t was 1733 when the poet and philosopher Voltaire met Emilie du Châtelet, a beguiling—and married—aristocrat who would one day popularize Newton’s arcane ideas and pave the way for Einstein’s theories. In an era when women were rarely permitted any serious schooling, this twenty-seven-year-old’s nimble conversation and unusual brilliance led Voltaire, then in his late thirties, to wonder, “Why did you only reach me so late?” They fell immediately and passionately in love.