Thaumatrope

optical illusion · spinning toy · history of animation

Two pictures become one. A thaumatrope has different pictures on each side of a disk. When you spin it super fast by twirling the strings, your brain sees both pictures at the same time instead of one at a time.

Your eyes play tricks. This happens because your eyes hold onto an image for about one-eighth of a second after it disappears. Scientists call this lingering effect visual persistence, and it's what makes the magic happen.

Invented in 1825. The thaumatrope is one of the earliest toys designed to show how our eyes and brains work together. It came before movies and helped people understand that moving pictures are actually just still images shown very quickly.

Simple but clever. You can make a basic thaumatrope with just a cardboard disk, two strings, and a marker. Twist the strings between your fingers fast, and the pictures blend before your eyes.