By Andrew Bridges, AP science writer
PASADENA, Calif. Ken Libbrecht is perhaps the flakiest man
going in the rarified world of physics.
Working in a small laboratory at the California Institute of
Technology, Libbrecht routinely matches Mother Nature in her skill in churning out a
product as beautiful as it is ephemeral: the snowflake.
Unlike Libbrecht's other pursuit the search begun by
physicists in Albert Einstein's day for gravity waves, the elusively mysterious ripples in
the fabric of space and time snow-crystal growing can satisfy in minutes, if not
"There is a lot of instant gratification," said
Libbrecht, as he adeptly demonstrated his technique on a recent morning, cranking out
multiple crystals, each as unique as any found cascading from a cold, winter sky.
Libbrecht, chairman of the powerhouse university's physics
department, began studying snow crystals snowflakes are actually clumps of snow
crystals about five years ago.
The fruits of his labor are stunning: his Web page contains
countless images of snow crystals. He and Midwest photographer Patricia Rasmussen plan a
book to feature the most photogenic crystals they've spied in nature and the lab.
But the work is also valuable science. The physics of snow crystal
morphogenesis how the patterns grow largely remains a mystery.
"I just became intrigued by the physics and that we don't
understand how it works how ice crystals grow," said Libbrecht, whose
upbringing on a North Dakota farm gives him an impeccable cold-weather pedigree.
Snow has captured the interest of scientific minds since at least
Johann Kepler, whose 1611 work, "A New Year's Gift, or On the Six-Cornered
Snowflake," was the first treatise to ruminate on why crystals always display a
Scientists know that snow crystals form from water condensed from
its gaseous state, each growing around a tiny nucleus, typically a speck of dust.
As more and more molecules of water attach to the growing crystal,
they do so selectively, giving it its distinctive, hexagonal shape.
On the subject of whether any two snowflakes are identical,
Libbrecht said crystals are like human faces. Stand back far enough, he said, and any two
appear identical. Come closer, though, and their variety shines through.
What scientists don't know is why crystal growth rates vary so much
as a function of temperature and humidity. It turns out that each tiny crystal, seemingly
so serene, betrays a life that is incredibly dynamic, as each totters on the brink of the
"Thermodynamically, it's an extraordinarily active material,
so it's always changing," said Sam Colbeck, a retired geophysicist from the U.S.
Army's Cold Regions Research and Engineering Laboratory in Hanover, N.H., where he was an
expert on how crystals grow in snow cover.
Following on Kepler's heels, Libbrecht has developed the means to
study crystals firsthand, even on winter days when the Pasadena campus of Caltech basks in
the Southern California sunshine.
He is one of what's perhaps just a handful of physicists and
meteorologists who work in the field and that's fine by him.
"I've worked in fields that are crowded before and I prefer
not to," Libbrecht said.
Libbrecht grows his crystals in a small, insulated box made of
plastic foam and glass, sealed with silicone caulk.
The box is cooled at the bottom and heated at the top, creating
within a stable temperature gradient. A piece of felt, soaked in water, creates the moist
air from which growing crystals snag water molecules.
A piece of two-pound test line, stretched vertically, crosses the
various gradients. That allows crystals to grow fastest at whatever point on the fishing
line that is, Goldilockslike, just right.
"It's not toxic or messy. And it's cheap," Libbrecht
said. "Experimentally, I love the stuff."
During a recent demonstration, Libbrecht showed off three clumps of
crystals, spaced fairly evenly along the line. The distribution illustrates how
temperature-sensitive they can be.
At 28 degrees Fahrenheit, the crystals grow as plates. At 23
degrees, it's columns or needles. At 5, it's back to plates. If temperatures dip as low as
minus 20, it's columns again.
"It sort of varies, plates to columns, to plates to columns,
to plates as a factor of temperature," Libbrecht said.
In the 1930s, Japanese physicist and snow crystal pioneer Ukichiro
Nakaya was the first to recognize that the shape of each crystal, when deciphered, betrays
the conditions under which it was born. "Hieroglyphs sent from the sky," Nakaya
called the crystals.
"The crystals will tell you very neatly what the temperatures
are," Libbrecht said. "That one string tells you a wonderful story."
Replacing the string with a section of tungsten wire, the story
becomes even more dramatic.
Libbrecht first puts 2,000 volts of electricity on the wire. That
creates a strong electrical field at the tips of whatever ice crystals are already present
and encourages them to grow further.
Magnified by microscope, the crystals can be seen to surge in
length, growing 10 times faster than normal to form slender, hexagonal "pencils"
"They just shoot out in long, thin needles," Libbrecht
Cutting the voltage and dropping the temperature, the crystals
revert to more normal growth patterns.
It takes Libbrecht just a few minutes to grow flowers of ice,
complete with delicate crystals sprouting from the stalklike columns. "Designer
crystals," he calls them.
On a recent morning, one of the stalks of a just-grown example
began to droop, dropping into view a perfect, star-shaped crystal.
"Oh, look at that. It doesn't get any better than that,"
The trick, discovered by luck, is the silicone caulk that holds the
ice box together. Something in the volatile vapor it gives off modifies the growth of the
Next door, a larger, more sophisticated tank allows the 43-year-old
to create miniature blizzards and then separate out individual crystals to clock
their individual growth rates.
"They're telling us volumes," he said of his snow crystal
research. "I just don't know what it means yet."
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