“This seemed to calm Isaac down, though he did not apologize for having thought the worst about Daniel. He said something along the lines of: “Heavenly radiance fills the aether, its rays parallel and straight and, so long as nothing is there to interrupt them, invisible. The secrets of God’s creation are all told by those rays, but told in a language we do not understand, or even hear—the direction from which they shine, the spectrum of colors concealed within the light, these are all characters in a cryptogram. The gnomon—look at our shadows on the Green! We are the gnomon. We interrupt that light and we are warmed and illuminated by it. By stopping the light, we destroy part of the message without understanding it. We cast a shadow, a hole in the light, a ray of darkness that is shaped like ourselves—some might say that it contains no information save the profile of our own forms—but they are wrong. By recording the stretching and skewing of our shadows, we can attain part of the knowledge hidden in the cryptogram. All we need to make the necessary observations is a fixed regular surface—a plane—against which to cast the shadow. Descartes gave us the plane.”