Matt Yglesias has a nice post about population density, basically arguing that you don’t need to have high-rise metropolises to have remarkably high density compared with the US average.

I’d quarrel a bit, however, with his characterization of New Jersey as the “quintessential suburban state.” He’s right in the sense that the two principal cities of this state are New York and Philadelphia. But a lot of NJ isn’t even suburban: there’s a lot of open country, and even a fair bit of wilderness.

Which brings me to Isaac Asimov.

Asimov, and specifically the Foundation trilogy, was my great inspiration; I became an economist because I wanted to be a psychohistorian, saving civilization through the mathematics of human behavior. But one thing always bothered me: Trantor, the capital of the Galactic Empire, which was described as one gigantic city, completely covering the planet’s land surface — so as to house its population of 45 billion people.

The problem is obvious: as described, Trantor would have a population density of about 600 per square mile; New Jersey has more than 1100 people per square mile. And completely covered in metal it isn’t, unless we’re talking about the turnpike during rush hour.

Update: Yglesias writes in to say that he already wrote about Trantor and about similar confusion in The Caves of Steel. I’d cut Caves a bit of slack, though; it’s obviously a parable about nerdy Jewish kids from Brooklyn and their feelings of inferiority in the face of blond, athletic, but slightly stupid upper-class WASPs.