Title: Kepler - preliminary diagram relating to the orbits of Saturn and Jupiter, from Mysterium cosmographicum
Original Format: photograph: negative
Description: With this first diagram, Kepler thought that he had discovered the key to unlocking a geometrical secret about the creation of the universe. His education at the university of Tubingen with Michael Maestlin had already convinced him of the truth of the Copernican system, and starting in 1595, he was trying to explain the relationship among the distances of the planets from the sun and the length of their revolutionaround the sun. The diagram came to Kepler as a revelation. As he was explaining some astrological matters to his students, he drew triangles inscribed in the same circle - or nearly triangles since the end of one made up the beginning of the next one. The crossing points of these triangles formed another circle, half the size of the first one. That proportion, he realized, was the same as the proportion between the orbits of Saturn and Jupiter. The importance of the Mysterium Cosmographicum doesn’t lie in its scientific value, but more in Kepler’s processes since he didn’t just present the result of his researches (such as the world system inscribed in the five regular bodies, which he considered at that time as an real achievement in favor of the Copernican system), but he also shows to the reader all his beginnings and errors, as it is the case with that diagram.