From: 3blue1brown
Johannes Kepler sought to prove what he considered the most elegant theory in astronomy [00:00:00]. His initial model for the solar system proposed a geometric arrangement involving nested spheres and Platonic solids [00:00:32].
The Platonic Solids Theory
Kepler’s theory envisioned six spheres, corresponding to the six then-known planets [00:00:23]. The arrangement was as follows:
- An octahedron inscribed within a sphere [00:00:04].
- The smallest possible sphere fit around that [00:00:07].
- An icosahedron fit around that sphere [00:00:10].
- Another sphere layered on [00:00:13].
- A dodecahedron [00:00:14].
- One more sphere [00:00:16].
- A tetrahedron [00:00:17].
- One more sphere [00:00:19].
- A cube [00:00:20].
- A final sphere [00:00:21].
Kepler hypothesized that the ratios between the sizes of these six spheres would precisely match the ratios of the orbits of the six known planets [00:00:23], believing this set of ratios to be natural or universal due to the involvement of Platonic solids [00:00:33].
Confrontation with Data and its Outcome
To validate his theory, Kepler acquired orbital data [00:00:38]. Although his method of obtaining and working with this data was described as “heroic” [00:00:43], his geometric model ultimately failed to fit the observations, consistently being off by a few percent [00:00:46].
Despite starting with an incorrect premise, this rigorous attempt to confirm his theory paradoxically led Kepler to become the first person to truly understand how planets orbit the Sun [00:00:50] and to the development of his famous astronomical laws [00:00:56].