When a vehicle is in forward motion, why do the hub caps/wheels look like they are rotating backwards?

Question

When a vehicle is in forward motion, why do the hub caps/wheels look like they are rotating backwards?

Answer 1

At first I thougt that this would only look in a film that way.

But lately I saw it in real. There it came because the screws were like a mirror so shiny, and that gave the same effect as in the old film projectors.  Somewhat the same effect as the early days Nabokov's-disk , the first TV experiment.

Could also be that you saw it in stroboscopic light.

Answer 2

The vehicles wheels are actually turning faster than your eyes can register. Your brain compensates for this by making its best guess. If you watch the wheels of an F1 car, you will notice that initially, the wheels appear to be rotating clockwise, then, they appear to be rotating anti-clockwise. Then, as they get faster, they swap back to rotating clockwise again. This is because the wheels are turning so fast now, that your brain is compensating for it even more poorly. For example, if a wheel has four struts, A, B, C & D, initially, you will see them turning A, B, C, D. Then, as the vehicle gets faster, your brain will begin to "skip". So you will see A, C, D, B as your brain is skipping one strut. As it gets even faster, you will see A, D, C, B, as your brain skips out even more struts.