Entropy: It’s the Law

I am having some fun thinking about the physics of cities today, hence the cheesy post title. The NPR Cities Project has been trying to capture “the vibrancy of urban life today” and that includes producing a great set of short pieces about cities, taking every angle imaginable. One of my favorites is written by Adam Frank, an astrophysicist at the University of Rochester. I am particularly partial to physicists, but he does have some pretty fascinating ideas.

Frank sees cities as analogous to a big engine — a system that is designed to turn energy into work. Food, electricity, fuel: these are all inputs to the city engine that allow people to do business, travel from place to place, and generally be productive. The interesting part of this is that Frank ties this energy-work relationship to the second law of thermodynamics. The first law of thermodynamics tells us that energy can be converted from one form to another but it cannot be created or destroyed. The second law says that in going from one form of energy to another (from energy to work, or coal into a moving vehicle) there is waste. Always. He says, “Use a load of coal to drive a steam-powered locomotive and some of the coal’s energy ends up heating the locomotive itself, leading to wear, tear and eventual decay. Physicists call this waste entropy, but what it really means is disorder.”

So if cities are big engines of energy-work transfer, then they’re also big sources of waste or entropy. Cities contribute to the increasing chaos of the universe (that’s heavy). The examples Frank gives of this entropy are the heat shimmers from buildings and roads and the general “din” of a city, the acoustic waste.

One of the big points with all of this is that if we’re going to have an urban world, as we do at the moment, we will always have to account for the waste and disorder that accompanies cities as they transform energy into work. Frank says, “no matter how clever we are, there will always be disorder, waste and pollution following in the wake of our work organizing societies into cities.” It’s the law.

Keeping with the physics analogies (realities?), there can be varying levels of entropy (waste) in the same system depending on the relative amount of order. Can this be the basis for sustainable solutions? Frank hints at this but doesn’t say it outright. He gives the example of a box filled with gas molecules. All of the molecules could be bunched up in the corner — high order, low entropy. Or they could all be floating around and bumping into each other — low order, high entropy. Do cities actually have more order than distributed populations? Are there ways to increase the order of cities? Is this a feasible decision criteria and how different is it from our current criteria for efficiency or sustainability? I am not sure if these are different terms for the same ideas but it would be interesting to sit down with a physicist and discuss.

Speaking of chaos and disorder, I am supposed to be leaving for New Orleans on Thursday to attend the American Political Science Association’s annual meeting…but Hurricane Isaac may have other plans.

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