Tychonian system

The Tychonian system was an effort by Tycho Brahe to create a model that allows for observations such as the phases of Venus within a geocentric model. In the Tychonian system, the earth is in the center of the universe, the sun revolves around the earth and the other planets revolve around the sun. It can be shown through a geometric argument that the motions of the planets in the Tychonian system are equivalent to the motions in the Copernican system, and the Tychonian system has the advantage of not predicting parallax which was not observable in the 16th century.

Ultimately the Tychonian system was rejected by the observations of Johannes Kepler who demonstrated that the orbits of the planets are ellipses and not circles.