Curiosities: Is every snowflake unique?

December 17, 2007

One fact we know from childhood: every snowflake is unique.

Isn’t it?

Snowflakes drawing

 

UW-Madison’s snowflake expert, meteorology professor Pao Wang, gently delivered the grim news: “Not really. I think the saying is more or less a picturesque way of saying that there are so many varieties of snowflakes, thousands of different kinds.”

Wang studies how snow and ice form into cirrus clouds — the high, gauzy clouds that play a major role in climate.

Snowflakes are all built on the hexagonal shape that occurs as water droplets freeze into crystals. The basic patterns include hexagonal plates, simple columns, thin columns, needles, and stellar, crystal or branched shapes. These shapes can build on each other to create complex, hybrid constructions that reflect the temperature and humidity conditions during formation. Warm, humid conditions are especially conducive to large, complex flakes.

But the variety is not infinite, Wang says, “You do run into some snowflakes that look exactly alike to the naked eye.” Then, as if eager to soften the injury to the one true childhood verity, he adds, “If you really want to go into detail, with a high-power microscope, you can always spot some difference, but I don’t think that’s the original intent of the saying.”