The final session was held by Louis Giglio. He preached about the bigness of God.
God has created a vast universe. If it exists only for humanity then it's much too large for its function. Perhaps it was created to show the glory of God (Isaiah 40). If God could create this universe by divine command, and the universe is as large as it is, surely God is even bigger. How remarkable it is, then, that God would know us personally, become flesh, and be crucified for us.
Space photography is beautiful. Louis showed lots of it during his sermon. Each one was a picture of something vast or of something a great distance away. They all supported the notion that the universe is massive. And for the audience we get a chance to be awed by this. We feel small and fragile.
At this point Louis makes the leap from natural religion to revealed religion. Whether you know it by this name or not you've probably seen it before. The basic structure is to start with an argument from nature (see how beautiful/complex/awesome this thing is) in order to persuade people that there is something more than the physical universe. The next step is to move away from nature and to a revelation (a book, a vision, an experience) to describe characteristics of that "something more."
The problem is that the "something more" could be Zeus, the Flying Spaghetti Monster, a juvenile deity who created us as a forgotten plaything, or whatever. The movement from "something else" to "the God and father of our lord Jesus Christ" is a movement of faith. It's not a logical consequence. Giglio's last image (after all the astronomy1) was a depiction of the crucified Christ.
Even though it's a logical fallacy, it's actually quite a successful technique for converting people to a particular faith. But as they say, you should aim to win the person and not the argument.
1. The inclusion of an image of the X-structure at the core of the whirlpool galaxy was a crowd-pleaser but it reminded me of people who claim to see the face of Jesus in grilled cheese on toast.