Notion of Absolute Clock Synchronization in SR
in [Relativity]
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From: valls on 18 Mar 2010 10:50 On 16 mar, 14:01, Tom Roberts <tjrob...(a)sbcglobal.net> wrote: > va...(a)icmf.inf.cu wrote: > > In the ECI frame of GPS all the clocks remain synchronized, even if > > they have different velocities and gravitational potentials. > > This is not true of STANDARD clocks. The clocks in the GPS satellites have been > modified so this is approximately true. That can only be done for certain > highly-symmetric situations, such as clocks in circular orbits around a planet > in which other effects can be neglected. Indeed, in the GPS those other effects > are not neglected, but are corrected for. > > These modified clocks are not what we normally mean when we say "clock". > For me, "clock" in this group means an instrument showing the unique time for an inertial system, as defined by 1905 Einstein with all precision. If you have a different version, can you make it explicit? > > Then, > > taking into account that huge experimental evidence, I dont see any > > other alternative that to accept that absolute clock synchronization > > exists in SR with the following meaning. Once perfect and stationary > > clocks are e-synchronized in some inertial frame, they remain showing > > the same time lecture at any local instant in all the others inertial > > frames. > > This is simply not true. Synchronizing clocks in frame A, and looking at them > from frame B, they are not in synch if B is moving wrt A. > > The modified clocks of the GPS are synchronized only in the ECI frame. That, of > course, is sufficient for the GPS, but is completely and utterly inadequate to > claim "absolute clock synchronization". > We are now in agreement. See my talking with Harald in this thread. > Tom Roberts RVHG (Rafael Valls Hidalgo-Gato)
From: harald on 18 Mar 2010 11:49 On Mar 18, 3:04 pm, va...(a)icmf.inf.cu wrote: > On 17 mar, 10:34, harald <h...(a)swissonline.ch> wrote: > > > On Mar 17, 3:34 pm, va...(a)icmf.inf.cu wrote: > > > > On 16 mar, 17:20, harald <h...(a)swissonline.ch> wrote: > > > > > On Mar 16, 3:30 pm, va...(a)icmf.inf.cu wrote: > > > > > > On 15 mar, 05:53, harald <h...(a)swissonline.ch> wrote: [..] > > > > > > > E-sync means that the ELAPSED times of both clocks correspond, as well as > > > > > > > the readings at some time. E-sync'd clocks remain in synch.. > > > > > > > Thanks for the elaboration. But more precisely: e-synched "perfect", > > > > > > "stationary" clocks remain in sync (if at the same gravitational > > > > > > potential). Now, let's hope that the OP will understand this. :) > > > > > > (Hello Harald, nice to meet you again). > > > > > In the ECI frame of GPS all the clocks remain synchronized, even if > > > > > they have different velocities and gravitational potentials. Then, > > > > > taking into account that huge experimental evidence, I dont see any > > > > > other alternative that to accept that absolute clock synchronization > > > > > exists in SR with the following meaning. Once perfect and stationary > > > > > clocks are e-synchronized in some inertial frame, they remain showing > > > > > the same time lecture at any local instant in all the others inertial > > > > > frames. Of course, that equal time lecture does not correspond to > > > > > the local time in each of the others inertial frames, where according > > > > > to SR rules, the now moving clocks (all with the same velocity) are > > > > > running slower than the local perfect and stationary e-synchronised > > > > > ones. > > > > > > RVHG (Rafael Valls Hidalgo-Gato) [..] > > The topic of this thread is concerned with the fact that according to > > all inertial reference systems in which the inertial reference system > > with its synchronized clocks is moving, those clocks are out of sync > > with each other (see also below). > > > > I mentioned the ECI of GPS, taken for granted that the e- > > > synchronization method of all its clocks is well-known. Let us > > > remember that all the moving clocks show the unique ECI time, > > > corresponding to the same time that a similar clock at rest in the > > > relevant ECI point would show. If now we consider the ECI moving at a > > > constant velocity with respect to an (imaginary) inertial frame B, > > > Note: the ECI "frame" itself is already an imaginary frame... > > I dont understand why you consider the ECI an imaginary frame. The whole Earth is rotating relative to it; there isn't any material frame that is pretended to be "in rest". > It is > the centre of mass inertial system corresponding to the Earth and all > the GPS satellites, a well-determined real part of our real world. But > the introduced inertial frame B doesnt have any real body at all > associated with it, being that the reason why I denote it an imaginary > entity. > > > what can we say about the time rate of the ECI clocks appreciated by > > > an inertial observer at rest in B? > > > I answered that here above. Einstein also explained and elaborated on > > that issue in his 1905 paper with a slightly different example (in > > section 2), as follows: > > > "We imagine further that at the two ends A and B of the [moving] rod, > > clocks are placed which synchronize with the clocks of the stationary > > system, that is to say that their indications correspond at any > > instant to the ``time of the stationary system'' at the places where > > they happen to be. These clocks are therefore ``synchronous in the > > stationary system.'' > > [..] > > Einstein is describing here exactly what it is done in today GPS. Yes indeed - except for the gravitation effect, which SRT ignores. > The > stationary system is the ECI, the moving system is any GPS > satellite. The clock inside the satellite is synchronized in the > stationary system, not in the moving system. > > Observers moving with the moving rod would thus find that the two > > clocks were not synchronous, while observers in the stationary system > > would declare the clocks to be synchronous. ") > > Yes, an inertial observer at rest in the moving system (moving GPS > satellite) appreciates all ECI clocks out of synchronism, but who > care that? OK, perhaps I misunderstood what you tried to communicate - in which case I don't know what it was! In fact, you here agree with the SRT claim that clock synchronisation (along x) is "relative", in the sense that it is meant. > I feel now very happy with your very valuable reference to 1905 > Einstein first paper on Relativity. Now we can make real the imaginary > inertial frame B identifying it with a moving GPS satellite (the real > inertial frame B is the centre of mass one corresponding to the > satellite and all bodies in its interior). You can choose it as you wish, according to SRT (as long as it isn't rotating, which is incompatible with GPS satellites!). > Consider now the inertial Solar System (the centre of mass one of all > its bodies). In principle, we can synchronize clocks in all its > planets, showing all of them the same unique time defined by 1905 > Einstein. It is "unique" for the solar system, just as the pair of shoes that I wear are "unique" for me... > Of course, this time is not an absolute one, but maybe > something similar to it was in the mind of the OP of this thread when > choosing its title. Perhaps - but it looked as if he was still trying to understand the basics. Harald
From: BURT on 18 Mar 2010 15:12 On Mar 18, 8:49 am, harald <h...(a)swissonline.ch> wrote: > On Mar 18, 3:04 pm, va...(a)icmf.inf.cu wrote: > > > On 17 mar, 10:34, harald <h...(a)swissonline.ch> wrote: > > > > On Mar 17, 3:34 pm, va...(a)icmf.inf.cu wrote: > > > > > On 16 mar, 17:20, harald <h...(a)swissonline.ch> wrote: > > > > > > On Mar 16, 3:30 pm, va...(a)icmf.inf.cu wrote: > > > > > > > On 15 mar, 05:53, harald <h...(a)swissonline.ch> wrote: > > [..] > > > > > > > > > > > > > E-sync means that the ELAPSED times of both clocks correspond, as well as > > > > > > > > the readings at some time. E-sync'd clocks remain in synch. > > > > > > > > Thanks for the elaboration. But more precisely: e-synched "perfect", > > > > > > > "stationary" clocks remain in sync (if at the same gravitational > > > > > > > potential). Now, let's hope that the OP will understand this. :) > > > > > > > (Hello Harald, nice to meet you again). > > > > > > In the ECI frame of GPS all the clocks remain synchronized, even if > > > > > > they have different velocities and gravitational potentials. Then, > > > > > > taking into account that huge experimental evidence, I dont see any > > > > > > other alternative that to accept that absolute clock synchronization > > > > > > exists in SR with the following meaning. Once perfect and stationary > > > > > > clocks are e-synchronized in some inertial frame, they remain showing > > > > > > the same time lecture at any local instant in all the others inertial > > > > > > frames. Of course, that equal time lecture does not correspond to > > > > > > the local time in each of the others inertial frames, where according > > > > > > to SR rules, the now moving clocks (all with the same velocity) are > > > > > > running slower than the local perfect and stationary e-synchronised > > > > > > ones. > > > > > > > RVHG (Rafael Valls Hidalgo-Gato) > > [..] > > > > The topic of this thread is concerned with the fact that according to > > > all inertial reference systems in which the inertial reference system > > > with its synchronized clocks is moving, those clocks are out of sync > > > with each other (see also below). > > > > > I mentioned the ECI of GPS, taken for granted that the e- > > > > synchronization method of all its clocks is well-known. Let us > > > > remember that all the moving clocks show the unique ECI time, > > > > corresponding to the same time that a similar clock at rest in the > > > > relevant ECI point would show. If now we consider the ECI moving at a > > > > constant velocity with respect to an (imaginary) inertial frame B, > > > > Note: the ECI "frame" itself is already an imaginary frame... > > > I dont understand why you consider the ECI an imaginary frame. > > The whole Earth is rotating relative to it; there isn't any material > frame that is pretended to be "in rest". > > > > > > > It is > > the centre of mass inertial system corresponding to the Earth and all > > the GPS satellites, a well-determined real part of our real world. But > > the introduced inertial frame B doesnt have any real body at all > > associated with it, being that the reason why I denote it an imaginary > > entity. > > > > what can we say about the time rate of the ECI clocks appreciated by > > > > an inertial observer at rest in B? > > > > I answered that here above. Einstein also explained and elaborated on > > > that issue in his 1905 paper with a slightly different example (in > > > section 2), as follows: > > > > "We imagine further that at the two ends A and B of the [moving] rod, > > > clocks are placed which synchronize with the clocks of the stationary > > > system, that is to say that their indications correspond at any > > > instant to the ``time of the stationary system'' at the places where > > > they happen to be. These clocks are therefore ``synchronous in the > > > stationary system.'' > > > [..] > > > Einstein is describing here exactly what it is done in today GPS. > > Yes indeed - except for the gravitation effect, which SRT ignores. > > > The > > stationary system is the ECI, the moving system is any GPS > > satellite. The clock inside the satellite is synchronized in the > > stationary system, not in the moving system. > > > Observers moving with the moving rod would thus find that the two > > > clocks were not synchronous, while observers in the stationary system > > > would declare the clocks to be synchronous. ") > > > Yes, an inertial observer at rest in the moving system (moving GPS > > satellite) appreciates all ECI clocks out of synchronism, but who > > care that? > > OK, perhaps I misunderstood what you tried to communicate - in which > case I don't know what it was! > In fact, you here agree with the SRT claim that clock synchronisation > (along x) is "relative", in the sense that it is meant. > > > I feel now very happy with your very valuable reference to 1905 > > Einstein first paper on Relativity. Now we can make real the imaginary > > inertial frame B identifying it with a moving GPS satellite (the real > > inertial frame B is the centre of mass one corresponding to the > > satellite and all bodies in its interior). > > You can choose it as you wish, according to SRT (as long as it isn't > rotating, which is incompatible with GPS satellites!). > > > Consider now the inertial Solar System (the centre of mass one of all > > its bodies). In principle, we can synchronize clocks in all its > > planets, showing all of them the same unique time defined by 1905 > > Einstein. > > It is "unique" for the solar system, just as the pair of shoes that I > wear are "unique" for me... > > > Of course, this time is not an absolute one, but maybe > > something similar to it was in the mind of the OP of this thread when > > choosing its title. > > Perhaps - but it looked as if he was still trying to understand the > basics. > > Harald- Hide quoted text - > > - Show quoted text -- Hide quoted text - > > - Show quoted text - Quantum vibration does not slow time. The center of the wave moves and has a two rate clock. Mitch Raemsch
From: valls on 18 Mar 2010 18:27 On 18 mar, 10:49, harald <h...(a)swissonline.ch> wrote: > On Mar 18, 3:04 pm, va...(a)icmf.inf.cu wrote: > > > On 17 mar, 10:34, harald <h...(a)swissonline.ch> wrote: > > > > On Mar 17, 3:34 pm, va...(a)icmf.inf.cu wrote: > > > > > On 16 mar, 17:20, harald <h...(a)swissonline.ch> wrote: > > > > > > On Mar 16, 3:30 pm, va...(a)icmf.inf.cu wrote: > > > > > > > On 15 mar, 05:53, harald <h...(a)swissonline.ch> wrote: > > [..] > > > > > > > > > > > > > E-sync means that the ELAPSED times of both clocks correspond, as well as > > > > > > > > the readings at some time. E-sync'd clocks remain in synch. > > > > > > > > Thanks for the elaboration. But more precisely: e-synched "perfect", > > > > > > > "stationary" clocks remain in sync (if at the same gravitational > > > > > > > potential). Now, let's hope that the OP will understand this. :) > > > > > > > (Hello Harald, nice to meet you again). > > > > > > In the ECI frame of GPS all the clocks remain synchronized, even if > > > > > > they have different velocities and gravitational potentials. Then, > > > > > > taking into account that huge experimental evidence, I dont see any > > > > > > other alternative that to accept that absolute clock synchronization > > > > > > exists in SR with the following meaning. Once perfect and stationary > > > > > > clocks are e-synchronized in some inertial frame, they remain showing > > > > > > the same time lecture at any local instant in all the others inertial > > > > > > frames. Of course, that equal time lecture does not correspond to > > > > > > the local time in each of the others inertial frames, where according > > > > > > to SR rules, the now moving clocks (all with the same velocity) are > > > > > > running slower than the local perfect and stationary e-synchronised > > > > > > ones. > > > > > > > RVHG (Rafael Valls Hidalgo-Gato) > > [..] > > > > The topic of this thread is concerned with the fact that according to > > > all inertial reference systems in which the inertial reference system > > > with its synchronized clocks is moving, those clocks are out of sync > > > with each other (see also below). > > > > > I mentioned the ECI of GPS, taken for granted that the e- > > > > synchronization method of all its clocks is well-known. Let us > > > > remember that all the moving clocks show the unique ECI time, > > > > corresponding to the same time that a similar clock at rest in the > > > > relevant ECI point would show. If now we consider the ECI moving at a > > > > constant velocity with respect to an (imaginary) inertial frame B, > > > > Note: the ECI "frame" itself is already an imaginary frame... > > > I dont understand why you consider the ECI an imaginary frame. > > The whole Earth is rotating relative to it; there isn't any material > frame that is pretended to be "in rest". > I have a doubt here about what do you mean by material frame. Newton conceived a unique true material frame, totally independent from the bodies, denoting it as absolute space and absolute time. But we are talking here about 1905 Einstein, who declared superfluous any material frame independent from the bodies. Besides, as it was well- known long before 1905, ANY body set (with specific mass and velocity for each of its bodies modelled by a material point, except one that depends on the others) determine a UNIQUE inertial frame where following Newtons laws a UNIQUE spatial point can be obtained that can be considered at rest with respect to itself, named centre of mass. The Earth is rotating in the centre of mass inertial system determined by all its own parts. > > > > > > It is > > the centre of mass inertial system corresponding to the Earth and all > > the GPS satellites, a well-determined real part of our real world. But > > the introduced inertial frame B doesnt have any real body at all > > associated with it, being that the reason why I denote it an imaginary > > entity. > > > > what can we say about the time rate of the ECI clocks appreciated by > > > > an inertial observer at rest in B? > > > > I answered that here above. Einstein also explained and elaborated on > > > that issue in his 1905 paper with a slightly different example (in > > > section 2), as follows: > > > > "We imagine further that at the two ends A and B of the [moving] rod, > > > clocks are placed which synchronize with the clocks of the stationary > > > system, that is to say that their indications correspond at any > > > instant to the ``time of the stationary system'' at the places where > > > they happen to be. These clocks are therefore ``synchronous in the > > > stationary system.'' > > > [..] > > > Einstein is describing here exactly what it is done in today GPS. > > Yes indeed - except for the gravitation effect, which SRT ignores. > SRT was re-created in 1915 by Einstein (the word special was introduced then), adapting it to its new GRT. Even if in 1905 Relativity gravitation remains present (see the gravitational accelerated movement for the clock put on the rotating equator), 1905 Einstein doesnt knew yet the gravitation effect on the time rate of a clock. > > The > > stationary system is the ECI, the moving system is any GPS > > satellite. The clock inside the satellite is synchronized in the > > stationary system, not in the moving system. > > > Observers moving with the moving rod would thus find that the two > > > clocks were not synchronous, while observers in the stationary system > > > would declare the clocks to be synchronous. ") > > > Yes, an inertial observer at rest in the moving system (moving GPS > > satellite) appreciates all ECI clocks out of synchronism, but who > > care that? > > OK, perhaps I misunderstood what you tried to communicate - in which > case I don't know what it was! I prefer to put the emphasis in what we are in agreement now. Our own ideas can be evolving somewhat in the time. > In fact, you here agree with the SRT claim that clock synchronisation > (along x) is "relative", in the sense that it is meant. > Yes, without any doubt synchronization is relative to the inertial frame you select to do it. But let us take some care here, I distinguish a real inertial system (the centre of mass one associated to some well-determined body set) from an imaginary one (as all of them in the 1907 Minkowski view). > > I feel now very happy with your very valuable reference to 1905 > > Einstein first paper on Relativity. Now we can make real the imaginary > > inertial frame B identifying it with a moving GPS satellite (the real > > inertial frame B is the centre of mass one corresponding to the > > satellite and all bodies in its interior). > > You can choose it as you wish, according to SRT (as long as it isn't > rotating, which is incompatible with GPS satellites!). > An inertial frame can never be rotating. The space belonging to the ECI (or any other inertial frame) has always all its points at rest. > > Consider now the inertial Solar System (the centre of mass one of all > > its bodies). In principle, we can synchronize clocks in all its > > planets, showing all of them the same unique time defined by 1905 > > Einstein. > > It is "unique" for the solar system, just as the pair of shoes that I > wear are "unique" for me... > I dont think so. You can change your shoes, but not the unique time corresponding to the Solar System as long as it is maintained as a closed one (I forgot to mention explicitly that basic condition when talking about real inertial frames). > > Of course, this time is not an absolute one, but maybe > > something similar to it was in the mind of the OP of this thread when > > choosing its title. > > Perhaps - but it looked as if he was still trying to understand the > basics. > (Some final comments) I appreciate a lot this new contact with you. If I remember well, in the last one (how many years ago?) you said that my Hierarchical Inertial Frame (HIS) concept was a mix of different theories, including the Newtonian one. I continue thinking that 1905 Einstein discovered an absolute (and total, owed to ALL fields that can be present) potential energy measured by a variable rest mass (depending on position). Well, this is not the adequate place to talk about all these things. In reality, I address them now in order to be able to introduce a possible absolute time, the principal topic in this thread. What if we consider a sequence of real inertial frames, each one with a body set that includes de previous one?( Earth, Solar System, Galaxy, ). How far can we run in that hierarchy of HIS? If we have a finite number of bodies in our Universe, the sequence is finite and we would have all the right to denote as absolute time the one corresponding to the highest hierarchy last HIS. And if our Universe has infinite number of bodies, in all ways we can talk at least about an absolute time as a limit. RVHG (Rafael Valls Hidalgo-Gato) > Harald- Ocultar texto de la cita - > > - Mostrar texto de la cita -- Ocultar texto de la cita - > > - Mostrar texto de la cita -
From: GSS on 19 Mar 2010 04:52
On Mar 18, 8:49 pm, harald <h...(a)swissonline.ch> wrote: > On Mar 18, 3:04 pm, va...(a)icmf.inf.cu wrote: ..... >>>>>>> Thanks for the elaboration. But more precisely: e-synched "perfect", >>>>>>> "stationary" clocks remain in sync (if at the same gravitational >>>>>>> potential). Now, let's hope that the OP will understand this. :) > ..... >> Of course, this time is not an absolute one, but maybe >> something similar to it was in the mind of the OP of this thread when >> choosing its title. > > Perhaps - but it looked as if he was still trying to understand the > basics. > > Harald Maybe yes, I am still trying to understand the intricacies of clock synchronization under SR regime. Let us consider two identical precision atomic clocks, positioned at points A and B, separated by a distance of about 30 km along east- west direction, on the surface of earth. Assume the two clocks A and B are mutually synchronized through Einstein convention such that the time taken, T_ab, by a laser pulse to propagate from A to B (as measured from the clock readings of B and A) is the same as the time taken, T_ba, by a laser pulse to propagate from B to A. That means, T_ab - T_ba = 0 which indicates e-synchronization of the two clocks. In your opinion, will this synchronization remain valid at least for a 24 hour period? That is, if we take to and fro signal propagation time readings at hourly intervals, will all readings show, T_ab - T_ba = 0 Perhaps you may like to call this mutual synchronization of clocks A and B as the 'local clock synchronization' valid in the local or lab frame of the two clocks. Kindly explain the procedure for e-synchronization of the same two atomic clocks A and B in the ECI or the GCRF frame. How exactly will it be different from the local clock synchronization in practical terms? Since the two clocks under consideration are simultaneously known to be co-moving in the solar system at about 30 km/s, you may kindly explain the procedure for e-synchronization of the same two atomic clocks A and B in the solar system BCRF frame. How exactly will it be different from the local clock synchronization in practical terms? Going one step still further,the two clocks under consideration are simultaneously known to be co-moving in the Galactic reference frame at about 200 km/s. Kindly explain the procedure for e-synchronization of the same two atomic clocks A and B in the Galactic reference frame. How exactly will it be different from the local clock synchronization in practical terms? For the sake of simplicity of discussions, you may completely neglect the gravitational effects on clock synchronization and only account for the SR effects. GSS |