Clairaut, Euler and the Figure of the Earth

• Published in: Gaṇita bhāratī Vol. 42; no. 1-2; pp. 87 - 127
• Main Author: Papadopoulos, Athanase
• Format: Journal Article
• Language: English
• Published: New Delhi Prints Publications Pvt. Ltd 06.08.2022
• Subjects: 18th century; Astronomers; Astronomy; Autobiographies; Earth; Elongation; Equatorial regions; Fluid dynamics; Geography; Hydrostatics; Mathematicians; Mathematics; Philosophers; Poles; Questions; Scientists; France
• ISSN: 0970-0307
• DOI: 10.32381/GB.2020.42.1-2.4

The sphericity of the form of the Earth was questioned around the year 1687, primarily, by Isaac Newton who deduced from his theory of universal gravitation that the Earth has the form of a spheroid flattened at the poles and elongated at the equator. In France, some preeminent geographers were not convinced by Newton's arguments, and about the same period, based on empirical measurements, they emitted another theory, claiming that on the contrary, the Earth has the form of a spheroid flattened at the equator and elongated at the poles. To find the real figure of the Earth became one of the major questions that were investigated by geographers, astronomers, mathematicians and other scientists in the 18th century, and the work done around this question had an impact on the development of all these fields. In this paper, we review the work of the 18th-century French mathematician, astronomer and geographer Alexis-Claude Clairaut related to the question of the figure of the Earth. We report on the relation between this work and that of Leonhard Euler. At the same time, we comment on the impact of the question of the figure of the Earth on mathematics, astronomy and hydrostatics. Finally, we review some later mathematical developments that are due to various authors that were motivated by this question. It is interesting to see how a question on geography had such an impact on the theoretical sciences.