Which theory states that the Earth is at the center of the universe?

The Ptolemaic Theory, proposed by Claudius Ptolemy in the 2nd century, posits that the Earth is the center of the universe, with all celestial bodies, including the sun and the stars, revolving around it. This geocentric model dominated astronomical thought for many centuries and was widely accepted in both the scientific and philosophical communities.

Ptolemy's system included complex models to explain the apparent retrograde motion of planets and accounted for their observed paths by introducing epicycles (small circular orbits superimposed on larger circular orbits). This model reflected the astronomical observations and conceptual framework of the time, making it a cornerstone of medieval cosmology.

In contrast, the other theories mentioned revolutionized our understanding of the universe. The Galilean Theory, associated with Galileo Galilei, supported a heliocentric view, which placed the sun at the center. The Newtonian Theory, based on Isaac Newton's laws of motion and universal gravitation, further established a more comprehensive understanding of celestial mechanics without explicitly naming a center. The Copernican Theory, introduced by Nicolaus Copernicus, directly challenged the Ptolemaic view by asserting that the sun is the center of the solar