خطای دید

 The first time I saw these optical Pictures I thought they were moving but they are not, if you look at them closely they are drawn perfectly that it creates an illusion that looks like they’re moving in circles. In fact these pictures are built from an Optical Imagery graphics making our eyes and mind confuse that creates a continuous motion out of the steady object.

  http://www.myce101.com/amazing-optical-illusion-that-creates-hallucination.html