"Chuck Harris" wrote in message
...
colin wrote:

Get an rf signal generator, 100 MHz maybe, near an oscilloscope. Run a
long coax to a laser (pointer type is fine) from the generator. Run
another long coax from a pin photodetector (with maybe a NON AGC
amplifier) back to the scope. Start with the laser close to the pin
and measure phase shift. Move them apart, ditto.

This would work with a pulse generator, measuring arrival time, too.

but the signal traveling down the coax is governed by the speed of light,
by the time the received signal is brought next to the transmited signal
it has undergone a roundtrip,
moving the optical devices apart just alters the total trip, not just the
trip in one direction only.

Colin =^.^=


Well, it depends on what you are trying to do. Are you looking for
currents
in the once presumed ether?

no I just find it fascinating that its so difficult to arrange an experiment
that measures it in one direction only,
that I dont think anyone has done it. everything seems to be extrapolated
form round trip experiments.

You could take two highly stable synchronized time standards, A and B, and
move B to the destination end of the experiment, and turn on the
laser when A reaches a predefined second, and record when the light pulse
comes to B after that same predefined second.

its effectivly been done with two fixed hydrogen masers in buildings some
distance apart.
the results seemed to cuase some controversy in some cirlces.

If you are worried about relativistic effects on the time standards, you
can bring A and B back together to recheck their synchronism.


moving the clocks introduces an error too, trying to move them realy slowly
may not be enough.
the two hydrogen masers were also moving at different speeds ever so
slightly.

Colin =^.^=