Christoph Rothmann computed and implemented the Kassel star catalog between 1585 and 1587 almost exclusively under the technical sponsorship of Prince Wilhelm IV. Rothmann was a convinced follower of Nikolaus
Copernicus, who justified the
heliocentric view of the world. In contrast to his prominent astronomical colleagues he fell into oblivion in the 17th century. In the 16th century in Europe two groups of researchers with the list of new more exact star catalogs had out-done. On side the well-known Dane
Tycho Brahe, who had established the famous observatory
Uraniborg on the island Ven, and a group of astronomers in Kassel at the court of the prince. Here Rothmann and
Joost Bürgi, a Swiss mathematician, worked. The two working groups maintained a scientific exchange like an extensive exchange of letters between Kassel and Ven. An often quoted letter between Rothmann and Brahe pointed out the whole dilemma of the physics at that time. Brahe distrusted the heliocentric view of the world of Nikolaus
Copernicus, and raised in a letter to Rothmann the following objection against the movement of the Earth:
"if the Earth actually turns from west to east, then a cannon ball, which is shot toward the turning of the Earth, must continue to fly as fast as a projectile fired in opposite direction." Rothmann answered that both projectile and cannon would participate in the movement of the Earth and so that his objection was invalid. This contradicted however the Aristotelian view of motion then valid in Europe. At that time this was so fundamental a contradiction that it could only be eliminated in the middle the 17th century with the discovery of the force of gravity. The crater
Rothmann on the
Moon is named after him. == Writings ==