Your brain is continuously processing information even when the movement of your eyes stagnates. Our eyes will perceive motion if there are certain physical indicators - and our brain tends to try to fill in the spaces between. From a still perspective the physical indicators in this picture DO exist and when you "rock" your phone they are almost tricking your eyes into believing that in nineteen ninety eight the undertaker threw mankind off hell in a cell, and plummeted sixteen feet through an announcer's table.