Man has an intense desire for assured knowledge.

It is impossible to get out of a problem by using the same kind of thinking that it took to get into it.

[Kepler] had to realize clearly that logical-mathematical theoretizing, no matter how lucid, could not guarantee truth by itself; that the most beautiful logical theory means nothing in natural science without comparison with the exactest experience. Without this philosophic attitude, his work would not have been possible.

Our defense is not in our armaments, nor in science, nor in going underground. Our defense is in law and order.

The scientist finds his reward in what Henri Poincare calls the joy of comprehension, and not in the possibility of application to which any discovery may lead.

At present every coachman and every waiter argues about whether or not the relativity theory is correct.

E=mc2. Energy equals mass times the speed of light squared