Pierre Louis Moreau de Maupertuis

Maupertuis was a French mathematician, astronomer, and natural philosopher whose life straddled two scientific revolutions. Born in Saint-Malo in 1698 to a wealthy privateer's family, he was tutored at home before heading to Paris to study mathematics. Elected to the Académie des Sciences at twenty-five, he became an early and vocal champion of Newtonian physics in a France still wedded to Descartes — a position that put him in frequent correspondence with Voltaire and Émilie du Châtelet.

His most public triumph came in 1736, when he led a Royal Academy expedition to Lapland to measure a degree of the meridian near the Arctic Circle. A parallel expedition went to Peru. The question was whether the Earth bulged at the equator (as Newton had predicted) or at the poles (as the Cassini family insisted). Maupertuis, working through a winter of frostbite and reindeer sledges, returned with measurements that confirmed Newton. Voltaire nicknamed him 'the Great Flattener' and never stopped teasing him about it.

In 1744 Maupertuis presented to the Berlin Academy — where Frederick the Great had lured him as president — a memoir stating what is now called the principle of least action. He claimed that nature, in any process, minimises a quantity he called action — defined roughly as mass times velocity times distance integrated along a path — and he interpreted the principle theologically: God, acting economically, would design the world so that the simplest possible rule governed every motion. Euler, working at Berlin alongside him, produced the rigorous mathematical version the same year.