"... the great tragedy of Science - the slaying of a beautiful hypothesis by an ugly fact"

~T.H. Huxley

The most exciting phrase to hear in science, the one that heralds the most discoveries, is not "Eureka!" (I found it!) but "That's funny..." 

~Isaac Asimov

The capacity to blunder slightly is the real marvel of DNA.  Without this special attribute, we would still be anaerobic bacteria and there would be no music. 

~Lewis Thomas

Observations always involve theory.

~Edwin Hubble

The scientist is not a person who gives the right answers, he's one who asks the right questions.

~Claude Lévi-Strauss

That theory is worthless.  It isn't even wrong!

~Wolfgang Pauli