Notion of Absolute Clock Synchronization in SR
in [Relativity]
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From: Androcles on 7 Apr 2010 03:32 "Tom Adams" <tadamsmar(a)yahoo.com> wrote in message news:d48f740f-4aa9-4fc2-ad2f-41a59f23816f(a)w42g2000yqm.googlegroups.com... On Mar 12, 9:31 am, GSS <gurcharn_san...(a)yahoo.com> wrote: > On Mar 11, 10:58 pm, PD <thedraperfam...(a)gmail.com> wrote: > > > > > On Mar 11, 9:35 am, GSS <gurcharn_san...(a)yahoo.com> wrote: > > >> As per Newtonian notion of absolute space and time, clocks can be > >> synchronized in absolute terms such that identical precision atomic > >> clocks located anywhere within the solar system and in any state of > >> motion, will read the same time t1 when a standard master clock reads > >> t1. This notion of absolute clock synchronization implies the notion > >> of absolute simultaneity. > > >> However, as per SR, spatial distance and time measurements have been > >> rendered 'relative' and cannot be the same value for different > >> observers in different states of motion. As per SR the notion of > >> global 'absolute simultaneity' is fundamentally invalid for different > >> observers in different states of motion. Therefore, the notion of > >> global 'absolute clock synchronization' (in contrast to e- > >> synchronization) is no longer valid in SR. > > >> Since the term 'absolute clock synchronization' is often used in > >> discussions, I would like to request some Relativity experts to kindly > >> clarify the precise definition of absolute clock synchronization in > >> SR. > > > Sure. One such procedure is as follows. > > 1. Start at clock A and note the time T1. > > 2. Proceed to clock B by any method of travel that is guaranteed to be > > at constant speed. > > 3. At arrival at clock B, note the time T2. > > 4. Proceed back to clock A by the same method of travel, and at the > > same speed. > > 5. At arrival at clock A, note the time T3. > > 6. If T3-T2 = T2 - T1, then the clocks are synchronized. If T3-T2 > T2- > > T1, then clock B is running slow and should be set forward by half the > > difference noted. If T3-T2 < T2-T1, then clock B is running fast and > > should be set back by half the difference noted. > > >> Kindly illustrate the procedure, through some 'thought experiment' > >> or 'gedanken', to achieve absolute clock synchronization for all > >> observers in different states of motion within our solar system. > > > This cannot be done, given what we know about the laws of physics. > > >> Further, I also need some expert opinion on the following situation, > >> involving clock synchronization. > > >> Two identical precision atomic clocks are positioned side by side at > >> point A on the surface of earth and mutually synchronized to ensure > >> that > >> (a) their clock rates or frequencies are exactly matched or > >> synchronized > >> (b) their instantaneous timing offsets are eliminated to ensure that a > >> common trigger pulse yields the same timing reading t1 from both > >> clocks. > > >> Assuming the inherent drift of the two atomic clocks is identical and > >> well within 100 ps per day, it can be demonstrated that while the two > >> clocks remain side by side, their synchronization, after a period of > >> one day, is retained at well within one ns accuracy. > > >> Let us shift one of the synchronized atomic clocks to a position B > >> such that distance AB is about 30 km. As per Newtonian notion of > >> absolute space and time, the mutual synchronization of the two clocks, > >> positioned at points A and B, will be retained in tact and this > >> synchronization can be referred as 'absolute synchronization'. But > >> according to SR, the mutual synchronization of the two clocks will > >> 'breakdown' during the shifting of one of the clocks from point A to > >> point B. > > > No, this is not what SR says. The clocks are still synchronized in the > > frame in which they are at rest. However, they are not synchronized in > > any frame where the two clocks are moving. > > You say that two clocks 'synchronized' in their rest frame, are 'not > synchronized' in any other frame where the clocks are moving. Let us > examine the plausibility of this statement. When two identical > precision atomic clocks are said to be 'synchronized' in their rest > frame, essentially their clock frequencies are supposed to have been > perfectly matched. > The matching of the two frequencies is a physical > phenomenon, controlled through their hardware circuitry and > sophisticated components. In SR, physical phenomena are defined in 4D space-time. They are all systems of events. They have no fixed defintion for all reference frames. > But when the same two clocks are 'viewed' by > different observers in different states of motion, they appear to be > out of synchronization. That is their clock frequencies 'appear' to be > mismatched by different amount to different observers in different > states of motion. > > However, creating a mismatch in the clock frequencies of two clocks is > a physical phenomenon controlled through their hardware circuitry and > sophisticated components. How do you think different observers in > different states of motion actually manage to physically influence the > hardware circuitry and sophisticated components of the two clocks to > create different amounts of mismatch in their frequencies, through the > mere act of 'viewing' from a distance? Do you think there is some > 'magic' involved in creating this phenomenon, which ordinary humans > cannot understand? The observers don't influence the system of events I referred to earlier. Each reference frame uses the operational definition of simultaneity and comes up with a different subset of events that thay consider to be simultaneous. So they disagree on whether the clocks are synchronous. Physical objects are systems of events in space-time. The objects viewed from a reference frame are projections into space and time, they are like shadows that change based on the angle of projection. > > GSS- Hide quoted text - > > - Show quoted text - You are a physical object that does not change as the angle of the sun changes. So how can your shadow be so different with different angles. That's what you are asking, you seem to think that is a paradox. ============================================ A sundial is a physical object and is a clock. A twin sundial goes on an accelerated relativistic journey and returns beside the sundial that remained at rest. The sundial that travelled is now younger than the sundial that remained. So how can its shadow be so different with different angles? That's what I am asking, I seem to think that is a paradox. -- Androcles.
From: PD on 7 Apr 2010 09:45 On Apr 7, 1:32 am, Tom Adams <tadams...(a)yahoo.com> wrote: > On Mar 11, 11:35 am, GSS <gurcharn_san...(a)yahoo.com> wrote: > > > > > As per Newtonian notion of absolute space and time, clocks can be > > synchronized in absolute terms such that identical precision atomic > > clocks located anywhere within the solar system and in any state of > > motion, will read the same time t1 when a standard master clock reads > > t1. This notion of absolute clock synchronization implies the notion > > of absolute simultaneity. > > > However, as per SR, spatial distance and time measurements have been > > rendered 'relative' and cannot be the same value for different > > observers in different states of motion. As per SR the notion of > > global 'absolute simultaneity' is fundamentally invalid for different > > observers in different states of motion. Therefore, the notion of > > global 'absolute clock synchronization' (in contrast to e- > > synchronization) is no longer valid in SR. > > > Since the term 'absolute clock synchronization' is often used in > > discussions, I would like to request some Relativity experts to kindly > > clarify the precise definition of absolute clock synchronization in > > SR. Kindly illustrate the procedure, through some 'thought experiment' > > or 'gedanken', to achieve absolute clock synchronization for all > > observers in different states of motion within our solar system. > > > Further, I also need some expert opinion on the following situation, > > involving clock synchronization. > > > Two identical precision atomic clocks are positioned side by side at > > point A on the surface of earth and mutually synchronized to ensure > > that > > (a) their clock rates or frequencies are exactly matched or > > synchronized > > (b) their instantaneous timing offsets are eliminated to ensure that a > > common trigger pulse yields the same timing reading t1 from both > > clocks. > > > Assuming the inherent drift of the two atomic clocks is identical and > > well within 100 ps per day, it can be demonstrated that while the two > > clocks remain side by side, their synchronization, after a period of > > one day, is retained at well within one ns accuracy. > > > Let us shift one of the synchronized atomic clocks to a position B > > such that distance AB is about 30 km. > > Stop right there. You are outside of the scope of SR. All acceleration > is outside the scope. SR cannot address your question. This is a mistake on two fronts. SR can and does routinely handle accelerations. Secondly, the resolution of the twin paradox is a straightforward implication of the fact that straight world lines have longer proper time integrated along the path, compared to bent world lines. This is something that can be seen in a spacetime diagram from basic SR. Penrose makes this point very succinctly, for example. > > Strictly speaking, the twin paradox is not part of SR since in > involves acceleration. The space-time paths that the twins take do > involve different elapsed times in a reference frame, but taking one > of the paths involves acceleration. > > > As per Newtonian notion of > > absolute space and time, the mutual synchronization of the two clocks, > > positioned at points A and B, will be retained in tact and this > > synchronization can be referred as 'absolute synchronization'. But > > according to SR, the mutual synchronization of the two clocks will > > 'breakdown' during the shifting of one of the clocks from point A to > > point B. Since 'after' shifting of one clock to point B on the surface > > of earth, there is no relative motion between the two clocks, their > > time rates or frequencies will again 'become' synchronized. Therefore, > > the only persisting effect of the 'synchronization breakdown' during > > shifting or repositioning of the two clocks, will be a motion induced > > constant time offset, say dT, in the instantaneous readings of the two > > clocks. > > > My question to the learned Relativity experts is: > > What is the order of magnitude of this 'relative motion induced' > > timing offset dT between the two clocks? > > Can it be precisely calculated in SR? Is it likely to be within a few > > nanoseconds or less? > > > Suppose we now shift the clock at point B to bring it back to point A, > > (with an identical speed and acceleration profile), will this timing > > offset dT now increase to 2.dT or reduce to zero? > > > I shall be thankful to the Relativity experts for their valuable > > opinions and clarifications. > > > GSS > >
From: Sue... on 7 Apr 2010 10:43 On Apr 7, 9:45 am, PD <thedraperfam...(a)gmail.com> wrote: > On Apr 7, 1:32 am, Tom Adams <tadams...(a)yahoo.com> wrote: > > > > > On Mar 11, 11:35 am, GSS <gurcharn_san...(a)yahoo.com> wrote: > > > > As per Newtonian notion of absolute space and time, clocks can be > > > synchronized in absolute terms such that identical precision atomic > > > clocks located anywhere within the solar system and in any state of > > > motion, will read the same time t1 when a standard master clock reads > > > t1. This notion of absolute clock synchronization implies the notion > > > of absolute simultaneity. > > > > However, as per SR, spatial distance and time measurements have been > > > rendered 'relative' and cannot be the same value for different > > > observers in different states of motion. As per SR the notion of > > > global 'absolute simultaneity' is fundamentally invalid for different > > > observers in different states of motion. Therefore, the notion of > > > global 'absolute clock synchronization' (in contrast to e- > > > synchronization) is no longer valid in SR. > > > > Since the term 'absolute clock synchronization' is often used in > > > discussions, I would like to request some Relativity experts to kindly > > > clarify the precise definition of absolute clock synchronization in > > > SR. Kindly illustrate the procedure, through some 'thought experiment' > > > or 'gedanken', to achieve absolute clock synchronization for all > > > observers in different states of motion within our solar system. > > > > Further, I also need some expert opinion on the following situation, > > > involving clock synchronization. > > > > Two identical precision atomic clocks are positioned side by side at > > > point A on the surface of earth and mutually synchronized to ensure > > > that > > > (a) their clock rates or frequencies are exactly matched or > > > synchronized > > > (b) their instantaneous timing offsets are eliminated to ensure that a > > > common trigger pulse yields the same timing reading t1 from both > > > clocks. > > > > Assuming the inherent drift of the two atomic clocks is identical and > > > well within 100 ps per day, it can be demonstrated that while the two > > > clocks remain side by side, their synchronization, after a period of > > > one day, is retained at well within one ns accuracy. > > > > Let us shift one of the synchronized atomic clocks to a position B > > > such that distance AB is about 30 km. > > > Stop right there. You are outside of the scope of SR. All acceleration > > is outside the scope. SR cannot address your question. > ================== > This is a mistake on two fronts. SR can and does routinely handle > accelerations. > Secondly, the resolution of the twin paradox is a straightforward > implication of the fact that straight world lines have longer proper > time integrated along the path, compared to bent world lines. This is > something that can be seen in a spacetime diagram from basic SR. > Penrose makes this point very succinctly, for example. Can you show us a four-vector proof that the final term of that exercise, "elapsed proper time" preserves the relevant symmetries? http://en.wikipedia.org/wiki/Noether%27s_theorem#Applications Sue... > > > > > Strictly speaking, the twin paradox is not part of SR since in > > involves acceleration. The space-time paths that the twins take do > > involve different elapsed times in a reference frame, but taking one > > of the paths involves acceleration. > > > > As per Newtonian notion of > > > absolute space and time, the mutual synchronization of the two clocks, > > > positioned at points A and B, will be retained in tact and this > > > synchronization can be referred as 'absolute synchronization'. But > > > according to SR, the mutual synchronization of the two clocks will > > > 'breakdown' during the shifting of one of the clocks from point A to > > > point B. Since 'after' shifting of one clock to point B on the surface > > > of earth, there is no relative motion between the two clocks, their > > > time rates or frequencies will again 'become' synchronized. Therefore, > > > the only persisting effect of the 'synchronization breakdown' during > > > shifting or repositioning of the two clocks, will be a motion induced > > > constant time offset, say dT, in the instantaneous readings of the two > > > clocks. > > > > My question to the learned Relativity experts is: > > > What is the order of magnitude of this 'relative motion induced' > > > timing offset dT between the two clocks? > > > Can it be precisely calculated in SR? Is it likely to be within a few > > > nanoseconds or less? > > > > Suppose we now shift the clock at point B to bring it back to point A, > > > (with an identical speed and acceleration profile), will this timing > > > offset dT now increase to 2.dT or reduce to zero? > > > > I shall be thankful to the Relativity experts for their valuable > > > opinions and clarifications. > > > > GSS > >
From: PD on 7 Apr 2010 14:36 On Apr 7, 9:43 am, "Sue..." <suzysewns...(a)yahoo.com.au> wrote: > On Apr 7, 9:45 am, PD <thedraperfam...(a)gmail.com> wrote: > > > > > On Apr 7, 1:32 am, Tom Adams <tadams...(a)yahoo.com> wrote: > > > > On Mar 11, 11:35 am, GSS <gurcharn_san...(a)yahoo.com> wrote: > > > > > As per Newtonian notion of absolute space and time, clocks can be > > > > synchronized in absolute terms such that identical precision atomic > > > > clocks located anywhere within the solar system and in any state of > > > > motion, will read the same time t1 when a standard master clock reads > > > > t1. This notion of absolute clock synchronization implies the notion > > > > of absolute simultaneity. > > > > > However, as per SR, spatial distance and time measurements have been > > > > rendered 'relative' and cannot be the same value for different > > > > observers in different states of motion. As per SR the notion of > > > > global 'absolute simultaneity' is fundamentally invalid for different > > > > observers in different states of motion. Therefore, the notion of > > > > global 'absolute clock synchronization' (in contrast to e- > > > > synchronization) is no longer valid in SR. > > > > > Since the term 'absolute clock synchronization' is often used in > > > > discussions, I would like to request some Relativity experts to kindly > > > > clarify the precise definition of absolute clock synchronization in > > > > SR. Kindly illustrate the procedure, through some 'thought experiment' > > > > or 'gedanken', to achieve absolute clock synchronization for all > > > > observers in different states of motion within our solar system. > > > > > Further, I also need some expert opinion on the following situation, > > > > involving clock synchronization. > > > > > Two identical precision atomic clocks are positioned side by side at > > > > point A on the surface of earth and mutually synchronized to ensure > > > > that > > > > (a) their clock rates or frequencies are exactly matched or > > > > synchronized > > > > (b) their instantaneous timing offsets are eliminated to ensure that a > > > > common trigger pulse yields the same timing reading t1 from both > > > > clocks. > > > > > Assuming the inherent drift of the two atomic clocks is identical and > > > > well within 100 ps per day, it can be demonstrated that while the two > > > > clocks remain side by side, their synchronization, after a period of > > > > one day, is retained at well within one ns accuracy. > > > > > Let us shift one of the synchronized atomic clocks to a position B > > > > such that distance AB is about 30 km. > > > > Stop right there. You are outside of the scope of SR. All acceleration > > > is outside the scope. SR cannot address your question. > > ================== > > > This is a mistake on two fronts. SR can and does routinely handle > > accelerations. > > Secondly, the resolution of the twin paradox is a straightforward > > implication of the fact that straight world lines have longer proper > > time integrated along the path, compared to bent world lines. This is > > something that can be seen in a spacetime diagram from basic SR. > > Penrose makes this point very succinctly, for example. > > Can you show us a four-vector proof that the final term > of that exercise, "elapsed proper time" > preserves the relevant symmetries?http://en.wikipedia.org/wiki/Noether%27s_theorem#Applications What "relevant symmetries" do you think a measurable physical quantity should preserve? Note your link talks about how *laws of physics* preserve certain symmetries, but measurable physical quantities are not laws of physics. I hope you don't get the two confused. > > Sue... > > > > > > Strictly speaking, the twin paradox is not part of SR since in > > > involves acceleration. The space-time paths that the twins take do > > > involve different elapsed times in a reference frame, but taking one > > > of the paths involves acceleration. > > > > > As per Newtonian notion of > > > > absolute space and time, the mutual synchronization of the two clocks, > > > > positioned at points A and B, will be retained in tact and this > > > > synchronization can be referred as 'absolute synchronization'. But > > > > according to SR, the mutual synchronization of the two clocks will > > > > 'breakdown' during the shifting of one of the clocks from point A to > > > > point B. Since 'after' shifting of one clock to point B on the surface > > > > of earth, there is no relative motion between the two clocks, their > > > > time rates or frequencies will again 'become' synchronized. Therefore, > > > > the only persisting effect of the 'synchronization breakdown' during > > > > shifting or repositioning of the two clocks, will be a motion induced > > > > constant time offset, say dT, in the instantaneous readings of the two > > > > clocks. > > > > > My question to the learned Relativity experts is: > > > > What is the order of magnitude of this 'relative motion induced' > > > > timing offset dT between the two clocks? > > > > Can it be precisely calculated in SR? Is it likely to be within a few > > > > nanoseconds or less? > > > > > Suppose we now shift the clock at point B to bring it back to point A, > > > > (with an identical speed and acceleration profile), will this timing > > > > offset dT now increase to 2.dT or reduce to zero? > > > > > I shall be thankful to the Relativity experts for their valuable > > > > opinions and clarifications. > > > > > GSS > >
From: Sue... on 7 Apr 2010 14:41
On Apr 7, 2:36 pm, PD <thedraperfam...(a)gmail.com> wrote: > On Apr 7, 9:43 am, "Sue..." <suzysewns...(a)yahoo.com.au> wrote: > > > > > On Apr 7, 9:45 am, PD <thedraperfam...(a)gmail.com> wrote: > > > > On Apr 7, 1:32 am, Tom Adams <tadams...(a)yahoo.com> wrote: > > > > > On Mar 11, 11:35 am, GSS <gurcharn_san...(a)yahoo.com> wrote: > > > > > > As per Newtonian notion of absolute space and time, clocks can be > > > > > synchronized in absolute terms such that identical precision atomic > > > > > clocks located anywhere within the solar system and in any state of > > > > > motion, will read the same time t1 when a standard master clock reads > > > > > t1. This notion of absolute clock synchronization implies the notion > > > > > of absolute simultaneity. > > > > > > However, as per SR, spatial distance and time measurements have been > > > > > rendered 'relative' and cannot be the same value for different > > > > > observers in different states of motion. As per SR the notion of > > > > > global 'absolute simultaneity' is fundamentally invalid for different > > > > > observers in different states of motion. Therefore, the notion of > > > > > global 'absolute clock synchronization' (in contrast to e- > > > > > synchronization) is no longer valid in SR. > > > > > > Since the term 'absolute clock synchronization' is often used in > > > > > discussions, I would like to request some Relativity experts to kindly > > > > > clarify the precise definition of absolute clock synchronization in > > > > > SR. Kindly illustrate the procedure, through some 'thought experiment' > > > > > or 'gedanken', to achieve absolute clock synchronization for all > > > > > observers in different states of motion within our solar system. > > > > > > Further, I also need some expert opinion on the following situation, > > > > > involving clock synchronization. > > > > > > Two identical precision atomic clocks are positioned side by side at > > > > > point A on the surface of earth and mutually synchronized to ensure > > > > > that > > > > > (a) their clock rates or frequencies are exactly matched or > > > > > synchronized > > > > > (b) their instantaneous timing offsets are eliminated to ensure that a > > > > > common trigger pulse yields the same timing reading t1 from both > > > > > clocks. > > > > > > Assuming the inherent drift of the two atomic clocks is identical and > > > > > well within 100 ps per day, it can be demonstrated that while the two > > > > > clocks remain side by side, their synchronization, after a period of > > > > > one day, is retained at well within one ns accuracy. > > > > > > Let us shift one of the synchronized atomic clocks to a position B > > > > > such that distance AB is about 30 km. > > > > > Stop right there. You are outside of the scope of SR. All acceleration > > > > is outside the scope. SR cannot address your question. > > > ================== > > > > This is a mistake on two fronts. SR can and does routinely handle > > > accelerations. > > > Secondly, the resolution of the twin paradox is a straightforward > > > implication of the fact that straight world lines have longer proper > > > time integrated along the path, compared to bent world lines. This is > > > something that can be seen in a spacetime diagram from basic SR. > > > Penrose makes this point very succinctly, for example. > > > Can you show us a four-vector proof that the final term > > of that exercise, "elapsed proper time" > > preserves the relevant symmetries?http://en.wikipedia.org/wiki/Noether%27s_theorem#Applications > > What "relevant symmetries" do you think a measurable physical quantity > should preserve? > Note your link talks about how *laws of physics* preserve certain > symmetries, but measurable physical quantities are not laws of > physics. I hope you don't get the two confused. > > > > > Sue... > > > > > Strictly speaking, the twin paradox is not part of SR since in > > > > involves acceleration. The space-time paths that the twins take do > > > > involve different elapsed times in a reference frame, but taking one > > > > of the paths involves acceleration. > > > > > > As per Newtonian notion of > > > > > absolute space and time, the mutual synchronization of the two clocks, > > > > > positioned at points A and B, will be retained in tact and this > > > > > synchronization can be referred as 'absolute synchronization'. But > > > > > according to SR, the mutual synchronization of the two clocks will > > > > > 'breakdown' during the shifting of one of the clocks from point A to > > > > > point B. Since 'after' shifting of one clock to point B on the surface > > > > > of earth, there is no relative motion between the two clocks, their > > > > > time rates or frequencies will again 'become' synchronized. Therefore, > > > > > the only persisting effect of the 'synchronization breakdown' during > > > > > shifting or repositioning of the two clocks, will be a motion induced > > > > > constant time offset, say dT, in the instantaneous readings of the two > > > > > clocks. > > > > > > My question to the learned Relativity experts is: > > > > > What is the order of magnitude of this 'relative motion induced' > > > > > timing offset dT between the two clocks? > > > > > Can it be precisely calculated in SR? Is it likely to be within a few > > > > > nanoseconds or less? > > > > > > Suppose we now shift the clock at point B to bring it back to point A, > > > > > (with an identical speed and acceleration profile), will this timing > > > > > offset dT now increase to 2.dT or reduce to zero? > > > > > > I shall be thankful to the Relativity experts for their valuable > > > > > opinions and clarifications. > > > > > > GSS > > |