A High-Energy Physicist on Poop-Scooping and the Future of ‘Superexponential’ Cities

Cities thrive because of social interaction, says Geoffrey West. An example: Picking up after your dog rapidly went from weird to expected.

The eminent British-born physicist Geoffrey West wanted to talk about poop-scooping. Not physics, even though he founded the high-energy physics group at Los Alamos National Laboratory. And not the Santa Fe Institute, even though he was president of the interdisciplinary think tank in New Mexico from 2005 to 2009. West’s new interest is everything about cities, from energy inputs to, yes, dog waste. He sees the urban public’s relatively recent embrace of poop-scooping as an example of the power of social interaction in cities, where both good and bad things seem to happen more and more quickly than in smaller communities.

“In cities now, one is very conscious of the fact that people go around picking up dog poop,” West told me. “Twenty or 30 years ago, this would be unthinkable. At some stage, it changed; it felt like almost overnight. Suddenly, everybody was picking up dog poop.” 

To West—whose poop epiphany resulted from dog-sitting for his son in Los Angeles recently—the change in custom resembles changes in materials like freezing, melting, and evaporation. “Sometimes there’s a highly coherent effect, when the whole system goes through what in physics we call a phase transition. The effects of all these local interactions suddenly become long-range.”

The analogy is characteristic of West, 76, who is applying the framework of physics to a whole new realm. Earlier this year he came out with a book called Scale: The Universal Laws of Growth, Innovation, Stability, and the Pace of Life, in Organisms, Cities, Economies, and Companies. (There is probably a hidden joke in the fact that the scale of the subtitle is so much grander than the scale of the main title, Scale.)

I cited West’s recent work in the Remarks column of Bloomberg Businessweek’s special issue on cities. But that mention just scratched the surface of a wide-ranging interview. How wide-ranging? Consider this excerpt from the table of contents of Scale:

From Godzilla to Galileo • Misleading Conclusions and Misconceptions of Scale: Superman • Orders of Magnitude, Logarithms, Earthquakes, and the Richter Scale • Pumping Iron and Testing Galileo • Individual Performance and Deviations from Scaling: The Strongest Man in the World • More Misleading Conclusions and Misconceptions of Scale: Drug Dosages from LSD and Elephants to Tylenol and Babies • BMI, Quetelet, the Average Man, and Social Physics • Innovation and Limits to Growth ...

The core idea of Scale is that cities, like living organisms, obey certain laws of growth. For example, an elephant consumes only 100 times as much as a rat even though it weighs 1,000 times as much. That’s a difference of three orders of magnitude on metabolism vs. four orders of magnitude on mass, for a metabolism-to-mass scaling law of ¾. The Swiss-born scientist Max Kleiber discovered in the 1930s that this ¾ (or 0.75) scaling law works for nearly all creatures, from gnats to blue whales.

Now West and others—including his former colleague Luis Bettencourt and Cornell University’s Steven Strogatz—are finding that scaling laws apply to cities as well. The metabolism of a city, measured by such things as the number of gas stations per capita, grows at a power of about 0.85 vs. population. So the bigger a city is, the lower the resource consumption per capita. “In this sense, New York City is the greenest city in the United States,” West writes in Scale.

What makes cities different from creatures is that sociological phenomena—from such good ones as patenting and personal income to bad ones like crime—scale faster than population, at a power of about 1.15, according to West and other physicists and mathematicians in his circle. Los Angeles is richer per capita than Oklahoma City, London has a higher crime rate than Oxford, and so forth. It seems that the more people there are in a city, the more opportunities there are for chance encounters. More interactions lead to a more rapid pace of change. People in big cities even walk faster.

Not everybody buys this brand of urban physics. Joel Kotkin of Chapman University told me that the energy consumption of cities tends to be under-measured, for example. Edward Glaeser of Harvard University said that he prefers to focus on why cities grow rather than on particular values of scaling laws.

But West says the 1.15 number is very real—and ominous. The reason is that when a function is “superexponential,” it heads toward infinity. Cities keep getting bigger and the pace of life picks up, and there’s no flattening out.

“We’re not only living on an accelerating treadmill that’s always getting faster and faster, but at some stage we have to jump onto another treadmill that is accelerating even faster …” he writes in Scale. “And this entire process has to be continually repeated into the future at a faster and faster rate. This is an extraordinary image and sounds like some bizarre psychotic behavior.”

West may be a tad too worried. The growth rate of most of the world’s biggest cities has already slowed; demographers predict that the most rapid growth will occur in second-tier cities. And the overall world population growth is falling as well. The American economist Herbert Stein used to say, “If something can’t go on forever, it will stop.” Heinz von Foerster of the University of Illinois gently mocked population alarmists in a 1960 article in the journal Science with a headline that read, “Doomsday: Friday, 13 November, A.D. 2026: At this date human population will approach infinity if it grows as it has grown in the last two millenia [sic].”

West has been around long enough to have heard the optimistic takes and he’s not persuaded: “Given the special, unique role of cities as the originators of many of our present problems and their continuing role as the superexponential driver toward potential disaster, understanding their dynamics, growth, and evolution in a scientifically predictable, quantitative framework is crucial to achieving long-term sustainability on the planet,” he wrote in Scale.

As he put it to me: “We’re just mindlessly charging ahead, thinking it’s all going to work out.”

    Peter Coy
    Bloomberg Businessweek Columnist
    Peter Coy is the economics editor for Bloomberg Businessweek and covers a wide range of economic issues. He also holds the position of senior writer. Coy joined the magazine in December 1989 as telecommunications editor, then became technology editor in October 1992 and held that position until joining the economics staff. He came to BusinessWeek from the Associated Press in New York, where he had served as a business news writer since 1985.
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