reply on wrong page I think Hi You wrote I assure you that the physics as viewed in a rotataing accelerated frame of reference has meaning even if the bottom line is that the same results are obtained in either case The ability of use an accelerated viewpoint is especially important in GR where you can be in a spaceship moving intertially but the effects of gravitation are such that the objects distant from you are being accelerated and effects such as gravitational time dilation and red blue shifting are none the less revealing themselves Relatitivy fundamentally is about how perceptions of the same events are changed by virtue of being in different frames of reference In essesnse changing frames of reference is a gedanken is nothing more than putting yourself is someone else s shoes In that regard their state of motion be it inertial or not should not matter I agree completely The assertion My personal opinion is that the proper way to interpret the physics of the Sagnac effect is to look at the physics from the perspective of the local inertial frame of reference I prefer the perspective of the local inertial frame of reference because that is the most symmetrical point of view By contrast as seen from a point of view that is accelerating the speed of light appears to be non isotropic and I am rather suspicious about that I very much doubt that describing physics from an accelerating point of view has any meaning at all EMS insisted that in the Sagnac effect article the physics should also be described as seen from a rotating frame of reference I tend towards the opinion that describing physics from the point of view of a rotating frame of reference does not carry any physical meaning was written by Teunisson so it might be better to reply to him I will think more about the Michaelson Morley experiment as related to acceleration I think you are right this cross dialogue is going too fast But the idea was to detect differences in the aether drift as the apparatus turned with the Earth If it were in inertial motion the supposed drift would not show up as a fringe shift A rotating reference frame is accelerated