That's an excellent set of analogies. As harsh as a sea voyage is on one's health, you don't risk breaking a hip when you step on a different continent. And you

That's an excellent set of analogies. As harsh as a sea voyage is on one's health, you don't risk breaking a hip when you step on a different continent. And you didn't have to bring your food, air, water, and airtight shelter with you. The case for manned exploration is hard enough to sell. Mankind will learn a lot about space travel and space habitats, and pay a lot for that knowledge. But the outcome may be that we are not able to prosper off Earth. We have been seduced by science fiction, but living it might not be what anyone can do for long.