Monday, April 21, 2008

SoapBoxxes, Quantum Plants, and Free Will

Hi everybody! It's been a while since I last posted here, so before I get to the meat of this post, I'd like to explain myself. About two weeks ago, I discovered SoapBoxxer, an Internet forum (ish thing), and it immediately proceeded to swallow my life whole and digest it in a warm broth of argumentative goodness. The basic premise of the site is that anyone can create an "Opinion," which consists of a binary statement (i.e. something with a Yes/No or Agree/Disagree answer), and other people vote on it. After you vote, you can comment on, argue about, or discuss the original topic and/or other comments on it. The site is new, relatively small, and full of pretty intelligent people. If you enjoy Internet argument even one fifth as much as I do, I'd recommend joining up right away. I am (of course) RealityApologist over there.

I was convinced that something good would come of my newfound addiction, and yesterday something did. Someone from SoapBoxxer pointed me toward this study about the newly discovered relationship between photosynthesis and quantum mechanics. It seems that researchers at Berkeley (yay!) have discovered a possible reason for plants' uncannily efficient use of sunlight (they're able to convert upwards of 90% of absorbed light into energy, whereas most solar panels haven't even come close to 50% efficiency yet). For a long time, how exactly they managed this was a mystery, but it seems like we've got a possible explanation now.

"We have obtained the first direct evidence that remarkably long-lived wavelike electronic quantum coherence plays an important part in energy transfer processes during photosynthesis,” said Graham Fleming, the principal investigator for the study. “This wavelike characteristic can explain the extreme efficiency of the energy transfer because it enables the system to simultaneously sample all the potential energy pathways and choose the most efficient one."

I can't stress enough how cool this is. Apparently the pigment molecules that are responsible for making the initial conversion of light energy to usable energy have a unique (so far--more on that in a bit) ability to momentarily "pause" the energy in a superposition and simultaneously explore all the possible ways the energy can be utilized. When it finds the most efficient way to utilize it, the wave function collapses into that state, and the energy gets passed on. The researchers on the project are careful to stress

For this reason, the transfer of electronic coherence between excitons during relaxation has usually been ignored. By demonstrating that the energy transfer process does involve electronic coherence and that this coherence is much stronger than we would ever have expected, we have shown that the process can be much more efficient than the classical view could explain. However, we still don’t know to what degree photosynthesis benefits from these quantum effects.

Obviously, I'm not a physicist (though reading about this stuff makes Columbia's MA in the Philosophical Foundations of Physics look mighty tempting), but it seems pretty clear that this adaptation is at least partially responsible for the very high efficiency of photosynthetic plants. Now, I'd like to take this idea a step further. What follows is PURE speculation on my part--I know there is at least one physicist in the audience, so PLEASE correct me if anything I say makes no sense.

I've discussed free will at some length on this blog, but I've spent very little time on Libertarianism (basically the view that we have free will in the traditional, robust, alternative possibilities sense). I've been dismissive of it as a viable philosophical position mostly because I haven't been able to see any scientifically plausible way that it could be true--most people who argue for it these days do so through an appeal to quantum mechanics, but are unable to describe how the brain might inherit the indeterminacy inherent in QM without also inheriting the randomness. This is a problem, of course, because random actions are no freer than determined ones--in order for us to really be "free" in a Libertarian sense, we have to be able to choose from multiple different paths without that choice being a random one.

Now the speculation: if chlorophyll can do this, why not the brain? If these researchers are correct, plants have evolved a mechanism to explore multiple quantum states at the same time before collapsing into the most beneficial one--what if our brains are doing something similar? Obviously, the mechanism would need to be far more complex than that involved in photosynthesis (making a rational choice doesn't seem to be just a matter of collapsing into the lowest energy state), but still: this research seems to lay some exciting groundwork for further exploration of the biological utilization of quantum mechanics. If our brains were somehow able to do something similar to this, it could potentially allow for quantum indeterminacy without quantum randomness--all possible quantum states would be open to us (indeterminacy), but which state we "collapsed" into would be dictated by something other than chance (not randomness). I'm very excited to see where this goes.


Chris Jackson said...

I totally forgot about your blog, and just spent the last 30 minutes or so catching up, which was quite enjoyable. Hopefully you’ll keep it going through grad school so those of us unfortunate enough not to be going to (the right type of) grad school can get some much-needed philosophical insight while studying some b.s. like contracts or property law.

I also had some thoughts on this post: props for not equating quantum indeterminacy with free will. Way too many people (including some idiotic math professors @ Princeton) seem to think that merely by showing that human actions are governed by quantum mechanics, we can assert that we have free will in the strong sense. But as you rightly point out, the fact that our actions aren't deterministic doesn't mean we have free will--we could just as easily be acting randomly.

And it's for that reason that I'm not sure this scientific discovery about photosynthesis helps the libertarian much. Let's grant for the sake of argument that the same kind of mechanisms that govern how plants photosynthesize govern the way humans act, i.e. that there's some kind of mechanism in our brains which considers all possible quantum states (or whatever the proper term is), and then chooses which quantum state to occupy not because of its energy level, but on some other criteria.

I should point out that this is a pretty specific picture that makes some strong claims about human behavior and neuroscience. That isn’t to say it couldn’t end up being right, but I’m not sure at this point we have good reason to think the manner by which plants convert sunlight into usable energy is similar to the way humans make choices about how to act. The libertarian has to show not just that some state of affairs which allows for free will could be true, but that it actually is true.

But more importantly, back to assuming that there is some x-factor determines the quantum states of our brains’ particles, and that that factor is related to human action, one of three statements must be true: (i) that x-factor never determines human behavior, which we’ve ruled out by our assumption; (ii) that x-factor always determines the quantum states of our brains’ particles, in which case our actions appear to be determined just as if classical physics is true, leaving no room for free will; or (iii) that x-factor sometimes, but not always, determines the quantum states of our brain particles, in which case there has to be some other mechanism which determines when that x-factor determines the quantum states of our brain particles and when it does not. In other words, there has to be another factor which determines when the x-factor is determinative. Besides the fact that there doesn’t appear to be a plausible candidate for that x’-factor, all we’ve done is pushed the libertarian problem back one iteration.

OK, that was much longer than I intended it to be, but it was either that or work, and work is less cool than philosophy.

Anonymous said...

From plants to bees: the trail just seems to be getting hotter..