What Was the Light On Day 1 Of Creation And How Come There Was Night When The Sun Was Created On Day 4?
Then God said, "Let there be light"; and there was light.
And God saw the light, that it was good; and God divided the light from the darkness.
God called the light Day, and the darkness He called Night. So the evening and the morning were the first day. (Gen 1:3-5)
Then God said, "Let there be lights in the firmament of the heavens to divide the day from the night; and let them be for signs and seasons, and for days and years; and let them be for lights in the firmament of the heavens to give light on the earth"; and it was so.
Then God made two great lights: the greater light to rule the day, and the lesser light to rule the night. He made the stars also. God set them in the firmament of the heavens to give light on the earth, and to rule over the day and over the night, and to divide the light from the darkness. And God saw that it was good. So the evening and the morning were the fourth day. (Gen 1:14-19)
On Day 1, pure physical light was created. The earth was covered with waters and deep darkness. The only movement was the movement of the Spirit over the face of the waters.
When God created light on Day 1, darkness was still there. Light was divided from the darkness in the sense that where light shines, darkness cannot be - light travels, darkness can't. Light is energy. The creation of Light signified the beginning of the Time-Clock. The time run down begins here. This is when the clocks begin to first tick. This is when the ancient symbols of time run - night and day - take charge. It doesn't mean that day is day because of the sun and night is night because of the moon. It signifies the beginning of physical time in the universe with the first act of God.
Of course, there are many opinions and suggestions given regarding the identity of this light. For examples, Dr. Rabbi Zev Farber documents a few rabbinic views such as the buried light view (that the original light got buried and withheld from sinful men), the unfixed lights view (that the lights on day 1 and 4 are identical but not fixed yet on day 1), and the placed in the sun view (that the light was placed in the sun to limit its radiance and heat on day 4). But, these are mere opinions and conjectures.
The fact stated is clearly that God said, "Let there be light"; and there was light. It doesn't say "lights", but "light" signifying the creation of the generic light.