Why does this happen? Let's now take a look at the relationship between the cat and the pendulum from the point of view of the stationary system. Now, from the cat's point of view, the pendulum is passing from right to left above the cat. After a half cycle, the pendulum has returned to its original position, but at that time, the cat is facing the other way. The direction of the pendulum is the reverse of that of a half a cycle before, but from the cat's point of view, there is no difference to the last swing, and he is thinking "Here it comes AGAIN from the RIGHT."