Skip to main content

Flow – Philip Ball ****

This is another of Philip Ball’s quirky, scholarly, illuminating studies of the patterns of nature, the second in a trilogy. The others deal with shapes and branches; this one deals with flow of all kinds, from convection in the sun to avalanches in a pile of rice.
Ball has struck popular science gold with this trilogy, because he has a subject matter that is at the same time scientifically intriguing, visually engaging, and easy for the layperson to grasp. Fluid flow – the paradigm of flow in this book – is a typical case. Eddies and turbulence are interesting for scientists because they are horribly complicated. But because they are horribly complicated, the only hope of understanding many features of fluid flow is through a kind of simple qualitative modelling, the kind that is easy to explain to a popular audience. The Kelvin-Helmholtz instability, for example, is a mechanism by which flowing water forms wavy currents. It is a simple mechanism, communicable in a picture, and it creates delicate plumed patterns in water that make great images. And like most of the patterns in this book, it crosses mediums easily – it is present in clouds as well as rivers.
It turns out, as Ball reveals in the last chapter of the book, that real turbulence is not susceptible to any simple models like the Kelvin-Helmholtz model. But this is a rare exception. And even with turbulence Ball finds a pretty way of illustrating the science: he concludes as he began the book, with a work of art. This artistic theme – the first chapter is about representations of fluid flow in Western and Eastern art, with a focus on Leonardo da Vinci – is typical of Ball’s playfulness in this trilogy, his fondness for interesting diversions. These are indeed diverting, but they can also be disorientating. In the case of this volume, I finished the first chapter without having much idea of what the book would be about.
This book is certainly about something, though, even if it that something is hard to pin it down. It’s about fluid motions, of course: aside from the relatively conventional topics of water flow and convection, we have intriguing chapters on the collective behaviour of grains (in dunes, piles, and sheets) and on the movement of flocks of animals, crowds of people, and lines of traffic. But it’s also about deeper themes, which Ball mentions now and then but never instructs us about systematically. It’s about trying to describe and understand a wide class of phenomena through a single parameter – whether it is Rayleigh’s number for describing the tendency of fluids to give convection patterns, or Reynold’s number for describing the eddy-forming habits of a liquid stream. In a vague way it is about self-organisation, the capacity of macroscopic entities to form complex patterns with no outside help except a steady influx of energy. And in a fleeting way it is also about self-organising criticality, the quality that some phenomena have of spontaneously entering highly unstable states – a quality that the now-legendary sand-pile is supposed to have.
Readers who are not interested in these themes, perhaps because they would rather see them treated front-on rather than in the occasional sidenote, will still find plenty to enjoy in this book. The simplest pleasure it offers is to witness similar patterns in disparate phenomena: lane-forming on human footpaths and in the trails of army ants; convection not just in boiling water but inside the earth, in clouds, in cereal packets, and in the regularly-spaced circular craters that shape some landscapes in Norway and Alaska. Another of the book’s pleasures is its narration of the process of science, the sequence of attacks by different scientists, using different methods, on the same problem. In Flow, Ball’s account of successive attempts to explain sand dunes is typical of his blow-by-blow coverage of the process of discovery.
The breadth and detail of Ball’s interests in this book means there are many other pleasures besides, from the historical (Faraday’s prescient thoughts on convection in grains) to the domestic (an explanation of why shaking a cereal packet drives the chunky bits to the top). The downsides are that the scientific detail is sometimes heavy-going, and that the underlying themes of the book (aside from the general idea of fluid motion) are nebulous. On a more specific note, Ball’s discussion of self-organising criticality did not ease much of my confusion about that topic. On the whole, however, Flow deserves its place in Ball’s trilogy – and that is high praise.
Review by Michael  Bycroft


Popular posts from this blog

The AI Delusion - Gary Smith *****

This is a very important little book ('little' isn't derogatory - it's just quite short and in a small format) - it gets to the heart of the problem with applying artificial intelligence techniques to large amounts of data and thinking that somehow this will result in wisdom.

Gary Smith as an economics professor who teaches statistics, understands numbers and, despite being a self-confessed computer addict, is well aware of the limitations of computer algorithms and big data. What he makes clear here is that we forget at our peril that computers do not understand the data that they process, and as a result are very susceptible to GIGO - garbage in, garbage out. Yet we are increasingly dependent on computer-made decisions coming out of black box algorithms which mine vast quantities of data to find correlations and use these to make predictions. What's wrong with this? We don't know how the algorithms are making their predictions - and the algorithms don't kn…

Infinity in the Palm of your Hand - Marcus Chown *****

A new Marcus Chown book is always a treat - and this is like a box of chocolates: a collection of bite-sized delights as Chown presents us with 50 science facts that are strange and wonderful.

The title is a quote from William Blake's Auguries of Innocence: 'To see a World in a Grain of Sand, / And a Heaven in a Wild Flower, / Hold Infinity in the palm of your hand, / And Eternity in an hour.' It would seem particularly appropriate if this book were read on a mobile phone (so it would be literally in the palm), which could well be true for ebook users, as the short essays make excellent reading for a commute, or at bedtime. I found them distinctly moreish - making it difficult to put the book down as I read just one more. And perhaps another. Oh, and that next one looks really interesting...

Each of the 50 pieces has a title and a short introductory heading, which mostly give a feel for the topic. The very first of these, however, briefly baffled me: 'You are a third mus…

How to Invent Everything - Ryan North ****

Occasionally you read a book and think 'I wish I'd thought of that.' This was my immediate reaction to Ryan North's How to Invent Everything. The central conceit manages to be both funny and inspiring as a framework for writing an 'everything you ever wanted to know about everything (and particularly science)' book.

What How to Invent Everything claims to be is a manual for users of a time machine (from some point in the future). Specifically it's a manual for dealing with the situation of the time machine going wrong and stranding the user in the past. At first it appears that it's going to tell you how to fix the broken time machine - but then admits this is impossible. Since you're stuck in the past, you might as well make the best of your surroundings, so the aim of the rest of the book is to give you the knowledge you need to build your own civilisation from scratch.

We start with a fun flow chart for working out just how far back in time you are…