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equatorial bulge
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Diagram showing two positions of Earth in its orbit around the Sun, labeled A for summer and B for winter, with arrows indicating forces Fa and Fb acting on the planet's equatorial bulges. These forces, shown at different points on the Earth's surface, illustrate how they contribute to the precession of Earth's axis. The Sun is centered between the two Earth positions, and both axes are tilted. Measurement points a and b, as well as torque ?, are also labeled.
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equatorial bulge

geophysics
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Diagram showing two positions of Earth in its orbit around the Sun, labeled A for summer and B for winter, with arrows indicating forces Fa and Fb acting on the planet's equatorial bulges. These forces, shown at different points on the Earth's surface, illustrate how they contribute to the precession of Earth's axis. The Sun is centered between the two Earth positions, and both axes are tilted. Measurement points a and b, as well as torque ?, are also labeled.
forces acting on Earth's equatorial bulges Figure 25: Forces acting on equatorial bulges in (A) the summer and (B) the winter cause the axis of Earth to precess (see text).

The equatorial bulge refers to the slight bulging of Earth at its equator. This bulge is a result of the centrifugal force generated by Earth's rotation. Consequently, Earth is not a perfect sphere but rather an oblate spheroid, with its equatorial diameter being slightly larger than its polar diameter. This bulge influences the gravitational field and the orbits of satellites. If Earth were to stop rotating, this centrifugal force would cease, and the planet would gradually reshape into a more perfect sphere, causing significant shifts in oceans and atmosphere.1234

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
4 Britannica Sources
  1. What Would Happen if Earth Stopped Rotating?
  2. gravity - Weighing the Earth
  3. Equator
  4. celestial mechanics - Examples of perturbations

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