Tychonic system

The Tychonic system (or Tychonian system) is a model of the Solar system published by Tycho Brahe in the late 16th century which combines what he saw as the mathematical benefits of the Copernican system with the philosophical and "physical" benefits of the Ptolemaic system. The model may have been inspired by Valentin Naboth and Paul Wittich, a Silesian mathematician and astronomer. A similar yet mathematically more efficient geoheliocentric model was also proposed a century earlier by Nilakantha Somayaji of the Kerala school of astronomy and mathematics.

It is essentially a geocentric model; the Earth is at the center of the universe. The Sun and Moon and the stars revolve around the Earth, and the other five planets revolve around the Sun. It can be shown that the motions of the planets and the Sun relative to the Earth in Brahe's system are mathematically equivalent to the motions in Copernicus' heliocentric system.

Tycho admired aspects of Copernicus's heliocentric model of the solar system, but felt that it had problems as concerned physics, astronomical observations of stars, and religion. Regarding the Copernican system Tycho wrote,

This innovation expertly and completely circumvents all that is superfluous or discordant in the system of Ptolemy. On no point does it offend the principle of mathematics. Yet it ascribes to the Earth, that hulking, lazy body, unfit for motion, a motion as quick as that of the aethereal torches, and a triple motion at that.

In regard to physics, Tycho held that the Earth was just too sluggish and heavy to be continuously in motion. According to the accepted Aristotelian physics of the time, the heavens (whose motions and cycles were continuous and unending) were made of "Aether" or "Quintessence"; this substance, not found on Earth, was light, strong, and unchanging, and its natural state was circular motion. By contrast, the Earth (where objects seem to have motion only when moved) and things on it were composed of substances that were heavy and whose natural state was rest—thus the Earth was a "lazy" body that was not readily moved. Thus while Tycho acknowledged that the daily rising and setting of the sun and stars could be explained by the Earth's rotation, as Copernicus had said, still

...
Wikipedia