As you know, the starting points of the special theory of relativity are two fundamental postulates: 1) The laws of physics are the same for observers in all inertial reference systems. 2) The speed of light in vacuum has the same value in all inertial reference frames.
The postulates are a kind of axiom in mathematics which is considered as true without proof.
Personally, I think that Einsten's special theory of relativity is so beautiful and brilliant and simplify other physical phenomena nicely.
Precisely speaking, there is no empty space (vacuum) in the universe. However, we can find near empty space approximately as far as the effect of gravity of matter is concerned. In fact, we can not apply the special theory of relativity unless the space is void.
Anyway, if there is an enough gravity (heavy enough), the speed of light is not the same as the one given in the special theory of relativity. The distribution of matter in the universe can change the speed of light, in particular, if you measure its speed in an extremely heavy star.
Since the universe (stars, distribution of matters) evolves, the point made by Canadian professor may be eligible for further investigations. However, personally again, the special theory of relativity is right although it is an extremely ideal case which should apply in the empty space. Remember we need apply the general theory of relativity for large scale world where the effect of gravity is big enough and quantum theory for subatomic scale world where quantum effect is measurable. Otherwise, Newtonian classical physics explain most things with enough accuracy.
Recently, I haven't read anything about new research papers regarding theories of relativity.
Again, the constant speed of light is one of the starting points of the special theory of relativity and should apply to an inertial reference system. Once these two postulates are accepted, any contradictions here mentioned will disappear.
