Quantum Physics and Materialism

December 19, 2017

This positive summary of Quantum Idealism by Inspiring Philosophy is fascinating, but I am still unconvinced. I would like to call myself a "neo-realist" instead of an idealist, and here's my lengthy critique as to why.


Until the rise of the new physics, most scientists were realists. They believed that the world exists objectively, independently of our perception of it. I am talking about ontological realism (what sort of world exists) not epistemological realism (whether theories can be true). Even today, the majority of practicing physicists are unreflective realists, in the sense that they believe they are investigating the way things really are, and they don't stop to think how they would support that assumption philosophically. Yet quantum mechanics has seriously shaken that implicit belief. In response, several physicists have sought to develop updated versions of realism.


Neils Bohr counseled agnosticism about the ontological status of the quantum world, but realists disagree. They believe the quantum world really exists, and most of them would add that it is populated by ordinary objects. After all, what do we actually see in quantum experiments? Patterns of tiny black marks on photographic screens. Curly tracks in cloud chambers. Pointer readings. These are clearly real, ordinary objects. Must we account for them by resorting to bizarre, unordinary interpretations? Isn't it more natural to think the electrons that made the marks are likewise ordinary objects, with normal position and momentum attributes?


Historically, most of the founders of quantum mechanics were realists: Einstein, Max Planck, Louis de Broglie, and Erwin Schrödinger. When Schrödinger saw the anti-realist direction in which quantum mechanics was heading, he said "I don’t like it, and I’m sorry I ever had anything to do with it.” Most realists believe the quantum world is built in the old-fashioned classical manner, out of particles and fields, with quantum waves as a type of force field, like magnetic waves. Yet in order to account for the puzzling features of the quantum world, realist interpretations have taken some interesting turns, so that we might more accurately call them "neo-realists".


David Bohm, for example, has developed a neo-realist theory in which particles have a definite position and momentum, and waves are separate and real entities, not merely mathematical constructs. In Bohm's theory, each particle travels along its own wave (he calls it a pilot-wave) like a cork bobbing on the sea. However, to make this ordinary-object model of quantum reality work, the pilot-wave has to behave in unusual ways. It spreads out as an invisible field, probing the environment and changing whenever the environment changes, simultaneously causing the particle to alter its behavior accordingly. This explains why an electron seems to "know" whether there are two slits (in which case it creates an interference pattern) or a single slit (in which case it acts as a barrage of particles). The particle's corresponding wave precedes it like a field and sends the information back.


Obviously this theory involves some pretty interesting concepts:


1. In order to take into account all possible influences, the pilot wave has to connect in principle with every other particle in the universe, somewhat as gravity does (except that, unlike gravity, the wave does not weaken with distance).


2. It has to communicate information about the world instantaneously to the particle, enabling it to switch its attributes accordingly. This violates Einstein's dictum that nothing can travel faster than the speed of light. As a result, Bohm regards his theory as merely a starting point in constructing an ordinary-reality model of quantum reality.


John Bell pursued Bohm's theory further, arguing that the famous Einstein-Podolsky-Rosen paradox (where paired electrons influence each other even when separated by vast distances, and it appeared to happen instantaneously, thus the underlying world is a seamless whole) supports the pilot-wave concept. The experiment gives evidence that quantum objects can indeed influence one another in mysterious ways not restricted by distance across space, thus not affected by locality. Bell calls his interpretation non-local realism. Well, realism it may be, but it differs sharply from common-sense realism. John Polkinghorne muses that neo-realists have jumped out of the frying pan of indeterminacy and into the fire of non-locality. Yet human nature being what it is, most practicing physicists continue to be realists of one sort or another, tending to visualize electrons as if they were ordinary objects flying along a path (even though our knowledge of the path is only statistical). And their calculations and experiments come out just fine. What else can scientists do, since quantum mechanics has yet to construct an alternative metaphor for the world?


Various metaphors have contended for dominance in science, either the world as mystical puzzle, or as an organism, or as a machine. Following Newton, the image of the world as a giant clockwork was accepted nearly universally by physicists. Today quantum mechanics has shattered that image, and yet offers nothing to replace it. Indeed, an undeterminate universe may even be inherently impossible to picture. As a result, most physicists continue to work within a basically Newtonian worldview in practice, even if they reject it in theory. They rely on common-sense realism, speaking of electrons in the same way they speak of billiard balls and inclined planes. Perhaps that is as good a reason as any to prefer a realist philosophy. As John Polkinghorne wrote, "Your average quantum mechanic is about as philosophically minded as your average garage mechanic."


Just as the latter might have an intuitive grasp of how a car works, that ought to be taken into account by anyone prone to theorizing about motors, so practicing physicists might have an intuitive grasp of their subject that ought to be taken into account in any philosophical interpretation. We may not believe that any particular realist interpretation has it quite right yet. But, John Polkinghorne concludes, "I submit it might be wise to look for an interpretation of quantum mechanics which comes as near as possible to being in accord with the attitude so widespread among its users."


Therefore, whatever philosophers of science may say, most working scientists remain realists, not only in regard to the ontological status of the quantum world, but also in regard to scientific knowledge. The realist believes that theories aim to describe the world and therefore can be true or false, not just useful, and that science consists largely of discovery, not just construction. These concepts are the stock-in-trade of every scientist. Even in particle physics, scientists speak of the discovery, not the invention, of a new particle. And they engage in extensive and costly research to discover whether the entities referred to in their theories really exist. For example, recall the recent Higgs boson discovery (first postulated in the 1960s and then confirmed in 2012). But for a more classic example, the existence of the neutrino (a class of electrically neutral low mass particles that only experience weak-nuclear and gravitational interactions) was first hypothesized by Wolfgang Pauli in the 1930s, because it made sense of a number of observations. Later the hypothesis solved other explanatory gaps in atomic theory. But no neutrinos had ever been detected, which bothered physicists. Neutrinos are so minute that physicists had to invest a tremendous amount of ingenuity, equipment, time, and money before they finally acquired good evidence that the tiny particles actually exist.


Christian astronomer Hugh Ross writes the following in regards to the discovery of neutrino mass:


For astronomers the icing on the cake of their exotic mass density measurements would be to actually detect some specific exotic mass particles. For over a decade physicists have noted that probably the easiest candidate would be neutrinos. Here, detecting neutrinos is not the problem. Physicists have been detecting them since 1956. The challenge is to prove that neutrinos have mass and, if possible, to accurately measure the mass of the neutrino. From a 1997 physics conference in Italy came the news that different research groups independently detected neutrino mass. To be more precise, they observed neutrinos oscillating, that is, spontaneously switching from one flavor to another. (Neutrinos come in three different varieties or flavors, namely, electron, muon, and tau.) Oscillation means mass. Neutrinos can oscillate only if they have mass. The case for neutrino mass was made more compelling because two radically different types of detectors came up with the same result. One was a 50,000-ton water tank surrounded by 13,400 photo detectors. The other was a thousand tons of corrugated iron interspersed with charged particle detectors. Additional evidence came in 1998 when the group using the 50,000-ton water tank confirmed neutrino oscillation from two sources: solar neutrinos and neutrinos in the earth’s atmosphere. Confirming the results from the two different oscillation experiments is what is called the “missing solar neutrinos” problem. Solar physicists now can understand why their neutrino detectors have found only a third of the neutrinos that they calculate the sun’s nuclear furnace must produce. Their detectors are tuned to pick up just one flavor of neutrino. The “missing” neutrinos apparently were missed when they oscillated. The neutrino “deficit” is no deficit at all. Neutrino oscillations only tell us that neutrinos have mass, not how much mass. But, they do establish the lower limit of that mass—at least a few billionths the mass of an electron, and potentially they can reveal the differences in mass among the three neutrino flavors. Several research labs are attempting to make direct measurements of neutrino mass, using something called “neutrinoless double beta decay” experiments. In 1997 a Russian-German collaboration determined that the neutrino mass can be no greater than 0.48 electron volts (that’s slightly less than a millionth of an electron mass). The difference between the lower and upper limits on the neutrino mass is nearly a factor of a thousand times. Fortunately, a new experiment was devised in 1999 that holds the promise of an accurate measure of the neutrino mass. It is a beta decay experiment based on the emission spectrum of the element rhenium. An Italian research team showed that there is enough detail in the rhenium beta decay emission spectrum to measure the neutrino mass.


Thus, the first thing to note is that it bothered physicists that a neutrino might be merely a useful concept (instrumentalism), or a linguistic convention that made sense of experiments (positivism), rather than a real entity. The second thing to note is that scientists were willing to expend a great deal of time and effort to confirm that neutrinos were in fact real. The fact that scientists instinctively operate on realist assumptions is perhaps a good reason to start with a realist stance whenever possible. There is, in fact, a growing trend in the philosophy of science today to define science according to actual scientific practice (what scientists actually do and think) rather than to prescribe what they ought to think.


Nevertheless, it must be acknowledged that quantum mechanics does modify many older forms of realism:


1. Realism has traditionally been associated with the ability to picture the world in some concrete model or analogy, such as the Newtonian image of the machine. But the quantum world cannot be pictured. We cannot picture something, for example, that is both a wave and a particle. But a realist epistemology should not have been tied to pictorial representation in the first place (argued by the famous Anglo-Catholic theologian E. L. Mascall). He famously wrote: "The paradigm of a real world is not its sensible imaginability but its intellectual apprehensibility. The world does not lose its claim to reality by ceasing to be imaginable as an infinite Euclidean receptacle populated by tiny, passive lumps drifting uniformly down the stream of time. The essential character of the objective world is not sensibility but intelligibility."


Thus, since the quantum world is difficult to picture, it is nonetheless highly intelligible mathematically. It can be grasped simply and elegantly in mathematical formulas. This is all that a realist epistemology requires.


2. Quantum physics provides an antidote to "hard" realism, which takes theories to be precise, literal descriptions of the world and denies the impact of a scientist's personal beliefs and commitments upon his work. Therefore, "soft" realism recognizes that the data are often ambiguous and that competing theories may fit the same observations, acknowledging that theories are not simply copies of nature; they are approximations, metaphors, and models. Nor are they derived mechanically simply by tabulating observations. Prior beliefs about what is real and what is scientifically plausible greatly influence what we choose to study, what results we look for in our experiments, and how we interpret those results. The unavoidable impact of the observer in quantum mechanics has driven these truths home in a new way.


So in summary, what do we make of this "mind over matter" argument as presented in this video? In the early days of quantum mechanics, many took it to be a repudiation of materialism and an open door to philosophical idealism. In fact, from the 1930s to the 1950s the idealist interpretation of quantum physics was quite widespread, thanks to popular works by James Jeans and Arthur Eddington.


Arthur Eddington enlisted the new physics for the cause of idealism with the argument that it made matter insubstantial. Newton described atoms as solid, hard, and impenetrable, like tiny billiard balls. But modern physics reveals that atoms are mostly empty space, consisting of a tiny nucleus surrounded by oscillating electrons. And even these are not material in the old sense; they are something like wads of condensed energy. Compared to the solid, substantial world of everyday perception, physics presents us with a world of shadows. Critics argue that Eddington confused energy with spirit or idea. A world of energy is just as physical as a world of matter. What quantum mechanics has done is merely replace old concepts of materialism with new concepts of materialism. It has not led to mentalism.


James Jeans adopted a different argument for idealism, a mathematical one. In quantum theory we cannot picture the universe in any coherent image; we can only describe it mathematically. But mathematics is a form of mental activity; hence, Jeans argued, the world is primarily mental. This is what he meant by his famous statement: "The stream of knowledge is heading towards a non-mechanical reality; the Universe begins to look more like a great thought than like a great machine. Mind no longer appears to be an accidental intruder into the realm of matter. We ought rather hail it as the creator and governor of the realm of matter."


Critics argue that Jeans misrepresented the nature of quantum physics. From his argument you might think it had become a branch of pure mathematics, a free creation of mathematical thought. But even in quantum physics, scientists still test their theories against experience. The tests may be very indirect, yet scientists still refer their theories to a physical world and not merely to a mental or mathematical world. Today the idealist interpretation of quantum physics has declined in popularity, living on primarily in works by New Age physicists. In these books, a major argument centers on the active role of the observer in quantum mechanics, interpreted to mean that the mind actually creates properties of the world. But, in quantum physics, since the observer does influence the outcome of experiments, it is not directly through his mind or consciousness. Rather it is through the tools he uses. A conscious observer doesn't need to be present for black marks to appear on a photographic screen, for a Geiger counter to click, or for tracks to appear in a cloud chamber. Indeed, for the last 4.5662 billion years, radioactive rocks have been decaying under the surface of the earth with no one observing them.


New Age idealism may claim support from quantum physics, but ironically it strikes a deathblow to physics, and all other branches of science. For science must begin with the assumption that there is an objective reality to be investigated. Even if we cannot know it perfectly, even if our act of observation affects it, even if it changes over time, still there must be something there, independent of our consciousness, in order for scientific investigation to proceed. There must be a world with its own inherent structure to which we can submit our theories to test them. But if the world is a creation of our own consciousness, as New Agers would have it, then it has no inherent structure. It can be altered to suit our beliefs. Hence there is nothing objective to test ideas against, and science is rendered impossible. It is curious that New Agers are so eager to claim scientific support for a philosophy that destroys the validity of science!


The Christian faith, by contrast, teaches that the world was created by God and that it exists independently of our perception. It is the handiwork of God, not the product of our minds (Genesis 1:1). Thus, this conviction is one reason the scientific revolution took place in Christian Europe and not in the Hindu East.

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