And God set them in the expanse of the heavens to give light on the earth,I could have placed this verse with one of the others, but I wanted to keep it by itself because of the phrasing of the first part of the verse. Notice that in the previous verse God created these lights, now it is telling us that he is placing them in the heavens. That is what those words mean. The New American Standard translates it as, "And God placed them..." We should tarry on that thought for a moment.
In the next little phrase we get to see the partial purpose of the stars and the other planets, of the moon and the sun. Their purpose is tied to this one little planet. Even though this planet isn't the physical center of our solar system or our galaxy... It is at the center of the universe. God's plan is being worked out here. All of those other objects up in the expanse of the heavens are just light fixtures.