Notion of Absolute Clock Synchronization in SR
in [Relativity]
|
From: valls on 22 Mar 2010 13:49 On 22 mar, 06:39, "Androcles" <Headmas...(a)Hogwarts.physics_w> wrote: > <va...(a)icmf.inf.cu> wrote in message > > news:c7f6d7b8-bbb7-4a86-8af8-c9b01bdf8e09(a)t20g2000yqe.googlegroups.com... > On 20 mar, 07:15, harald <h...(a)swissonline.ch> wrote: > > > > > On Mar 19, 5:39 pm, va...(a)icmf.inf.cu wrote: > > > > On 19 mar, 04:23, harald <h...(a)swissonline.ch> wrote: > > > > > On Mar 18, 11:27 pm, va...(a)icmf.inf.cu wrote: > > > > > > 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. > > > > > A stiff thing made up of atoms (such as earth, wood, steel or > > > > concrete). > > > > > [..] > > > > > > > > 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). > > > > > Sure we can - we can set t=0 whenever we want, and also choose our > > > > time standard. > > > > From your last answer I deduce that we dont share a common > > > interpretation about what is the time defined by 1905 Einstein. Let > > > us take two very well-known real inertial systems, the ECI and the > > > Solar System (SS). Let me ask you a very crucial question. Can be two > > > GPS clocks (for example one in a satellite and another in the Earths > > > surface) e-synchronized with respect to the ECI and at the same time > > > also e-synchronized with respect to the SS? > > > The essential difference between the (1905 Einstein) times of two > > > different inertial systems has no relation at all with the totally > > > arbitrary selection of initial instants and time standard units in > > > both systems. > > > Perhaps you meant with "unique time", "unique synchronization"? Most > > people would call that not "absolute" but "relative" synchronization. > > Anyway, I'm not at all interested in debates over words. > > I didnt use the word unique in the comment where I made you a clear > question. I repeat it: > Can be two GPS clocks (for example one in a satellite and another in > the Earths > surface) e-synchronized with respect to the ECI and at the same time > also e-synchronized with respect to the SS? > I am referring to the synchronization described by 1905 Einstein in > his first relativity paper (30 June 1905). > As you, I am also not interested at all in any debate about simple > words. > If it helps you to answer the question, my opinion is that it must be > answered with a clear no. I want to know if we are in agreement > about this point or not. > > RVHG (Rafael Valls Hidalgo-Gato) > ============================================ > If you are not interest in words, why add confusion with "e-synchronized" ? > That's not a word. > Einstein said: > > 1.. If the clock at B synchronizes with the clock at A, the clock at A > synchronizes with the clock at B. > 2.. If the clock at A synchronizes with the clock at B and also with the > clock at C, the clocks at B and C also synchronize with each other. > He didn't say "e-synchronized". > Hello Androcles, do you remember our very long talkings many years ago? I used the expression "e-synchronized" only because some other persons in this thread use it. Anyway, I put clear that I am referring to 1905 Einstein's synchronization process (in the context of his "time" definition). > Can be two Global Positioning System (GPS) clocks (for example one in > a satellite and another in the Earths surface)... > The GPS doesn't ever use a clock on the Earth's surface, GPS receivers > don't have atomic clocks or need clocks at all. > However, atomic clocks upload position and time to the satellites and > they are ALL synchronized. Of course that GPS receivers have not atomic clocks, I am refering to those last ones mentioned by you (that are at the Earth's surface). RVHG (Rafael Valls Hidalgo-Gato)
From: Androcles on 22 Mar 2010 14:19 <valls(a)icmf.inf.cu> wrote in message news:290f9863-733d-46e3-b3c9-15ba51e4c26a(a)k17g2000yqb.googlegroups.com... On 22 mar, 06:39, "Androcles" <Headmas...(a)Hogwarts.physics_w> wrote: > <va...(a)icmf.inf.cu> wrote in message > > news:c7f6d7b8-bbb7-4a86-8af8-c9b01bdf8e09(a)t20g2000yqe.googlegroups.com... > On 20 mar, 07:15, harald <h...(a)swissonline.ch> wrote: > > > > > On Mar 19, 5:39 pm, va...(a)icmf.inf.cu wrote: > > > > On 19 mar, 04:23, harald <h...(a)swissonline.ch> wrote: > > > > > On Mar 18, 11:27 pm, va...(a)icmf.inf.cu wrote: > > > > > > 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 > > > > > > > > > > > don�t 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 don�t 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�. > > > > > A stiff thing made up of atoms (such as earth, wood, steel or > > > > concrete). > > > > > [..] > > > > > > > > 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 don�t 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). > > > > > Sure we can - we can set t=0 whenever we want, and also choose our > > > > time standard. > > > > From your last answer I deduce that we don�t share a common > > > interpretation about what is the �time� defined by 1905 Einstein. Let > > > us take two very well-known real inertial systems, the ECI and the > > > Solar System (SS). Let me ask you a very crucial question. Can be two > > > GPS clocks (for example one in a satellite and another in the Earth�s > > > surface) e-synchronized with respect to the ECI and at the same time > > > also e-synchronized with respect to the SS? > > > The essential difference between the (1905 Einstein) times of two > > > different inertial systems has no relation at all with the totally > > > arbitrary selection of initial instants and time standard units in > > > both systems. > > > Perhaps you meant with "unique time", "unique synchronization"? Most > > people would call that not "absolute" but "relative" synchronization. > > Anyway, I'm not at all interested in debates over words. > > I didn�t use the word �unique� in the comment where I made you a clear > question. I repeat it: > Can be two GPS clocks (for example one in a satellite and another in > the Earth�s > surface) e-synchronized with respect to the ECI and at the same time > also e-synchronized with respect to the SS? > I am referring to the synchronization described by 1905 Einstein in > his first relativity paper (30 June 1905). > As you, I am also not interested at all in any debate about simple > words. > If it helps you to answer the question, my opinion is that it must be > answered with a clear �no�. I want to know if we are in agreement > about this point or not. > > RVHG (Rafael Valls Hidalgo-Gato) > ============================================ > If you are not interest in words, why add confusion with "e-synchronized" > ? > That's not a word. > Einstein said: > > 1.. If the clock at B synchronizes with the clock at A, the clock at A > synchronizes with the clock at B. > 2.. If the clock at A synchronizes with the clock at B and also with the > clock at C, the clocks at B and C also synchronize with each other. > He didn't say "e-synchronized". > Hello Androcles, do you remember our very long talkings many years ago? ================================================ Hopefully you've very long maturings since then. ================================================ I used the expression "e-synchronized" only because some other persons in this thread use it. Anyway, I put clear that I am referring to 1905 Einstein's synchronization process (in the context of his "time" definition). ================================================ "Synchronized" only means "set to the same time", it has nothing to do with a clock running fast or slow compared to another or compared to the daily rotation of the Earth on its own axis, or its yearly revolution around the Sun along with the Earth. One GPS satellite year is identical to one Earth year, Einstein was an idiot. > Can be two Global Positioning System (GPS) clocks (for example one in > a satellite and another in the Earth�s surface)... > The GPS doesn't ever use a clock on the Earth's surface, GPS receivers > don't have atomic clocks or need clocks at all. > However, atomic clocks upload position and time to the satellites and > they are ALL synchronized. Of course that GPS receivers have not atomic clocks, I am refering to those last ones mentioned by you (that are at the Earth's surface). ================================================ All clocks tick, the count of the ticks for identical clocks is the same number of ticks each year or they would not be identical, Einstein was an idiot. "Thence we conclude that a balance-clock at the equator must go more slowly, by a very small amount, than a precisely similar clock situated at one of the poles under otherwise identical conditions." -- Einstein. Anyway, I put clear that I am referring to 1905 Einstein's � 4. Physical Meaning of the Equations Obtained in Respect to Moving Rigid Bodies and Moving Clocks found in http://www.fourmilab.ch/etexts/einstein/specrel/www/. Thence we conclude that Einstein was a babbling cretin and a complete ignoramus who knew nothing of physics or mathematics, and neither does Van lintel the lentil.
From: valls on 23 Mar 2010 09:53 On 22 mar, 13:19, "Androcles" <Headmas...(a)Hogwarts.physics_w> wrote: > <va...(a)icmf.inf.cu> wrote in message > > news:290f9863-733d-46e3-b3c9-15ba51e4c26a(a)k17g2000yqb.googlegroups.com... > On 22 mar, 06:39, "Androcles" <Headmas...(a)Hogwarts.physics_w> wrote:> <va....(a)icmf.inf.cu> wrote in message > > >news:c7f6d7b8-bbb7-4a86-8af8-c9b01bdf8e09(a)t20g2000yqe.googlegroups.com.... > > On 20 mar, 07:15, harald <h...(a)swissonline.ch> wrote: > ............................... > > > I didnt use the word unique in the comment where I made you a clear > > question. I repeat it: > > Can be two GPS clocks (for example one in a satellite and another in > > the Earths > > surface) e-synchronized with respect to the ECI and at the same time > > also e-synchronized with respect to the SS? > > I am referring to the synchronization described by 1905 Einstein in > > his first relativity paper (30 June 1905). > > As you, I am also not interested at all in any debate about simple > > words. > > If it helps you to answer the question, my opinion is that it must be > > answered with a clear no. I want to know if we are in agreement > > about this point or not. > > > RVHG (Rafael Valls Hidalgo-Gato) > > ============================================ > > If you are not interest in words, why add confusion with "e-synchronized" > > ? > > That's not a word. > > Einstein said: > > > 1.. If the clock at B synchronizes with the clock at A, the clock at A > > synchronizes with the clock at B. > > 2.. If the clock at A synchronizes with the clock at B and also with the > > clock at C, the clocks at B and C also synchronize with each other. > > He didn't say "e-synchronized". > > Hello Androcles, do you remember our very long talkings many years > ago? > > ================================================ > Hopefully you've very long maturings since then. > > ================================================ > > I used the expression "e-synchronized" only because some other persons > in this thread use it. Anyway, I put clear that I am referring to 1905 > Einstein's synchronization process (in the context of his "time" > definition). > ================================================ > "Synchronized" only means "set to the same time", it has nothing to do > with a clock running fast or slow compared to another or compared to > the daily rotation of the Earth on its own axis, or its yearly revolution > around the Sun along with the Earth. One GPS satellite year is identical > to one Earth year, Einstein was an idiot. > > > Can be two Global Positioning System (GPS) clocks (for example one in > > a satellite and another in the Earths surface)... > > The GPS doesn't ever use a clock on the Earth's surface, GPS receivers > > don't have atomic clocks or need clocks at all. > > However, atomic clocks upload position and time to the satellites and > > they are ALL synchronized. > > Of course that GPS receivers have not atomic clocks, I am refering to > those last ones mentioned by you (that are at the Earth's surface). > > ================================================ > > All clocks tick, the count of the ticks for identical clocks is the same > number of ticks each year or they would not be identical, Einstein was > an idiot. > > "Thence we conclude that a balance-clock at the equator must go more > slowly, by a very small amount, than a precisely similar clock situated at > one of the poles under otherwise identical conditions." -- Einstein. > > Anyway, I put clear that I am referring to 1905 Einstein's § 4. Physical > Meaning of the Equations Obtained in Respect to Moving Rigid Bodies and > Moving Clocks found inhttp://www.fourmilab.ch/etexts/einstein/specrel/www/. > > Thence we conclude that Einstein was a babbling cretin and a complete > ignoramus who knew nothing of physics or mathematics, and neither does > Van lintel the lentil. If we have two identical synchronized clocks (with the same physical conditions in some real inertial frame), they get out of synchronism when you alter the physical conditions of one of them (but returning it to the initial ones in order to compare the time registered by the clocks in the same initial physical conditions). This is an experimental fact that you cant reject as a scientist. Surely you know the Hafele&Keating experiment and the huge experimental evidence of today GPS. I can accept that synchronized means "set to the same time", even knowing that you believe in the existence of a unique time. OK, let us consider that the two clocks are synchronized (by you at your unique time, surely you know how to do it) at an Earths pole, changing later one of them to the equator (of an Earth considered a perfect sphere, to avoid complications with the gravitational potential not known yet by 1905 Einstein). After some time we can return the clock at the equator to the pole to compare with the other, to see if 1905 Einstein was right or not. We can change a little the experiment putting first two synchronized clocks at the equator (needing again your help to put them reading your unique time) and changing later one of them to a pole, returning it after some time to its original position at the equator. Which will be the result? RVHG (Rafael Valls Hidalgo-Gato)
From: GSS on 25 Mar 2010 11:29 On Mar 22, 8:45 pm, Tom Roberts <tjrob...(a)sbcglobal.net> wrote: > GSS wrote: >> 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. > > OK, that's clear enough. But note there is no inertial frame in which these > clocks are synchronized, and that is usually a prerequisite for calling them > "synchronized". Your measurements and operations are clear, but applying the > word "synchronized" to this is not so clear. If you cannot apply the word "synchronized" in this case, which other word, you think, is more appropriate? At any instant, when TAI time is t1, if each one of the two 'ideal' clocks A and B show the same time t1, shouldn't we call them 'mutually' synchronized, irrespective of the reference frame in which we may consider them to be located at that instant? Further, at any given instant, the two ideal clocks A and B under consideration can be viewed as 'physically' located in many inertial reference frames like ECI, BCRF and Galactic reference frame, even though they are not *at rest* in any of them. Why should the physical state of the two clocks being 'in synchronization', change when we refer their location to ECI or BCRF or the Galactic frame? Choice of a reference frame is our 'human' artifact, and this choice must not influence a physical phenomenon of two clocks being 'in synchronization' or 'not in synchronization'. Isn't this awkward situation a consequence of equally awkward second postulate of SR? > >> 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 > > Modulo drifts in the individual clocks, yes. In gedankens we invariably use > ideal clocks, so they don't drift, and the answer is an unqualified yes. That's > because in such gedankens we also ignore such tiny things as the variation in > earth's rotational rate (which would turn that into a "no", but the variations > would be far below present technology's resolution). > This "unqualified yes" is an important statement. Assume the time resolution of available atomic clocks is limited to one ns, and that their locations A and B are at the same gravitational potential. Can you confirm that the state of mutual synchronization of the two clocks (represented by T_ab - T_ba = 0) will remain valid for a 24 hour period, irrespective of the rotational motion of the earth about its axis? Specifically, I want you to confirm that there will be no 'significant' diurnal variation in the value of (T_ab - T_ba) which should remain within +/- one ns during the 24 hour testing period. >> 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? > > To do this, one must set the clocks so that they display the time of a > coordinate clock of the ECI that is located where the moving clock is located at > the instant in question. ECI coordinate clocks, of course, are at rest in the > ECI frame, and because the ECI is supposed to be an inertial frame in the sense > of SR (not GR), gravitation does not affect ECI coordinate clocks. This means > that the moving clocks must all be modified so that effects of their motion and > gravitational potential are compensated. The result is that all such moving > clocks are modified and initialized so they always indicate the time that an ECI > coordinate clock would indicate at the moving clock's current location. This is > how the GPS was set up. > Since physically no atomic clock can ever be at *rest* in the ECI frame, do you mean to imply that in order to synchronize the clocks A and B (at rest on the earth surface) in the ECI frame, their time offsets will have to be physically altered or adjusted to suit the computations of SR? GSS
From: PD on 25 Mar 2010 11:40
On Mar 25, 10:29 am, GSS <gurcharn_san...(a)yahoo.com> wrote: > > If you cannot apply the word "synchronized" in this case, which other > word, you think, is more appropriate? > > At any instant, when TAI time is t1, if each one of the two 'ideal' > clocks A and B show the same time t1, shouldn't we call them > 'mutually' synchronized, irrespective of the reference frame in which > we may consider them to be located at that instant? You can certainly do that. You can choose a clock to be the master clock of all clocks and use your definition to declare that all clocks have been thus synchronized, regardless of reference frame the clock belongs to. The problem then becomes that the laws of physics will depend on which clock is being used. This becomes evident when you time, say, a chemical clock reaction that is local to the master clock, and the same chemical clock reaction that is local to a different clock. Though the two clocks will remain synchronized, the two clocks will report different times for the local copies of the chemical clock reaction. And the obvious question would be, which of these is right, since they are IDENTICAL measurements? Note this is different than the case of two clocks observing the same process, since one of them will be in the rest frame of the process and the other will be in a frame with relative motion to the process. PD |