Physicist Amok

To start, a question: why are the expositions of Landau and Lifshitz compelling? Here are ten volumes, without data. Compare them to any number of disastrous texts with an equal amount of data. Why does Landau & Lifshitz leave us credulous and so many others make us peery?

I think the answer is physical intuition. Chapters one and two of Mechanics set forth are a reference on physical intuition. A physicist believe the world has this shape, or one near to it, no matter what object we embed. For the next four volumes we get physics justified only from this intuition, and then the first chapter of volume 5 - Statistical Physics - hammers in the next piece of intuition: here is how many particles behave. The road forward is probabilistic.

These are the preconceptions a physicist carries with him into biology, where at first they seem to fail him. Some physicists become cynical and jettison this baggage (often at the behest of some biologists). Others refuse and build models that fail, fail, and fail again.

Step back for a moment. Imagine a physicist who has internalized the intuition in Mechanics but not in Statistical Physics. What is his fate? Feynman tells us (Feynman Lectures on Physics, vol.1, p.39-2):

“Anyone who wants to analyze the properties of matter in a real problem might want to start by writing down the fundamental equations and then try to solve them mathematically. Although there are people who try to use such an approach, these people are the failures of the field; the real successes come to those who start from a physical point of view, people who have a rough idea where they are going and then begin by making the right kind of approximations, knowing what is big and what is small in a given complicated situation.”

In other words, don’t neglect the first chapter of Landau and Lifshitz, vol.5.

What must we bolt onto our intuition to handle biology? The key is in Dobzhansky’s statement “Nothing in biology makes sense except in the light of evolution.”

A biologist tells a physicist, “When you have enough of X, this happens.” The naive physicist takes this literally: there exists a concentration of X at which something physically happens. But the mechanism in question probably exists in several related species, from different environments, all of which rely on similar versions of X. X probably is transcribed at different levels, into a different environment, and yet the system functions roughly the same.

More importantly, the system had to evolve, and the system had to function in all the environments leading up to the present. This is what we must add to our intuition. Exact fixed points and thresholds don’t happen. Now when we hear, “When you have enough of X, this happens,” from a biologist we filter it to, “In a bunch of organisms and places, some level of increase of X causes this to happen.” We do this with (as-is) absurd statements about mechanics and ensembles of particles every day.

This can be made rigorous in the same way as the pieces of Landau and Lifshitz. I suspect that evolutionary game theory of some form may be the proper language to express this.