الأصول الرياضية للفلسفة الطبيعية
In "Philosophiæ Naturalis Principia Mathematica" (1686), Isaac Newton gave a theoretical explanation for the "bulging equator" which also explained the differences found in the lengths of the "second pendulums", theories that were confirmed by the French Geodesic Mission to Peru undertaken by the French Academy of Sciences in 1735.