From Plane to Spheroid: Determining the Figure of the Earth from 3000 Bc to the 18th Century Lapland and Peruvian Survey Expeditions
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 On: 2006-07-29
The French Academy of Sciences sent out survey expeditions to Peru and Lapland in 1735/36 to determine the shape of the earth. This book conveys some of the charm of this amusing and interesting episode in the history of science. Now, to determine the shape of the earth by measurements one would of course have to measure the north-south distance between two latitudes. Straightforward measurement is not feasible. One instead triangulates a large area, measures all the angles, and measures one side. This one length then propagates through the grid by elementary trigonometry. Smith focuses the entire book on this perspective, describing the history of trigonometry and measuring instruments and so on. More theoretical treatments of the shape of the earth are treated poorly, if at all. For instance, Newtons important determination of the shape of the earth in the Principia is too hastily summarised, claiming for example that Newton "was able to demonstrate" that the earth must be spheroidal (p. 79), even though there is no such proof in the Principia or elsewhere (cf. prop. XIX-XX, book III, of the Principia).
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