Gas Chilled to Record Cold Temperature
Sept. 12 -- Outer space may be cool, but not cool enough for physicists at the Massachusetts Institute of Technology who have chilled a gas to the coldest temperature ever recorded.
The coldest known place in nature is in deep space where gases are 3 degrees above absolute zero, or about -454 degrees Fahrenheit. The physicists bested that frigidity by more than 2 degrees.
In a microscopic cavity created by the repelling walls of magnetic fields, the researchers cooled a sodium gas to only a half-billionth of a degree above absolute zero. Absolute zero, or -460 degrees Fahrenheit, is the temperature where all atoms stop moving.
This is the first time that a gas has been cooled below 1 nanokelvin, which is one-billionth of a degree Kelvin.
"To go below 1 nanokelvin is a little like running a mile under four minutes for the first time," said Nobel laureate Wolfgang Ketterle, co-leader of the MIT team, which also included David Pritchard, a physicist at the university.
Cold Atoms Create New Matter
At room temperatures, atoms move at the speed of a jet airplane. At less than 1 nanokelvin, the atoms screech to a crawl, moving only one inch every 30 seconds. Atomic energy corresponds to heat since atoms' motion generates heat. So very slow-moving atoms are also very cold.
Creating a very, very cold gas is not just a cool achievement, it also helps physicists better understand a new form of matter that forms when gases get extremely cold. And since atoms in the frigid material behave in a much more predictable way than warmer ones, scientists believe it could someday be used as a tool to take extremely precise measurements.
Ketterle and a group at the University of Colorado at Boulder were the first to get a glimpse of this new matter in 1995 when they cooled a gas to 1 microkelvin — one-millionth of a degree Kelvin. Two years later, Eric Cornell and Carl Wieman documented the peculiar form when they cooled sodium gas to a few billionths of a degree above absolute zero. At this temperature, the atoms lose their separate identities and begin to behave as one.
