MadSci Network: Physics |
Dear Virginia, In the last ten years or so there has been a real breakthrough in the quest to reach very low temperatures. This has been due to techniques which use lasers to cool gases of atoms. A laser beam consists of photons which can collide with atoms in a gas. If the lasers are tuned just right, the collisions will tend to slow down the gas atoms down more than speed them up. There is a whole bag of tricks that can be employed to lower the temperature this way, and presently it is possible to reach within one millionth of a degree above absolute zero. It is, however, theoretically impossible to get all the way to absolute zero. I can't give you a detailed explanation of all the techniques, but if you are interested in looking into this further you should look up the 1997 Nobel prize in physics which was given in recognition of laser based cooling. You can check out the Nobel prize web page at www.nobel.se or you can find printed copies of the Nobel prize speeches in your local library. Larry
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