Clairaut, Alexis-Claude

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Clairaut, Alexis-Claude (1713-1765): French Mathematician.

Clairaut was a child prodigy in mathematics and would soon become a celebrated member of the Académie Royale des Sciences. After submitting his mémoire on mathematical curves, Recherches sur les courbes à double courbure (1731), he gained entrance to the Academy under exceptional circumstances at the age of eighteen, thus making him the youngest person ever to be elected. Clairaut was a key figure in the attempt to determine the shape of the Earth, one of the most intense debates of his time, and was also on the front lines of a “civil war” in the French Academy over the validity of Isaac Newton’s theory of attraction.

Schooled by his father, Jean-Baptiste Clairaut – himself a skilled mathematician and Professor who was elected to the Berlin Academy – Clairaut first read a paper on differential calculus, Quatre problèmes sur de nouvelles courbes, before the Academy in 1726, just before his thirteenth birthday. His promotion within the Academy was appropriately meteoric: from adjoint mécanicien on July 1, 1731, Clairaut rose to associé on March 30, 1733, and finally to pensionnaire on May 12, 1738. The astonishing arc of Clairaut’s rise in the Academy is due both to his unparalleled genius as well as to his powerful and timely connections within the Academy.

Another renowned young member of the Academy, Maupertuis, Pierre-Louis Moreau de took the younger Clairaut under his wing, and together the two championed the Newtonian worldview. In 1687 Newton published the first edition of the Principia, in which he took up the problem of the shape of the Earth and argued that it was not a perfect sphere. By the time of the third edition (1726) Newton continued to argue that the Earth was an ellipsoid flattened at the poles. His theory of effective gravity at the points of the earth’s surface called into question the terrestrial observations of certain older members of the French Academy, notably Jean-Jacques Dortous de Mairan and Jacques Cassini. Cassini, in particular, argued that the earth was slightly elongated at the poles. Descartes’s theories of motion of bodies in space also held sway at the French Academy. Newton’s theories were met with great resistance in France, and the Cartesian world, along with the reputations of Cassini and Fontenelle, Bernard le Bovier de at the Academy were now under attack in a veritable querelle between the Moderns and the Ancients.

Scientific and literary quarrels were a main event of eighteenth century intellectual and social life in France. The drama at the French Academy was underscored by the extraordinary attention (and the royal stamp of approval) given to two geodesic expeditions, one to Peru in 1735 and a second to Lapland, undertaken by Maupertuis and Clairaut in 1736. Both teams planned to take measurements of the length of a degree of latitude in the hopes of resolving the dispute over the shape of the Earth at the pole and the equator. The publicity that Maupertuis and Clairaut orchestrated for the Lapland expedition was remarkable for its time, as were the dramatic pronouncements that Clairaut delivered through a series of mémoires before the Academy.

While the Lapland expedition did not clearly prove Newton’s theories, it did establish that personality and ambition were essential to the craft of the Academy scientist. Hailed in the press as the next Pascal and as the French Newton, Clairaut was a prolific and indefatigable scientist who followed his Théorie de la figure de la Terre (1743) with the Théorie de la lune (1752), a work that earned him the prize of the St. Petersburg Academy, as well as a rivalry with yet another well known Academy member and encyclopédiste, Jean Le Rond d’Alembert. After the expedition to the pole, the next big project would be the attempt to predict the return of Halley’s comet. For Clairaut, it was an opportunity to develop a computational method to extend Newton’s calculus of the motion of three or more bodies in space. Several critics, notably Alembert, Jean Le Rond d’ attacked the credibility of the comet calculations. Yet Clairaut assembled a team of assistants to divide the labor of scientific computation and eventually came within one month of predicting the perihelion of the comet in 1758.

Clairaut made a reputation of being a forward-thinking, ambitious scientist who was also somewhat of a bon vivant. In a society where the borders of the Academy and the aristocratic salon were largely open, Clairaut served as tutor to Du Châtelet, Gabrielle Emilie le Tonnelier de Breteuil, Marquise. Although some historians have assumed a “dangerous liaison” in this tutor/pupil relationship, most believe that Clairaut focused on helping the Marquise produce her outstanding translation and commentary of Newton’s Principia (1756). In his Eloge de Clairaut before the Academy, Jean-Paul Fouchy offered a charitable portrait: “un maintien agréable, sa douceur et sa modestie étaient peintes sur son visage.” In Clairaut’s obituary, we read “Ce grand Géomètre était un fort honnête homme, mais il aimait les femmes et avait toujours eu des maîtresses entretenues; en un mot c’était un célibataire libertin.”

Clairaut may have been a modest bachelor, we cannot know with any certainty, save for a glimpse in the archives. Yet we do know that Clairaut was passionate about geometry and bodies in motion, or the mathematics of Newton that defined the earthly ambitions of the age.

Further Reading:

Elisabeth Badinter, Les Passions Intellectuelles, 1999.

David Alan Grier, When Computers Were Human, 2005.

Michael Rand Hoare, The Quest For The True Figure Of The Earth: Ideas And Expeditions In Four, 2005.

Mary Terrall, The Man Who Flattened the Earth: Maupertuis and the Sciences in the Enlightenment, 2002.

John Patrick Walsh

College of Charleston