The real scientific reasons why everything always goes wrong. Start looking for Murphy's Law, and you'll find it everywhere. Buses go round in threes, the queue you join always goes slowest, when your hands are full your nose starts to itch, you think of 10 important things to remember just as you are falling asleep . . . Can there ever be a rational explanation? The answers turn out to be one part scientific to three parts psychology. The world has changed a lot in the last 4000 years, but our brains haven't. So, again and again we find our reactions are just plain out of date. Why do you take the same wrong turning every single time? Why, when you lose something, do you keep looking in the same place over and over? And why is it suddenly there the twentieth time you look?