The Wagon Wheel Effect is a phenomenon in which a spinning wheel appears to move backward or forward when viewed from a certain angle. It is caused by the persistence of vision, which is the phenomenon in which the eye retains a visual image for a fraction of a second after the source has
From Wikipedia
The wagon-wheel effect is an optical illusion in which a spoked wheel appears to rotate differently from its true rotation. The wheel can appear to rotate more slowly than the true rotation, it can appear stationary, or it can appear to rotate in the opposite direction from the true rotation.