which ancient astronomer developed a geocentric model of the universe explaining the observable motions of the planets?

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Geocentric model

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Geocentric model

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"Geocentric" redirects here. For orbits around Earth, see Geocentric orbit. For the coordinate system, see Geocentric coordinates.

— An illustration of the 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the geocentric model (also known as geocentrism, often exemplified specifically by the Ptolemaic system) is a superseded description of the Universe with Earth at the center. Under the geocentric model, the Sun, Moon, stars, and planets all orbit Earth.[1] The geocentric model was the predominant description of the cosmos in many European ancient civilizations, such as those of Aristotle in Classical Greece and Ptolemy in Roman Egypt.

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 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 on a celestial sphere rotating once each day about an axis through the geographic poles of Earth.[2]

Second, Earth seems to be unmoving from the perspective of an earthbound observer; it feels solid, stable, and stationary.

Ancient Greek, ancient Roman, and medieval philosophers usually combined the geocentric model with a spherical Earth, in contrast to the older flat-Earth model implied in some mythology.[n 1][n 2][5] The ancient Jewish Babylonian uranography pictured a flat Earth with a dome-shaped, rigid canopy called the firmament placed over it (רקיע- rāqîa').[n 3][n 4][n 5][n 6][n 7][n 8] However, the Greek astronomer and mathematician Aristarchus of Samos (c. 310 – c. 230 BC) developed a heliocentric model placing all of the then-known planets in their correct order around the Sun.[12] The ancient Greeks believed that the motions of the planets were circular, a view that was not challenged in Western culture until the 17th century, when Johannes Kepler postulated that orbits were heliocentric and elliptical (Kepler's first law of planetary motion). In 1687 Newton showed that elliptical orbits could be derived from his laws of gravitation.

The astronomical predictions of Ptolemy's geocentric model, developed in the 2nd century CE, served as the basis for preparing astrological and astronomical charts for over 1500 years. The geocentric model held sway into the early modern age, but from the late 16th century onward, it was gradually superseded by the heliocentric model of Copernicus (1473–1543), Galileo (1564–1642), and Kepler (1571–1630). There was much resistance to the transition between these two theories. Some felt that a new, unknown theory could not subvert an accepted consensus for geocentrism.

1 Ancient Greece 2 Ptolemaic model

2.1 Ptolemaic system

2.2 Persian and Arab astronomy and geocentrism

3 Geocentrism and rival systems

3.1 Copernican system

4 Gravitation 5 Relativity

6 Religious and contemporary adherence to geocentrism

6.1 Polls

6.2 Historical positions of the Roman Catholic hierarchy

6.3 Orthodox Judaism

6.4 Islam 7 Planetariums 8 See also 9 Notes 10 References 11 Bibliography 12 External links

Ancient Greece[edit]

Illustration of Anaximander's models of the universe. On the left, summer; on the right, winter.

The geocentric model entered Greek astronomy and philosophy at an early point; it can be found in pre-Socratic philosophy. In the 6th century BC, Anaximander proposed a cosmology with Earth shaped like a section of a pillar (a cylinder), held aloft at the center of everything. The Sun, Moon, and planets were holes in invisible wheels surrounding Earth; through the holes, humans could see concealed fire. About the same time, Pythagoras thought that the Earth was a sphere (in accordance with observations of eclipses), but not at the center; he believed that it was in motion around an unseen fire. Later these views were combined, so most educated Greeks from the 4th century BC on thought that the Earth was a sphere at the center of the universe.[13]

In the 4th century BC, two influential Greek philosophers, Plato and his student Aristotle, wrote works based on the geocentric model. According to Plato, the Earth was a sphere, stationary at the center of the universe. The stars and planets were carried around the Earth on spheres or circles, arranged in the order (outwards from the center): Moon, Sun, Venus, Mercury, Mars, Jupiter, Saturn, fixed stars, with the fixed stars located on the celestial sphere. In his "Myth of Er", a section of the , Plato describes the cosmos as the Spindle of Necessity, attended by the Sirens and turned by the three Fates. Eudoxus of Cnidus, who worked with Plato, developed a less mythical, more mathematical explanation of the planets' motion based on Plato's dictum stating that all phenomena in the heavens can be explained with uniform circular motion. Aristotle elaborated on Eudoxus' system.

Source : en.wikipedia.org

1. Which ancient astronomer developed a geocentric model of the universe explaining the observable

1. Which ancient astronomer developed a geocentric model of the universe explaining the observable motions of the planets? - 1979412