by Kate Bannan on Tue, December 13, 2011
With winter just around the corner, can snow be far behind?
We’ve all heard that no two snowflakes are alike, but what do we really know about them?
Snowflakes always have six sides. Their form and shape depends on temperature and moisture. Snowflake shapes fall into six main categories: plate (flat), column, stars, dendrite (lacy), needle and capped column. When it is extremely cold, snow becomes fine and powdery and the snowflakes’ design becomes simpler, usually needle or rod shaped. When the temperature is close to freezing point, snowflakes become much larger and more complex in design.
Snow crystals form in clouds when the temperature is below freezing and are created by water droplets freezing on small ice particles. As an ice crystal drops through the cloud it bumps and knocks others and becomes a snowflake. This process of bumping others, along with melting and re-freezing aids the creation of their complex design. The air that the snowflake drops through has to be under freezing or the snowflake will simply melt and turn into rain.
Physicists working on the National Spherical Torus Experiment (NSTX) at the Princeton Plasma Physics Laboratoryare working to solve one of the grand challenges of magnetic fusion research: reducing the effect that plasma has on the walls of the tokamak. By using a "snowflake" diverter, a novel magnetic diverter named for its shape, scientists have improved heat and power handling by reducing the interaction between hot plasma and the cold walls surrounding it.
You can find more about snowflakes, tokamaks and fusion via Science Accelerator, a gateway to science, including R&D results, project descriptions, accomplishments, and more, via resources from the Office of Scientific and Technical Information (OSTI), U.S. Department of Energy.
This year in the US, the first day of winter is December 22. Let it snow!