page_title: Geocentric model
section_title: Geocentrism and rival systems
hierarchical_section_title: Geocentric model / Geocentrism and rival systems
caption_attribution_description: English: The geocentric world view. From an Icelandic manuscript, written between 1747 and 1752. Now in the care of the Icelandic National Library. See here: https://handrit.is/is/manuscript/imaging/is/JS08-0392/161r-198v#page/165v++(10+af+76)/mode/2up
context_page_description: In astronomy, the geocentric model is a superseded description of the Universe with Earth at the center. Under the geocentric model, the Sun, Moon, stars, and planets all orbited Earth. The geocentric model was the predominant description of the cosmos in many 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.
  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.
context_section_description: 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 in orbit 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.
caption: This drawing from an Icelandic manuscript dated around 1750 illustrates the geocentric model.
exif: {}