Geocentrism is the astronomical theory that considers that the Earth is the center of the Universe and that the different planets revolve around it. This conception of the universe was initiated by Aristotle in the 4th century BC. C and supplemented by Ptolemy later. Geocentrism was accepted as a valid explanation until the new vision of the universe in the 15th century, in which the investigations of Copernicus and then Galileo led to a different theory, heliocentrism (the sun is the center of the universe and all the planets rotate around it).
Understanding Geocentrism on the basis of planetary circular motion
The geocentric theory was based on the circular movements of the planets, called epicycles. On the other hand, there were a series of theoretical principles that supported this vision: the apparent immutability of the Earth, the finiteness of the Universe and that the world was divided into two differentiated spheres (the sublunar sphere and the supralunar sphere).
Why was geocentrism accepted
Although geocentrism is a theory not accepted by the scientific community and only maintained by a few outlandish researchers, one wonders what was the reason for its acceptance for almost twenty centuries. There are several reasons for its success. On the one hand, it was based on the idea that the Earth did not move and, in parallel, occupied the center of the entire universe.
The figure of man at the center of the universe
This vision was reinforced by another consideration: man is the center of creation and, therefore, it was logical to think that everything revolved around the human being, including the planets (this consideration is the central axis of anthropocentrism). Thus, anthropocentrism complemented geocentrism and both theories were admitted by the religious dogma of Christianity.
From an astronomical point of view, geocentrism was based on the belief in the circular motion of the planets, a dogma that seemed unquestionable.
The crisis of geocentrism
Theoretical explanations of geocentrism began to be questioned in ancient times by Aristarchus of Samos, but his contributions were rejected because Aristotle's authority was unquestionable and because the church later supported geocentrism. It was not until the fifteenth century that Copernicus' investigations began to seriously weaken the geocentric theory.
For this reason, we speak of the "Copernican revolution", since his research on planetary movements was decisive for other astronomers to make new contributions to the heliocentric theory.
Among the most relevant contributions that dismantled geocentrism, three very specific ones should be highlighted: Tycho Brahe observed that the spheres of the Moon were not immutable and showed that some data on geocentrism were wrong, Kepler's laws introduced planetary movements based on orbits. Ellipticals and Galileo's planetary observations with the telescope allowed heliocentrism to take over as the astronomical theory that replaced geocentrism.
