Long ago, Sun and Moon were the greatest lovers of all time. Sun, being a priceless beauty and Moon an elegant gentleman. Not even God tried to separate them, and they were never meant to be together. Sun was meant to come out for day, and Moon at night.
Chaos occurred while they were together in the sky. God dealt with this for so long, he dealt with it until the destruction of Earth the first time, for he did not want to tear their love apart. One terrible day, Sun and Moon spent too much time together, causing the death of dinosaurs. I told you, they caused chaos each time they were together.
God had had enough. He couldn't go on with re-creating the world only to have Sun and Moon destroy it again. He separated them the best he could. He made it to where Sun could only come out during the day, and Moon at night, as was meant to be. Obviously Sun and Moon were both miserable, but they knew it was for humanity. Occasionally, Moon will stay in the sky all day and watch his lover from a distance. If you ever see the Moon out during the day, know that you're watching another love story in the making. And it's the greatest love story of all time.