THE SCIENCE OF SPIN

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.