Tycho Brahe days list. One should also note that Denmark was on the Julian calendar until 1700, when it switched to the Gregorian calendar. Medieval calendars often contained lists of "dies Ægyptiaci", "Egyptian days", that also were held to be unlucky. The Egyptian days were: These too were days considered unlucky to begin any enterprise. Physicians were especially discouraged from performing bloodletting on the Egyptian days. Tycho Brahe days In the folklore of Scandinavia, Tycho Brahe days (Danish: "Tycho Brahes-dage"; Norwegian: "Tycho Brahedager"; Swedish: "Tycho Brahe-dagar") are days judged to be especially unlucky, especially for magical work, and important business transactions[ and personal
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