The rate of rotation of a star or galaxy about an axis is estimated from measurements of the redshift of light from its opposite sides. If the diameter is known, and redshift is considered to be proportional to velocity, then the rate of recession of one side and approach of the other can be calculated from the difference in their redshifts. Hence periods of rotation about the axis.
Such a calculation does not hold good if, as proposed in the stochastic regeneration model, redshift is proportional to distance but not velocity of recession from the Earth.
A suggested explanation of observations is that spin generates a disturbance in the electromagnetic field surrounding the spinning object. If the spin of the body imparts a direction of spin to the electromagnetic field, in the same way that gravity imparts a direction to a mass thrown off a spinning body, then light leaving one side of the body would have a different effective path from light leaving the other side i.e. with or against the spin, a sort of catherine wheel effect. Differences of trajectory might account for any difference of redshift.
There may be some evidence of this in measurements of spectra of the skies made high above the Earth. Measurements made in one direction were said to be slightly bluer than those made in the opposite direction.
A. C. Sturt
12 November 2001