The Unbelievable World of Snowflakes

Snow crystals

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"Snow crystals," Ukichiro Nakaya wrote in 1939, "may be called letters sent from heaven." The Japanese physicist spent his life studying snowflakes, eventually becoming the first to create an artificial snow crystal in the laboratory. His breakthrough led to a nuanced understanding of how snowflakes form.

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The hexagonal symmetry of snow

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Nakaya, however, was not the first scientist to take a close look at snowflakes. The process began as early as 150 BC when Chinese scholar Han Ying wrote about the "contrasts [between] the pentagonal symmetry of flowers with the hexagonal symmetry of snow."

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Scholars of history enamored with snowflakes

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Throughout history, many notable people -- including Saint Albertus Magnus, Johannes Kepler, and René Descartes -- took an interest in snow and snow crystals. Centuries of study yielded countless descriptions of snow and illustrations of snow structure.

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The first photograph of a snowflake

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It wasn't until January 15, 1885, however, that a snowflake was photographed. Using a process involving black felt backgrounds he developed on his family's Vermont farm, Wilson Bentley was able to capture the ephemeral crystals on film. He went on to take thousands of photographs of snow crystals, paving the way for advanced taxonomic studies of snow.

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Hollow-column snowflake

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Bentley described snowflakes as "tiny miracles of beauty" and snow crystals as "ice flowers." He was the first person to argue that no two snowflakes are alike. Above, a unique hollow-column snowflake.

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Rimed-crystal snowflake

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When Ukichiro Nakaya set out to photograph his own ice crystals Bentley's book, Snow Crystals, served as an inspiration. Above, a rimmed-crystal snowflake.

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Fernlike stellar-dendrite snowflake

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Nakaya photographed thousands of snow crystals. Studying these photographs allowed him to develop a systematic classification system for snowflakes. In the end, he defined 41 individual morphological types. Above, a fernlike stellar dendrite. Image credit:

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Stellar-dendrite snowflake

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His research was extended by C. Magono and C. W. Lee in 1966. Their system defined 80 different types of falling snow. Nakaya is most famous, however, for creating artificial snow crystals. This research eventually led him to the Nakaya Diagram, which describes the relationships between vapor, temperature, supersaturation, and excess vapor density in clouds. Above, a stellar dendrite.

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Sectored-plate snowflake

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Most simply, a snow crystal forms when an already supercooled cloud particle freezes. However, this event is the result of a delicate balance among the variables described in the Nakaya Diagram. This is a sectored-plate snowflake.

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Forming crystals

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The crystal forms around a nucleus, some kind of particle present in the cloud. It is not known what materials are most likely to form crystals. In the lab, Nakaya used single rabbit hairs but in nature it is thought that clays, desert dust and biological particles might be the most effective.

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Growing ice crystals

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Once a nucleus forms, it collects water droplets surrounding it. The abundance of water droplets in the cloud allows the ice crystals to grow rapidly.

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Falling crystals form snowflakes

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Once it has achieved a certain size, the ice crystal begins falling. Their mass allows them to efficiently pass through the atmosphere. As they tumble to earth, they join with other snow crystals, forming conglomerations known as snowflakes.

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The largest recorded snowflakes

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The largest snowflakes ever measured occurred in Fort Keogh, Montana, in 1887. Flakes as large as 15 inches wide were reported. Shown above is a double fernlike stellar-dendrite snowflake.

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Can two snowflakes ever be alike?

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Is Wilson Bentley's hypothesis that "no two snowflakes are alike" really true? It is technically possible that two snowflakes could be the same, if they formed under identical atmospheric conditions. In fact, identical snow crystals of very simple form have been identified. However, it is a near impossibility that two identical snowflakes would ever be created.

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The wonder of it all

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Snowflakes may no longer be a mystery of science, but they truly remain a wonder. As British Novelist Jeanette Winterson pondered, "They say that every snowflake is different. If that were true, how could the world go on? How could we ever get up off our knees? How could we ever recover from the wonder of it?" Centuries earlier, Francis Bacon had a response to a similar philosophical question. "Begin doing what you want to do now. We are not living in eternity. We have only this moment, sparkling like a star in our hand—and melting like a snowflake..."