Dead Serious, and Yet Flaky


A physicist in southern California, of all places, is proving himself one of the world’s foremost experts on snowflake formation, a surprisingly complicated process he has been able to re-create in his lab.

So far Kenneth Libbrecht of the California Institute of Technology has built multiple devices to grow snowflakes, including one where ice collects on the tip of a needle electrified to 2,000 volts. To mimic natural flake formation, Libbrecht also built a machine that sprinkles dust particles into a cold chamber saturated with water vapor. Like a tumbling snowball, dust attracts ice as it descends, and a snowflake grows around it.

One great mystery Libbrecht wants to clear up is how the shape of snowflakes depends on temperature. Snowflakes can take one of two shapes—six-sided flat “stars” or dagger-like crystals—but no one knows why one shape emerges at one temperature and one at another. Even more oddly, as temperatures drop, snowflakes seemed to toggle back and forth in their preference, first forming stars, then daggers. “No one knows why they should do that,” he says.

Libbrecht has a flurry of experiments related to the star vs. dagger phenomenon ready to go, but says it might take a while to finish them, partly because he struggles to attract funding for snowflake science. It’s real physics, he says, but, “if you use the word snowflake in a grant application you’re doomed right there. You can imagine if some congressman got hold of ‘Snowflake research.’”

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Sam Kean is the author of six science books, including The Disappearing Spoon and The Icepick Surgeon.


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