does not care about any of this, and does whatever she does without regard to > such human foibles.] > > Tom Roberts
From: GSS on 11 Apr 2010 10:50 On Apr 11, 7:24 am, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: > GSS wrote: >> On Apr 9, 1:24 am, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: >>> GSS wrote: >>>> [...] >>> Bottom line: while one can take two clocks at rest on earth's geoid and >>> synchronize them in an inertial frame (e.g. the ECI), one CANNOT treat them as >>> if they were at rest in that inertial frame. Because they aren't. > >> Agreed. That is fair enough. > >>> The method used by the GPS to synchronize clocks in the ECI works in a way that >>> relies on each clock moving at a constant speed wrt the frame, and at a constant >>> gravitational potential. For a set of clocks at rest on the geoid, those >>> conditions hold for the ECI frame. They do NOT hold for the BCRF frame, which is >>> why it is not possible to synchronize them in that frame. > >> That is if we 'set' or 'adjust' or 'synchronize' each of the two >> clocks to the 'coordinate' time of that frame (BCRF) then the two >> clocks will no longer remain mutually synchronized. > > Yes. Such clocks on the geoid will not be mutually synchronized IN ANY INERTIAL > FRAME. You keep forgetting that "synchronized" must INHERENTLY be qualified with > an inertial frame -- that is part of the definition. > >> After all, when the two clocks A and B under consideration, are >> mutually synchronized to UTC time through GPS, these clocks are >> actually, physically located in (a) their local or lab frame, (b) ECI >> frame, (c) BCRF frame and the (d) Galactic reference frame. That is >> these clocks are simultaneously located in ALL of these frames ALL the >> time. > > Hmmm. "physically located in frame X" really makes no sense -- frames are merely > a way of describing locations (via coordinates). Objects are "physically > located" in the WORLD, not any particular frame; but the coordinates of any > frame can be used to describe the location of a given object (relative to that > frame, of course). This is sort of what you said, but the implications are quite > different. > > Frames are a "point of view", and not any "physical" entity at all. They are, at > base, an artifact of human minds, as are the coordinates of any frame. Nature > herself uses no frames or coordinates; nature herself synchronizes no clocks -- > these are all HUMAN ARTIFACTS. > > We often use a physical object, such as a lab, to define a > frame. It is the physical object that is physical, not the > frame. > >> Only when you have to force the application of the second >> postulate of SR in different inertial frames, perforce you have to >> bring in the notion of coordinate time and hence need to 'adjust' the >> clocks accordingly in each frame. > > Not true. As I said before, the clocks are synchronized in ONE AND ONLY ONE > inertial frame because THAT IS HOW THE WORLD WE INHABIT WORKS [#]. This has > nothing directly to do with the second postulate of SR. But, of course, that > postulate was formulated because it, too, reflects how the world we inhabit > works [%]. > > I cannot help it if you do not understand this and refuse to accept it.... OK, let me ask you a final question under this thread. Assume two identical precision atomic clocks located on earth's geoid and separated by distance S (about 30 km.). Kindly give your most considered opinion regarding the best possible method to mutually synchronize them in a reference frame which you consider as most appropriate for the purpose. Will such synchronization hold good at least for a period of one day. Kindly suggest a practical method to check or verify the above synchronization between the two clocks. GSS
From: Da Do Ron Ron on 13 Apr 2010 10:11 [~RA~ wrote:] >> By what process were they [clocks] synch'd [in the given frame]? [Inertial wrote:] >> When they show equal times as equal. A number of ways to do this. >> Send fixed speed signals between them, or sync them when at the >> same location and then move them apart. Your Way#1 is bogus because the clocks may move relative to the fixed speed signals, thereby screwing up the synchronization. Your Way#2 is also bogus because clocks moving in different directions may run at different rates. (You would have to prove otherwise.) [~RA~ wrote:] > Why are they not in synch per other frames? [Inertial wrote:] >> Because that is how reality works. We have to model reality .. not >> bend it to our wills. Methinks you miscontrued the question; can you please tell us why the other frames see the clocks as asynchronous? ~RA~
From: GSS on 22 Apr 2010 12:58 On Apr 11, 7:24 am, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: > GSS wrote: >> On Apr 9, 1:24 am, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: >>> GSS wrote: >>>> [...] >>> Bottom line: while one can take two clocks at rest on earth's geoid and >>> synchronize them in an inertial frame (e.g. the ECI), one CANNOT treat them as >>> if they were at rest in that inertial frame. Because they aren't. > >> Agreed. That is fair enough. >> >>> The method used by the GPS to synchronize clocks in the ECI works in a way that >>> relies on each clock moving at a constant speed wrt the frame, and at a constant >>> gravitational potential. For a set of clocks at rest on the geoid, those >>> conditions hold for the ECI frame. They do NOT hold for the BCRF frame, which is >>> why it is not possible to synchronize them in that frame. > >> That is if we 'set' or 'adjust' or 'synchronize' each of the two >> clocks to the 'coordinate' time of that frame (BCRF) then the two >> clocks will no longer remain mutually synchronized. > > Yes. Such clocks on the geoid will not be mutually synchronized IN ANY INERTIAL > FRAME. You keep forgetting that "synchronized" must INHERENTLY be qualified with > an inertial frame -- that is part of the definition. > Do you mean to say that a pair of atomic clocks on the geoid can never be mutually synchronized because they are not at rest in any INERTIAL frame? >> After all, when the two clocks A and B under consideration, are >> mutually synchronized to UTC time through GPS, these clocks are >> actually, physically located in (a) their local or lab frame, (b) ECI >> frame, (c) BCRF frame and the (d) Galactic reference frame. That is >> these clocks are simultaneously located in ALL of these frames ALL the >> time. > > Hmmm. "physically located in frame X" really makes no sense -- frames are merely > a way of describing locations (via coordinates). Objects are "physically > located" in the WORLD, not any particular frame; but the coordinates of any > frame can be used to describe the location of a given object (relative to that > frame, of course). This is sort of what you said, but the implications are quite > different. > > Frames are a "point of view", and not any "physical" entity at all. If frames are a "point of view", at least the atomic clocks are physical entities. How can the digital readings of an atomic clock change with the change in the "point of view" or the reference frame? For example the digital reading of a temperature gauge does not change with a change in "point of view" or the reference frame. > They are, at > base, an artifact of human minds, as are the coordinates of any frame. Nature > herself uses no frames or coordinates; nature herself synchronizes no clocks -- > these are all HUMAN ARTIFACTS. > Agreed that objects are "physically located" in the WORLD, not any particular frame and Nature herself uses no frames or coordinates. Then how come Nature ensures the speed of light c to be an isotropic constant in all inertial reference frames in relative uniform motion, even if IT had to physically adjust the clock times and length scales of all such reference frames. You know that without adjusting the clock times in different inertial reference frames in relative uniform motion, the speed of light propagation c cannot be ensured to remain isotropic constant in all such frames. >> Only when you have to force the application of the second >> postulate of SR in different inertial frames, perforce you have to >> bring in the notion of coordinate time and hence need to 'adjust' the >> clocks accordingly in each frame. > > Not true. As I said before, the clocks are synchronized in ONE AND ONLY ONE > inertial frame because THAT IS HOW THE WORLD WE INHABIT WORKS No, that is how you have distorted the world view by accepting the second postulate of SR as a Gospel truth. Can you name a single physical phenomenon which cannot be explained/understood without invoking the second postulate of SR. GSS
From: Androcles on 11 May 2010 16:47
<valls(a)icmf.inf.cu> wrote in message news:44448961-61b6-4f02-8424-a16374f4d311(a)k19g2000yqm.googlegroups.com... Time as a coordinate is introduced by 1907 Minkovski, having then this concept no relation at all with 1905 Einstein. This is the reason why I am always repeating that 1905 Relativity is not equal to 1916 Special Relativity. =============================================== It is "1905 Special Relativity is not equal to 1916 General Relativity" |