Propagation of light in noninertial reference frames
Abstract
It is shown that the complete description of the propagation of light in a gravitational field and in noninertial reference frames in general requires an average coordinate and an average proper velocity of light. The need for an average coordinate velocity of light in noninertial frames is demonstrated by considering the propagation of two vertical light rays in the Einstein elevator (in addition to the horizontal ray originally discussed by Einstein). As an average proper velocity of light is implicitly used in the Shapiro time delay (as shown in the Appendix) it is explicitly derived and it is shown that for a round trip of a light signal between two points in a gravitational field the Shapiro time delay not only depends on which point it is measured at, but in the case of a parallel gravitational field it is not always a delay effect. The propagation of light in rotating frames (the Sagnac effect) is also discussed and an expression for the coordinate velocity of light is derived. The use of this coordinate velocity naturally explains why an observer on a rotating disk finds that two light signals emitted from a point on the rim of the disk and propagating in opposite directions along the rim do not arrive simultaneously at the same point.
 Publication:

arXiv eprints
 Pub Date:
 September 1999
 arXiv:
 arXiv:grqc/9909081
 Bibcode:
 1999gr.qc.....9081P
 Keywords:

 General Relativity and Quantum Cosmology
 EPrint:
 14 pages, 1 figure, LaTeX, Section 4 has been devoted to the Sagnac effect