Astronomical Images : The dimensions and distances of planetary orbs

Johannes Kepler

Astronomical Images

<p style='text-align: justify;'>This heliocentric model of Plate [<i>Tabula</i>] 3 shows the six planetary orbs - of Mercury, Venus, Earth, Mars, Jupiter and Saturn - inscribing and circumscribing the five so-called Platonic solids - the regular octahedron, icosahedron, dodecahedron, tetrahedron and cube. The eccentricities of the planets' paths, and hence the thicknesses of their orbs, are indicated by the epicycles adjacent to the planetary signs within each orb. Kepler regarded the nested solids as a proof for the Copernican hypothesis, as he points out in the 'primary derivation' (summarised below). The model is dedicated to Friedrich, Duke of Wuerttemberg, who had commissioned a drink-dispenser based on it, with the planetary hemispheres serving appropriate beverages - a project that was, alas, abandoned.</p>