From David Longhurst, Haslemere, Surrey, UK
Before Christmas, I was trying to explain quantum theory to the grandchildren and mentioned Schrödinger’s cat, where the cat is both alive and dead before the box is opened. The children were sceptical. “Surely,” they said, “if you carefully observe the box from the outside, sooner or later the ‘cat’ will interact with one or more walls of the box and you would be able to infer its state without having to directly observe it.” So, I pointed to the Christmas tree, and said: “Under the tree is a carefully wrapped present for each of you. The present may be the gift of your dreams, or a pair of Grandma’s knitted socks. But you won’t know until you take off the wrapping and look inside.” Now that got their attention (29 November, p 36).
