Just when you think you've perceived a subject clearly - just when the glass, or the light, or the peephole that has allowed you to observe it with certitude - nature fools you. Blame it on perspective, on distortions in the medium, on the demons of simulacra: You can't always believe what you see. In optics it's called an aberration - when light is imperfect, when rays fail to converge to a sharply defined focus. It can be due to a flaw, to the distance, or perhaps even to a failure in the optic nerve. Astronomers know this as the aberration of heavenly bodies: You think you see a star to the left, but in fact it is to the right, because, though every hair on your head is in place, you are reeling through the universe at considerable velocity. This is very like the moment when you gaze out the window of a moving car and the rain looks as if it is falling sideways. It is now. Its trajectory is a plumb line toward the center of the earth, following the brute pull of gravity. But if you are planted serenely in your seat, it is hard to factor that you are rushing along the earth's surface, and so what you think you see happening isn't happening at all.
Cellophane, Marie Arana, p. 255.