Polkinghorne’s preface opens with this statement: “The discovery of modern quantum theory in the mid-1920s brought about the greatest revision in our thinking about the nature of the physical world since the days of Isaac Newton. What had been considered to be the arena of clear and determinate process was found to be, at its subatomic roots, cloudy and fitful in its behavior. Compared with this revolutionary change, the great discoveries of special and general relativity seem not much more than interesting variations on classical themes.”
For Polkinghorne, the quantum world is more than just small (where at the Planck scale “a row of dots looks like a solid line”). At the nucleus level, subatomic particles behave differently than in the deterministic universe of Newton and Einstein, where linear cause and effect relationships are clear. Rather, in the quantum world, there’s Heisenberg’s uncertainty and its “epistemological principle of ignorance” regarding position and momentum that lies at the core of reality. Polkinghorne writes of quantum logic that, as opposed to an Aristotelian true/false dynamic, includes a “maybe,” where what can be said about electrons can only be stated in probabilistic terms. In quantum mechanics, a particle can jump through barriers “provided it reaches the other side quickly enough to pay back energy within the necessary time limit. It is as if the particle had tunneled through the hill.” Per Feynman, we have virtual particles without physical mass that exist as intermediate particles, different than what exists initially or at the end of a process. Polkinghorne states that even Newtonian mechanisms exhibit quantum properties – when very small disturbances make “their future behavior beyond our power to predict accurately. These chaotic systems (as they are called) soon come to be sensitive to detail at the level of Heisenberg uncertainty or below.”
Polkinghorne writes that within a vacuum, the lowest energy state, there is still “an infinite collection of harmonious oscillation” with specific frequencies. Even in empty space, particles move (there’s “zero point motion”). A vacuum “is a humming hive of activity,” he says. “Fluctuations continually take place, in the course of which transient ‘particles’ appear and disappear. A quantum vacuum is more like a plenum than like empty space.” Finally, at the heart of the quantum world, Polkinghorne writes that there is a “deep-seated relationality” or correlation between two events where “entities that have interacted with each other remain mutually entangled, however far they may eventually separate spatially.” This, for Polkinghorne, means that at the smallest levels of matter and energy there’s more than pure atomism that is involved.
Polkinghorne closes with a chapter on “lessons and meanings.” His quantum world counters positivism with its self-imposed limitation on using only observational data. For him, the quantum world of electrons and photons, quarks and gluons are real, operating at very small scales. They don’t overturn classical theory but they make “intelligible great swathes of physical experience that otherwise would be opaque to us.” The quantum world is a relational reality that transcends atomism. And, he advises, the quantum world is anything but arbitrary. In fact, he argues that it accounts for the fundamental stability of atoms. While probabilistic and not deterministic, and while it operates in a “wraithlike” fashion, the quantum world has order and stability. And “random subatomic uncertainty is very different, indeed, from the exercise of the free will of an agent,” he says for those who attempt to use the meanings of quantum physics this way.
Polkinghorne draws heavily on the work of Dirac. He makes several references to “wave-like” and “particle-like,” but the reader is left with the impression of a third subatomic property that is neither a wave nor particle. Here and there, the author leaves his lay readers behind who, lacking in the requisite background, bump into some fairly thick stuff. Yet, this book, while short, is a lucid description of a complex subject.