Sagnac effect and Einstein's postulate of constant light velocity

[Bossieman]

Is there anyone here that can explain this phenomena using Einsteins postulat that the velocity of light is constant?
I haven't found any explanation to the phenomena on the Internet.

 

[quartodeciman]

The Sagnac experiment appears to be a favorite case among the CON-relativity and PRO-aether folks (the two groups are not entirely overlapping). The following is the best discussion of it I found that doesn't conclude with relativity-is-wrong. I don't know who wrote it.

reflections on relativity/the sagnac effect, by mr./ms. ?