The document discusses the history of models of the universe from ancient geocentric to modern heliocentric models. It describes early geocentric models from Thales of Miletus, Anaximander of Miletus, and Pythagoras that proposed the Earth was flat or cylindrical at the center. Later models from Ptolemy, Aristotle, and others incorporated spheres to explain planetary motions. The heliocentric model was proposed by Aristarchus of Samos but gained acceptance after Copernicus' "On the Revolution of Celestial Orbs" in 1543 despite religious objections. Key figures like Brahe, Galileo, and Kepler further developed and supported the heliocentric model through observations and Kepler's laws