Earth radius

Earth radius (denoted as R๐Ÿœจ or ) is the distance from the center of Earth to a point on or near its surface. Approximating the figure of Earth by an Earth spheroid, the radius ranges from a maximum of nearly 6,378 km (3,963 mi) (equatorial radius, denoted a) to a minimum of nearly 6,357 km (3,950 mi) (polar radius, denoted b).

Earth radius
Cross section of Earth's Interior
General information
Unit systemastronomy, geophysics
Unit ofdistance
1 R๐Ÿœจ in ...... is equal to ...
   SI base unit   6.3781ร—106 m[1]
   Metric system   6,357 to 6,378 km
   English units   3,950 to 3,963 mi

A nominal Earth radius is sometimes used as a unit of measurement in astronomy and geophysics, which is recommended by the International Astronomical Union to be the equatorial value.[1]

A globally-average value is usually considered to be 6,371 kilometres (3,959 mi) with a 0.3% variability (ยฑ10 km) for the following reasons. The International Union of Geodesy and Geophysics (IUGG) provides three reference values: the mean radius (R1) of three radii measured at two equator points and a pole; the authalic radius, which is the radius of a sphere with the same surface area (R2); and the volumetric radius, which is the radius of a sphere having the same volume as the ellipsoid (R3).[2] All three values are about 6,371 kilometres (3,959 mi).

Other ways to define and measure the Earth's radius involve the radius of curvature. A few definitions yield values outside the range between polar radius and equatorial radius because they include local or geoidal topography or because they depend on abstract geometrical considerations.

Share this article:

This article uses material from the Wikipedia article Earth radius, and is written by contributors. Text is available under a CC BY-SA 4.0 International License; additional terms may apply. Images, videos and audio are available under their respective licenses.