Except God hadn’t created the sky until the second day, the earth on the third day, and the sun and moon until the fourth day. So the light wasn’t from the Sun, and could not mean a full rotation of the earth as neither had been created yet.
I have read where the term “day” might be better translated as “period of time” or “era”.
These primitive people that had not witnessed Creation, but it had been revealed to them, on their own terms, described it in their own terms the best they could.
As with so many things in the Bible that can be considered a mystery (the Resurrection is perhaps the most important mystery to me), I take them on faith, even if I don’t completely understand them.
On the first day, I have wondered if the “let there be light” was more like “let there be energy” (what we now theorize is something like the “Big Bang”). And that energy is distinct from the empty dark expanse of nothingness previously.
I have seen electrical engineering T-shirts that were printed with
And God said
[put the 4 Maxwell’s equations here, which refer to all electromagnetic phenomena, not just visible light]
And there was light.
And don’t forget spiritual light, a very frequent topic in scripture. Was it the physical alone that came into being at the creation event? Very doubtful, given the sheer importance of spiritual light.
This matches how I interpret it and how I teach it. But I wasn't there so I could be wrong.