Ok. Recall that I said that the literal "evening and morning" of the first day is famously cited as impossible, since the sun was not yet created. But you are right that this was no barrier to the traditional literal interpretation. I cite Chapter I of History of the Warfare of Science with Theology in Christendom (1896) by Andrew Dickson White:
In the first of the biblical accounts light is created and the distinction between day and night thereby made on the first day, while the sun and moon are not created until the fourth day. ... the original text is a precious revelation to us of one of the most ancient of recorded beliefs the belief that light and darkness are entities independent of the heavenly bodies ...
And further,
Of this belief we find survivals among the early fathers, and especially in St. Ambrose. In his work on creation he tells us: "We must remember that the light of day is one thing and the light of the sun, moon, and stars another the sun by his rays appearing to add lustre to the daylight. For before sunrise the day dawns, but is not in full refulgence, for the sun adds still further to its splendour." This idea became one of the "treasures of sacred knowledge committed to the Church," and was faithfully received by the Middle Ages.
So, there we have the simple literal meaning, believed by Christians for centuries. Is your faith equal to this? Would you reject revealed truth on the strength of mere human notions of optics?
Another understanding is that the revelation occurs over 7 days.