The geocentric model, in all of its complexity, survived scientific scrutiny for almost 1400 years. However, in modern astronomy, scientists seek to explain the natural and physical world we live in as simply as possible. The complexity of Ptolemy's model was an indicator that his theory was inherently flawed. Why, then, was the geocentric model the leading theory for such a long time, even though the heliocentric model more simply explained the observed motions and brightness of the planets?

The geocentric model appealed to mans' vanity, being in the center of everything. Simply, it satisfied their self-thought thus leaving no room for questioning its validity.

Explanation:

The geocentric and heliocentric models were the two main models proposed on how our solar system is laid out. Geocentric, coming from the word 'geo' meaning earth and 'centric' being center said that the Earth was the center of our solar system and the rest of the planets rotated and revolved around it. This model appealed to mans' vanity, this theory was promoted by Egyptian mathematician, Ptolemy. This theory was incorporated into religious dogma thus creating false credit. Ptolemy's calculations were correct, but his assumptions were not: the earth was motionless, circular orbits for planets, all celestial bodies orbit the earth etc. This was until Keppler and Galielo proved him wrong with his assumptions giving rise to the valid, Heliocentric model where the sun is the center of our solar system, planets have elliptical orbits and other planets had bodies orbiting them.