Notion of Absolute Clock Synchronization in SR
in [Relativity]
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From: GSS on 12 Mar 2010 06:59 On Mar 11, 10:07 pm, Tom Roberts <tjrob...(a)sbcglobal.net> wrote: > GSS 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. > > But it conflicts with actual observations of the world we inhabit. Atomic clocks > on earth and in satellites do not remain synchronized. Effective clocks > intrinsic to elementary particles vary widely (factors of 10,000 or more in > rate) with their speed relative to the lab. > Elementary particles do not 'carry' any intrinsic clocks. It is a misinterpretation of the physical situation, that is carried too far! >> the notion of >> global 'absolute clock synchronization' (in contrast to e- >> synchronization) is no longer valid in SR. > > Yes. > >> I would like to request some Relativity experts to kindly >> clarify the precise definition of absolute clock synchronization in >> SR. > > There is no such definition, as "absolute clock synchronization" does not exist, > either in SR or in the world we inhabit. > But the definition of clock synchronization does exist. Is there no alternative method of clock synchronization other than e- 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. > > OK. Note that to achieve that accuracy requires multiple atomic clocks and a > good algorithm to construct a so-called "paper clock". > >> 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. 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. > > It is NOT true that "there is no relative motion between the two clocks" -- that > is valid ONLY relative to the rotating earth, which is not an inertial frame. It > is invariably wrong to attempt to make conclusions based on non-inertial frames > without careful considerations of the implications of their non-inertialness. > Relative to any inertial frame, these two clocks do have different velocities. Do you mean to imply that the clock rates or their frequencies will no longer match (even when both clocks are at rest on the surface of earth or say geoid) just because both A and B appear to have different 'velocities' in ECI or that the line segment AB is seen to be rotating in ECI? To elaborate this point, let us assume that clocks A and B are positioned along the equator and the frequency mismatch due to their rotation about the earth axis is dF. Synchronize a third clock with clock B and then shift to point B_1 on the equator such that BB_1 is equal to AB. Then the frequency mismatch between clocks B and B_1 will also be dF and the cumulative frequency difference between A and B_1 will be 2*dF. Similarly synchronize and position n more identical clocks at equidistant locations B_2, B_3 ... B_n along the equator, such that the last clock B_n comes back close to A and the cumulative frequency difference between A and B_n will be (n+1)*dF. However, since the two identical clocks B_n and A are positioned close by, they must be in synchronization and their frequency mismatch must be zero. This can be true only if dF is equal to zero. That means all clocks on the surface of earth, say geoid, must remain synchronized irrespective of their rotation about the earth axis. Do you agree? > The effect of their separation on their relative timing depends IN DETAIL on how > they were moved, what their relative positions are, and how they are compared. > No general conclusion can be made without specifying at least those details. > >> What is the order of magnitude of this 'relative motion induced' >> timing offset dT between the two clocks? > > As I said above, it depends on details you did not give. But for a mere 30 km > separation, assuming it is horizontal and not vertical, I would not expect it to > be large. > >> Can it be precisely calculated in SR? Is it likely to be within a few >> nanoseconds or less? > > Given sufficient information, it can be computed using GR. The gravitation of > the earth can be important here, in which case SR is inadequate. But if one > stipulates the two clocks both remain on earth's geoid, or at equal altitudes > from it, then gravitation can be neglected and SR is sufficient. > > With that stipulation, and assuming the 30 km transport is at automobile speeds > or less, I would not expect the clocks to differ by as much as a nanosecond. > IIRC actual tests of atomic clocks in automobiles showed about a nanosecond > difference after a full day at highway speeds. > > Certainly several hours sitting at the top of a mountain can > exceed that difference relative to a clock in the valley. > http://leapsecond.com/great2005/tour/ > (a small mountain only 5400 ft high, ~20 ns for a weekend) > >> 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? > > As I said, the details matter. It is also impossible to specify what dT is when > they are separated without specifying how the ambiguities of the comparison are > handled, and there is no unique and definitive way to do that. But upon > re-joining, the difference does not go to zero. > > Tom Roberts Thanks for your valuable opinion. GSS
From: GSS on 12 Mar 2010 07:21 On Mar 11, 10:26 pm, kenseto <kens...(a)erinet.com> wrote: > On Mar 11, 10:35 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. 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. > > Let's assume that when the B clock stop at 30 km away from A the A > clock shows a time interval of Delta(tA). Therefore Delta(tB) is > calculated as follows: > Delta(tB)=Delta(tA)/gamma_A > What this mean is that the B clock will lag behind the A clock by a > factor of [Delta(tA)-Delta(tB)] when it is stopped 30 km from A. > Kindly clarify what do you mean by the term gamma_A. We are shifting clock B with respect to A. Do you imply gamma_A to be a function of 'average' separation velocity of clock B with respect to A? Is it a standard method of computing the clock lag when two identical synchronized clocks are separated by slow transport? Tom Roberts does not seem to agree with this method. >> 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? > > The B clock will lag behind the A clock by a factor of 2.dT. > > Ken Seto > Thanks for your valuable opinion. GSS
From: Inertial on 12 Mar 2010 08:13 "GSS" <gurcharn_sandhu(a)yahoo.com> wrote in message news:f6d56542-6f1e-445e-b176-cecbeaa97437(a)q16g2000yqq.googlegroups.com... > On Mar 11, 10:07 pm, Tom Roberts <tjrob...(a)sbcglobal.net> wrote: >> GSS 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. >> >> But it conflicts with actual observations of the world we inhabit. Atomic >> clocks >> on earth and in satellites do not remain synchronized. Effective clocks >> intrinsic to elementary particles vary widely (factors of 10,000 or more >> in >> rate) with their speed relative to the lab. >> > Elementary particles do not 'carry' any intrinsic clocks. It is a > misinterpretation of the physical situation, that is carried too far! There are processes that happen with elementary particle that serve the purpose as a clock >>> the notion of >>> global 'absolute clock synchronization' (in contrast to e- >>> synchronization) is no longer valid in SR. >> >> Yes. >> >>> I would like to request some Relativity experts to kindly >>> clarify the precise definition of absolute clock synchronization in >>> SR. >> >> There is no such definition, as "absolute clock synchronization" does not >> exist, >> either in SR or in the world we inhabit. >> > But the definition of clock synchronization does exist. Yes it does .. but you cannot absolutely synchronize (clock sync is frame dependent) > Is there no > alternative method of clock synchronization other than e- > synchronization? E-synch is simply common sense. If you have tow fixed clocks, and a fixed speed signal between them, Then for the clocks to be in any way considered in sync, the timing for them must show the same time for the fixed speed signal to travel the same distance. If they don't, then no-one in his right mind would call clocks that didn't show this 'synchronized'. There are other methods of obtaining synchronized clocks .. eg place two clocks together, set them to the same time, then move them apart with the same (but opposite) speeds. It can be shown this results in a sync the same as e-synch
From: kenseto on 12 Mar 2010 08:26 On Mar 12, 7:21 am, GSS <gurcharn_san...(a)yahoo.com> wrote: > On Mar 11, 10:26 pm, kenseto <kens...(a)erinet.com> wrote: > > > > > On Mar 11, 10:35 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. 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. > > > Let's assume that when the B clock stop at 30 km away from A the A > > clock shows a time interval of Delta(tA). Therefore Delta(tB) is > > calculated as follows:average velocity > > Delta(tB)=Delta(tA)/gamma_A > > What this mean is that the B clock will lag behind the A clock by a > > factor of [Delta(tA)-Delta(tB)] when it is stopped 30 km from A. > > Kindly clarify what do you mean by the term gamma_A. Gamma_A is determined by A by measuring B's average velocity during its transit from A to 30 km away. >We are shifting > clock B with respect to A. Do you imply gamma_A to be a function of > 'average' separation velocity of clock B with respect to A? Yes. >Is it a > standard method of computing the clock lag when two identical > synchronized clocks are separated by slow transport? Tom Roberts does > not seem to agree with this method. Slow clock transport will minimize the lag between B and A. The best way to synch the two clocks is as follows: 1. separte A and B in the opposite directions with the same velocity and stop them simultaneously. 2. Then bring them back together with the same velocity. 3. These two clocks should remain synchronized. Ken Seto > > >> 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? > > > The B clock will lag behind the A clock by a factor of 2.dT. > > > Ken Seto > > Thanks for your valuable opinion. > > GSS- Hide quoted text - > > - Show quoted text -
From: GSS on 12 Mar 2010 08:31
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. 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? GSS |