Who was Émilie du Châtelet?
A French natural philosopher and mathematician of the early eighteenth century whose translation and commentary on Newton's Principia remains the standard French edition — and whose own work on energy anticipated a concept physics would not settle for another century.
Her situation. Born in 1706 into the French aristocracy, she was unusually well educated for a woman of her time, being taught languages and mathematics, and later studied under Maupertuis and Clairaut. Academies were closed to women; she was famously refused entry to a café where scientists met and reportedly returned in men's clothing.
Her substantive contributions:
The Principia translation. She rendered Newton's Latin into French and — more importantly — added an extensive commentary recasting his geometric arguments in the calculus notation then developing on the continent, making the work genuinely usable by French mathematicians. Published after her death, it is still the standard French text.
The Institutions de Physique (1740), an ambitious textbook attempting to reconcile Newtonian physics with Leibnizian metaphysics — an intellectual synthesis rather than a summary.
Kinetic energy. This is her sharpest technical contribution. The prevailing Newtonian view held that a moving body's "force" was proportional to its velocity. Drawing on Leibniz and on Willem 's Gravesande's experiments dropping balls into clay, she argued it was proportional to the square of velocity — the relationship underlying kinetic energy and the conservation of energy. She was substantially right, at a time when the question was genuinely contested.
Work on fire, submitted anonymously to an Academy competition, which proposed that heat and light are related and speculated about what would later be understood as infrared radiation.
Her partnership with Voltaire — intellectual as much as romantic — is how most people encounter her, and it consistently overshadows the fact that she was the better mathematician of the two.
She died in 1749, days after childbirth, at 42, having pressed to finish the Newton commentary first.