[wideminded]

a theory developed by John Barrow at the University of Cambridge in the UK and Douglas Shaw at the University of London, suggests that the sun produces a field that changes the value of the fine structure constant on Earth as its distance from the sun varies during each orbit.

Since the fine structure constant is computed from the values of the electric charge, Planck's constant, and the speed of light, one or more of these would have to be changing with distance from the sun if this theory were true.

If the speed of light were changing with distance from the sun it would produce a shift in the observed positions of stars that would have been noticed already.

[Quix]

IIRC . . .

some such differences have been reported.