The Snowflake Maker
It is 94 degrees outside Ken Libbrecht’s Caltech lab. Inside, within refrigerated coolers, tanks and glass boxes, it is a cool 5 degrees, and Libbrecht is busy making snowflakes.
For the past 16 years, Libbrecht has lived in Pasadena, toiling at high-profile astrophysical pursuits. But he was raised on a farm on the snowy eastern plains of North Dakota and has come to realize that the same snowflakes he once captured on his tongue as a child may--like the gravity waves coursing through the universe that he also studies--hold the key to some of nature’s most basic problems.
“It popped into my head one day a few years ago--the physics of snowflakes,” said Libbrecht, head of the physics department at Caltech and a professor there. “You never lose your roots.”
The physics--and sheer beauty--of snowflakes have been like a scientific siren to Libbrecht, luring him away from a $365-million project to detect gravity waves, the ripples in the fabric of space and time produced by the most violent events in the universe.
Instead, he’s moved toward the one-man, tabletop research that is modern snowflake science. Though it started out as a small sideline--”comic relief,” said Libbrecht--he now spends half his time on snow. “Recently, I pulled out all the stops,” he said. “No more fooling around with little experiments.”
The central question is how staggeringly complex and symmetrical snowflakes arise spontaneously from simple physical systems. As Libbrecht writes in his snowflake Internet site (https://www.its.caltech.edu/~atomic/snowcrystals/), “Where is the creative genius that produces these miniature masterpieces of frozen water quite literally out of thin air?”
The work is part of a larger field of physics called pattern formation, which has matured in the last 20 years, said Herbert Levine, a professor of physics at UC San Diego who studied snowflake patterns in the 1980s and has since moved on to study the complex forms produced by living organisms such as bacteria.
“There are two reasons people study this,” he said. “One reason is just aesthetic beauty. We’re just amazed that processes in the world can create patterns we find so intrinsically beautiful.” The research, he added, can also help solve practical problems. Learning about instabilities in pattern formation, for example, can help aircraft engineers avoid weak spots as they solidify metal into a wing.
Libbrecht faces a flurry of questions: Where do the various prisms and plates and needles come from? Why are they symmetrical? Why do snowflake needles only grow at certain temperatures? “How can we not know that?” asks Libbrecht. “It’s the 21st century.”
Some snowflake basics are known. The ice crystals have, after all, intrigued some of the world’s finest minds, from Kepler to Descartes.
Snowflakes are ice crystals, water vapor that condenses out of cold air around something like a piece of dust. The initial crystal is a hexagonal prism, a shape dictated by ice’s molecular structure. The prism spouts six arms because its points stick out and collect more water molecules from the air.
The first systematic study of snow did not occur until the 1930s, when Japanese nuclear physicist Ukichiro Nakaya turned his attention to snowflakes. Nakaya, who called snowflakes “hieroglyphs sent from the sky,” was the first to catalog the major snow crystal types and the first to grow them artificially in the lab--atop dried rabbit hairs. He found that snowflakes grow into different shapes at different temperatures and humidities.
In the 1980s, Levine and researchers at a host of other labs helped solve a key snowflake problem, developing the first mathematical explanation for how certain snowflake crystals grow.
But snowflakes have not yielded the rest of their secrets easily. For example, at 28 degrees, snowflakes form fat ice plates. At 23 degrees, they form needle-like columns. At 5 degrees, they form thin plates. At 22 below, it’s columns again. “It’s puzzling,” Libbrecht said.
He’s tackling the problem as Nakaya did--but with a bit of high-tech help. Instead of using rabbit hairs, Libbrecht grows flakes with lasers, electric fields, ultra-clean tanks and triple-insulated glass boxes with precise temperature gradients where he can custom design wintry climates.
Here, Libbrecht carefully crafts flakes under different conditions. The flakes appear in an instant, growing before one’s eyes, their every detail magnified on a television screen. “A classic stellar dendrite,” says Libbrecht, as a shimmering ice star appears. “That’s everybody’s favorite form.”
Then he unceremoniously taps the needle holding the icy work of art. It shatters and disappears. To Libbrecht, it’s just an opportunity to grow a new flake. “We can make more,” he tells a disappointed visitor. “They’re cheap.”
Libbrecht’s “designer crystals” are shaped like crowns, shot glasses and chandeliers. He moves snowflakes as they develop, growing long needles with stars on each of their ends, like tiny ice bouquets. Some have long, wavering needles growing from their midst, recalling the mutilated “Edward Scissorhands.” “We call those Tim Burton flakes,” Libbrecht said.
One key in snowflake patterns, although Libbrecht admits he’s some way from figuring it out, is in the quasi-liquid, disordered layer on top of the more orderly ice crystal. He’s also looking at how the thickness of crystals changes as the temperature does. And he’s investigating the role of different atmospheric pollutants and pressures on flakes.
Libbrecht has, of course, tackled the most famous of all snowflake questions. Of the septillion snowflakes that fall each year (septillion: that’s a 1 with 24 zeros after it), are any two alike? As with most things in modern physics, there is not a simple answer.
Many of the simple crystals that first form in air are just alike. But the complex crystals that form after fluttering through myriad atmospheric conditions are never alike. “Once they get complicated, they’re like people,” Libbrecht said. “No two are the same. Because like people, they have different paths.”
Though he seems to conjure the flakes out of thin air, getting the setup to work was not easy. “It’s very touchy,” he said. “A lot of it is trial and error.” When he tried to rid the tanks of contaminants, for example, he found it harder to grow the flakes. It turned out that one contaminant--vapors from an off-the-shelf silicone adhesive--helped flakes grow.
Though giving up “Big Science” has its costs--a loss of million-dollar grants and a steady stream of graduate students--it has its rewards as well. Libbrecht is having a lot of fun. “I’m really jazzed,” he said. “I was willing to give up having big groups and big results if I could stay in the lab,”
But Libbrecht is also willing to leave the lab. He’s planning a snowflake field trip back to the family farm near Fargo to study snowflakes in the wild--and on his windshield. Although his family thinks he’s lost his mind to leave the Golden State in winter, others think Libbrecht is just as crazy to grow snowflakes in sunny Southern California.
Libbrecht disagrees. “Everything else is phony around here,” Libbrecht said. “Why not snowflakes?”
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Usha Lee McFarling can be reached at usha.mcfarling@latimes.com
