A motionless disk
Hold the disks on both sides of the mirror.
Tilt your head to the left to look in the mirror. The mirror image of your left-hand covers your view of your right hand.
Without changing the position of your head, move the disk to the right.
How it works
The movement of the disk surprises and confuses you because your brain expects to see movement but doesn’t.
The idea for this device comes from the Portland Science Centre in United the States of America.