An oblate spheroid is a famous shape. It is the shape of the Earth and some other planets. It is like a sphere squashed from the top so the circumference around the poles is less than the circumference around the equator. Shapes of this type are called ellipsoids.
Origin of flattening[change | change source]
In 1687 Isaac Newton published the Principia. He included a proof that a rotating self-gravitating fluid body in equilibrium takes the form of an oblate ellipsoid of revolution (a spheroid). The amount of flattening depends on the density and the balance of gravitational force and centrifugal force.