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From ink to oceans, a materials scientist explores the properties of fluids encountered on a transatlantic flight

Liquid Rules: The Delightful and Dangerous Substances That Flow Through Our Lives

Mark Miodownik
Houghton Mifflin Harcourt
256 pp.
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I read Mark Miodownik’s Liquid Rules on a flight between Germany and South Carolina—an appropriate setting because the book is organized around another transatlantic plane trip. Telling the story of liquids during air travel may seem counterintuitive, but as Miodownik carefully shows, one encounters many diverse and interesting liquids during flight.

Liquid Rules is Miodownik’s second popular science book. The first, Stuff Matters, illuminates the inner workings of solids. Written in a conversational tone, with all of the charm that genuine enthusiasm for the subject brings, each of the 12 chapters in Liquid Rules is devoted to a particular substance, from ink to tea and from clouds to oceans. Miodownik delves into the history of each liquid, including its discovery, manufacture, uses, and at times even its philosophy, mythology, and physics. He draws on his experience as an engineer and materials scientist and his skills as a science writer to make complex concepts accessible and, better still, intuitive.

The book begins on the atomic scale, describing how molecular geometry influences the physical properties of a liquid—a theme that will reoccur. By beginning with the most basic structures and properties of liquids, Miodownik emphasizes how the microscopic influences the macroscopic, bridging the gap between the unseen and the everyday. He describes, for example, how kerosene pours like water, whereas olive oil is viscous and gloopy, but reveals that both are composed of simple hydrocarbons. The unseen reason for this difference is that the atoms in kerosene form long carbon chains akin to “spaghetti” strands, whereas the chains in olive oil are “branched and twirled”; kerosene molecules slide past each other easily, but the olive oil chains get tangled up.

In the next chapter, Miodownik discusses alcohols, with an emphasis on the perennial favorite: ethanol. Many readers will be familiar with the intoxicating effects of ethanol but may never have considered how the hydrophobic region of ethanol influences intoxication or how the astringency of wines makes them an ideal palate cleanser during meals.

Miodownik’s discussion of stickiness and glues is particularly interesting, with paints making a surprise appearance. Once he points it out, you can’t help but notice that paint is, after all, just a colored glue. You might also be surprised, as I was, to learn that many airplanes are glued together.

Liquid Rules also contains sobering passages about global warming and sustainability. As sea levels rise, coastal regions will flood, but counterintuitively, ice melting in Greenland and Antarctica could also result in postglacial rebound, allowing these landmasses to become lighter and “bob up” out of the fluid mantle, Miodownik reveals. This increase in landmass height could potentially offset some flooding.

Although the implications of rising sea levels are frightening, the book’s overall message is lighthearted and optimistic, tempering more serious passages with discussions of new and innovative technologies, such as roads that heal their own cracks with sunflower oil and 3D-printed prosthetics.

Liquid Rules answered questions I never thought to ask. What makes something “sticky,” for example? And why is saliva so stringy? Where does the “soap” in “soap opera” come from? I especially enjoyed Miodownik’s careful consideration of everyday, often overlooked technologies and came away with a new appreciation for the liquid-based engineering involved in candle-making and the non-Newtonian fluid dynamics of a ballpoint pen.

Each chapter of Liquid Rules switches focus and scale, jumping, for example, from a glass of wine to the ocean itself and then later back to a cup of tea. A straight read-through left me with a bit of metaphorical whiplash. The book might be better swallowed in short bursts, consumed chapter by chapter, rather than in one extended read.

There are also two distinct narrative voices: a personable, enthusiastic narrator whose anecdotes add charm to the discussion and a more authoritarian voice that occasionally stretches to make connections between disparate concepts. At times, the switch between these two was not as smooth as it could have been.

Despite this, Liquid Rules is both entertaining and informative, which makes it a useful tool in the fight to promote scientific literacy. At a time when technology, science, and public policy are often at odds, Miodownik adds to our understanding of the physical world with humor and sound science.

About the author

The reviewer is a biochemist based in Munich, Germany.