Other Comments:  In another section of this report the two factors which determine light's velocity in a given region of space are covered in detail.   But Briefly: The key determining influence is the velocity of light's largest proximate gravitational entity which the earth's milky way carrier.  But outside of this local frame of reference, if the earth were within a different galaxy, moving at 10 times the velocity of our milky way, then the velocity of light measured in that location would be 10 X greater than its measurement here.  Thus the phenomena of any local light velocity is ultimately understood as being determined by the gravity field of its galactic carrier:  In other words Light travels at the base velocity of its galaxy, and then its velocity is slightly reduced by local time dilation, from its proximity to stars or planets.