Solar eclipses were interpreted throughout much of history as bad news for the sovereign — an ominous sign for their personal health or that of the realm. But those fears helped fuel thousands of years of scholarship. This progress began in Mesopotamia with a hunt for periodic patterns in historical data. It has culminated in an era in which we know the interdependent future motions of solar system bodies centuries in advance, transforming what was once a cause for cosmic-scale angst into a matter of cold clockwork.