This is an old paradox about a mirror. When you look into a mirror it reverses the side your hair is parted on. The image in the mirror is left and right reversed, but not top and bottom. Why?
Another way to look at the problem is to lie down on your side and look into the mirror. Your hair will still part on the left side. Your left and right used to be respectively up and down and the up and down were previously right and left. So, how did the mirror 'figure out' what you were going to do.
English vision scientist Richard Gregory offers an experiment using a match and its box. Hold a match horizontal and parrallel to a vertical mirror. What happens? When the head of the match is to the right, its head is also to the right. It is not left-right reversed. However, the writing on the matching, when viewed in the mirror, is left-right reversed. So, it appears as if the match and it's box behave differently! Why is this?