Concerning the Speed of Light
(1999)

In science news, researchers have discovered how to slow light down to a speed which could be exceeded by a strong bicyclist.

This result was anticipated by Einstein and quantum physics. In case you want to try this at home, just use laser light to cool down a medium to near absolute zero. Boil off the warmer electrons, and iterate. Then send a laser beam through it at right angles, count one-mississippi, two-mississippi, three-mississippi, and watch it come out the other side.

The idea is that when you cool off the medium, the momentum of the atoms nears zero. But the uncertainty principle limits how accurately we can know the product of the momentum and the position. Since the momentum is known (near-zero), the position becomes very unknown — even to the atoms themselves, apparently, as they start to overlap and merge into kind of a super-atom sharing the same wave function. The result is a medium with an incredibly high index of refraction, which could be useful for those of us who would otherwise need extremely thick lenses.

The refractive index is about 100 trillion times greater than that of a glass optical fiber. At one point their system had approximately the transparency of lead. Then they tickled it with a probe laser and it laughed out about 25% of the light.

This reminds me of a short story I read a long time ago, "Light of Other Days" by Bob Shaw, about a house which had a picture window made of a kind of glass so dense that it took light fifty years or so to travel through it. The owner could look through the glass and see his wife when she was still alive, etc. This is just one of the many applications that are right around the corner. A more immediate effect on our daily lives is that cops can now pull you over whenever they please and say, "Did you know you were going faster than the speed of light?"

The discovery was made by Danish physicist Dr. Lene Vestergaard Hau. Other scientists hope to use this technology to make devices that up-shift infrared light into the visible range so they can watch her undressing at night.

 

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