Game time

# Gravity-defying balls channel M.C. Escher

Four balls appear to roll uphill in an uncanny creation by Japanese researcher Kokichi Sugihara. The prize-winning illusion is one of many examples of what Sugihara calls "impossible motion."

If you think your eyes have played tricks on you before, check out this video. It shows four little wooden balls that seem to defy gravity by rolling uphill on four slopes built of cardboard. The balls seem drawn to the slopes' peaks, as if by magnetism. That's why this bizarre creation, by Kokichi Sugihara of the Meiji Institute for Advanced Study of Mathematical Sciences in Kawasaki, Japan, won the 2010 Best Visual Illusion of the Year Contest.

The illusion is entitled "Impossible Motion: Magnet-like Slopes." When turned around, it becomes apparent that the slopes are actually pointing down, not up, and gravity is acting on the balls.

(Credit: Kokichi Sugihara)

Sugihara, a professor of engineering, explains how the illusion works: when we look at the object, our brains perceive all the slopes' support columns as being vertical, and the longest column as being the tallest. But, in fact, the opposite is true.

Sugihara discovered similar illusions while doing research into how computers interpret 2D drawings as 3D objects. He was checking software he developed by testing it with pictures of geometrically impossible objects, fully expecting the software to reject them. But the program accepted some drawings, leading Sugihara to try to create them in real life.

The photo at right, for instance, shows a set of Escher-like infinite stairs that Sugihara made from paper. A related video about making impossible objects like a Penrose triangle, which is ostensibly formed by three straight, square bars meeting at right angles. Sugihara has experimented by placing rods into some of these objects, and getting one end of the rod to come out where it ought not to. He calls these tricks "impossible motions" (see video here).

The vantage point, lighting, and the way our brains interpret the scenes in Sugihara's little shows are important in pulling off these visual prestidigitations. Would they work in the real world? Sugihara hopes to create sculptures of impossible objects in public parks in Japan, and even playground slides on which kids appear to defy gravity. Maybe Escheresque jungle gyms would get kids to put down their PSPs and look around. Or maybe not.

(Via Pink Tentacle)

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