- Have been brooding a lot lately on what I have come to think of as the Two-Cafe Problem. The form is borrowed from the old Three-Body Problem, which perplexed mathematicians late into the nineteenth century, and which, as I vaguely understand it, involved calculating the weird swerves and dodges that three planets worked on each other when the force of gravity was working on them all. My problem ...www.randomhouse.com/boldtype/1200/gopnik/excerpt.html