© Copyright Kirk Rader 2023. All rights reserved.
Almost daily, in certain corners of the media, yet another blog post, TV documentary, book or pop-sci magazine article appears, full of breathlessly overblown descriptions of how weird and brain-breaking Quantum Physics is including quotes from Professional Physicists explaining how Everything We Believe About the Nature of Reality Is Wrong!
Let's all just calm down.
A century ago, when the field of Quantum Physics was new and burgeoning, physicists might have been excused for reacting to its discoveries with shock and even disbelief. It took no lesser mind than that of Albert Einstein, who had pioneered the idea of treating photons as quanta of light, quite a while to fully internalize some of Quantum Physics' impossible-to-predict-in-advance results, particularly indeterminacy and entanglement. But consider that Einstein along with the originators of Quantum Mechanics like Bohrs were born firmly within the Victorian Age. Universal electrification of cities was still a work in progress when they were students. Steam power was still in use in non-trivial ways when they were working at the height of their intellectual powers. But what is so shocking, really? It turns out that billiard balls are made out of stuff at the sub-atomic level that does not behave exactly like a bunch of little tiny billiard balls. Stop the presses! Reality doesn't exist!
Would it not have been more surprising and metaphysically disturbing if the "particles" of particle physics actually did behave substantially like, well, particles? That would suggest an infinite regress of sub-sub-sub-atomic particles, each being very particle-like, to the power of \(-\infty\) and that really would be hard to reconcile with common sense. As it is, chunks of macroscopic matter have different properties than molecules, molecules have different properties than atoms, atoms have different properties than protons, neutrons and electrons which, in turn, have different properties than the rest of the denizens of the "particle zoo." As physics advances, what counts as a "fundamental" particle keeps changing: some particles formerly regarded as fundamental turn out to be composed of even smaller particles like quarks (and now, it seems, leptoquarks) with even stranger properties. But that does not mean that it is accurate to regard a quark as being a little ball and a hadron as being a bigger ball made of mashed-together quarks or an atom's nucleus being a ball of protons and neutrons, each of which is a littler ball, being orbited by a bunch of tiny balls, each of which is an electron, despite all those diagrams you saw in school.
Consider that mechanical clocks are not just collections of gears of particular sizes, springs of particular lengths and flexibility and so on. Clocks are collections of such bits and pieces arranged in very specific ways and maintained in a very particular state. Disassemble a clock and you have all the pieces of which a clock can be made, but none of those pieces on their own look or behave anything like a clock. You cannot tell time by looking at a pile of gears and springs, even if that pile is a disassmbled clock. You especially cannot tell time just using a single gear on its own.
Electrons are among the constituent bits and pieces out of which ordinary matter is made. They are too tiny to see on their own and travel too fast for us to follow as they whiz past (when viewed as "particles") or wash about (when viewed as "waves"), but a bunch of very clever people have figured out ways to perform hard-to-explain experiments measuring their actions and interactions. Human brains working the way they do, even the most clever people need to start with some sort of mental framework when trying to puzzle out completely new things. So, of course, phycists who were steeped in classical mechanics — because that is the only kind there was when science first became ready to tackle stuff at the quantum level — started to categorize and interpret the results they got when they started measuring the effects and properties of things like electrons. Reasoning by analogy to classical mechanics electrons when measured in some experiments "behave like waves" and in other experiments "behave like particles." This is only hard to reconcile if you forget that you were reasoning by analogy to begin with. It is no surprise that physicists may detect particle-like and wave-like properties in things that are neither particles nor waves using tools and techniques that can only ever measure indirectly some specific aspect of a thing they can never, even in principle, see exactly for what it is in the way we can literally see dust particles or ocean waves.
A billiard ball resting on a level surface will sit in perfect stillness and smug solidity when viewed at the scale at which human senses operate, right up to the moment that some external force is applied that sends it rolling off in some predictible direction, at some predictible speed, all according to Newton's comfortably explicable laws. Because that is how well polished spheres of lacquered wood behave. But dare zoom in far enough, pop-sci Physics warns, and the ball is nothing but a tenuous, seething cloud of mere probability that really should not be said to exist at all and is in danger at any moment of dissolving into a gamma ray burst or teleporting itself onto the surface of the moon. But is that not like saying that the old proverb about the blind men and the elephant means that elephants do not really exist but only wall-like things, and tree-like things, and rope-like things, and snake-like things?
A far more sensible way of regarding the supposed "weirdness" of Quantum Physics is that electrons behave like electrons, protons like protons etc. just as billiard balls behave like billiard balls. It is a metaphysical red herring known as reductionism to focus on the fact that the latter are made from the former. Since we cannot see at the sub-atomic level directly, we perform experiments and take measurements and construct mathematical models to describe the results. When we make the mistake of taking our reasoning by analogy with stuff we actually can see too seriously, our expectations are thwarted not because the behavior of stuff at the sub-atomic level is inexplicably and even threateningly different from the behavior of stuff made from that sub-atomic stuff, any more than the "reality" of a clock is threatened by the fact that it is made from parts that are, themselves, not at all clock-like. Stop talking or thinking about sub-atomic particles as being particles and suddenly things seem a lot less weird.
A corollary is that apparent paradoxes like the "tail problem" are not particularly problematic after all. Supposedly, quantum indeterminacy means that there is always some chance, even if only an ultra microscopically small chance, of some physical object acting in some observably non-classical way. Ask any casino operator: that is not how probability actually works. If it were, casinos would go out of business. As it is, they love nothing better than to give out giant jackpots because the marketing opportunities they represent are built into their extremely profitable business model. Casinos know very well, in advance, the limits to how much money they are going to give out over any given period of time because their games of chance are carefully and consciously designed to pay out at a certain rate even while not being rigged in the sense of outright cheating. The chance of a casino going broke because it had to pay too many jackpots all at once is transcendently higher than the chance of seeing some billiard ball start rolling around on its own due to quantum indeterminacy. Do not hold your breath waiting to see either of those events in the real world.
More signficantly, the "tail problem" looks at the indeterminacy of some state of an individual wavicle and imagines that it somehow equates to even a very small potential for indeterminacy at the macroscopic scale. But that relies on math that treats probablities as points on the infinitely subdivisible number line. That, in turn, ignores the quantum nature of reality, itself. The real problem here is Physcists mistaking features of their mathematical models for features of the stuff they are modeling. Yes, quantum indeterminacy is real. It can lead to measurable effects that can be usefully applied in science and engineering like quantum tunneling. No, that does not mean that there is some metaphysical threat to the nature of reality nor that cause and effect are illusory or provisional.
And then there is superposition and collapse. The way in which the "Copenhagen" and "Many Worlds" interpretations are usually discussed is more than a little silly. The act of observation, it is said, causes the wave function to collapse such that observation determines reality or wave functions never collapse such that the universe is constantly boiling off into unimaginably vast snarls of alternate histories each with its own unique combination of quantum outcomes. As appealing as the one is to mystics and the other to sci-fi authors, neither is at all necessary nor plausible. Even taking the Bell Theorem into account and accepting the experimental results confirming that there are no "hidden variables," there is a difference between reality and knowledge about reality. Schrödinger's cat is doing just fine, thank you very much — unless, of course, she isn't. That is because cats are not subject to quantum indeterminacy even if composed of stuff that is. If you make her well-being contingent on the indeterminate state of a quantum experiment (in a thought experiment! No cats were harmed in the writing of this article!) the indeterminacy remains at the quantum level, not at the level of the cat. The fact that we will not know whether the cat is alive or dead until we open the box does not mean that opening the box caused the cat's wave function to collapse, because wave functions do not actually have anything to say about cats. Ultimately, the supposed ontological crisis implied by the observer effect is just another example of taking mathematical model too seriously while applying it in a reductionist fashion.
Though not related to Quantum Physics, the same could be said about General Relativity and the "problem" of "time's arrow." General Relativity is true enough that it can make accurate predictions regarding astronomical observations like gravitational lensing and time dilation must be accounted for by aerospace engineers working on satellite based systems and the like. One of its basic premises is that time is just another mathematically interchangeable dimension of spacetime along with width, height and depth. But if that were all there were to say about time, then the inexorable and unidirectional passage of time and the rest of our very different experience of it compared to our experience of the three spatial dimensions of spacetime seems to need explanation. Einstein famously quipped that the passage of time is a "persistent illusion." Given his penchant for metaphor and sarcasm ("Spooky action at a distance," "God does not play dice with the universe," "the definition of insanity is performing the same experiment over and over while expecting different results" and the like), there is no reason to doubt Einstein's sanity in this regard. I imagine he was employing irony to point out that while his own mathematical model allows us to treat spacetime usefully and effectively as a four-dimensional plenum for the purposes of General Relativity, that cannot actually be all there is to a complete understanding of the nature of time. Attempts to supplement the reduction of space and time to spacetime with reference to something like entropy to account for "time's arrow" do not help and actually just highlight the real problem. Meta-mathematical models are by definition reductionist and so can be relied upon to produce the kind of "paradoxes" that arise when observations of the real world focus on phenomena outside the domain of discourse of a given model. Einstein's model only looks at time as a dimension of a mathematical abstraction known as spacetime and does not even attempt to pull into its description other properties of time that are not relevant to General Relativity, in particular those properties that make it quite different from spatial dimensions. This also explains the supposed "incompatibility" of General Relativity and Quantum Physics. To be "inconsistet," the two mathematical models would need to describe the same phenomena while somehow producing incompatible results. In fact, they each consist of entirely distinct mathematical models of unrelated physical phenomena that can only be connected through a fallacious kind of reductionism. Saying that they contradict one another is like saying that a German text on automobile repair contradicts a cookbook written in French because they do not say the same things. To continue that analogy, to say that General Relativity needs to be "reconciled" with Quantum Physics is like saying that texts about automobile repairs and cooking written in different languages need to be "reconciled" since both mechanics and cooks operate under the constraints of Chemistry and Physics. They do, but in ways not relevant to sets of instructions on how to maintain a Porsche or prepare a soufflé.
In short, Physicists (really, pop-sci journalists) would do well to leave Metaphysics to the professionals in the Philosophy Department. Ideally, they will just get on with the business of calculating their wave functions and conducting their experiments, letting the rest of us in on the interesting and useful stuff they discover along the way without all the melodrama.