“Even modest improvements in the social, economic, and political problems that our global civilization now faces could release enormous resources, both material and human, for other goals. There’s plenty of housework to be done here on Earth, and our commitment to it must be steadfast. But we’re the kind of species that needs a frontier - for fundamental biological reasons. Every time humanity stretches itself and turns a new corner, it receives a jolt of productive vitality that can carry it for centuries. There’s a new world next door. And we know how to get there.”