A couple of possibly related points, observations and questions:
-Within the past few years I read in the news of experiments that successfully slowed the speed of light. Once again, I don’t remember specifics as to who, where, how and when.
-Gravity does affect light. I bends light, and in the case of black holes / gravity wells, it swallows light.
-What is the speed of gravity? If the sun were to vanish, we would still see its light for about another eight minutes. How long would it take for Earth to cease its elliptical orbit and fly out in a (basically) straight line?