Émilie du Châtelet

Who Proved It Goes as the Square · Physicist & Mathematician · 1706–1749

The marquise who argued that the force of a moving body varies as the square of its speed — the quantity now called kinetic energy — and whose French translation of Newton's Principia is still the standard one.

Who was Du Châtelet?

Émilie du Châtelet was born in Paris in 1706 to a father unusual enough to have his daughter taught Latin, mathematics and metaphysics. Barred as a woman from the Academy of Sciences and from the cafés where mathematicians argued — she is said to have dressed as a man to get into one — she built her scientific life at the château of Cirey, where Voltaire lived under her protection for fifteen years and where she assembled a library of some twenty thousand volumes. In 1738 she and Voltaire entered the Academy's prize essay competition on the nature of fire, secretly and separately; neither won, but hers was published, and it proposed that different colours of light carry different heating power. Her most consequential work was in the vis viva controversy, the long argument over what quantity measures the force of a moving body. The Newtonians said mass multiplied by velocity; du Châtelet, following Leibniz and marshalling Willem 's Gravesande's experiments — brass balls dropped into soft clay, sinking to a depth that went as the SQUARE of the speed — argued that the conserved quantity varies as v². She was right, and the quantity is now called kinetic energy. Her last work, a French translation of the Principia with an extensive commentary, was completed while she was pregnant at forty-two and published after her death in childbirth. It remains the standard French edition.

Major achievements

• Argued and evidenced that the force of a moving body varies as the square of its speed
• Translated Newton's Principia into French with a commentary — still the standard edition
• Published a prize essay on the nature of fire, proposing that colours differ in heating power
• Wrote Institutions de Physique, synthesising Newtonian and Leibnizian physics
• Established one of the foremost private scientific households in Europe at Cirey

Life in brief

• 1706 — Born in Paris: Taught Latin, mathematics and metaphysics as a girl.
• 1733 — Meets Voltaire: The partnership that will define Cirey begins.
• 1737 — The essay on fire: Entered for the Academy prize, secretly and separately from Voltaire.
• 1740 — Institutions de Physique: Newtonian and Leibnizian physics brought together.
• 1741 — The vis viva dispute: Argues in print that the conserved quantity goes as v².
• 1749 — The Principia finished: Completed while pregnant at forty-two.
• 1749 — Dies at Lunéville: Days after giving birth; the translation is published posthumously.

Explore the life of Du Châtelet — five chapters

1. A Father Who Had Her Taught — Latin, mathematics and metaphysics, for a girl
2. Cirey — Twenty thousand books, and a laboratory in a country house
3. Vis Viva — Brass balls dropped into clay, and the square of the speed
4. Translating Newton — Not a translation — a commentary that argues
5. A Mere Appendage — What was remembered, and what was not

Read the five-chapter life of Émilie du Châtelet →

Where Du Châtelet appears in your course

Émilie du Châtelet has a genuine claim on 1 lesson of the Pearson Edexcel International GCSE science course built into Incandio:

• Gravitational Potential and Kinetic Energy — Physics: The ½mv² on this page is the settlement of an argument she was central to. Through the 1730s and 1740s physicists disputed what quantity measures the force of a moving body: the Newtonians said mass times velocity, and du Châtelet, following Leibniz, argued for a quantity going as v². She marshalled 's Gravesande's experiments — brass balls dropped into soft clay, sinking to a depth that went as the square of the speed rather than in proportion to it — and argued the case in print against the leading French physicists. She was right, and the quantity is kinetic energy.

Begin

• Start a conversation with Du Châtelet — a dramatised, historically grounded AI portrayal
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• Explore the life of Du Châtelet — five chapters
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