When he’s not thinking about gravity waves or the nature of stars, the chairman of Caltech’s physics department can be found wandering the northern tundra, searching for snowflakes. See end for snowflake pictures.

By Jim Dawson
Inside Science News Service

During the long, cold winters of his youth on a farm west of Fargo, North Dakota, physicist Ken Libbrecht viewed snow like most kids in the upper Midwest – something to be played in, trudged through, and shoveled.

Only after obtaining his PhD in solar physics from Princeton in 1984 and working for years studying acoustic waves inside the sun and using laser cooling to trap individual atoms did Libbrecht turn his research skills to a topic that reconnected him with his childhood: snowflakes.

“As a kid, there were snowflakes everywhere, and I didn’t pay much attention to them,” Libbrecht said from his office at the California Institute of Technology in Pasadena, where he is chairman of the physics department. “When I finally studied them, I realized I should have paid attention.”

What he found was a fascinating world of both simple and complex physics, and a world of amazing beauty. For the past decade Libbrecht has been toting a photographic microscope from Southern California to snow fields in the north and taking exquisite photographs of the white ice crystals. In his newest book, The Art of the Snowflake (Voyageur Press), Libbrecht reveals images of stunning beauty that fall to earth mostly unnoticed every winter – what he calls “winter’s secret beauty.”

Libbrecht has done years of respected scientific work on the growth of ice crystals, answering some questions about how crystals grow, and uncovering other questions whose answers remain a mystery. But for non-scientists, he writes about snowflakes with a style that is both insightful and easily understood.

Starting with moisture that has condensed on a fleck of dust in a cold winter cloud, “the unruly whorls and eddies in the air drive each snowflake through a chaotic, convoluted path as it grows. In this way, the wind becomes the artist, creating a multitude of unique ice sculptures using only the simplest of raw materials.”

Because the wind is the artist and the specific humidity and temperature variation determine the growth pattern of each snow crystal as it falls, Libbrecht says, “one can estimate how many different structural variations are possible for a large, branched snowflake. The number is almost unfathomably large – so large, in fact, that I can say with confidence that no two complex snow crystals have ever been, or ever will be, exactly alike.”

When he is on one of his snowflake expeditions, Libbrecht sets a piece of cardboard on a tripod and, using a magnifying glass, looks carefully at what nature puts before him. “Even on a good day,” he writes in the book, “most snowflakes are rather poorly formed, looking essentially like bits of icy gravel.” But when a good one falls, he gently picks it up with a small paintbrush, twirling the bristles to lift the flake. He places the ice crystal on a glass slide, presses it flat with the brush, slides it into the microscope in the back of his van, and snaps a picture.

“Handling snowflakes like this causes surprisingly little damage,” he writes. And if he breaks one trying to get it to the microscope, “there are plenty more to choose from.” He prefers the flakes falling from low clouds, as they are often still growing when they hit his cardboard. Flakes from high altitudes, he said, often appear “travel worn.”

Libbrecht has classified snowflakes into 35 basic types, which range from dendrites and needles to capped columns and plates. The types of snowflakes that occur during a particular snowfall are predictable to a point, as certain types form predominantly in certain temperature and humidity conditions. When the temperature is just below freezing and the humidity is low, the flakes tend to fall as hexagonal plates, with some growing six arms to become dendrites. Drop down to 20 degrees Fahrenheit, and the sky will fill with crystals shaped like needles and hollow columns. Still lower temperatures bring thin plates, sectored plates, big dendrites, capped columns, and an assortment of other forms.

For Libbrecht, searching for snowflakes is similar to going birding. His Field Guide to Snowflakes, published in 2006, is intended to guide snowflake hunters on their quests for the perfect ice crystal.

“Take a little magnifier out with you,” he says. He has taken more than 6,000 snowflake photographs, “and I never get tired of it. I have a long list of those (snowflakes) I want to photograph.”

While birders may dream of spotting the elusive, and perhaps extinct, Ivory-billed woodpecker, Libbrecht has in mind a twin column, 12-point snowflake with a 30 degree twist. “It ought to exist,” says the physicist.

He is also creating his own snowflakes in the lab, but adding chemical impurities to the air to see if they change the shape of the crystals. “I want to see if contaminants in the air affect the growth. Trace amounts of methane in the air, and carbon dioxide, might have some effect. But in one experiment I threw a bunch of methane into the chamber and it didn’t make any difference. We’re working on it.”

While his quest is usually conducted alone and in the cold, he has garnered a following of snowflake groupies that isn’t typical for a solar physicist. Several people have contacted him about using his images for tattoos, and a woman worked with him to etch a snowflake image into a glass table. In 2006, the U.S. Postal Service used four of his images to create the popular snowflake stamps.

Libbrecht isn’t sitting quietly in his Caltech lab ignoring his fame. On his website, http://www.snowcrystals.com, he has gone commercial with his snowflake pictures, offering greeting cards, posters, high-quality prints, and books. The site also contains articles on the science, history, and myths about snowflakes.

While Libbrecht feigned shock at how little the public knows about the world of snowflakes, he’s not sure that his scientific work on snowflake crystals has wider applications. “Is it good for anything? Probably not,” he says, with typical Dakotan humility. But the pictures are stunning.

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