Reexamining “Free Energy Rate Density” as a Complexity Metric

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Cosmic Evolution, by Eric J. Chaisson is arguably one of the original “core” texts of big history. Despite being published over 20 years ago, it is still relevant for its explanation of the cosmological and thermodynamic underpinnings of the evolution of complex systems over the span of time. It was also a pioneering work because it proposed that we can quantify the degree of complexity of systems by determining the quantity of the “free energy rate density” or FERD (abbreviated as “Ωm” in Cosmic Evolution) that flows through a system. Although Chaisson advises that his correlations of FERD to complexity degree is subject to various limitations and generalizations, careful analysis of the arguments and examples used to support FERD indicates that it is even less likely to be as reliable and quantifiable than he purports for at least the following reasons:1. The author offers a relatively short list of criteria for a system to qualify being “complex” that in turn results in the inclusion of systems that are not classified as complex by usual criteria. 2. Free energy rate density is not compared against other complexity metrics and subsequently seems to serve as its own “gold standard.” The lack of comparisons results in a tautological argument and sometimes questionable conclusions.3. The argument for FERD sometimes deviates from the hypothesis that FERD is a good way to measure the degree of a system’s complexity to a claim that it also measures complex functions and structures as well. 4. The FERD that he reports are often actually for the total energy flow through a system. Hence, a much more efficient complexity might only appear to be less complex. 5. Complex systems have many variables that can confound attempts to make reliable and precise generalizations, including good metrics for their degree.