Alexis Clairaut: A forgotten light of mathematics | Tangente

The prerevolutionary 18^th century, whose emblematic figures included Voltaire and Rousseau, was marked by a great thirst for new ideas and knowledge. Through his various studies, particularly of the three-body problem, Alexis Clairaut did more than anyone to advance the central scientific debate of the Enlightenment—a debate that may seem unremarkable today, but was extraordinarily difficult and delicate: the validity of the law of universal gravitation proposed a few years earlier by Isaac Newton (1643–1727).

Alexis Clairaut (1713–1765).

Clairaut was also remarkable for having begun his career at a very young age, having "absorbed geometry with his mother's milk," as one of his biographers, Abbé Charles Bossut (1730–1814), put it. The son of a mathematics teacher, he presented his first paper to the Académie des sciences at the age of twelve years and eleven months, before becoming a member at eighteen! His candidacy was bolstered by the publication of his first book, Recherches sur les courbes à double courbure (Paris, 1731), a substantial treatise on so-called skew curves, which cannot be drawn in a plane.

The Clairaut family -------------------

Alexis Clairaut's father, Jean-Baptiste Clairaut (?–1767), taught mathematics at one of the most prestigious institutions of the time, the Académie Dugard, founded by the king to educate the nobility. He was also one of the founders of the Société des arts, an association established to promote technology, and a member of the Berlin Academy of Sciences, which received several papers he had written. He also invented a multipurpose mathematical instrument, a "planchette," whose description was published by the Paris Académie des sciences.

Besides Alexis, another of his sons presented a mathematical paper to the Académie des sciences while still a child. Sadly, the boy now known only as "the younger Clairaut" died of smallpox at a very early age. Clairaut's father had the further sorrow of outliving his entire family, though it had numbered twenty-one children. Father and son also endured the pain of losing their wife and mother, Catherine Petit (?–1759), during what should have been a very joyful period: between the completion of the calculations predicting the date of the comet's return and its actual reappearance.