In ahem, certain quarters, one now and again overhears (oversees?) speculations about the relationship between entropy and biology, speculations that can likely trace their roots to Schrödinger's 1944 book What is Life?


Hence the awkward expression 'negative entropy' can be replaced by a better one: entropy, taken with the negative sign, is itself a measure of order. Thus the device by which an organism maintains itself stationary at a fairly high level of orderliness (== fairly low level of entropy) really consists in continually sucking orderliness from its environment. This conclusion is less paradoxical than it appears at first sight. Rather could it be blamed for triviality. Indeed, in the case of higher animals we know the kind of orderliness they feed upon well enough, viz. the extremely well-ordered state of matter in more or less complicated organic compounds, which serve them as foodstuffs. After utilizing it they return it in a very much degraded form - not entirely degraded, however, for plants can still make use of it. (These, of course, have their most powerful supply of 'negative entropy' in the sunlight.)

what-is-lifep. 73–4

The argument here hinges on the observation that living organisms are able to maintain homeostasis, that is, a relatively stable set of biologically favourable internal conditions in a physical environment that otherwise have brought it into swift thermodynamic equilibrium with its surroundings. Schrödinger in fact goes as far as to claim it as the characteristic feature of life

What is the characteristic feature of life? When is a piece of matter said to be alive? When it goes on 'doing something', moving, exchanging material with its environment, and so forth, and that for a much longer period than we would expect an inanimate piece of matter to 'keep going' under similar circumstances.

what-is-lifep. 69

By the time we get to the footnotes, Schrödinger starts back-tracking and saying that he should really have framed the discussion around free energy instead. (But then parries again by invoking Boltzmann?)

The remarks on negative entropy have met with doubt and opposition from physicist colleagues. Let me say first, that if I had been catering for them alone I should have let the discussion turn on free energy instead. It is the more familiar notion in this context. But this highly technical term seemed linguistically too near to energy for making the average reader alive to the contrast between the two things. He is likely to take free as more or less an epitheton ornans without much relevance, while actually the concept is a rather intricate one, whose relation to Boltzmann's order-disorder principle is less easy to trace than for entropy and 'entropy taken with a negative sign', which by the way is not my invention. It happens to be precisely the thing on which Boltzmann's original argument turned.

what-is-lifep. 74

His interlocuter in the footnotes, a certain F. Simon, seems a wise and prudent friend—to the extent that it's usually easier to sound wise when trying to poke holes in another's arguments than in trying to fully articulate our own. As he puts it, if the point of all this masticating is to extract order from our surroundings, why should we not be crunching on the highly ordered crystalline structures of solid rock, rather than the heterogeneous organisation to be found in soft piths of celery or in juicy legs of chicken?

All this certainly seemed a neat idea to me at some point—perhaps too neat, the way such a definition of life slots into the conception of orderly, rational man being at the top of the heap, fighting his inexorable battle against the chaos all around. And a little passé, by machine-age standards, where the spontaneous mess of serendipitous encounters has come to pervade our sense of what it means to be alive—and the orderly inflexibility of machine-abetted bureaucracy, its anti-thesis.

Update [2021-06-01]

There is a probable confusion here of "informational entropy" and "thermodynamic entropy", cf Schrödinger's claims were cited as well by Penrose in emperors-new-mindch. 7, confusingly enough. According to post, dead bodies have lower (thermodynamic) entropy than live ones (contra "maintenance of low entropy" according to Schrödinger).

I'm just going to clip this last excellent bit here that's especially germane:


The context of this discussion is mis-application of the Second Law of Thermodynamics to systems that might appear to exhibit entropy differences in the form of orderliness of macroscopic arrangements of matter. But many of these “intuitive” cases of entropy differences translate to little or no thermodynamic entropy differences, and therefore do not fall under the jurisdiction of the Second Law.

Simpler statements that are consistent with the laws of thermodynamics and bear on our societal options are:

  1. Energy may be extracted when temperature differences exist (e.g., combustion chamber compared to ambient environment; solar surface temperature compared to Earth surface). Entropy measures of the energy itself are not meaningful.
  2. Net energy from fossil fuels may only be extracted once.
  3. Efficiencies are capped at 100%, and often are theoretically much lower as a consequence of the Second Law.

The most hilarious bit of the post: "It is said that when a group of scientists discusses entropy, they’ll be talking nonsense inside of ten minutes. I think we managed to steer clear of this common peril."

To chew on a bit more: the Boltzmann conception of entropy that led to this muddle.


emperors-new-mind Penrose, Roger. 1999. The Emperor's New Mind: Concerning Computers, Minds, and the Laws of Physics. Oxford University Press. ↩︎ 1

what-is-life Schrödinger, Erwin. 2012. What Is Life?: The Physical Aspect of the Living Cell ; With, Mind and Matter ; & Autobiographical Sketches. Cambridge University Press. ↩︎ 1 2 3