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The geocenter (from Greek γῆ Ge , German 'the earth' ), also the center of the earth , is the center of gravity of the earth .

The term geocentric is used in various natural sciences for those data , calculations and models that relate to the earth and in particular to the center of the earth.

The geocenter

Even when viewed ideally at sea ​​level, the earth's surface is not equally far from the center of the earth at all points, since the earth is not a geometric sphere . Rather, the earth figure can be described much better approximately by means of an ellipsoid of revolution. The diameter of the earth, which is over 12,700 kilometers, is therefore about 42 km less between the poles than the diameter at the equator . The earth figure is described even more precisely by the geoid .

Geocentric data

Geocentrically characterizes the reference system most favorable for astronomy and geodesy in the earth's center of gravity or in the center of the earth's ellipsoid . In contrast, we know:

In the geocentric coordinate system measured data include:

The geocentric and bary- or heliocentric directions to celestial bodies differ depending on their distance. In the case of planets , values ​​can be up to 180 ° (e.g. during a solar eclipse or Venus passage ), in the case of nearby stars up to 0.7 ″ ( parallax of Alpha Centauri ).

The geocentric worldview

The " geocentric worldview " concerns another aspect of the word. It is the interpretation of astronomical phenomena from the point of view of an observer on earth, the size of which is considered to be almost zero compared to the sphere ( celestial sphere ). Therefore this system can be both geocentric in the above sense and topocentric .

The geocentric worldview was widespread from antiquity to the Renaissance and was replaced by the heliocentric worldview in the 17th century.

See also

Web links

Wiktionary: geocentric  - explanations of meanings, word origins, synonyms, translations