 OMG guys, did you see the wheels turn backwards instead of forwards? Guys, this effect is an optical illusion known as the stroboscopic effect. To understand this phenomenon, let us consider a scenario. Say that there is a hypothetical wheel which has only one spoke. This wheel is rotating clockwise 24 times a second. And this wheel is shot by a camera which is capturing at the rate of 24 frames per second. Assume that the camera captures the frame each time the spoke is at 12 o'clock position. Now when you view this movie, won't the spoke always appear to be at 12 o'clock position? And this is because the angular frequency of the rotation and the FPS of the camera is exactly the same. Now, if the wheel slows down slightly, the camera will shoot the spoke before 12 o'clock position, let's say at 11 o'clock position. Now if you watch this film again, you'll feel like this spoke is rotating in an anti-clockwise rotation compared to its initial position, giving you the feel that the wheel is actually rotating backwards instead of forwards.