China has the earliest known records of supernova explosions (1400 bc) Greeks were the first people known to make models of nature. They tried to explain patterns in nature without resorting to myth or the supernatural. They tested (and limited) their models with observations. The greeks explained planetary motion with a geocentric model. Earth at the center of the universe. Heavens must be perfect - objects move on perfect spheres or in perfect circles. But this can"t explain retrograde motion- planets moving backwards. Easy for us to explain: this occurs when we lap another planet (or when mercury or. But it is very difficult to explain if you think that earth is the center of the universe. In fact, the greeks (aristarchus) considered the correct explanation, but most rejected it. Their inability to observe stellar parallax was a major factor.