The best weapon of a dictatorship is secrecy; the best weapon of a democracy is openness.

I am guilty of the great crime of optimism.

Really exotic methods of propulsion . . . will have to be devised to get there. How it will be done, I do not know. Whether it will be done, I am not quite certain. But I would bet it can be done.

Secrecy, once accepted, becomes an addiction.

The best weapon of a dictatorship is secrecy; the best weapon of a democracy is openness.

Physics is, hopefully, simple. Physicists are not.

If not for me, the H-bomb would have been developed in Russia first. In the U.S., we'd now be speaking Russian.