Why physicists refuse to measure the one-way speed of light directly?
in [Physics]
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From: PD on 19 Jan 2010 15:20 On Jan 19, 2:13 pm, Da Do Ron Ron <ron_ai...(a)hotmail.com> wrote: > PD confusingly stated: > > >Isotropy is not a OWLS measurement. > > One-way isotropy was the subject at hand. We all know that experiment > has shown round-trip isotropy, so your ref. is useless. Specifically, > the subject > at hand is one-way light speed invariance. But no experiment has shown > this. > It cannot simply be assumed at the start because this means nothing. > > PD incorrectly stated: > > >Synchronization is a condition that is only satisfied in one frame > >anyway. > > You cannot have one-way light speed invariance unless observers in > _all_ frames obtain the same speed for light's one-way speed, and > this > means that clocks in _all_ frames must be set per Einstein's > definition. > > And by refusing to complete the given task, you have blocked yourself > from understanding Einstein's definition of clock synchronization. > > Here, again, are the rules: > > 1. At least two frames must be used (for invariance). > > 2. Only one light source must be used (to separate the frames). > > 3. The proper version of the definition must be used. > (This is the one that can be applied to two or more frames > using a single light source.) > > Anyone who ignores any one of these bedrock rules will not be able > to grasp the full physical significance of Einstein's definition. > > Here, again, is the task that you must complete in order to fully > comprehend that definition: > > Frame A > [0]---------x----------[?] > Source S~~>light > [0]---------x----------[?] -->v > Frame B > > Why are you afraid to fill in the blanks? > Forget about everything else, and do this now. > Only then will you see the truth. > Guaranteed. > > ~~RA~~
From: PD on 19 Jan 2010 15:22 On Jan 19, 2:13 pm, Da Do Ron Ron <ron_ai...(a)hotmail.com> wrote: > PD confusingly stated: > > >Isotropy is not a OWLS measurement. > > One-way isotropy was the subject at hand. We all know that experiment > has shown round-trip isotropy, so your ref. is useless. http://edu-observatory.org/physics-faq/Relativity/SR/experiments.html#one-way_tests > Specifically, > the subject > at hand is one-way light speed invariance. But no experiment has shown > this. > It cannot simply be assumed at the start because this means nothing. > > PD incorrectly stated: > > >Synchronization is a condition that is only satisfied in one frame > >anyway. > > You cannot have one-way light speed invariance unless observers in > _all_ frames obtain the same speed for light's one-way speed, and > this > means that clocks in _all_ frames must be set per Einstein's > definition. No, that is incorrect. Each frame has its OWN set of clocks, and in EACH frame THAT set is synchronized according to the Einstein procedure. In EACH frame, then, the speed of light will have the same value. This does NOT mean that the clocks in one frame are synchronized along with the clocks in a different frame, and in general this will NOT be the case. > > And by refusing to complete the given task, you have blocked yourself > from understanding Einstein's definition of clock synchronization. No, I'm sorry, but Einstein was quite clear. > > Here, again, are the rules: > > 1. At least two frames must be used (for invariance). > > 2. Only one light source must be used (to separate the frames). > > 3. The proper version of the definition must be used. > (This is the one that can be applied to two or more frames > using a single light source.) > > Anyone who ignores any one of these bedrock rules will not be able > to grasp the full physical significance of Einstein's definition. > > Here, again, is the task that you must complete in order to fully > comprehend that definition: > > Frame A > [0]---------x----------[?] > Source S~~>light > [0]---------x----------[?] -->v > Frame B > > Why are you afraid to fill in the blanks? > Forget about everything else, and do this now. > Only then will you see the truth. > Guaranteed. > > ~~RA~~
From: Tom Roberts on 19 Jan 2010 22:34 Da Do Ron Ron wrote: > PD confusingly stated: >> Isotropy is not a OWLS measurement. Right. Experiments have shown one-way isotropy, without actually measuring OWLS. But Da Do Ron Ron does not seem to understand that: > One-way isotropy was the subject at hand. We all know that experiment > has shown round-trip isotropy, so your ref. is useless. Specifically, > the subject > at hand is one-way light speed invariance. But no experiment has shown > this. If you mean that no experiment has DIRECTLY shown one-way light speed invariance, that is correct. But it has been solidly established, indirectly, within the context of SR. In particular, "light speed invariance" is an empty phrase without a complete theory to test. For non-gravitational measurements, the appropriate theory is SR. SR has been solidly established within its domain of applicability, and it includes light speed invariance. [In a context in which gravitation is important, there is no light-speed invariance, one-way or round-trip. Indeed, in general there is not even isotropy (of either type).] > It cannot simply be assumed at the start because this means nothing. Well yes, one cannot assume what one is trying to establish. And yes, attempting to discuss "light speed invariance" divorced from a theory means nothing. > PD incorrectly stated: >> Synchronization is a condition that is only satisfied in one frame >> anyway. That is not incorrect. Your follow-on claim is so ambiguous that your statement is tantamount to being incorrect. > You cannot have one-way light speed invariance unless observers in > _all_ frames obtain the same speed for light's one-way speed, and > this > means that clocks in _all_ frames must be set per Einstein's > definition. Your English usage is excessively ambiguous. Your "in all" can mean "in every one separately", or it could mean "in every one simultaneously" -- the former is correct the latter is not. Say, rather, that one-way light speed invariance means that in each inertial frame a measurement of OWLS will obtain c, independent of the inertial frame used. In particular, it simply is not possible for a GIVEN pair of clocks to be synchronized in _all_ frames, though that is one possible interpretation of your words. We have three "pieces" that when put together establish one-way light speed invariance: A) round-trip invariance of light speed, for all inertial frames occupied by an earthbound laboratory. Those frames differ by ~60 km/s, and the experimental accuracy of the invariance is a bit less than 1 m/s. B) one-way isotropy of light speed, for all inertial frames occupied by an earthbound laboratory. Again the experimental accuracy is less than 1 m/s. C) SR is a comprehensive theory in which one-way light speed invariance holds precisely, and is consistent with all experiments within its domain, including A and B. So while no experiment has directly established one-way light speed invariance, the indirect evidence is quite solid. In particular, no known theory that does not have one-way light speed invariance is consistent with these experiments. I mean MEASURED invariance. There are theories in which the coordinates have both anisotropy and lack of invariance, but which are experimentally indistinguishable from SR. In short, for these theories their anisotropy and non-invariance precisely cancel out whenever real clocks and real rulers are used to measure the speed of light. > And by refusing to complete the given task, you have blocked yourself > from understanding Einstein's definition of clock synchronization. I have no idea what you mean by this. > Here, again, are the rules: [...] Science is not about arbitrary "rules", but rather is about formulating and testing theories experimentally. SR has been extensively tested, and has not been refuted by any experiment within its domain of applicability. That's as good as it gets. Tom Roberts
From: Da Do Ron Ron on 21 Jan 2010 15:21 T. Roberts stated: >Say, rather, that one-way light speed invariance means that >in each inertial frame a measurement of OWLS will obtain c, >independent of the inertial frame used. We are now back to square one, but that's better than nothing. I assume that your above is saying that light's one-way speed can be measured, and that it can be measured in many inertial frames. Elsewhere, you have stated that two clocks (in each inertial frame) are needed to measure the one-way speed of light. Also, you have stated that Einstein somehow synchronized these two clocks (in each inertial frame) in order to somehow guarantee c invariance. How are the clocks in special relativity synchronized? (How is c invariance guaranteed?) (What is the physical process involved?) If you cannot tell us, then why did you make that claim about Einstein's guarantee? ~~RA~~
From: PD on 21 Jan 2010 17:19
On Jan 21, 2:21 pm, Da Do Ron Ron <ron_ai...(a)hotmail.com> wrote: > T. Roberts stated: > > >Say, rather, that one-way light speed invariance means that > >in each inertial frame a measurement of OWLS will obtain c, > >independent of the inertial frame used. > > We are now back to square one, but that's better than nothing. > > I assume that your above is saying that light's one-way speed can > be measured, and that it can be measured in many inertial frames. > > Elsewhere, you have stated that two clocks (in each > inertial frame) are needed to measure the one-way > speed of light. > > Also, you have stated that Einstein somehow synchronized > these two clocks (in each inertial frame) in order to > somehow guarantee c invariance. > > How are the clocks in special relativity synchronized? I answered this. > (How is c invariance guaranteed?) > (What is the physical process involved?) > > If you cannot tell us, then why did you make that claim > about Einstein's guarantee? > > ~~RA~~ |