EXPANSION
(Heb. «rãqîa»).
The Hebrew term means an inconsistent extension (Gen. 1:6), and corresponds well with the term space (cp. the term “open expanse of the heavens” in Gen. 1:20, KJV).
The translation “firmament,” which appears in many versions, is an unfortunate slip of the pen by Jerome in the Vulgate version.
Aristotle and the classics imagined that the sky was a solid sphere. However, this is not the concept we find in the Bible, except in figurative poetic language (cf. Jb. 26:11; 2 Sam. 22:8, and contrast instead with Jb. 26:7).