The first day of creation illuminated a framework of existence with the words, “let there be light.” The big picture of God’s plan could then be seen. After God completed that first day, He then divided “the waters from the waters,” creating a firmament known as Heaven. Other translations of the Bible use the word “expanse.”
Regardless of how we interpret the physical separations created by God on the second day, the practical result is that He created a domain for humanity through this division. As people, we cannot see the entirety of existence or the domain of God. As we try to reconcile science and the Bible, the creation story reminds us that God’s capabilities are incomprehensible and often shielded from view. The light and the firmament established our domain while they also limited our viewpoint to a comprehensible universe.
6 And God said, Let there be a firmament in the midst of the waters, and let it divide the waters from the waters. 7 And God made the firmament, and divided the waters which were under the firmament from the waters which were above the firmament: and it was so. 8 And God called the firmament Heaven. And the evening and the morning were the second day.