What does Genesis 1:8 mean?

The description of creation given in Genesis follows a poetic but very firm pattern. For each of the first three days of creation, God modifies the world in preparation for some new thing. Then, in each of the corresponding second three days, He creates that new thing and places it in the world. In each case, God observes His work and declares it "good," and the day is given a number.

The previous two verses detail the creation of an expanse between the waters of the sea and some upper layer of waters. Now, in verse 8, God names that space. In Hebrew, the name He gives to it is sā'mā'yim. Bible scholars translate this term as "sky," or "heaven," or "air." In Hebrew, the word can be applied to any of these, based on context. It's not likely that the word means heaven in the sense that we normally think of it in our day. This heaven is very likely "the heavens," or the atmosphere: the "empty" space above the sea.

The primary message is that, on creative day two, God formed an open space and named it. As with other aspects of creation, this counters any claim that the air, wind, or skies are themselves divine. Even the sky and atmosphere around us are an intentional part of God's creation of the earth.