Simultaneity of Relativity
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From: glird on 10 Nov 2009 11:33 On Nov 9, 1:00 pm, PD wrote: > On Nov 9, 11:19 am, glird wrote: > > On Oct 13, 6:36 pm, PD wrote: > > > Do you know the definition of simultaneity for two spatially separated events? > > > I do. Do You? If so, please write it out for us. > > < Here: If events occur at two spatially separated points, and a signal is sent with equal speed from each event to a single observer positioned midway between the two events, and the signals arrive at the observer at the same time, then this is what we mean when we say the two events are simultaneous. On the other hand, if events occur at two spatially separated events, and a signal is sent with equal speed from each event to a single observer positioned midway between the two events, and the signals arrive at the observer at different times, then this is what we mean when we say the two events are not simultaneous. > Please try again; this time without using signals or observers or clocks. > This is in fact the definition that Einstein used. In his 1905 STR paper he wrote: "If at the point A of space there is a clock, an observer at A can determine the time values events in the immediate proximity of A by finding the positions of the hands which are simultaneous with these events. If there is at the point B of space another clock in all respects resembling the one at A, it is possible for an observer at B to determine the time values of events in the immediate neighborhood of B. but it is not possible without further assumption to compare in respect of time, an event at A with an event at B. We have so far defined only an "A time" and a "B time". We have not defined a common "time" for A and B, for the latter cannot be defined at all unless we establish _by definition_ [his italics] that the "time" required for light to travel from A to B equals the "time" it requires to travel from B to A." He then gave an example that is similar to yours, though not identical: "Let a ray of light start at the "A time" t_A from A toward B, let it at the "B time" t_B be reflected at B in the direction of A, and arrive again at A at the "A time" t_A'." Temporarily ignoring the fact that A and B might be on an inertially moving system, he then said, "In accordance with definition the two clocks synchronize if t_B - t_A = t_A' - t_B." A few pages later, after treating a horizontal rod moving at v on X of a stationary system, he wrote, "We imagine further that at the two ends A and B of the [moving] rod, clocks are placed which synchronize with [have the same settings as] the clocks of the stationary system, that is to say that their indications correspond at any instant to the "time of the stationary system" at the places where they happen to be. These clocks are therefore "synchronous in the stationary system". "We imagine further that with each clock there is a co-moving observer, and that these observers apply to both clocks the criterion established in §1 for the synchronization of two clocks. Let a ray of light depart from A at the time tA, let it be reflected at B at the time tB, and reach A again at the time tA'. Taking into consideration the principle of the constancy of the velocity of light we find that tB-tA = rAB/(c-v) and tA'-tB = rAB/(c+v) where rAB denotes the length of the moving rod -- measured in the stationary system. Observers moving with the moving rod would thus find that the two clocks were not synchronous, while observers in the stationary system would declare the clocks to be synchronous." > Notice that there are no synchronized clocks anywhere. Perhaps not in his book to the layman, written decades later, but in his germinal paper there were. He said "at the two ends A and B of the [moving] rod, clocks are placed which synchronize with the clocks of the stationary system". He had previously postulated how those clocks were to be set, and had here said that the observers on the moving rod "apply to both clocks the criterion established in §1 for the synchronization of two clocks". However, instead of continuing on to show the next step required by the moving observers in order to "synchronize" clocks A and B - which would have been that observer B turns his clock's setting back by vx/c^2 seconds, where x = rAB as measured by them and v is the velocity of their rod in the "empty space" in which light propagates with a velocity c - he completely changed the subject, saying, "So we see that we cannot attach any absolute signification to the concept of simultaneity, but that two events which, viewed from a system of co-ordinates, are simultaneous, can no longer be looked upon as simultaneous events when envisaged from a system which is in motion relatively to that system." "Synchonous" and "simultaneity" are two entirely different things! Clocks are synchronous if they have identical settings. Events are simultaneous if they occur at the same instant; regardless of whether or not clocks even exist, or if they do, how they are set. For the record, PD and Inertial and mpc and Bruce, please be aware that I respect your intelligence and know where you are coming from. I too began my study of STR by reading Einstein and Infeld's book written to the layman. I too found places where I disagreed with their logic. It took a year or so for me to learn that my arguments -- especially those about his train-lightning gedanken -- though valid, had nothing to do with STR; that in order to understand the theory one has to go back to Einstein's actual 1905 paper. It took MANY years thereafter to understand it well enough to find an actual error in it; and then more, and more and then, one day, to suddenly discover that Einstein had revised the proof copy of his paper (in the summer of 1905) in order to include the Lorentz mathematics set forth in an earlier 1905 paper by Poincare'. Once I realized THAT, the roof fell in as I found place after place where his revisions contradicted themselves and/or are mathematically false. In the end I realized - and have written an article that PROVES it - that Einstein didn't understand Poincare's "Lorentz Transformation Equations" nor his own equations along the way to "deriving" them. Although much of this is presented in "A Flower for Einstein", the details are in a much shorter article called "The Missing Symbol", which proves via the fact that the symbol IS missing that Einstein really did revise his proof copy and, while doing so, didn't understand his own mathematics. glird
From: glird on 10 Nov 2009 12:24 On Nov 9, 5:49 pm, "Inertial" wrote: > "glird" wrote > << Note: As used in Einstein's tor, it means "If events occur at two spatially separated events, one at A and one at B, their "simultaneity" requires that two clocks - one at A and the other at B - that are set to mark rAB/c-v equal to rAB/c+v will mark them as happening at the same time. >> > > Where did you get that from? In particular, what is v? I got it from Einstein's 1905 paper, in which we find, x'/(c-v) + x'/(c+v), where x' = x-vt is the length of the moving rod as measured by the stationary system. In there, and as I used it, v is the speed of the moving rod wrt his "stationary system". > > It is obvious that since the clocks are NOT synchronous (other than via Einstein's novel definition of the word) the two events were NOT simultaneous either. > > > > Why do you think they are not synchronous? Let a rod moving at v = .6c be x' = rAB = .8 units long as measured by stationary system Z'. It is obvious that x'/(c-v) = .8/.4 = 2 is unequal to x'/(c+v)= .8/1.6 = .5. Since his moving clocks had been set to register the identical readings as those of this system, which have entirely different "times" than those required to measure the speed of light as the same in each direction, it is therefore obvious that clocks that are set to MEASURE 2 = .5 are not "synchronous" i.e. set to read the same "time" at the same instant. > How would YOU synchronise two clocks? I don't object to using Einstein's METHOD; I DO object to calling esynched clocks "synchronous" even if they aren't identically set per instant (i.e per "epoch"). glird
From: glird on 10 Nov 2009 12:36 On Nov 9, 6:17 pm, mpc755 wrote: > > The problem with simultaneity in Einstein's > train thought experiment [snip] The real problem is that his gedanken experiment has little to do with how the equations of STR actually work. Therefore these interminable arguments, as to whether or not they are valid, are useless. glird
From: PD on 10 Nov 2009 12:51 On Nov 10, 10:33 am, glird <gl...(a)aol.com> wrote: > On Nov 9, 1:00 pm, PD wrote:> On Nov 9, 11:19 am, glird wrote: > > > On Oct 13, 6:36 pm, PD wrote: > > > > Do you know the definition of simultaneity for two spatially separated events? > > > > I do. Do You? If so, please write it out for us. > > > < Here: If events occur at two spatially separated points, and a signal is sent with equal speed from each event to a single observer positioned midway between the two events, and the signals arrive at the observer at the same time, then this is what we mean when we say the two events are simultaneous. > > On the other hand, if events occur at two spatially separated events, > and a signal is sent with equal speed from each event to a single > observer positioned midway between the two events, and the signals > arrive at the observer at different times, then this is what we mean > when we say the two events are not simultaneous. > > > Please try again; this time without using signals or observers or > clocks. Why? This is what we MEAN when we say two events are simultaneous. > > > This is in fact the definition that Einstein used. > > In his 1905 STR paper he wrote: > "If at the point A of space there is a clock, an observer at A can > determine the time values events in the immediate proximity of A by > finding the positions of the hands which are simultaneous with these > events. If there is at the point B of space another clock in all > respects resembling the one at A, it is possible for an observer at B > to determine the time values of events in the immediate neighborhood > of B. but it is not possible without further assumption to compare in > respect of time, an event at A with an event at B. We have so far > defined only an "A time" and a "B time". We have not defined a common > "time" for A and B, for the latter cannot be defined at all unless we > establish _by definition_ [his italics] that the "time" required for > light to travel from A to B equals the "time" it requires to travel > from B to A." > He then gave an example that is similar to yours, though not > identical: > "Let a ray of light start at the "A time" t_A from A toward B, let it > at the "B time" t_B be reflected at B in the direction of A, and > arrive again at A at the "A time" t_A'." > Temporarily ignoring the fact that A and B might be on an inertially > moving system, he then said, The definition applies whether this is the case or not. And in fact, it is presumed that it IS! > "In accordance with definition the two clocks synchronize if > t_B - t_A = t_A' - t_B." OK, yes, you're right, Einstein used this definition to define how clocks get synchronized, and then he used this as a presumption for determining simultaneity of two spatially separated events. Do you need to see that the two definitions are equivalent? > A few pages later, after treating a horizontal rod moving at v on X of > a stationary system, he wrote, > "We imagine further that at the two ends A and B of the [moving] rod, > clocks are placed which synchronize > with [have the same settings as] > the clocks of the stationary system, that is to say that their > indications correspond at any instant to the "time of the stationary > system" at the places where they happen to be. These clocks are > therefore "synchronous in the stationary system". > "We imagine further that with each clock there is a co-moving > observer, and that these observers apply to both clocks the criterion > established in §1 for the synchronization of two clocks. Let a ray of > light depart from A at the time tA, let it be reflected at B at the > time tB, and reach A again at the time tA'. Taking into consideration > the principle of the constancy of the velocity of light we find that > tB-tA = rAB/(c-v) and tA'-tB = rAB/(c+v) > where rAB denotes the length of the moving rod -- measured in the > stationary system. Observers moving with the moving rod would thus > find that the two clocks were not synchronous, while observers in the > stationary system would declare the clocks to be synchronous." > > > Notice that there are no synchronized clocks anywhere. > > Perhaps not in his book to the layman, written decades later, but in > his germinal paper there were. He said "at the two ends A and B of > the [moving] rod, clocks are placed which synchronize with the clocks > of the stationary system". > He had previously postulated how those > clocks were to be set, and had here said that the observers on the > moving rod "apply to both clocks the criterion established in §1 for > the synchronization of two clocks". However, instead of continuing on > to show the next step required by the moving observers in order to > "synchronize" clocks A and B - which would have been that observer B > turns his clock's setting back by vx/c^2 seconds, where x = rAB as > measured by them and v is the velocity of their rod in the "empty > space" in which light propagates with a velocity c - he completely > changed the subject, saying, > "So we see that we cannot attach any absolute signification to the > concept of simultaneity, but that two events which, viewed from a > system of co-ordinates, are simultaneous, can no longer be looked upon > as simultaneous events when envisaged from a system which is in motion > relatively to that system." > "Synchonous" and "simultaneity" are two entirely different things! > Clocks are synchronous if they have identical settings. Events are > simultaneous if they occur at the same instant; regardless of whether > or not clocks even exist, or if they do, how they are set. > > For the record, PD and Inertial and mpc and Bruce, please be aware > that I respect your intelligence and know where you are > coming from. I too began my study of STR by reading Einstein and > Infeld's book written to the layman. I too found places where I > disagreed with their logic. On what basis? Disagreement should be on the basis of conflicting experimental data. > It took a year or so for me to learn that my arguments -- especially > those about his train-lightning gedanken -- though valid, had nothing > to do with STR; that in order to understand the theory one has to go > back to Einstein's actual 1905 paper. It took MANY years thereafter > to understand it well enough to find an actual error in it; and then > more, and more and then, one day, to suddenly discover that Einstein > had revised the proof copy of his paper (in the summer of 1905) in > order to include the Lorentz mathematics set forth in an earlier 1905 > paper by Poincare'. Once I realized THAT, the roof fell in as I found > place after place where his revisions contradicted themselves and/or > are mathematically false. > In the end I realized - and have written an article that PROVES it - > that Einstein didn't understand Poincare's "Lorentz Transformation > Equations" nor his own equations along the way to "deriving" them. > Although much of this is presented in "A Flower for Einstein", the > details are in a much shorter article called "The Missing Symbol", > which proves via the fact that the symbol IS missing that Einstein > really did revise his proof copy and, while doing so, didn't > understand his own mathematics. > > glird
From: mpc755 on 10 Nov 2009 13:14
On Nov 10, 12:36 pm, glird <gl...(a)aol.com> wrote: > On Nov 9, 6:17 pm, mpc755 wrote: > > > > > The problem with simultaneity in Einstein's > > train thought experiment [snip] > > The real problem is that his gedanken experiment has little to do > with how the equations of STR actually work. Therefore these > interminable arguments, as to whether or not they are valid, are > useless. > > glird Einstein's train thought experiment is fundamental to people's misunderstanding of how light behaves. It behaves as any other wave in a medium does and that is it travels relative to the medium it is propagating through. Einstein made the same mistake and that is why his train gedanken is so important. Light waves to not travel from the emission point and travel at 'c' from that point to the destination in the same frame of reference. In Einstein's train thought experiment, where the marks are made on the train and on the embankment are irrelevant as to how far the light travels to the Observers at M and M'. If the light travels from the marks made at A and B to M, then the aether is entrained and at rest relative to the embankment. If the light travels from the marks made at A' and B' to M', then the aether is entrained and at rest relative to the train. Since the embankment frame of reference and the train frame of reference both occupy the same space, and for this aether/space to be at rest for the train frame of reference and for the embankment frame of reference is physically impossible. This is what Einstein was trying to accomplish when he says the "idea of motion may not be applied to the [aether]." He is trying to have it both ways. Einstein needs the space/aether to be motionless relative to both frames of reference or his whole Relativity of Simultaneity is false. That is why he says: 'Ether and the Theory of Relativity by Albert Einstein' http://www-groups.dcs.st-and.ac.uk/~history/Extras/Einstein_ether.html "Now comes the anxious question:- Why must I in the theory distinguish the K system above all K' systems, which are physically equivalent to it in all respects, by assuming that the ether is at rest relatively to the K system? For the theoretician such an asymmetry in the theoretical structure, with no corresponding asymmetry in the system of experience, is intolerable. If we assume the ether to be at rest relatively to K, but in motion relatively to K', the physical equivalence of K and K' seems to me from the logical standpoint, not indeed downright incorrect, but nevertheless unacceptable." It is an anxious question because it requires Einstein to finish with "The idea of motion may not be applied to [aether]", which winds up undermining Relativity of Simultaneity and undermining measuring to the marks left by the lightning strikes and concluding anything about the simultaneity of the lightning strikes. Without knowing how the light travels from the lightning strikes to the Observers relative to the aether, you cannot conclude anything about when the lightning strike events occurred in either frame of reference. You can assume the light travels from A and B to M and the light from A' and B' to M', but since the idea of motion may not be applied to the aether/ space, that requires the shared three dimensional space to be at rest relative to train frame of reference and the embankment frame of reference, which is impossible. What you can conclude is due to the lightning strike events interaction with the aether and the fact the lightning strike event at A/A' is a single event, there is one light wave associated with the lightning strike and it is propagating outward at 'c' in all directions relative to the aether in the present. |