Ancient Greek astronomers grappling with the various zigs, zags and tilts of heavenly motions spun off some novel explanations. Some of them even orbited near the truth. Like the Sumerians before him, Anaximenes noted in the sixth century B.C.E. that planets rambled solo across the stellar backdrop. But he also encased the stars in a rigid, eternal sphere that he said rotated around Earth, an idea that would outlast geocentrism and stick around until Edmund Halley observed the sovereign motion of the stars in 1718 [sources: Belen et al.; Brandt; Graham; Kanas].
As further observations strained the model, ancient astronomers kept adding shells. They stuck stars in shells, planets in shells -- they even snatched the sun and moon from their former free-floating home in the air and stuck them in shells. Some said the stars, sun and moon were just holes in some colossal cosmic colander that revealed the holy fire beyond. When blocked, these holes produced moon phases and eclipses [sources: Graham; Allen; Kanas].
This piling-on of spheres culminated in charmingly and ludicrously complex systems invented by Eudoxus in fourth-century B.C.E. , which entailed up to 27 nested and linked spheres, each spinning on its own axis and influencing the others [sources: Allen; Kanas]. Eudoxus would have invented more, but William of Occam traveled back in time and hacked him with a razor.