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No. 127: Jan-Feb 2000

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Shadow Dance Of The Gnats

An curious phenomenon was reported recently to the New Scientist.

"I travelled to Hungary to observe the recent total solar eclipse. About five minutes before totality, my wife and I noticed many curved shadows about 3 centimetres long dancing on a white paper lying on the ground, formed by a swarm of gnats. The shadows were exactly the same shape as the remaining bright portion of the Sun, by then only a thin arc of light. Why?"

This phenomenon is not anomalous but it is entertaining. It is the reverse of the pin-hole-camera effect often seen during total eclipses. People standing in the shadow of a tree will see many bright arcs on the ground -- images of the sun being eclipsed. The interstices between the tree's leaves act as pinholes. The phenomenon happens in reverse when pin-holes are replaced by "pins"; that is, small opaque obstructions, such as gnats.

(Scott, Andrew, and Diebold, Mike; "Shadow Dance," New Scientist, p. 93, October 30, 1999.)

From Science Frontiers #127, JAN-FEB 2000. � 1997 William R. Corliss