Tomorrow morning, I confidently expect to awake and find the elegant spires and haphazard Victorian rooftops of Dorchester, transformed by the silent fall of billions of snowflakes.
An individual snowflake is itself an agglomeration of up to several hundred ice crystals, and a cubic foot of snow can contain roughly one billion crystals of ice. Conventional wisdom suggests that no two snowflakes are alike, but in the case of the simplest type of snowflake, this isn't actually true. According to Dr Karl Kruszelnicki:
In 1988, the scientist Nancy Knight (at the National Center for Atmospheric Research in Boulder, Colorado) was studying wispy high altitude cirrus clouds. Her research plane was collecting snowflakes on a chilled glass slide that was coated with a sticky oil. She found two identical (under a microscope, at least) snowflakes in a Wisconsin snowstorm.
As Dr Karl points out, these snowflakes were simply hexagonal prisms, rather than the more complex type of snowflake-crystal, which exhibit the classic six-fold spoked structure, seen in the picture above. And, as both Dr Karl and Kenneth G.Libbrecht of Caltech point out, if two such snowflakes are deemed alike, then they are only alike at the level of resolution provided by a microscope.