English: Schematic model likely representing the first 4, out of a total of 27, spheres of Eudoxus' cosmic model following Schiaparelli. Each sphere has its own rotational axis that, together, generates a complex motion for the planet, in this illustration, the moon. Its operation is similar to what we currently know as a gyroscope. Note: The axes are placed illustratively and do not correspond to a real geometric-mechanical formulation."