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In astronomy, the geocentric model (also known as geocentrism, often exemplified specifically by the Ptolemaic system) is a superseded description of the Universe with Earth at the center. Under most geocentric models, the Sun , Moon , stars , and planets all orbit Earth.
Figure of the heavenly bodies — an illustration of the Ptolemaic geocentric system by Portuguese cosmographer and cartographer Bartolomeu Velho, 1568 (Bibliothèque Nationale, Paris), depicting Earth as the centre of the Universe
Counting the total number is difficult, but estimates are that he created a system just as complicated, or even more so. [16] Koestler, in his history of man's vision of the universe, equates the number of epicycles used by Copernicus at 48. [17] The popular total of about 80 circles for the Ptolemaic system seems to have appeared in 1898.
English: The Ptolemaic geocentric model of the Universe according to the Portuguese cosmographer and cartographer Bartolomeu Velho (Bibliothèque Nationale de France, Paris). Español : El modelo geocéntrico del universo de Ptolomeo , de acuerdo al cosmógrafo y cartógrafo portugués Bartolomeu Velho (Biblioteca Nacional de Francia, París).
In classical, medieval, and Renaissance astronomy, the Primum Mobile (Latin: "first movable") was the outermost moving sphere in the geocentric model of the universe. [ 1 ] The concept was introduced by Ptolemy to account for the apparent daily motion of the heavens around the Earth, producing the east-to-west rising and setting of the sun and ...
The basic elements of Ptolemaic astronomy, showing a planet on an epicycle (smaller dashed circle), a deferent (larger dashed circle), the eccentric (×) and an equant (•). Equant (or punctum aequans) is a mathematical concept developed by Claudius Ptolemy in the 2nd century AD to account for the observed motion of the planets. The equant is ...
The Ptolemaic system used in ancient Greek astronomy placed the planets by order of proximity to Earth in the then-current geocentric model, closest to furthest, as the Moon, Mercury, Venus, Sun, Mars, Jupiter, and Saturn. [16]
These were based on a Ptolemaic, geocentric model of the Solar System. Although the Alphonsine tables were not very accurate, nothing else was available and so they continued to be used. Although the Alphonsine tables were not very accurate, nothing else was available and so they continued to be used.