THE coolest thing in the universe is officially a small cloud of sodium atoms in a laboratory in Cambridge, Massachusetts.
Physicists there have chilled 2500 sodium atoms to within half a billionth of a degree of absolute zero. 鈥淣othing in the universe [we know of] is naturally this cold,鈥� says Aaron Leanhardt, who led the research. Even deep space exists at a temperature 6 billion times higher.
To cool the atoms, the team from the MIT-Harvard Center for Ultracold Atoms trapped them with magnetic fields, then allowed the gas they form to slowly expand. The result breaks the Guinness World Record for the 鈥渓owest manmade temperature鈥�.
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The team will experiment on these ultracold atoms, to look for quantum effects and see if they can be harnessed to make more accurate atomic clocks (Science, vol 301, p 1513).