Final answer:
During the Middle Ages, the geocentric model, which placed Earth at the universe's center, was prevalent, based on Ptolemy's teachings.
Step-by-step explanation:
The model for understanding the solar system during the Middle Ages was the geocentric model, primarily based on the work of Claudius Ptolemy. In this model, Earth was considered the center of the universe, with the sun, moon, stars, and planets revolving around it. This view was encapsulated in Ptolemy's Almagest and remained dominant until the heliocentric model, proposed by Copernicus, gained acceptance following support from observations by astronomers such as Galileo.
According to the geocentric model, each planet moved in a small circle, called an epicycle, as it orbited Earth. While this model was the dominant cosmological view in medieval Europe, it faced challenges as observations and scientific inquiry progressed. It wasn't until the heliocentric model proposed by Nicolaus Copernicus in the 16th century that a new understanding of the solar system began to take shape, eventually leading to the revolution in astronomical thought during the Renaissance and Scientific Revolution.