This is Kepler’s famous pretzel diagram, where he focused attention on the planet rather than the rotating solid sphere which carried the planet. In an Earth-centered system, the planet must follow some kind of similar pretzel path as it is carried along within a thick solid sphere. By analyzing Tycho’s observations of Mars, Kepler put forward what are now regarded as his first two laws. Just as fundamentally, he changed the paradigm from focusing on orbs, or solid spheres, to orbits, the actual path a planet takes as it moves through space.