Scientists Follow The Money

A group of creative physicists have given new meaning to the phrase "follow the money." The researchers tracked the movements of half a million US dollar bills using the internet in order to learn about peoples' traveling behavior.

Each line in the image above represents the movement of a single banknote. The bills were released from various destinations across the country, but mainly from Seattle (blue) and New York (yellow). The money was followed using the bill-tracking website www.wheresgeorge.com.

The researchers were surprised to learn that the number of people traveling long distances in crowded cities like New York was roughly proportional to that of less populated cities. The same was also true for the number of people traveling short and intermediate distances.

Scientists had previously assumed that populous cites would have a higher number of people making long-distance treks simply because there were more people traveling and more transportation options were available.

The researchers concluded that people's traveling behaviors follow universal laws. They suggest that a better understanding of these laws could help scientists create better models for the spread of infectious diseases.

The study is detailed in the Jan. 26 issue of the journal Nature.