A pair of German physicists claim to have broken the speed of light - an achievement that would undermine our entire understanding of space and time.

According to Einstein's special theory of relativity, it would require an infinite amount of energy to propel an object at more than 186,000 miles per second.

However, Dr Gunter Nimtz and Dr Alfons Stahlhofen, of the University of Koblenz, say they may have breached a key tenet of that theory.

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.

Dr Nimtz told New Scientist magazine: "For the time being, this is the only violation of special relativity that I know of."