The Quark and the Jaguar: Adventures in the Simple and the Complex by Murray Gell-Mann
By JULIAN BROWN
The Quark and the Jaguar: Adventures in the Simple and the Complex by Murray Gell-Mann, W. H. Freeman in the US/Little, Brown in Britain, pp 392, £18.99
Consider this paradox. The rules of chess can be summed up in a page or two and most people can understand them fairly easily. Yet the game is very difficult to play well and is full of delightful subtleties and labyrinthine plots. A similar condition seems to apply to the Universe because the underlying laws appear to be fairly simple, yet manifestly it is extraordinarily rich in structure: quasars, stars, planets, rocks, trees and people are but a few of its many wonders.
It has often been a criticism of science that by attempting to reduce things to their simplest components, it loses sight of the whole. Few people are better placed than Murray Gell-Mann to respond to this criticism because he has done outstanding work on both sides of the divide. In 1963, he predicted the existence of the quark, the fundamental constituent of all matter, and developed the ‘eightfold way’, a method of grouping quarks that explained and predicted numerous subatomic particles. The quark is an essential component of what is now known as the standard model in particle physics.
In the 1980s, Gell-Mann diverted some of his energy away from the simplest objects in the Universe to the most complex. Rather than picking any one system such as the human brain and studying it in enormous detail, he has looked at complexity in search of possible unifying principles. As part of this effort, he helped to set up the world’s first centre for the study of complex systems, the Santa Fe Institute in New Mexico.
The Quark and the Jaguar is Gell-Mann’s overview of what we know about the opposite ends of the simplicity/complexity spectrum. The evocative title that symbolises Gell-Mann’s work so succinctly was inspired by a poem written by a Chinese-American poet Arthur Sze and read to him by his wife. It is all the more appropriate because Gell-Mann first suggested the name ‘quark’ for the fundamental particle, and as we discover in the opening chapter of the book he once came face to face with a jaguarundi while walking through the rainforest in Equador. That encounter sharpened his awareness of the beauty of nature at its most complex, reminding him of its fragility.
Gell-Mann’s wife Marcia, a poet and a professor of English, turns out to have been useful in other ways too because, as he reveals in the preface, he found the book very difficult to write because his father vigorously criticised anything he wrote as a child. Coming from someone who is famous for his prodigious abilities this comes as quite an admission. Marcia, it seems, goaded Murray into completing the task, and as a nonscientist acted as a sounding board for anything that might be too technical.
On this second point she has only partly succeeded – although it seems unfair to blame any lack of success on her. Gell-Mann admits that there are passages where Marcia would have preferred more clarity. Me too. The book is occasionally quite tough going. Nevertheless, it does offer an invaluable account of Gell-Mann’s world view because there is so much in it uniquely his own . Gell-Mann sets out to show how simplicity and complexity are connected by constructing ‘staircases between different disciplines’ from the underlying laws of physics up to the heady heights of phenomena like biological evolution and consciousness.
After some personal reminiscences on his childhood, he shows us some of the materials he uses to build those staircases. He introduces the notion of a complex adaptive system, which you might assume to be a fancy way of describing any biological entity from a bacterium to human being. However, Gell-Mann uses the term in a more general way to include other things like societies, investors on the stock market, the mammalian immune system and computers that evolve their own programs. It is the contention of this book that all of these things share common features, features that make complexity a subject in its own right. As he reveals these features, Gell-Mann discusses important ideas concerning how complexity can be defined and measured. Among them is the notion of ‘coarse graining’: the idea that whenever we measure the world we only ever do so down to certain level of detail much as the grains of a photograph impose a limit on the resolution of an image. In measuring a system’s complexity, it is essential to know what level of graininess you are dealing with.
Gell-Mann’s explanation and treatment of all this is very clear. It’s when he leads us down into the basement of science that things get trickier. He points to spooky stuff about quantum mechanics and the observer which he disparagingly describes as ‘flapdoodle’ because of what he calls the modern view of quantum mechanics. This, it emerges, is largely due to recent ideas developed by him and his colleague Jim Hartle. Intriguingly, one of them is the notion of ‘coarse graining’ again making a direct link between the worlds of simplicity and complexity. A second crucial idea is ‘decoherence’, to explain why everyday objects such as tables and chairs behave classically even though they are made of quantum objects like atoms.
I found much of Gell-Mann’s discussion of quantum mechanics is riveting because many of his ideas have yet to be covered in other popular books and you know you are getting the story from the most authoritative source. But I suspect that many people unfamiliar with the subject may find their understanding ‘decohering’ when they read passages that go under headings such as ‘Are there many inequivalent quasiclassical domains?’ ‘Who cares?’ you might ask. Well, Gell-Mann and Hartle obviously do because as we learn they are still trying to figure it out. Some readers may give up with the book at this point, a pity because there is still a lot of good stuff to come.
There are chapters on superstring theory, the arrow of time, biological evolution, creative thinking, the nature of myth and superstition, neural nets, machine learning, economics, biological diversity and, finally, sustainability. That is the beauty of complexity: it covers just about anything that is, well, complex. The amazing thing is the way Gell-Mann assembles everything into one coherent whole, showing how the ideas of simplicity and complexity intertwine and how they are applicable to a vast range of phenomena.
Of course, the jury is still out on whether the study of complexity is here to stay or whether it’s just another of those passing fashions – remember catastrophe theory in the 1970s, and, to a lesser extent, chaos in the 1980s? Work on algorithmic information theory and computer-generated artificial life is undoubtedly producing tangible results, but it is in the realm of the social sciences where things look far more speculative. Gell-Mann regards the economics programme as one of the most exciting activities at the Santa Fe Institute, but on the strength of the results he cites briefly in this book, it is not clear that economics is about to become ‘less dismal’ as a science.
But it is still early days for complexity; Gell-Mann says the next few years will be critical for the institute’s work. But if you want to catch up on the story so far, and hear Gell-Mann’s numerous insights into the physical, biological and social world, then read this book.