Book excerpt: The captivating biography of the French aristocrat who balanced the demands of her society with passionate affairs of the heart and a brilliant life of the mind Although today she is best known for her fifteen-year liaison with Voltaire, Gabrielle Emilie le Tonnelier de Breteuil, Marquise Du Châtelet (1706-1749) was more than a great man's mistress. After marrying a marquis at the age of eighteen, she proceeded to fulfill the prescribed-and delightfully frivolous-role of a French noblewoman of her time. But she also challenged it, conducting a highly visible affair with a commoner, writing philosophical works, and translating Newton's Principia while pregnant by a younger lover. With the sweep of Galileo's Daughter, Emilie Du Châtelet captures the charm, glamour, and brilliance of this magnetic woman.