You gave an explanation? Where? What was it? Can you please be specific (not vague) about it? Spell it out, please.
"expanse" is an incorrect translation of Heb. "Rakia" which the LXX renders "firmament" (as in KJV and LV) which is a solid dome, ceiling, or tent. It is translated "expanse" (and affirmed in many commentaries) only to accommodate modern science and modern cosmology. These two commentaries are more accurate IMO (taken from Bible Hub):
Ellicott's Commentary for English Readers:
(6) A firmament.—This is the Latin translation of the Greek word used by the translators of the Septuagint Version. Undoubtedly it means something solid; and such was the idea of the Greeks, and probably also of the Hebrews. As such it appears in the poetry of the Bible, where it is described as a mighty vault of molten glass (
Job 37:18), upheld by the mountains as pillars (
Job 26:11;
2Samuel 22:8), and having doors and lattices through which the Deity pours forth abundance (
Genesis 7:11;
Psalm 78:23). Even in this “Hymn of Creation” we have poetry, but not expressed in vivid metaphors, but in sober and thoughtful language. Here, therefore, the word rendered “firmament” means an expanse. If, as geologists tell us, the earth at this stage was an incandescent mass, this expanse would be the ring of equilibrium, where the heat supplied from below was exactly equal to that given off by radiation into the cold ether above. And gradually this would sink lower and lower, until finally it reached the surface of the earth; and at this point the work of the second day would be complete.
Ellicott clearly states that rakia is solid, but concedes to modern geological theory.
Cambridge Bible for Schools and Colleges:
6–8. The Firmament of the Heaven
6. Let there be … waters] The work of the “second day” is the creation of the so-called “firmament” of heaven. The Hebrews had no conception of an infinite ethereal space. The vault of heaven was to them a solid arched, or vaulted, structure, resting upon the pillars of the earth (
Job 26:11). On the top of this dome were the reservoirs of “the waters above the heaven,” which supplied the rain and the dew. Beneath the earth were other reservoirs of waters, which were the sources of the seas, lakes, rivers and springs. After the creation of light the next creative act was, according to the Hebrew cosmogony, the division of the primaeval watery abyss, by means of a solid partition which is here denoted by the word rendered “firmament.” The waters are above it and below it.
a firmament] This word reproduces the Lat. firmamentum; LXX στερέωμα. The Hebrew râqîa denotes (see Heb. Lex.) “extended surface, (solid) expanse” (as if beaten out; cf.
Job 37:18). For the verb raq‘a=beat, or spread, out, cf.
Exodus 39:3,
Numbers 17:4,
Jeremiah 10:4,
Ezekiel 1:22, “and over the head of the living creatures there was the likeness of a firmament … stretched forth over their heads above.” Compare
Job 37:18, “canst thou with him spread out (tarqi‘a) the sky which is strong as a molten mirror?” See
Psalm 19:1;
Psalm 150:1,
Daniel 12:3, where “firmament” = sky.
From Dr Hastings’ Dictionary of the Bible, by kind permission of Messrs T. & T. Clark:
For the solidity of the heaven according to this conception, cf.
Amos 9:6, “it is he that buildeth his chambers in the heaven, and hath founded his vault upon the earth.” The fall of rain was regarded as the act of God in opening the sluices of heaven, cf.
Genesis 7:11,
2 Kings 7:2;
2 Kings 7:19,
Psalm 78:23;
Psalm 148:4, “ye waters that be above the heavens.”
This Cambridge commentary is more accurate IMO.
So then, to answer your question: Gen. 1:7 says that God placed the sun, moon, and stars IN THE FIRMAMENT, which means they truly believed what their naked eyes saw, and concluded that they existed in the dome above the Earth. "Heavens" means the dome above the Earth, since the firmament is called "heaven."
Again, God accommodates to man such things, as He doesn't think it important to correct men about science, technology, and other things that are understood my natural observation and reasoning. God in the Bible is concerned with morality, idolatry, how people treat each other, and other moral and ethical matters. IOW, theology.