the Empyrean, defined by Claudius Ptolemy as the highest heaven or celestial realm, which translates literally as “the place in fire” (Em-Pyr).
Philolaus says:
"There is fire in the middle at the center and again more fire at the highest point and surrounding everything. By nature the middle is first, and around it dance ten divine bodies — the Sky, the Planets, then the Sun, next the Moon, next the Earth, next the counter-earth, and after all of them the fire of the hearth which holds position at the center."
— Stobaeus - 1:22
It is around this point that all heavenly bodies were said to rotate. Wrongly translated as Dios Phylakê (Διός φυλακή) or "Prison of Zeus", a sort of hell, the Central Fire was more appropriately called the "Watch-tower of Zeus" (Διός πυργός) or the "Hearth-altar of the universe" (ἑστία τοῦ παντός).
Empyrean derives from the Ancient Greek word Empyres ἐμπύριος (Empúrios or Empyrus), from ἐν (en, “in”) + πῦρ (Pûr, “fire”) or fiery in Latin called Empȳreus, from (whence we get the English word Pyre. The highest heaven or heavenly sphere in ancient and medieval cosmology usually consisting of fire or light.
