What does Genesis 1:16 mean?

Verses 14-19 describe the fourth day of the creation week, during which God created the sun, moon, and stars. Following the usual pattern, prior verses related God's words, followed in this verse by a description of that command becoming reality.

The sun and moon are pictured as two great lights, one each to govern—or "rule"—the day and the night. At the time Genesis was written, many cultures worshipped the sun, moon, and stars as if they themselves were gods. The claim of the Bible is that these "lights" are not deities, merely created things made by the one, true God. It's an idea that still stands in opposition to many cultural norms. This would have been especially meaningful to the people of Moses' day, when nations such as Egypt were dominated by belief in gods of the sun, moon, stars, and skies.

This verse ends with another profound understatement: God made the stars. Given what we know of the immense universe surrounding us, this is an incredible display of power. The idea that God created the whole expanse of our universe in a day, with a word, should astound and humble us. Not only does our view of the heavens help us track time (Genesis 1:14), it is also intended by God to provoked us to worship Him, through the immensity and beauty of what He has made (Psalm 19:1).