SFR Talk: Big Questions

With Geoffrey West

If you missed the last episode of WNYC’s Radiolab (and if you did, shame on you) or the last issue of Nature (more understandable), then you missed Geoffrey West, a theoretical physicist at the Santa Fe Institute, explaining his research on city size and behavior. As the size of a city increases, West says, so does almost every socioeconomic aspect: libraries, AIDS cases, wealth, even the speed at which people walk and talk. That correlation runs counter to West’s previous lifespan-of-organisms research, which constructed a mathematical model to explain why, as organisms increase in scale, less energy is needed per cell, thus allowing organisms to live longer. SFR spoke to West about the differences between animals and cities, biology and physics, and the ever-outlying Santa Fe.

SFR: How does the framework of biology differ from that of physics?
GW: It’s a mathematical, quantitative, predictive framework, much more using ideas in physics than the qualitative, narrative way that biology has traditionally been done. That’s been the traditional divide between them. When you think about biology, the thing you’re confronted with is the overwhelming complexity of life, and it looks like, ‘My God, can you imagine that there are any general rules operating here that can be put to use in a mathematical framework, that operate on a cell, operate on a mouse, operate on a forest?’

Did you jump right into studying cities, or did you study other introductory subjects?
I didn’t think when I started at all, ‘My God, I’m going to address some of the biggest questions,’ but I did want to address a big question, and that was the question of aging and death. But also, now, to bring in the physics perspective, ‘Can I understand why the lifespan, so to speak, of the average human being is on the order of 100 years?’

It's not on the order of 10 years or 1,000 years, it's on the order of 100 years. Why is that, and how is that related to the timescales on the microscopic molecular level of genes and complex molecules that control life? How the hell do they know that the organism they are part of should be dying in 100 years? And, also, how can it be that those same molecules, if they were part of a mouse, have to be dead in two or three years?

What we eventually crafted was a complete theory of the origin of these [timescales], and it’s based on the idea that what these scaling laws—these kind of systematic, universal scaling laws are manifesting, are the generic universal properties of the multiple networks that sustain life. So everything from your respiratory system to your neural system to networks within cells, all of these networks have universal mathematical properties and are governed by principles of network theory.

Was studying the networks within organisms what led you to study networks between organisms, ie cities?
Exactly. It’s obvious that a city, or even a company, has network structure. Not even at the social level, just at the physical level, a city has roads and gas stations and pipelines, which are networks. But it also has something more abstract and, in some cases, something more sophisticated than in biology. And that is networks of social interactions, which are where things like information and knowledge are being translated.

If you go back to biology, another way of saying it is that—let's just think of mammals. The fact that the whale is in the ocean and the elephant has a big trunk and the giraffe has a long neck and we walk on two feet and the mouse scurries around, these are all superficial characteristics. And in terms of their functionality, their physiological design, their organization, their life history, the essence of what they are, they're actually all scaled versions of one another. We are, at some 90 percent level, just a scaled-up mouse. And the question is, is that true of cities? Is New York just a scaled-up San Francisco, which is a scaled-up Boise, which is a scaled-up Santa Fe, even though they look completely different?

So what we did is look at all this data, everything from number of gas stations to length of electrical cables to number of patents they produce to number of police and crimes and spread of AIDS disease and wages, everything you could lay your hands on, and ask, 'If you look at those functions of city size (population), is there some systematic progression?' And to our amazement, actually, there is. So, in some average way, Santa Fe is a scaled-down New York City.

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