Frenchmathematician and physicist. In 1736 he took part in an expedition to Lapland to measure the length of a degree of latitude; the result proved that the Earth is an oblate spheroid. The next year he provided a rigorous theoretical explanation for the aberration of starlight, which J. Bradley had been unable to do. He used his own solution of the three-body problem to derive an accurate prediction for the date of perihelion passage of Halley's Comet on its return in 1758/9.
Subjects: Astronomy and Astrophysics.