Icicles!

Did you know they were doing serious research on icicles?  Knowing their properties is important for among other things gutter design.  Here is an excerpt from The Icicle Atlas by Dr. Stephen Morris of the University of Toronto:

“Icicles are familiar to anyone living in a cold climate. But what determines their shape and growth? Their distinctive forms emerge from the complex interplay between their evolving shape and the flow of air and water over their surfaces. These flows in turn control the release of heat needed to transform water into ice. Impurities in the water also play an important role, especially in the formation of ribs or ripples around the circumference of the icicle.”

Thus, icicles do not form from water tension and are dependent on air flow and water impurities.  The Atlas can be found on-line at:  http://www.physics.utoronto.ca/Icicle_Atlas/  It has some very interesting pictures and details growing conditions.  So before you knock down the treasure trove that has been decorating your house, have a look to see if they match Dr. Morris’ collection.  (Picture: Naturally curved icicles on the edge of a roof in Truckee, CA.  The icicles kept growing and curled as a mass of icy snow slid down the metal roof.  Credit John Larkin - NYTimes Science)