Review: Cosmic Evolution
Eric Chaisson's book Cosmic Evolution takes a grand look at the nature of change in our universe. It proposes a universal theory of change, whereby Darwin's theory of natural selection is expanded to encompass all of physical change. Despite the woo-woo sounding title, the book takes a relatively rigorous look at how physical laws influence change over time, and it provides a helpful framework for considering Darwinian process taking place beyond biology.
The book is centered around a discussion of the second law of thermodynamics, which states that any given system will trend towards a state of higher entropy, or disorder, over time. Taken at a glance, this law seems to conflict with our everyday experience. We seem to be living in a world where things get more ordered with time: life has gone from single-celled organisms to the complex array of plants and animals that cover the earth today; our cities are continually getting bigger and more organized; and our societies have become exponentially more peaceful than those of our stone-age ancestors. This apparent contradiction is resolved, however, by noting that while local events can become more ordered--for example by natural selection--this order comes are the expense of an equivalent amount of disorder being created globally. So while the laptop I'm typing on right now is highly ordered, this order comes at the expense of all the energy it took to mine the minerals and create the electricity that power it--the net effect being a slight increase in disorder. This principle has some interesting, and somewhat frightening, implications for our civilization. While technology many advance and our cities may grow, this growth will always come at the expense of an increase in disorder in the universe at large.
To understand the nature of change at a universal level, you first have to consider how the world was created and how it has changed over time. To the best of our current scientific knowledge, the universe was created during a big bang event, after which all the energy in the universe started to rapidly expand. The exact geometry and fate of our universe is still a mystery, but we do know that the universe could evolve in one of several possible ways. Our universe could keep expanding infinitely into the future, or we could live in a universe where gravitational forces will eventually overtake that expansion and our universe will collapse in on itself. Existential mysteries aside, this explanation provides a scaffold for us to understand how our universe started changing beginning in the earliest microseconds of its existence all the way to our current point in time.
In the beginning, there was no matter--only incredibly hot and dense radiation. After the universe started expanding, however, some of that radiation began to convert into matter, first as sub-atomic particles, which were briefly born and then destroyed in the intense heat, and later as more durable stuctures such as elements and molecules as the universe cooled. This transition from radiation to matter was thus the most important example of evolution in the early universe, if not of all time. While it might seem like were are living in a world made entirely of matter, we are in fact living in a world everywhere permeated by cosmic background radiation left over from the time when the universe was entirely made of radiation.
Entropy in a system must always increase, but at the same time negative entropy--so-called negentropy--can also increase. How is this possible? According to cosmologists like Chaisson, it is possible because this universal expansion allows the maximum possible entropy in a system to increase over time. In the beginning everything was dense and uniform. The flow of energy involved in expansion caused temperature gradients to form between various parts of the early universe, which were the earliest signs of order. Expansion caused matter to become clumpier, and this set off the chain of events that resulted in galaxies and life and all of the sources of order we see around ourselves in the universe.
This expansion also creased flows of energy, which Chaisson concludes are the ultimate drivers of evolution. These flows, which he calls free energy rate density, are what sustain organized complexity. They are also quantifiable, and for each rung in the evolutionary ladder you can see a trend towards greater energy throughput. Chaisson provides a few back-of-the-napkin calculations illustrating this point, and it seems to have some merit, but it seems like further study is necessary before reducing all evolution down to this one constant. Nevertheless this book is a great example of cross-disciplinary big-picture thinking, and worth a read as long as you aren't afraid of math equations.