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Does Quantum Theory Explain Consciousness?
astroengine writes "Quantum theory is often seen as the root cause of unrelated, mysterious phenomena. Take consciousness for example. British physicist Roger Penrose recently argued 'that we will need to invoke 'new physics and exotic biological structures': rewriting quantum theory to make sense of consciousness.' But why do this, especially as there is no apparent causal link between quantum mechanics and the conscious mind? There appears to be a very basic logical fallacy here that even the most prominent physicists seem to be making."
Quantum chemist here (my username's a hint at that), and I couldn't agree more. I fight against this nonsense all the time.. You'd think that if there was anything to it, we'd be all over it - since explaining chemistry and biochemistry in terms of quantum mechanics is exactly what we do. But nope, I don't know anybody in the field who thinks those ideas have any merit whatsoever. (And let's just point out that as merited a guy Penrose is, he's not a quantum chemist, and more a mathematician than a physicist. His main area of expertise is topology, which has applications in cosmology but is totally unrelated to this area)
It breaks down like this: Electrons in atoms and molecules behave entirely quantum-mechanically. It's why QM was invented in the first place. Since chemical properties are the result of how the electrons behave, all of chemistry is intrinsically quantum-mechanical in some sense.
However: Molecules as a whole do not act quantum-mechanically. They move about according to classical mechanics - and that's how we model them physically too. Because once things get as heavy as an atomic nucleus (save for hydrogen, under some circumstances), their quantum 'uncertainty' in position etc is so small that it's chemically insignificant. So you need QM to describe how two atoms are bonded, but classical mech does a good job of describing how the molecules as a whole bounce around.
So the question is: Are there 'non-trivial' quantum effects in biology? I.e. ones that aren't explainable in terms of 'ordinary' chemistry (which is still ultimately quantum-mechanical). There are a few examples, such as magnetoreception in birds, and energy transfer during some photosynthetic processes. But: despite a lot of the hype surrounding them, these things are still dealing with individual, sub-atomic particles. They don't cast any doubt on 'conventional wisdom' that QM phenomena don't happen at the biological scale. There's nothing in the cell that depends on the actions of a single small molecule, or a single chemical reaction, or anything that's small enough to act quantum-mechanically.
The physics here doesn't make sense (Penrose's ideas in particular don't even hinge on established QM, but rather his own speculative ideas about quantum gravity.. of all things), we have every reason to believe you wouldn't have quantum phenomena at that scale in that environment, and no reason to believe otherwise. The chemistry doesn't make sense, as there's basically nothing hitherto found in biochemistry that doesn't fit into established chemistry. (Which isn't to say biochem hasn't expanded the boundaries of established chemistry, but it hasn't changed the foundations at all) And the biology doesn't really make sense, as cells are not built anything like Geiger counters, sitting in a labile state waiting for a single sub-atomic event to trigger them.
Finally, the philosophy doesn't really add up either. The quantum-consciousness people seem to have an agenda along the lines of 1) QM is non-deterministic 2) If the brain's higher functions rely directly on QM processes, then the brain is non-deterministic 3) That nondeterminism means we have free will.
Little of that makes sense to me. (1) is in fact a matter of which interpretation of QM you choose, and ultimately a question of metaphysics, since any non-deterministic theory could be postulated to be the result of a deterministic underlying 'reality' (as is the case with the Bohm interpretation of QM), or vice-versa. (2) is unwarranted speculation and (3) especially doesn't make much sense to me, since the philosophical question of 'free will' tends to hinge on whet