Einstein, my upset stomach hates your theory [of General Relativity]—it almost hates you yourself! How am I to' provide for my students? What am I to…

- Paul Ehrenfest

No two electrons in the same state? That is why atoms are so unnecessarily big, and why metal and stone are so bulky.

- Paul Ehrenfest

Don't be impatient with me. Bear in mind that I hop around among all of you big beasts like a harmless and helpless frog who is afraid of being squas…

- Paul Ehrenfest

You will get your difficulties with the point electron.

- Paul Ehrenfest

Physics is simple, but subtle.

- Paul Ehrenfest

A thesis has to be presentable... but don't attach too much importance to it. If you do succeed in the sciences, you will do later on better things a…

- Paul Ehrenfest