Most of you likely have observed the wagon-wheel illusion in real life. It is an optical illusion in which a wheel with spokes appears to rotate differently from its actual rotation. If you’ve not observed this, I like the example and explanation provided at the link below. Reportedly, the illusion was first noted during the playback of old movie films in which the wheels of a forward-moving vehicle appear to slow down or even roll backwards. Some have noticed this in recordings of helicopter rotors and aircraft propellers. The effect is said to be a result of temporal aliasing. It can also often be seen when a rotating wheel is illuminated by flickering light. These forms of the effect are known as stroboscopic; the original smooth rotation of the wheel is visible only intermittently.