This is one of the first major works of Kepler (1597); compiled in Mysterium Cosmographicum or Mystery of the Cosmos where he lays out an entire philosophy of the structure of universe in this lengthy book volume. His philosophy favored the Copernican system (which earlier introduced the idea that the planets revolved in a complex system of epicycles, but revolved around the sun) and he advocated a heliocentric system, which implied that the center of the universe is the Sun. The “heliocentric theory” was still new, untested and an unpopular idea in his times. On the other hand, Copernican system was found to be mathematically sound, but physically implausible. Also, since the earlier view in sixteenth century believed that the universe was geocentric; i.e., with earth as the center of universe, Copernicus’s views/theories were a shock to his co-existing astronomers. Therefore, this particular piece of work was very crucial and the first of its kind that acknowledged Copernican system since Copernicus’s death, fifty years back. The view of Kepler was different from that of others and he stayed unique in the sense that, he stood away from the crowd. He wanted to fit the theories to “existing things” in nature. He had great ideas on the layout of universe but the ideas didn’t appeal his contemporaries, as they believed that, orbits of six planets could fit around the five perfect solids (cube: six square sides, tetrahedron: four triangular sides, octahedron: eight triangular sides, dodecahedron: twelve pentagonal sides, and icosahedron: twenty triangular sides). Each perfect solid can be further inscribed in and circumscribed around a sphere.
In Kepler’s system, inscribed in a cube, is the orbit of Jupiter, which circumscribes a tetrahedron. Inscribed in a tetrahedron, is the orbit of Mars, which circumscribes a dodecahedron. Inscribed in the dodecahedron, is the orbit of Earth, which circumscribes an icosahedron. Inscribed in an icosahedron is the orbit of Venus, which circumscribes a octahedron. Finally, the orbit of Mercury is inscribed in the octahedron. As intriguing as it was, this was a beautiful creation of Kepler and it was widely accepted later.
Although not mathematically perfect, the construction looked good and it did fit well with the approximate orbits of the planet. Therefore, he devoted a large portion of this book volume to compare actual astronomical observations to his predictions, working out on the approximate differences as well. Kepler illustrated his theory with sheer confidence and he trusted his ideas.
He also went to the extent of believing that if facts didn’t fit his theory, there could be some flaws with the facts themselves. Therefore, he started to play around with the numbers and tried to find ways in which the observations could be reinterpreted. One of his ideas was to take a closer look at the center of the planetary orbits. Earlier view of Copernicus believed that, planets orbited around an imaginary point in space. But Kepler put the “sun” in the physical center of the universe. Although this shift didn’t help the theory of perfect solids system, he deduced a very important fact that no one had ever imagined. He moved the sun to the center of the universe, replacing an imaginary point with a physical object, thus making a gigantic leap toward achieving an accurate physical picture of the universe. Kepler realized that the position of sun in the center of universe made a lot of sense and that it was the most powerful object of the universe. Also, he firmly believed that the sun was mainly responsible for the motion of planets. He imagined a force originating from the sun that controlled the circular motion of planets around it in their orbits and grew weaker with their relative distance from the sun. But later, this idea was proved to be wrong and the force that he imagined was far from the concept of “gravitational force” that in reality guides the planets around their rrespective orbits. Nonetheless, his idea was found to be revolutionary as it provided some elementary explanation for the celestial motion of the planets. Indeed, what we know now as the solar system is basically governed by our most gracious sun with nine planets revolving around it, in a most concerted fashion, and we as members of the living planet, the earth, appreciate and adore this fact. Thanks to the great astronomers like Copernicus, Kepler, and Ptolemy to name a few, who made great efforts to resolve the mysteries of this unverse and put forth their greatest discoveries with solid proofs, which we now strongly believe.