IT IS the coldest lump of metal ever. Physicists in Germany, led by Frank Pobell of Bayreuth University, have managed to chill 32 grams of platinum to just 3-millionths of a degree Celsius above absolute zero (鈭�273.15 掳C).
Pobell says the experiment, which ran for 10 days, will improve scientists鈥� understanding of the magnetic behaviour of platinum at extremely low temperatures. This is important basic research, he says, although it has no immediately obvious practical application.
The platinum was cooled to within a whisker of absolute zero, says Pobell, by 鈥渃leverly turning a magnetic field on and off鈥�. Pre-cooled platinum was placed in a large magnetic field which was slowly removed. The platinum atoms lost thermal energy as their nuclear magnetic energy declined. Nevertheless Pobell says that the experiment was not designed to create a new record.
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Pobell previously held the record for the coldest solid when he achieved 12-millionths of a degree above absolute zero in 1988. But in 1994 researchers at the University of Lancaster pushed the record back a further 12-millionths of a degree.
Small numbers of individual atoms, however, have been made even colder. Last year, researchers at the Joint Institute of Laboratory Astrophysics in Boulder, Colorado, cooled some 2000 atoms of rubidium to 0.17 millionths of a degree above absolute zero.