PRIDE CHEKERAwasn’t orbiting around Earth. According to Ptolemaic
cosmological model, Earth was regarded as the center of the
universe. He believed that the five known planets at that time,
Mercury, Venus, Mars, Jupiter and Saturn visible to the naked
eye, were defining small, uniform, circular orbits called
epicycles. The centers of these epicycles were orbiting Earth
about a circular orbital trajectory called deferent. Ptolemy
complicated his model by later shifting the deferent about Earth
to a certain distance from Earth and introduced other circular
uniform motions about another axis called equant point. This
very complex model was so difficult to comprehend that
Alfonso X, the King of Castile said, “If the Load Almighty had
consulted me before embarking upon Creation, l should have
recommended something simpler.”
This Ptolemaic cosmological model was accepted for centuries
and believed to be the, objectively, authentic picture of the
universe. It was in the 16th century when Kopernik proposed a
new, different model. He discovered that Earth was not the
center of the universe, but the sun was the center of our solar
system around which other planets orbit, not all those stars seen.
Rigorous calculations in the 20th century proved that there is no
center to our universe, since its topology resembles that of a 3-
sphere. This heliocentric model of Kopernik was not easily
accepted until 17th century, when Galileo Galilei proved it
correct.