The question is indeed about belief, one of the conclusions of the special relativity theory (in French, restricted) is that no energy can go at a velocity higher than EM waves, in order to satisfy the axiom at the start, that the speed of light is the same for all observers, whatever their movement. It seems to have been abundantly proved, even if it doesn't answer some questions. But the theory seems to be operationally fully reliable.
General relativity is more an essay to understand the substance of matter (if one can say so), and the applications are at best speculations as the theory doesn't fit special relativity. But it also launched a great part of modern physics. Disagreements gave birth to quantum mechanics and many derived applications and theories. Unfortunately, the original question about gravitation and of the universe fabrics remains completely unsolved.
A pleasant site (http://www.newtonphysics.on.ca/einstein/index.html)of a physicist exasperated by the conformism of the true believers!
Regards,
Luc
