Quanta Magazine: How the Ancient Art of Eclipse Prediction Became an Exact Science

Decades earlier, Halley, an avid reader of ancient texts, had rediscovered and popularized a helpful celestial cycle for thinking about eclipses and the position of the moon in the sky: 6,585 days, or a little more than 18 years. He called this cycle the “Saros,” which modern historians view as a mistranslation of a Sumerian symbol that originally meant something like “universe” or “big number.”