Dear Mr. Skilling,
With gravity pulling everything toward the Earth, how do clouds stay in the sky?
James Petros (age 6), Elmhurst, Ill.
Dear James,
The romantic notion that clouds float in the sky, borne gently along by the wind, is as old as the ages, but the truth is that it’s incorrect: Clouds don’t float! The tiny droplets of water and crystals of ice of which clouds are composed actually do respond to the downward tug of gravity. They do fall–only one or two feet per minute, but they do fall.
And that leads to your question: If cloud particles fall, what keeps clouds up? The answer is that clouds remain aloft because they exist only in an environment of rising air. The rising motion is sometimes very gentle, as in stratus clouds, or it can be violent, as in cumulonimbus (the thunderhead).
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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN-TV News at noon and 9 p.m.
WGN-TV meteorologists Steve Kahn, Richard Koeneman and Paul Dailey plus weather producer Bill Snyder contribute to this page.
