March 1, 2010

It has been snowing for days where I live in New York State. The roads were clear by Sunday morning and we took a drive and photographed the incredible sights, with wet, heavy snow coating everything.

This photograph got me thinking about a fascinating exception that exists in nature. Most non-metallic substances contract as they get colder. Not water, though. Water contracts until it gets down to about 39 degrees F.  Then it begins to expand until it freezes and turns into ice. So why is that important? Well, it means that when water turns to ice, the ice forms at the surface rather than at the bottom of a pond, lake or ocean.  The warmer water sinks. That’s why ice floats. And that’s one of the reasons that living things in ponds and lakes can survive the winter at the bottom where water is still liquid and not frozen solid. 

Posted by: Seymour Simon

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