Answer: the Bible is not a science journal.
But think about it. A day is the period of time that it takes for the earth to rotate on its axis with respect to the sun. Furthermore, the earth depends on the sun’s gravitational field in order to remain in its orbit (obviously) and not go drifting off aimlessly in space. But the sun did not show up until day 4…
So, regarding the first three days before God created the sun, what kind of “day” are we talking about here?
According to St Augustine, you can’t interpret the first chapter of Genesis literally (Duh!). In other words, the meaning of the term “day” can’t mean what we ordinarily take it to mean when we use this term. Augustine interprets the term “day” as it is used in the Genesis account as referring to angelic time — not earth time.
On the first day, when God said let there be light, God “brought to light” his first creatures, the angels:
And God said, “Let there be light,” and there was light. God saw that the light was good, and he separated the light from the darkness. God called the light “day,” and the darkness he called “night.” And there was evening, and there was morning—the first day. (Gen 1:3-5)
Upon their creation, the angels were good. Then something happened — exactly what, it’s hard to say, because we’re not angels — and some of the angels fell and were separated from God’s presence. That is how Augustine interprets the verse, “he separated the light from the darkness”. The separation of “morning angels” and “evening angels” marked the end of the first “day” in creation history.
What made these morning angels cling to God while the evening angels chose to be separated from him for all eternity? That’s a matter for further speculation — maybe tomorrow. Until then…
Have a nice “Day!”