|Émilie du Châtelet|
Portrait by Maurice Quentin de La Tour.
|Born||December 17, 1706
|Died||September 10, 1749
Gabrielle Émilie Le Tonnelier de Breteuil, marquise du Châtelet (December 17, 1706, Paris – September 10, 1749) was a French mathematician, physicist, and author during the Age of Enlightenment. Her crowning achievement is considered to be her translation of Isaac Newton's monumental work Principia Mathematica, published after her death with an "algebraical commentary"; it is still considered the standard translation in French. Voltaire, one of her lovers, declared in a letter to his friend King Frederick II of Prussia that du Châtelet was "a great man whose only fault was being a woman".
Her father was Louis Nicolas le Tonnelier de Breteuil, the Principal Secretary and Introducer of Ambassadors to King Louis XIV, whose position placed him at the center of social activity in the court, and thus gave the family great status. Among their acquaintances was Fontenelle, the perpetual secretary of the French Académie des Sciences. Émilie's father Louis-Nicolas, recognizing her early brilliance, arranged for Fontenelle to visit and talk about astronomy with her when she was 10 years old. Émilie's mother, Gabrielle-Anne de Froulay, was brought up in a convent, at the time the predominant educational institution available to French girls and women. While some sources believe her mother did not approve of her intelligent daughter, or of her husband's encouragement of Émilie's intellectual curiosity, there are also other indications that her mother not only approved of du Chatelet's early education, but actually encouraged her to vigorously question stated fact.
In either case, such encouragement would have been seen as unusual for parents of their time and status. When she was small, her father arranged training for her in physical activities such as fencing and riding, and as she grew older, he brought tutors to the house for her. As a result, by the age of twelve she was fluent in Latin, Italian, Greek and German; she was later to publish translations into French of Greek and Latin plays and philosophy. She received education in mathematics, literature, and science. Her mother Gabrielle-Anne was horrified at her progress and fought Louis-Nicolas at every step, once attempting to have Émilie sent to a convent.
Émilie also liked to dance, was a passable performer on the harpsichord, sang opera, and was an amateur actress. As a teenager, short of money for books, she used her mathematical skills to devise highly successful strategies for gambling.
Much later in life, she once lost 84,000 francs (the equivalent of over US$1,000,000 in 2009)—some of it borrowed—in one evening at the table at the court of Fontainebleau, to card cheats. To quickly raise the money to pay back her huge debts, she devised an ingenious financing arrangement similar to modern derivatives, whereby she paid tax collectors a fairly low sum for the right to their future earnings (they were allowed to keep a portion of the taxes they collected for the King), and promised to pay the court gamblers part of these future earnings.
On 12 June 1725, she married the Marquis Florent-Claude du Chastellet-Lomont, and thus became Marquise du Chastellet (the spelling Châtelet was introduced by Voltaire, and has now become standard). Like many marriages among the nobility, theirs was arranged. The couple had little in common, but the proprieties were observed in accordance with contemporary mores.
After bearing three children, Émilie, considering her marital responsibilities fulfilled, made an agreement with her husband to live separate lives while still maintaining one household. The Marquis was a military man and governor of Semur-en-Auxois in Burgundy. In the upper classes of France at the time, it was acceptable for both the husband and wife to have a lover.
At the age of twenty-four, Émilie du Châtelet had an affair with the Duc de Richelieu that lasted for a year and a half. The Duc was interested in literature and philosophy, and Châtelet was one of the few women who could converse with him on his own level. She read every book of consequence, attended the theater regularly, and enjoyed intellectual debate. Châtelet expressed an interest in the works of Isaac Newton, and Richelieu encouraged her to take lessons in higher mathematics to better understand his theories. Moreau de Maupertuis, a member of the Academy of Sciences, became Châtelet's tutor in geometry. He was a mathematician, astronomer and physicist, and supported Newton's theories, which were a topic of hot debate at the Academy.
Émilie and Voltaire, the fourth of her lovers after her marriage, met after he returned from his exile in London. Châtelet invited him to live in her country house at Cirey-sur-Blaise in Haute-Marne, north-eastern France, and he became her long-time companion (under the eyes of her tolerant husband). There she studied physics and mathematics and published scientific articles and translations. To judge from Voltaire's letters to friends and their commentaries on each other's work, they lived together with great mutual liking and respect.
Châtelet's last affair proved to be fatal. In her early 40s, she had an affair with the poet Jean François de Saint-Lambert and became pregnant. In a letter to a friend she confided her fears that, because of her age, she would not survive her pregnancy. She bore the child, but died six days later from an embolism at the age of 42.
In 1737, Châtelet 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 book Institutions de Physique (“Lessons in Physics”) appeared in 1740; it was presented as a review of new ideas in science and philosophy to be studied by her thirteen-year-old son, but it incorporated and sought to reconcile complex ideas from the leading thinkers of the time. In it, she combined the theories of Gottfried Leibniz and the practical observations of Willem 's Gravesande to show that the energy of a moving object is proportional not to its velocity, as had previously been believed by Newton, Voltaire and others, but to the square of its velocity. (In classical physics, the correct formula is Ek = 1⁄2mv², where Ek is the kinetic energy of an object, m its mass and v its velocity.)
In the year of her death, she completed the work regarded as her outstanding achievement: her translation into French, with her commentary, of Newton’s Principia Mathematica, including her derivation from its principles of mechanics the notion of conservation of energy. Today du Châtelet's translation of Principia Mathematica is still the standard translation of the work into French.
Although the classical mechanics of du Châtelet are not approached with the same methodology as Einstein's concept of mass and velocity, in his famous equation for the energy equivalent of matter E = mc² (where c represents the velocity of light), modern biographers and historians persist in seeing a neat accord with the principle E ∝ mv² first recognised by du Châtelet from over 150 years before. It should be emphasized, however, that from a physical point of view, du Châtelet's principle is a correct assessment of the kinetic energy in classical mechanics, and is the first term in an expansion of Einstein's Mass–energy equivalence.