Following suggestions from Mike Wiest in his comment on this post, I’ve been reading more on efforts to invoke quantum physics in explaining life. Below are my thoughts following my reading of Mae-Wan Ho’s The Rainbow and The Worm: The Physics of Organisms.
This is an engaging and thought-provoking book, extremely dense with information and ideas running from accepted science through increasingly speculative extrapolations and concluding with some free-form philosophizing. This book was published in 1993, with the second edition I read coming in 1998. Ho, who was trained as a biochemist, has since been involved in leading an organization called the Institute of Science in Society, and her more recent writings tend toward public policy.
The early sections of Ho’s book discuss life in thermodynamic terms. I was broadly familiar with the idea that life utilizes energy flow to build and maintain high levels of structural organization far from equilibrium. In several steps, and citing work of other scientists, she builds a case that explaining life in detail strains the traditional thermodynamic picture (which assumes microscopic homogeneity). She says intricately organized living things utilize molecular systems which transfer energy without thermalization (zero entropy growth). Energy is stored and used at the electronic level, not the thermal level. But how can these micro-level energy exchanges operate across the macroscopic dimensions of the organism? Ho says stored energy can amplify weak signals across larger distances.
Throughout these early chapters, Ho uses the word “coherent” to describe the (non-thermal) energy storage and transfer within the organism (she says stored energy is by definition coherent energy). She will come back to this idea later in the book and explicitly argue that it must involve quantum coherence specifically.
The energy we’re talking about is electromagnetic. We know electrons move quickly and in organized fashion through crystals and super-cooled materials (superconductors). Could something like that be happening in the organism (despite the high temperature)? Ho uses the example of a solid state laser where energy flow induces a quantum phase transition which can take place very rapidly. She sketches how this might occur in living tissue and discusses the idea that cells could be solid state systems.
In a later chapter Ho leaves aside the solid state system model of the organism in favor of specifically identifying it as a liquid crystal system. She became convinced of this in part by examining fruit fly larva under a polarizing microscope. The title of the book comes from the colorful organized patterns she detected. She believes the type of organization seen is evidence that organisms are essentially liquid crystals.
What other evidence is there that organisms are coherent systems? A piece of possible evidence is in the analysis of the electro-magnetic fields emitted by organisms. It seems well supported that organisms do generate weak electromagnetic fields, and are in turn sensitive to external fields. Ho cites the work of Fritz Popp and colleagues who have analyzed the emission of light (“bio-photons”) from organisms such as fruit fly embryos. (A list of Popp’s publications can be found here). The pattern of photons issued in response to stimulus is said to be consistent with non-classical coherence. This may lend some credence to the idea that a coherent field may be providing organization to the organism.
Ho has a chapter toward the end of the book on quantum physics. She summarizes the familiar phenomena of quantum entanglement and coherence (2 slit experiment, EPR, etc.). Then she tries to convey why the ideas and arguments of the preceding chapters lead her to conclude it is indeed quantum coherence (superposition of states, non-local entanglement) which prevails in the organism. But has she made the case? In a key passage she says:
“I have been presenting heuristic arguments throughout many of the preceding Chapters on why the wholeness of organisms has to be understood as quantum coherence.”
This is followed by a brief summary of some of the earlier ideas; then:
“By far the most persuasive argument for quantum coherence, to my mind, is the nature of the coordination that is achieved in the organism, where every single part…is able to work autonomously while keeping in step and in tune with the whole.”
I think she is conceding that her case, which is admirably detailed and suggestive, is ultimately circumstantial. Now, criminals are convicted every day by circumstantial evidence, so I don’t mean to be dismissive here. But for the mainstream scientific community to get on board, we’ll need more.
As Paul Davies said, we need a secure experimental result which demonstrates a biological system clearly exploiting non-trivial quantum effects.
One area I do want to follow up on is this idea of an organism or cell as a liquid crystal. Saying something is a liquid crystal is not the same as saying it is coherent in the quantum sense. But liquid crystals and other phenomena of condensed matter physics demonstrate intriguing properties. And the scales at which these occur is small enough require quantum as well as classical theoretical tools to investigate. The emergent features found in some of these systems (some discussed in Robert Laughlin’s A Different Universe, which I discussed in this post) are mysterious in their own right, and if biological systems do exhibit characteristics of some of these, that would be very interesting to investigate.