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June 27, 2008

Strange But True!

Q. How did sightings of the Loch Ness monster (Nessie) go the way of old sightings of mermaids and mermen?

A. Likely all were mirages, with light rays refracted from their normal straight path by layers of air of varying temperatures (same as the common highway “oasis mirage”), says Jearl Walker in “The Flying Circus of Physics.” Under the right conditions, a log floating in water may seem to extend upward like the neck of a monster and to oscillate as if swimming. Conditions are ideal for such a mirage when cold water cools the air just above it while sunlight warms the higher air. Then some of the light is refracted downward but only slightly, so the viewer must be near the water level to intercept the light.


 
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