Faster-than-light 'tachyons' might be impossible after all

Faster-than-light particles, or "tachyons", may be fundamentally impossible, according to two mathematical physicists. If they're right, their new theory would also imply that time – seemingly one of the most fundamental facets of nature – is no more than a mirage.

Although it is commonly believed that Einstein's theory of relativity says nothing can go faster than light, that is not quite true. Relativity does forbid ordinary matter from ever reaching the speed of light, because it would require infinite energy.

But the theory does not rule out a realm of particles that can only travel faster than light. Named "tachyons" by physicists in the 1960s, these subatomic speedsters would actually need an infinite amount of energy to slow down to the crawl of light-speed.