Krugman is very, very insightful when it comes to social physics. His NY Times blog on ‘Gravity’ relates to an article by Adam Davidson on how a gravity model is able to simulate trade between a place called Kanesh in Eastern Turkey near the Syrian border and its trading partners. However Krugman goes on to say that what is important is not just the distance between or size which we might measure as GDP in any two places that trade but what exists in each place – what products are traded. In fact Krugman’s own contributions to trade theory suggest that counties and cities are more similar with respect to size and what they produce that once was thought and this to an extent supports distance and size effects. The gravity model works rather well. Tobler and Weinberg anticipated Davidson in their work on trade in Cappadocia which they published in 1971 in Nature (May, 231, 39-41) , but Krugman’s real contribution in his NY Times article is to suggest that the gravity model is a baseline from which all else must be measured when it comes to interaction theory in general and trade in particular. Lionel March and myself following James S. Coleman articulated all this for gravity models in our paper The Method of Residues in Urban Modelling which we published in Environment and Planning A in 1976 (April, vol. 8 no. 2 189-214). Essential reading – we would say that wouldn’t we – but a lot is wrapped up in Krugman’s article as in many of his works.
A diverse selection of talks on the Science of Cities at the 2015 Conference on Complex Systems, starting this afternoon in the Sheraton Airport Hotel in Tempe AZ Canyon Room. My own talk is about our Future Cities Catapult Land Use Transportation modelling work where we are building a model called QUANT of all zones defining the UK – well England and Wales first – but it will be extended to Scotland. In fact as long as you use a decent browser that supports WebGL then you can get access to the rudimentary alpha version so far by clicking on this link http://quant.casa.ucl.ac.uk/
My European Research Council (ERC) grant comes to an end in 3 months time. You can hear me talk about the project courtesy of an ERC podcast by clicking here but in this post I will tell you what the project is about. It is about developing what myself and others call a science of cities, a new science in some respects but not the only science by any means. Its acronym is Mechanicity which unpacks as Morphology, Energy & Climate cHANge In the CITY. We have done a lot on urban morphology and somethings on energy as flows in the city. Climate change of course is the backcloth to everything that is happening in cities as we try to move to a more sustainable future but the core of our work has really been on city size and structure, working with new notions about scaling and diffusion, ways ot thinking of the properties of cities as they scale in terms of networks and transportation systems, and at the same time, building operational models of such systems: good old fashioned transportation models that are consistent with form and function and dynamics to some extent but mainly statics. To pull our work together, we are developing a new web site from our old one and in a few months it will be online and as one stop shop for getting access to our material. Elsa Arcaute and myself are pulling these ideas together and we are also extending them into a project on the distribution and performance of cities of different sizes in Britain and elsewhere. Watch this space. The podcast and the ERC publicity that you can get from the web page if you click on the image above gives you some sense of this project.