Scientists Slow Down Speed of Light

B O S T O N,   Feb. 19, 2001 -- Scientists have managed to slow down light so much that if it were a car on a highway, it could get a ticket for not getting over to the right-hand lane.

The speed of light is normally about 186,000 miles per second, or fast enough to go around the world seven times in the wink of eye.

Scientists succeeded in slowing it down to 38 mph.

They did this by shooting a laser through extremely cold sodium atoms, which worked like “optical molasses” to slow the light down.

The experiment doesn’t invent any new physics. When light passes through a material such as water or glass, it slows down a bit as the photons interact with the surrounding molecules. The new result merely set the world record for slowest light.

Practical Applications

While slow-speed light now is just a laboratory plaything for top physicists, Lene Vesergaard Hau, the Danish scientist who led the project, said practical applications could be a few years away. She envisions improved communications technology, switches, even night-vision devices.

The atoms were contained in what is called a Bose-Einstein condensate, a condition created when matter is cooled almost to absolute zero, the lowest temperature theoretically possible. That’s 459.67 degrees below zero.

“We have really created an optical medium with crazy, bizarre properties,” Hau said. “Everybody knows that light is something that goes incredibly fast. If you could possibly slow it down to a real human dimension. That was really fantastic.”

The research, conducted at the Rowland Institute for Science in Cambridge and Harvard University, was described in Thursday’s issue of the journal Nature.