There's no system foolproof enough to defeat a sufficiently great fool.

If there ever was a misnomer, it is "exact science." Science has always been full of mistakes. The present day is no exception. And our mistakes are good mistakes; they require a genius to correct. Of course, we do not see our own mistakes.

No endeavor that is worthwhile is simple in prospect; if it is right, it will be simple in retrospect.

Society's emissions of carbon dioxide may or may not turn out to have something significant to do with global warming-the jury is still out.

My experience has been in a short 77 years that in the end when you fight for a desperate cause and have good reasons to fight, you usually win.

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.

I am guilty of the great crime of optimism.