You know Doc, you remind me of a frightened witchdoctor howling and raging when a pharmacologist turns up. You still don't get this
scientific evidence thing do you?

Originally Posted by
DrRocket
BTW the Shapiro delay deals with coordinate time, not local time, and absolutely does not imply that the local speed of light is anything other than the constant c.
The local speed of light is always measured to be constant because we use the motion of light to define our second and our metre, which we use to measure the motion of light. We can make electrons (and positrons) out of light, we can annihilate protons (and antiprotons) to yield light, so anything that affects the light affects us and our rods and clocks. Clocks like the
NIST caesium fountain clock referred to in the
definition of the second:
"Since 1967, the second has been defined to be the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom. This definition refers to a caesium atom at rest at a temperature of 0 K (absolute zero), and with appropriate corrections for gravitational time dilation."
Like I was saying, lasers and a microwave cavity are employed to cause hyperfine transitions, electron spin-flips. They're electromagnetic. They emit microwaves. They're electromagnetic too. A detector finds the peak frequency. But frequency is measured in Hertz, which is defined as cycles per second, and
this clock is being used to define the second. Thus the detectors are counting incoming microwave peaks. When they get to 9,192,631,770,
that's a second, and the frequency is 9,192,631,770 Hertz by definition. Then you define the metre, then you measure the speed of light at 299,792,458 m/s. Then you take this clock and place it in a region of low gravitational potential, where all electromagnetic processes and propagation occur at a slower rate. The detectors get to 9,192,631,770, and
that's a second. Then you define the metre again and use the second and the metre to measure the speed of light again. Guess what you're going to come up with? 299,792,458 m/s again. But those two speeds aren't the same, because the seconds aren't the same, because the motion of light isn't the same. QED, the speed of light varies, just like Einstein said. I can't make it any simpler.