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One in a Septillion

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Photograph of snowflakes, Robert Libbrecht,

While winter has not yet officially arrived, some of us have been given a taste of the season to come with cold temperatures, frigid winds, frost, ice, and even powdery snow.

When I think of winter, I think of twinkling ice crystals falling from the sky and colliding to become intricate snowflakes. Each winter there are about a septillion (trillion trillion) snowflakes that fall from the sky.

 Around this time of year, we frequently receive the question Is it true that no two snowflakes are alike? The simple answer is yes. The probability of finding two snowflakes which are exactly the same in molecular structure and appearance are extremely minute. Of course there are snowflakes that appear similar, but when you take a closer look you see the differences.

 One of the first studies of ice crystals was from the young Johannes Kepler, who was going to his benefactor’s New Year’s Eve party without a gift. He writes:

 Just then by a happy chance water-vapour was condensed by the cold into snow, and specks of down fell here and there on my coat, all with six corners and feathered radii. ‘ Pon my word, here was something smaller than any drop, yet with a pattern; here was the ideal New Year’s gift for the devotee of Nothing, the very thing for a mathematician to give, who has Nothing and receives Nothing, since it comes down from the heavens and looks like a star (A New Year’s Gift, p.7).

 This event led Kepler to write about why snowflakes have six corners in  A New Year’s Gift, or On the Six-Cornered Snowflake, published in 1611.

Oringial Wilson Bentley snowflake image from the Jericho Historical Society

In 1885 Wilson Bentley, also known as the Snowflake Man, took the first photomicrographs of snow crystals using a microscope and a camera. Duncan Blanchard, in his article  Snowflake Man published in Weatherwise (1970) called Bentley “America’s First Cloud Physicist.”  Through his work he began to deduce that air temperature may affect the structure and form of snow crystals.  He published over 60 articles of his work, along with the book Snow crystals (1931, 1962), which contains over 2400 of his photographs.

Starting in the 1930’s,  Japanese scientist Ukichiro Nakaya, who also took photomicrographs of snowflakes, went a step further and created artificial snow crystals in his laboratory to better understand the meteorological and environmental conditions that affect the structure and form of snow crystals. He published his findings in Snow Crystals: Natural and Artificial (Harvard University Press, Cambridge, 1954), as well as creating the first systematic classification scheme of snowflakes.

Today, Cal Tech physics professor Robert Libbrecht, who studies the physics of snowflakes and the molecular dynamics of snow crystal growth, continues the tradition of photomicrography of snow crystals and flakes. His state of the art photomicrography set up and color lights produce striking images of snowflakes never seen before. Not only have his images graced the covers of many popular science magazines and books,  but also his images were selected for the 2006 United States holiday season stamp.  Check out his Snowcrystals website and see for yourself.

For more information about snowflakes see our guide on Snow: Flakes and Crystals, which features a selected list of book titles, articles, and websites.


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