It might seem as though there is no subject they haven't mastered, no piece of trivia that they haven't memorized. But it's a wide world, with a long history. Find the book that's stuffed with hilarious facts they've never learned, teach them about historical events that they've never even heard of, give them DVDs that are packed with information. It might once have been hard to buy presents for this know it all, but these gift ideas will make it easy.