Some assume the creation story described in the opening chapter of the Bible is a literal description how the universe unfolded. Efforts have been made to try to fit the order of the seven days of creation into our scientific world view. But trying to explain the order of creation as described in Genesis 1 stands at odds with modern understanding.
There are problems that are difficult to reconcile in a literal interpretation of the creation story. For example, day and night occur before the sun is created on the 4th day. The waters are created before the earth. The earth is created on the 3rd day before the stars or sun. Plants are created on the 3rd day before the Sun is on the 4th.
Literalist defenders are left trying to explain various difficulties such as how plants could survive without the sun.
There are other ways to explain the ordering of the events of the creation story. Genesis was written in the pre-scientific era. The Hebrews and their neighbors used literary parallels in their writings. A look at parallels in the opening chapter of the Pentateuch can shed some light (pun intended) as to why the events were ordered as they were.
Akkadian and Ugaritic literature indicate seven consecutive periods were considered a perfect period of time to do an important work, with action lasting six days, reaching its conclusion/outcome on the 7th. In their traditions, 6 days of labor were divided into three pairs, 1&2, 3&4, 5&6 with completion occurring in the 7th period. [UC 13]
The Hebrews did this a bit differently in Genesis 1 with 1&4, 2&5, 3&6 periods being related with completion on the 7th day. Creations are also grouped into static relationships (days 1-3) and animated relationships (days 4-6).
|Stationary Creation||Animated, Moving Creations|
|1; Light||4; Luminaries (sun , moon & stars)|
|2; Sea and Heaven||5; Fish and Fowl|
|3; Earth (with its plants)||6; Land Creatures and Man|
Note the conceptual relationship in the symmetric pairs (rows). The 1st column lists the static phenomena or place, while it’s parallel (2nd column) occupies and moves through the 1st. During the first three days, the stationary aspects of creation are made. During the 2nd three days, the creations occupy and move through the corresponding medium created earlier. [UC 17, 42]
There is no need to try to reconcile the order of the six periods of creation with a scientific understanding of creation of the universe. This literary parallel seems to provide a simpler explanation.
 Regarding light, the Hebrews did not understand that light moved as we do today. Light appeared to statically fill the air – and therefore fits in as a stationary creation. The sun, moon and stars, however, had movement and fit in the “animated” group.
UC: Cassuto, Umberto. A Commentary on the Book of Genesis. Jerusalem: Magnes, Hebrew University, 1961. Print.