Magnetic fields in cities can be used as early warning system for pollution

Researchers now believe we can optimise energy conservation and monitor the ‘health’ of urban areas by studying localised magnetic fields. 

Scientists from the U.S. and Germany are collaborating on a joint study of two American cities – Berkeley, California, and the borough of Brooklyn, New York – which aims to gauge whether a locality’s magnetic footprint can help us understand pollution levels and energy use.

‘A city is viewed as a physical system akin to a distant astronomical object that can be studied using a variety of multispectral techniques,’ explained Vincent Dumont, from Lawrence Berkeley National Laboratory. ‘In short, our project was inspired by our desire to apply what we learned practicing fundamental physics research to the study of cities.’

To conduct the research, the team used a network of sensitive magnetometers, which sourced data over a four-week period, with results synchronized and processed. Analysis shows that the two cities exhibit some stark contrasts, with Brooklyn’s magnetic field present day and night – indicative of 24-7 activity – while Berkeley’s dropped to near-zero by midnight. 

‘Not too surprisingly, we discovered that ‘New York never sleeps,’ or more seriously, there are indeed a number of magnetic signatures specific to each city,’ Dumont continued. ‘This work builds on our earlier experiments conducted around the city of Berkeley, in the San Francisco Bay Area. We identified the dominant sources of magnetic signals – which, not too surprisingly, turned out to be the trains of the Bay Area Rapid Transit (BART) system, and learned to glean weaker signals from this dominant background.’

Pressure is continuing to grow on policymakers and urban planners to bring pollution levels under control, with estimates suggesting toxic air is linked to 9m global deaths each year. 

Image credit: Enzo Ticà