The answer is: Heaven

Gen 1:8 - The NIV calls the firmament 'sky'.

In Genesis 1:8, when God divides the waters and calls the firmament "Heaven" or "Sky," we glimpse the immense creativity within the Creation story. The term "firmament" gives an intriguing picture of the ancient view of the universe, as it implies a solid layer that separates the waters above from the waters below. Picture it like a vast canopy or dome over the Earth—that perspective was quite common in ancient Near Eastern cultures!

Fun fact: Ancient civilizations often attached spiritual significance to the sky. While today's understanding of the atmosphere relies on science, back then, the sky was viewed as the realm of divinity. The consistent use of "Heaven" also indicates a realm where the divine action takes place; God creating these boundaries isn't just about foundry, it's involved and active.

Now, what's particularly fascinating is the echo this concept has later in biblical texts. For example, in Psalm 19:1, we finds poetic descriptions of how the heavens declare God's glory. It suggests a dynamic link between creation and the ongoing story of a universe full of wonder and purpose.

So, when you read about God calling the firmament Heaven in Genesis, try to see it as a powerful establishment of order. It serves not only to showcase the remarkable intricacies of the world we inhabit but also portrays the universe as a harmonious expression of meaning, carrying divine resonance throughout the ages!