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This week's LabZone activity
March 8, 2006
New Moon?
Bet you can make a full moon shrink!
THE SETUP:
This illusion has two parts: (1) Look at a full moon just after it has arisen. The moon should be near the horizon. (2) Next, view the moon through a little window you make from the space between the thumb and forefingers of each hand held together. View only the moon. Don't let any of the objects on the ground enter your little viewing window.
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| Commander John Bortniak, NOAA Corps |
THE FIX:
The "shrinking moon" illusion has been known for hundreds of years. Although the ancients realized the moon seems much smaller when it is high in the sky, the reason behind this illusion still is not completely understood.
Scientists have measured our perceptions, and we see the moon as 2 1/2 to 3 1/2 times larger near the horizon than high in the sky. The best theory to explain this phenomenon is that the moon appears larger when it is near identifiable objects. When you remove these visual cues by blocking them out with your fingertips or by waiting until the moon is high in the sky, the moon appears to shrink. Instantly.
Reprinted with permission from Bet You Can! Science Possibilities to Fool You by Vicki Cobb (www.vickicobb.com) and Kathy Darling. Text copyright © 1983 by Vicki Cobb and Kathy Darling. Published by Avon Books.
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