If you just run the same calculation on the moon, its width compared to distance is indeed somewhat less than that still. So should be accurate.
An eight hundred mile radius would make the city much bigger than France, though.
You're right, France is more like an 800 mile diameter, not radius (or at least, France is about an 800 mile width). I think I realized that at some point, but then forgot. My city is more like a 600 mile radius to most points, 800 to the farthest points. So definitely bigger than France. I might scale that down a bit, but not too much.
And yeah, the calculation does work for the moon, so I suppose I should trust it. It seems so strange, but it must be correct.
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