In the 1920’s, after centuries of dispute over whether light is a wave or particles, Bohr devised the compromise that holds today, that they are complementary views, so both are true, and nothing better has been found since:
“…nobody has found anything else which is consistent yet, so when you refer to the Copenhagen interpretation of the mechanics what you really mean is quantum mechanics.” (Davies & Brown, 1999), p71.
This don’t ask, don’t tell policy lets a photon be a wave when we don’t look, as long as it’s a particle when we do, so physics can use particle or wave equations as convenient. In no pond do rippling waves behave like particles, and on no pool-table do billiard-ball particles behave like waves, but Bohr managed to sell the big lie [Note 1] that light is a wavicle as Gell-Mann noted in his 1976 Nobel Prize speech:
“Niels Bohr brainwashed a whole generation of physicists into believing that the problem (of the interpretation of quantum mechanics) had been solved fifty years ago.”
Bohr’s interpretation of quantum theory was that it can be true for equations but not in reality, so physics can use it to calculate results without believing it exists. Figure 3.4 shows the options available to interpret quantum theory. The first is physicalism, that only the physical world exists, so there are no quantum waves (Figure 3.4a). Physicists who use quantum waves that don’t exist to predict the future are then like shamans who use spirit messages that don’t exist to do the same.
Bohr avoided the criticism that physics is like shamanism by making the quantum world real in equations but not actually real. This double-think let the quantum world exist for the purposes of physics, so it in effect somehow co-exists with the physical world (Figure 3.4b). This quantum-physical dualism, like Descartes’s mind-body dualism before it, is then a mystical marriage of convenience between incompatible domains.
In public, Bohr accepted quantum theory but in private, denied that the quantum world existed at all. He accepted its benefit to physics while denying what it meant, but that its events can exist for the equations of physics was an admission of failure not a theory success (Audretsch, 2004), p14.
In contrast, the quantum realism interpretation is that physical events are a subset of quantum events (Figure 3.4c), so classical mechanics is a subset of quantum mechanics. Instead of the quantum world existing to serve the physical world, it is the other way around, but what then is it?
Note: A “big lie” is a statement so outrageous that people think it must be right or it wouldn’t be said.