In 1988, a cloud scientist named Nancy Knight (at the National Center for Atmospheric Research—let’s not defund it) took a plane up into the clouds over Wisconsin and found two simple but identical snow crystals, hexagonal prisms, each as like the other as one twin to another, as Cole Sprouse is like Dylan Sprouse. Snowflakes, it seems, are not only alike; they usually start out more or less the same.
Yet if this notion threatens to be depressing—with the suggestion that only the happy eye of nineteenth-century optimism saw special individuality here—one last burst of searching and learning puts a brighter seasonal spin on things. “As a snowflake falls, it tumbles through many different environments,” an Australian science writer named Karl Kruszelnicki explains. “So the snowflake that you see on the ground is deeply affected by the different temperatures, humidities, velocities, turbulences, etc, that it has experienced on the way.” Snowflakes start off all alike; their different shapes are owed to their different lives.