One hundred and fifty years ago in the US, the combined power of four strong horses harnessed to a plough was no more than 3 kilowatts – and more than half the entire labour force worked on farms. Today, even the smallest John Deere tractor produces 120 kilowatts and about 1.3% of workers are employed in agriculture. This means that the power rating of farm machinery has been multiplied by 40 and the rural workforce has been divided by 40 in that time – all of which is hardly a coincidence.
In transport, both modern ships and large airliners can generate up to 90 megawatts. That makes them nearly 1000 times more powerful than a typical small car and 100,000 times more powerful than a 19th-century waterwheel. And these are not even the most powerful machines out there: some steam engines that generate electricity now operate at 1000 megawatts. Setting aside the environmental impact, these enormous increases in power have brought a surfeit of food and affordable consumer items to a largely urban society, with increased access to information and mobility.
The Czech–Canadian scientist and policy maker Vaclav Smil analyses this growth of scale and power in his latest book Size: How It Explains the World. Smil is a prolific author who has already published more than 40 books on topics ranging from energy and food production to technical innovation and public policy. In this work, he revisits some of those territories, linking them together with a discussion of size, though it might be more accurate to say that the book is about proportion.
Size is not as trivial as simply a list of things that have become very big over the centuries. The physical limitations on that growth are discussed – the size of oil tankers, for example, is often expressed in deadweight tonnage (dwt), and the sizes of these ships increased steadily from about 20,000 dwt after the Second World War to about 300,000 dwt by the 1970s. There are no engineering limitations to making them more than twice that size and yet that hasn’t happened. Smil points out that this is because only a handful of deep-water ports in the world can accommodate such mega-ships, and they would be unable to pass through either the Suez or Panama canals.
On the opposite end of the size scale, Smil discusses Moore’s law, in which engineer Gordon Moore predicted in 1965 the rapid doubling of the number of components placed on a microchip. A graph of the number of transistors versus time shows that the law was maintained for many decades, but that there has been a slight levelling off since 2008. Smil links this tailing off to work by the US electrical engineer Robert Dennard, who showed that as transistors become smaller, they can be made to run faster without increasing the overall power consumption – but that this scaling effect had already begun to reach its limit by the 1990s. Future improvements may also be controlled by both the natural limits of lithography, the widely used light-printing technique, and by the enormous investments needed to develop a new manufacturing facility.
Size also goes beyond simply analyzing technology. In an attempt to appreciate the human scale in all aspects of design, Smil starts with a lengthy discussion of the giants encountered in Gulliver’s Travels. We learn that – despite Jonathan Swift’s attempts to build his fictitious world with some plausibility – a modern understanding of materials reveals that his giants would have been unable to walk upright. Worse, their mass-to-surface-area ratio would have made it very difficult for them to cool themselves down, an issue mirrored in the significantly smaller Lilliputians, who would have had to eat almost constantly to maintain their body temperature.
The scattergun nature of the topics in the book might prevent it from ultimately presenting a cohesive thesis – but it is no less enjoyable for that. The lengthy discussion of normal distributions and how they apply to issues as diverse as income distribution, as well as the heights of basketball players, is both informative and entertaining. I also enjoyed the section on the human body and perceived attractiveness, which leads to an analysis of how we are represented in paintings. That in turn takes us to a wonderful rant about the supposed ubiquity of the “golden ratio” in art and design. Smil approaches this concept with some scepticism, concluding that the so-called ratio cannot be precisely expressed as a fraction, and is therefore not even truly a ratio.
All in all, I suspect that many Physics World readers would be delighted to find this book waiting for them under the Christmas tree. Indeed, it would be perfect reading material for anyone who enjoys a mathematical analysis of the world around them, and finds themselves with a little free time.
- 2023 Penguin 304 pp £20hb
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- Source: https://physicsworld.com/a/size-matters-the-economies-of-scale-from-the-very-big-to-the-very-small/
