Winter Wonderland: Snowflakes Are Predictably Diverse, But Not Unique

For centuries we have marveled at the diversity of snowflakes and told our children that each snowflake is unique (just like our little darlings!)

But although each snowflake may be unique on a molecular level (“purely because there are differences in the atomic structure of the atoms making up a water molecule,” explains Penn State meteorology professor Hans Verlinde) there is new evidence that in structural terms they may be less unique than we previously thought.

In the video above, Duke professor Adrian Bejan (well-known in these pages), explains “Why Every Snowflake is NOT Unique.” From CalTech to Penn State and beyond, there are now many researchers recreating the conditions that produce snowflakes, but Bejan’s lab at Duke has been working on explaining the physics and engineering of how they grow on a purely theoretical level. The equations described in an article published this past April in NatureWhy solidification has an S-shaped history, ultimately could be used to predict how a snow crystal will grow in response to specific environmental conditions.

Bejan explains that the key thing to understand in the formation of snowflakes is that the process is fundamentally about the flow of heat. The snowflake is not growing for its own sake, or to make something beautiful or unique, but in order to distribute heat in the most efficient way. “The snowflake has an architecture that is predictable provided you recognize the principle, ” says Bejan. He identifies two principles, first that heat flows through the snowflake as it grows and second, that “ flow systems evolve to provide easier access to the currents that flow through them.” This second point is the principle of the constructal law and the basis of Bejans’s work.


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