France remembered her as Voltaire's mistress. France still reads Newton in her words.
In the summer of 1749 a forty-two-year-old marquise sat at a desk in Lunéville, heavily pregnant and convinced she would not survive the birth, racing to finish a book. The book was Isaac Newton's Principia — the hardest text in Europe — and she was not merely translating it. She was rebuilding its geometry in the new language of calculus so that Frenchmen who could not read Latin, or Newton, could finally follow the argument. She finished the manuscript in September. She died on the tenth, six days after her daughter was born.
Émilie du Châtelet had spent her life doing physics in a country whose Academy of Sciences would not admit her, and history repaid her by filing her under Voltaire. Yet she wrote the physics textbook that carried Leibniz's ideas into France, argued the continent into accepting that the energy of a moving body goes as mv² and not mv, and left behind a translation so good that it is still, two and a half centuries later, the Newton that France reads.
A life by candlelight
The lifeline
1706
Born in Paris to a court official who, unusually, had her taught Latin, mathematics and four languages
1725
Married at eighteen to the Marquis du Chastellet, a soldier mostly away at war
1733
Meets Voltaire; takes lessons from Maupertuis and Clairaut, two of France's finest mathematicians
1737
Enters the Academy's prize essay contest in secret — against Voltaire, who does not know
1740
Publishes Institutions de physique, then takes on the Academy's secretary over mv² — and wins the argument
1749
Dies at Lunéville on 10 September, days after childbirth, the Principia manuscript finished
By the numbers
The measure of her
42
Years she lived — she completed the Principia translation in her last weeks
mv2
The quantity she defended against Newtonian France — the ancestor of kinetic energy
1759
Her Newton appeared complete, ten years after her death. It is still France's standard translation
230
Years between her death and the Académie des sciences electing its first woman member, in 1979
What she wrote
The work
1737
Dissertation sur la nature et la propagation du feu. Written in secret at night while Voltaire prepared his own entry for the same Academy prize. Neither won — Euler did — but the Academy printed hers in 1739, a rare honour for a woman's work. In it she weighed heated metals to argue that fire has no mass, and proposed that different colours of light carry different heating powers.
1738
Éléments de la philosophie de Newton. Published under Voltaire's name, with her at work throughout — and its frontispiece says so: Newton in the heavens, du Châtelet holding a mirror that reflects his light down onto Voltaire's writing desk.
1740
Institutions de physique. A physics textbook begun for her thirteen-year-old son, which became the book that introduced Leibniz's metaphysics and mechanics to French readers.
1741
The vis viva quarrel. When Dortous de Mairan, permanent secretary of the Academy, published a rebuke, she answered it in print — defending mv² as the true measure of a moving body's force. Contemporaries judged her the winner.
1746
Elected to the Academy of Sciences of the Institute of Bologna — the membership Paris would never offer her.
1749–59
Principes mathématiques de la philosophie naturelle. Newton's Principia in French, with an algebraic commentary of her own drawing on Clairaut. Finished weeks before she died; published complete in 1759 with a preface by Voltaire. No one has replaced it since.
Shut out, then indispensable
Recognition
In her lifetime
Ineligible for the Académie royale des sciences — it took no women
Entered its prize contest anonymously; her essay was printed but could win nothing
By long tradition, turned away from the Café Gradot, where the mathematicians met, and returned dressed as a man
Read across Europe as Voltaire's companion first and a physicist second
Bologna made her a member in 1746; Paris never did
Today
Her Principia remains the only complete French translation — the one still cited and reprinted
Historians credit her Institutions with carrying vis viva into France, on the road to kinetic energy
Her Discours sur le bonheur is read as a small classic of Enlightenment philosophy
The Institut Émilie du Châtelet was founded in Paris in 2006, three centuries after her birth
Voltaire's own verdict, in grief: "a great man whose only fault was being a woman"
The place that made her
Cirey-sur-Blaise
Her husband's crumbling château in Champagne, which she and Voltaire rebuilt from 1734 into something Europe had not quite seen: a country house run as a laboratory. Instruments were ordered from Paris and London, experiments on fire and light were staged in its rooms, and visitors reported a library on a scale no private house had any business owning. She kept a punishing schedule there — coffee, mathematics, and work far into the night.
21,000
Volumes in the Cirey library, by contemporary count — more than most universities held
1734
The year the château became her refuge, her laboratory and her workshop
~200 km
East of Paris — and of the Academy that would not have her
"The love of study is, of all the passions, the one that contributes most to our happiness."
— Émilie du Châtelet, Discours sur le bonheur, c. 1747
