Let me tell you a tale about two sisters.

Long ago, there were two Alicorn sisters who ruled over the land, the older sister would raise and lower the Sun, while the younger would Raise and Lower the moon. Together, they ruled over Equestria, protecting the kingdom and bringing peace to all of it's inhabitants.

However, with time, the younger sister grew more and more Jealous about her older sister. While ponies basked in the glory of the Sun, enjoying it's warmth and doing activities during the day, ponies would sleep through the night.

That jealousy grew into arguments, which grew into hatred. They both distanced themselves from each-other, until the younger sister finally decided to rebel, she wanted to take over the Entire Kingdom for herself. The older sister didn't have any other choice, but to completely banish her younger sister to the Moon.

This is that story.