Uniformly Spherical Countries in frictionless vacuum

Like most people here who read science fiction growing up, I was raised on the idea of the world-nation.

By the time I was in my twenties, I knew that wouldn’t work. Acculturating more than once (back and forth, really, after my year as an exchange student) had made it clear that countries don’t actually want to merge, no matter what idealists and crazy people want.

And yet, somehow, I managed to believe the “open borders” part of libertarianism well into my thirties. I really have no...