The Lord calls the expanse heaven.
The word heaven
here does not have the meaning of the dwelling place of God. It refers to the sky and clouds as we see them above us. The Lord created the water and the sky. The waters above and on the earth are not divine. They are creations of God over which he rules.
The second day is the only one where we do not read, Then God saw that it was good.
The reason is clearly not that his work of creation on that day did not live up to his perfect plan. What applies to all of creation, according to Genesis 1:31, also applies to God’s work on the second day.
8 And God called the expanse Heaven. And there was evening and there was morning, the second day.