When scientists do not know the answer to something, they do two things: admit "I don't know" and say "let's find out". This is the basis of "being scientific"; this is what teachers should also be doing in order to develop scientific literacy in their pupils. The heart of scientific enquiry is this two-part "I don't know, let's find out" attitude to ignorance. The fact that a teacher does not understand something can be turned into a wonderful opportunity to explore and to experience directly how real science works. Remember, one is being scientific when one says "I don't know"--as long as one follows it up with "let's find out." (Contains 4 figures and 2 online resources.)