Wootton also insists, against the grain of contemporary academia, that single observed facts, what he calls “killer facts,” really did polish off antique authorities. Facts are not themselves obvious: the fact of the fact had to be invented, litigated, and re-litigated. But, once we agree that the facts are facts, they can do amazing work. Traditional Ptolemaic astronomy, in place for more than a millennium, was destroyed by what Galileo discovered about the phases of Venus. That killer fact “serves as a single, solid, and strong argument to establish its revolution around the Sun, such that no room whatsoever remains for doubt,” Galileo wrote, and Wootton adds, “No one was so foolish as to dispute these claims.” Observation was theory-soaked—Wootton shows a delightful drawing of a crater on the moon that does not actually exist, drawn by a dutiful English astronomer who had just been reading Galileo—and facts were, as always, tempered by our desires. But there they were, all the same, smiling fiendishly, like cartoon barracudas, as they ate up old orbits.