I don't think you understand. The firmament is heaven. Genesis 1:8. Scripture doesn't say the firmament is in heaven, nor that it divides heaven and earth. Rather it is heaven. I didn't understand the rest of your post.
If "earth" and "water" are really two different words that describe one undifferentiated whole before Genesis 1:8, why bother using two different, normally non-synonymous words? I assume that there is a perfectly usable Hebrew word for "mud".
The fact that two different words are being used shows that your thesis is untenable. Even if the physical separation of water and earth is only accomplished in verse 8, the ontological separation of water and earth has already been accomplished from verse 2 - by the use of
two separate words which show that it is meaningful to speak of some action being performed on, or some status being attendant of, the waters, which do not apply to the earth.
In any case. Your thesis that "the firmament" is simply identifiable with "the heavens" fails on many counts. For one, you are being inconveniently fuzzy about what precisely these "heavens" will be (although to be fair you haven't really been asked). What are they? The atmosphere? The space of the solar system? The outer space? The rest of the physical universe outside Earth, whether observable or not? Or "spiritual space" - the dwelling place of God and the angels?
Secondly, the simple text of the passage itself shows that God's naming the firmament "Heaven" is not a simple identification. For starters:
In the beginning God created the heaven and the earth.
(Genesis 1:1 KJVR)
There is already a "heaven" in existence before the creation of the firmament in vv. 7-8, some kind of heaven which has properties not contingent upon the firmament, and in which the firmament is later set. vv. 7-8 clearly mean that the firmament
is set in heaven - the firmament
is heaven insofar as it is located in heaven. How can I know that? Because both qualifiers are used in tandem later on:
And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years:
(Genesis 1:14 KJVR)
And God said, Let the waters bring forth abundantly the moving creature that hath life, and fowl that may fly above the earth in the open firmament of heaven. (lit. "on the face of the firmament of heaven")(Genesis 1:20 KJVR)
(emphases added)
If "firmament" and "heaven" are so easily and singly equal as you say they are, why is the compound description necessary? Surely God could have simply said "Let there be luminaries in Heaven", and it would all be clear and you would be right. Instead it must be specified that the luminaries and later birds are associated with the firmament of the heaven, perhaps because either:
- there are other firmaments besides the one in heaven, so that they are not simply in the firmament, but the firmament of the heaven;
- or there are other locales in heaven besides the firmament, so that they are not simply in heaven, but the firmament of the heaven.
Whichever it is, the text itself disproves your reading of it clearly enough.
Thirdly, even if you were right and "firmament" can be simply identified with heaven, that would not displace the connotations of solidity that we find about the firmament. The firmament is able to divide waters from waters (Gen 1:6) and looks stunningly crystalline (Eze 1:22). The heavens, meanwhile, can be stretched forth (Isa 45:12, 51:13) - even as a curtain! (Isa 40:22) - they can shake, literally "quiver" (Isa 13:13), and they have pillars (Job 26:11) too. Add this on to the evidence of the etymology of "firmament",
raqiya from the act of metal casting, and the etymology of its consistent Septuagint translation
stereoma with its implications of solidity and substantiality.
Your arguments, unlike the firmament

, do not hold water.