Celestial spheres

From Wikipedia, the free encyclopedia

The celestial spheres, or celestial orbs, are the fundamental element of the geocentric, Ptolemaic system of cosmology, which holds that the universe is comprised of nine spheres of progressively greater size, each sphere enclosing the smaller spheres. In this system, the Earth is the center sphere. Beyond the Earth, in this order, are the spheres of the Moon, Mercury, Venus, the Sun, Mars, Jupiter, Saturn, and the stars. When one sphere moved, its motion caused each sphere internal to it to move, as well.

While Ptolemy standardized this model of the cosmos, it did not originate with him. Ptolemy based his work on similar, more basic cosmological views from earlier Greek philosophers including Plato and Aristotle. Medieval, Christian philosophers modified Ptolemy's system to include a tenth sphere, the outermost, which was the sphere of God. Each sphere was directed by a ruling force, called its intelligence. The outermost sphere, whose movement affected all others, was referred to as the Primum Mobile, the "Prime Mover."

In the late 16th and early 17th centuries CE, the mathematician and astronomer Johannes Kepler dealt with the concept of the spheres in his work Harmonia Mundi. Kepler drew together theories from the world of music, architecture, planetary motion and astronomy and linked them together to form an idea of a harmony and cohesion underlying all world phenomena and ruled by a divine force.

Although this work remained untranslated into English for over 400 years, finally astronomer and mathematician Dr J. Field translated the Latin into English for publication by the American Philosophical Society in Philadelphia:

Aiton, E. J., A. M. Duncan, and J. V. Field The Harmony of the World by Johannes Kepler Memoir 209 (1997)

The earlier French and German translations were of poor quality and incomplete.