However, Dr Gunter Nimtz and Dr Alfons Stahlhofen, of the University of Koblenz, say they may have breached a key tenet of that theory.Wow!
The pair say they have conducted an experiment in which microwave photons - energetic packets of light - travelled "instantaneously" between a pair of prisms that had been moved up to 3ft apart.
Being able to travel faster than the speed of light would lead to a wide variety of bizarre consequences.
For instance, an astronaut moving faster than it would theoretically arrive at a destination before leaving.
The scientists were investigating a phenomenon called quantum tunnelling, which allows sub-atomic particles to break apparently unbreakable laws.
Now comes the effort to replicate the experiment and verify their findings.