Editing Geocentric model (section)

{{Short description|Superseded description of the Universe with Earth at the center}}
{{Redirect| Geocentric|orbits around Earth|Geocentric orbit|the coordinate system|Geocentric coordinates}}
{{Use American English|date=January 2024}}
[[File:Bartolomeu Velho 1568.jpg|thumb|upright=1.35|''Figure of the heavenly bodies'' – An illustration of a Ptolemaic geocentric system by Portuguese cosmographer and cartographer [[Bartolomeu Velho]], 1568 (Bibliothèque Nationale, Paris)]]

In [[astronomy]], the '''geocentric model''' (also known as '''geocentrism''', often exemplified specifically by the '''Ptolemaic system''') is a [[superseded scientific theories|superseded]] description of the [[Universe]] with [[Earth]] at the center. Under most geocentric models, the [[Sun]], [[Moon]], [[star]]s, and [[classical planet|planets]] all [[orbit]] Earth. The geocentric model was the predominant description of the cosmos in many European [[Ancient history|ancient]] civilizations, such as those of [[Aristotle]] in Classical Greece and [[Ptolemy]] in Roman Egypt, as well as during the [[Islamic Golden Age]].

Two observations supported the idea that Earth was the center of the Universe. First, from anywhere on Earth, the Sun appears to revolve around Earth [[diurnal motion|once per day]]. While the Moon and the planets have their own motions, they also appear to revolve around Earth about once per day. The stars appeared to be [[fixed stars|fixed]] on a [[celestial sphere]] rotating once each day about [[celestial pole|an axis]] through the [[geographic pole]]s of Earth.{{sfn|Kuhn|1957|pp= 5–20}} Second, Earth seems to be unmoving from the perspective of an earthbound observer; it feels solid, stable, and stationary.

[[ancient Greece|Ancient Greek]], [[ancient Rome|ancient Roman]], and [[Middle Ages|medieval]] philosophers usually combined the geocentric model with a [[spherical Earth]], in contrast to the older [[flat Earth|flat-Earth]] model implied in some [[mythology]]. However, the Greek astronomer and mathematician [[Aristarchus of Samos]] ({{circa|310|230 BC}}) developed a [[heliocentric model]] placing all of the then-known planets in their correct order around the Sun. The ancient Greeks believed that the motions of the planets were [[circular orbit|circular]], a view that was not challenged in [[Western culture]] until the 17th century, when [[Johannes Kepler]] postulated that orbits were heliocentric and [[elliptic orbit|elliptical]] (Kepler's [[Kepler's laws of planetary motion#First law|first law of planetary motion]]). In 1687, [[Isaac Newton]] showed that elliptical orbits could be derived from his laws of gravitation.

The astronomical predictions of [[#Ptolemaic system|Ptolemy's geocentric model]], developed in the 2nd century of the Christian era, served as the basis for preparing [[astrology|astrological]] and [[star chart|astronomical charts]] for over 1,500 years. The geocentric model held sway into the [[early modern]] age, but from the late 16th century onward, it was gradually [[Superseded scientific theories#Superseded astronomical and cosmological theories|superseded]] by the heliocentric model of [[Copernicus]], [[Galileo Galilei|Galileo]], and [[Kepler]]. There was much resistance to the transition between these two theories, since for a long time the geocentric postulate produced more accurate results. Additionally some felt that a new, unknown theory could not subvert an accepted [[Scientific consensus|consensus]] for geocentrism.