Ever wonder where your dollar bills travel after you plop them down for a cup of coffee? The Web site Where’s George? allows you to do just that: Record your bill’s serial number and then track its journeys as other people spend it across the country. But it’s more than just a game. Because every time a dollar is spent in a new place, it means someone moved it there. Christian Thiemann and Daniel Grady of Northwestern University in Evanston, Illinois, have been using the Web site’s data to study how people move within the United States.

They produced this video to explain their project and animate the results.

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The February 2010 issue of Physics World presents a special focus on Complexity and challenges in Network Science. From mapping the rise of the field, to examples of applications rooted in our everyday life, to charting the field’s possible future evolution, the special issue explores the key topics of Network Science - a field where physicists have been playing a major role.

A special feature is dedicated to infectious diseases, how they rapidly spread in our modern society, and what weapons we have nowadays to fight them. The article titled The Flu Fighters by Vittoria Colizza and Alessandro Vespignani (ISI Foundation and Epiwork coordination) describes the contribution of physicists to an interdisciplinary area where complex systems are the main ingredients, and modeling human behavior and biological contagion is the ultimate challenge.

Physics World, February 2010 issue.

D. Brockmann, "Follow the money"

V. Colizza, A. Vespignani, "The Flu Fighters"

In another special feature, Dirk Brockmann (Max Planck Institute for Dynamics and Self-organization) reveals how information garnered from the geographical movement of banknotes and the location of mobile phones can reveal patterns in how people travel
The cover of the special issue shows an illustration by B. Goncalves et al. of the multiscale worldwide mobility networks used in the GLEaM model.

PNAS Cover Image

In the issue of December the 22nd of the Proceedings of the National Academy of Sciences, we publish a paper that discusses the interplay of human mobility patterns like those between local metropolitan commuters and long-range airline travelers during a global epidemic. The image of the worldwide mobility network constructed in our paper has been featured in the cover of the journal.

Multiscale mobility networks and the spatial spreading of infectious diseases.
D.Balcan, V. Colizza, B. Gonçalves, H. Hu, J. J. Ramasco, A. Vespignani
Proc Natl Acad Sci U S A 106, 21484-21489 (2009).

In the paper we detail the definition of the worldwide multiscale mobility network at the core of the Global Epidemic and Mobility (GLEaM) model and discuss the data integration process and the statistical analysis that allow its construction.