I liked Rosenblum and Kuttner’s (R&K) book Quantum Enigma and Mermin’s review of it [Am. J. Phys. 75(3), 287–288 (2007)], but I disagree with both in fundamental ways.

R&K’s main contention, that conscious observation is required for a complete quantum measurement, is a groundless and unnecessary extravagance. For example, a photon making a permanent mark on a photographic plate is surely a quantum measurement, even if nobody is around to look at it. Once the mark is made, an observer can read it years later, or never, and the mark is still there in any case. To question the reality of such a mark is like questioning the reality of any other macroscopic object, such as the moon. It’s an unnecessary extravagance to assume that consciousness is required.

The authors’ answer seems to be that a human brain is needed because, when the photon makes its mark, the plate...

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