In the geocentric model of the Solar System, Earth is in the center of the system, with the planets moving around it at the speed called orbital velocity. In the current heliocentric model, however, the Sun is the center of the Solar System. Apollonius, an astronomer from ancient Greece, made the foundation for these models by discovering that planets move in a circle called an epicycle (Ge, 2021). Another astronomer, Hipparchus, only known to the present-day scholars from Ptolemy’s works, modified Apollonius’s theory by adding that Earth slightly deviates from the center (Ge, 2021). Ptolemy, a Greek or a Hellenized man from the era of the Roman Empire, established the theory in its final form. He used the works of his predecessors to explain the motion of the Sun, the Moon, and the planets (Ge, 2021). Thus, the geocentric model has a long history of hundreds of years.
In the 13th century, the Christian church decided to include the works of Ptolemy in its ideology. The geocentric model became a demonstration of God’s will and omnipotence (Ge, 2021). However, during the Renaissance, an unprofessional Polish astronomer called Copernicus created the heliocentric model, putting the Sun into the middle of the system. The supposed movement of planets and stars around Earth was acknowledged to only be an illusion (Ge, 2021). Being afraid of the church, Copernicus delayed publishing this information, only doing so shortly before his death. Some of the most dedicated followers of the then-novel heliocentric model, Giordano Bruno and Galileo Galilei, faced trials from the Inquisition for their point of view, which resulted in execution for Bruno. Therefore, it was considerably difficult for the more progressive heliocentric model to take the precedence it currently holds.
Ge, Y. (2021). From geocentric to heliocentric: How discoveries are Mamde. Springer Publishing.