Tired eyes
Motion aftereffect
Make the video full screen and stare at the middle until it ends (a minute). Then look at your hand or someone’s face. What happens?
It seems to stretch and move.
Why? The cells that sense motion in one direction get tired, so still things look like they’re moving the other way. After watching a waterfall, the rocks beside it seem to drift upward; it’s also called the waterfall illusion.
Picture: Paulnasca at English Wikipedia, Public domain · Wikipedia(opens in a new tab)