Chad Orzel's clever analysis of the children's book Goodnight Moon:

The attentive toddler will find a lot to look at in the pictures-- there's a mouse in every one that SteelyKid delights in pointing out-- but an inquiring adult might well ask "Just how long does it take this bunny to say goodnight to all this stuff, anyway?"

Well, we can answer this question with SCIENCE! You see, there are six pictures in the book showing the moon through one of the room's windows, and as the book goes along, the moon moves higher in the window. This provides a way to estimate the passage of time in the book.