During a physics class I took in college, the professor introduced the unit on thermodynamics with a quote from Albert Einstein, who said that it is “the only physical theory of universal content which I am convinced . . . will never be overthrown.” I was suitably impressed. Yet within about 10 minutes my enthusiasm flagged. Sure, the field might be eternal, but even Einstein’s imprimatur couldn’t glamorize the grubby details of heat exchange and energy conservation.
Such is the fate of thermodynamics. It’s arguably the most successful scientific theory in history, sweeping and precise and revolutionary all at once. And virtually no one cares. “Einstein’s Fridge: How the Difference Between Hot and Cold Explains the Universe,” a wide-ranging book by the British documentary filmmaker Paul Sen, sets out to rectify that situation. Mr. Sen knows the challenge that awaits him. In the book’s very first sentence, he laments that “thermodynamics is a dreadful name.” It implies a bland focus on heat flow and, to me at least, conjures up images of Victorians in stuffy suits tinkering with steam engines. It’s a far cry from the romance of relativity or the enigmatic koans of quantum mechanics. Mr. Sen nevertheless makes a strong case that thermodynamics is every bit as lively as those other fields—and vastly more useful for understanding what makes the universe tick. The history of thermodynamics flips the relationship between science and technology on its head. Nowadays, scientists emphasize the primacy of fundamental research. Only after you understand the basic science, they argue, can you hope to apply it outside the lab. Not so with thermodynamics. In case after case—steam engines, refrigerators, computer circuits—engineers and dedicated tinkerers began making impressive progress in the field before they had any real understanding of the underlying science. This topsy-turvy history might explain, in part, the field’s inability to charm the public. We love bold leaps that open up new vistas of thought; sweeping scientific breakthroughs are sexy. Tinkering isn’t. And even after scientists jumped into thermodynamics, their understanding came fitfully—a handful of men and women advancing piecemeal over a century. Contrast that to the theory of relativity and its lone, dreamy hero in Einstein. Or quantum mechanics, which had the feverish air of a revolution in the 1920s. However important, the history of thermodynamics is messy. Photo: WSJ In Mr. Sen’s hands, that history is still pretty lively. Two main characters in “Einstein’s Fridge” committed suicide (Ludwig Boltzmann and Alan Turing); another (Emmy Noether) labored for years without pay or recognition, only to end up on the cover of Time magazine. There’s also the book’s titular home appliance. Starting in the 1920s Einstein collaborated on building several different models of refrigerators, which seems like a bizarre aberration. Didn’t he have better things to do? But Einstein adored thermodynamics, so the project was a natural fit for him. Much of Einstein’s work, in fact, was built on 19th-century thermodynamics. Even E=mc2, in showing the equivalence of mass and energy, simply extended the idea of energy conservation. Beyond the anecdotes, Mr. Sen also succeeds in showing thermodynamics’ wide application—capable of providing insights into nearly every other scientific field. In the 1800s biologists used it to show that the energy that animals expend comes only from the calories they ingest. This disproved the old “vitalist” notion that living matter was infused with some sort of mystical energy that differentiated it from nonliving matter. Meanwhile, the thermodynamic concept of entropy explains everything from why chemical reactions take place to why time flows in only one direction. (At one point, Mr. Sen describes a refrigerator as “a device inside which time slows down,” largely by stalling the march of entropy.) Modern science and technology owe even more to thermodynamics. In the mid-20th century, Claude Shannon teased out the deep links between thermodynamics and information theory, paving the way for a telecommunications revolution. Toward the end of his book, Mr. Sen also describes some mind-bending cosmological theories about the connections between entropy, black holes and whether our seemingly three-dimensional universe is really just a 2-D hologram. My main quibble with “Einstein’s Fridge” is Mr. Sen’s tendency to veer into analogies. A judicious few can be helpful, and the author offers some dandies. I especially enjoyed the one about the rowdy pub patrons invading a quiet library, to illustrate a change in entropy. Other analogies, though, are rather baroque. To show what happens when a mass falls into a black hole, Mr. Sen sketches out a scenario involving some superintelligent fish who swim around a shallow but infinitely wide ocean. They’re blind and can’t feel the water on their skin, but they have incredible hearing, and they’re being pulled down a drain (in the ocean) while they ping each other with sonar. One fish is also somehow wearing a watch. I could see where he was going with all this, but the simpler the analogy the better: When multiple such analogies started piling up, it gets a bit dizzying. Overall, though, Mr. Sen makes a compelling case for how vital thermodynamics is; I now regret not heeding my professor back in college. But perhaps I shouldn’t be so hard on myself: Even legendary scientists tend to underestimate the field. In the early days of quantum mechanics, the physicist Niels Bohr wanted to jettison the first law of thermodynamics—which states that energy is always conserved—to salvage a pet theory of his. Half a century later, Stephen Hawking insisted that the second law of thermodynamics—which says that the entropy of the universe always increases—didn’t apply to black holes. Eventually, both men conceded that they were wrong. The lesson is simple: Thermodynamics does not bow to other fields; other fields bow to it. Mr. Kean is the author of several books. His latest, “The Icepick Surgeon: Murder, Fraud, Sabotage, Piracy, and Other Dastardly Deeds Perpetrated in the Name of Science,” will be published in July.