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Researchers Cool Gas To Record Low
Vacuum chamber Image left: MIT researchers used this vacuum chamber to cool sodium gas to near absolute zero. Courtesy Ketterle Lab

The next time you're shivering under your winter coat as your local weather forecaster predicts "record lows," take heart. It could be a lot colder.

Try one-half-billionth of a degree above absolute zero, or about -460 degrees Fahrenheit (-273 degrees Celsius).

That's the lowest temperature ever recorded, recently measured by NASA-funded researchers at the Massachusetts Institute of Technology who used a unique combination of gravitational forces and magnetic fields to cool sodium gas.

Absolute zero is the point at which no further cooling is possible. All motion stops, except for tiny vibrations, because the cooling process extracts all energy from the particles. At the new low temperature, it takes atoms half a minute to move a single inch.

The Biggest Chill

Scientists have gotten close to absolute zero before, but the new temperature is six times lower than the previous record. It's also the first time a gas has been cooled to below one nanokelvin, which is one billionth of a degree.

"To go below one nanokelvin is like running a mile below four minutes for the first time," said Dr. Wolfgang Ketterle, an MIT physics professor who co-led the study.

The research, appearing in the September 12 issue of the journal Science, gives scientists at the MIT-Harvard Center for Ultracold Atoms a chance to study a recently discovered form of matter known as the Bose-Einstein condensate, first seen in 1995 by an MIT team led by Ketterle and another group at the University of Colorado.

Normally, atoms bounce around independently in many different directions at extremely high speeds. But when they cool to near absolute zero, they slow down to the point that they condense, marching in lockstep instead of flitting around independently.

The discovery of the Bose-Einstein condensate earned Ketterle and University of Colorado researchers Drs. Eric Cornell and Carl Wieman the Nobel Prize for Physics in 2001.

So, just how did the MIT team handle something so cold?

Even the best thermos in the world can't be cooled to such temperatures, and even if it could, atoms that cold can't be kept in physical containers, because they would stick to the walls.

Researchers with cooling machine Image right: Team members Tom Pasquini (left) and Aaron Leanhardt (right) in front of the cooling machine. Courtesy Ketterle Lab

So researchers came up with a novel way to confine the atoms. They used a "gravito-magnetic trap," positioning magnets around the atoms to counteract gravity and keep the gaseous cloud confined without touching it.

Dr. David E. Pritchard, Ketterle's co-leader says the research could have some real world benefits. "Ultra-low temperature gases could lead to vast improvements in precision measurements by allowing better atomic clocks and sensors for gravity and rotation."

In other words, there's much more to the science than just making a really, really big chill.

 Jet Propulsion Laboratory's Fundamental Physics in Space
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 Office of Biological and Physical Research
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 Dr. Ketterle's Research Group
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 MIT-Harvard Center for Ultracold Atoms
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