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Earth radius (denoted as R 🜨 or R E) 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 (an oblate ellipsoid), the radius ranges from a maximum (equatorial radius, denoted a) of nearly 6,378 km (3,963 mi) to a minimum (polar radius, denoted b) of nearly 6,357 km (3,950 mi).
The Earth's radius is the distance from Earth's center to its surface, about 6,371 km (3,959 mi). While "radius" normally is a characteristic of perfect spheres, the Earth deviates from spherical by only a third of a percent, sufficiently close to treat it as a sphere in many contexts and justifying the term "the radius of the Earth".
(110–210 Earth radii) 6.36×10 6 –1.27×10 7: The space dominated by Earth's magnetic field and its magnetotail, shaped by the solar wind. [17] Earth's orbit: 299.2 million km [b] 2 AU [c] 2.99×10 8: The average diameter of the orbit of the Earth relative to the Sun. Encompasses the Sun, Mercury and Venus. [18] Inner Solar System ~6.54 AU ...
In the WGS-84 standard Earth ellipsoid, widely used for map-making and the GPS system, Earth's radius is assumed to be 6 378.137 km (3 963.191 mi) to the Equator and 6 356.752 3142 km (3 949.902 7642 mi) to either pole, meaning a difference of 21.384 6858 km (13.287 8277 mi) between the radii or 42.769 3716 km (26.575 6554 mi) between the ...
The first known scientific measurement and calculation was done by Eratosthenes, by comparing altitudes of the mid-day sun at two places a known north–south distance apart. [3] He achieved a great degree of precision in his computation. [4] The Earth's shape deviates from spherical by flattening, but by only about 0.3%.
A data set which describes the global average of the Earth's surface curvature is called the mean Earth Ellipsoid. It refers to a theoretical coherence between the geographic latitude and the meridional curvature of the geoid. The latter is close to the mean sea level, and therefore an ideal Earth ellipsoid has the same volume as the geoid.
Since experts started measuring the Anomaly a few decades ago, it has grown in size and now covers a fifth (20.3%) of Earth’s surface, with no signs of shrinking anytime soon.
[87] [88] Earth's shape also has local topographic variations; the largest local variations, like the Mariana Trench (10,925 metres or 35,843 feet below local sea level), [89] shortens Earth's average radius by 0.17% and Mount Everest (8,848 metres or 29,029 feet above local sea level) lengthens it by 0.14%.