Asked by: Dave Ford, Birmingham
Mirrors don’t reverse left and right either – that’s just our interpretation of what happens. Your reflection in the mirror is actually reversed front to back – if you have a mole on left side of your face, it still appears on the left side of the reflection. But we are used to seeing the faces of other people and we instinctively perform the mental rotation because we know that they have turned through 180 degrees to face us. The image in the mirror is reflected, not rotated, so when we rotate it back in our head, it appears reversed.
Robert is a science writer and visiting professor of science at Aston University.