Why Everything in the Universe Turns More Complex

The article talks a lot about biological evolution, but in that case the only claim that is likely to be true is that the complexity of the entire biosphere increases continuously, unless a catastrophe resets the biosphere to a lower complexity.

If you look only at a small part of the biosphere, like one species of living beings, it is extremely frequent to see that it evolves to become simpler, not more complex, because a simpler structure is usually optimal for constant environmental conditions, the more complex structures are mainly beneficial for avoiding extinction when the environmental conditions change.

The book describes "Assembly Theory", a theory of how life can arise in the universe. The idea is that you can quantitatively measure the complexity of objects (especially chemicals) by the number of recursive steps to create them. (The molecule ATP is 21 for instance.) You need life to create anything over 15; the idea of life is it contains information that can create structures more complex than what can be created randomly. The important thing about life is that it isn't spontaneous, but forms an unbroken chain through time. Explaining how it started may require new physics.

If the above seems unclear, it's because it is unclear to me. The book doesn't do a good job of explaining things. It looks like a mass-market science book, but I found it very confusing. For instance, it's unclear where the number 21 for ATP comes from, although there's an analogy to LEGO. The book doesn't define things and goes into many, many tangents. The author is very, very enthusiastic about the ideas but reading the book is like looking at ideas through a cloud of vagueness.

The writing is also extremely quirky. Everyone is on a first-name basis, from Albert (Einstein) to Johnny (von Neumann) and Erwin (Schrödinger). One chapter is written in the second person, and "you" turn out to be "Albert." The book pushes the idea that physics is great and can solve everything, covering physics "greatest hits" from relativity and quantum mechanics to gravitational waves and the Higgs boson. (The underlying theme is: "Physics is great. This book is physics. Therefore, this book is great.") The book has a lot of discussion of how it is a new paradigm, Kuhn's paradigm shifts, how it will move astrobiology beyond the pre-paradigmatic phase and unify fields of research and so forth. It's not a crackpot book, but there are an uncomfortable number of crackpot red flags.

I'm not rejecting the idea of assembly theory. To be honest, after reading the book, I don't understand it well enough to say which parts seem good and which parts seem flawed. There seem to be interesting ideas struggling to get out but I'm not getting them. (I don't like to be negative about books, but there are a few that I regret reading and feel that I should warn people.)

It always increases in an isolated system. That caveat is almost always missing in pop-sci level of discussions about entropy, but it is crucial.

> Eventually there will be enough entropy that any change may cause it to reduce or oscillate?

Assuming that the universe is actually an isolated system, entropy will reach a maximum (it cannot oscillate). It is interesting to speculate, and of course our theories are imperfect and we are certainly missing something. In particular, the relationship between time and entropy is not straightforward. Very roughly: is the entropy a function of time, which we could define otherwise, or is time a consequence of entropy changes?

In the first case, we can suppose that if the universe reaches an entropy maximum we’d be far enough outside the conditions under which our theories work that we’d just have entropy decrease with time (i.e., the rule that entropy increases with time is only valid close to our usual conditions).

But in the second case, it would mean that the universe reached the end of time. It could evolve in any conceivable way (in terms of the fundamental laws of Physics), and the arrow of time would always point to the same moment. "What comes after?" Would be a question just as meaningless as "what came before the Big Bang?"

In any case, there are a lot of assumptions and uncertainty. The story does not do the subject any justice.