Notion of Absolute Clock Synchronization in SR
in [Relativity]
|
From: Sue... on 16 Mar 2010 15:11 On Mar 16, 3:01 pm, 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". > > > 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 [coordinate time] > clocks in frame A, and looking at them > from frame B, they are not in synch if B is moving wrt A. http://en.wikipedia.org/wiki/Coordinate_time http://en.wikipedia.org/wiki/Einstein_synchronisation http://en.wikipedia.org/wiki/Lorentz_ether_theory#Later_activity_and_Current_Status Sue.... > > 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". > > Tom Roberts
From: harald on 16 Mar 2010 18:20 On Mar 16, 3:30 pm, va...(a)icmf.inf.cu wrote: > On 15 mar, 05:53, harald <h...(a)swissonline.ch> wrote: > > > On Mar 15, 11:33 am, "Inertial" <relativ...(a)rest.com> wrote: > > > > "harald" <h...(a)swissonline.ch> wrote in message > > > >news:b4db03e0-4bbb-4ab5-8aca-497de387f1fe(a)g19g2000yqe.googlegroups.com.... > > > > > On Mar 12, 5:13 pm, Tom Roberts <tjrob...(a)sbcglobal.net> wrote: > > > >> harald wrote: > > > >> > [clocks] can also be > > > >> > synchronized at a certain point in time (only at that time) without > > > >> > having the same frequency. > > > > >> We do not call this "synchronized". The whole point of synchronizing > > > >> clocks is > > > >> so they can be used together to make related measurements of something. > > > >> Two > > > >> clocks that indicate the same time only once cannot be used together. > > > > >> After all, a stopped "clock" is correct twice a day! > > > >> (In physics, we don't call such a device a "clock"; it is > > > >> merely a clockface with unmoving hands.) > > > > >> Tom Roberts > > > > > That misses the point of my correction of the OP (both of which you > > > > snipped) and my last remark was in general*. The OP wrongly thought > > > > that two clocks that have the same frequency are necessarily > > > > synchronized. The OP thus missed an essential point about > > > > synchronizing clocks. > > > > Yeup > > > > > * It's unclear who "we" are. For physicists it's rather standard to > > > > synchronize running clocks at the start of an experiment without > > > > assuming that they run perfectly in sync during the experiment > > > > Then there is not much point in doing so :) > > > Perfect clocks for experiments don't exist - we just have to account > > for the errors in practice. In theoretical descriptions we can work > > with "perfect" clocks, but even those can deviate as illustrated > > below. > > > > > , and > > > > this is also common language of textbooks (see for an online example > > > >http://mamacass.ucsd.edu/people/pblanco/physics2d/handout1/index.html: > > > > "we can arrange for the clocks to synchronize when O' passes O, i.e.. > > > > t'=t=0"). > > > > Yes .. you can synchronize them momentarily. But they are not e-synced > > > then. > > > > There problem here is two different uses of the term. > > > Indeed, the LT's t0 sync is a different synchronization. > > > > Synchronizing clocks in the first sense means making their readings show the > > > same time AT the same time. Such clocks may only be synchrnoized for a > > > moment. > > > > 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) Hi Rafael, how are you doing? What you claim here above is completely wrong. As I already indicated, clocks that have been synchronized (both in setting and in pace) "in" one reference system, will deviate if they are put at another gravitational potential or given another speed without being re-tuned. See also the clarifications of Tom Roberts. Harald
From: valls on 17 Mar 2010 10:34 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: > > > > On Mar 15, 11:33 am, "Inertial" <relativ...(a)rest.com> wrote: > > > > > "harald" <h...(a)swissonline.ch> wrote in message > > > > >news:b4db03e0-4bbb-4ab5-8aca-497de387f1fe(a)g19g2000yqe.googlegroups.com... > > > > > > On Mar 12, 5:13 pm, Tom Roberts <tjrob...(a)sbcglobal.net> wrote: > > > > >> harald wrote: > > > > >> > [clocks] can also be > > > > >> > synchronized at a certain point in time (only at that time) without > > > > >> > having the same frequency. > > > > > >> We do not call this "synchronized". The whole point of synchronizing > > > > >> clocks is > > > > >> so they can be used together to make related measurements of something. > > > > >> Two > > > > >> clocks that indicate the same time only once cannot be used together. > > > > > >> After all, a stopped "clock" is correct twice a day! > > > > >> (In physics, we don't call such a device a "clock"; it is > > > > >> merely a clockface with unmoving hands.) > > > > > >> Tom Roberts > > > > > > That misses the point of my correction of the OP (both of which you > > > > > snipped) and my last remark was in general*. The OP wrongly thought > > > > > that two clocks that have the same frequency are necessarily > > > > > synchronized. The OP thus missed an essential point about > > > > > synchronizing clocks. > > > > > Yeup > > > > > > * It's unclear who "we" are. For physicists it's rather standard to > > > > > synchronize running clocks at the start of an experiment without > > > > > assuming that they run perfectly in sync during the experiment > > > > > Then there is not much point in doing so :) > > > > Perfect clocks for experiments don't exist - we just have to account > > > for the errors in practice. In theoretical descriptions we can work > > > with "perfect" clocks, but even those can deviate as illustrated > > > below. > > > > > > , and > > > > > this is also common language of textbooks (see for an online example > > > > >http://mamacass.ucsd.edu/people/pblanco/physics2d/handout1/index.html: > > > > > "we can arrange for the clocks to synchronize when O' passes O, i..e. > > > > > t'=t=0"). > > > > > Yes .. you can synchronize them momentarily. But they are not e-synced > > > > then. > > > > > There problem here is two different uses of the term. > > > > Indeed, the LT's t0 sync is a different synchronization. > > > > > Synchronizing clocks in the first sense means making their readings show the > > > > same time AT the same time. Such clocks may only be synchrnoized for a > > > > moment. > > > > > 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) > > Hi Rafael, how are you doing? > What you claim here above is completely wrong. As I already indicated, > clocks that have been synchronized (both in setting and in pace) "in" > one reference system, will deviate if they are put at another > gravitational potential or given another speed without being re-tuned. > See also the clarifications of Tom Roberts. > Yes, after reading Tom Roberts, Inertial and Harald replies to my last post, I admit serious mistakes in it. We are in agreement about the fact that the time rate of a clock depends on gravitational potential and speed, and surely we can add other physical conditions (like temperature, for example). We must take into account all the physical factors that affect the time rate of a clock when e-synchronizing them in some inertial frame, with the goal that all the clocks show the unique time characteristic of the involved inertial frame (ECI in this case) according to 1905 Einstein very precise time definition. But what change in gravitational potential or speed for a clock already e-synchronized on the ECI are you talking about? Are you suggesting that a completely arbitrary change in the reference system can put the whole Earth moving with a linear velocity as great as you want? That seems completely absurd to me. 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, what can we say about the time rate of the ECI clocks appreciated by an inertial observer at rest in B? Even accepting (what I really put in doubt) that this change in the reference frame is a physically valid one, I am unable to understand what is occurring here following the today accepted SR rules. It was a mistake from my part to say something about the time rate of the ECI clocks as appreciated for the inertial observer at rest in B. RVHG (Rafael Valls Hidalgo-Gato) > Harald- Ocultar texto de la cita - > > - Mostrar texto de la cita -
From: harald on 17 Mar 2010 11:34 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: > > > > > On Mar 15, 11:33 am, "Inertial" <relativ...(a)rest.com> wrote: > > > > > > "harald" <h...(a)swissonline.ch> wrote in message > > > > > >news:b4db03e0-4bbb-4ab5-8aca-497de387f1fe(a)g19g2000yqe.googlegroups..com... > > > > > > > On Mar 12, 5:13 pm, Tom Roberts <tjrob...(a)sbcglobal.net> wrote: > > > > > >> harald wrote: > > > > > >> > [clocks] can also be > > > > > >> > synchronized at a certain point in time (only at that time) without > > > > > >> > having the same frequency. > > > > > > >> We do not call this "synchronized". The whole point of synchronizing > > > > > >> clocks is > > > > > >> so they can be used together to make related measurements of something. > > > > > >> Two > > > > > >> clocks that indicate the same time only once cannot be used together. > > > > > > >> After all, a stopped "clock" is correct twice a day! > > > > > >> (In physics, we don't call such a device a "clock"; it is > > > > > >> merely a clockface with unmoving hands.) > > > > > > >> Tom Roberts > > > > > > > That misses the point of my correction of the OP (both of which you > > > > > > snipped) and my last remark was in general*. The OP wrongly thought > > > > > > that two clocks that have the same frequency are necessarily > > > > > > synchronized. The OP thus missed an essential point about > > > > > > synchronizing clocks. > > > > > > Yeup > > > > > > > * It's unclear who "we" are. For physicists it's rather standard to > > > > > > synchronize running clocks at the start of an experiment without > > > > > > assuming that they run perfectly in sync during the experiment > > > > > > Then there is not much point in doing so :) > > > > > Perfect clocks for experiments don't exist - we just have to account > > > > for the errors in practice. In theoretical descriptions we can work > > > > with "perfect" clocks, but even those can deviate as illustrated > > > > below. > > > > > > > , and > > > > > > this is also common language of textbooks (see for an online example > > > > > >http://mamacass.ucsd.edu/people/pblanco/physics2d/handout1/index..html: > > > > > > "we can arrange for the clocks to synchronize when O' passes O, i.e. > > > > > > t'=t=0"). > > > > > > Yes .. you can synchronize them momentarily. But they are not e-synced > > > > > then. > > > > > > There problem here is two different uses of the term. > > > > > Indeed, the LT's t0 sync is a different synchronization. > > > > > > Synchronizing clocks in the first sense means making their readings show the > > > > > same time AT the same time. Such clocks may only be synchrnoized for a > > > > > moment. > > > > > > 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) > > > Hi Rafael, how are you doing? > > What you claim here above is completely wrong. As I already indicated, > > clocks that have been synchronized (both in setting and in pace) "in" > > one reference system, will deviate if they are put at another > > gravitational potential or given another speed without being re-tuned. > > See also the clarifications of Tom Roberts. > > Yes, after reading Tom Roberts, Inertial and Harald replies to my last > post, I admit serious mistakes in it. We are in agreement about the > fact that the time rate of a clock depends on gravitational potential > and speed, and surely we can add other physical conditions (like > temperature, for example). We must take into account all the physical > factors that affect the time rate of a clock when e-synchronizing them > in some inertial frame, with the goal that all the clocks show the > unique time characteristic of the involved inertial frame (ECI in this > case) according to 1905 Einstein very precise time definition. But > what change in gravitational potential or speed for a clock already > e-synchronized on the ECI are you talking about? Are you suggesting > that a completely arbitrary change in the reference system can put the > whole Earth moving with a linear velocity as great as you want? That > seems completely absurd to me. Not sure if this has much to do with the topic. However, I'll try to clarify, although I'm not sure where the misunderstanding comes from: "Perfect" synchronized "stationary" clocks remain in sync; in contrast, if they are made to move or put at another height, they'll fall out of sync with the remaining "stationary" reference clocks if nothing is done about it. That's all that I clarified, before and after you commented on it. It was just a remark on the side for the OP's understanding of "synchronization", it's not the topic of this thread. 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... > 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.'' [..] 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. ") > Even accepting (what I really put > in doubt) that this change in the reference frame is a physically > valid one, I am unable to understand what is occurring here following > the today accepted SR rules. It was a mistake from my part to say > something about the time rate of the ECI clocks as appreciated for the > inertial observer at rest in B. Regards, Harald
From: valls on 18 Mar 2010 10:04
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: > > > > > > On Mar 15, 11:33 am, "Inertial" <relativ...(a)rest.com> wrote: > > > > > > > "harald" <h...(a)swissonline.ch> wrote in message > > > > > > >news:b4db03e0-4bbb-4ab5-8aca-497de387f1fe(a)g19g2000yqe.googlegroups.com... > > > > > > > > On Mar 12, 5:13 pm, Tom Roberts <tjrob...(a)sbcglobal.net> wrote: > > > > > > >> harald wrote: > > > > > > >> > [clocks] can also be > > > > > > >> > synchronized at a certain point in time (only at that time) without > > > > > > >> > having the same frequency. > > > > > > > >> We do not call this "synchronized". The whole point of synchronizing > > > > > > >> clocks is > > > > > > >> so they can be used together to make related measurements of something. > > > > > > >> Two > > > > > > >> clocks that indicate the same time only once cannot be used together. > > > > > > > >> After all, a stopped "clock" is correct twice a day! > > > > > > >> (In physics, we don't call such a device a "clock"; it is > > > > > > >> merely a clockface with unmoving hands.) > > > > > > > >> Tom Roberts > > > > > > > > That misses the point of my correction of the OP (both of which you > > > > > > > snipped) and my last remark was in general*. The OP wrongly thought > > > > > > > that two clocks that have the same frequency are necessarily > > > > > > > synchronized. The OP thus missed an essential point about > > > > > > > synchronizing clocks. > > > > > > > Yeup > > > > > > > > * It's unclear who "we" are. For physicists it's rather standard to > > > > > > > synchronize running clocks at the start of an experiment without > > > > > > > assuming that they run perfectly in sync during the experiment > > > > > > > Then there is not much point in doing so :) > > > > > > Perfect clocks for experiments don't exist - we just have to account > > > > > for the errors in practice. In theoretical descriptions we can work > > > > > with "perfect" clocks, but even those can deviate as illustrated > > > > > below. > > > > > > > > , and > > > > > > > this is also common language of textbooks (see for an online example > > > > > > >http://mamacass.ucsd.edu/people/pblanco/physics2d/handout1/index.html: > > > > > > > "we can arrange for the clocks to synchronize when O' passes O, i.e. > > > > > > > t'=t=0"). > > > > > > > Yes .. you can synchronize them momentarily. But they are not e-synced > > > > > > then. > > > > > > > There problem here is two different uses of the term. > > > > > > Indeed, the LT's t0 sync is a different synchronization. > > > > > > > Synchronizing clocks in the first sense means making their readings show the > > > > > > same time AT the same time. Such clocks may only be synchrnoized for a > > > > > > moment. > > > > > > > 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) > > > > Hi Rafael, how are you doing? > > > What you claim here above is completely wrong. As I already indicated, > > > clocks that have been synchronized (both in setting and in pace) "in" > > > one reference system, will deviate if they are put at another > > > gravitational potential or given another speed without being re-tuned.. > > > See also the clarifications of Tom Roberts. > > > Yes, after reading Tom Roberts, Inertial and Harald replies to my last > > post, I admit serious mistakes in it. We are in agreement about the > > fact that the time rate of a clock depends on gravitational potential > > and speed, and surely we can add other physical conditions (like > > temperature, for example). We must take into account all the physical > > factors that affect the time rate of a clock when e-synchronizing them > > in some inertial frame, with the goal that all the clocks show the > > unique time characteristic of the involved inertial frame (ECI in this > > case) according to 1905 Einstein very precise time definition. But > > what change in gravitational potential or speed for a clock already > > e-synchronized on the ECI are you talking about? Are you suggesting > > that a completely arbitrary change in the reference system can put the > > whole Earth moving with a linear velocity as great as you want? That > > seems completely absurd to me. > > Not sure if this has much to do with the topic. However, I'll try to > clarify, although I'm not sure where the misunderstanding comes from: > > "Perfect" synchronized "stationary" clocks remain in sync; in > contrast, if they are made to move or put at another height, they'll > fall out of sync with the remaining "stationary" reference clocks if > nothing is done about it. That's all that I clarified, before and > after you commented on it. It was just a remark on the side for the > OP's understanding of "synchronization", it's not the topic of this > thread. > > 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. 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. 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? 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). 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. 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. > > Even accepting (what I really put > > in doubt) that this change in the reference frame is a physically > > valid one, I am unable to understand what is occurring here following > > the today accepted SR rules. It was a mistake from my part to say > > something about the time rate of the ECI clocks as appreciated for the > > inertial observer at rest in B. > > Regards, > Harald- Ocultar texto de la cita - > > - Mostrar texto de la cita - |