Urban Physics - A Look at City Dynamics

Can cities really be looked at as clusters of molecules?


The next time you're on a plane flying over a city, take a look at what's below you - there will be grids of buildings, back alleys and pavements combining to create patterns, all of which become the make-up of an entire city.

If you're high enough, the prominent buildings and roads start to look like something entirely different, and if you're Franz-Josef Ulm, engineering professor at the Massachusetts Institute of Technology, or a follower of his work, you might even say that the view looks more like a cluster of molecules.

Borne out of a 'eureka' moment when Ulm was having coffee with his colleague, the discovery has since gone on to inspire research that's bringing together the dissimilar fields of physics and urban planning, with the hope that it will help architects and urban planners.

Ulm's work has concluded that cities can be grouped into distinct categories. New York for example shares the same molecular structure as crystal, whereas Seattle and Los Angeles can be defined as separate liquids. Although not incorporated into an academic study as of yet, the hope is that Ulm's work will allow for a city's structure to be better understood, including its energy use and how it's reacting to climate change.

In an article in the Boston Globe, Ulm states, 'Boston has grown organically, the city, in the way its buildings are organized today, carries that information from its historical evolution'. Boston's structure is far different from New York's, and more similar to Los Angeles', a surprising find considering the proximity of the two East-coast cities.

According to Ulm, his research has two main applications. In the same Boston Globe article it states, 'First, it could help predict and mitigate urban heat island effects, the fact that cities tend to be several degrees warmer than their surrounding areas — a phenomenon that has a major impact on energy use'. His work should also be able to decrease a city's vulnerability when it comes to extreme weather conditions.

This research isn't just a way of categorising cities, it's a new way to understand them. Cities have become far more complex machines, and with the urgency around global warming increasing all the time, Ulm's work could be an excellent tool going forward but it'll be important that it gets scientific certification in the not too distant future. 


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