City is like Blood System
Interesting article from The Economist explaining how much have cities' networks of roads, railways, electricity, etc. in common with the blood vessels of animals or the sap-carrying xylem and phloem of plants:
Steven Strogatz, a mathematician at Cornell University, wrote last year that Manhattan and a mouse might just be variations on a single structural theme. His point was that both are, in part, composed of networks for transporting stuff from one place to another.
Peter Dodds of the University of Vermont draws a particular analogy between the blood system and a suburban railway network. The commuter-rail system of a city ramifies from the centre. The farther out you go, the sparser it is. By analogy, Dr Dodds predicted, the network of capillaries (the tiny blood vessels that permeate tissues) would not be as dense in large animals (where many of them are far from the centre) as it is in small ones. They, too, branch ultimately from a central source—the heart. Surprisingly, no one had looked for this before, but in a paper published recently in Physical Review Letters Dr Dodds shows that this does indeed turn out to be the case.
