Notion of Absolute Clock Synchronization in SR
in [Relativity]
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From: GSS on 12 Mar 2010 08:39 On Mar 12, 6:13 pm, "Inertial" <relativ...(a)rest.com> wrote: ...... > > 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 Kindly give me a link or reference where it is shown that the above synch method is the same as e-synch. GSS
From: Inertial on 12 Mar 2010 08:41 "GSS" <gurcharn_sandhu(a)yahoo.com> wrote in message news:d5784bd8-d01d-44ec-9e19-a39252b361de(a)b7g2000yqd.googlegroups.com... > 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 synchronization) is no longer valid in SR.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. Not in ALL other frames. > 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. Yes. > That is their clock frequencies 'appear' to be > mismatched by different amount to different observers in different > states of motion. No .. it means they show different times. it does not mean they are ticking at different rates > 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? Clearly you are the one not understanding what synching clocks means.
From: rotchm on 12 Mar 2010 09:29 > 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. Yes... But not only their frequencies (rate) but their "initial value". That initial value is the synchronization. >The matching of the two frequencies is a physical > phenomenon, controlled through their hardware circuitry and > sophisticated components. Yup... >But when the same two clocks are 'viewed' by > different observers in different states of motion, they appear to be > out of synchronization. Yup. The initial values of the observer's clocks ( his "time") no longer corresponds to the initial values of the observED (moving) clocks. >That is their clock frequencies 'appear' to be > mismatched by different amount to different observers in different > states of motion. No... For a particular observer observing the two (moving) clocks, those clocks have the same frequency; are ticking at the same rate. Its their initial value that no longer corresponds to the observer's clocks ( his "time"). > However, creating a mismatch in the clock frequencies of two clocks There is no mismatch in frequencies for any observer. > 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? They dont influence the frequencies not the hardware. That is why the frequencies remain matched. What they do change is *their* initial values of *their* own clocks (their "time"); They sych their own clocks, not the observed (moving) clocks. Their own synchronization ( initial values) will not correspond to the initial values of the two observed clocks.
From: harald on 12 Mar 2010 10:02 On Mar 12, 2:39 pm, GSS <gurcharn_san...(a)yahoo.com> wrote: > On Mar 12, 6:13 pm, "Inertial" <relativ...(a)rest.com> wrote: > ..... > > > > > 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 > > Kindly give me a link or reference where it is shown that the above > synch method is the same as e-synch. > > GSS You can easily show that to yourself by using the PoR: in the coordinate system in which the clocks were in rest, they will appear to slightly slow down by the same amount. Thus they must stay in sync with each other according to any standard clocks (e-synched) that they pass. Harald
From: harald on 12 Mar 2010 10:07
On Mar 12, 2:31 pm, 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. No. Essentially it means that their clock COUNTS have been matched, according to the sync convention. Clocks can have the same clock frequencies without being synchronized at all, and they can also be synchronized at a certain point in time (only at that time) without having the same frequency. Harald |