Earth radius

Scale drawing of the oblateness of the 2003 IERS reference ellipsoid. The outer edge of the dark blue line is an ellipse with the same eccentricity as that of the Earth, with north at the top. For comparison, the outer edge of light blue area is a circle of diameter equal to the minor axis. The red line denotes the Karman line and the yellow area, the range of the International Space Station.

Al-Biruni's (973–1048) method for calculation of the Earth's radius improved accuracy.

Earth radius is the distance from the Earth's center to its surface, about 6,371 kilometers (3,959 mi). This length is also used as a unit of distance, especially in astronomy and geology, where it is usually denoted by R_⊕.

This article deals primarily with spherical and ellipsoidal models of the Earth. See Figure of the Earth for a more complete discussion of the models. The Earth is only approximately spherical, so no single value serves as its natural radius. Distances from points on the surface to the center range from 6,353 km to 6,384 km (3,947–3,968 mi). Several different ways of modeling the Earth as a sphere each yield a mean radius of 6,371 kilometers (3,959 mi).

单词	Authalic radius
释义	Authalic radius 英语百科 Earth radius Earth radius is the distance from the Earth's center to its surface, about 6,371 kilometers (3,959 mi). This length is also used as a unit of distance, especially in astronomy and geology, where it is usually denoted by R_⊕. This article deals primarily with spherical and ellipsoidal models of the Earth. See Figure of the Earth for a more complete discussion of the models. The Earth is only approximately spherical, so no single value serves as its natural radius. Distances from points on the surface to the center range from 6,353 km to 6,384 km (3,947–3,968 mi). Several different ways of modeling the Earth as a sphere each yield a mean radius of 6,371 kilometers (3,959 mi).
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Authalic radius

Earth radius