Everybody has a weakness. Superman’s is kryptonite. The Wicked Witch of the West’s is water. Mine is physics. My body may be subject to its laws (i.e., I accelerate when I run, barely), but my brain has always struggled to understand it, from velocity and momentum through relativity and string theory. Schrödinger’s cat made no sense to me — why would Nature care if anyone is observing the cat?
So it was with great joy that I discovered and consumed Carlo Rovelli’s latest offering, Helgoland: Making Sense of the Quantum Revolution (Riverhead Books). A bit less poetic but no less elegant than his bestseller Seven Brief Lessons on Physics, Helgoland hooked me so hard I read the entire book in one sitting. And then twice more.
Rovelli offers a tour through the shaky and convoluted terrain of quantum phenomena, which he argues are fundamentally “relational.” Nature, he writes, is not a collection of solitary, permanent objects and other substances; rather, Nature is fundamentally made of relations between quantities. A quantity conveys information (has meaning) only in relation to another quantity, never by itself.
Helgoland delivers its first gut punch early on, when Rovelli frames a fundamental question for quantum physics: How can we understand the quantity of energy that we observe as “an electron, its movement and other properties”? Strangely, its location can be predicted only for the moments we observe it. He writes, to my immense gratitude, “What does Nature care whether there is anyone to observe or not?” This paradox of quantum superposition (which also underlies Schrödinger’s cat) is resolved, we learn, by the realization that “an observer” need not be a human observer. The observer can also be another quantity. An electron’s position or velocity exists only relative to some other quantity of energy. When an electron is not interacting with anything, it has no physical properties. Rovelli explains other quantum mysteries via the same scientific punchline: A quantity has no inherent meaning — it is only meaningful in relation to something else.
A second revelation in the book was even more personal. My research program as a neuroscientist and psychological scientist — constructionism — is based on the idea that physical signals, like the raise of an eyebrow, a rise in blood pressure, or an increase of cortisol, have no inherent psychological meaning. These signals (a.k.a., quantities) are meaningful only in relation to one another and to other signals, including the electrical and chemical signals in a brain. Your brain doesn’t observe and detect — it constructs thoughts, feelings, perceptions, and other mental events as it makes meaning from sense data. This meaning-making process is a whole brain event; it is not localized to particular neurons. The meaning of any firing neuron is always in relation to other physical signals, including other neural firing. Constructionism is fundamentally a relational perspective, and so, ironically, I found a kindred scientific spirit in a book about a topic that I have struggled my entire adult life to understand.
Physics, writes Rovelli, “is always a first-person description of reality,” not a “description of things in the third person.” Later, he continues, “There is no way of seeing reality that is not dependent on a perspective — no point of view that is absolute and universal.” The same is true for every other science. And, of course, for book choices.
Lisa Feldman Barrett is a professor of psychology at Northeastern University and the author of How Emotions Are Made: The Secret Life of the Brain and Seven and a Half Lessons About the Brain.