Lunar Laser Ranging Test of the Invariance of c
Daniel Y. Gezari
The speed of laser light pulses launched from Earth and returned by a retro-reflector on
the Moon was calculated from precision round-trip time-of-flight measurements and
modeled distances. The measured speed of light (c) in the moving observer?s rest frame
was found to exceed the canonical value c = 299,792,458 m/s by 200?10 m/s, just the
speed of the observatory along the line-of-sight due to the rotation of the Earth during
the measurements. This result is a first-order violation of local Lorentz invariance; the
speed of light seems to depend on the motion of the observer after all, as in classical wave
theory, which implies that a preferred reference frame exists for the propagation of light.
However, the present experiment cannot identify the physical system to which such a
preferred frame might be tied.
