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Snow Wonder

It's official: meteorologists logged 2006 as the warmest year on record in the United States. No need to remind Ken Libbrecht.

"Terrible year," says the California Institute of Technology physicist, one of a handful of scientists who takes serious the study of snowflakes.

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Living in flake-free (meteorologically speaking, at least) Southern California, Libbrecht over the years has traveled to Michigan, Alaska and rural Canada to study and photograph his subject, which he also grows from scratch in his lab.

His efforts and those of other flake fanatics are helping unravel how these frozen works of art are created. It's also finding applications in some unexpected places, including computer chip manufacturing and aircraft safety.

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In October, the U.S. Postal Service issued a set of 39-cent stamps featuring Libbrecht's flake portraits. He has also written what is likely to become the bible of snowflake buffs, Ken Libbrecht's Field Guide to Snowflakes, published last year by Voyageur Press.

"Looking at snowflakes is a much-underappreciated recreation," the 48-year-old North Dakota native argues in the book's forward.

Scientists who study the phenomenon, he points out, are a bit particular about their subject, cringing slightly at the word "snowflake." Their quarry is properly described as snow crystals, says Libbrecht, since flakes are often puffy agglomerations of individual crystals.

Whatever you call them, they've attracted an interesting cast of scientific characters over the years.

Johannes Kepler, a German mathematician and astronomer who first proposed that the planets orbit the sun on an elliptical path, was among the first to seriously ponder how snow crystals form.

In 1611, he wrote The Six-Cornered Snowflake, an extended rumination on the source of a snow crystal's flower-like six-sided symmetry.

Several hundred years later, a self-educated Vermont farmer named Wilson Bentley pioneered techniques to capture frozen crystals on film.

In 1885, after years of tinkering, he connected a microscope to a bellows camera and successfully captured the first photograph of a single snow crystal, which he called "miracles of beauty."

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More than 5,000 photographs followed, nearly half of which wound up in Bentley's 1931 magnum opus, Snow Crystals. (The book arrived in the nick of time. The 66-year-old died later that year, two days before Christmas, in his rural Jericho, Vt., farmhouse.)

With his images, Bentley provided the first hard proof of the astounding variety of shapes snow crystals could take.

"Every crystal," he wrote, "was a masterpiece of design and no one design was ever repeated. When a snowflake melted, that design was forever lost."

Still, a central mystery remained: How do all these intricate shapes arise in the first place?

Enter Ukichiro Nakaya in Japan. In the 1930s, after earning a degree in nuclear physics, Nakaya was hired by Hokkaido University on the country's frigid northernmost island.

But when he showed up, he quickly realized the university owned no equipment for nuclear work. So Nakaya instead turned his attention to a substance found in abundance: snow.

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Nakaya, who described snowflakes as "letters sent from heaven," began trying to grow individual crystals on rabbit hairs, spider webs and other thin filaments.

Skiers everywhere owe him. Nakaya was not only the first person to make artificial snow, but his experiments helped unravel the complex relationship between crystal shape and two key atmospheric conditions: temperature and humidity.

(Snowflake aficionados can make a pilgrimage to The Ukichiro Nakaya Museum of Snow and Ice, in Nakaya's hometown 300 miles west of Tokyo.)

Today, thanks to the physicist's efforts, scientists have a much better understanding of how snow crystals are formed.

They don't start life as raindrops or liquid water, says Libbrecht. Instead, snow crystals form directly from water vapor in the atmosphere. This vapor typically condenses around airborne dust particles, which serve as "seeds" for the fledgling crystals.

"The crystals become heavier as they grow, until gravity eventually pulls them out of their cloudy nurseries," Libbrecht writes in the January-February issue of American Scientist.

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These days some scientists are drawn to snowflake studies for practical reasons. John Hallett, a meteorologist at the Desert Research Institute in Reno, Nev., is growing snow crystals to improve aircraft safety.

Hallett, director of the institute's Ice Physics Laboratory, says his work is helping create a cockpit-mounted device to warn pilots away from crystal-filled clouds that might ice their wings.

A better understanding of snow crystals, he adds, could translate to more commercially significant crystals, including sugar, silicon semiconductors in computer chips and many metals.

"If you grow snowflakes from vapor, you could just as well be growing metals from vapor. You can use one to get insight into the other," he says.

Caltech's Libbrecht, on the other hand, says his quest is simply to understand nature's most wondrous winter display.

Since he first started working on snow crystals in 1997, Libbrecht has refined Nakaya's insights into snow crystal formation and has categorized them into 35 common species. Stellar dendrites are the ones most people know best: These are the snowflakes of Hallmark cards and the boughs of Christmas trees. But there are also less-familiar forms with poetic names such as capped bullets and arrowhead twins, needle clusters and hexagonal plates.

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Libbrecht's research has shown that crystals tend to be simpler when humidity is low and more complex as water vapor content rises.

Temperature changes also have a significant impact on snow crystal shapes - but the exact relationship remains a scientific mystery. (For more technical details on Libbrecht's research, go to snowcrystals.com.)

The one thing that everyone who encounters Libbrecht wants to know is: Is it really true no two snowflakes are alike?

The short answer, he says, is yes. The larger mystery for him is why people are so fascinated by that notion.

"It's really a funny question because no two grains of sand are alike either," he says. And nobody seems to care about that.

michael.stroh@baltsun.com


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