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How do Newton’s laws explain why Earth is not perfectly spherical?

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A diagram of a cylindrical vessel containing gas, with a movable piston held down by a weight. Countless small dots beneath the piston represent gas particles in rapid, random motion, illustrating Bernoulli's model of gas pressure. — physics As conceived by Daniel Bernoulli in *Hydrodynamica* (1738), gases consist of numerous particles in rapid random motion. He assumed that the pressure of a gas is produced by the direct impact of the particles on the walls of the container.

Newton’s laws of motion and his law of gravitation explain that Earth is not a perfect sphere because of the balance between competing physical forces.12

As Earth rotates on its axis, it generates centrifugal force that acts outward from the center of rotation. This force is strongest at the Equator, where the rotational velocity is highest. According to Newtonian mechanics, this outward force opposes the inward pull of gravity, which acts to pull all matter toward the planet's center of mass.342

The resulting equilibrium between these forces causes Earth to bulge at the equator and flatten at the poles, creating an oblate spheroid shape rather than a perfect sphere. Newton used this theoretical prediction to successfully explain the precession of the equinoxes, and the subsequent confirmation of this equatorial bulge by 18th-century expeditions provided critical evidence for the validity of Newtonian physics.32