Notion of Absolute Clock Synchronization in SR
in [Relativity]
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From: Sue... on 6 Apr 2010 16:57 On Apr 6, 4:51 pm, PD <thedraperfam...(a)gmail.com> wrote: > On Apr 6, 3:37 pm, "Sue..." <suzysewns...(a)yahoo.com.au> wrote: > > > > > On Apr 6, 4:15 pm, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: > > > > GSS wrote: > > > > On Apr 6, 8:13 am, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: > > > >> GSS wrote: > > > >>> On Apr 3, 9:12 pm, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: > > > >>>> By saying "inertial frame" you imply the context is SR -- in SR one could set > > > >>>> the offsets of two clocks such that they are synchronized in any inertial frame > > > >>>> you choose. They would be synchronized with each other in that frame, but not > > > >>>> with coordinate clocks of the selected frame (these two would "tick at a > > > >>>> different rate" than those coordinate clocks). > > > >>> You have made a very important statement which I would like to repeat > > > >>> with some emphasis. "In SR one could set the *offsets* of two clocks > > > >>> such that they are *synchronized* in *any* inertial frame you choose. > > > >>> They would be synchronized with each other in *that* frame." > > > >>> Let us extend the analogy of two clocks fixed on earth's geoid to a > > > >>> million (or more) clocks fixed on earth's geoid. Let us synchronize > > > >>> all these clocks in ECI frame by synchronizing their time to UTC by > > > >>> using GPS service. In this state, each and every adjoining pair of > > > >>> clocks can be considered as mutually synchronized with zero time > > > >>> offset between them. > > > >> But, of course, each pair is synchronized in the ECI frame. The concept > > > >> "synchronized" is ALWAYS qualified with a frame. > > > > >>> Let us *adjust* the offsets of all these clocks such that they are now > > > >>> synchronized in BCRF. > > > >> It is not possible to make such an "adjustment". They all have essentially the > > > >> same gravitational potential, but they have different speeds relative to the > > > >> BCRF -- the earth both rotates and revolves around the sun. > > > > > As per your statement above, "They would be synchronized with each > > > > other in that [BCRF] frame, but not with coordinate clocks of the > > > > selected [BCRF] frame (these two would "tick at a different rate" than > > > > those coordinate clocks)." > > > > That was for two clocks AT REST IN SOME INERTIAL FRAME, being synchronized in > > > some other inertial frame. Here the clocks on the geoid are NOT at rest in ANY > > > inertial frame, and my "statement above" does not apply. > > > > Remember that the context in which statements are made is important, and you > > > cannot take a statement from one context, apply it in a different context, and > > > expect it to remain valid. > > > > > [...] we can always state that these clocks are > > > > *synchronized in proper time* > > > > There is no such thing [#]. As I said before, synchronization is ALWAYS > > > qualified with an inertial frame. You synchronized all those clocks in the ECI > > > frame, so they cannot be synchronized in the BCRF. > > > > [#] If there were, then the "twin paradox" would not occur. > > > It does. > > > > [This is getting overly repetitive; don't expect me to continue. You cannot > > > reasonably expect to learn much via "20 questions". Get a good textbook and STUDY.] > Gosh Tom, When half the returns for a Google search for the term "accumulated proper time" are posts by yourself or Daryl, one begins to give up looking for an adequate text on the subject. Ya can't blame folks for wanting to get it from straight from the horse's mouth. > > Tom said to get a good *textbook*, not a search return list. You do > know the difference and the relative value of each, don't you? If not, > then this perhaps accounts for much of your problem. "if you aren't taking flack, you aren't over the target" --Some lucky aviator > > > > Tom Roberts > >
From: BURT on 6 Apr 2010 17:46 On Apr 6, 10:04 am, GSS <gurcharn_san...(a)yahoo.com> wrote: > On Apr 6, 8:13 am, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: > > > > > GSS wrote: > > > On Apr 3, 9:12 pm, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: > >>> By saying "inertial frame" you imply the context is SR -- in SR one could set > >>> the offsets of two clocks such that they are synchronized in any inertial frame > >>> you choose. They would be synchronized with each other in that frame, but not > >>> with coordinate clocks of the selected frame (these two would "tick at a > >>> different rate" than those coordinate clocks). > > >> You have made a very important statement which I would like to repeat > >> with some emphasis. "In SR one could set the *offsets* of two clocks > >> such that they are *synchronized* in *any* inertial frame you choose. > >> They would be synchronized with each other in *that* frame." > > >> Let us extend the analogy of two clocks fixed on earth's geoid to a > >> million (or more) clocks fixed on earth's geoid. Let us synchronize > >> all these clocks in ECI frame by synchronizing their time to UTC by > >> using GPS service. In this state, each and every adjoining pair of > >> clocks can be considered as mutually synchronized with zero time > >> offset between them. > > > But, of course, each pair is synchronized in the ECI frame. The concept > > "synchronized" is ALWAYS qualified with a frame. > > >> Let us *adjust* the offsets of all these clocks such that they are now > >> synchronized in BCRF. > > > It is not possible to make such an "adjustment". They all have essentially the > > same gravitational potential, but they have different speeds relative to the > > BCRF -- the earth both rotates and revolves around the sun. > > As per your statement above, "They would be synchronized with each > other in that [BCRF] frame, but not with coordinate clocks of the > selected [BCRF] frame (these two would "tick at a different rate" than > those coordinate clocks)." Here we are not insisting on their > *synchronization* with the *coordinate clocks*, but only on the > *mutual synchronization* of all clocks located on earth's geoid. That > is, all these clocks when in *mutual synchronization* will display the > same instantaneous time (as UTC), but *that* time need not be the same > as the *corresponding* time on the coordinate clocks in BCRF. > > >> A little reflection will show that the required > >> offset will finally come out to be zero [...] > > > Even ignoring the above impossibility, this cannot possibly be true: both ECI > > and BCRF are inertial frames (in the local sense of GR, but here "local" > > includes all these clocks on the geoid). If these clocks were synchronized in > > both inertial frames, then the two frames must be the same. But they are > > manifestly not the same. > > Let me present the same problem in a slightly different form. > > As per Wikipedia, the coordinate times cannot be measured with real > physical clocks, but only computed from the proper-time readings of > real clocks with the aid of the time dilation relationship. Let us > therefore now consider a million (or more) identical atomic clocks > fixed on earth's geoid. Let us *synchronize* their *proper time* with > the UTC time by using GPS service. In this state, each and every > adjoining pair of clocks can be considered as mutually synchronized in > *proper time* with zero time offset between them. > > However, since the *proper time* of all these clocks cannot physically > change whether we consider them located in ECI frame or BCRF or the > Galactic reference frame, we can always state that these clocks are > *synchronized in proper time* which remains same in all inertial > reference frames. Of course for your relativity computations, you can > always transform these proper times to the corresponding *coordinate > times* of the selected reference frame. > > Do you agree? > > GSS- Hide quoted text - > > - Show quoted text - You must bring together two atomic clocks in the same strength of gravity and flow through space in order to synchronize them in the two universal time rates that slow down. The two times both have a fastest starting point at which they departed from in the very beginning and are now slower. Mitch Raemsch
From: Tom Adams on 7 Apr 2010 02:19 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.
From: Tom Adams on 7 Apr 2010 02:32 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. 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: Androcles on 7 Apr 2010 03:21
"Tom Adams" <tadamsmar(a)yahoo.com> wrote in message news:827aa470-d686-4b02-a943-ada1caebe193(a)g30g2000yqc.googlegroups.com... 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. 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. =========================================== Stop right there. Strictly speaking, the twin paradox is very much part of SR since it does NOT involve acceleration. The outbound journey is at velocity v and the inbound is at velocity -v, the path is a two-sided polygon. "If we assume that the result proved for a polygonal line is also valid for a continuously curved line, we arrive at this result: If one of two synchronous clocks at A is moved in a closed curve with constant velocity until it returns to A, the journey lasting t seconds, then by the clock which has remained at rest the travelled clock on its arrival at A will be 1/2 t v^2/c^2 second slow." -- Einstein, 1905, "On the Electrodynamics of Moving Bodies". Thence we conclude that clock B (having travelled and being younger than clock A) meets clock A before clock A meets clock B. The clock are twin clocks, and in real physics A meets B when B meets A. That's the paradox. http://www.merriam-webster.com/dictionary/paradox 2 a : a statement that is seemingly contradictory or opposed to common sense and yet is perhaps true b : a self-contradictory statement that at first seems true c : an argument that apparently derives self-contradictory conclusions by valid deduction from acceptable premises No need for any word salad about 'synchronized' or 'spacetime' or 'acceleration', the paradox is: B meets A before A meets B, contradictory to the acceptable premise that A meets B when B meets A. ================================================ > 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 |