Legend has it that the physicist Niels Bohr had a horseshoe hanging above his door. A colleague asked him why, to which he responded, “it’s for luck.” The colleague then asked him if he believed in luck. Bohr reassured him that as a scientist he did not believe in luck. Puzzled, the colleague asked again why Bohr had the horseshoe hanging above his door. Bohr responded, “I’m told that you don’t have to believe in order for it to work.”