It’s snowing in Boston today. While I was out for a walk this morning I noticed that many of the snowflakes that were crashing into my jacket were perfectly symmetrical, six-pointed stars with delicate branching on each point. I managed to snap a picture of one of these snowflake specimens just after it alighted on my coat sleeve, before it melted away.
The most recent episode of RadioLab features a story about snowflakes. If you haven’t heard it yet, it’s worth a listen. We often think of snowflakes in terms of the perfect, crystal forms featured on holiday cards and sweaters, but the RadioLab story reveals that these perfect-looking snowflakes are actually very rare in nature. It turns out that most snowflakes aren’t anything special to look at. They’re often lumpy and asymmetrical. Kenneth Libbrecht, a scientist featured in the story who studies snow crystal formation, claims that he can look at thousands of snowflakes before finding one that is completely symmetrical. He explains that conditions have to be just right for perfect snowflake formation: there must be minimal wind, and it has to be cold enough that the snowflakes don’t clump together as they fall. It just so happens that these ideal snowflake-forming conditions exist today in Boston.
An article about snowflake science accompanies the RadioLab piece. It features Kenneth Libbrecht’s microscope photos of some perfect and not-so-perfect snowflakes.