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59th book for 2018.

A very interesting and accessible book on quantum ontology.

With no math (!) Becker takes the reader effortlessly through nearly a hundred years of back-and-forth debate as what quantum mechanics implies about the universe we live in.

The history itself is fascinating. I had no idea (blush) that Heisenberg (of uncertainty fame) was actually a Nazi who headed the Nazi's atomic bomb project, which according to Heisenberg (postwar) was unsuccessful as he was really a nice guy who didn't want to blow up things, and according to Becker was incompetent. According to Becker, Heisenberg was actually the one who coined the "Copenhagen Agreement" in the postwar period as a way of cementing his role in the foundation of QMs and upgrading his status post-Hitler, and by doing so made it seem there was a standard interpretation when there wasn't.

Einstein (who I had been raised to think of as just never getting QM) comes across as particularly sharp in his critique, and was concerned about the implications of non-locality that he saw lurking at the heart of the standard interpretation of QM; which is of course at the heart of Bell's inequality theorem. QM's grandfather Bohr comes as a bit of an arsehole, stopping any dissent into his standard positivist interpretation of QM. His waving away of the measurement problem, of there being two worlds (a QM world of the small, and a classical world of the big), can be seen in retrospect as incoherent and vastly damaging to the field.

(If I understood things correctly) Einstein's major concern with the Copenhagen Interpretation of QM was that not only were a particle's properties (momentum, energy etc) unknown until the collapse of QM wave function, they in didn't exist according to the Copenhagen Interpretation until that point. Einstein saw that this led to two possibilities: either QM was incomplete and these properties existed but were unmeasurable (i.e., there were "hidden variables - God doesn't play dice!) or the nature of the properties was fixed at the time of measurement (i.e., the Copenhagen Interpretation). If the latter, this would in turn imply that in certain situations (i.e., where particles were quantumly entangled) information about these properties would be transmitted instantaneously (i.e., faster than the speed of light and locality would fail). Naturally Einstein preferred the situation where QM was incomplete and locality was upheld.

David Bohm, later derived a model of QM that was completely consistent with the maths of the Copenhagen Interpretation, but did involve hidden non-local variables (i.e., at any particular moment a particle has a definite momentum, energy, spin etc). As a bonus this Bohmian interpretation gave simple explanations of classic problems like the double-slit experiment, as well as QM entanglement, but perhaps because it involved non-locality (or because it contradicted the Copenhagen Interpretation) was largely dismissed and forgotten.

Hugh Everett, looking for a quick doctoral topic, decided to avoid the measurement problem altogether by supposing the wave function never collapsed, and thereby developed what has become known as the Many Worlds interpretation of QM. Naturally his work was also ignored by the physics establishment at the time, and he had to radically reedit his thesis in order to pass.

Later John Bell (a particle physicist at CERN, who by his own account worked on QM foundations on Sundays) developed a theoretical test to see if local hidden variables could exist within QM. His paper, published in an obscure journal, was eventually tested years later at Berkeley for the first time in the early 1970s, and showed that non-locality was upheld (i.e., there were no local hidden variables - God does play with dice!). What this means for the World is hard to get your head around, and I join my better Einstein in thinking this is a very weird result indeed. It is shocking to learn that the postdoc who did these brilliant experiments, was unable to get tenure afterwards, because this work was regarded as quasi-worthless by the general physics community in the 1970s.

In an irony of fate, this very non-locality is the very basis for modern quantum computing.

Strongly recommended.

5-stars.