On closing the book and thinking................

Dear Mr. Lewis:
     Thank you for your nice letter.  It makes me feel good to hear that you liked my colloquium so much.  Don't despair of standard dull textbooks.  Just close the book once in a while and think what they just said in your own terms as a revelation of the spirit and wonder of nature.  The books give you facts but your imagination can supply life.
     My father taught me to do that when I was a little boy on his knee and he read the Encyclopedia Britannica to me!  He would stop every once in a while and say - now what does that really mean.  For example, "the head of tyrannosaurus rex was four feet wide, etc." - it means if he stood on the lawn outside, his head would look in at your bedroom the second floor, and if he poked it in the window it would break the casement on both sides.  Then when I was a little older when we would read that again he would remind me of how strong the neck muscles had to be - of rations of weight and muscle area - and why land animals can't become the size of whales - and why grasshoppers can jump just about as high as a horse can jump.  All this, by thinking about the size of a dinosaur's head!
      Yours, Sincerely,
      Richard P. Feynman

-from a letter dated 8/10/81 from Perfectly Reasonable Deviations From The Beaten Track:  The Letters of Richard P. Feynman