Light from the Sun and other stars is not the only way to illuminate the earth and produce day-night cycles. The light of Day 1 was probably a consequence of the instantaneous creation of matter. To understand why, some basics must first be explained.
Before plants, planets, and people could be created, fundamental forces had to be created, including the gravitational force and electrical force. For example, on earth, the gravitational force pulls all things—rocks, the chair you are sitting in, and your body—toward the center of the earth. Powerful electrical forces hold atoms—which comprise everything—together.
Gravity. The Bible seems to mention the beginning of gravitational forces. In describing earth’s earliest state, Genesis 1:2 says, “And the earth was formless and void, ... .” The second half of that verse then states, “... the Spirit of God was moving over the surface of the waters.” Could the earth be formless—basically a “glob”—but soon afterwards have a surface? Yes, if gravitational forces suddenly began acting to make a “formless” earth spherical.
Possibility 1. Just as earth’s particles, when created, were apparently at various distances from where they would finally rest after gravitational forces came into existence, atomic particles (electrons, protons, etc.) may not have been created in their final positions within atoms. The newly created electrical forces would have pulled electrons and protons—negatively and positively charged particles—toward each other to form atoms. Negatively charged electrons would have accelerated or “fallen,” by electrical attraction toward positively charged nuclei. In doing so, they would emit light.
Whenever electrical charges accelerate, electromagnetic radiation—which includes visible light—is given off. That is how an antenna works. Electrons surge up and down the antenna at a particular frequency, causing radio, television, or other electromagnetic waves to radiate out at that frequency. If “a universe” of newly created electrons accelerated (or “fell”) toward atomic nuclei, light would have radiated at all frequencies.
Possibility 2. Alternatively, if before the heavens were stretched out (explained on pages 416–428), matter in the very compact universe would have been gravitationally compressed and heated so much that atoms would have rapidly lost and gained electrons. Matter would have emitted light, just as in a light bulb or florescent lamp. Once the stretching began, that matter would have cooled and the light would have diminished.
With either Possibility 1 or 2, the newly created matter would have emitted light. Genesis 1:3 may describe this: “Then God said, ‘Let there be light’, and there was light.”
When light reflects enough times off surrounding matter—as it would in a much smaller universe—everything reaches a common temperature and the space between that matter becomes filled with blackbody radiation.1 If that space later expands, that radiation’s temperature will drop.