Johannes Kepler (idea)

Kepler constructed an interesting model of the Solar System from his observations, constructed of nested regular polyhedra and spheres:

• The orbit of Saturn
  
  • A cube inscribed in the sphere
    
    • the orbit of Jupiter: A sphere inscribed in the cube
      
      • A tetrahedron inscribed in that sphere
        
        • The orbit of Mars: A sphere inscribed in the tetrahedron
          
          • A dodecahedron inscribed in that sphere
            
            • The orbit of the Earth; a sphere inscribed in the dodecahedron
              
              • An icosahedron inscribed in that sphere
                
                • The orbit of Venus inscribed in the icosahedron
                  
                  • An octahedron inscribed in that sphere
                    
                    • The orbit of Mercury inscribed in the octahedron.

The regular solids and spheres supposedly rubbed together, producing the music of the spheres¹.

Now, although this seems bizarre to us today, it fit the observations of the day fairly well.

It predicts the distances of the orbits of the planets fairly well (within about 10 percent) and seemed to explain that there were six planets because there were five regular solids.

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¹I think I need to go put Astronomy Domine on now.