'And Flamsteed says that they do,' Isaac said, yanking the sheaf of notes out of Daniel's hip pocket. Ignoring the cover letter, he tore the ribbon from the bundle and began to scan the pages. 'Therefore gravity does indeed follow an inverse square law. But we may only say so because it is consistent with Flamsteed's observations. If tonight Flamsteed notices a comet moving in a spiral, it shows that all my work is wrong.'