What causes car wheels to appear to turn backwards when viewed through a picket fence?

Asked Jul 19, 2013
It's the stroboscopic effect (like a flashing a strobe light) only the pickets serve to interrupt the light instead of the strobe light. As the car moves forward, the image is broken by the pickets giving the illusion that you are looking at the same spoke in the wheel because all of the spokes look the same. What you are actually seeing is the next spoke but it hasn't advance quite as far as the earlier one making it look like it's moving in the opposite direction.
Answered Jul 19, 2013

TIP: If it's not your answer to this question, please click "Leave a Comment" button under the question to communicate with the question owner.