The true definition of madness is repeating the same action, over and over, hoping for a different result.

[Max Planck] was one of the finest people I have ever known... but he really didn't understand physics, [because] during the eclipse of 1919 he stayed up all night to see if it would confirm the bending of light by the gravitational field. If he had really understood [general relativity], he would have gone to bed the way I did

Reading, after a certain age, diverts the mind too much from its creative pursuits. Any man who reads too much and uses his own brain too little falls into lazy habits of thinking.

You teach me baseball and I'll teach you relativity...No we must not. You will learn about relativity faster than I learn baseball.

... one does people the best service by giving them some elevating work to do and thus indirectly elevating them.

The man who regards his own life and that of his fellow-creatures as meaningless is not merely unfortunate but almost disqualified for life.

I like neither new clothes nor new kinds of food.