Copernicus's Heliocentrism

In aristotilian physics, heavy things that are dominated by earth and water move towards the centre of the cosmos. This nicely explains why rocks fall straight down and flames flicker upwards. How can copernicus offer a superior explanation? For that will need to wait for seventeenth century physics. He does his best though, proposing that god implants a natural desire in each element to move towards the place where the whole of that element gathers. As copernicus notes, the result will be that a falling rock actually moves in a far more complex way than we would suppose.