Oooooh, finally a topic I'm familiar with.

The "wagon wheel effect" on film/TV has its basis in sampling theory. Do a Google search for "Nyquist's Theorem", if you want the details.

To keep it simple, you can think of filming a wheel as watching the wheel rotate while illuminating it with a strobe light flashing at 24 flashes per second. Imagine a wheel with one red spoke. If the wheel was rotating at 24 RPM, it would appear to stand still, because the red spoke would be in the exact same position each time the flash went off. If the flash was a little slower than the wheel, the wheel would appear to be rotating slowly in the proper direction because the red spoke would move slightly more than one revolution per flash. If the flash was a little fast, the wheel would appear to rotate backward, as the red spoke wouldn't quite make a full revolution for each flash.

If you have a ceiling fan in your house, you can duplicate the effect by laying on the floor and blinking your eyes while watching the fan rotate. With a little practice, you can make the fan appear to rotate forward, backward, or stand still by blinking faster or slower.

Normally, your brain/eyes do not sample signals the way film does, but vibration of your eyes will result in similar results. At a previous job where we designed Liquid Crystal Displays, we would routinely check for "flicker" by looking at the display while chattering our teeth.

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"All natural, huh? So is lightning." - Mike Rowe