Geocentric Model

The Ptolemaic system

Synonym: Ptolemaic World-View

History

Until the Copernican Revolution, the commonly held world-view was that the "sublunar sphere" of the earth is the centre of the universe around which the sun, moon, planets and the fixed stars revolve. The basis for this view is the subjective human perception of the cosmos which is unavoidably geocentric in nature. This idea lay at the heart of the system devised by the ancient Babylonians and was transmitted to medieval Europe via the books of the Hellenistic astrologer and astronomer Ptolemy. It had a lasting influence on cosmological beliefs until Copernicus published his ideas on the heliocentric model. Judaism, Christianity and Islam all lent support to the geocentric world-view because of affirmed scriptural passages that seemingly placed the earth in the center of the cosmos.

The Ptolemaic order of spheres from Earth outward is:

1. Moon (lunar sphere)
2. Mercury
3. Venus
4. Sun
5. Mars
6. Jupiter
7. Saturn (the farthest planet)
8. Fixed stars
9. Primum Mobile (First Moved)

The basic elements of Ptolemaic astronomy

Modern astrology is still based on a geocentric world-view. The reasoning has nothing to do with remaining loyal to tradition or ignoring scientific discoveries but rather because human experience of the cosmos is literally geocentric: humans observe celestial events from the earth. The individual's position is at the centre of a horoscope with the planets rotating around this centre.

See also

• Spherical Observation

Weblinks

• Wikipedia: Geocentric model

Bibliography

• Giorgio de Santillana, 1955, The Crime of Galileo, University of Chicago Press; pp. 40-47, 93