Still pictures that move
Ouchi illusion
Move your eyes around, or move the picture a little. What does the circle do?
It seems to float above the background and slide on its own. It is printed flat and still.
Why? Each part of your eye only sees a small patch, and can only tell which way stripes move across themselves. The bricks inside and outside point different ways, so the two parts seem to move differently. Hajime Ouchi drew it in 1977.
Picture: Drawn by Science Playground