PopTech : Blog : Snowflakes made to order

Snowflakes made to order

Lindsay Borthwick ( Bio / Posts ) | Thursday, January 05, 2012 UTC

When Kenneth Libbrecht utters the words “let it snow,” the universe obliges — even in southern California, even in the summer. Libbrecht is a physicist at Caltech, but he’s also a snowflake designer, manipulating water and air in his laboratory to produce the exquisite ice crystals we love to sing about —and to play about in — each winter.

But why? What secrets can a tiny, elemental snowflake yield to science today? As Libbrecht recently told the journal Nature (subscription required):

We see these beautiful structures falling from the sky, and we still cannot explain how they came to be. When you ask how snowflakes form, you are really asking about how molecules go from a disordered gaseous state to an ordered crystalline lattice. Unexpected phenomena can emerge — snowflakes are one fascinating example.

So his interest boils down to wanting to understand how crystals grow, the physics of which may find application in materials science. More specifically, Libbrecht is trying to understand why temperature has such a dramatic impact on the shape of snow crystals, producing simple, needle-like crystals at one temperature and extraordinarily complex, star-like ones at another. It's hard to believe, but the physics responsible for this transformation is still a mystery.

It should be said that Libbrecht’s interest in snowflakes isn’t purely academic. He’s an accomplished snowflake photographer, an author of several books on the icy crystals, and a pilgrim of sorts, who travels to snowflake “hot spots” – in Canada and Japan, for example – in search of the world’s best snow crystals. (Visit his website, SnowCrystals.com, for a flurry of facts and images about snowflakes including whether any two are the same.)

When in Pasadena, he uses his design studio — otherwise known as a “vapor diffusion chamber” — to try to create what nature has perfected. The chamber is essentially a box full of very humid air that’s cold at one end and hot at the other. LIbbrecht manipulates the most basic snowflake form, a hexagonal prism barely visible to the human eye, by varying temperature and humidity. As water vapor comes into contact with the corners of the prism, the snowflakes grow, forming the iconic shapes we know so well.

As an essay in the same issue of Nature makes clear, Libbrecht isn't the first scientist to be smitten by snow. According to the piece, which revisits a 17^th-century booklet called On the Six-cornered Snowflake, by German mathematician Johannes Kepler, Kepler was strolling through Prague when he spotted a snowflake on his lapel. He began contemplating its geometry, and ultimately produced a 24-page treatise that, apparently, “seeded the notion from which all of crystallography blossomed: that the geometric shapes of crystals can be explained in terms of the packing of their constituent particles.”

Snowflakes, it seems, have already given science a great deal.

Photo: Kenneth Libbrecht, SnowCrystals.com

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