Beware of making unwarranted assumptions; support your assertions with Scripture.
I. The key to understanding the Creation Account of the Book of Genesis is the realization that the account is a catalogue of activity, rather than a chronological record. The days of the Creation Account of Genesis are not literal days of twenty and four hours; some are stages which take place in chronological sequence, others are functional categories. Moreover, the Account focuses upon the earth, and events are described from an earth-bound perspective.
Finally, it must be kept in mind that the account of Genesis has to do with the Physical or Natural Realm, which is to say, the Realm of Nature. The Lord God exists in the Realm of the Spirit; man exists entirely in the Realm of the Natural; consider John 3:6.
II. The vision or eyesight of man, being a phenomenon of the Natural Realm, is dependent upon light. As a general rule, apart from sight, man is unable to work. Consider John 9:4: "I must work the works of him that sent me, while it is day: the night cometh, when no man can work." Accordingly, in the process of creation, the first order of business is the provision of light.
However, the expression "let there be light" does not mean that light was created when God uttered the phrase. After all, light is inherent to the nuclear process by which a star operates, and the universe is comprised of myriads of galaxies which, in turn, are comprised of myriads of stars, each of which generates vast quantities of light. Thus, light is fundamental to the Natural Realm. What is happening on the fourth day is that the Lord is causing light to reach the surface of the earth.
III. The existence of the "waters" in the second verse indicates that, at the time the Creation Account commences, the surface temperature of the earth has fallen well below the boiling point of water, so that water is able to exist in a liquid state. This, in turn, indicates that the Natural Realm is at an advanced stage of development.
The solar system, consisting of the Sun and the planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto) has been in place for some time, and the sun is providing light to the planets. But when the Creation account opens, the light of the sun is not penetrating to the surface of the earth, because the earth, spherical and encased in a layer of water, is shrouded by a dense layer of cloud.
IV. Like the Creation Account as a whole, the fourth day of the Account is a catalogue of activity, and not a chronological record. The time frame of the activity of the fourth day extends back to the creation of the universe, seen in the first verse.
In his much earlier creation of the sun, the moon, and the stars, the Lord God determined the positions these entities, so as to serve his purpose with respect to the earth.
V. Though the Protestant commonly interprets the linguistic structure, "God said ... and it was so," as implying instantaneous creation, such an interpretation is an insult to the Lord God.
While the Lord God has no need of sketchpad, draughting board, sliderule, calculator, computer, and tables of physical and chemical properties, the Lord nonetheless engages in sophisticated design and meticulous engineering of the highest order, paying exquisite attention to detail. The Lord God is a designer and engineer, not a faiery godmother whose magic wand mystically resolves a myriad of details.
Moreover, the six days of the Creation Account testify to the fact that the Lord used Natural Process* to implement his designs; the process of transforming the earth from the state "without form and empty" into a beautiful habitation for man and animals, was conducted in stages, likely over a span of millions of years. There is no reason to assume that the Lord God, who is everlasting, Psalm 90:2, and to whom the span of a thousand years is but a watch in the night, Psalm 90:4, accomplished the transformation in the span of one hundred forty and four hours.
* Natural Process is simply the set of rules, designed and implemented by the Lord God, which set governs operation of the physical and chemical processes of the Natural Realm. For example, water neither freezes instantaneously nor boils instantaneously, nor does ice melt instantaneously; each process requires the transfer of heat, and the rate of transfer depends upon temperature differential. Chemical reactions do not occur instantaneously; the rate at which a given reaction proceeds depends upon many factors, including pressure and temperature. A material body cannot be accelerated instantaneously; the rate of acceleration is proportional to the mass of the body and the force applied. In the performance of a miracle, the Lord is able to bypass Natural Process, but in many instances, such as the parting of the Red Sea, the Lord simply uses Natural Process.