Why physicists refuse to measure the one-way speed of light directly?
in [Physics]
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From: Tom Roberts on 11 Jan 2010 17:29 kenseto wrote: > one-way isotropy is not a direct measure of the value of the > one-way speed of light. Why? You can have 200,000 Km/sec isotropy or > 300,000 Km/sec isotropy. No. It is true that tests for isotropy do not directly measure the value of the speed. But once they demonstrate isotropy then the value of the one-way speed involved can only be equal to the KNOWN value for the round-trip speed of light in vacuum. After all, the round-trip paths used in such measurements consist of two one-way paths in series. > Besides, since they performed experiments to measure for one-way > isotropy why didn't they report the value of one-way speed of light > for those same experiments? Because, as I keep telling you and you keep ignoring, most tests for isotropy cannot obtain a value for the speed. Such experiments are optimized for measuring the anisotropy, and generally do this with difference techniques, not by measuring the value of the one-way speed and then subtracting values. You might have heard of the Michelson-Morley experiment. It measures the anisotropy in the round-trip speed of light, but is completely incapable of providing a value for the speed of light itself. If you would LEARN something about the subject and STUDY the experiments, you would know all this already. Tom Roberts
From: Tom Roberts on 11 Jan 2010 18:48 Sam Wormley wrote: > On 1/11/10 12:01 PM, glird wrote: >> On Jan 11, 11:22 am, Sam Wormley wrote: >>> Physics FAQ: How is the speed of light >> measured? >> [snip] >>> http://math.ucr.edu/home/baez/physics/Relativity/SR/experiments.html >> >> I looked and found this written therein: >> "At this time there are no direct tests of length contraction, as >> measuring the length of a moving object to the precision required has >> not been feasible. There is, however, a demonstration that it occurs: >> "A current-carrying wire is observed to be electrically neutral in >> its rest frame, and a nearby charged particle at rest in that frame is >> unaffected by the current. A nearby charged particle that is moving >> parallel to the wire, however, is subject to a magnetic force that is >> related to its speed relative to the wire. If one considers the >> situation in the rest frame of a charge moving with the drift velocity >> of the electrons in the wire, the force is purely electrostatic due to >> the different length contractions of the positive and negative charges >> in the wire (the former are fixed relative to the wire, while the >> latter are mobile with drift velocities of a few mm per second). This >> approach gives the correct quantitative value of the magnetic force in >> the wire frame. This is discussed in more detail in: Purcel, >> Electricity and Magnetism. It is rather remarkable that relativistic >> effects for such a tiny velocity explain the enormous magnetic forces >> we observe." >> >> It is rather remarkable that DESPITE THIS EXPERIMENTAL confirmation >> of Lorentz's length contraction, present physics still denies that it >> really happens. >> >> glird > > Depends on the observer! "Really Happening" is what one measures. And moreover, no matter what observers measure, this "length contraction" NEVER affects the object itself. As that is what a "real contraction" would mean, it's clear that this length contraction is not a real contraction OF THE OBJECT. So one must be careful in how one phrases statements about "length contraction". There are too many possible meanings of "real" to be able to use that word without saying what one means by it. Tom Roberts
From: kenseto on 11 Jan 2010 19:14 On Jan 11, 5:08 pm, Sam Wormley <sworml...(a)gmail.com> wrote: > On 1/11/10 3:59 PM, kenseto wrote: > > > > > > > On Jan 11, 11:22 am, Sam Wormley<sworml...(a)gmail.com> wrote: > >> Physics FAQ: How is the speed of light measured? > > >>http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/measure.... > > >> Physics FAQ: What is the experimental basis of Special Relativity? > >> http://math.ucr.edu/home/baez/physics/Relativity/SR/experiments..html > > >> 3.2 One-Way Tests of Light-Speed Isotropy > > > Wormy....one-way isotropy is not a direct measure of the value of the > > one-way speed of light. Why? You can have 200,000 Km/sec isotropy or > > 300,000 Km/sec isotropy. > > Besides, since they performed experiments to measure for one-way > > isotropy why didn't they report the value of one-way speed of light > > for those same experiments? > > > Ken Seto > > Kind of a moot point when the speed of light is a defined > constant of nature... and no observation has called that > into question. No wormy....you can't use a definition to invalidate a direct measurement. Ken Seto > > > > > > >>http://math.ucr.edu/home/baez/physics/Relativity/SR/experiments.html#.... > > >> Note that while these experiments clearly use a one-way light path and > >> find isotropy, they are inherently unable to rule out a large class of > >> theories in which the one-way speed of light is anisotropic. These > >> theories share the property that the round-trip speed of light is > >> isotropic in any inertial frame, but the one-way speed is isotropic only > >> in an ther frame. In all of these theories the effects of slow clock > >> transport exactly offset the effects of the anisotropic one-way speed of > >> light (in any inertial frame), and all are experimentally > >> indistinguishable from SR. All of these theories predict null results > >> for these experiments. See Test Theories above, especially Zhang (in > >> which these theories are called Edwards frames ). > > >> Cialdea, Lett. Nuovo Cimento 4 (1972), pg 821. > >> Uses two multi-mode lasers mounted on a rotating table to look for > >> variations in their interference pattern as the table is rotated. Places > >> an upper limit on any one-way anisotropy of 0.9 m/s. > > >> Krisher et al., Phys. Rev. D, 42, No. 2, pg 731 734, (1990). > >> Uses two hydrogen masers fixed to the Earth and separated by a 21-km > >> fiber-optic link to look for variations in the phase between them. They > >> put an upper limit on the one-way linear anisotropy of 100 m/s. > > >> Champeny et al., Phys. Lett. 7 (1963), pg 241. > >> Champeney, Isaak and Khan, Proc. Physical Soc. 85, pg 583 (1965). > >> Isaak et al., Phys. Bull. 21 (1970), pg 255. > >> Uses a rotating M ssbauer absorber and fixed detector to place an upper > >> limit on any one-way anisotropy of 3 m/s. > > >> Turner and Hill, Phys. Rev. 134 (1964), B252. > >> Uses a rotating source and fixed M ssbauer detector to place an upper > >> limit on any one-way anisotropy of 10 m/s. > > >> Gagnon, Torr, Kolen, and Chang, Phys. Rev. A38 no. 4 (1988), pg 1767. > >> A guided-wave test of isotropy. Their null result is consistent with SR. > > >> T.W. Cole, Astronomical Tests for the Presence of an Ether , Mon. Not. > >> R. Astr. Soc. (1976), 175 93P-96P. > >> Several VLBI tests sensitive to first-order effects of an ther are > >> described. No ther is detected, with a sensitivity of 70 m/s. > > >> Ragulsky, Determination of light velocity dependence on direction of > >> propagation , Phys. Lett. A, 235 (1997), pg 125. > >> A one-way test that is bidirectional with the outgoing ray in glass > >> and the return ray in air. The interferometer is by design particularly > >> robust against mechanical perturbations, and temperature controlled. The > >> limit on the anisotropy of c is 0.13 m/s.- Hide quoted text - > > - Show quoted text -- Hide quoted text - > > - Show quoted text -
From: zzbunker on 11 Jan 2010 19:17 On Jan 11, 8:59 am, kenseto <kens...(a)erinet.com> wrote: > Why physicists refuse to measure the one-way speed of light directly? > The answer: > The one-way speed of light is physical distance dependent. > BTW that's why they invented a new definition for a meter length: 1 > meter=1/299,792,458 light second > Using this definition the one-way speed of light is c by definition. Well, that idiot defintion is also why the people who know how computers and enginnering work invented Flat Screen Software Debuggers, and USB rather than Lisp. Blue Ray rather than Bitmaps. Atomic Clock Wristwatches and Light Sticks rather than the Ohm's Law. The History Channel rather than NIST. Digital Books rather than Microwave Ovens, CD+rw and Desktop Publishing rather than DVD. XML and Cyber Batteries rather than Fortran, GPS rather than Set Theory.. HDTV rather than PBS. Holograms rather than CMOS. All-in-One Printers rather than C++. Compact Flourescent Lighting rather than GE. Rapid Prototyoing rather than Intel. > > Ken Seto
From: Sue... on 11 Jan 2010 19:50
On Jan 11, 8:59 am, kenseto <kens...(a)erinet.com> wrote: > Why physicists refuse to measure the one-way speed of light directly? > The answer: =========== > The one-way speed of light is physical distance dependent. That should be welcomed news to a lot of physicists. If physical laws are not the same from time to time and from place to place then their study hardly merits infringement on time spent at a good fishing spot. http://en.wikipedia.org/wiki/Noether%27s_theorem#Applications Countless physicists who would rather be fishing are no doubt trying to find just the right words to thank you for liberation from an endless fool's errand. Yeah... That is why you haven't heard from any of them yet. Sue... > BTW that's why they invented a new definition for a meter length: 1 > meter=1/299,792,458 light second > Using this definition the one-way speed of light is c by definition. > > Ken Seto |