Tycho Brahe days days in the year pregnant with misfortune, wherefore in Denmark, up to this very day, the laboring class call such days on which they happen to meet with some unfortunate accident, Tycho Brahe's days." In his travelogue "A Poet's Bazaar", Hans Christian Andersen alludes to the fact that Tycho Brahe died in exile in Prague, observing that "Denmark owns not even his dust; but the Danes mention his name in their bad times, as if a denunciation proceeded out of it: 'These are Tycho Brahe's days!' say they." However, no mention of the Tycho Brahe days is actually found in
Two-body problem in general relativity The Kepler problem derives its name from Johannes Kepler, who worked as an assistant to the Danish astronomer Tycho Brahe. Brahe took extraordinarily accurate measurements of the motion of the planets of the Solar System. From these measurements, Kepler was able to formulate Kepler's laws, the first modern description of planetary motion: Kepler published the first two laws in 1609 and the third law in 1619. They supplanted earlier models of the Solar System, such as those of Ptolemy and Copernicus. Kepler's laws apply only in the limited case of the two-body problem. Voltaire and Émilie du Châtelet were the