The Science of Spin

May 1, 2023
Rotary motion may seem uninteresting, but it turns out to be worth understanding. Ennos, a professor of biological sciences and author of The Age of Wood, points out that Isaac Newton derived his laws from studying rotary motion via planetary orbits. With some modification, circular movements obey his laws, but few scientists took note because 17th-century life and technology didn't feature much spin. As both grew more complex during the following centuries, scientists struggled to explain rotational forces, making a surprising number of mistakes (which Ennos happily points out). Beginning with the Big Bang, the author emphasizes that curved motion plus gravity formed the stars and planets, "so spin really did create both the heavens and the earth." Traditionally, the invention of the wheel is considered the key landmark in the rise of civilization, although Ennos considers it overrated as a method of transportation until a much more recent development: roads. Regarding chariots, the author writes that "they would certainly have enabled wealthy aristocrats to be taken to the heart of battles without getting out of breath, but they would only have been practical on smooth, level battlefields, and so only suitable for stylized set combats." Though wheeled vehicles have proven disappointing over the centuries, the principle of a circular disk whirling around a fixed axle has been vital to nearly all human machinery since the Bronze Age. By the 19th century, it had transformed the textile and metalworking industries and revolutionized transport, starting the process of globalization that continues to this day. Ennos divides the text into topical sections: spin related to the universe, to machines, and to the human body. Although generous with charts and pictures, inevitably, most of his explanations require words, and readers with no scientific background may struggle to understand his written descriptions of high- and low-pressure turbines or how humans keep their balance. Nonetheless, there's plenty to ponder. A basic scientific concept receives long overdue attention.

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May 15, 2023
“Spin pervades all aspects of the world around us,” according to this frustrating survey. Ennos (The Age of Wood), a biology professor at the University of Hull, England, explores spin’s role in such diverse phenomena as the operation of turbine engines, the movement of yo-yos, and the orbits of planets. He explains that the gravitational pull of the moon “sweep the seas across the globe” in the opposite direction of Earth’s rotation, slowing how fast the planet spins on its axis and elongating days by 2.3 milliseconds per century. Other insights are harder to follow. The author’s account of how the invention of the flying shuttle in 1732 improved the productivity of looms will be lost on anyone who isn’t intimately familiar with the machines, and the description of how humans stay balanced by rotating their ankles expects readers to recognize precise anatomical terminology (“We relax our gastrocnemius muscles and contract our tibialis anterior muscles”). Additionally, the extended discussion of how “the hegemony of mathematics... has greatly obstructed the progress of science” by obscuring intuitive findings and repelling people “unwilling to grind their way through” complicated equations feels out of place. This will make readers’ heads spin.

July 1, 2023
Rotational energy is everywhere, at every scale of the cosmos. Its very ubiquity, notes Ennos (The Age of Wood, 2020), inclines us to ignore it. Bringing it to our attention, he spans spin's effects from Earth's rotation to technological advances to human biomechanics. Reinforced with diagrams and pictures, he explains centripetal and centrifugal forces, which, on Earth, exert profound influences that contribute to our planet's habitability, such as stabilizing its axis, generating its magnetic field, and distributing solar radiation. Turning to human applications of spin, Ennos touts the spindle, a progenitor of essential devices. Ennos does give the wheel its due, but as potter's wheels, water wheels, and turbines. Culminating with bicycles, automobiles, and aircraft, his sequence of descriptions amounts to a synopsis of the Industrial Revolution. While rotation seems inherent in technology, its presence is less apparent in the human body, but Ennos assures readers that it is key to almost any movement, from walking to throwing. In breadth of subjects and clarity of writing, Ennos' illumination of spin will fascinate readers interested in how things work and why.

COPYRIGHT(2023) Booklist, ALL RIGHTS RESERVED.