MuggsMcGinnis wrote:So, in what sort of reference frame would light in vacuum have a different speed?
In any non-inertial (accelerated) frame.
The statement I made isn't restricted to Special Relativity.
I think it needs to be.
I refer to measurements done under non-zero and variable accelerations.
I don't know if any experiments have been conducted under conditions where the accelerations were large enough to produce measurable deviations from what would be observed in an inertial frame. If so, I'd expect they involved particles in a circular accelerator.
Light will follow a curved path, geodesic, with respect to an accelerating reference frame but isn't it true that its speed along that path is still c?
Yes, but you need GR to understand how to measure that. From an accelerated frame, I think light can
appear to be traveling at something other than c. That is never the case in an unaccelerated frame.
[quote="MuggsMcGinnis"]So, in what sort of reference frame would light in vacuum have a different speed?[/quote]
In any non-inertial (accelerated) frame.
[quote]The statement I made isn't restricted to Special Relativity.[/quote]
I think it needs to be.
[quote]I refer to measurements done under non-zero and variable accelerations.[/quote]
I don't know if any experiments have been conducted under conditions where the accelerations were large enough to produce measurable deviations from what would be observed in an inertial frame. If so, I'd expect they involved particles in a circular accelerator.
[quote]Light will follow a curved path, geodesic, with respect to an accelerating reference frame but isn't it true that its speed along that path is still c?[/quote]
Yes, but you need GR to understand how to measure that. From an accelerated frame, I think light can [i]appear[/i] to be traveling at something other than c. That is never the case in an unaccelerated frame.