When asked what he meant by a miracle: Oh, anything with a probability of less than 20%.

The fundamental point in fabricating a chain reacting machine is of course to see to it that each fission produces a certain number of neutrons and some of these neutrons will again produce fission.

Ignorance is never better than knowledge

The fact that no limits exist to the destructiveness of this weapon [the 'Super', i.e. the hydrogen bomb] makes its very existence and the knowledge of its construction a danger to humanity as a whole. It is necessarily an evil thing considered in any light. For these reasons, we believe it important for the President of the United States to tell the American public and the world what we think is wrong on fundamental ethical principles to initiate the development of such a weapon.

Where is everybody? Humans could theoretically colonize the galaxy in a million years or so, and if they could, astronauts from older civilizations could do the same. So why haven't they come to Earth?

Experimental confirmation of a prediction is merely a measurement. An experiment disproving a prediction is a discovery.

I remember my friend Johnny von Neumann used to say, 'with four parameters I can fit an elephant and with five I can make him wiggle his trunk.'