You mean that you don't even know about Einstein's observers in thought experiments? (see Sir Arthur Eddington's comment that "gravity waves travel at the speed of thought").
I have always maintained that "c" was not a speed in the sense of Special Relativity, but a mass term. But then what does "c" through a medium is a constant" (your phrase) mean?
Finally, learn to write tex if you have anything intelligent to say; your language sucks.