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from the quantum-reality-is-just-classical-reality-in-really-tiny-bits? dept.
For nearly a century, "reality" has been a murky concept. The laws of quantum physics seem to suggest that particles spend much of their time in a ghostly state, lacking even basic properties such as a definite location and instead existing everywhere and nowhere at once. Only when a particle is measured does it suddenly materialize, appearing to pick its position as if by a roll of the dice. This idea 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 world-view. 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.
In a groundbreaking experiment, the Paris researchers used the droplet setup to demonstrate single- and double-slit interference. They discovered that when a droplet bounces toward a pair of openings in a damlike barrier, it passes through only one slit or the other, while the pilot wave passes through both. Repeated trials show that the overlapping wavefronts of the pilot wave steer the droplets to certain places and never to locations in between — an apparent replication of the interference pattern in the quantum double-slit experiment that Feynman described as "impossible ... to explain in any classical way." And just as measuring the trajectories of particles seems to "collapse" their simultaneous realities, disturbing the pilot wave in the bouncing-droplet experiment destroys the interference pattern.
Droplets can also seem to "tunnel" through barriers, orbit each other in stable "bound states," and exhibit properties analogous to quantum spin and electromagnetic attraction. When confined to circular areas called corrals, they form concentric rings analogous to the standing waves generated by electrons in quantum corrals. They even annihilate with subsurface bubbles, an effect reminiscent of the mutual destruction of matter and antimatter particles.
How about it Soylentils. Is there anyone here who groks Quantum Mechanics who would care to explain this in layman's terms? What shortcomings and/or benefits do you see with this theory?
(Score: 3, Informative) by kebes on Tuesday July 01 2014, @10:33PM
In any case, I'll happily defer to the real experts on QM theory. Such as:
Sean Carroll [wikipedia.org] (CalTech) has some nice general-audience blog entries:
Why the Many-Worlds Formulation of Quantum Mechanics Is Probably Correct [preposterousuniverse.com]
Does This Ontological Commitment Make Me Look Fat? [preposterousuniverse.com]
Quantum Mechanics Made Easy [preposterousuniverse.com]
(This blog post [lesswrong.com] covers some similar ground.)
Allan Adams [mit.edu] has an intro to quantum [mit.edu] course that is freely available on MIT Open Courseware, and provides a good intro (without resorting to the any Copenhagen verbiage).
Max Tegmark [mit.edu] (MIT) wrote a Nature commentary, Many lives in many worlds [mit.edu], that provides a general-audience into to a deterministic interpretation of QM. He also has some more technical papers on these topics (the intros and conclusions may be useful even to non-specialists):
Many Worlds in Context [arxiv.org]
Parallel Universes [arxiv.org]
Yet more technical, but still interesting, are the results of decoherence (in large part from Wojciech H. Zurek [wikipedia.org] ):
Decoherence, the measurement problem, and interpretations of quantum mechanics [arxiv.org]
The quantum-to-classical transition and decoherence [arxiv.org]
Decoherence and the transition from quantum to classical [arxiv.org]
(Score: 2) by melikamp on Wednesday July 02 2014, @06:03AM
Fascinating thread. I have a few general comments.
The interpretation does matter, even to physicists. It seems at least possible that the universe (or some aspect of it) is in fact a mathematical object. If it is, then it may be possible to ascertain this fact statistically. (For example, if it is deterministic, and there is a way to check the outcomes experimentally, and to re-stage these experiments many times over.) That would be an interesting discovery, and one worth making. And talking about deterministic interpretations and deterministic mathematical formalism is a basic heuristic for getting there.
As a mathematician, I don't see how a deterministic mathematical universe is more or less surprising than a non-deterministic mathematical universe. It would be far more surprising to me if the universe was discovered to be a mathematical object at all (although also deeply satisfying). Exactly what kind of mathematical object? Well, right now it looks like it is geometrical on large scales and algebraic/probabilistic on small scales (algebraic geometry is hot, incidentally), but it in the end it may turn out to be something really silly, like a finite sequence of distance matrices. All of these possibilities have exactly the same ontological status for mathematicians, and in particular, the probability theory with its perfect theoretical distributions is no less true or concrete than the integer arithmetic.
Alas, if this is the grail, then the odds are against us. Assuming that the world is mathematical, it may simply be too complicated to pin down. What if it is a bit longer than Newton's laws or the field equations? For example, it may be fully described as an algorithm (a Turing machine program) operating on a very large array of simple "particles", kind of like in the world of Newton. And this algorithm just happens to be a fancy PRNG-like gizmo with emergent macroscopic properties we are observing (so yeah, it sucks as an RNG, but because of that we have galaxies, planets and life instead of a homogenous soup). And the shortest description of this algorithm in, say, Lisp, is 10 MiB in length: a modest program by modern standards, but far more complicated than any PRNG devised so far. So a physicist may be faced with reverse-engineering a PRNG of incredible complexity, and that without even a perfect way to read the output.
The odds are against us in the sense that there are far more long programs than there are short ones, and a 10 MiB, or even a 10 TiB program is absolutely tiny when faced with the infinity of all possible programs. I don't mean to call actual odds here, only to express the cautiousness of my optimism.
(Score: 2) by kebes on Wednesday July 02 2014, @12:56PM
The Mathematical Universe [arxiv.org]
Is "the theory of everything'' merely the ultimate ensemble theory? [arxiv.org]
Shut up and calculate [arxiv.org]
On Math, Matter and Mind [arxiv.org]
The ideas he's putting forth are that:
1. The universe is, inescapably, a mathematical structure. One way of thinking about this is to say that if the universe is consistent, then it must be described by some set of non-contradictory rules, in which case one can find a mathematical formalism isomorphic to those rules. Tegmark phrases it slightly differently: explaining instead that if one accepts that the universe has independent reality (not just a product of our minds), then it must have some observer-independent description; which again implies one can find a mathematical formalism isomorphic to that description. (Read the paper for the rigorous version of this argument.)
2. If our universe is actually a mathematical structure, why does it have physical reality? Perhaps other mathematical structures also do? Perhaps all consistent mathematical structures have physical reality?
It's a long way from being a sound scientific theory, but interestingly Tegmark sketches out how this idea could be tested experimentally. It also has some interesting implications, e.g. that the description of the universe becomes so generalized, compact, and elegant, that its information content is nearly zero [arxiv.org].
Again, this is all just speculation at this point, but these are fun concepts to think about.
(Score: 0) by Anonymous Coward on Wednesday July 02 2014, @04:03PM
Thank you so much for your comments, those are one of the most interesting/insightful comments I've seen on any "nerdy" website about a particular topic so far. If you had some website/blog with interesting ideas/facts about QM or other topics, I'd be very happy to have it in my RSS feed :)
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Posting anonymously, because I'm clearly OT - feel free to downvote :).