Between the lines

Wildlife biology for physicists

In engineering terms, animals are a mature technology. They are well adapted for the ecological niches they fill and, for the most part, they do a rather good job of surviving in an unforgiving world. But what really makes them tick? This is the central question addressed in Engineering Animals, a remarkable book by two authors, Mark Denny and Alan McFadzean, who trained as physicists before pursuing careers as engineers, and who have spent the past two years immersing themselves in biology. Appropriately, the book begins with a thermodynamics-inspired discussion of how animals use energy. Readers familiar with the second law will probably not be surprised to learn that the “food chain” linking prey species and predators is hugely inefficient, with each prey organism providing only 10% of its energy to whatever eats it. This simple observation, however, has some interesting consequences. Among other things, it underlies certain patterns in animal behaviour, including the fact that small carnivores (such as cats) eat smaller animals (mice), whereas large carnivores (such as lions) eat things that are roughly their own size (wildebeest). Energy considerations also feed into rules about animal size and shape, including “Allen’s rule” that animals living in cold climates are rounder than those in warm ones, because organisms with high volume-to-surface-area ratios retain body heat better. Allen’s rule was articulated in the 19th century, but the book also ventures into current debates in biology, such as arguments about why giraffes do not suffer aneurysms when they lower their heads to drink, whether systems that distribute resources around an animal’s body are fractal-like, or why migrating birds fly in a V-shape (simple energy savings do not quite cover it, apparently). Written in a light and engaging style, but with plenty of references and footnotes, Engineering Animals is perfect for physicists who, like your reviewer, abandoned formal studies in biology at an early age and have always wondered what they missed.

• 2011 Harvard University Press £25.95/$35.00hb 400pp

How humans work

From the physics of animals in general, we now move to the physics of one particular animal: humans. Unlike the previous book, Physics of the Human Body is intended for medical students and professionals rather than physicists. But although most of the physics concepts in the book are familiar, a great many of the examples used to illustrate them are not. The section on forces and torques, for instance, eschews abstract rods and levers in favour of the human musculoskeletal structure. This leads nicely into a discussion about how much weight an average person can lift without injuring themselves – a topic that is certainly of practical interest to many experimental physicists, even if the physics of it is not particularly interesting. This pattern of introducing a physics concept, then concentrating on its medical applications, continues through most of the book. The coverage of pressure, for example, places a strong emphasis on how pressure-related ideas play out in the human circulatory system, as well as in organs such as the lungs, eye, brain and bladder. The exception to the rule of “physics first, medicine later” occurs in the final chapter, where author Richard McCall instead uses a medical concept – drug delivery and absorption – to illustrate how physicists model complex problems. McCall has obviously worked hard to make the physics interesting and relevant for medically minded readers, and as a physics lecturer at the St Louis College of Pharmacy in Missouri, US, he has had plenty of opportunities to field-test this approach. Anyone who teaches similar students – or who simply wants to vary the examples they use in introductory physics courses – should look at his book.

• 2010 Johns Hopkins University Press £23.50/$45.00pb 312pp

The physics of va-va-vroom

Fast Car Physics is not a book for automotive novices. If you do not know the difference between a dyno torque curve and a g-g diagram, you will find some of its chapters hard-going. If you’ve never heard of either, you had best steer clear altogether. Fortunately for the book’s publishers, the overlap region in a Venn diagram of “people who like physics” and “people who like cars” is large. Moreover, readers who enjoy debating the relative merits of the Subaru WRX STi and the Nissan 350Z – and then plotting graphs to prove their points – will definitely find a kindred spirit in author Chuck Edmondson. A physicist at the US Naval Academy, Edmondson’s other passion is car racing, and he has extensive experience in combining the two: not only has he taught a course in automotive physics, he has also raced in an amateur team with his son and daughter. His book is pretty comprehensive, taking in everything from the factors that restrict 0 to 60 mph times to the materials science of Formula 1 tyres, plus a meaty final chapter on “green racing”. As Edmondson points out, oil shortages and growing concerns about the environment have not reduced interest in motor sports. The challenge for a green-minded homo automotives, then, is to find a way of combining speed and environmental friendliness. None of the possible solutions explored in this chapter (electric cars, hybrids, alternative fuels, etc) seem to hold all the answers, but it is encouraging to know that some racers are at least thinking about the problem.

• 2011 Johns Hopkins University Press £15.50/$29.95sb 248pp