The theory of Special Relativity is the basis of modern physics. Einstein used it to elegantly explain how the cosmos works. In part, this theory says the speed of light is constant. It always travels at 186,000 miles per second.

But Special Relativity falls apart on very small scales. Something is wrong with it. But what? A possible variation in the speed of light could be the key. And it could lead to a theory that explains everything. Or not. For scientists, being wrong is just as interesting as being right.