Why does a mirror exchange left and right but not up and down?
A lot of people seem to ask this question when they wear a T-shirt in front of a mirror. For example, imagine wearing a T-shirt with lettering on it while brushing your teeth. Why are the letters on the T-shirt reversed in the mirror, while your head appears right side up? Why does a mirror only reverse things in the horizontal dimension? Go stand in front of a restroom mirror and ponder this for a moment… For example, here is a photo of a person wearing a How Stuff Works T-shirt while standing in front of a mirror. The front of the T-shirt reads “I Gotta Know…”, and you can see that the mirror appears to reverse it: A person standing in front of a mirror. The person is on the right, the image of the person in the mirror on the left. One way to start to get a handle on this is to take a piece of paper with your name written on it. Look at it in the mirror and it will be reversed. Now turn it vertically. You will find that the lettering is reversed, but it is not upside down. That s
