on


When Things Get Complicated

By Jascha Hoffman, 5/30/2004

QUINCY -- What happens when you throw hundreds of complexity researchers together in a Boston-area hotel for a week to study such subjects as how fireflies synchronize their blinking, what started the blackout of 2003, and where Al Qaeda gets its recruits? Chaos, it turns out.

The Fifth International Conference on Complex Systems, held over the course of six days earlier this month at the Quincy Marriott, attracted a swarm of 500 researchers, buzzing from room to room to compare hundreds of original research papers on everything from the inflation of the cosmos to the globalization of sushi.

"The ultimate of interdisciplinary fields," according to the conference organizers, complexity theory has blossomed into a broad movement of scientists searching for universal patterns that occur at all levels of nature and society when local interactions give rise to new collective behaviors. They want to know, for example, how millions of amoebas swarm into a self-directed slime mold, how a trillion-celled organism develops from a single egg, and how markets arise from the interactions of individual human beings.

Complexity theorists want to reproduce these patterns with computer models, in order to gain a kind of insight that equations or statistics supposedly cannot match. What's more, they want to see both the forest and the trees, by viewing big patterns through the local rules of interaction that produce them.

The majority of scientists are skeptical that complexity theory will do much for their fields. But with computer simulations already a staple in biology and finance, and gaining currency in many other fields of inquiry and industry, the vision of a world made for modeling may be catching on.

Steven Strogatz, a Cornell mathematician whose recent book "Sync: The Emerging Science of Spontaneous Order" (Hyperion) describes his research on "synchrony" in fireflies, sleep cycles, and heart rhythms, kicked off the second day of the conference by presenting the curious case of London's Millennium Bridge.

Two days after it opened in 2000, the state-of-the-art suspension bridge was closed due to violent swaying along its 320-meter length. Though carefully designed to withstand wind and even the malicious stomping of a mob of vandals, the bridge's designers had not foreseen that once the bridge started swaying a little, people would synchronize their steps to coincide with its side-to-side motion. This caused vibrations strong enough to knock people off-balance, which, when they righted themselves, caused a feedback loop that snapped the bridge back and forth.

Neo Martinez, a San Francisco State University ecologist wearing a Hawaiian shirt and Converse sneakers, presented his network models of evolving food webs. He showed a series of slowly rotating nest-like structures on his laptop, each one a tangle of thousands of colored spheres representing species, connected by links showing who eats whom. As the model played out, one species would bulge as it sucked the biomass from another, only to shrink again as its predators became more numerous. Designed to match the deluge of data culled from real-world aquatic ecosystems, these models helped him generate artificial food webs to check his intuitions about which feeding strategies lead to equilibrium, and which to oblivion.

These days, a handful of engineers are trying not only to simulate such "emergent" behavior but to actually create it by designing robots that swarm together to produce unforeseen results. Wei-Min Shen, director of the Polymorphic Robotics Laboratory at the University of Southern California, proudly showed video clips recording the first steps of his creature: a set of identical frog-sized robots that can reconfigure themselves on the fly, joining up to form a lizard (in order to climb a hill) that then rips off its own legs to slither away like a sidewinder. With no central brain, decisions made by the robots arise as a collective property of the whole system. Such machines could be useful for exploration, search and rescue, and even combat, says Shen, who is also adapting the technology for a 10-kilometer orbiting array of solar panels planned by NASA.

Speaking about the intertwined histories of physics and the social sciences, the topic of his forthcoming book, "Critical Mass: How One Thing Leads to Another" (Farrar Straus & Giroux), science writer Philip Ball set the stage for dozens of studies of human interactions. Following his remarks, others stepped to the podium to present papers on established topics like game theory and financial modeling as well as more exotic ones like the unearned fame of German fighter pilots and "undoing cult mind-control."

If it seemed that any phenomenon was fair game, no matter how marginal, or how enormous, perhaps it was because researchers believed that with complexity they had discovered a framework for understanding just about everything there is. Yaneer Bar-Yam, the physicist who founded the New England Complex Systems Institute and organized this year's complex-systems conference, sees complexity as nothing short of another scientific revolution.

Bar-Yam noted that the conference itself, with its scientists swarming between six parallel sessions, could be studied as a complex system. Whether someone will simulate it for the next meeting is an open question.

Jascha Hoffman is a writer living in Brooklyn.
© Copyright 2004 Globe Newspaper Company.