That God Playing Dice With the Universe Thing Again

Quanta has an article with the intriguing title: “Have We Been Interpreting Quantum Mechanics Wrong This Whole Time?”. Far be it from me to interpret quantum mechanics at all, so I’ll merely quote:

…That nature is inherently probabilistic — that particles have no hard properties, only likelihoods, until they are observed — is directly implied by the standard equations of quantum mechanics. But now a set of surprising experiments with fluids has revived old skepticism about that worldview. The bizarre results are fueling interest in an almost forgotten version of quantum mechanics, one that never gave up the idea of a single, concrete reality.

The experiments involve an oil droplet that bounces along the surface of a liquid. The droplet gently sloshes the liquid with every bounce. At the same time, ripples from past bounces affect its course. The droplet’s interaction with its own ripples, which form what’s known as a pilot wave, causes it to exhibit behaviors previously thought to be peculiar to elementary particles — including behaviors seen as evidence that these particles are spread through space like waves, without any specific location, until they are measured.

Particles at the quantum scale seem to do things that human-scale objects do not do. They can tunnel through barriers, spontaneously arise or annihilate, and occupy discrete energy levels. This new body of research reveals that oil droplets, when guided by pilot waves, also exhibit these quantum-like features.

Assuming that continued experimentation confirms that the probabilistic behavior of these droplets and fluids mirrors the behavior of quantum-level particles, the question would be: Is this similarity a mere coincidence or does it indicate that there is an underlying deterministic basis for apparently spooky, indeterministic quantum events? 

To some researchers, the experiments suggest that quantum objects are as definite as droplets, and that they too are guided by pilot waves — in this case, fluid-like undulations in space and time. These arguments have injected new life into a deterministic (as opposed to probabilistic) theory of the microscopic world first proposed, and rejected, at the birth of quantum mechanics.

“This is a classical system that exhibits behavior that people previously thought was exclusive to the quantum realm, and we can say why,” said John Bush, a professor of applied mathematics at the Massachusetts Institute of Technology who has led several recent bouncing-droplet experiments. “The more things we understand and can provide a physical rationale for, the more difficult it will be to defend the ‘quantum mechanics is magic’ perspective.”

The great French physicist Louis De Broglie first proposed a deterministic pilot-wave theory in the 1920s. David Bohm famously proposed a later version. According to the article, John Stewart Bell, the author of Bell’s Theorem, which supposedly shows that quantum mechanics cannot be deterministically explained by “hidden variables”, was also a proponent:

In 1986, [Bell] wrote that pilot-wave theory “seems to me so natural and simple, to resolve the wave-particle dilemma in such a clear and ordinary way, that it is a great mystery to me that it was so generally ignored.” 

Of course, many physicists are skeptical, as they should be. Overturning the standard interpretation of quantum mechanics (the indeterministic “Copenhagen” interpretation) would be a very big deal. But doing so would make our universe much less mysterious (no more God playing dice). And it would allow physicists to give up the increasingly popular idea that there are many, many universes (the “multiverse” interpretation of QM). We might then go back to thinking of the universe as a unique, cozy place where everything happens for a reason.

2 thoughts on “That God Playing Dice With the Universe Thing Again

  1. I have some sympathy with the deBroglie-Bohm interpretation, but I can understand why most physicists would be skeptical of fluid dynamics experiments necessarily meaning much for actual quantum systems. Still, the experiments are interesting.

    • I find this all very interesting. If the fluid dynamics physicists are able to duplicate lots of phenomena previously thought to occur only at the quantum level, that will suggest that the same underlying principles are at work in both cases. It might be a coincidence, but the more reasonable and more elegant conclusion will be that the high-level and low-level phenomena occur for the same reasons. What a discovery it would be to unify fluid dynamics and quantum mechanics!

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