Somebody once asked Niels Bohr why he had a horseshoe hanging above the front door of his house. Surely you, a world famous physicist, can't really believe that hanging a horseshoe above your door brings you luck? Of course not, Bohr replied, but I have been reliably informed that it will bring me luck whether I believe in it or not.

In my youth I regarded the universe as an open book, printed in the language of equations, whereas now it appears to me as a text written in invisible ink, of which in our rare moments of grace we are able to decipher a small segment.

Adolescence is a kind of emotional seasickness. Both are funny, but only in retrospect.

The principle mark of genius is not perfection but originality, the opening of new frontiers.

Courage is never to let your actions be influenced by your fears.

In any language it is a struggle to make a sentence say exactly what you mean.

The moment of truth, the sudden emergence of a new insight, is an act of intuition.