/Krista Niles, AP Ken Libbrecht points to platelet growth on a snowflake grown in his lab at the California Institute of Technology.

More information Ken Libbrecht: Snow crystals.

By Andrew Bridges, AP science writer

PASADENA, Calif. — Ken Libbrecht is perhaps the flakiest man going in the rarified world of physics.

Working in a small laboratory at the California Institute of Technology, Libbrecht routinely matches Mother Nature in her skill in churning out a product as beautiful as it is ephemeral: the snowflake.

Unlike Libbrecht's other pursuit — the search begun by physicists in Albert Einstein's day for gravity waves, the elusively mysterious ripples in the fabric of space and time — snow-crystal growing can satisfy in minutes, if not seconds.

"There is a lot of instant gratification," said Libbrecht, as he adeptly demonstrated his technique on a recent morning, cranking out multiple crystals, each as unique as any found cascading from a cold, winter sky.

Libbrecht, chairman of the powerhouse university's physics department, began studying snow crystals — snowflakes are actually clumps of snow crystals — about five years ago.

The fruits of his labor are stunning: his Web page contains countless images of snow crystals. He and Midwest photographer Patricia Rasmussen plan a book to feature the most photogenic crystals they've spied in nature and the lab.

But the work is also valuable science. The physics of snow crystal morphogenesis — how the patterns grow — largely remains a mystery.

"I just became intrigued by the physics and that we don't understand how it works — how ice crystals grow," said Libbrecht, whose upbringing on a North Dakota farm gives him an impeccable cold-weather pedigree.

Snow has captured the interest of scientific minds since at least Johann Kepler, whose 1611 work, "A New Year's Gift, or On the Six-Cornered Snowflake," was the first treatise to ruminate on why crystals always display a six-fold symmetry.

	/Krista Niles, AP
	Snowflakes grow in the lab of physics Professor Ken Libbrecht

Scientists know that snow crystals form from water condensed from its gaseous state, each growing around a tiny nucleus, typically a speck of dust.

As more and more molecules of water attach to the growing crystal, they do so selectively, giving it its distinctive, hexagonal shape.

On the subject of whether any two snowflakes are identical, Libbrecht said crystals are like human faces. Stand back far enough, he said, and any two appear identical. Come closer, though, and their variety shines through.

What scientists don't know is why crystal growth rates vary so much as a function of temperature and humidity. It turns out that each tiny crystal, seemingly so serene, betrays a life that is incredibly dynamic, as each totters on the brink of the melting point.

"Thermodynamically, it's an extraordinarily active material, so it's always changing," said Sam Colbeck, a retired geophysicist from the U.S. Army's Cold Regions Research and Engineering Laboratory in Hanover, N.H., where he was an expert on how crystals grow in snow cover.

Following on Kepler's heels, Libbrecht has developed the means to study crystals firsthand, even on winter days when the Pasadena campus of Caltech basks in the Southern California sunshine.

He is one of what's perhaps just a handful of physicists and meteorologists who work in the field — and that's fine by him.

"I've worked in fields that are crowded before and I prefer not to," Libbrecht said.

Libbrecht grows his crystals in a small, insulated box made of plastic foam and glass, sealed with silicone caulk.

The box is cooled at the bottom and heated at the top, creating within a stable temperature gradient. A piece of felt, soaked in water, creates the moist air from which growing crystals snag water molecules.

A piece of two-pound test line, stretched vertically, crosses the various gradients. That allows crystals to grow fastest at whatever point on the fishing line that is, Goldilockslike, just right.

"It's not toxic or messy. And it's cheap," Libbrecht said. "Experimentally, I love the stuff."

During a recent demonstration, Libbrecht showed off three clumps of crystals, spaced fairly evenly along the line. The distribution illustrates how temperature-sensitive they can be.

	California Institute of Technology, Ken Libbrecht
	Snowflakes, each about one millimeter in diameter, growing on the ends of thin ice needles in the lab of physics Professor Ken Libbrecht

At 28 degrees Fahrenheit, the crystals grow as plates. At 23 degrees, it's columns or needles. At 5, it's back to plates. If temperatures dip as low as minus 20, it's columns again.

"It sort of varies, plates to columns, to plates to columns, to plates as a factor of temperature," Libbrecht said.

In the 1930s, Japanese physicist and snow crystal pioneer Ukichiro Nakaya was the first to recognize that the shape of each crystal, when deciphered, betrays the conditions under which it was born. "Hieroglyphs sent from the sky," Nakaya called the crystals.

"The crystals will tell you very neatly what the temperatures are," Libbrecht said. "That one string tells you a wonderful story."

Replacing the string with a section of tungsten wire, the story becomes even more dramatic.

Libbrecht first puts 2,000 volts of electricity on the wire. That creates a strong electrical field at the tips of whatever ice crystals are already present and encourages them to grow further.

Magnified by microscope, the crystals can be seen to surge in length, growing 10 times faster than normal to form slender, hexagonal "pencils" of ice.

"They just shoot out in long, thin needles," Libbrecht said.

Cutting the voltage and dropping the temperature, the crystals revert to more normal growth patterns.

It takes Libbrecht just a few minutes to grow flowers of ice, complete with delicate crystals sprouting from the stalklike columns. "Designer crystals," he calls them.

On a recent morning, one of the stalks of a just-grown example began to droop, dropping into view a perfect, star-shaped crystal.

"Oh, look at that. It doesn't get any better than that," Libbrecht said.

The trick, discovered by luck, is the silicone caulk that holds the ice box together. Something in the volatile vapor it gives off modifies the growth of the needles.

Next door, a larger, more sophisticated tank allows the 43-year-old to create miniature blizzards — and then separate out individual crystals to clock their individual growth rates.

"They're telling us volumes," he said of his snow crystal research. "I just don't know what it means yet."