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Geocentric model

Geocentric modelIn astronomy, the geocentric model (also known as "geocentrism, "geocentricism," or the Ptolemaic view of the universe), is the theory, now superseded, that the Earth is the center of the universe and other objects go around it. Belief in this system was common in ancient Greece.

It was embraced by both Aristotle (see Aristotelian physics) and Ptolemy, and most, but not all, Ancient Greek philosophers assumed that the Sun, Moon, stars, and naked eye planets circle the Earth. Similar ideas were held in ancient China.
Theory Explanation:
Two common observations were believed to support the idea that the Earth is in the center of the Universe: The first observation is that the stars, sun, and planets appear to revolve around the Earth each day, with the stars circling around the pole and those stars nearer the equator rising and setting each day and circling back to their rising point; the second is the perception that as the Earth is solid and stable it is not moving—but is at rest.
The geocentric model was usually combined with a spherical Earth by ancient Greek and medieval philosophers. It is not the same as the older flat Earth model implied in some mythology. The ancient Greeks believed that the motions of the planets were circular and not elliptical, a view that was not challenged in Western culture before the 17th century.
The predictions of Ptolemy's geocentric model were used for astrology for over 1500 years. The geocentric model held sway into the early modern age; from the late 16th century onward it was gradually replaced by the heliocentric model of Copernicus, Galileo and Kepler.
Not all Greeks agreed with the geocentric model. The Pythagorean system has already been mentioned; some Pythagoreans believed the Earth to be one of several planets going around a central fire. Hicetas and Ecphantus, two Pythagoreans of the 5th century BC, and Heraclides Ponticus in the 4th century BC, believed that the Earth rotated on its axis but remained at the center of the universe. Such a system still qualifies as geocentric. It was revived in the Middle Ages by Jean Buridan. Heraclides Ponticus was once thought to have proposed that both Venus and Mercury went around the Sun rather than the Earth, but this is no longer accepted. Martianus Capella definitely put Mercury and Venus on epicycles around the Sun.
Aristarchus of Samos was the most radical. He wrote a work, which has not survived, on heliocentrism, saying that the Sun was at the center of the universe, while the Earth and other planets revolved around it. His theory was not popular, and he had one named follower, Seleucus of Seleucia.

•    Type→ Basic Science
•    Theorist→ Claudius Ptolemaeus
•    Date → 100 – 170 AC

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