At the 2014 American Association for the Advancement of Science (AAAS) meeting in Chicago today, SFI Professor Luis Bettencourt discussed the relationships among urban growth, creativity, and sustainability.

Bettencourt, a physicist, says he has always been fascinated by people and how they interact. He became interested in a scientific understanding of cities a decade ago.

“Often when we think about cities, we go straight to policy or engineering,” he said. “What has been missing for me is we have never had a multidisciplinary view so we don’t make mistakes when we make policy decisions.”

Rapid urbanization, especially in Asia and Africa, is reconfiguring human society, both in space and function, he said. More than half the world’s population now lives in urban centers, and the rate of urbanization is increasing.

Some of the models we used to build cities in the United States are being emulated in other parts of the world, he said. Beijing and Sao Paulo are now experiencing some of the worst traffic jams in the world. But these models are not sustainable, he noted as he showed a slide depicting a 16-lane highway with bumper-to-bumper traffic. “You’d assume this is L.A., but it’s Beijing,” he said.

So far, ideas to create smarter, highly instrumented, sustainable cities are just that: ideas. “They’re not yet reality,” he said, showing an image of a model for a planned arcology project, Masdar City, in the United Arab Emirates.

Bettencourt said that to make good decisions about how to engineer sustainable cities, we need a science of cities, something he and SFI’s Cities & Urbanization Team has been working on.

He described results demonstrating that many urban metrics, from cost of living to wages to GDP, increase in a predictable, regular way as city population grows, showing a slide of the speed at which people walk in dozens of cities around the world.

“Cities all behave in the same way,” he said. “Everything in socioeconomics seems to be accelerated in a regular way as the city grows.”

This regularity, he said, is a function of social networks; it’s the interdependence of people in space and time that allows us to specialize and engage in creative pursuits, to create wealth and knowledge, he said.

Bettencourt’s recent research suggests that the social benefits of living in denser cities tend to balance themselves with the costs of moving around, and that the healthiest, most productive cities are near a mathematical sweet spot, where social interactivity are highest and transportation costs are lowest.

He thinks of cities as social reactors; like a star, cities burn brighter as interactions get denser. This is true of all cities, regardless of their size or location in the world, and even across time scales; a paper out this week in PLOS ONE, in fact, shows that mathematically, ancient cities were no different from modern ones.

“This is a tremendous time to look at cities, because it’s the first time we can measure human interaction on this vast scale,” he said. “If you look at city as a process…then you have sort of a picture of what is the science that needs to be done to help cities work better.”

He said we need to view cities in three ways: how they work, how they are engineered, and how technologies enable cities to function. Individually, none of these views will give you a complete picture.

“If we do this, we will get a better understanding of how we can build more sustainable cities as well as what it means to be human,” he said. “It’s a exciting time.”