A Comparison of Three Books Written by Physicists About Physics
Helgoland: Making Sense of the Quantum Revolution. Carlo Rovelli. Riverhead Books. NY. 2021.
Fundamentals: Ten Keys to Reality. Frank Wilczek. Penguin Press. NY. 2021.
Something Deeply Hidden: Quantum Worlds and The Emergence of Spacetime. Sean Carroll. Dutton. NY. 2019.
The Characters
Rovelli’s Helgoland:
Observables, Probability, Granularity
Einstein, Heisenberg, Bohr, Schrodinger
Observables hearken to an age-old debate in philosophy/science about how we humans gain knowledge: Empirically or Ideally. Through observations or through ideas? Heisenberg sends quantum mechanics down the road of looking only at observables and attempting to describe them and predict them.
Probability continues that debate with its insistence that at the quantum level we cannot know specific facts with certainty, only with a spectrum of probabilities. When presented with Heisenberg’s and Schrodinger’s math of probability, Einstein famously said, “God does not play dice,” meaning “The laws of Nature should be predictive.”
Granularity is what quantum means. Quantum physics is the study of the granularity of physical life in the electromagnetic spectrum (light has packets of energy we call photons), in atoms (electrons move in discreet leaps), and for atoms (atoms can only spin in discreet speeds, not continuously).
Bohr philosophically guided quantum physics towards observation over explanation. His retort to Einstein was “Stop telling God what to do.”
Wilczek’s Fundamentals:
10 keys to reality, culminating in complementarity
An infant becoming an adult, scientists
The 10 keys include two broad themes: What There Is and Beginnings & Ends.
What There Is: Plenty of space and time, with very few ingredients and laws, and with plenty of matter and energy.
Beginnings & Ends: emergence of the universe and the consequent complexity; we have more ways to learn how to see the world, which will help us solve the current mysteries we don’t have answers to; and finally, complementarity.
The infant: a child, any child, symbolized by his own granddaughter. She is newly born, searching reality to learn her place in it by separating internal from external reality. If she grows up with a scientific mindset, she will still need to be open to being born again as an adult, with the presentation of new data, and fuse—or at least blur the line between—internal and external realities.
Scientists and their instruments across time and culture have all contributed to the amazing knowledge we now have that he has delineated into the 10 keys to reality.
Carroll’s Something Deeply Hidden:
Quantum mechanics itself, measurement, Many-Worlds theory
Einstein, Bohr, and Everett
Classical or Mechanical Physics, as described by Isaac Newton looks at position and velocity of objects and the forces acting upon them. Even Einstein’s relativity theory, “which was world-transforming in its own way, is a variety of classical mechanics rather than a replacement for it.”
Classical physics doesn’t have a measurement problem; quantum mechanics does: “What we see when we look at the world seems to be fundamentally different from what actually is.” For example, classical physics has a two-rule recipe for experiments; quantum has a comparable two-rules, but then adds another three, all relating to measurement.
He devotes a long paragraph to a list of questions about what constitutes measurement and how to define it.
“The fact that the quantum recipe provides us with probabilities rather than certainties might be annoying, but we could learn to live with it. What bugs us, or should, is our lack of understanding about what is actually happening.”
Einstein and Bohr engaged in a series of discussions over a number of years debating this measurement problem in quantum physics. Einstein never accepted Bohr’s philosophical solution, but Bohr’s approach has come to dominate the science of physics ever since.
But others have attempted to go back to the beginnings of physics and try to understand better just what is happening in quantum experiments. Everett was one such scientist, who proposed the Many-Worlds theory.
Next, the authors duke it out: The Conflict
The Conflict
Some further background:
Classical physics = mechanical physics = Newtonian theory of gravity.
Quantum physics = quantum mechanics = quantum theory.
When Einstein was developing his theories, he was working as a classical physicist. His discoveries, along with the discoveries of many other physicists doing research, experiments, and theorizing over the course of roughly 27 years (1900 – 1927), created the entirely new science of quantum physics.
Quantum means granularity. Quantum physics is the study of the granularity of physical life in the electromagnetic spectrum (light has packets of energy we call photons), inside atoms (electrons seem to move in discreet leaps), and for atoms (atoms seem to only spin in discreet speeds, not continuously).
To further define the conflict, let’s distill down the afore-mentioned list of characters to three main ones, for they play pivotal roles as main characters in two of the books and starring roles in the conclusion of the third book: Heisenberg, the uncertainty principle (or complementarity), and the act of measurement.
Heisenberg first developed the math to help account for experimental results in the first quarter of the 1900’s. He realized that at the atomic level—as opposed to our macro-level of living—we cannot measure both speed and position of a single atom or its parts at the same time, like you can, say, a baseball’s.
Heisenberg called this the uncertainty principle, also known as complementarity: there can be two opposing but complementary views of the same object.
Related to complementarity is superposition, when two contradictory properties are present together. In a sense, Rovelli says, an electron can be in two places at the same time, without a trajectory between the two. But he also clarifies that no one has actually seen this, only the consequences of this superposition. We see the interference, not the actual superposition. And when we take a measurement in a certain experiment, the interference disappears. This is the confounding aspect that Carroll is trying to understand.
Thus, the very act of measuring something…well, there’s the rub. That act of measuring an object at the quantum level is the conflict and/or the source of inspiration that all three physicists try to address.
It betrays the very foundation of all we humans take for granted: how do we know anything? How they answer this question of measurement is how their three stories diverge…or converge.
Rovelli focuses on the concept of observables; “…the strange idea of ‘limiting yourself to only what’s observable’…has never been wrong.” If that’s not astonishing enough, the following is emblematic of the opinions of all three authors: “…[quantum] is the only fundamental theory about the world that until now has never been found wrong—and whose limits we still do not know.” Not wrong, that is, in experiments and in applications; it still doesn’t mean anyone understands how it works.
Rovelli poses several questions such as: Why can we not describe what an electron is doing when we are not observing it, and “What does Nature care whether there is anyone to observe or not?” In his storytelling of the history of quantum, the debate over observables coalesces into the solution of probability, in which an electron has a range of probable positions and speeds, but only one position or only one speed can be observed the moment the experiment is measured by humans or our instruments.
“But what does a particle care if we are observing it or not? The most effective and powerful scientific theory is an enigma.” That’s the very concept that Carroll complains about and encourages us to not accept without question; to him, science is about clarifying, not muddying.
Rovelli discusses other interpretations of this measurement enigma before giving his own solution. He writes a scant three pages describing the interpretation that Carroll takes a whole book to explain; Carroll doesn’t even mention Rovelli’s ‘relational’ interpretation.
Rovelli’s take on the Many-Worlds theory: “Many ‘interpretations’ of quantum mechanics … seem to me to be efforts to squeeze the discoveries of quantum physics into the canons of metaphysical prejudice … Does it disturb us to see a component of a quantum superposition disappear? Then let’s introduce a parallel universe where this component can go and hide … I believe we need to adapt our philosophy to our science, not our science to our philosophy.”
For Rovelli, taking a measurement is not a big deal. The weather doesn’t change the moment we read the barometer, we merely learn what the weather is up to and can infer where it is headed next. The real conflict is in the questions: What is an observation and What is an observer?
Wilczek waits until the 10th chapter to describe the concept that both Rovelli and Carroll begin their books discussing. Wilczek takes one of the first major concepts that began quantum physics as his book’s ending point and a springboard into a new way of expanding our general understanding, both philosophically and spiritually.
Wilczek is a bit of an enigma to me. Very focused on the facts of science, he then can launch seamlessly into a religious response in his thinking and behavior. His last chapter focuses first on very practical considerations regarding the issue of measurement; the second half is titled “Complementarity as Wisdom.”
He doesn’t see a measurement problem, he sees a mathematical construct: “In quantum theory, as presently understood, complementarity is a mathematical fact, not just an airy assertion.” And further, “If it were possible to measure both position and velocity simultaneously, then we would need a new mathematical theory….” It would no longer be the science of quantum but some other science.
His refreshing clarity of thought comes through: “…this conflict—this complementarity—reflects two key points. The first key point is that to measure something’s properties, you must interact with it” …and… “precise measurements require strong interactions.” [Wilczek’s emphasis] Or put another way later, “…observation is an active process and observation is invasive … .” Then a bit later, a quick dab into spirituality, “By observing the world, we participate in making it.”
Back to some clarity, he discusses the facts of describing different levels of reality differently. He uses a hot air balloon as an example. While theoretically it might be possible and even satisfying to ascertain the exact position and velocity of every gas atom in the balloon in order to describe and then predict its behavior, it is extremely impractical to collect, store, and calculate all that data. And yet an experienced balloonist operates her balloon just fine. How? By using the macro concepts of density, pressure, and temperature.
Wilczek describes and solves the measurement problem in the same paragraphs. It’s not a problem; it is a fact and source of inspiration.
Carroll’s whole book is an attempt to answer the measurement problem. His solution is the Many-Worlds theory, as first formulated by Everett. Of the three authors, he is the most explicit about and insistent that there is a conflict, and that it stems from interpreting the very act of measuring in quantum experiments.
Carroll explains Everett’s approach in the following way: If we want to talk about the universe in quantum terms, we have to acknowledge that the whole universe is quantum, that there is no “separate classical realm.” That means even the observer and the measuring devices are quantum. There is, in fact, only a single quantum state, the wave function of the universe.
Measurement is when one part of the universe interacts with another part of the universe. “We don’t need to invoke any special rules for measurement at all; things bump into each other all the time.” This reminds me of Rovelli’s ‘relational interpretation,’ but Carroll goes on a whole other pathway:
When a device measures the electron as ‘spin-up,’ the device and electron have evolved into a superposition with each other; the other possible outcome—‘spin-down’—also exists!
It simply branched into a separate world.
That universal wave function branches into multiple worlds when two entities interact; all possible results have occurred, they’re just seen in different worlds.
Carroll admits that how often branching occurs is yet unknown, “but we do know there’s a lot of branching going on…In a typical human body, about 5,000 atoms undergo radioactive decay every second. If every decay branches the wave function in two, that’s 25000 new branches every second. It’s a lot.”
Carroll states that with the Many-Worlds formulation of quantum mechanics there is “nothing special about what constitutes ‘a measurement’ or ‘an observer.’ Consciousness has nothing to do with it. “The ‘observer’ could be an earthworm, a microscope, or a rock.”
“The price we pay for such powerful and simple unification of quantum dynamics is a large number of separate worlds.”
Next: The Rapture and The Wrap Up
Other posts that mention this review: Gastrophysics, Essay on Perception,