When it comes to describing the Earth orbiting the Sun before Copernicus, the ancient Greek astronomer Aristarchus of Samos proposed a heliocentric model in the 3rd century BCE, suggesting that the Earth revolves around the Sun. However, this idea was not widely accepted at the time and was overshadowed by the geocentric model championed by Ptolemy. It was not until the 16th century when Nicolaus Copernicus developed his heliocentric model, which gained significant attention and eventually became widely accepted.
In the realm of astronomy, many notable astronomers have made significant contributions throughout history. Some examples include Claudius Ptolemy, Nicolaus Copernicus, Galileo Galilei, Johannes Kepler, Isaac Newton, and Edwin Hubble, among others. Determining the "greatest" astronomer is subjective and can vary depending on various factors such as their discoveries, impact on the field, and influence on subsequent generations of astronomers.