Nicolas Louis de Lacaille - Measuring The Southern Arc of Meridian

Measuring The Southern Arc of Meridian

At the Cape, Abbé de Lacaille wanted to test Newton's theory of gravitation and verify the shape of the earth in the southern hemisphere. He set out a baseline north of Darling. Using triangulation he then measured a 137 km arc of meridian between Cape Town and Aurora. The results suggested the earth was egg-shaped rather than oval. In 1838, Thomas Maclear who was Astronomer Royal at the Cape, repeated the measurements. He found that de Lacaille had failed to take into account the gravitational attraction of the nearby mountains.

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