Just a nitpick here, but when you write > breaking the global graph up into connected subgraphs I feel like it's too conservative -- and takes "the transporta

Just a nitpick here, but when you write > breaking the global graph up into connected subgraphs I feel like it's too conservative -- and takes "the transportation graph" as too fixed an entity. Consider how much the shape of the U.S. changed between 1917 and 2017 -- suburbs, the Interstate Highways, malls, fast food, huge parking lots, and on and on. The car literally gave us new ways of living with each other, for better and for worse. So I think we should expect changes at least that radical in the next hundred years -- which suggests that we'll not just divide some abstract, eternal graph differently, but really truly reshape it. I can't wait for super-fast trains + self-driving cars, AND I can't wait to see what kind of world they create.