1 article for "Clairaut, Alexis Claude"

**Clairaut, Alexis Claude**[Astro*Index]

(1713-1765) French mathematician. Born and died at Paris.

Tutored by his father, he studied the Calculus at 10, wrote mathematical papers at 13, and published a book on mathematics at 18. He was a member of the expedition of Maupertuis to Lapland to measure the curvature of the Earth. In 1743, he published a book dealing with the shape of a rotating body, acting under the combined effects of gravitational and centrifugal forces. He demonstrated how the shape of the Earth could be calculated by measuring the force of gravity at various points by means of the timing of the swings of a pendulum. He made many contributions to the lunar theory, and computed the gravitational effects on the Earth of Venus and the Moon. Using the observations of Lacaille, he obtained reasonable values for the masses of these two bodies. With the assistance of Lalande, he determined the perturbing effect of Jupiter and Saturn on the orbit of Halley's comet, predicting that it would be late in its return, not reaching perihelion until 1759 APR 13 (which was within a month of the actual time). The comet was sighted on 1758 DEC 25.

See also:

♦ Halley, Edmund ♦ LaCaille, Nicholas Louis de ♦ Lalande, Joseph Jerome Le Francois de

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