An American scientist once visited the offices of the great Nobel Prize-winning physicist, Neils Bohr, in Copenhagen, and was amazed to find that over his desk a horseshoe was nailed to the wall.

The American said with a nervous laugh, "Surely you don't believe that horseshoe will bring you good luck, do you, Professor Bohr?"

Bohr chuckled. "I believe no such thing, my good friend. Not at all. I am scarcely likely to believe in such foolish nonsense. However, I am told that a horseshoe will bring you good luck whether you believe in it or not!"