Joan-Claude van Dirk Helps to Trivialize Special Relativity
in [Relativity]
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From: cadwgan_gedrych on 17 Mar 2005 10:59 From: "" <cadwgan_gedrych(a)yahoo.com> Newsgroups: sci.physics.relativity Subject: Re: Joan-Claude van Dirk Helps to Trivialize Special Relativity Date: Thu, 17 Mar 2005 07:13:29 -0800 > > ... it is impossible for two clocks to both physically run > > slower than each other .... > > Sure it is. Thanks for agreeing. But why did you go on to argue? > > (or for two twins to both be younger than each other). > > That's not the same thing. > Prejudicial mental block at work. > > Note that "younger than" is a comparison made locally and locally only. > "Slower than" is a not necessarily a comparison made locally. In the part of my post which you cowardly snipped, I showed clearly that my clock comparison was LOCAL. Given this, I should not reply to the rest of you silly post, but I will because one of my overall goals here is to help folks to understand special relativity. > There is no such thing as a "physical rod length". Rod length is > strictly the result of an observer-dependent procedure. Hog wash. Every rod and all other physical objects have a given number of atoms which have definite physical shapes, and these two things determine an object's physical length. You were talking about measured rod length; I was talking about the atomic and intrinsic length. There is a world of difference between the two. Try to unconfuse yourself if you can. > "Physical clock rhythms", "physical rod lengths", and "physical > masses" are poorly defined terms. > > Let's start with length. Define the length of a rod, or at least how > you would find it. I defined physical rod length above. And here is how you can correctly measure it: In an inertial frame, place clocks at points (0,0,0) and (100,0,0). At point (50,0,0), simultaneously send out two inertial objects whose speeds wrt the clock frame are equal. (Note that equality does not require quantification, but only qualitative comparison.) (Also note that two things which are at the same point can be started absolutely simultaneously.) Given this, the two clocks must be started absolutely simultaneously by the objects. Then we can use the clocks to measure light's passing speed. This, in turn, will tell us how fast we are moving in relation to light. For example, we could be moving at 60% light speed. If so, then a standard ruler on board the clock frame will be physically contracted by 20% so that its actual, physical, atomic, intrinsic length is not 1 unit, but is .8 unit. Why don't you tell us how SR can correctly measure the length of even a rod that is at rest wrt our frame? In fact, why don't you tell us how SR can even correctly measure the one-way, two-clock speed of anything? In order to do that, here are the hurdles which SR must overcome: [1] SR must prove that its clocks are correctly synchronized. [2] SR must prove that its clocks are not physically slowed. [3] SR must prove that its rulers are not physically contracted. Be sure to let us all know when you have your answer. I will not be holding my breath. And here is a simple definition of "physical clock rhythm": Given: A simple sort of atomic clock where exactly one atomic transition or vibration = 1 time unit. Given this, it is perfectly clear that if two clocks register different numbers of atomic vibrations between the same two events, we know that the clocks' intrinsic rhythms differ. Given this, it is easy to see that no outside, passing frame(s) can control or have any effect upon a clock's intrinsic atomic rhythm. That is, a clock's intrinsic rhythm is absolute, not relative. A given clock will record one and only one time between any two given events, and this unique time is in no way dependent upon the point of view of observers in some passing frame or frames. Got it? [snip] ? > This asynchronousness is easily proved, as follows: > > Given two events, we know that they must physically occur > > either absolutely simultaneously or not, > > And how do you know that? This is not only not obvious, but also > incorrect. Hogwash, again. As you should know, events are observer-independent, and events must occur either truly simultaneously or not. If you believe otherwise, then tell us the alternative. Again, you are talking about measuring things (events), not the things themselves. > Define simultaneity and how you would determine whether two > things are simultaneous. This was done above, but here is another example: It is a simple fact that clocks can have absolutely different velocities. (Indeed, only clocks which are always relatively at rest will have absolutely identical velocities.) In other words, clocks can move differently through space. Let's assume, as Einstein seems to do, that clocks moving at absolutely different speeds do not have absolutely different intrinsic rhythms. Now, we can start two touching clocks on zero so that they are now absolutely synchronous (by simple direct observation and per all observers in all frames). We now slowly move one clock to a different location, so that acceleration is negligible. The clocks, according to our Einsteinian-based assumption, should still be absolutely synchronous. Thus, we can use the clocks to determine whether two things are simultaneous. Got it? > > but Einstein's > > clocks in various frames will say that two given events > > occurred BOTH simultaneously and nonsimultaneously, which, > > as we just noted, is simply physically impossible, and, a > > picture of this situation quickly shows that Einstein's > > clocks cannot be correctly synchronized in any frame but > > one: > > > > left clock right clock > > [3]-------Frame A-------[3] > > E1 E2 > > [3]-------Frame B-------[4] > > left clock right clock > > > > If events E1 and E2 happened to occur absolutely simultaneously, > > That's a big IF. No two events EVER happen *absolutely* simultaneously. > Don't misunderstand me. I'm not implying this is a matter of > imprecision. Events can be simultaneous, but that simultaneity is not > absolute, true, physical, or inherent. > You completely missed the point, as usual. It matters not how the events occurred. All that matters is the fact that they cannot occur in more than one way. If you foolishly believe otherwise, then explain. Since events, as I noted above, are observer-independent (as even Einstein would admit), the way they occur is also observer- independent. However, in SR, as I noted, observers in different frames will find different occurrence orders and times for the SAME two events. This -- see my picture above -- proves that Einstein's clocks cannot be related the same in any two frames. Therefore, even if one of Einstein's frames by sheer accident has absolutely synchronous clocks, no other Einsteinian frame can have absolutely synchronous clocks. > > then only one Einsteinian frame's clocks will say this, but all > > other such frames' clocks will say that the events occurred > > nonsimultaneously; so, as the picture shows, these other frames' > > clocks will be absolutely asynchronous. > > > > Having found the immediate answer to the question which Dirk > > claimed that no one could answer, we can easily go even further, > > and answer the question Why are Einstein's clocks asynchronous? > > > > It's because Einstein ignores the differences in frame velocities > > when he uses light signals to "synchronize" his clocks. For > > example, whereas Frame A may move toward a given light signal, > > Frame B may move away from said signal, so the clocks in these > > two frames cannot possibly be set the same way using said signal > > as long as one uses Einstein's definition of "synchronization," > > You haven't learned how Einstein insists synchronization be done. > Synchronizing clocks involves clocks, sources and receivers that are > all stationary, not moving, in that frame. You don't understand the basic facts about light. Since light is source-independent, ONE light signal can be used to E-synch the clocks of ALL frames. > Summarizing your faulty assumptions: > 1. That duration is a physical, absolute, inherent property. Apparently, you have not heard of proper time. This is an absolute (or observer-independent) time. Apparently, you are not aware that during your lifetime, you will have a single number of heartbeats. This single number is the absolute (or observer-independent) duration of your life. Also, refer to my definition of intrinsic or absolute clock time, given above. > 2. That length is a physical, absolute, inherent property. See my above. > 3. That simultaneity is a physical, absolute, inherent property. See my above.
From: PD on 17 Mar 2005 11:03 Harry wrote: > "PD" <pdraper(a)yahoo.com> wrote in message > news:1111004650.489408.138750(a)l41g2000cwc.googlegroups.com... > > > SNIP > > > > This asynchronousness is easily proved, as follows: > > > Given two events, we know that they must physically occur > > > either absolutely simultaneously or not, > > > > And how do you know that? This is not only not obvious, but also > > incorrect. > > Define simultaneity and how you would determine whether two things are > > simultaneous. > > It depends on one's starting assumptions. > In science (natural philosophy) the starting assumption used to be that one > single observervation independent reality exists. > Based on that assumption, two events can only be either simultaneous *or* > not simultaneous. The difficulty with this, SR holds, is: 1. Given two observers in relative motion, there will be a disagreement as to whether two events are simultaneous or not. There is no physical way to determine which observer is correct. 2. Given a set of observers all in relative motion and three events A, B, C, it will be the case that A and B will be simultaneous to only one observer among the set of observers, and B and C will be simultaneous to only one observer among the set observers, and these two observers will not necessarily be the same observer. The association of simultaneity with the observer-independent reality (i.e. absolute simultaneity) would imply that one of these choices is correct, which would mean there would have to be a way to physically distinguish that choice as being correct (and the other incorrect). 3. No test has been able to distinguish which choice is correct. PD > If OTOH one adopts the pov that somehow everyone establishes his/her own > reality -- effectively everyone's personal universe -- then indeed everyone > can decide on his/her own truth. "Physical" can then be put in the domain of > films such as Matrix, it's just personal perception. > > Harald
From: cadwgan_gedrych on 17 Mar 2005 11:29 Dirk Van de moortel wrote: > <cadwgan_gedrych(a)yahoo.com> wrote in message news:1110999070.611006.230190(a)l41g2000cwc.googlegroups.com... [snip] > > This proves that relativity's time dilation cannot pertain > > to physical clock rhythms (or to any other processes > > involving physical time or physical aging) > Time dilation pertains to physical measurements. > Physics pertains to physical measurements. > But we told you this before. The 3-clock "paradox" does not pertain to mere measurements. Its two directly-compared clocks show different times after being synchronous. But of course, this is why you cowardly snipped my 3-clock "paradox" example. You can run, but you can't hide, from the truth. > > because it is impossible for two clocks to both > > physically run slower than each other (or for two > > twins to both be younger than each other). > When we look at each other through gaps between our > fingers, we each find that the other one is smaller. That > doesn't say anything about our physical lengths. It says > something about the way we measured something. > But we told you this before. I repeat: The 3-clock "paradox" does not pertain to mere measurements. Its two directly-compared clocks show different times after being synchronous. But of course, this is why you cowardly snipped my 3-clock "paradox" example. You can run, but you can't hide, from the truth. > The twin sitation in the so-called paradox is not symmetric. That is exactly why I used the NO-accelerations 3-clock case. (It eliminates the asymmetry of only one twin accelerating.)
From: Harry on 17 Mar 2005 12:09 "PD" <pdraper(a)yahoo.com> wrote in message news:1111075406.192734.177260(a)g14g2000cwa.googlegroups.com... > Harry wrote: > > "PD" <pdraper(a)yahoo.com> wrote in message > > news:1111004650.489408.138750(a)l41g2000cwc.googlegroups.com... > > > > > SNIP > > > > > > This asynchronousness is easily proved, as follows: > > > > Given two events, we know that they must physically occur > > > > either absolutely simultaneously or not, > > > > > > And how do you know that? This is not only not obvious, but also > > > incorrect. > > > Define simultaneity and how you would determine whether two things > are > > > simultaneous. > > > > It depends on one's starting assumptions. > > In science (natural philosophy) the starting assumption used to be > that one > > single observervation independent reality exists. > > Based on that assumption, two events can only be either simultaneous > *or* > > not simultaneous. > > The difficulty with this, SR holds, is: > 1. Given two observers in relative motion, there will be a disagreement > as to whether two events are simultaneous or not. There is no physical > way to determine which observer is correct. That is not a problem for SRT, just as it doesn't matter for Newtonian mechanics not to know which observer is moving, and as it doesn't matter for electronics not to know which conductor is at zero potential. One may just assume whatever and it works. > 2. Given a set of observers all in relative motion and three events A, > B, C, it will be the case that A and B will be simultaneous to only one > observer among the set of observers, and B and C will be simultaneous > to only one observer among the set observers, and these two observers > will not necessarily be the same observer. The association of > simultaneity with the observer-independent reality (i.e. absolute > simultaneity) would imply that one of these choices is correct, Exactly, > which > would mean there would have to be a way to physically distinguish that > choice as being correct (and the other incorrect). Certainly not, that's an erroneous argument. Why on earth would one think that whatever exist must be measurable in principle, or worse, that it must be measurable with our existing instruments? > 3. No test has been able to distinguish which choice is correct. Correct, AFAIK. > > If OTOH one adopts the pov that somehow everyone establishes his/her > own > > reality -- effectively everyone's personal universe -- then indeed > everyone > > can decide on his/her own truth. "Physical" can then be put in the > domain of films such as Matrix, it's just personal perception. > > > > Harald >
From: PD on 17 Mar 2005 12:43
Harry wrote: > "PD" <pdraper(a)yahoo.com> wrote in message > news:1111075406.192734.177260(a)g14g2000cwa.googlegroups.com... > > Harry wrote: > > > "PD" <pdraper(a)yahoo.com> wrote in message > > > news:1111004650.489408.138750(a)l41g2000cwc.googlegroups.com... > > > > > > > SNIP > > > > > > > > This asynchronousness is easily proved, as follows: > > > > > Given two events, we know that they must physically occur > > > > > either absolutely simultaneously or not, > > > > > > > > And how do you know that? This is not only not obvious, but also > > > > incorrect. > > > > Define simultaneity and how you would determine whether two things > > are > > > > simultaneous. > > > > > > It depends on one's starting assumptions. > > > In science (natural philosophy) the starting assumption used to be > > that one > > > single observervation independent reality exists. > > > Based on that assumption, two events can only be either simultaneous > > *or* > > > not simultaneous. > > > > The difficulty with this, SR holds, is: > > 1. Given two observers in relative motion, there will be a disagreement > > as to whether two events are simultaneous or not. There is no physical > > way to determine which observer is correct. > > That is not a problem for SRT, just as it doesn't matter for Newtonian > mechanics not to know which observer is moving, and as it doesn't matter for > electronics not to know which conductor is at zero potential. One may just > assume whatever and it works. There is a difference. In the other cases that you mentioned, the physical laws are quite explicit in depending not on the absolute scale of those quantities but on the *difference* only. Acceleration (which enters into the dynamics) does not depend on the velocity of the reference frame; potential *difference* does not depend on which point is chosen to be zero. In the case of simultaneity, critics of SR often assert that simultaneity MUST be relied on as an absolute property. The fact is, as SR points out, there is nothing in physical law that demands simultaneity being an absolute property. > > > 2. Given a set of observers all in relative motion and three events A, > > B, C, it will be the case that A and B will be simultaneous to only one > > observer among the set of observers, and B and C will be simultaneous > > to only one observer among the set observers, and these two observers > > will not necessarily be the same observer. The association of > > simultaneity with the observer-independent reality (i.e. absolute > > simultaneity) would imply that one of these choices is correct, > > Exactly, > > > which > > would mean there would have to be a way to physically distinguish that > > choice as being correct (and the other incorrect). > > Certainly not, that's an erroneous argument. Why on earth would one think > that whatever exist must be measurable in principle, or worse, that it must > be measurable with our existing instruments? I don't think anyone worries too much about whether it is measurable with existing instruments. Certainly, Einstein proposed some measurements to test the theory that involved experimental apparatus not yet developed, but he DID suggest some ways to test it *in principle*. SR does NOT say that simultaneity is in principle a verifiable property, but we don't have the instruments to detect it yet. As to whether something can exist but be unmeasurable in principle, even indirectly, this becomes a subject of metaphysics, not physics. Personally, I feel strongly that physics makes a representation of the universe, but that there are limitations to our representation that have to do with semantics (particle-wave duality, for example) or intractibility (perturbation theory and renormalization), for example. To that extent, there may well be a reality that is outside our understanding even in principle, but that lies outside physics. Personally, I also have faith (and I mean that term) that nature does not exhibit things that are inherently unmeasurable or undetectable. For a long time, folks were sure that neutrinos were massless and left-handed. As such, right-handed neutrinos would interact with *nothing* in the universe and would, by their very nature, be undetectable and would have no implications for the rest of reality. So it was perhaps interesting to ask the question whether right-handed neutrinos could exist *anyway*. The dominant thinking has been, of course they *could*, but they are not part of physics. For physicists, massless, right-handed neutrinos simply do not exist. This is clearly based on a faith that the universe does not feel compelled to produce "useless" particles. There are some ether theories that are identical in saying that the ether is present but it is by nature completely undetectable, even in principle. Such theories are generally rejected on the principle of simplicity. Given two experimentally indistinguishable models A and B, where B involves something that A doesn't but whose existence cannot be verified, the choice is usually A, and that's a defendable choice. Similarly here, if absolute simultaneity is a property of two events but is completely and by nature undetectable, even in principle, then for the purpose of physics, absolute simultaneity is not a needed concept. > > > 3. No test has been able to distinguish which choice is correct. > > Correct, AFAIK. > > > > If OTOH one adopts the pov that somehow everyone establishes his/her > > own > > > reality -- effectively everyone's personal universe -- then indeed > > everyone > > > can decide on his/her own truth. "Physical" can then be put in the > > domain of films such as Matrix, it's just personal perception. > > > > > > Harald > > |