Scivillage.com Casual Discussion Science Forum

http://backreaction.blogspot.com/2019/06...-ball.html

EXCERPT (Sabine Hossenfelder): . . . Philip Ball knows what he writes about, that’s obvious from page one. For all I can tell the science in his book is flawless. It is also engagingly told, with some history but not too much, with some reference to current research, but not too much, with some philosophical discourse but not too much. Altogether, it is a well-balanced mix that should be understandable for everyone, even those without prior knowledge of the topic. And I entirely agree with Ball that calling quantum mechanics “weird” or “strange” isn’t helpful.

In “Beyond Weird,” Ball does a great job sorting out the most common confusions about quantum mechanics, such as that it is about discretization (it is not), that it defies the speed of light limit (it does not), or that it tells you something about consciousness (huh?). Ball even cleans up with the myth that Einstein hated quantum mechanics (he did not), Feynman dubbed the Copenhagen interpretation “Shut up and calculate” (he did not, also, there isn’t really such a thing as the Copenhagen interpretation), and, best of all, clears out the idea that many worlds solves the measurement problem (it does not).

In Ball’s book, you will learn just what quantum mechanics is (uncertainty, entanglement, superpositions, [de]coherence, measurement, non-locality, contextuality, etc), what the major interpretations of quantum mechanics are (Copenhagen, QBism, Many Worlds, Collapse models, Pilot Waves), and what the currently discussed issues are (epistemic vs ontic, quantum computing, the role of information). (MORE)

RELATED: Peter Woit review of "Beyond Weird" ... Conversation with Philip Ball about book

Quote:that it tells you something about consciousness (huh?).

If it tells us something about epistemic vs ontic, then it's about consciousness imo..

(Jun 16, 2019 08:49 PM)Magical Realist Wrote: [ -> ]

Quote:that it tells you something about consciousness (huh?).

If it tells us something about epistemic vs ontic, then it's about consciousness imo...

I suppose she could be referring to slash disparaging quantum theories of consciousness. But since it's Philip Ball's book that is the focus, I assume instead it's what he mentions below. Decoherence discards the role of conscious observers which is often implied in the Copenhagen Interpretation. It wasn't until the 1950s that Heisenberg actually fabricated the latter from informal lectures given by Bohr[*] decades earlier (and his own material). Despite that dubious origin it somehow became the default orientation or gospel. There's no definitive text from the 1920s establishing what CI is, just a collection of principles assembled up that have a degree of consensus.

The quantum view of reality might not be so weird after all (Philip Ball): Thanks to the theory of decoherence, we no longer have to make quantum measurement some magical and mysterious event that crystallises knowledge. We have a mathematical theory to explain how information gets out of the quantum system and into the macroscopic apparatus. We can use the theory to calculate how quickly that happens, and how robustly. We have, at long last, a theory of measurement. What’s more, it is a theory that confers no privileged status on the conscious observer, stripping away the seemingly mystical veneer from quantum mechanics.

There’s no longer any need for Bohr’s arbitrary division of the world into the microscopic, where quantum mechanics rules, and macroscopic, which is necessarily classical. Now we can see not only that they are a continuum, but also that classical physics is just a special case of quantum physics. Regarded this way, common sense is a direct and utterly sensible outgrowth of quantum sense.

[...] Quantum effects such as interference rely on the wave functions of different entities being coordinated (the technical term is coherent) with one another. If they’re not, the effects are averaged away. That sort of coherence is what permits the quantum property of superposition, in which particles are said to be in two or more states at once. Again, they’re not really in two states at once – we don’t know how best to describe what they really are in a classical sense. But if the wave functions of those states are coherent, then both states remain possible outcomes of a measurement.

If their wave functions are not coherent, two states cannot interfere, nor maintain a superposition. The process called decoherence therefore destroys these fundamentally quantum properties, and the states behave more like distinct classical systems. Macroscopic objects don’t display quantum interference or exist as superpositions because they can’t be described by coherent wave functions. This – and not sheer size per se – is the fundamental dividing line between what we think of as quantum versus classical (familiar) behaviour. Quantum coherence is essentially what defines ‘quantum-ness’.

What, though, causes decoherence? This arises because of a long-neglected aspect of quantum entities: their environment. The way a quantum system behaves and evolves can depend crucially on the fact that it doesn’t exist in isolation. The environment is what conjures classical physics – and ‘common-sense’ behaviour – out of the quantum soup.

[...] The foundations of decoherence theory were laid in the 1970s by the German physicist H Dieter Zeh. Even then it was largely ignored until two papers on the ‘decoherence programme’ the following decade, by Wojciech Zurek at the Los Alamos National Laboratory in New Mexico, brought it to a wide audience.

[...] Notice that this effect of decoherence has nothing to do with observation in the normal sense. To turn quantum to classical, we don’t need a conscious mind to measure or look; we just need an environment full of stuff. With or without us, the Universe is always looking. (MORE)

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[*] SEP entry (Jan Faye): In fact Bohr and Heisenberg never totally agreed on how to understand the mathematical formalism of quantum mechanics, and neither of them ever used the term “the Copenhagen interpretation” as a joint name for their ideas. In fact, Bohr once distanced himself from what he considered to be Heisenberg's more subjective interpretation [...] Bohr was definitely neither a subjectivist nor a positivist philosopher, as Karl Popper and Mario Bunge have claimed. He explicitly rejected the idea that the experimental outcome is due to the observer. As he said: “It is certainly not possible for the observer to influence the events which may appear under the conditions he has arranged”.

Not unlike Kant, Bohr thought that we could have objective knowledge only in case we can distinguish between the experiential subject and the experienced object. It is a precondition for the knowledge of a phenomenon as being something distinct from the sensorial subject, that we can refer to it as an object without involving the subject's experience of the object. In order to separate the object from the subject itself, the experiential subject must be able to distinguish between the form and the content of his or her experiences. This is possible only if the subject uses causal and spatial-temporal concepts for describing the sensorial content, placing phenomena in causal connection in space and time, since it is the causal space-time description of our perceptions that constitutes the criterion of reality for them. Bohr therefore believed that what gives us the possibility of talking about an object and an objectively existing reality is the application of those necessary concepts, and that the physical equivalents of “space,” “time,” “causation,” and “continuity” were the concepts “position,” “time,” “momentum,” and “energy,” which he referred to as the classical concepts. He also believed that the above basic concepts exist already as preconditions of unambiguous and meaningful communication, built in as rules of our ordinary language. So, in Bohr's opinion the conditions for an objective description of nature given by the concepts of classical physics were merely a refinement of the preconditions of human knowledge.