[Newton wrote to Halley ... that he would not give Hooke any credit] That, alas, is vanity. You find it in so many scientists. You know, it has always hurt me to think that Galileo did not acknowledge the work of Kepler.

Imagination encircles the world.

For every one billion particles of antimatter there were one billion and one particles of matter. And when the mutual annihilation was complete, one billionth remained - and that's our present universe.

It's not that I'm so smart, it's just that I stay with problems longer.

The pioneers of a warless world are the young men (and women) who refuse military service.

I have always eaten animal flesh with a somewhat guilty conscience.

I do not believe that a man should be restrained in his daily actions by being afraid of punishment after death or that he should do things only because in this way he will be rewarded after he dies. This does not make sense. The proper guidance during the life of a man should be the weight that he puts upon ethics and the amount of consideration that he has for others.