Sun shone down on Earth. The dirt cracked and sizzled, dry and molten. The red, flaming sky baked the world. Nothing grew except for the tiny drops of green things deep beneath the crust, which lived and died scuttling over each other in total darkness.
Sun felt lonely, so he reached out into the blackness of space around him and scooped up a piece of it, which he rolled into a ball and set near Earth. This blackness that was of himself and not of himself took on a shine from Sun's reflection over time, and, as is the way of things, awoke.
Sun and Moon spent many fine years together carousing through the heavens. Moon reflected Sun's joy back on him, and together they magnified their light to many times greater than what Sun could do on his own.
Moon, though, was lonely in her own way. Sun was so bright, and sometimes she yearned for a sliver of the darkness from which she came. She looked down at Earth and saw that, without her noticing, the path of her shadow when she came between Sun and Earth left a smudgy darkened stain on the scorched ground.
These darkened patches reminded Moon of her many eons of life in black, deep space, when she was free to sprint through the sky at her leisure. She adjusted her movement around Earth in order to block the light of Sun from reaching Earth's surface more often. As the frequency of shadows lengthened, more darkness appeared on the surface.
The darker dirt spread and grew, and the difference in temperature over Earth's surface created wind. With wind came clouds of dust, which collected in Moon's shadow and, in some places, dropped the surface heat enough that the beginnings of water droplets cooled and condensed in the air and on the surface.
Over time, these tiny flecks of water collected into the dust clouds and then rained, spreading the darker, richer soil across the Earth. The green drops in the deep blackness wiggled and squirmed their way to the surface, slowly growing into plants and animals. Some of the plants grew larger and larger and became trees, which protected the ground from Sun even when Moon was not present. In the dark shade of the trees, the life on Earth grew up and learned to live in the light of both the Sun and the Moon.
Sun, though, felt jealous. Earth was his creation, after all, and Moon had gone and changed it without asking. No longer did it perfectly reflect his glory--in many forests and jungles, in the deepest oceans and lakes, his light could barely penetrate. He didn't even get a chance to completely soak it in his light, what with Moon constantly flitting around, tending to places that needed darkness to thrive.
Sun, though a bit jealous by nature, nevertheless had learned a few things over the years. He thought there might be some equitable solution to both his and Moon's desires. He thought and thought, as Earth grew lusher still and thick canopies of leafy green covered most of the land mass. When he finally brought up his solution to Moon, she was delighted.
Sun and Moon both shifted their positions slightly. Sun now shone his brilliant light, unfiltered, on Earth every so often. So much light changed the surface of Earth in some places, and some places without a strong green forest withered and died and became harsh, cracked deserts again--though never as lifeless as they had been before. Other places found themselves out of balance in a different way, and without the same mixture of Sun and Moon they became cold and frozen. Still, the majority of Earth continued on as before, lush and rioting with sound and color. And overall, the variety of new places on Earth pleased Moon, who liked variety.
Too, Moon thought she received the better end of the deal. While Sun did now get an opportunity to blast Earth with his full and unalloyed brilliance, when this happened Moon was completely in Earth's shadow. For the first time since her creation, Moon could spend a few glorious, blissful minutes completely in the dark, reveling in the children of Earth without sharing with Sun. As a result of this change, Moon also received the occasional chance to come fully between the Sun and Earth, interposing herself and bathing in Sun's untinted joy. At these times, Moon let her love of Earth fade away and grew the bond between her and Sun, reminiscing with him about the times when their bond was the only such tie between them.