Question

Is the expansion of space taken into consideration when calculating light or any (Radio to Gamma) wave length distance and speed? I know C is a constant, but my concern is if "space expansion" is somehow altering the speed of light or any other wave length relative between two points.

Answer 1

The way in which this would occur is that a photon emitted by A would be recieved by B at some later time, when B had cosmologically accelerated away from A, so it would see a redshifted wavelength. In terms of a local description, the expansion of space is entirely contained in the local relative motions of objects, so that if two things are relatively stationary, there will be no additional wavelength change as light propagates between them.

When they are far away on a cosmological scale, at least one of these two relatively stationary things will seem to be moving relative to the cosmological idea of being at rest (no redshift in the microwave background).

It is incorrect to impute the redshift of light to an expansion of space over and above the relative motion of emitter and reciever. The expansion of space just tells you how different rest frames far away are related.