I guess it was inevitable that in my wider reading on subjects such as astronomy and physics I would eventually bump into quantum mechanics. Where I have encountered it so far, I have admitted it went straight over my head. It might thus seem foolhardy for a biologist to try and tackle a book like this. Then again, the hallmark of good communicators is that they make complex topics understandable. And theoretical physicist Sean Carroll’s previous books have been lauded, some even winning prizes. Are you ready to get down and dirty with quantum mechanics?

Something Deeply Hidden: Quantum Worlds and the Emergence of Spacetime, written by Sean Carroll, published in Europe by Oneworld Publications in September 2019 (hardback, 368 pages)

Carroll’s opening salvo, and one of the main reasons to write this book, is that physicists do not understand quantum mechanics. That’s right. They know how to use it to design new technology or predict the outcomes of experiments, but they do not truly understand it. And for a theory that was pretty much formulated by 1927 that is more than a bit embarrassing. What is worse, Carroll writes, is that many physicists scoff at the idea of spending time and effort on understanding its foundations.

Carroll thinks we have made good progress with this, though, and throughout this book, he champions the Everett or Many-Worlds formulation of quantum mechanics that was developed in 1957 by Hugh Everett.

This is where we reach a fork in the road. I could go ahead and try and summarize the ideas put forward in this book, leaving you with the impression that I understood everything he is talking about.

“Carroll’s opening salvo, and one of the main reasons to write this book, is that physicists do not understand quantum mechanics. That’s right.”

I could write about the contrast between classical mechanics where particles have a location and a velocity, and quantum mechanics where these are replaced by a cloud of probability. Here, particles exist in a superposition of all possible locations and velocities that only take on a single value when we observe them, i.e. quantum wave functions appear particle-like when observed. (Actually, that bit I did understand.) I could write of Werner Heisenberg’s uncertainty principle and Niels Bohr’s concept of complementarity: particles have a wave function and you can describe either a particle’s position or its momentum (its velocity), but not both simultaneously. This was empirically shown by the famous double-slit experiment.

I could write about quantum entanglement and whether or not, depending on which theorem you follow, particles interacting at a distance means that information is travelling faster than light. Or about Everett’s assertion that the universe can be described by a single wave function, evolving according to the Schrödinger equation. Or the fact that parts of the universe interacting (two particles for example) lead to them becoming entangled. That this is called decoherence and, according to Everett, means the wave function branches into multiple worlds, representing all the different ways in which such interactions could have played out. And that the space of all possible wave functions is called the Hilbert Space which may or may not have an infinite number of dimensions (I apologise in advance to any physicists reading this if I have butchered above brief summaries).

I could do all of this. But I won’t. It will probably bring a smile to Carroll’s face if I say that I would like to think that there is a branch of the wave function where I did write that review.

“[…] nature is quantum by definition – classical physics is what we observe because our brain cannot observe wave functions, the same way four-dimensional space flummoxes our brain.”

The truth is that most of the concepts explained here still seem esoteric, abstract, and counterintuitive to me. Partially that is the nature of the beast. As Carroll writes, nature is quantum by definition – classical physics is what we observe because our brain cannot observe wave functions, the same way four-dimensional space flummoxes our brain. But we can still calculate and theorise with it. And partially it reflects that even physicists are still trying to wrap their heads around all of the above.

But here are three reasons why this did not matter to me and why, despite the mental gymnastics involved, I still enjoyed this challenging book.

First, even though this book is not a history book, Carroll gives a short overview of how these ideas developed and, importantly, corrects common stories told about, for instance, Albert Einstein. Such as that by the time of the 1927 Solvay conference, where leading physicists met to discuss quantum theory, Einstein had grown old and conservative in his ideas, lost the debates with Bohr, and could not get to grips with Heisenberg’s uncertainty principle. That is not how Carroll reads this history.

“The universe does not copy itself at every interaction like a foam bath bubbling over. “Branches” and “worlds” are just convenient shorthands for us humans to talk about the evolving wave function of the universe.”

Second, in spite of the mind-bending concepts, Carroll employs excellent metaphors and examples, uses handy diagrams, and even includes a staged dialogue between a theoretical physicist daughter and her sceptical particle physicist father. And he is balanced enough to consider some alternatives to Everett’s Many-Worlds formulation. All of this makes matters if not understandable at least graspable. I found myself reading along and thinking “I sort of see where you are going with this”. Carroll’s casual writing style and occasional humour help much in this regard. And though he throws in the occasional equation as an illustration, he does not bog the reader down with impenetrable calculations.

Third and final, Carroll devotes space to providing a reality check on what quantum mechanics actually means. Over the decades, a lot of ideas have leaked into mainstream thinking where they have started leading a life of their own and are being taken out of context. Does the Many-Worlds formulation mean that there are a near-infinite number of copies of you and me out there, each corresponding to all the possible choices we could have made at every turn in our lives? Not quite. The universe does not copy itself at every interaction like a foam bath bubbling over. “Branches” and “worlds” are just convenient shorthands for us humans to talk about the evolving wave function of the universe.

Something Deeply Hidden is a book that pleasantly stretches the mind. It even makes previous books I have read, such as The Case Against Reality, a bit more understandable. Although, as an aside, my impression is that Hoffmann’s assertion of conscious agents being at the base of everything (Carroll calls it idealism on pages 223-224) is totally at loggerheads with Carroll’s understanding of quantum mechanics. Even though the finer points might still elude me (perhaps I should take it down a notch and pick up Quantum: A Guide For The Perplexed), Carroll convinces that the study of quantum foundations is a worthwhile and interesting academic pursuit. And given his pleasant writing style, I am certainly tempted by his other book, The Big Picture.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

Something Deeply Hidden paperback, hardback, ebook or audiobook

Other recommended books mentioned in this review:

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“Quarks to Culture: How We Came to Be“, written by Tyler Volk, published by Columbia University Press in May 2017 (hardback, 250 pages)

Biologists are fascinated with these questions, and plenty of books have marvelled at the vast chain of being, trying to discern patterns. This ranges from popular treatments such as Life Ascending: The Ten Great Inventions of Evolution or Restless Creatures: The Story of Life in Ten Movements to more scholarly ones, such as The Major Transitions in Evolution, The Major Transitions in Evolution Revisited, or Biology’s First Law: The Tendency for Diversity & Complexity to Increase in Evolutionary Systems. Some say it is energy, others that it is information. “No, physics is life’s silent commander”, says a third (see respectively The Vital Question: Why is Life the Way it is?, and my reviews of The Demon in the Machine: How Hidden Webs of Information Are Finally Solving the Mystery of Life and The Equations of Life: The Hidden Rules Shaping Evolution). But Volk wants to look beyond this, at, as he puts it, “the whole shebang”, all the way from elementary particles to political states, from quarks to culture, to search for a universal pattern. And Volk sees one.

See, Volk says, our world, our whole universe, is like a giant Matryoshka doll, one set of things nested inside the next. (Actually, he does not refer to these Russian dolls anywhere, I do – but it’s a fitting metaphor.) Simple things combine to form larger complex wholes that have new properties. This is the phenomenon of emergence (see e.g. Emergence: The Connected Lives of Ants, Brains, Cities And Software) and is the domain of systems theory and complexity studies. And that is the universal pattern that Volk sees.

But he is not content with calling it emergence, instead calling it “combogenesis”: things combine and integrate with other things into new, larger things at a new level. At this new level, these larger things can form new kinds of relationships with others at the same level, giving rise to yet another new level. And so on, in an upwards cascade of nestedness, something he dubs the “grand sequence”. Now, throwing around your own terms and calling things “grand sequences” all sounds a bit, well, grandiose and reeks of hubris. Luckily, that is not at all the spirit of this book, and Volk keeps things uncomplicated and pragmatic, talking of “things” and “levels”.

“[…] our world, our whole universe, is like a giant Matryoshka doll, one set of things nested inside the next.”

In twelve chapters, Volk takes that logic to reason his way up twelve levels. So, fundamental quanta (quarks, leptons, bosons, etc.) combine to form nucleons (protons and neutrons), which combine to form atomic nuclei, and on it goes to atoms, molecules, prokaryotic cells, eukaryotic cells (here Volk invokes endosymbiosis, see One Plus One Equals One: Symbiosis and the Evolution of Complex Life), multicellular organisms, animal social groups, human tribes, agricultural settlements, and finally geopolitical states.

A final series of chapters looks at the whole sweep, highlighting several interesting observations. First off, as he acknowledges, it is unapologetically anthropocentric. I am sure that following the same reasoning you could draw up other “grand sequences” with different endpoints (molecules, stars & planets, galaxies, superclusters?). But Volk wants to focus on how we humans got to where we are. Second, are there more levels further down or higher up? The latter is something he speculates on in the epilogue. The former, as he points out, is what physicists are labouring over worldwide, with string theory being one, albeit controversial candidate (see e.g. The Elegant Universe: Superstrings, Hidden Dimensions and the Quest for the Ultimate Theory versus Not Even Wrong: The Failure of String Theory and the Continuing Challenge to Unify the Laws of Physics).

It also spans several fields, from physics to biological evolution to cultural evolution. Volk introduces the idea of dynamical realms, with certain steps (such as from molecules to cells) heralding a major transition, literally opening up a new world of possibilities. Cells, then, are the base level of the realm of biological evolution. Is there an explanation for these major transitions? Here he names one last new concept: the alphakit. An alphakit contains a small number of elements that can be combined into an enormous number of possible ways. The first example to come to mind is how a limited number of letters (or really phonemes: distinct units of sound) can be combined into almost unlimited arrays of words, sentences, books, etc. You can do a lot with those basic building blocks.

“Volk introduces the idea of dynamical realms, with certain steps (such as from molecules to cells) heralding a major transition, literally opening up a new world of possibilities. “

The argument is not so neat that an alphakit automatically signals a major transition. For example, there are only 92 stable kinds of atoms, but the number of possible molecules is huge. However, molecules are not, by themselves, alive. At this point we’re still in the realm of physics. Indeed, how inanimate matter becomes alive remains a vexing question, see e.g. What is Life? How Chemistry Becomes Biology. But the reverse seems to hold: major transitions seem to require these alphakits. On the border of the realms of physics and biology few atoms give rise to many molecules. Some of these molecules (the combo of four DNA bases and a small number of amino acids) give rise to larger numbers of other molecules (genes and proteins). Same at the transition from biological evolution to cultural evolution where a small number of phonemes gives rise to language, allowing for the next series of iterations. Also invoked here is the concept of a field of possibilities, which are all the theoretically possible combinations of elements. Wagner introduced this in his fascinating Arrival of the Fittest: Solving Evolution’s Greatest Puzzle to argue how evolution can probe these multidimensional spaces of possible protein sequences to rapidly come up with innovative solutions to life’s problems.

Earlier on, Volk makes a distinction between what is and is not a case of combogenesis. So, cells combining to form multicellular animals is combogenesis, but whales evolving from worms is not. The latter is a matter of “more of the same”, not “more of a different kind”. By that logic, the alphakits Volk introduces sometimes involve combogenesis (from atoms to molecules), but sometimes they don’t (from amino acids to proteins, these are both types of molecules).

No doubt readers both inside and outside of complexity studies will find plenty to question and criticise here. I mentioned the possibility of other “grand sequences”. Harold Morowitz did a similar exercise in his book The Emergence of Everything: How the World Became Complex, but required 28 steps. And I wonder: is combogenesis really different enough from emergence to warrant its own term?

My impression is that Volk would be delighted to see his ideas discussed. Quarks to Culture is engagingly written, often chatty (a style I personally enjoy). To wade into subatomic particle physics as a biologist is courageous of Volk, but he seems to have read up on the topic and spoken to plenty of colleagues who explained it to him. Volk excels at translating that for his readers, kindling a new interest in me. Despite the questions and eyebrows this book might raise for some, if you read it in the spirit it was intended – a thought experiment rather than a fully-fledged theory – I expect you will find it a rewarding and thought-provoking intellectual exercise.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

Quarks to Culture hardback or ebook

Other recommended books mentioned in this review:

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“The Equations of Life: The Hidden Rules Shaping Evolution“, written by Charles Cockell, published in Europe by Atlantic Books in June 2018 (hardback, 339 pages)

That physics imposes hard limits on life is not necessarily a novel idea. D’Arcy Wentworth Thompson’s 1917 book On Growth and Form already put forth the idea that morphology and growth are dictated by physical laws and can be described mathematically. And Vogel’s 1989 book Life’s Devices: The Physical World of Animals and Plants is a great, if slightly dated, introduction to biomechanics. Cockell starts off at the level of animal groups such as insect communities and flocks of birds to show how simple mathematical rules can lead to the emergence of complex behaviours. And, like above books, he discusses how the form of organisms is dictated by physics, touching on some of the power laws and network-like properties that George West discussed at length in Scale: The Universal Laws of Life and Death in Organisms, Cities and Companies. There are plenty of equations, some simple, some complex, although they are really only there to illustrate his point. I was expecting the book to stay at this level and discuss how various laws of physics limit the possible outcomes of evolution. What I wasn’t quite prepared for was the giddy tumble down the hierarchies of life in the rest of the book, but was I ever so pleasantly surprised.

Starting with cells and how physics explains why they developed, the book then considers DNA and proteins, offering an explanation of why we have four different base pairs in DNA instead of six or more. On a smaller scale, life is about acquiring energy which is achieved by transferring electrons across cell membranes (in The Vital Question: Why is Life the Way it is?, Nick Lane considered this to be life’s ultimate linchpin). Further down still, water (and not another solvent) is used as the medium in which to carry out biochemical reactions, and life uses a very limited set of atoms as its predominant building blocks. At every turn, Cockell shows how physics explains why life has preferred the solutions it has preferred, and how proposed alternative solutions (such as life forms based on silicon instead of carbon) would not work as well.

“physics is life’s silent commander”

Cockell is a professor of astrobiology, a discipline that studies early biology and origins of life in the universe, as well as the possibility of extraterrestrial life and what it might look like. Amongst the many books he has written on the subject is the undergraduate textbook Astrobiology: Understanding Life in the Universe. The abovementioned descent down the hierarchies of life is at the same time an excuse for him to speculate what these findings mean for life elsewhere in the universe. Cockell clearly enjoys his forays into this topic, throwing in a short overview of exoplanets as a bonus (for a fuller picture of that, you can take your pick from at least four current or forthcoming pop-science works, which I link to below). Based on the fact that many principles of physics apply throughout the universe, he makes a strong case for extraterrestrial life likely resembling life forms as we know them on earth, speculative zoology and science fiction notwithstanding.

To long-time readers of this blog, the question of the predictability of evolution might sound familiar. Indeed, it was also explored in Losos’s book Improbable Destinies: How Predictable is Evolution?, the first book reviewed here. Cockell acknowledges this book several times in his chapter notes, and throughout the book he considers whether what we see in living organisms is a consequence of convergent evolution (life independently evolving the same solution repeatedly) or contingency (the result of chance events that could work out completely different if we could repeat the evolution of life). He recaps Losos’s discussion of the main players in this debate, namely Stephen Jay Gould, who was a proponent of contingency (see amongst others his book Wonderful Life: The Burgess Shale and the Nature of History), and Simon Conway Morris, who was a proponent of convergent evolution (see amongst others his books The Crucible of Creation: The Burgess Shale and the Rise of the Animals and The Runes of Evolution: How the Universe Became Self-Aware).

“[Cockell] makes a strong case for extraterrestrial life likely resembling life forms as we know them on earth, speculative zoology and science fiction notwithstanding”

In the end, your answer to this question depends on your perspective. Cockell is willing to concede that, yes, if you focus on the details, the variety of life seems bewildering and unpredictable, and there seems to be a lot of contingency. But to him this is just icing on the cake. When you zoom out and consider life on a more fundamental level, the outcomes of evolution are highly predictable, and convergent evolution is the rule. From his vantage point, that of physics circumscribing the limits of life, life has almost no other choices. Maybe, just maybe, if we discover life elsewhere in the universe, we might find some very exotic solutions to life’s basic needs, but Cockell convincingly argues that these will be the very unlikely exceptions occurring under the confluence of very exceptional circumstances.

Written with enthusiasm, in turns lyrical and infused with a dash of humour, The Equations of Life is a pleasure to read. In a few places, Cockell assumes perhaps just a little too much background knowledge of physics on the part of the reader, such as when he casually talks about the various orbitals and suborbitals that electrons can occupy in an atom. I also think that for a popular science work of this calibre, the book could have used illustrations of basic concepts in places. Overall, however, I think Cockell does a marvellous job of presenting complicated and abstract concepts in an understandable way. Both convergent evolution and the role of physics in biology have been written about before, but with his background in astrobiology, Cockell presents a unique take on the subject that comes highly recommended.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

The Equations of Life paperback, hardback, ebook or audio CD

Other recommended books mentioned in this review:

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Some recent popular science books on exoplanets:

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