In celebration of the first snowfall I’ve seen this season, here are some gratuitous pretty pictures of snowflakes – taken using an electron microscope at the Electron Microscopy Unit at the Beltsville Agricultural Research Center, Maryland.

I do love snow. I’ve always loved how things like snowflakes can form in such seemingly precise patterns. They always have hexagonal (or occasionally, trigonal) symmetry, and this baffles a great many people. The question I’ve heard asked is how a snowflake knows what shape it should form? The answer is simple chemistry. Water molecules, when they freeze into ice at atmospheric pressures, form into nanoscopic hexagonal arrangements. Those seemingly vanishingly small hexagonal nanocrystals continue to grow and grow, all the while still retaining their intrinsic hexagonal pattern – due to the points in the ice crystals which have the lowest energy (making them the easiest places for new water molecules to stick to). Eventually, you have a tiny object with an overall hexagonal symmetry, which is large enough to be seen with the naked eye. In other words, a snowflake.

Did I mention I’m also a big fan of hexagons…?

With a tip of the hat to polymath4ever.