Julie Anne Workman · CC BY-SA 4.0

An American physicist who built a career studying complex systems — the mathematics of how large numbers of interacting parts, from cells to markets to societies, produce unpredictable collective behavior. He founded the New England Complex Systems Institute to apply that lens to real-world problems, advised policymakers during the West African Ebola epidemic, and in February 2020 founded EndCoronavirus.org, mobilizing volunteers worldwide to push evidence-based policy against COVID-19.