For the cave man, the universe was simple: A disk extending to the visible horizon covered by a hemisphere where celestial bodies were hanging. It made sense.
The Babylonians were the first to think that planets were the odd balls as they didn't follow the general pattern of the stars and were ... moving in the sky. Hence their name as "planet" in Greek, means "wanderer."
The real problem was for Venus and Mercury. Those two planets, being between us and the sun, described not even an orbit but were apparently making loops in the sky, as observed on the starry background. It is no wonder that the ancients gave god-like power to those heavenly bodies; they had a mind of their own.
Today, it is quite paradoxal to think that while we know that we spin on ourself, around the sun and around the center of the Milky Way, relativity tell us that, wherever we observe the universe, it is as if we are at its center and that there is no absolute frame of reference.
For the amusement, it his said that a Pope of the Middle Age is known to have said: "Any fool can understand that the earth is not a sphere. If it was, then rain and snow would fall upward at the other end!"
... Yep, that's how we think, sometimes, in our own familiar way.
