Emergent Ideas

My conference talk went reasonably well and provided me the opportunity to engage in some thought-provoking conversations.

One title that came up is Nobel laureate Robert Laughlin's A Different Universe. The book contains some provocative ideas that sound promising, but need to be fleshed out more.

The book wanders off on many tangents, but the central theme is that the laws of physics are "emergent." Emergence means that the organization of a particular system cannot be deduced from lower-level laws. For example, a biological system is in some way independent of the minutiae of its chemistry and physics. The term itself is poorly chosen, as it seems to imply that organization bubbles from "below," when actually the term signifies that organization comes from somewhere (anywhere) else (perhaps from "above" or from the whole collective). I think of the term as a verbal fig leaf for reductionists—their last grasp on science is semantic. A better term is needed badly. For now I'll just put emergence in quotation marks.

The clearest examples are in biology:

Life is especially fun to talk about from a physical perspective because it is the most extreme case of the emergence of law. In fact, the entre idea of emergence was invented by biologists to explain some aspects of living things—the rodlike shapes of some bacteria, for example, or the tendency of bunnies to run away from foxes—are stable and reproducible, while the microscopic laws of chemistry from which they descend [wc] are random and probabilistic. (158)

The stability of large systems (insensitivity to low-level perturbations) also creates a barrier of unknowability. As Laughglin puts it, "The machinery of life is rendered inaccessible by the very physical principles central to its function" (166).

Thus the presenter of a paper reports writing a computer program based on fictitious laws of motion for the atoms, and then using this program to predict the shapes of proteins from the unerlying DNA sequence. that this strategy works at all (which it does some of the time) indicates that the particular protein's folded up structure does not depend sensitively on the details of the interatomic forces, since if it did, one would have to implement a correct solution of the correct equations of motion. Yet if one asked these same people, or their grant monitors whether they believed universal principles were at work, so that one could speak sensibly of "hemoglobinness" or "ribosomeness," most of them would say no. (171)

Between these extremes [scientific view that life is just chemistry vs. mystical view that life is fully unknowable] we have the profoundly important, but poorly understood, idea that the unknowability of living things may actually be a physical phenomenon. This does not make life any less wonderful, but simply identifies how its inaccessibility could be fully compatible with reductionist law. (173)

Laughlin is a solid state physicist. His specialty is statistical phenomena, so he might be said to have a bias when he puts collective phenomena as more fundamental than "fundamental" field theories like String Theory.¹ Laughlin boldly extends "emergence" to the laws of physics:

Newton's legendary laws have turned out to be emergent. They are not fundamental at all but a consequence of the aggregation of quantum matter into macroscopic fluids and solids—a collective organizational phenomenon. They were the first laws to be discovered, they brought the technological age into existence, and they are as exact and true as anything we know in physics—yet they vanish into nothingness when examined too closely. Astonishing as it may seem, many physicists remain in denial. to this day, they organize conferences on the subject and routinely speak about Newton's laws being an "approximation" for quantum mechanics, valid when the system size is large—even though no legitimate approximation scheme has ever been found. the requirement that Newton's laws emerge in the macroscopic limit was christened the principle of correspondence in the early days of quantum mechanics.... But the correspondence principle remains mathematically unprovable. (31-32)

We are accustomed to thinking of [electron charge] as a building block of nature requiring no collective context to make sense. The experiments in question, of course, refute this idea. They reveal that the electron charge makes sense only in a collective context, which may be provided by either the vacuum of space, which modifies this charge the same way it modifies atomic wavelengths, or by some matter that preempts the vacuum's effects. (18)

The myth of collective behavior following from law is, as a practical matter, exactly backward. Law instead follows from collective behavior, as do things that flow from it, such as logic and mathematics [!]. The reason our minds can anticipate and master what the physical world does is not because we are geniuses but because nature facilitates understanding by organizing itself and generating law. (209)

In this last paragraph, he seems to go too far in claiming that logic and mathematics flow from collective behavior. Were that the case, it would seem that the individuals composing the collective would not obey logic and mathematics. The fact that Laughlin doesn't seem to be aware of this problem, makes me hesitate to endorse his program. In fact one has to wonder what rules (laws) govern the interactions of particles to give rise to the charge of the electron, since that charge itself is in some sense the cause of the electromagnetic laws that we would normally claim to mediate interactions.

But the central idea is promising. It will be interesting to see what he has to say in future.

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Notes

1. Everyone favors his own field. I've said before that if trash-men specialized in writing and talking, Plato wouldn't have had the philosopher king, but the trash-man king.

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Robert B. Laughlin, A Different Universe: Reinventing Physics from the Bottom Down (New York: Basic Books, 2005).

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Physics Today has a news item about Laughlin's departure from Korea Advanced Institute of Science and Technology: June 2006 (subscription required). Here's a free article on Laughlin's replacement: MIT Professor Named KAIST President

Laughlin's Nobel Prize autobiography