Book Reviews - Summer 2021

Physics for the Feeble-Minded

A crash course on our boundlessly bizarre universe

By Jethro K. Lieberman | August 9, 2021
Cezary Borysiuk (Flickr/cezaryborysiuk)
Cezary Borysiuk (Flickr/cezaryborysiuk)

Helgoland: Making Sense of the Quantum Revolution by Carlo Rovelli (Translated from the Italian by Erica Segre and Simon Carnell); Riverhead, 256 pp., $20

Carlo Rovelli’s newest book, Helgoland: Making Sense of the Quantum Revolution, is, the author writes, for readers “who are unfamiliar with quantum physics and are interested in trying to understand, as far as any of us can, what it is.” The field is not merely the stuff of academic esoterica, he assures us, but a realm of intense study about matter at its ultra-tiniest—and one that carries massive practical consequences. Not only Nobel Prizes but also financial fortunes can ride on quantum physicists’ findings, which propel technologies “from computers to nuclear power.” Indeed, as a body of knowledge, Rovelli writes, quantum theory “has never been wrong.” Sounds like something worth understanding, right?

Unfortunately, the only thing harder than doing quantum mechanics, it seems, is explaining it. Richard Feynman, the most celebrated American physicist of the second half of the 20th century, famously declared that no one understands it. Almost all who write about it, including Rovelli, begin by quoting Feynman—and then plunge recklessly ahead as if Feynman couldn’t really have meant what he said. Invariably, they end up past the end of the road, tumbling over the cliff. Initially, Rovelli seems to be driving in the same direction, but it turns out that he has his own itinerary. An internationally known Italian physicist and the author of several other unconventional books on physics, Rovelli is a guide worth following, even if he does wander off topic now and then. What could be more pleasurable than an evening or two in the company of an amiable chatterbox who likes to quote Shakespeare, reflect on the musings of contemporary philosophers, and express his amazement on encountering a two-millennia-old text of a Buddhist sage who anticipated Rovelli’s own theorizing?

Helgoland is a treeless island in the North Sea, about 30 miles off the coast of Germany, where in 1925, 23-year-old Werner Heisenberg sought escape from allergies. While there he formulated the mathematics that account for the strange orbits of electrons around the atomic nucleus. Heisenberg’s discoveries on his Helgoland sojourn are generally regarded as the foundation of quantum mechanics—the physics of the subatomic realm. The principles that have emerged are stranger than strange. An electron’s path is wholly unlike the path of a billiard ball, a bullet fired from a rifle, or a rocket ship, all of which move continuously from point to point along a given arc. Subatomic particles, by contrast, do not move continuously through space; to get from one orbit to another, the electron simply jumps without somehow traversing the distance in between (the “quantum jump”). Many other well-established oddities are elaborated at length in scores of popular books on quantum theory published in recent years.

One much-discussed peculiarity is the thought experiment of Austrian-Irish physicist Erwin Schrödinger and his cat. Place a cat in a locked chamber housing a contraption in which an atom might randomly decay. If it does, a decay particle triggers the release of a poison, killing the cat. Until it is observed, the atom is said to be in a “superposition” of both states, and the cat will be both alive and dead (or, in Rovelli’s more benevolent version, both awake and asleep). How and why should an observation cause the atom to act one way or another? A more recent discovery is the weirdness of “entanglement.” Two particles, at first mysteriously connected to each other and then separated by vast distances, will always turn up the same “color” (in quarks, a quality expressed not chromatically but mathematically) when examined—even though the colors that the particles manifest are wholly random and neither of them has any known means of communicating with the other.

It is only in relation to something else that anything can be known—and a thing can manifest itself differently to different things.

If you’re truly uninitiated, you’ll need to seek out a more detailed book to get a comprehensive picture of phenomena like these. Rovelli dallies here only briefly, for his main interest is in exploding how various camps of physicists have sought to account for quantum phenomena. For example, the “many worlds” interpretation of quantum behavior holds that the atom in Schrödinger’s chamber chooses both options: it simultaneously decays and does not decay, but “we” see only one result—say, the one in which the cat lives. Many-worlds proponents hypothesize that at the instant we make our observation, the universe splits—and that in this other universe, wholly inaccessible to “us,” an identical “we” see a dead cat.

Rovelli’s short answer to this and other bizarre takes on quantum weirdness: Nonsense! His real purpose is to posit his own theory of “relations.” He suggests that most, if not all, of quantum theory’s perplexities can be resolved by understanding that there is no ultimate essence, no Kantian Ding an sich, no existence in and of itself attributable to a particle. What we know, since we too are part of nature, is only how something manifests itself to us. It is only in relation to something else that anything can be known—and a thing can manifest itself differently to different things. Think about yourself, for example: you are known in one way to your spouse, another to your children, and so on.

This is a radical theory: the world as relation, not substance—the universe as Wonderland, where the body fades away and the Cheshire Cat becomes, in Alice’s words, the “grin without a cat.” As Rovelli writes [his italics], “there are no properties outside of interactions,” and “facts that are real with respect to an object are not necessarily so with respect to another.” The grass is green to us but not to a rock. A photon has one set of properties when measured one way, a different set when measured otherwise. Physicists, so to speak, have been barking up the wrong tree. The question ought not to be “what is the essence of this thing?” but “how does it relate to that other thing?”

And there Rovelli leaves it. Despite his promise (in my words) to fly you all the way to an island paradise, he bails out somewhere far short of the landing strip, leaving you to find your own way to ground. We can hope that in his next book, Rovelli will take on the many open questions that will doubtless occur to you when you finish this one. Helgoland is the headline. The story of Rovelli’s revelation remains, in its fullness, to be written.

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