It raced so fast the pulse exited a specially-prepared chamber before it even finished entering it.
The experiment is the first-ever evidence of faster-than-light motion.
The result appears to be at odds with one of the basic principles of Albert Einstein's theory of relativity, that nothing can go faster than the speed of light in a vacuum, about 186,000 miles per second.
The NEC Research Institute lab
However, Lijun Wang, one of the scientists from the NEC Research Institute in Princeton, N.J., says their findings are not at odds with Einstein.
She says their experiment only disproves the general misconception that nothing can move faster than the speed of light.
The scientific statement "nothing with mass can travel faster than the speed of light" is an entirely different belief, one that has yet to be proven wrong. The NEC experiment caused a pulse of light, a group of waves with no mass, to go faster than light.
For the experiment, the researchers manipulated a vapour of laser-irradiated atoms that boost the speed of light waves causing a pulse that shoots through the vapour about 300 times faster than it would take the pulse to go the same distance in a vacuum.
Light travels slower in any medium more dense than a vacuum, which has no density at all. For example, light travelling through glass slows to two-thirds its speed in a vacuum. If the glass is altered, the light can be slowed even further.
The NEC team produced the opposite effect. Inside a chamber, they changed the state of a vapour in a way that light travelling through it would travel faster than normal.
When the pulse of light travelled through the vapour, the pulse reconfigured as some component waves stretched and others compressed. As the waves approached the end of the chamber, they recombined, forming the original pulse.
The key to the experiment was that the pulse reformed before it could have gotten there by simply travelling through empty space. This means that, when the waves of the light distorted, the pulse traveled forward in time.
The NEC researchers published their results in this week's issue of the journal Nature.
