Gabrielle-Emilie Le Tonnelier de Breteuil, the daughter of the French court’s chief of protocol, married the marquis du Chatelet in 1725. She lived the life of a courtier and bore three children. But at age 27, she began studying mathematics seriously and then branched into physics. This interest intensified as she began an affair with the philosopher Voltaire, who also had a love of science. Their scientific collaborations—they outfitted a laboratory at du Chatelet’s home, Chateau de Cirey, and, in a bit of a competition, each entered an essay into a contest on the nature of fire (neither won)—outlasted their romance. Du Chatelet’s most lasting contribution to science was her French translation of Isaac Newton’s Principia, which is still in use today. At age 43, she fell in love with a young military officer and became pregnant; she died following complications during the birth of their child.