Gabrielle Émilie Le Tonnelier de Breteuil, marquise du Châtelet (December 17, 1706 - September 10, 1749) was a French mathematician, physicist, and author during the Age of Enlightenment. Her education has been the subject of much speculation, but nothing is known with certainty. In 1737 she published a paper entitled Dissertation sur la nature et la propagation du feu, based upon her research into the science of fire, that predicted what is today known as infrared radiation and the nature of light. Her crowning achievement is her translation and commentary on Isaac Newton's work Principia Mathematica. Louis-Simon Lempereur, circa 1771-72 (cropped and cleaned).