Book Review: What Is Real? The Unfinished Quest for the Meaning of Quantum Physics, Adam Becker
A basic thought experiment from the early days of quantum theory has meandered into the mainstream. As usually happens with these sorts of transfers into the common understanding, it is only partially understood and that part is more often misunderstood. A cat is trapped in a box. In the full version of the thought experiment, along with the cat is a Rube Goldberg device comprised of uranium, a geiger counter attached to a hammer, and a vial of cyanide resting under the head of the hammer. The experiment (fortunately for cat lovers, only transacted in the minds of physicists and other inquirers) relies on the fact that in time the uranium will release radiation, triggering the geiger counter, releasing the hammer, breaking the vial and killing the cat. However, at any given moment, the radiation may OR may not release. Therefore, the hypothetical cat may actually be either alive or dead–we will not know until we open the box. In a closed and unobserved system, the concept concludes, the cat is both alive and dead since both possibilities are equally probable. It is the observing that defines the cat’s untimely demise or it’s fortuitous release.
The full version of Erwin Schrodinger’s thought experiment opens the 2018 book What Is Real? Adam Becker provides a rousing history of quantum theory, looking at the personalities, mathematics, and experiments that have shaped this central theory of physics over the last century. With outsized characters like Schrodinger, Werner Heisenberg, Albert Einstein, and especially Neils Bohr creating the foundations of the theory, it is little wonder that quantum physics moved to the center of our understanding of how atoms and electrons work. The math is sound: quantum calculations are at the heart of literally thousands of innovations in technology and have predicted many of the discoveries in physics that excited both scientists and laypersons alike throughout the twentieth century.
What even many scientists fail to fully understand, though, is that there is still no complete understanding of HOW and WHY quantum mechanics works. The math works. Find a quantum problem, enter the variables, and out pops the solution. The temptation then is to follow the advice of one key physicist: shut up and calculate. (In fairness, that scientist himself rejects his own advice.) But many scientists are unwilling to accept this practical solution. They want to know WHY it works. Certain principles of quantum mechanics seem to violate Einstein’s Theory of Relativity by creating changes simultaneously in two bodies separated by great distance. If communication faster than light is impossible (Relativity says it is), then this can’t be. Other facets of quantum theory show behavior of objects changing based on observation (e.g. Schrodinger’s poor cat being both alive and dead until it is seen as being definitively one or the other). But exactly why does the behavior change upon observation? And what qualifies as “observation”? Were these particles behaving one way throughout time, waiting for someone with a PhD to come along? Or does behavior change if a cat, or a mouse, or a flea, were to observe it? These are the kinds of questions that scientists have been wrestling with since the beginning of quantum theory, and many of those questions remain unanswerable to date.
Various critiques of the traditional understanding of quantum physics have been offered, some gaining more traction than others. One which has become very popular in science fiction (if less so among actual scientists) is the multiple worlds theory, which holds that any action which has multiple potential outcomes has actually resulted in each of those potential outcomes, with the universe dividing again and again and again to accommodate those outcomes. In one universe the poor cat has died, in another it lives. That is again oversimplifying the argument to the point of devastating it, but the beauty of the multiple worlds theory is again that the math works. (I am taking Becker’s word for this–my math skills are not elite on any possible world.)
To a degree, though, this is both the agony and the ecstacy of quantum theory: it does a magnificent job of predicting what will happen, but we still cannot understand why it actually does this. Parts of quantum theory (especially as it relates to waves, electrons, and events occurring at a sub-atomic level) can be demonstrated as factually true. But why it works at the level of electrons and yet fails to predict the behavior of molecules as effectively is something scientists cannot yet answer.
Becker’s story is about the people who have looked and are looking for those answers. It goes beyond “just” the science and looks at the scientists as people and at the times they lived in. Becker deals squarely with the Nazi sympathies and collaboration of Heisenberg and other German scientists during WWII (and the disruption to European science in particular by the anti-Semitic prejudice and actions of the Nazis). He follows the path of one scientist exiled from the US during the “Red Scare” of the 1950s and how that affected the trajectory of quantum theory during a time when no one wanted to be accused of being “communist.” He traces the outsized influence of Neils Bohr, acknowledging his brilliance while noting that his influence was in part due to his amazing personality and warmth. Einstein’s critiques of quantum theory failed to gain as much traction, in part, due to Einstein’s more standoffish personality–Bohr won over critics with warmth and genuine affection when sometimes his math and writing were less precise.
The key question is the title of the book: What Is Real? In one sense, quantum theory answers this question. It works, therefore it is real. It predicts actual behavior of electrons. It leads to the creation of repeatable experiments. It results in actual inventions that have real world applications. That’s as real as you can get. But in another sense, the question remains unanswered. Can quantum theory predict the behavior of things larger than an electron? Can it be unified with the Theory of Relativity–which also works–in a way that explains the universe compellingly? If it is real, is it only real on a scale that we will never effectively observe? The search for those answers continues.
I loved the book–although I admit that I am not smart enough to fully understand it. Becker writes well. His stories about the people who shaped the theory are fascinating and fun. I will never be able to explain quantum physics or understand it nearly as well as my children do. But I appreciate the fact that scientists are people who struggle with bills and careers and politics as well as math and observation and theory. Becker’s book is about science and it is about the people who do science. That makes it a fascinating read.