Many readers ask a simple question: what is the exact radius of the Earth? The standard answer used by scientists is a mean radius of about 6,371 kilometers. That figure is a useful average, but the planet is not a perfect sphere. The equatorial radius measures roughly 6,378.1 km, while the polar radius is about 6,356.8 km, a difference of roughly 21 kilometers caused by Earth’s equatorial bulge.D...More