Slowing The Speed Of Light

Light normally moves through a vacuum at about 186,000 miles per second. Nothing in the universe moves faster, and Albert Einstein theorized that nothing ever will. But a Danish physicist and her collaborators have trimmed that speed by a factor of 20 million.

That translates to a leisurely 38 mph, a pace that would get a highway motorist pulled over for driving too slowly.

Lene Vestergaard Hau's team accomplished the feat by shooting a laser through extremely cold sodium atoms, which worked like "optical molasses" to slow the light.

"We have really created an optical medium with crazy, bizarre properties," said Hau.

While slow-speed light now is just a laboratory plaything for top physicists, Hau believes practical applications are not too far in the future. She envisions improved communications technology, television displays, even night-vision devices.

The research, conducted at the Rowland Institute for Science in Cambridge and Harvard University and described in Thursday's issue of the journal Nature, isn't something that can be replicated in a home workshop.

The laggard laser moves through a high-density group of atoms called a Bose-Einstein condensate, created when matter is cooled almost to absolute zero, the lowest temperature theoretically possible. That is 459.67 degrees Fahrenheit below zero.

Now that the scientists have reduced the speed of light to 38 mph, they believe it's possible to slow it 1,000 times further.

"A human could move faster than that," said Stanford University's Steve Harris, who participated in the project. "But a human couldn't move through a Bose-Einstein condensate."

Written by Tom Kirchofer