Firmament

Firmament is the vault or expanse of the sky. The word is first recorded in the 13th century and is anglicized from Latin firmamentum. According to Genesis, God created firmament ex nihilo and used it to make Heaven. It is a contentious topic because firmament is the central feature of a scriptural cosmology which is now considered primitive.

Augustine wrote that too much learning had been expended on the nature of the firmament. "We may understand this name as given to indicate not it is motionless but that it is solid." he wrote. Saint Basil argued for a fluid firmament. According to St. Thomas Aquinas, the firmament had a "solid nature" and stood above a "region of fire, wherein all vapor must be consumed.

The notion of the sky as a solid object (rather than just an atmospheric expanse) was widespread among both ancient civilisations and primitive cultures, including ancient Greece, Egypt, China, India, native Americans, Australian aborigines, and also early Christians. It is probably a universal human trait to perceive the sky as a solid dome.