Sounds like a fascinating question, but I’m not fully understanding it.
At times the word translated “firmament” in the KJV and other translations seems to be speaking of the expanse of the sky, the region under the “canopy” or “dome” at the edge of the atmosphere. At other times, it seems to be speaking merely of the vast region “up there” above us.
The ESV Study Bible explains:
“... it is difficult to find a single English word that accurately conveys the precise sense of the Hebrew term shamayim, “heaven/heavens.” In this context, it refers to what humans see above them, i.e., the regions that contains both celestial lights (vv. 14-17) and birds (v. 20).”
I did find the discussion of this concept at Wikipedia to be pretty fascinating: http://en.wikipedia.org/wiki/Firmament
Maybe in the end, we should just think of “firmament” broadly as “space,” distinct from “stuff.”
Apparently even Sir Isaac Newton struggled with this possible poor translation. I prefer where Dr. Walt Brown PhD felt this lead ~ from my links page re:creationscience.com...
Genesis 1: 8a — Two Interpretations
Why then, does Genesis 1:8a state, “And God called the expanse heaven”? Here are two interpretations:
a. “The expanse” meant the atmosphere or outer space.
b. “The expanse” meant “heaven”—where God dwelt—the original paradise. Recall that God “walked” and “talked” with Adam (Genesis 3:8–9), so heaven was originally on the earth—or the earth’s crust.
If “heaven” meant atmosphere or outer space, then the Septuagint and Vulgate translators incorrectly associated solidness with it. Notice also that the similarities of raqia ((ayqirf) with baqia ((ayqib@f) and raqa ((qarf) support the second interpretation. [See page 447.] If raqia (expanse or firmament) always means atmosphere or outer space, five questions, or apparent textual contradictions, arise.
Question 1: Why was the word raqia followed by the phrase “of the heavens” in Genesis 1:14, 15, 17, and 20? That would be redundant.
Question 2: If raqia implies a canopy, why wasn’t one of the three Hebrew words that clearly means “canopy” used?
Question 3: Genesis 1:1 says that the heavens were created on the first day.19 However, if raqia always means “heaven” (atmosphere or outer space), then Genesis 1:8a says heaven was created on the second day. Also, Genesis 1:8a defines heaven after the word “heavens” was first used in Genesis 1:1. Normally a word’s meaning is understood from the context of its first usage.
Question 4: Genesis 1:9 states, “Let the waters below the heavens be gathered into one place, and let the dry land appear.” Obviously, these are earth’s surface waters. If “heaven” meant atmosphere or outer space and if “expanse” meant a canopy surrounding the earth, why would Genesis 1:9 not read, “Let the waters below be gathered into one place”? That would have been sufficient, clear, and consistent with the phrasing of Genesis 1:7, which relates the water’s two locations to the expanse. It would also make clear that the expanse (raqia) is above—not below—the surface waters. Instead, the text reads, “Let the waters below the heavens be gathered into one place.” The words “the heavens” apparently were added to make clear that surface waters were gathered into one place.
Question 5: Genesis 1:14 says the Sun, Moon, and stars (which fill the universe) were placed in the raqia of the heavens, and Genesis 1:7 says liquid water was placed above the raqia (as opposed to the raqia of the heavens). Does this mean that the raqia is the universe, and liquid water surrounded the universe?20
After struggling to understand Genesis 1:8a for 30 years, I described several possible interpretations of Genesis 1:8a in the 7th edition (2001) of this book. In 2005, I received independent letters from two pastors proposing an explanation.21 Before Adam’s fall, the earth was a paradise; in a sense, it was “heaven on earth.” Therefore, God called the firmament (earth’s crust) heaven. (Notice: God did not call heaven “the firmament.”) Each pastor provided different biblical reasons for his view, but both maintain that our difficulty in understanding Genesis 1:8a results largely from our inability to imagine the original paradise. If man had not fallen, no one would have difficulty with the fact that God called the earth, “heaven.”