Why physicists refuse to measure the one-way speed of light directly?
in [Physics]
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From: Da Do Ron Ron on 11 Jan 2010 16:48 Tom R wrote: >It should be clear that using Einstein's synchronization >method ... will GUARANTEE that the one-way speed of light >will be measured to be c. How is this guaranteed? (That is, what exactly did Einstein do to make it happen?) ~~RA~~
From: GogoJF on 11 Jan 2010 16:49 On Jan 11, 1:54 pm, Tom Roberts <tjrob...(a)sbcglobal.net> wrote: > GogoJF wrote: > > Tom: Why can't you use my concept of the "Light sandwich experiment", > > that I proposed in this paper? http://www.wbabin.net/physics/gogo4.pdf > > Because that approach ASSUMES that the one-way speed of light is isotropic! That > is inherent in this statement: "Since the clock is stationed exactly in between > Omni light sources A and B, Omni light sources A and B are illuminated at > precisely the same time at tA and tB." > > Given that the one-way speed is isotropic, then its value > MUST be the same as the two-way speed. There is no ambiguity in > measuring the latter, and we know its value. > > Claiming "it is impossible to measure the one-way speed of light" is a rather > gross overstatement -- one can clearly do so with two clocks and a measured > distance between them. Note that it INHERENTLY requires two clocks to make a > one-way measurement, and that requires that the two clock be synchronized -- > there's the rub! > > What is impossible is to divorce the result of such a measurement from the > method of synchronizing those two clocks. But one can synchronize two clocks in > ANY manner whatsoever, which implies that one can obtain ANY answer whatsoever > from such a measurement. > > Your paper chose to use one of Einstein's methods to synchronize > the two "Omni light sources" A and B. That's a reasonable method, > but it is not unique. > > It should be clear that using Einstein's synchronization method (any of them; > they are all equivalent) will GUARANTEE that the one-way speed of light will be > measured to be c. Note also that slow clock transport in an inertial frame is > equivalent to Einstein's methods. > > [Your quote from Croca requiring 100 meter paths is woefully > outdated. Detectors now exist with resolutions of a few > picoseconds.] > > [Also: The links to "poincare-curse" are all dead.] > > Tom Roberts Tom said: Your paper chose to use one of Einstein's methods to synchronize the two "Omni light sources" A and B. That's a reasonable method, but it is not unique. Gogo says: Tom, thanks for your comments. Could you please reference Einstein method which is identical to mine. Sure would appreciate it.
From: Androcles on 11 Jan 2010 16:55 "Da Do Ron Ron" <ron_aikas(a)hotmail.com> wrote in message news:f5decbd3-4e3c-4581-a010-9fd911ad1396(a)j14g2000yqm.googlegroups.com... > Tom R wrote: >>It should be clear that using Einstein's synchronization >>method ... will GUARANTEE that the one-way speed of light >>will be measured to be c. > > How is this guaranteed? (That is, what exactly did Einstein > do to make it happen?) > > ~~RA~~ He said this: http://www.androcles01.pwp.blueyonder.co.uk/Shapiro/Crapiro.htm
From: kenseto on 11 Jan 2010 16:59 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 > > 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 æther 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 731734, (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 Mössbauer 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 Mössbauer 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 æther are > described. No æther 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.
From: Sam Wormley on 11 Jan 2010 17:08
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. > > >> >> 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. > |