The solids as dimensional intervals between the six worlds.
"The Earth [the sphere of the Earth] is the measure for all other orbits. Circumscribe a twelve-sided regular solid about it; the sphere stretched around this will be that of Mars. Let the orbit of Mars be circumscribed by a four-sided solid. The sphere which is described about this will be that of Jupiter. Let Jupiter's orbit be circumscribed by a cube. The sphere described about this will be that of Saturn. Now, place a twenty-sided figure in the orbit of the Earth. The sphere inscribed in this will be that of Venus. In Venus' orbit place an octahedron. The sphere inscribed in this will be that of Mercury. There you have the basis for the number of planets."
Kepler eventually disproved his own theory when he discovered that the orbits of the planetary bodies were not perfect circles, as once thought, but rather ellipses. This lead to he discovery of Kepler's Three Laws, which are still in use by astronomer's today. And, of course, his law that "an orbiting body sweeps out equal areas of space in equal times, no matter what its position along the orbit" contributed to the formulation of concepts for hypergeometric mathematics, which forms the basis of the natural world.
Hell; octahedron; Hungry Ghosts; icosahedron; Animals; dodecahedron; Man; tetrahedron; demi-gods; cube; Gods.
In his Mysterium Cosmographicum, Kepler also associates the platonic solids to each of the Universal Elements; air, water, universe, fire and earth. It is clear from this that the world of man and animals. therefore the Earth, exists collectively in the element known as Universe, and this describes why this 'bardo' is of such great importance to Tibetan Mysticism, and the path to achieving enlightenment.