"Rational Quantum Dynamics, Were Such a Thing to Exist"
For most of the last century, the achievements of physics were used to prop up the failures of the humanities. Quantum physics was endlessly interpreted (and abused) to provide a supposed scientific confirmation for irrationalist and mystical doctrines. The latest discoveries of science, it was said, confirmed that knowledge is impossible, that we can achieve only probability and not certainty, that everything is subjective, and that the world is made up of impenetrable contradictions from the subatomic level on up.
This was always based on distortions and misapplications of the real physics, but it had enough backing from the original physicists to make it stick. Some of the pioneers of quantum physics embraced the subjectivist interpretations, which should be no surprise when you consider the intellectual environment they came from: the irrationalist Modernism of early 20th-century Europe. If you consider what was going on in art, in music, in literature, and in philosophy, it's no surprise that some of the scientists would want to harmonize their work with the prevailing intellectual direction of the era.
This provided the foothold for later interpreters and popularizers to fully recruit quantum physics—the very frontier of modern science!—as evidence that the Modernists are right to reject reason and objective reality. When I was young, the latest vogue was to claim that quantum physics validates Eastern mysticism. This version rose up in 1975—the 1970s, wouldn't you know it—with Fritjof Capra's The Tao of Physics, which I read as a student some time in the 1980s. Looking back, I recall it as a vast exercise in reasoning by vague analogy. Capra went trolling through the popular portrayal of quantum physics, cherry picking ideas that he could then present as vaguely similar to some idea picked out of Hinduism, Buddhism, or Taoism. (It didn't really matter which.) It was a pretty sloppy, unscientific endeavor, and not much use as an accurate description of Eastern religion, as far as I can tell, but it sure impressed the hell out of the humanities majors.
I mention all of this because I've seen a few signs lately that the irrationalist appropriation of quantum physics may be meeting more resistance.
The New York Times blog The Stone publishes essays from academic philosophers, and the results are frequently pretty dreadful, but it recently published an interesting piece from philosopher of science Craig Callender challenging the abuse of Heisenberg's Uncertainty Principle.
Why exactly is the uncertainty principle so misused? No doubt our sensationalist and mystery-mongering culture is partly responsible. But much of the blame should be reserved for the founders of quantum physics themselves, [Werner] Heisenberg and Niels Bohr....
Heisenberg vividly explained uncertainty with the example of taking a picture of an electron. To photograph an electron's position—its location in space—one needs to reflect light off the particle. But bouncing light off an electron imparts energy to it, causing it to move, thereby making uncertain its velocity. To know velocity with certainty would then require another measurement. And so on. While this "disturbance" picture of measurement is intuitive...it leaves the reason for uncertainty mysterious. Measurement always disturbs, yet that didn't stop classical physicists from in principle knowing position and velocity simultaneously.
For this reason Heisenberg supplemented this picture with a theory in which measurement figures prominently. It's not simply that we can't simultaneously measure definite values of position and momentum, he thought. It's that before measurement those values don't simultaneously exist. The act of observation brings into existence the properties of the world. Here we find the seeds of the claims made by some social theorists and found in [the movie] "What the Bleep Do We Know!?" If reality depends on interaction with us, it's natural to suppose that objectivity is undermined and that we, from the outside, make reality, possibly with some kind of mental energy.
Students of philosophy will recognize Heisenberg's interpretation—that the act of perceiving something distorts what you perceive, so that you can never really know the thing as it really is—as just a restatement of the 18th-century German philosopher Immanual Kant, projected by German scientists onto 20th-century physics. It is physics dragooned into the service of a pre-existing philosophical commitment.
Callender offers an interesting argument against Heisenberg's interpretation, pointing out that Heisenberg makes the act of measurement somehow metaphysically special—whereas reality has no way of telling the difference between an interaction among particles that results from a human effort at measurement, versus an interaction among particles that happens as a random matter of course.
Interactions abound. What qualifies some as measurements? Inasmuch as disturbance is related to uncertainty, it's hardly surprising that observing something causes it to change, since one observes by interacting. But a clear and complete physical theory should describe the physical interaction in its own terms....
[A]ll the truly wild claims—that observers are metaphysically important, that objectivity is impossible, that we posses a special kind of mental energy—are the result of foggy interpretations made even less sharp by those wanting to validate their pet metaphysical claims with quantum physics.
To prevent future temptation to misuse, I urge that we demote the uncertainty principle. If Pluto can be reclassified as a dwarf planet, then surely we can do something similar here.
I think there's more to say about the absurdity of how Heisenberg's idea has been presented, but the point isn't what I say about it. It's the fact that there are mainstream voices which are speaking out against Heisenberg abuse.
But there's also something much more interesting that's happening, a development in physics—recounted in MIT News—that strikes to the heart of the irrationalist interpretation of subatomic physics.
The trouble began with the famous "double slit" experiment, in which light shows some of the characteristics of a discrete particle, while also showing some characteristics of a wave.
If a wave traveling on the surface of water strikes a barrier with two slits in it, two waves will emerge on the other side. Where the crests of those waves intersect, they form a larger wave; where a crest intersects with a trough, the fluid is still. A bank of pressure sensors struck by the waves would register an 'interference pattern'—a series of alternating light and dark bands indicating where the waves reinforced or canceled each other.
Photons fired through a screen with two holes in it produce a similar interference pattern—even when they're fired one at a time. That's wave-particle duality: the mathematics of wave mechanics explains the statistical behavior of moving particles.
But how can light be both a particle and a wave at the same time? It seems to contradict Aristotle's famous Law of Non-Contradiction: that a thing cannot both be and not be at the same time and in the same respect.
For those who retained their commitment to this Aristotelian axiom, quantum physics never actually posed a fundamental threat. It posed a problem to be solved: what kind of thing can have the characteristics of both a particle and a wave? The main theory that was offered was the idea of a "pilot wave."
In the early days of quantum physics, in an attempt to explain the wavelike behavior of quantum particles, the French physicist Louis de Broglie proposed what he called a 'pilot wave' theory. According to de Broglie, moving particles—such as electrons, or the photons in a beam of light—are borne along on waves of some type, like driftwood on a tide.
In other words, light is not both a particle and wave at the same time and in the same respect. It is a particle in one respect, and a wave in a different respect. So the "duality" is not a contradiction but the result of two separate things working together.
The MIT News article notes that "Physicists' inability to detect de Broglie's posited waves led them, for the most part, to abandon pilot-wave theory." I have to wonder to what extent they abandoned the theory due to lack of evidence, or whether they stopped looking for evidence because of the pressure from "those wanting to validate their pet metaphysical claims with quantum physics," as Callender put it.
At any rate, there is now new evidence that brings the pilot wave theory back into play.
Recently, however, a real pilot-wave system has been discovered, in which a drop of fluid bounces across a vibrating fluid bath, propelled by waves produced by its own collisions.
In 2006, Yves Couder and Emmanuel Fort, physicists at Université Paris Diderot, used this system to reproduce one of the most famous experiments in quantum physics: the so-called 'double-slit' experiment, in which particles are fired at a screen through a barrier with two holes in it.
In the latest issue of the journal Physical Review E (PRE), a team of MIT researchers, in collaboration with Couder and his colleagues, report that they have produced the fluidic analogue of another classic quantum experiment, in which electrons are confined to a circular "corral" by a ring of ions. In the new experiments, bouncing drops of fluid mimicked the electrons' statistical behavior with remarkable accuracy.
Note that this is not the discovery of pilot waves on the quantum level. This is a discovery from larger-scale fluid dynamics. But by showing that a pilot wave system can exist and that it produces exactly the kind of results seen on the quantum level, it has the potential to renew the search for such a system in quantum physics—a system which would resolve all of the apparent irrationalism of the traditional interpretations.
(UPDATE: You can see a video of these experiments by way of Morgan Freeman, whose narration confirms their philosophical impact.)
As one of the researchers, MIT professor John Bush, puts it: "It's the first pilot-wave system discovered and gives insight into how rational quantum dynamics might work, were such a thing to exist."
Were such a thing to exist. Well, this experiment invites someone to bring it into existence, doesn't it?
I should acknowledge that in commenting on this experiment, I am going outside my area of expertise. In this area, I'm like someone traveling in a foreign country who knows enough to (mostly) understand the language when it is spoken to him, but who can't speak it himself. But it really strikes me that, in demonstrating a real physical system that exhibits the "wave-particle duality" in a totally consistent, rationally understandable way, and which produces exactly the same kind of results as quantum mechanics, it presents a prima facie case for suspecting that the same thing must be at work at the quantum level. It might also provide new clues for how to look for "pilot waves" on the quantum level.
Since I'm not an expert, I'll refer to another professor, Paul Milewski, who is quoted in the MIT News article describing the implications of the new experiment.
Experiments like this weren't available to the giants of quantum mechanics.... Suppose these guys—who were puzzled by why the world behaves in this strange probabilistic way—actually had access to experiments like this and had the knowledge of chaos [theory], would they have come up with an equivalent, deterministic theory of quantum mechanics, which is not the current one? That's what I find exciting from the quantum perspective.
In effect, what Milewski is describing is an opportunity for a philosophical "do-over" of quantum mechanics, in which the whole system is re-thought in a way that is consistent with Aristotelian metaphysics and a rational view of the world—and mysticism and irrationalism are left high and dry, without any supposed "validation" from cutting-edge physics.
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