Your question is not as simple as it seems, because some interpreters have read into the word “firmament” primitive ideas that reflect the mythologies of other ancient cultures. Yet Genesis 1 uses simple and majestic language to depict the birth of a planet as it comes into existence from the hands of the Creator. Although told in a way that any human can understand, Genesis 1 allows for further comprehension through scientific investigation without being irrelevant or primitive.

With respect to your specific question, “firmament” (rāqîac) has been taken by some to refer to the primitive ancient Near Eastern concept of a gigantic, metallic, heavenly dome placed by God or the gods over the earth. If this understanding is correct, then Genesis 1 is culturally conditioned and becomes useless in understanding how God brought the world into existence.

Let’s take a quick look at Genesis 1, paying particular attention to your question.

1. Genesis 1 Is Unique: When compared to ancient Near Eastern Creation accounts, the biblical narrative is certainly unique. The absence of polytheism and of any reference to God’s struggle with the forces of chaos set the Genesis creation account totally apart from its contemporary and competing Creation stories. There is absolutely nothing in the ancient Near Eastern narratives about a six-day creation followed by a seventh day of rest. Yes, there are some similarities, but when they are placed within the totality of their respective stories they are not significant.

In fact, the similarities may well be, at least in some cases, remnants of truth preserved in the pagan narratives. The biblical story is unparalleled and seems to be a polemic against other Creation ideas prevalent in the ancient world.

2. Use of the Word “Firmament”: As far as I know, the Hebrew term rāqîac (firmament) is not found in any other ancient language, and its Hebrew meaning is not completely clear. The verbal form means “stamp down, spread out, hammer out,” suggesting that the noun “firmament” designates the vault of heaven as a solid dome. But the noun does not necessarily designate the concrete result of the hammering out. The basic idea of the verb is of extending something, and the noun could then express the idea of expansion or, here in Genesis 1, the “expanse.” Since Genesis 1 does not describe the nature of the “firmament” created during the second day, scholars tend to explain it in terms common to ancient ideas of a solid vault.

Genesis 1 says several important things about the “firmament.” First, its function was to separate the waters below from those above. The fact that it separates the waters could suggest that there is an element of concreteness to it, but nothing is said specifically. This silence makes it possible for us to use the modern word “atmosphere” to designate it.

Second, the suggestion that the reference is to the atmosphere is reinforced by the fact that the “firmament” is the space where birds fly: “Let birds fly above the earth across the expanse of the sky” (verse 20, NIV). Third, the “firmament,” or expanse, is specifically called “heavens,” or more precisely, “sky” (NIV), in verse 8. The emphasis is not on concreteness but rather on the space separating the waters, making room for birds to fly.

Finally the text says that the sun and the moon were in the firmament/expanse of the heavens to function as lights. The word “firmament” does not distinguish between the sky and the stellar heavens, but neither does it deny that distinction. The description in the text is from the perspective of a person who looks up and sees the moon and the sun in the sky.

The mystery of Creation by a loving God will never be completely understood by His creatures. Still, Genesis provides the only trustworthy account of that glorious event; and even there we find only a brief but reliable summary of His creative action. Modern science cannot prove or disprove what Genesis says, but it can expand our understanding of our God’s power.