Does it look like the red portion of this animation is rotating clockwise and the blue portion is rotating counter-clockwise?  The blue part is actually stationary, only the red part is moving.

This effect was described by Peter van der Helm in an abstract in 2006 and was a Top 10 finalist in the 2007 Best Visual Illusion of the Year Contest.

Other Optical Illusions You Might Enjoy

Peace 3D Stereogram Optical Illusion Video

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Moving Snakes Motion Illusion

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Delboeuf Illusion

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Dual Axis Illusion

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Charlie Chaplin Optical Illusion

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The Art of Optical Illusions Book

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