Science File / An exploration of issues and trends affecting science, medicine and the environment. : Mind Over Matter : The Weird Worlds of Extreme Heat and Cold

Last month physicists at the University of Colorado chilled a batch of atoms to the coldest temperatures ever achieved on Earth--or anywhere else in the universe, for that matter. Any day now, they’re hoping to get the atoms cold enough to freeze into an entirely new state of matter.

This feat of unnatural frigidity consumed six years and more than half a million dollars. Physicists are suitably impressed. But lay people might well want to ask: What’s the point?

The answer is not simply “because it’s there” (although certainly that is one reason even scientists like to set records). Rather, it’s because there is so much to learn at the fringes of physics--at the coldest, the hottest, the smallest, the biggest, the fastest imaginable.

In fact, some scientists love nothing better than pushing nature to the edge, and sometimes over it. Who can slice time into the thinnest sliver? Who can see farthest in space, or furthest back in time?

At these extremes, things don’t simply change size or temperature; they change character.

Take size. Everyday objects like houses and mountains come in any odd shape. But when enough matter gathers in one place, gravity gets so strong that it pulls everything toward a common center. Get up to planet size and everything is round or roundish.

Add still more matter, and even gravity gets overwhelmed; it squeezes things so tight that nuclear forces take over. Big enough planets ignite into stars.

Let gravity go haywire and you get a black hole. It doesn’t matter what you started with. Sheer size determines what becomes an asteroid, a planet, a star, a hole in space.

Or think small. Zoom down to subatomic size and particles become waves. Or think fast: Whizzing along at close to light speed, particles gain 40,000 times their own weight.

At these extremes, the laws of nature (along with common sense) tend to break down. Physicists love these places because cracks in theories often open doors to other worlds. The cold frontier has been flouting natural law for nearly a hundred years now, ever since the serendipitous discovery that below certain temperatures, electricity can flow without resistance--producing, in effect, perpetual motion. Helium at very low temperatures is even more bizarre: It flows uphill and oozes through the walls of ceramic containers.

“Very cold really means very slow,” said Eric Cornell, a physicist on the team that recently achieved the coldest temperature in the universe by cooling ribidium atoms to 35 billionths of a degree above absolute zero. (By comparison, even the frigid depths of outer space are a sweltering 3 degrees above absolute zero, which translates roughly into minus 454 on the Fahrenheit scale.)

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Stopped in their tracks by laser beams and trapped in a magnetic box, Cornell’s atoms drift along at 1 or 2 millimeters per second. (At room temperature, atoms move at 800 or 900 m.p.h.)

But getting merely cold isn’t the point. “All of a sudden, the behavior changes,” said Cornell. “That’s the part that’s really interesting.”

What the physicists expect to see is so strange they don’t even know how to describe it. Just as hot water erupts into boiling and cold water solidifies into ice, super-cold substances become so still that they evolve into a new form of matter.

Suddenly, the nervous jittering of atoms becomes so quiet that a whole bunch of them can condense into a single wave, falling into perfect step. In a sense, they all become the same atom. “It’s impossible to distinguish them,” said Cornell. And because they all behave as one, it’s possible to see the weird world of subatomic behavior on an everyday scale.

Albert Einstein and Indian physicist Satyendra Nath Bose predicted that such a state of matter should exist at super low temperatures, but so far, no one has managed to get enough atoms in the same place cold enough at the same time.

Cornell thinks he’s very close. “We expect to see Bose-Einstein condensation, but how it appears and what its properties are, we don’t really know.”

Whatever happens, it’s sure to shed light on the behavior of superconducting materials--a promising technology that the world’s best scientists have not yet been able to tame.

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While Cornell explores cold, physicists in New York on the other side of the continent are getting ready to play with fire. At a new accelerator soon to go on-line at Brookhaven National Laboratory on Long Island, super-hot, super-dense matter is expected to melt into equally mysterious forms. Physicist Frank Wilczek of Princeton’s Institute for Advanced Studies, for one, is eager to know such things as: “Does the vacuum melt?” In other words, if empty space gets hot enough, will its present structure dissolve into an amorphous blob?

One normally doesn’t think of physicists as extremists, but sometimes brinkmanship can really pay off. In this game, fire or ice can be equally rewarding.