Notion of Absolute Clock Synchronization in SR
in [Relativity]
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From: PD on 12 Mar 2010 11:10 On Mar 12, 7:31 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 synchronization) is no longer valid in SR.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. 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. I'm not sure how you would distinguish what the clocks "are" from what they "appear" to be. You read the clocks and see what they say. This tells you what they are. It would be foolish to read a clock and presume that what it reads is not what it really is. > > However, creating a mismatch in the clock frequencies of two clocks is > a physical phenomenon controlled through their hardware circuitry and > sophisticated components. No, this is a common mistake. The presumption is that if clocks read differently, then there must have been something that physically interacted with the clocks to alter their mechanism. This is not the case. > 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? It is not magic and it is straightforward for humans to understand. It is important, though, that the human being able to entertain a new notion other than what he is used to, for nature is broader and richer than what we once thought it was. Most importantly, one has first to recognize that if it is measured, it is real. This is not something whose plausibility is in question. If it is seen, then OF COURSE it is plausible, because it is something that actually happens. Once you get your head wrapped around that, THEN you can start figuring out how it happens. The mistake that some people make is not believing that something happens until you can understand how it can happen. In physics, the observation of what really does happen sometimes precedes a good understanding of how that is possible. PD
From: Tom Roberts on 12 Mar 2010 11:13 harald wrote: > [clocks] can also be > synchronized at a certain point in time (only at that time) without > having the same frequency. We do not call this "synchronized". The whole point of synchronizing clocks is so they can be used together to make related measurements of something. Two clocks that indicate the same time only once cannot be used together. After all, a stopped "clock" is correct twice a day! (In physics, we don't call such a device a "clock"; it is merely a clockface with unmoving hands.) Tom Roberts
From: GSS on 12 Mar 2010 12:02 On Mar 12, 7:29 pm, rotchm <rot...(a)gmail.com> wrote: >> 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. > This is an important point. I hope all other Relativity experts agree with your contention. >>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. > Does it mean that the 'initial values' of two identical atomic clocks A and B, if matched in their rest frame, will remain mutually matched even in moving observer's frame, even though these 'initial values' will no longer match with the initial values of the observer's clocks ( his "time")? >>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"). > Again this is an important point. May I request Tom Roberts to confirm if this contention is true as per SR? > > 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 don't 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. Thanks for your valuable clarification. I only hope this is true as per SR. GSS
From: rotchm on 12 Mar 2010 14:00 On Mar 12, 12:02 pm, GSS <gurcharn_san...(a)yahoo.com> wrote: > On Mar 12, 7:29 pm, rotchm <rot...(a)gmail.com> wrote:>> 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. > > This is an important point. > I hope all other Relativity experts agree with your contention. "experts" is relative. Many "experts" are self proclaimed. > > Yup. The initial values of the observer's clocks ( his "time") no > > longer corresponds to the initial values of the observED (moving) > > clocks. > > Does it mean that the 'initial values' of two identical atomic clocks > A and B, if matched in their rest frame, will remain mutually matched > even in moving observer's frame, even though these 'initial values' > will no longer match with the initial values of the observer's clocks > ( his "time")? Let C1 and C2 be the two (moving) clocks which havee ben synched in their mutual frame. Let them start to tick/count with a value of zero. The initial values are zero. Now let an (O)bserver move wrt these two clocks. The O has synched *his* own clocks; has set up 'time' in his frame. As C1 initially coincides with O's clock K1 ( what ever clock it is), k1 indicates something... say zero too. But as C2 ( as it indicates a value of zero) coincides with O's clock K2, K2 will not indicate zero: C1_____C2_____ ... frame with sped v. K1_____K2_____ ... C1=0, K1 = wlg 0. There exist a clock K2 that coincides with C2 as this C2 indicates zero. The value on K2 at this coincidence will not be zero. IOW, time in C and K are not in synch. > > >>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"). > > Again this is an important point. > May I request Tom Roberts to confirm if this contention is true as per > SR? Note that all observers ( C's and K's ) agree that C1 and C2 started with the value of zero. Its the relation of these zero's with the observers clocks ( K's) which is different. Take care on what is meant here by 'initial values' ...
From: Da Do Ron Ron on 12 Mar 2010 14:51
On Mar 11, 5:26 pm, Tom Roberts <tjrob...(a)sbcglobal.net> wrote: > Da Do Ron Ron wrote: > > > Also, please note that Dr. Smolin points out that Quantum Physics > > uses absolute time. > >http://www.fortunecity.com/emachines/e11/86/whattime.html > > "And quantum theory, which was originally developed to explain > > the properties of atoms and molecules, took over completely > > Newton's notion of an absolute ideal time." > > Yes, quantum mechanics uses an absolute time coordinate. But we also know that > QM is wrong. Quantum field theories such as the standard model are much better > models of the world we inhabit, and they use no "absolute time" -- they are > Lorentz invariant. > > Tom Roberts Smolin said this: "So, in theoretical physics, we have at present not one theory of nature but two theories: relativity and quantum mechanics, and they are based on two different notions of time." "at present" = "currently" ~~RA~~ |