Question asked by Stephanie Dobson Click here to open up the snow flash movie Snowflakes are almost always six sided but that doesn't stop them from expressing their individuality. Click on the picture to explore the world of snow with my flash movie and watch a snowflake growing. If we were to list the top 8 wonders of the natural world, snow should surely be included. That such intricate, diverse and beautiful structures come from just cooling a simple molecule has got to make you appreciate the universe we live in. Snow forms in clouds where the air is saturated with water vapour and is very cold.
Snowflakes start off as tiny ice crystals that nucleate around dust particles.
As more water molecules join the growing ice crystal they build up around the first hexagon maintaining the overall shape of the crystal as it grows. The crystal not only grows outwards but upward too - otherwise snowflakes would only be one molecule thick. The rate at which water attaches to the top and sides depends on the temperature. At -5 C the top and bottom of the hexagonal crystal grow faster and you get hexagonal columns. In contrast, at -15 C the sides of the crystal grow faster and you get the more 'traditional' flat snowflake.