A Healthy Interest Dynamic Features, Such As Segregation Or Polynucleated Growth

NATURE|Vol 441|15 June 2006 BOOKS & ARTS

A growing urban problem

Cities and Complexity: Understanding Cities with Cellular Automata, Agent- Based Models, and Fractals

by Michael Batty S. GALLUP/GETTY MIT Press: 2005. 648 pp. $60, £38.95

Frank Schweitzer Urban growth is one of the biggest challenges for humankind in the twenty-first century. The world’s urban population is at present estimated to be growing by about 50 million people per year. This growth is still almost exponential, and saturation may be reached only by the middle of the century. So there is much discussion about estimates of land con- sumption, the manageable size of megacities, and simple ways to structure, if not to control, this vast spread of urbanization. For this, a better understanding of the spa- tial dynamics of urban growth should be a precondition. In fact, urban planning, urban geography, urban economics and other related disciplines have put quite some effort into this problem. Although they provide insight into some details, they do not present the big The expanding sprawl of cities such as Athens highlights a need to understand urban growth. picture of generic mechanisms underlying these complex dynamics. So it is reasonable the reader to play with the ideas discussed should agree that this complex-systems per- to consider whether the theory of complex in the book. Unfortunately, the plan to put spective sheds new light on to the dynamics of systems developed in different scientific areas examples from the book together with related urban evolution by highlighting relations to over the past 30 years may provide a suitable material on a website (www.complexcity.info) seemingly distant phenomena, such as swarm- toolbox for gaining such an insight. is yet to be realized. ing or epidemics. Apart from the necessary In Cities and Complexity, Mike Batty, an The book certainly succeeds in making the technical details of the models, the author expert in the area of urban modelling, unfolds topic of urban growth accessible and inter- gives a number of illustrative examples and the different aspects of urban change in rela- esting to those already familiar with formal facts to elucidate his viewpoint, widening the tion to complex systems theory. The focus is modelling of complex systems. However, prac- appeal of the book to a broader audience. ■ on models and computer simulations: there is titioners in urban planning may find some Frank Schweitzer is chair of systems design at no introduction explaining what we already of the concepts and models too abstract and ETH Zürich, Kreuzplatz 5, 8032 Zürich, know about cities and growth, or any attempt ‘academic’ to give solutions. But at least they Switzerland. at orientation on the phenomenological side. This is good and bad at the same time. Some readers will certainly miss a clear relation between cities as we know them and the rather abstract models and results for specific A healthy interest dynamic features, such as segregation or polynucleated growth. Others, however, will Doctor Franklin’s Medicine to do the same for the rest of his long life. appreciate the insights into generic features of by Stanley Finger In Doctor Franklin’s Medicine, Stanley Finger urban dynamics that can only be highlighted University of Pennsylvania Press: 2006. has assembled Franklin’s many interactions at the abstract level used. As the author puts 400 pp. $39.95, £26 with medicine, health and doctors. Given the it, the focus is “largely on experiments with attention that the iconic Franklin has already models that provide us with analogies as to W. F. Bynum attracted from historians, there are few sur- how cities develop and evolve”. If the creation of the American Republic can prises here, but the impact of the whole pack- These analogies are investigated on very dif- be taken as a high point of the Enlightenment, age is formidable. Most doctors would have ferent modelling levels relating to the different then Benjamin Franklin (1706–1790) is a cen- been well satisfied to have so changed the face scales of urban dynamics. Models of fractal tral figure. Unlike many of the other Founding of medicine; Franklin did it almost inciden- growth show analogies to the morphological Fathers, he came from a humble background tally, in the midst of a busy life as a natural structure of urban aggregates, and models of and had a gentle sense of humour. Self-taught, philosopher, diplomat and man of the world. moving agents resemble the motion of pedes- he made his initial reputation as a printer Franklin lived most of the second half of his trians on streets and inside buildings. Many and publisher, especially of Poor Richard’s life in England and France, on official business of these models use cellular automata, which Almanac, a phenomenally successful annual in first on behalf of Pennsylvania, and then of the allow a broad range of topics such as land-use a crowded market. In the almanac, Franklin’s new nation. He was known abroad primarily as patterns or regeneration of urban areas to be alter ego, Poor Richard, offered advice and an electrician, a word that in those days carried addressed. A ‘desktop simulator’ is described homespun wisdom about health and much rather different connotations. Through his in more detail in one of the chapters, tempting else besides. In his own persona, Franklin was famous experiment with a kite and lightning,

815 © 2006 Nature Publishing Group BOOKS & ARTS NATURE|Vol 441|15 June 2006 he did for electricity what Newton had done likely sources of toxic levels of the metal. He the French occasionally assumed that he was with gravity: related the heavens to the Earth. suffered from gout and bladder stones, a prob- medically qualified; in fact, ‘Doctor Franklin’ It was as an electrician that Franklin was lured able consequence of the poison to which he had several honorary degrees but no formal into the practice of medicine: he was several helped alert the public. medical training. Nor did he apparently need times asked to electrify patients with nervous There were other inconsistencies in his it. He moved easily in medical and scientific disorders. Always suspicious of grand specula- philosophy of health. He advocated the health- circles, respected by the French and welcomed tion, and a careful observer, he never claimed giving properties of fresh air, although as a in Britain even after the United States had sev- more for the therapeutic potential of his brain- social man he thrived in the clubs of urban ered its ties with the mother country. Franklin child than his own experience warranted. centres such as Philadelphia, London and had signed the Declaration of Independence, Several of his interactions with medicine Paris. He also preached the virtues of exercise, but he was always a man of peace. As he have biographical poignancy. He advocated believing that swimming was an undervalued wrote in 1783: “There never was a good war, or inoculation for smallpox (he died shortly activity, and swam even after he became very a bad peace.” ■ before Edward Jenner introduced vaccination), corpulent in his old age. W. F. Bynum is at the Wellcome Trust Centre for but lost one of his own uninoculated children Other medical contributions were unam- the History of Medicine, University College to the disease. Ever alert to the dangers of lead biguous. Franklin invented and wore bifocals, London, London NW1 2BE, UK. poisoning (among printers who used lead type, and used an ingenious mechanical arm to as well as other occupational groups), Franklin grasp books and other objects on high shelves, MORE ON BENJAMIN FRANKLIN collaborated with George Baker, the British a natural consequence of his large private The First Scientific American: Benjamin physician who exposed its high levels in cider library. He was a founder of the first public Franklin and the Pursuit of Genius and other alcoholic drinks kept in lead vats. hospital in America, the Pennsylvania Hospi- by Joyce E. Chaplin Franklin himself loved Madeira and port, two tal. So close was his relation to medicine that Basic Books: 2006. 362 pp. $27.50 Home from home History is brought to life at Benjamin Franklin’s house in London.

Colin Martin sound described as “the voice of angels”. account of coagulation. Hewson lived at the Arguably the most famous American in the He worked with Joseph Priestley on house from 1770 to 1774 after he married Age of the Enlightenment, Benjamin Franklin experiments that led to the discovery of Polly Stevenson, the daughter of Franklin’s achieved scientific fame by flying a silk kite oxygen; recorded the effects of the Gulf landlady. The medical-history room in the with a wire rod at one end and a key at the Stream and other ocean currents; science study centre continues this tradition other into a thunderstorm in Philadelphia in investigated canal depths and their with ingenious models and touch-screen 1752. He thus demonstrated that lightning implication for transport; and demonstrated computers to encourage schoolchildren to consists of flashes of electricity. the veracity of the old adage that oil calms think about how the human body works. During his long life, Franklin The house is interpreted for made many contributions to visitors in an evocative ‘museum several branches of science. He as theatre’ tour, which found research a welcome respite incorporates state-of-the art from his role negotiating the audiovisual display techniques and M. DE GUZMAN turbulent complexities of an actress in eighteenth-century contemporary diplomacy, dress who plays the role of Polly including the repeal of stamp (see picture). Polly’s interest in duty, which the British parliament Franklin’s diplomacy and science had imposed on its American made her one of his closest colonies in 1765. confidantes. “After writing six folio This year marks the 300th pages of scientific philosophy to a anniversary of Franklin’s birth, the young girl, is it necessary to finish cue for activities around the world such a letter with a compliment?” (see www.benfranklin300.org). asks Franklin during an audiovisual It has been celebrated in London presentation. “Is not such a letter by the public opening of the Tour de force? Polly acts as guide in Franklin’s London home. of itself a compliment?” 1730s Georgian townhouse, at Despite his skilled diplomacy, 36 Craven Street, where he lived for 16 years troubled water, on a windswept pond in the and his satirical Rules By Which a Great Empire as an agent for the Pennsylvania Assembly. London suburb of Clapham. Some of these May be Reduced to a Small One, written in The newly restored house serves as a achievements are recreated as hands-on 1773 to warn the intransigent British of museum and education centre (see experiments for school children at the centre the dangers of taking a hard line against www.benjaminfranklinhouse.org). as an introduction to scientific methodology. hot-headed American colonists, Franklin During his years in London, Franklin During the recent restoration of the house, failed to avert the War of Independence. In invented bifocal spectacles; developed some 1,200 human bones were found in the 1775, he hurriedly left Craven Street. By the a fuel-efficient fireplace draught called basement. They were identified as remains time he had returned to Philadelphia, the the Franklin stove; installed a new, more from an anatomy school founded at the American Revolution had begun. He died effective lightning rod on the dome of house by William Hewson, a British in 1790 at Passy near Paris, with Polly and St Paul’s Cathedral; and invented the glass anatomist who identified the role of Franklin’s own daughter Sally at his bedside. armonica (or harmonica), with its haunting fibrinogen in 1770 and gave the first valid Colin Martin is a writer based in London. SCIENCE IN CULTURE