Why physicists refuse to measure the one-way speed of light directly?
in [Physics]
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From: Cwatters on 11 Jan 2010 14:02 "Androcles" <Headmaster(a)Hogwarts.physics_r> wrote in message news:uAI2n.38994$Qm6.29837(a)newsfe08.ams2... > > "Sam Wormley" <swormley1(a)gmail.com> wrote in message > news:rPGdnRQjJNPTzdbWnZ2dnUVZ_r5i4p2d(a)mchsi.com... >> Physics FAQ: How is the speed of light measured? >> >> http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/measure_c.html > > Proper method: > speed = distance/time. > > Why do shitheads refuse to measure the one-way speed of light directly? > > Why don't you try?
From: PD on 11 Jan 2010 14:28 On Jan 11, 7:59 am, kenseto <kens...(a)erinet.com> wrote: > Why physicists refuse to measure the one-way speed of light directly? Because it would not add to the information already available from two- way-light-speed measurements and anisotropy measurements. We've been through this. > 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. > > Ken Seto
From: Tom Roberts on 11 Jan 2010 14:54 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
From: Sue... on 11 Jan 2010 15:19 On Jan 11, 2:54 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! << U. S. intelligence agencies believe China performed a successful anti-satellite (asat) weapons test at more than 00 mi. altitude Jan. 11 destroying an aging Chinese weather satellite target with a kinetic kill vehicle launched on board a ballistic missile >> http://www.spaceref.com/news/viewnews.html?id=1188 Perhaps China knows something about clock synchronisation that you have not considered. Sue... http://en.wikipedia.org/wiki/Lorentz_ether_theory#Later_activity_and_Current_Status .. > > 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
From: Sam Wormley on 11 Jan 2010 15:24
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. |