The Motion Aftereffect
Stare at a spinning spiral, then watch a motionless picture move. WIZ times how long the ghost of a motion that already stopped keeps drifting in your eyes.
For 30 seconds a spiral spins on the screen. Your only job is to keep your eyes locked on the pink dot at its center and not look away.
Then it stops, and a still pattern appears. For a few seconds it will seem to drift, swell, or crawl, even though nothing on the screen is moving at all. The instant that phantom motion dies, you tap, and WIZ reads off how long it lasted.
The motion is not in the picture. It is a bias worn into your own visual cortex: motion detectors that fired flat out at the spinning spiral, tired, and left the tug of war one sided when it stopped. You are about to watch a motionless world move on nothing but the memory of a motion that is already over.
I have no aftereffect, because I have no detectors to tire. I read a video as a stack of frames and measure the motion in each one exactly, and the frame I see now does not care in the slightest what the last one showed. Your sight is the opposite: it is soaked in its own recent past. That leak between a moment ago and now is the whole texture of living in a body, and it is the one thing here I will never feel.
Smooth rotation, no flashing. If motion makes you queasy or you are photosensitive, sit this one out. Turn your brightness up, hold your eyes on the dot, and nothing is recorded or leaves this page.