When physicist Kenneth Libbrecht looks out over a snowy landscape, he doesn’t see a peaceful scene, he sees a laboratory. Libbrecht has traveled from Fairbanks, Alaska, to a research station above the Arctic Circle in northern Sweden to study the formation of snow crystals. His microscopic photos on display in his latest book, Snowflakes from Voyageur Press, show the intricate variety of snow crystals, and reveal the rigorous laws of nature that shape them.
Libbrecht, the chair of the physics department at Caltech, says he was drawn into this frosty work when he read a reference to the physics of ice crystal formation. “I realized I didn’t understand how these things work very well, and then I looked it up, and realized that no one understood how they worked,” he says.
He started trying to figure out why crystals grow into such dramatically different shapes in different atmospheric conditions, and, well, “It just sort of snowballed, you could say.” Now his Caltech lab spends considerable time growing “synthetic snowflakes” under different conditions (the results can be ogled on Libbrecht’s Web page). These needles are slender hexagonal columns that form at mid-humidity and relatively warm temperatures, around 23 degrees Fahrenheit.
Chinese naturalists may have discovered the six-sided nature of snowflakes over a thousand years before Europeans caught on; an ancient text dating from 135 B.C. mentions the six-pointed nature of “snow flowers.”
In 1611, German astronomer Johannes Kepler caught up with a treatise on the six-fold symmetry of snowflakes, but he was baffled as to how the intricate shapes were created. Libbrecht explains that it wasn’t until the development of X-ray crystallography in the 1920s that researchers were able to study the atomic structure of ice crystals to determine how they formed. “X-rays have about the same wavelengths as the spacing between atoms in crystals,” Libbrecht explains.
Each snow crystal forms when water vapor in the clouds condenses into ice. The molecules of H2O join together in a hexagonal lattice, and those molecules begin to clump together. The small core of a crystal has “rough” patches with many dangling chemical bonds as well as “smooth” areas; a crystal grows into a six-sided prism because the incoming molecules attach to the rough patches at six distinct spots. Those areas grow faster than the “smooth” patches, and soon a basic hexagonal shape with six points and six facets has formed.
“The geometry of the molecule gets transformed to geometry of the snowflake,” Libbrecht says, “so you can see it.”
Read more here: Discover Magazine