Physicists have known that the speed of light is variable since 2001:

"Lee [Smolin] and I discussed these paradoxes at great length for many months, starting in January 2001. We would meet in cafés in South Kensington or Holland Park to mull over the problem. THE ROOT OF ALL THE EVIL WAS CLEARLY SPECIAL RELATIVITY. All these paradoxes resulted from well known effects such as length contraction, time dilation, or E=mc^2, all basic predictions of special relativity. And all denied the possibility of establishing a well-defined border, common to all observers, capable of containing new quantum gravitational effects." Joao Magueijo, Faster Than the Speed of Light, p. 250

http://www.amazon.com/Faster-Than-Sp.../dp/0738205257
"...Dr. Magueijo said. "We need to drop a postulate, perhaps the constancy of the speed of light."

http://www.nytimes.com/2002/12/31/sc...-relative.html
Joao Magueijo, Niayesh Afshordi, Stephon Alexander: "So we have broken fundamentally this Lorentz invariance which equates space and time [...] It's the other postulate of relativity, that of constancy of c, that has to give way..."

https://youtu.be/kbHBBtsrU1g?t=1431
The problem is that the truth, VARIABLE speed of light, will completely destroy today's fundamental physics (in this sense establishing the the truth is suicidal):

"The whole of physics is predicated on the constancy of the speed of light," Joao Magueijo, a cosmologist at Imperial College London and pioneer of the theory of variable light speed, told Motherboard. "So we [Joao Magueijo and Niayesh Afshordi] had to find ways to change the speed of light without wrecking the whole thing too much."

https://motherboard.vice.com/en_us/a...t-speed-slowed
Yet:

https://pbs.twimg.com/media/Dsi1me8WsAANyer.jpg
Pentcho Valev