THE SOUTHWORTH PLANETARIUM 207-780-4249 www.usm.maine.edu/planet 70 Falmouth Street Portland, Maine 04103 43.6667° N, 70.2667° W Founded January 1970 "The Universe creates because it can." THE DAILY ASTRONOMER Wednesday, December 30, 2015 Snowflake Astronomy Gathered in piles, they appear rather unremarkable. White, indistinct and, when lifted en masse, are far more burdensome than beguiling. Yet, if closely observed in isolation, the snowflake is seen as pure artwork. A unique and elegant configuration of ice crystals arranged hexagonally. As innumerable crystals comprise each flake, trillions upon trillions of different patterns are possible. Hence, the adage, "no two snowflakes are alike." See a few snow flake close ups on the Daily Astronomer Image Page: http://usm.maine.edu/planet/december-30-snowflake-astronomy Today's DA discusses the "astronomy" of snowflakes. We realize that one has to stretch the definition of "astronomy" and then leave it draped over a porch banister for a night to make it relate to snowflakes. However, now that the snow has finally arrived, we wanted to seize this opportunity to celebrate and explain the gorgeous spectacle of the snowflake. Why is their shape hexagonal? Why are their shapes unique? The first requirement for a snow flake to form is nucleation. A frozen water droplet must attach itself to a dust or pollen particle. After it accumulates sufficient amounts of ice, the weighty nucleus descends through the atmosphere and collects other droplets during the fall. This prolonged descent is chaotic. No two paths are the same, hence the snowflake's uniqueness. Ice collects along six "spokes" radiating away from the center. This hexagonal design reflects the water molecule's internal structure. Like a fractal that infinitely replicates the same pattern, a snowflake is a macroscopic reproduction of a microscopic configuration. Apart from the falling flake's pathway, another variable is temperature and humidity, both of which change during the descent. Warmer sub-freezing conditions, around 25 degrees F, produce needle-like arms, whereas colder air around 0 F tend to produce plate-like crystals. Even though a snowflake's local conditions change during its formation, at any given moment, the conditions along a single, small snowflake are constant, so the flake will always exhibit an elegant symmetry, as evidenced by the images shown within the link above. As they consist of ice, snowflakes are clear. We perceive them as white because they reflect light back to us. Consequently, freshly fallen snow appears almost blindingly bright under sunlight. A single snow storm can produce countless snowflakes, the vast majority of which go unobserved. They are tucked under shrouds or create the glittering membrane of vast snow fields. The delicate structures and complex crystals sculpted by Earth's winds remain unknown and therefore unappreciated. We know, however, that embedded within all snow piles are myriad miracles of natural sorcery.