Monday, December 23, 2013

Silly use of uncertainty metaphor

People are often saying nonsense about the uncertainty principle, but it is annoying to see it in a reputable science magazine.

Walter G. Montgomery says he has a PhD and writes in Scientific American:
In quantum mechanics, Heisenberg’s Uncertainty Principle holds that it is impossible to determine both the position and momentum of a particle. Heisenberg’s breakthrough relates to a subject of vital importance to America: the need for better communications practices in the science and technology fields.

Communications is my profession, and I am concerned by what I see. ...

The third and most challenging way in which science and technology communications differ from communications practices in other fields brings us back to the Uncertainty Principle. In other realms, superior communications professionals work side-by-side with clients to craft consistent and compelling messages and documents that concern finite situations that occur in specific spaces and points in time. They may, for example, draft a press release to announce a company acquisition, a statement explaining a C-level executive succession or an internal communications piece that describes to company employees the importance of a new product or service launch. In each of those cases, our job is to explain what has happened in terms that are as concrete and definitive as possible.

Messaging around science and technology, however, is a different story, because science rarely involves certainty. Rather, science is a quest for objective truth that might never achieve a final, definitive outcome. Given that science is an ever-unfolding story in which the goal posts keep moving—and that today’s vouchsafed hypothesis might be modified six months from now—crafting solid messaging around uncertainty becomes a unique communications challenge.
No, the uncertainty principle is not about our lack of knowledge about some final objective truth that we can might never achieve. There is plenty of certainty in science. Science has more certainty than any other field, except mathematics. Reporting on scientific experiments and other progress is just as certain as reporting in the business world, if not much more so. Usually scientists are at least trying to tell the truth in their press releases, while business press releases nearly always tell some partial truth designed to promote the sale of a product.

Lumo rants:
The probabilities in quantum mechanics do have exactly the same physical interpretation as the probabilities resulting from ignorance in classical statistical physics – i.e. as the probabilities calculable from the distribution functions on the classical phase space. The actual difference between classical statistical physics and quantum mechanics is the uncertainty principle that governs the latter. The uncertainty principle says that some degree of the ignorance is fundamentally unavoidable, independently of the chosen observer, her measuring apparatus, or methodology. Mathematically speaking, the new feature of quantum mechanics is the nonzero commutator between generic enough observables. It is not just a specific technical feature of some particles; it is a key conceptual rule that holds everywhere in this quantum world: The truths themselves refuse to commute in this Universe.

It seems very obvious to me that Scott Aaronson doesn't understand these basic conceptual findings about the character of probabilities in statistical physics and quantum mechanics. He's not the only one; almost everyone else who loves to write "popular" texts about quantum mechanics these days is similarly deluded. These people maintain some insane anti-Bohr, anti-Heisenberg sentiments that prevent them from seeing that by these assaults against the deepest findings done by these two men (and their school), they are exactly as canonical crackpots as "biologists" who love to constantly assault Darwin's "mistakes".
He is a little hard on Aaronson, who obviously understands quantum mechanics very well, but is correct about the uncertainty principle. The fundamental new feature of quantum mechanics is that observables do not commute, thereby necessitating and uncertainty in their measurements. Bohr and Heisenberg had this part of the theory exactly correct, and Einstein had it wrong. Progress in the last 75 years has only affirmed what Bohr and Heisenberg said. I cannot explain why Aaronson seems to have a different view, and writes:
You might say that Bohr and Heisenberg got closer to what we now know to be the truth about QM (i.e., that local hidden-variable theories can’t work, and the probabilities in QM can’t have an ordinary ignorance interpretation like in QM). ...

Bohr and Heisenberg both had the properties of

(1) putting way more stress on “wave/particle complementarity” and the uncertainty principle than we’d put today,

(2) bizarrely, saying almost nothing about the aspects of QM we do see as central today, like entanglement, the enormous size of Hilbert space, or amplitudes being complex-valued analogues of probabilities, ...
The probabilities in QM certainly do have an ordinary ignorance interpretation, with that ignorance being the ignorance of measurement. They are not interpreted as probabilities of hidden variables, of course, as Bohr and Heisenberg rejected the sort of hidden variable theories that Einstein and others stubbornly and wrongly clung to.

Entanglement is overrated. The enormous size of Hilbert space is a trivial mathematical fact, and not that important unless you are arguing for some silly theory like the Many Worlds Interpretation. I also do not agree that the amplitudes are complex-valued analogues of probabilities. The amplitudes can be used to calculate probabilities, but that's all. Aaronson has his own popular book on quantum mechanics, but he has some distorted views.

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