"Well, almost. A lot of planets aren't habitable. Not enough atmosphere, no water. Terraforming... fixes it. Change the atmosphere to something humans can survive in, lets us get set up on a planet." Some places it took better than others. The Inner colonies had more complete terraforming than a lot of the outer colonies, but it was the same way wth most things.

"The gas planets have cores of rock and ice and liquid metal. They have enough of a gravitational pull to hold the gas around them." He thinks that's how it works. It's been a long time since high school science.