Bruce Kalvers Incredible Shrinking and Growing Head

Posted on November 07, 2007 by Amy Tolmie
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I defy anyone who has to take school assemblies not to want this amazing optical illusion. It's a large card spiral that you spin on a power drill (not included!). Ask the audience to stare at the centre for sixty seconds and then look at someone else's head. Depending on whether the drill was rotating clockwise or anticlockwise, they will see people's head growing or shrinking. It's very very cool. A classic assembly prop. Ideas please about how to apply it.