Shape of the Earth

The study of the Earth is called geodesy. In the past, geodesy depended on ground - based surveys. Today, satellites play a major role.

The Earth is not a perfect sphere. It is a unique shape called a geoid, which means "Earth shaped" . The Earth spins faster at the Equator than at the Poles, because the Equator is farther from the Earth's spinning axis. The extra speed of the Earth at the Equator flings it out in a bulge, while it is flattened at the Poles.

Equatorial bulge was predicted in 1687 by Isaac Newton. The equatorial bulge was confirmed 70 years after Newton by French surveys in Peru by Charles de La Condamine, and in Lapland by Pierre de Maupertuis.

The Earth diameter at the Equator is 12,758 km. This is larger, by 43 km , than the vertical diameter from North Pole to South Pole. The official measurement of the Earth's radius at the Equator is 6,376,136 m ± 1m.