Re: Slowing the speed of light

Gina Miller (
Sun, 25 Apr 1999 19:57:50 PDT

Michael Mcdermott wrote:
>hmm, is light really slowed in this experiment, or is it just passed
>through a medium which mearly causes light to take a path through the
>medium so that it seems to be moving slower.

In response here are more details from ABC science news (copy and pasted)

‘Optical Molasses’ Slows Light
Scientists Reduce Speed of Light to a Crawl

Danish physicist Lene Vestergaard Hau, and colleagues have reduced the speed of a light pulse to 17 meters per second - a factor of 20 million less than its speed in a vacuum. (Photo by Rowland Institute for Science/Reuters)

By Tom Kirchofer
The Associated Press
B O S T O N, Feb. 19 — 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 nightvision 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.

Copyright 1999 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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By shooting a laser through very cold sodium atoms, scientists manage to slow the speed of light to 38 mph.

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