Meet the snowflake man

What's up with snowflakes? Is it true that of the billions and billions that float from the sky, each one is different? "The Snowflake Man" thought so. He coined the phrase "no two snowflakes are alike."

The Snowflake Man was Wilson A. Bentley. He earned his nickname because he was one of the first people to photograph snowflakes with a camera mounted to a microscope.

That was more than a hundred years ago, before scientists knew much about snowflakes.

As a boy, "Willie" Bentley was curious. Each winter, he loved exploring and playing in snow in the fields around his family's farmhouse in Jericho, Vt., where he grew up.

For his 15th birthday, Willie's mother gave him an old microscope. When he looked at magnified snowflakes under the lens, he saw that snowflakes were actually crystals. He was awed by their symmetry and beauty.

Bentley's enthusiasm for snowflakes developed into a lifelong study of these frozen crystals. But he wasn't the first to take notice of these tiny ice sculptures. As early as AD 135, Chinese literature referred to six-pointed "flowers of snow." And in 1555, a Scandinavian bishop wrote about the wide variety of snowflakes.

In the early 1600s, German mathematician and astronomer Johannes Kepler observed "the six- cornered starlet," and French philosopher René Descartes ("I think, therefore I am") detailed snowflake structure.

The first book on snowflakes was published in 1864. It was written by Frances Knowlton Chickering of Portland, Maine, after she had observed snowflakes with a simple magnifying glass. Because there were no photographs, she illustrated her book with paper cutouts of snowflakes.

What these people realized was snowflakes came in many sizes. But the one thing that was always the same was that all snow crystals have six sides.

Why six? Why not five or seven sides?

To answer that, let's step back in time to learn about the man who first photographed snowflakes.

Bentley, born in 1865, picked up where other scientists left off. While those who preceded him observed snowflakes, they didn't have the equipment to record snowflake structures in the way that Bentley did. That's because he was greatly aided in his work by a new technology: photography.

By adapting a microscope to a bellows camera, Bentley became the first person to photograph a snowflake. That happened in 1885, when he was 19 years old. But it wasn't easy.

It took trial and error during one winter and part of the next before Bentley captured his first image of a snowflake. When he finally succeeded, he was ecstatic. "I felt almost like falling on my knees beside that apparatus and worshipping it!" he wrote.

For the next 45 years, Bentley took photomicrographs (photographs taken with the help of a microscope) of snowflakes. He steadily added to his collection of images, which would eventually total more than 5,000.

Universities bought copies of his pictures, and magazines published Bentley's articles. The Vermont farmer gained the respect of leading scientists. But Bentley wasn't after fame or money. He actually lost money on his photomicrographs, which were expensive to print. (He sold them for only 5 cents apiece.)

"I am a poor man," he wrote, "except in the satisfaction I get out of my work. In that respect I am one of the richest men in the world."

Bentley loved sharing with people the beauty of snowflakes. That's why in 1931, he put more than 2,000 snowflake pictures into a book, "Snow Crystals." It still inspires scientists and artists today.

For every photo Bentley took, he made detailed notes on weather conditions at the time, including the part of the storm from which the snowflake came. He also learned that snowflakes are shaped by varied atmospheric conditions that they pass through on their way to earth, such as air temperature and humidity.

Inspired by Bentley's photomicrographs, Japanese scientist Ukichiro Nakaya took up the study of snowflakes. In the 1930s, he produced artificial snowflakes in his laboratory and discovered that the shape of a snowflake is highly sensitive to changes in temperature and humidity.

Here's how it works: An ice crystal begins to form when water vapor in a cloud condenses. Depending on the air temperature, the crystal that's formed will have either a flat, six-sided shape, or a tall, columnar six-sided shape.

As the ice crystal gets blown around and falls to the ground, it passes through air that varies in temperature and moisture content. Each change causes a change in the growth pattern of the six sides of the crystal.

A columnar shape, such as the shape of a pencil, may grow into a thin needle of ice. A flat crystal may develop sectors shaped like flower petals, or it may sprout long, lacy arms. These reach out farther and farther to take up more moisture from the air.

The countless variations on the interplay of temperature and humidity produce the differences in snowflakes. And because each one takes a different path in its journey to earth, each one ends up looking different.

So, is it true that no two are alike? Physicist Kenneth Libbrecht says "yes."

The tiniest, simplest snowflakes may look alike even under a microscope, he explains. But as with identical twins, the closer you look, the more differences you'll see. "It could snow day and night until the sun dies before two snow crystals would be exactly, precisely alike," Libbrecht said.

No doubt Bentley would be pleased to hear today's full scientific explanation that no two snowflakes are alike. But he probably wouldn't be surprised that his theory that each one is unique has proven correct.

Kenneth Libbrecht, head of the physics department at the California Institute of Technology in Pasadena, is a modern-day snowflake scientist. He discusses the physics of snow - and how snowflakes form - in his book, "The Snowflake: Winter's Secret Beauty."

A snowflake is a crystalor group of crystals stuck together. It and other crystals - such as diamonds, silicon, salt, and sugar - assemble from a random collection of molecules. Snow crystals form into six-sided structures.

Dr. Libbrecht explains that snow sparkles on a sunny day because its six facets reflect light as a mirror does.

He tells us that ski areas' man-made snow is actually sleet. Its crystals are made by rapidly freezing water, whereas snow crystals are made by freezing water vapor.

Libbrecht also explains why we sometimes see a halo around the moon. It's because we're looking through a cloud of "diamond dust" - snow crystals so tiny they aren't heavy enough to fall.

He says that snowflakes hold secrets, unknown even to today's scientists.

Libbrecht's website, www.snowcrystals.com, offers many activities as well as interesting information. He tells how you can photograph snowflakes yourself and make snowflake "fossils." He also shows how anyone can have fun examining snow crystals with a small magnifying glass.

Here are some books that don't require below-freezing temperatures to learn more about snowflakes.

Snow Crystals by W.A. Bentley and W.J. Humphreys, published in 1931. It has been reprinted by Dover Publications. It is a treasure-trove of more than 2,000 of Bentley's photomicrographs. For all ages.

Snowflake Bentley by Jacqueline Briggs Martin, woodcut illustrations by Mary Azarian. A children's picture-book biography of Wilson Bentley.

The Snowflake Man by Duncan C. Blanchard. A detailed biography of Bentley written for adults.