FactSentinel

Earth is not a perfect sphere. It is an oblate spheroid, meaning it bulges at the equator and is slightly flattened at the poles. Earth's rotation causes this shape: the spinning motion generates a centrifugal effect that pushes material outward, strongest at the equator. As a result, Earth's equatorial diameter is about 12,756 kilometers, while its pole-to-pole diameter is roughly 12,714 kilometers, a difference of about 43 kilometers.

The evidence comes from several independent sources. Satellite measurements, including those from geodesy missions and GPS systems, map Earth's shape with remarkable precision. Surveys dating back to the 18th century found that a degree of latitude spans a slightly longer distance near the poles than near the equator, which is consistent with a flattened shape. Gravity measurements also vary by location, since the surface is farther from Earth's center at the equator. Earth's surface is also uneven, with mountains, ocean trenches, and variations in the density of the planet's interior producing a lumpy shape called the geoid.

A common misconception is that the flattening is dramatic. In reality, it is only about 0.3 percent, so Earth appears almost perfectly round in photographs from space. This is why it is often described as "spherical" in everyday conversation. Another point of confusion is that mountains make Earth look rough. Scaled to a billiard ball, Earth would actually be smoother than the ball, though it still falls short of being a mathematically perfect sphere.