Critical Mass
by Philip Ball
Summary
Ball's subject is an old dream renewed: a physics of society. Thomas Hobbes, writing amid civil war, tried to derive government from Galilean first principles; Ball's book is the story of that ambition's modern, unexpected vindication, not through reducing people to atoms, but through the discovery that large numbers of interacting agents, molecules or motorists or traders, produce collective behaviour with laws of its own.
The physics supplying the tools is the theory of phase transitions: water knows nothing of ice until, at a threshold, everything changes at once, and the mathematics of such transitions turns out to describe an astonishing range of human phenomena. Ball works through the casebook: traffic, where jams condense out of free flow like a change of state, and the models that explain a phantom jam with no cause; pedestrian crowds and their spontaneous lanes and fatal crushes; the growth of cities and firms, obeying power laws nobody legislated; financial markets, whose crashes look less like rational adjustment than like avalanches in a pile of sand; the spread of fashions, crimes and epidemics through networks; small worlds and six degrees; voting, alliances, and the game theory of cooperation and conflict.
The book is generous with its history, Hobbes to Adam Smith to statistical mechanics, and scrupulous about the limits: statistical man is not actual man, and Ball never pretends otherwise.
More than five hundred pages, encyclopaedic and clear.
Best for readers who want the definitive tour of complexity science applied to human affairs, before the phrase social physics was worn smooth.
Historical Context & Significance
Critical Mass won the Aventis Prize in 2005, recognition for its scale and ambition, and for its author's unusual position: Philip Ball, a chemist and physicist by training, spent over twenty years as an editor at Nature, a perch from which he watched every field at once, and his books, on water, on colour, on pattern formation, on music, on quantum theory, have made him one of Britain's most prolific serious science writers.
The book codified a field just as it was naming itself: econophysics and computational social science took off in the following decade, and the smartphone era then supplied the mass behavioural data the models had lacked, making the book look prescient and, its sceptics note, making its cautions about statistical man more necessary rather than less.
Ball kept producing at a rate that became a running joke in science writing; the prize shortlisted him again in 2014 for Serving the Reich, and this remains his largest single statement.