Joan-Claude van Dirk Helps to Trivialize Special Relativity
in [Relativity]
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From: cadwgan_gedrych on 18 Mar 2005 09:11 Daryl McCullough wrote: > cadwgan_gedrych(a)yahoo.com says... > > >Here is an example of its blatant circularity/triviality: > > > >SR sez: > >"If we manually force all clocks in all frames to > >obtain the same one-way light speed, then, by George, > >all clocks in all frames will obtain the same one-way > >light speed." > > > >Can you, even your blinded eyes, see the silly circularity? > > SR says more than that---it says that *every* experiment done > in the "moving" frame, using clocks synchronized Einstein's way, > produces the same results as the same experiment performed in > the "stationary" frame. > > In particular, consider the following experiment: Foul. Slowly transported clocks are not E-synched. (His definition does not mention moving clocks, and uses light signals.) > In the moving frame, we synchronize a clock at > rest at position x'=0 and a clock at rest at position > x'=L using light signals. Then we slowly (at a speed > much slower than the speed of light) move the > first clock from its position x'=0 until it is > side-by-side with the clock at postion x'=L. Then > we compare times. The prediction of SR is that > the clocks will continue to be in synch. Wrong. SR does not pertain to actual or physical clock slowing, and yet that is what would happen during clock transport. If you believe otherwise, then you must prove that clocks moving at different speeds do not have different intrinsic rhythms. > That is a nontrivial empirical prediction. More generally, > SR predicts that any clock transported along any path > will show an elapsed time of > > tau = Integral of square-root(1 - v(t)^2/c^2) dt > > where v(t) is the instantaneous velocity of the clock at time t. > That doesn't follow circularly from the definition of Einstein > synchronization. Wrong again. As I said, SR makes zero predictions about intrinsic clock rhythms. The only way such rhythms are within SR is via Einstein's explicit (see 1905 paper) and mere acceptance of the MMx null result _up front_, prior to SR. No prediction, just acceptance of an old (1887) experimental result. [key search words in 1905 paper: "in agreement with experience"] > Your basic point is correct---some predictions of a theory > are not true predictions, they are more like conventions; > Einstein's synchronization convention is such a convention > (that's why it's called a "convention"). In order to extract > the physical content of a theory, it is helpful to rephrase > predictions so that the result is independent of any such > conventions. The constancy of the speed of light is *not* > a physical prediction, unless you operationally define how > you are measuring it. Partly right; partly wrong. Your implication that SR does make some scientific predictions is simply incorrect, but at least you agree that E-synch is indeed a mere convention or definition - given entirely by man, and not by nature (or experiment). You are also incorrect regarding _predicting_ light's one-way speed whilst at the same time _giving the result in advance_ (via some definition of synchronization). For example, as I have already mentioned, if one forces clocks (via Einstein's definition) to obtain one-way invariance, then, by George, one will obtain one-way invariance. This does NOT involve a prediction, as should be obvious, and no other such scenario can involve a prediction, contrary to your above. Here again is my specific complaint about special relativity: ```````````````````````````````````````````````````````````````` It makes exactly zero physical predictions which are nontrivial, noncircular and/or correct, or so it is not a scientific theory. ```````````````````````````````````````````````````````````````` And here is a related complaint about SR: ```````````````````````````````````````````````````````````````` Einstein based SR on his firm belief that it pertained to and directly addressed a LAW of physics, namely, the one-way light speed "law"; however, as we have seen, there can be no natural (or experimental) law in the one-way case because the result will always be given in advance via some definition of clock synchronization, which of course CONTROLS light's one-way speed in the specific case of two same-frame (non-moving) clocks, the ONLY case to which SR could possibly pertain because all others involve possible intrinsic clock slowing due to different clock speeds through space, with both of these concepts lying _outside_ of SR, as was explained above. `````````````````````````````````````````````````````````````````` Finally, note that since there is no possible LAW in the one-way, two-same-frame clock light speed case, there can be no scientific hypothesis, guess, hunch, prediction, supposition, or assumption in this case, so there can be no scientific theory, so SR is not a scientific theory. (It is nothing at all but an incorrect definition of clock "synchronization," which does not correctly synchronize clocks in any frame but one.)
From: PD on 18 Mar 2005 10:02 Harry wrote: > "PD" <pdraper(a)yahoo.com> wrote in message > news:1111081433.010734.73380(a)o13g2000cwo.googlegroups.com... > > 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. > > The physical laws describe relative measures of speed and potential. Which > does not prevent models in which they are absolute, but measured relatively. > Your above "difficulty" only exist for certain philosophers, because of > their personal taste. It is not so much a matter of taste as it is of lack of necessity. A model that invokes absolute quantities but makes no use of them is needlessly complicated. Moreover, invoking absolute quantities obscures physical insight that comes from seeing that it is only the relative quantities that are physically important. After all, relativity is called relativity precisely because the power and insight that the relative nature of these quantities provides. > > > > > 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*. > > My objection was against your argument that all that exist must be > measurable by us, as if we are gods who can measure all that exists. Then allow me to amend to say that all we can *model* must be measurable by us, and what we can model is the business of physics. > > > 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. > > Exactly. You made a metaphysical claim about physics, with which I > disagreed. > > > 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. > > Hmm, that is not physics but philosophy. Physics is neutral about such > issues - and physicists the same. Perhaps you'd like to think so (or perhaps not -- see below). > > > 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. > > OK, we agree that that is an optionally choice. OTOH, what do you think of > neutrinos? Likely a theory can be divised in which they don't exist, but > instead we just introduce a correction factor in calculations. IMO, Okham's > razor is easily misapplied. If it were the case that the only way to detect neutrinos is through a "remnant" or a ghost of missing energy and spin -- perhaps. But perhaps you did not know that we routinely detect collisions of neutrinos with matter, and can attribute the colliding particle to nothing else but a neutrino. > > > 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. > > Right - except maybe if physics is based on the premise that its purpose is > to investigate nature by observations, and not just observations. > AFAIK, such used to be its purpose. Ah, but I thought you said above that physics had to be neutral about things which it could not observe. Here you seem to be saying that physics is about saying something definite about things which it cannot observe. Which is it? PD > > Harald > > > > > 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: Daryl McCullough on 18 Mar 2005 09:48 cadwgan_gedrych(a)yahoo.com says... >Foul. >Slowly transported clocks are not E-synched. (His >definition does not mention moving clocks, and uses >light signals.) Why is it a *foul*? E-synch is a convention. The fact that E-synch produces the same result as slow clock transport is a *prediction* of relativity theory. >Wrong. SR does not pertain to actual or physical clock slowing, >and yet that is what would happen during clock transport. SR pertains to *all* physical processes. The physical content of SR is the claim that all physical laws are invariant under the Lorentz transformations. >As I said, SR makes zero predictions about intrinsic >clock rhythms. As I said, that's false. The relativity principle, together with Einstein's theory, allows you to make definite predictions about how a clock behaves when travelling an accelerated path. If you have some cyclic, self-contained system (such as a vibrating crystal, or a mass oscillating on a spring), you can measure the period in your frame. Call that T. Now you set the system in motion at some speed v. The relativity principle tells you that, as measured in the new rest frame, the period will again be T. Einstein's theory predicts that the period will be T/gamma as measured in the original frame (using E-synched clocks). That is a prediction of relativity theory. >Here again is my specific complaint about special relativity: >```````````````````````````````````````````````````````````````` >It makes exactly zero physical predictions which are nontrivial, >noncircular and/or correct, or so it is not a scientific theory. Yes, but your specific complaint is *false*. I gave you a specific prediction of relativity theory. Your complaint really seems to be that you cannot *derive* the prediction from Einstein-style thought experiments involving light signals. That is true. But Einstein only used those thought experiments to derive the Lorentz transformations. The physical content of relativity is not simply the Lorentz transformations, it the Lorentz transformations, together with the *physical* hypothesis that the laws of physics are invariant under the Lorentz transformations (that includes the assumption of the invariance of the vaccuum under Lorentz transformations). If you are defining SR to be only the mathematical derivation, then yes, it isn't a physical theory, it's mathematics. But what physicists mean by SR is more than that. What physicists mean by SR certainly makes physical predictions---the elapsed time on a moving clock is an example. -- Daryl McCullough Ithaca, NY
From: PD on 18 Mar 2005 10:13 cadwgan_gedrych(a)yahoo.com wrote: > PD wrote: > > cadwgan_gedrych(a)yahoo.com wrote: > > > > Here is an example of its blatant circularity/triviality: > > > > > > SR sez: > > > "If we manually force all clocks in all frames to > > > obtain the same one-way light speed, then, by George, > > > all clocks in all frames will obtain the same one-way > > > light speed." > > > > > > Can you, even your blinded eyes, see the silly circularity? > > > > You confuse a conclusion with an assumption. Read the 1905 paper. It > > states at the outset that the constancy of the speed of light is an > > *assumption* of the theory, not a conclusion of the theory. > > See my response to Daryl. (It cannot be an assumption because it is > given up front via definition.) Reread the paper. He cites it as a "postulate". A postulate is something that is assumed to be true, not something that is proven to be true. > > > Now, if you have any experimental evidence that the speed of > > light is NOT constant for all inertial frames, then let's have > > that, because that would be a truly interesting result (and it > > would immediately dispense with a whole bunch of physics, > > including SR, GR, the Dirac equation, quantum field theory, > > QED, QCD, the standard model Lagrangian, nuclear physics, etc.). > > > > PD > > (The proper word is "invariant," not "constant." These things matter > when discussing the in's and out's of physics.) Except in the case of c, the number is both an invariant AND a constant. Invariant: independent of inertial frame of reference Constant: independent of any experimental measurement; single-valued Would you like to contest those physical definitions? > > The only "physics" that one-way invariance would "blow away" would > be SR. > > And, ironically, Einstein himself told us exactly how to have > one-way variance. In his little popular book "Relativity," he > stated mathematically that if the assumed-to-be-absolutely- > synchronous clock of classical physics were used, then light's > one-way speed would be c +/- v in all frames. Which conflicts with observation, which is why the synchronous clock of classical physics is a poor assumption. > > But I do not need such clocks to answer your challenge to > provide experimental evidence that the speed of light is NOT > constant [sic] for all inertial frames because all I need is > the following simple experiment: > > Let two observers meet in passing as a light ray approaches > them. > > (Oa = Observer A and Ob = Observer B) > > ........Oa > ......................................<~~~~~~~~~light ray > ........Ob > > When the two observers briefly meet, they know that the light > ray's tip is equidistant from them because they are at a single > point in space, and the ray's tip is also at one point in space. > We can qualitatively label this distance "X". > > After the observers separate, the light ray will reach one of > them, as shown below: > > ...Oa > ............<~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~light ray > ...........Ob > > Since the tip of the light ray cannot be in two places at once, > the observers will see it sequentially at absolutely different > times. (Here is a down-to-earth example: If I see the real you > in both Texas and New York, then this proves that I saw you at > absolutely different times because you cannot be in two places > at once.) > > We can - again purely qualitatively - label the ray's absolutely > different arrival times "Ta" and "Tb." (All we care about here > is the fact that these times are absolutely different.) > > The observers can now compare one-way light speeds. (Having no > rulers or clocks, they must do this qualitatively.) Here are > their extremely simple results: > > Light's speed wrt Oa = X/Ta > > Light's speed wrt Ob = X/Tb And they know their clocks are synchronized with respect to each other how? PD
From: Daryl McCullough on 18 Mar 2005 10:03
cadwgan_gedrych(a)yahoo.com says... >> You confuse a conclusion with an assumption. Read the 1905 paper. It >> states at the outset that the constancy of the speed of light is an >> *assumption* of the theory, not a conclusion of the theory. > >See my response to Daryl. (It cannot be an assumption because it is >given up front via definition.) I'm not sure whether you are making a substantive argument, or a terminological one. Consider the following experiment: Take two identical atomic clocks. Take them out into outer space far from atmosphere, far from any source of gravity. Let one clock remain at rest in an inertial frame. Put the second clock on a high speed rocket, and take it on a outward-bound trip at speed v for a year, and then back at speed v. After the two clocks are reunited, compare the elapsed times on the two clocks. Let T1 be the elapsed time on the first clock, and let T2 be the elapsed time on the second clock. If I predict that T2/T1 = square-root(1-(v/c)^2), that seems like a falsifiable prediction to me. You seem to be claiming that such a prediction isn't *really* a prediction of SR. Okay, if you want to say that, go ahead. It's not important what you call it. The fact is that there is a collection of well-understood, falsifiable predictions that physicists think of as consequences of SR. Call the rules for making these predictions "Theory X". You want to say that Theory X is not SR. Okay, who cares what you call it? Do you agree that Theory X makes falsifiable predictions? Do you agree that my prediction about the results of comparing elapsed times on atomic clocks is a falsifiable prediction of Theory X? -- Daryl McCullough Ithaca, NY |