E

The forces which could make planets go in such paths are unimaginable; and this seems to have been a major feeling in Kepler’s mind when he adopted Copernicus’ view that the Sun must be the centre, and that planets must go in simple orbits around it. He showed that they go in an ellipse. Dynamical thinking lay behind this triumph of the new astronomy; though the nature of the forces was still unclear until Newton’s work on gravity later in the seventeenth century.