Originally published 19 December 2000
It was one of those unexpected encounters that brighten a day: a leafless winterberry tree covered with cedar waxwings busily gobbling the scarlet fruit.
These elegant birds, with their tufted crests, flecks of red, and yellow tail-bands, can appear seemingly from nowhere and vanish almost as quickly. I counted myself lucky to see them, and stood for a long time watching their lively feeding.
I had just finished reading Eric Chaisson’s Cosmic Evolution: The Rise of Complexity in Nature, soon to be published by Harvard University Press. Where, along the curve of cosmic evolution, I wondered, lay this particular vignette of winterberries, waxwings, and human observer. In the universe of the galaxies, does the level of complexity we encounter here on Earth stand high, low, or somewhere in between? And does it matter?
Chaisson is an astrophysicist at Tufts University, who has written many popular books on science. His newest offering is concerned with “time’s arrow,” a curve of rising cosmic complexity beginning with the Big Bang and reaching — well, insofar as we know and for the time being, a brain that can appreciate the beauty of feeding waxwings.
Chaisson argues that rising complexity can be explained (or at least roughly described) by the laws of non-equilibrium thermodynamics, without any need to postulate new kinds of science or mysticism. He shows that in an expanding universe, local pockets of order will naturally arise even as the overall disorder (entropy) of the universe increases.
There is nothing new in any of this; scientists have long assumed that a growth of local complexity is entirely consistent with the laws of thermodynamics. What is most original about Chaisson’s argument is his proposal of a quantitative way to measure complexity, and to plot the course of cosmic evolution using this measure.
He invokes something called free energy rate density, a concentration of energy with respect to time and mass, and calculates values of free energy rate density for everything from stars to microchips. A graph of these values versus time reveals a rising curve that Chaisson takes to be the signature of cosmic evolution.
For example, there is much more energy flowing through a star than is involved in a worm’s metabolism. But the concentration of energy in time and mass is numerically greater for the worm (roughly 10,000 ergs per second per gram for a worm, versus 2 ergs per second per gram for the Sun).
As the universe evolves, according to Chaisson, the values of free energy rate density increase in local places: galaxies, stars, planets, plants, animals, brains, societies. Within each of these broad categories, he calculates more specific values of free energy rate density, as for example within human society: hunter-gathering, controlled use of fire, agriculture, industrialization. The curve rises as time passes.
What does all of this mean? That’s hard to say, but Chaisson’s graph of time’s arrow is certainly provocative. If nothing else it confirms in a nicely quantitative way our intuition that the universe does indeed breed complexity, and apparently in ways that can be usefully described with the language of modern physics.
If we accept Chaisson’s analysis, at least tentatively, then certain conclusions follow. First, we are almost certainly not unique in the universe, because there is nothing in his account of cosmic evolution that evokes the specific uniqueness of Earth. And second, we are not the end of the line either; the curve will continue to rise, and novelty will ensue.
In fact, a glimmer of the future might already be visible. Presently, in our neighborhood of the cosmos, the top of Chaisson’s curve of cosmic evolution is occupied by — get this — the Pentium microchip (and its equivalents), with a free energy rate density of something over 10 billion ergs per second per gram. This exceeds even the human brain because microchips perform their operations so much faster than do webs of organic neurons.
Microprocessor computer chips are not as sentient as human brains, but they are more complex, by Chaisson’s definition, and represent a further step in cosmic evolution by his standard. So does the immediate future of complexity on this planet lie in dense webs of silicon transistors? Are humans merely instruments in bringing about the next step in cosmic evolution? Are there other forms of complexity out there among the galaxies with free energy rate densities in the trillions? Time will tell, although I would not be surprised if the answer to all of these questions is yes.
And in the meantime, the answers don’t at all affect how I live my life. Chaisson can assign a value of free energy rate density to winterberries, waxwings, and human brains, but the skittering feast of the crested birds on a frosty morn of early winter bowls me over with its beauty — exhilarating, uplifting, and, for all practical purposes, inexplicable.
