Stopping Light

Last year, physicists at Harvard University shined a laser beam into a glass cell filled with atomic vapors. The light went in, but it didnt come out again. It was not destroyed or absorbed, but rather stored -- ready to emerge intact at the scientists bidding.The laser pulse was kilometers-long before it entered the cell, yet the pulse fit intact within the centimeters-wide chamber. Sound like magic? Perhaps ... but it was only quantum mechanics.Quantum mechanics describes the bizarre rules of light and matter on atomic scales. In that realm, matter can be in two places at once. Objects can be particles and waves at the same time. And nothing is certain -- only probable or improbable.This improbable feat -- stopping light -- was accomplished by two teams. One was led by Ron Walsworth, a physicist at the Harvard-Smithsonian Center for Astrophysics, and the other by Lene Hau of Harvard Universitys Department of Physics. Walsworths group used warm rubidium vapors to pause their laser beam; Haus group used a super-cold sodium gas to do the same thing.
http://science.nasa.gov/headlines/y2002/27mar_stoplight.htm