Reach Absolute Zero?

By Jeffrey Kluger

On the whole, the laws of physics don't like to be fooled with. Nature has pretty strict rules, not just about how fast objects can move but also about how cold they can get. Scientists know temperatures can drop only so far before absolute zero--the bitter rock bottom of physics' thermometer--stops them from cooling any further. On the way down toward the absolute-zero mark, however, remarkable things can happen.

When objects grow cooler, what is actually, if invisibly, happening is that their atoms are moving slower. At a certain point--about -460[degrees]F--the motion of all matter would stop. Such utter atomic stillness is not possible, since the colder atoms become, the more they draw warmth from anything in the vicinity--often from one another. In 1995, however, a team led by physicists Carl Wieman and Eric Cornell of the University of Colorado at Boulder used lasers and evaporation to achieve something known as a Bose-Einstein condensate, a supercold gas in which atoms overlap and begin to move in synchrony. "We get to within a billionth of a degree of absolute zero," says Wieman.

Even the best Bose condensate is a modest thing--measuring about one-tenth of a millimeter across--but the little cloud could help science take big steps. Particles frozen so rigidly in place are easy to observe and manipulate, providing a clearer than ever look at how things behave at the subatomic, or quantum, state. Down the line, such precise control may make it easier to design better atomic clocks or fabricate submicroscopic nanocomponents and other vanishingly tiny machines. Absolute zero might be an impossibility, but for scientists who have spent their careers trying to drive the thermometer down, the deep freeze they've already achieved might be more than deep enough.

--By Jeffrey Kluger