Pierre Louis Maupertuis

Pierre Louis Maupertuis (1698–1759) was a French mathematician, philosopher, and naturalist who formulated an early principle of least action and led an expedition to measure a meridian in Lapland.

Lapland expedition: A 1736–1737 French scientific expedition to measure a degree of meridian near the Arctic Circle. Maupertuis led this expedition, whose measurements supported Newtonian predictions about Earth’s flattening.
Meridian arc measurement: A geodetic method that estimates Earth’s curvature by measuring a north–south distance and its associated change in latitude. Maupertuis’s team measured a Lapland arc to compare polar curvature with measurements nearer the equator.
Émilie du Châtelet: A French mathematician and natural philosopher known for translating and explaining Newton’s Principia. Her Newtonian scholarship connected the French debate over mechanics to Maupertuis’s advocacy of Newtonian physics.
Académie des Sciences: France’s royal scientific academy, founded in 1666 to support and organize research. Maupertuis entered its mathematical community before becoming a prominent advocate of Newtonian science.
Fermat’s principle: A principle of geometrical optics stating that light follows a path of stationary travel time. Its earlier use of an extremum principle prompted comparisons with Maupertuis’s proposal for mechanics.
Figure of the Earth: The shape and dimensions of Earth, described through measurements of its curvature and gravitational field. The expedition’s measured meridian arc helped settle whether Earth bulged at the equator.
Triangulation: A surveying method that calculates distant positions from measured angles and a known baseline. Triangulation let the expedition extend a small set of ground measurements across a long meridian.
Leonhard Euler: A Swiss mathematician whose work transformed analysis, mechanics, and mathematical notation. Euler developed a more general mathematical treatment of stationary action after Maupertuis’s proposal.
Newtonianism: The body of scientific ideas and methods derived from Isaac Newton’s mechanics and universal gravitation. Maupertuis’s geodesy and mechanics helped introduce Newtonian ideas into French intellectual life.
Hamiltonian mechanics: A formulation of classical mechanics built around generalized coordinates, momenta, and the Hamiltonian function. Its action-based formulation developed a broader mechanics than Maupertuis’s original statement.

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