You don't need much time to see that Becker is a hardcore anti-quantum jihadist at the level of Tim Maudlin – it's often impossible to distinguish which of the two men wrote a given text – while Philip Ball is a moderate jihadist.
Let me discuss the text
The first question that Ball obfuscates is "Who are the authors of the Copenhagen Interpretation":
I think James Cushing makes a good case that it was largely a retrospective invention of Heisenberg’s, quite possibly as an attempt to rehabilitate himself into the physics community after the war. As I say in Beyond Weird, my feeling is that when we talk about “Copenhagen”, we ought really to stick as close as we can to Bohr – not just for consistency but also because he was the most careful of the Copenhagenist thinkers.Holy cow. Why does he write a book claiming to teach the reader something about the history of the Copenhagen Interpretation if he doesn't know even the answers to these basic questions?
OK, so when and by whom was the "interpretation" invented? The beef of the "interpretation" has been a part of the thinking of the founding fathers from the beginning – and the articulation of its rules has evolved somewhat gradually. But concerning the term, you may check that in a 1929 lecture, Heisenberg outlined his effort to "spread the Copenhagen spirit". That spirit is a "way of thinking" that was adopted, nurtured, and elaborated upon in Copenhagen.
Everyone who has followed the basic facts knows that Heisenberg primarily meant himself and Bohr as the "masterminds of the Copenhagen spirit". Others people could have contributed and that's why the more inclusive name based on the city was chosen. These debates usually took place in the Danish capital. Bohr and Heisenberg were screaming at one another before they agreed that they were basically advancing the same ideas using different words.
Also, one may learn that the explicit term "Copenhagen Interpretation" was coined by Heisenberg in 1955. So Heisenberg himself is the originator of the word "interpretation" that spread like fire among the philosophers whose obsession is to question quantum mechanics. Before his book was published, Heisenberg already realized that he had shot himself in the foot and by coining the term "interpretation", lots of morons would be constructing their own "interpretations". And indeed, that's exactly what happened.
In fact, it's worse than that:
By the time you're 35 you should have your own interpretation of quantum mechanics.— Sabine Hossenfelder (@skdh) 27. května 2018
Note the huge number of "likes" under this staggeringly idiotic tweet. There's a whole movement of idiots who try to tear down physics. Maybe the number of such folks is so high that I should be afraid of going to the street after I pointed out that all these people are incredible idiots. Well, I still think we live in the Western society where I can say that there's only one theory of quantum mechanics whose "core" is a set of the most general rules how to apply it in scientific thinking – its "interpretation" – and this core is absolutely unique and everyone who believes in a different core or a "plurality of interpretations" is completely ignorant about modern physics.
As a major representative of those people points out, every idiot should propose her interpretation of quantum mechanics by the age of 35. And that's almost what's happening – about one-half of the idiots in the world actually do propose their "own interpretations". While Heisenberg who coined the term "interpretation" in the discussions about the conceptual foundations of quantum mechanics did think that every "other interpretation" is complete hogwash, as of 2018, we're literally drowning in an ocean of dozens of "interpretations" invented by assorted morons.
If you knew these basic historical facts about the "Copenhagen Interpretation", why would you pretend it's some deep discovery that Werner Heisenberg has coined the term? But what I find disgusting is Ball's remark about the "motivation" behind the "Copenhagen Interpretation":
...quite possibly as an attempt to rehabilitate himself into the physics community after the war...What? What do the foundations of quantum mechanics have to do with the political "rehabilitation"? Everything that Heisenberg – and everyone else – has done for the mankind makes it easier to "rehabilitate" them. Heisenberg has clearly been one of the most important scientists of the 20th century. His track record during the war didn't include something shocking that he would really have to be ashamed of. He was a typical German patriot – but as a theoretical physicist, he was also an honorary Jew.
(And Bohr, a half-Jewish man, has done some things to help the victims of Nazism.)
Even if we believed that Heisenberg needed some "rehabilitation", why would you include this comment to the discussion about the foundations of quantum mechanics? Let me tell you why Ball is doing so. Because he is an extreme leftist, trusts that his texts are read by other extreme leftists, and believes that by suggesting that "Heisenberg was basically a Nazi", he contaminates the image of quantum mechanics or "the Copenhagen Interpretation" – which is what he really cares about.
In effect, Ball places his politics above science. This politicization of science is sick, disgusting, and must be fought against. The validity of quantum mechanics doesn't depend on your agreement with the politics of one founder of quantum mechanics or another. Get used to it, neo-Marxists.
"Copenhagen Interpretation" is anti-realist
In the third paragraph, Ball starts to dispute the claim that the Copenhagen Interpretation is non-realist:
It’s perhaps for this reason too that I think there are misconceptions about the Copenhagen interpretation. The first is that it denies any reality beyond what we can measure: that it is anti-realist. I see no reason to think this. People might read that into Bohr’s famous words: “There is no quantum world. There is only an abstract quantum physical description.”Ball claims that it's a myth that Copenhagen is anti-realist. But the terms "realist" and "anti-realist" that spread after Heisenberg's death are defined in such a way that Bohr's statement automatically implies that quantum mechanics is an anti-realist theory. Bohr's statements are really clear:
There is no quantum world. There is only an abstract quantum physical description.Bohr says that the task of physics – which used to be "find all the numbers that objectively describe the state of Nature, and the laws that objectively govern their evolution" – is no longer enough to do physics. That was the framework underlying classical physics. But quantum mechanics has to use a more general framework, one in which the task is to produce correct propositions about Nature (well, correct propositions about observables). More precisely, quantum mechanics allows us to calculate the probability that a proposition about observables will be correct, given some knowledge about the observables that was obtained in the past.
It is wrong to think that the task of physics is to find out how nature is. Physics concerns what we can say about nature.
According to Bohr, quantum physics works like the derivation of theorems in an axiomatic system in mathematics. You are given some axioms – there may be different sets of axioms etc. – and you may derive some of their implications and theorems. Different people may use different axioms – those are analogous to the initial measurements. Some people use the axiom of choice, others assume its negation etc. But quantum mechanics tells you which statements about the future measurements are true or likely to be true. That's just like the ability of mathematics to tell you which theorems you may derive from a given set of axioms. But your conclusions about the truth values of propositions always depend on some assumptions – on the axioms.
So in quantum mechanics, Bohr clearly says, you can no longer assume the objective existence of some facts about Nature. You may still say that "Nature exists". But you must be careful to understand that this statement must be interpreted in a very weak way so that it's basically vacuous. Nature may exist but no data describing the current state of any objects may be assumed to have objective values that would be independent of the observers. Ball pretends that Bohr's compatibility with some vague form of the statement "Nature exists" is enough for him to be "realist". But in this foundational quantum context, the term "realist" has been given a rather clear definition – the assumption that the framework of classical (observer-independent) physics is OK in principle – and a vague version of "Nature exists" simply isn't a sufficient condition for one to be considered "realist". Ball shows his ignorance of facts or definitions – or a deliberate distortion of the truth – if he claims that some very weak statement "Nature exists" is enough for Bohr to be a "realist".
Instead, according to Bohr, what matters is that "particular quantitative facts about objects in Nature" only exist to the extent to which they were observed. And observations cannot be identified as observations objectively, either. It's very clear that this is what Bohr and Heisenberg meant – and it's very clear that they were right and this is how physics works and has to work. We can find quotes that make it clear that this is what they have always meant.
In the comment section, Becker quotes Niels Bohr as talking about
"the impossibility of any sharp distinction between the behaviour of atomic objects and the interaction with the measuring instruments which serve to define the conditions under which the phenomena appear."Becker and other anti-quantum zealots only know this sequence of Bohr's words because it was quoted in a text by John Bell. They are not the first generation of anti-quantum activists. They're about the third or fourth generation – and they have read many more texts written by activists such as John Bell than texts written by physicists. So all their "knowledge" about physics has gone through anti-scientific, mostly Marxist filters installed by demagogues and pseudoscientists such as John Bell. They only know what Marxists have said about science. They don't know any science by itself and they haven't read any texts by the actual physicists. But they deliberately obfuscate this fact and use the term physics even though they actually mean a Marxist critique of physics. Why do they do so? Because "physics" sounds more prestigious than "Marxist critique of physics". But they're doing the latter, not the former.
At any rate, what does Bohr's statement above say? It's very clear. It says that the only way to say something about the properties or behavior of atomic objects is to measure them with an apparatus. These two processes – the "actual" behavior of the atomic objects and what we "see" when we observe them with an apparatus – cannot be separated. The properties of atomic objects (and all objects evolving according to quantum mechanics, which means all objects, at least in principle) may only be studied through the measurement. There are no particular quantitative facts about the "behavior of atomic objects" that would exist without the measurement by an apparatus.
On top of that, Bohr's sentence clearly says that there's no objective line (Heisenberg cut) that could say what the measurement is and what the measurement isn't. So any effort to "objectively define" the measurement is bound to depend on the observer's approach. There's always some freedom in the way how the observer divides processes to "processes of the external atomic objects" and "the measurements of them". This freedom is an important fact about Nature and it's just foolish to fight against the facts of Nature, to try to reform them, or to be annoyed by them.
The observer must decide where the Heisenberg cut is, he must decide what he will be able to perceive, what observable coming from a future measurement he wants to be predicted, and quantum mechanics can do this prediction – by spitting the probabilities of various outcomes (allowed outcomes are the eigenvalues). In principle and in general, different observers ask different questions – they probe the same "Nature" in different, complementary ways. What is incomplete or incomprehensible about any of these things?
But just like Heisenberg's views are being attacked by these demagogues by misinterpreting his links to Nazism, Bohr's views are being attacked by these aßholes by constantly repeating that he was vague and he was guru in a cult. For example, Becker writes:
But more generally, I am loath to ascribe positions to Bohr. He really was unclear. His students said he spoke of a complementarity between clarity and truth, and thus Bohr's seeming incomprehensibility was merely the result of his concern for the truth.Bohr wasn't unclear enough so that one could doubt the conclusions above. Concerning the complementarity between clarity and truth, it's partially a metaphor – a playful usage of "complementarity". But to some extent, it's more than a poetic metaphor. While clarity and truth aren't really physical observables so this kind of "complementarity" doesn't seem like a full-blown special example of the complementarity between different descriptions, there is a valid point here.
As you can see, the anti-quantum zealots simply find the statements of the kind "Nature ultimately operates according to the laws of classical physics i.e. works with objective data that are independent of observers" to be "clearer". The only problem with that proposition is that it is completely wrong. The people who implicitly assume classical physics are asking the question: "What are the basic classical observables that Nature uses? And what are the equations by which they evolve?" It sounds like a clear question and they expect a clear answer. However, this question has no clear answer except for a "disappointing" one: There are no classical observables in Nature (except for constant \(c\)-numbers).
This very statement – that Bohr couldn't give a simple, particular, straight answer about the "right classical observables" – made his actual answer "less clear" according to those who asked the question. But he had to give this "less clear" answer because the "more clear" answers are just untrue. So there's a trade-off between "clarity" and "truth" here – simply because the untrue answers would look (and, therefore, "be", because even in quantum mechanics, things "are" the way they are "observed") more clear than the true ones.
Why would you use the witticism about the "complementarity of truth and clarity" against Bohr, Heisenberg, or their understanding of quantum mechanics? It's pure demagogy. It's a nice witticism but it's clearly not a serious example showing how complementarity is involved in the discussion of physical situation because general discussions about truth and clarity are philosophical and not physical topics.
Human languages haven't been evolved to optimally discuss "esoteric" phenomena and laws such as the laws of quantum mechanics. So it's clear that no sentences in human languages have ever captured the essence of quantum mechanics completely and universally comprehensibly. The inappropriateness of human languages for quantum mechanics is also the reason why many people felt they disagreed with each other – even Bohr and Heisenberg did. And even the propositions that were important and insightful turned out to be highly non-unique. There have been many ways to express the same rules. One may talk about observers or consciousness or measurements or observations or dependence on the observer or other things – but at the end, this novelty of quantum mechanics relatively to classical physics is always exactly the same despite the fact that some of the words "offend" some of the listeners more than others.
At the end, lots of people are just too stubborn or too stupid to understand that quantum mechanics really requires one to abandon the classical thinking. They still assume classical physics and want to add some extra structure within classical physics. While choosing the additions, they care about the differences between words in human languages whose differences have nothing to do with what is actually needed to understand modern physics. They have made their decision to reject modern physics at the very beginning. The most influential ones among them have also made the decision to learn "physics" from Marxist activists instead of physicists.
And they work hard to increase the Marxism-to-science ratio which is why the number of texts such as Becker's book and (somewhat less offensively) Ball's book keep on increasing and why the true heroes of science such as Bohr and Heisenberg are always getting worse press than a year ago. It's because much of the media and publishing industries has been conquered by Marxist šitheads who care about their pathetic 19th century ideology much more than they care about science and its profound insights.