It wasn’t so long ago that the Coldest Spot in the Universe was drifting out in the vast emptiness of space between galaxies. Warmed only by the meager crackling of energy left over from the Big Bang, atoms out there manage no more than a brisk 454 degrees below zero Fahrenheit.
Today the Coldest Spot in the Universe resides in Boulder, Colorado. Hardly anyone is complaining, though. Business remains brisk in downtown Boulder’s hip eateries and boutiques, and hikers haven’t recorded any negative impact on the town’s treasured scenic resources. No wonder: the Coldest Spot is just a crumb of space a quarter-inch wide sitting in a lipstick-size glass tube. The tube is surrounded by a miniature forest of lenses, vacuum pumps, and laser beams, and the whole deal is neatly tucked away in Carl Wieman’s modest lab in a small, towerlike physics building at the University of Colorado.
The crumb of space enfolds a wisp of vapor consisting of a mere 200 million atoms--less than a billionth as many as in a normal chunk of air that size. But the cesium atoms in the Coldest Spot do something that no other atoms anywhere else have ever done: nothing. Or at least very close to nothing. While other atoms bounce and dance and slam and careen, Wieman’s atoms lazily float. Which is to say his atoms are cold. To be exact, they are within a millionth of a degree of absolute zero, the unreachable point on the temperature scale--close to minus 460 degrees Fahrenheit--where all matter would, if it could, come to a perfect standstill.
Other physicists, too, including Daniel Kleppner of MIT and Steven Chu of Stanford, are racing to quiet atoms to the point where they’re as cold as inhumanly possible. This desire to reach the stillest possible state of matter is driven by more than mere competitiveness; theory predicts there’s a strange new state of matter at the limit of coldness--a state unlike anything that has ever existed on Earth. Perhaps unlike anything in the universe. Atom stuff, Wieman calls it, for lack of a better word. Its properties, he says, are a mystery.
Matter, after all, has an odd way of completely changing its character as it heats up or cools down. Take ordinary water. Warm it up a bit and it changes to vapor, a gas. Heat it even more and the water molecules dissociate into oxygen and hydrogen atoms; what was wet and largely sedentary is now two fairly volatile gases. Heat it more and the atoms split apart into electrons and nuclei. Atoms, in fact, no longer exist. The disordered mixture, called a plasma, is electrically charged; under the right conditions it would glow. Of course, you can continue: in a particle accelerator you can split the nuclei into protons and neutrons; you could then, perhaps, disassemble the protons into quarks. Some physicists think that at the very top of the temperature scale there’s something called quark matter, a sea of disconnected quarks that’s so weird no one knows what its properties might be.
