You might watch snow fall, glimpse its beauty, and think, "Oh, that's nice." Ken Libbrecht takes a much closer look. He peers into a microscope to study how snow crystals are formed and ponders the age-old question of why no two snowflakes are alike.
"It's been said that snowflakes are like hieroglyphs from the sky...," says Libbrecht, an astrophysicist and chairman of the physics department at the California Institute of Technology. "In the shape of the crystal is encoded the conditions under which it grew."
Libbrecht explores the physics of how snow crystals grow and form in the atmosphere.
"Everybody can kind of picture a snowflake in their head and yet very few people have thought about why they look like that — and very few scientists have really spent much time looking at that, either. And, in fact, we don't really understand the details of why they look like they do."
Libbrecht photographed snow crystals as a hobby. Then he expanded, with a Web site he called SnowCrystals.com. It became popular with, as he says, "snowflake enthusiasts" — science teachers and mathematicians who want to model snowflakes ... even the U.S. Postal Service, which turned one of his wintry images into a stamp.
Libbrecht travels to Vermont, Alaska and Canada and other places to understand how snowflakes get their shapes — for example, why they're symmetrical.
He breaks the science into fundamentals:
"A snow crystal forms up in the atmosphere, of course," Libbrecht says. "It starts with, say, a small water droplet which freezes into a very tiny piece of ice and then that grows and gets this hexagonal shape. Then, as it gets larger, these corners of the hexagon sprout branches and they can become very elaborate as it grows larger."
He built his own microscope with a camera attached to it to take these pictures. The whole thing fits in a suitcase so he can take it along to cold places.
Of course, the question he hears most often is whether, in fact, there are any two snowflakes that look alike.
"One thing you can do, as a physicist, is you can try to calculate how many ways there are to make a snowflake, and I've done that," he says. "And it's a very large number. The number of ways to make a complex snowflake is far greater than the total number of atoms in the universe. And with such large numbers, you can say fairly confidently that if you looked at all the snowflakes that grew on earth, you would never see one that looked exactly the same."