Orac,

I think you have reached an end. When Zwicky developed the hypothesis, right after Hubble observed the red shift for distant galaxies, He himself shot down several possible mechanisms. Since then astronomical measurements have gotten more and more precise. And every one of the possible explanations for how tired light could occur have gotten more and more unlikely. I suppose that there might be some strange effect that hasn't been considered, but there have been a lot of people who have looked into it and they have found no data supporting the hypothesis.

Bill Gill

C is not the speed of light in a vacuum.
C is the universal speed limit.