Everything was dark until God brought forth light.
He created light, then light fixtures (stars), then the "lights of the world" (man).
When Christ tells us to be the "light of the world" we need to refer to light in Genesis.
Three things we see light used for:
1) Separation - day was separated from night.
You know it's day because it's light, because the sun is out.
When we show up then it will cause separation - some will hate us and others will love us, but nobody will ignore us.
2) Signs - light fixtures were used as signs pointing to God's order.
God wanted us to be "in the know" of His order, so He gave us signs that point to it.
We are to be signs pointing to God's order.
3) Government - The sun is in charge of the day and the moon and stars are in charge of the night. When they come out it will be either day or night.
The church is God's governor on the earth - just like a governor on a go-cart.
The go-cart can only go so fast because it's being restrained.
The church is God's boundary-maker.