Eudoxus' Planetary Model
Eudoxus of Critus devised an astronomical system, which lines among the most
notable products of Greek genius. This is a simulation of the planetray model
which he devised. He explained the motions of sun, moon, and planets by means
of concentric spheres. He used four spheres in his model. These four spheres
are performing uniform rotations around the earth which is the blue colored
sphere in the center.In this model, the outer most sphere moves from east to
west once every 24 hours on an axis passing through the Polaris. Witin this
sphere and inclined to it at a 23 1/2 degree angle is second sphere. Moon is
the third sphere, 90 degree down from the axis of rotation. The third sphere
is inclined at 5 degree to te second sphere. The fourth sphere, carries the
planet to a point on its equator and its axis has an inclination towards small
angle relative to the third axis. The fourth sphere also carries a planet,
which has been given a red color in this model.