Why physicists refuse to measure the one-way speed of light directly?
in [Physics]
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From: Sam Wormley on 11 Jan 2010 12:44 On 1/11/10 11:15 AM, GogoJF wrote: > I think what kenseto is trying to say, "Why do physicists refuse to > measure a one-way speed of light directly?"- implies this one- > directional approach. A linear one way path requires a fixed known (measured) distance and a synchronized timing system. Both distance and time are DEFINED in terms of light speed and light frequency.
From: Tom Roberts on 11 Jan 2010 12:48 kenseto wrote: > Why physicists refuse to measure the one-way speed of light directly? You confuse "refuse" with an inability to do so accurately enough to be useful. The problem with any one-way measurement is that the systematic errors are large. So large that competing theories cannot be distinguished via this method. For round-trip measurements the situation is quite different. From pre-1983 measurements it is known that the round-trip speed of light in vacuum in any earthbound laboratory is within 1 meter/sec of the currently defined value. That is, after all, the rationale behind the redefinition of the meter. > The answer: [...] Ken's "answer" is nonsense. But yes, today the International Standards Organization defines the speed of light in vacuum to be constant, and they define the meter in terms of the speed of light and their definition of the second. [You REALLY don't understand this, and like a hamster in a wheel you keep re-tracing old steps without getting anywhere. Don't expect me to respond until you LEARN something about this.] Tom Roberts
From: glird on 11 Jan 2010 13:01 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
From: GogoJF on 11 Jan 2010 13:26 On Jan 11, 11:48 am, Tom Roberts <tjrob...(a)sbcglobal.net> wrote: > kenseto wrote: > > Why physicists refuse to measure the one-way speed of light directly? > > You confuse "refuse" with an inability to do so accurately enough to be useful. > > The problem with any one-way measurement is that the systematic errors are > large. So large that competing theories cannot be distinguished via this method. > > For round-trip measurements the situation is quite different. From pre-1983 > measurements it is known that the round-trip speed of light in vacuum in any > earthbound laboratory is within 1 meter/sec of the currently defined value. That > is, after all, the rationale behind the redefinition of the meter. > > > The answer: [...] > > Ken's "answer" is nonsense. But yes, today the International Standards > Organization defines the speed of light in vacuum to be constant, and they > define the meter in terms of the speed of light and their definition of the second. > > [You REALLY don't understand this, and like a hamster in a wheel > you keep re-tracing old steps without getting anywhere.. Don't > expect me to respond until you LEARN something about this.] > > Tom Roberts 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
From: glird on 11 Jan 2010 13:55
On Jan 11, 1:26 pm, GogoJF wrote: > >< 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 it uses light-signals traveling PERPENDICULAR to the direction of motion of the source. (In STR, there is no difference in the settings of clocks in those directions. The offsets per successive clocks is in the direction of their motion.) glird |