The Painting is "The School of Athens" by Raphael (1483–1520). Note that Plato is pointing up while Aristotle is pointing down.

Plato (400 BC) - Declared that the Earth was imperfect and changeable while the heavens were perfect and immutable.

Aristotle (350 BC) - Universe consists of a perfect celestial sphere rotating around a fixed Earth at the center of the Universe.

Aristarchus from Samos (250 BC) - Theorized the "radical" view that the Earth and all the Planets revolve around the Sun: The Heliocentric model. The model was not accepted because it contradicted the "Great" Aristotle and predicted parallax; the change in the position of the stars as the Earth moves. Note that Aristarchus also said that stellar parallax will not be observed because the stars were very far away. A man 17 centuries ahead of his time!

Erastothenes (200 BC) - A Greek astronomer and mathematician, he was first to measure the Earth's diameter by waiting until the Sun illuminated the bottom of a well in Syene. At the same time of day, the Sun was at 7 degrees zenith angle in Alexandria.

Ptolemy (140 AD) - Adopted Aristotle's Geocentric(or earth-centered) model. All heavenly bodies move in uniform circular motion around the Earth. For almost 1,500 years all of Astronomy was summarized in Ptolemy's book known now as Almagest (Greatest). However, ... planets do not move in simple circular orbits around the Earth; they show: Retrograde Motion.

As measurement of planetary positions became more and more precise (Tycho), reconciling those measurements and retrograde motions with "planetary spheres" became a complex arrangement of spheres within spheres within spheres.

Modern Astronomy

Copernicus (1500) - Adopted (Aristarchus) Heliocentric model: The Sun, not the Earth, is at the center of the Universe. The model gain support because it was beautiful and elegant in its explanation of retrograde motion. The model was not totally correct, as it predicted that the planets will move in circular orbits around the Sun. The fine-tuning of the model, and the birth of Modern Astronomy, came with: Tycho, Kepler, Galileo, and Newton.

Galileo's observation that the apparent size of Venus changes for different phases provided strong evidence in support of the heliocentric system. If Venus orbited the Earth as Aristotle believed, it would always appear of the same size, just as the Moon does.