Why Everything in the Universe Turns More Complex

Tried reading the paper [1]. I understand the authors are academics, which is why I'm surprised the paper reads like a layman's attempt at a contributing to a "theory of everything", or at best, an inquiry written by a 18th century European philosopher of science.

- "identification of conceptual equivalencies among disparate phenomena were foundational to developing previous laws of nature" - what exactly is a "conceptual equivalence"? You mean models? Unifying disparate observations into models is basic science. Not sure why it is highlighted here as some important insight.

- "The laws of classical physics emerged as efforts to provide comprehensive, predictive explanations of phenomena in the macroscopic world" - followed by a laymen's listing of physical laws, then goes on to claim "conspicuously absent is a law of increasing “complexity.”"

- then a jumble of examples including gravitation, stellar evolution, mineral evolution and biological evolution

- this just feels like a slight generalization of evolution: "Systems of many interacting agents display an increase in diversity, distribution, and/or patterned behavior when numerous configurations of the system are subject to selective pressure."

At this point, I gave up.

[1] https://www.pnas.org/doi/10.1073/pnas.2310223120

"Complexity" is a hugely problematic term when used in this way - remember that entropy and complexity are related, but they are not interchangeable. A complex system can have lower entropy than a simpler system, and conversely, a system can have high entropy but be relatively simple. By mingling these terms without specifying objective reference points, it all just comes out as word salad.

This paper just reads like an attempt at sounding smart while actually saying little.

Coincidentally, I'm reading Walker's book "Life as No One Knows It: The Physics of Life's Emergence" on the same topic. (Walker is one of the researchers in the article.) Summary: I don't like the book. The book was motivating me to write an article "Books I don't like", but I'll comment here instead :-)

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.)

Amateur speculation, but informed by professionals: I think this tendency toward complexity is situational, not fundamental. Specifically, it's a product of this stage of the universe having lots of available energy. More complex structures are favored when/because they can consume more energy and increase entropy more effectively. The complexity will probably start fading when the hydrogen-fusion party dies. The second law will continue on its way.

This reminds me of Teilhard de Chardin's take on complexification, as laid out in his seminal book Le Phénomène humain. See e.g., this article[0] for a simple overview of the hypothesis. For further reading, I recommend the excellent new translation by Sarah Appleton-Weber, The Human Phenomenon[1].

[0] <https://onlinelibrary.wiley.com/doi/pdf/10.1002/%28SICI%2910...>

[1] <https://www.liverpooluniversitypress.co.uk/doi/book/10.3828/...>

I'm fairly sure this is already in the usual canon of statistical mechanics.

"When one compares a hotplate with and without a Benard cell apparatus on top, there is an overall increase in entropy as energy passes through the system as required by the second law, because the increase in entropy in the environment (at the heat sink) is greater than the decreases in entropy that come about by maintaining gradients within the Benard cell system."

Sentences like this, i.e. "everything turns more complex", must be formulated much more precisely in order to become true.

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 law that entropy always increases holds, I think, the supreme position among the laws of Nature. If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations - then so much the worse for Maxwell's equations. If it is found to be contradicted by observation - well, these experimentalists do bungle things sometimes. But if your theory is found to be against the Second Law of Thermodynamics I can give you no hope; there is nothing for it to collapse in deepest humiliation.” ― Arthur Eddington, New Pathways in Science

I remember reading somewhere that maybe the purpose of life is to increase entropy in the universe. If that is true and we haven't found any sound evidence of life elsewhere, I don't know.

Isn't that like saying that "some things take time"? Complexity also takes time to develop through a myriad probabilities. We even define complexity along the concept of things taking time or equivalent space/memory. As the authors say, functional information of physical systems is very difficult to quantify. Until then, this is another formulation of the anthropic principle , but with complexity instead of humanity.

Pretty cool. I often wondered if the universe was evolving similar to natural selection via a reinforcement learning process. Wave function collapses to the value that maximizes some objective function.

How would you test for it though? I've seen enough residual data from RL processes to almost see semblences of patterns that could be extracted and re-applied at a macro scale.

The thing that is often missed in debates about entropy and Universe is that the classical notion on entropy is not compatible with General Relativity. Richard Tolman almost 100 years ago proposed an extension that was compatible.

One of the consequences of that extension was a possibility of a cyclic universe. On expansion one sees that classically defined entropy increases but then it will decrease on contraction.

These days that work is pretty much forgotten, but still it showed that with GR heat dearth of the universe was not the only option.