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You may not expect to see a ball slide up a slope. But a new trick shortlisted for the 2012 Best Illusion of the Year Contest makes it seem like it's possible to defy gravity.
The models, made out of corrugated cardboard and polystyrene by Sachiko Tsuruno at Kinki University in Japan, use clever decoration to create an illusion of height. Tsurumo built two models. In the first, nothing seems out of the ordinary as a ball rolls down the incline. But Model B appears to show objects mysteriously sliding up against gravity.
Both of the models contain a gentle slope, but the shape and decoration of the model (for example the steps on either side of the slope) imply greater height between the top and the bottom of the slope. Clever camera angles also crucially conceal the fact that in Model B, the slope is actually inclined in the opposite direction to that implied by the design - giving the illusion that the balls roll against the pull of gravity. To get a better sense of how to pull off such a trick, see how a similar illusion was pulled off to win the 2010 contest.