Customer Reviews

How Nature Works: The Science of Self-organized Criticality

5 star:		(5)
4 star:		(7)
3 star:		(0)
2 star:		(4)
1 star:		(4)

 

 

I couldn't let the previous reviewer's comments stand without comment. I can't believe the reviewer read the same book that I did. Bak's treatment is detailed, clear, and balanced. When he is enthusiastic he let's you know exactly why, leaving you free to make up your own mind. The fact that most of the studies he describes were published in Physical Review Letters might tell you something about their quality. The book provides wonderful examples of the role of models in science, much better than any I've come across in rather extensive search for materials for a course on the Nature of Science I help teach. I'm reading the book for the third time (not because it is difficult to read, but simply because it repays rereading) and I admire it more with each reading. If you want to understand models that display Self Organized Criticality, this book is without question the place to go.

Per Bak's book How Nature Works is about the theory of self organizing criticality and its applicability to a variety of questions and problems in several sciences. It is an interesting and quick read for the most part. I have read other books on self organized criticality that were far less understandable and more limited in their scope of applicability.

Although there were portions of Bak's work that were a little belabored-I found my interest in sand piles began to sag after the initial discussion, for instance-much of the rest of the book was enlightening. The discussion in Chapter 1 of the contrast between the clarity and simplicity of the laws of physics and the complexity and unpredictability of nature was particularly interesting as was the discussion of the difference between chaos and complexity. His explanation in Chapter 2 of the theory of self organized criticality and the history of its development is far clearer than I found Stuart Kauffman's to be. It might make a better starting place for anyone wishing to understand the theory a little better before going on to Kauffman's and other books on the subject.

Essentially the theme of the book involves the self organization of much of the universe, from stars and volcanoes to traffic jams and economics, into critical states sustained as stable systems until they evolve through cascade events or what Bak calls avalanches (after his sand pile paradigm) or catastrophes. Bak explains that the system maintains itself along a critical line, above which chaos rules and nothing can be predicted and below which nothing happens so there is nothing to predict!

Chapter 5 which deals with earthquakes and volcanic eruptions interested me in particular because of my own study of geology. Here Bak suggests that geophysicists' attempts at prediction of events is a lost cause. He believes it to be based upon the mistaken human habit of looking at random events for patterns and periodicity where none exists. While the history of a given event can be studied in some detail after the fact, the information derived is useless in predicting the future. In Bak's opinion, the variables involved are so legion and are interrelated in so convoluted a way as to be impossible to monitor before the fact.

In chapters 7, 8, and 9 the author attempts to model Darwin's gradual evolution, Gould's punctuated equilibrium, and the Santa Fe Institute's fitness landscape to see which fits the facts better. In general Darwin's theories are vindicated---no real surprise there---while punctuated equilibrium is also found to have it's place in a complete theory of evolution. Chapter 11 contained a section on the unavoidability of catastrophes and fluctuations---and by their extension, one supposes, biological evolution-which casts light on the boom and bust character of economics among other things. This chapter extends the use of the theory of SOC to human activities as well as to human evolution.

The author's style is very chatty, which makes it readable and personable. By filling in the human details of the discoverers, he makes the book more personal. In all, though I found myself occasionally losing the thread of the author's theme, I nevertheless found the content of each chapter well worth.

This is both a wonderful book and an awful one with two interleaved narratives. I've read the book cover to cover and some of the key chapters several times over. I've also replicated some of the key simulation results on a personal computer. Much to the credit of Per Bak's clear explanations designed to simplify he eminently succeeds at his task of making his point: complexity in nature can be simple to understand. Bak points out the existence of power laws in self-organized critical systems occurring in nature and he gives the reader the ability to model them using simple numerical methods. We could call them "back of the envelope calculations" if the were analytic. All of this he manages to do without the need for the reader ever to go to the published literature. In the process of doing that, he does not completely strip off the plausibility of the models. In some sense it is quite a tour de force.

So what could be awful about such a wonderful book? It would be a great world if those who make significant advances in science were magnanimous. While one narrative in Per Bak's book is all about self-organized criticality, the "other" narrative comes out all but too self-serving. Per Bak relishes in his moment in the limelight of science as he uses every bit of it as a platform to offer judgmental and patronizing opinions about every other field of science (including his own physics) and many colleagues he's worked with or benefited from the insight of... When convenient, reductionism is good but when not convenient, reductionism is vile. Big Science is mindless, except perhaps for this or perhaps for that... A lot of this "other narrative" really sounds like small talk around the departmental coffee pot with a few smirks and some wry smiles. Perhaps the editor might have suggested it all stayed there. If all this was really meant to be tongue in cheek or said with a kind smile, consider rewriting the prose.

The "real reality" about science is that it benefits from advances on all fronts, both the microscopic and the macroscopic. Both the linear and the non-linear. It is men and women who do science, not machines, and unfortunately they sometimes bring in hubris with an inch gained here or there. Go ahead and buy the book (it's reasonably priced...), enjoy the first narrative and try to disregard the second, if you can.

I used this book (along with Stu Kauffman's "At Home in the Universe, Feynman's "The Character of Physical Law", and Cohen & Stewart's "Collapse of Chaos") for a freshman seminar at Duke University on "Emergence of Complexity". My students really enjoyed Bak's book. It gave them a whole new perspective on the nature of physical and biological systems and on the nature of scientific models. Most importantly, their short essays on various parts of the book showed that Bak's enthusiasm for his subject was contagious. Students appreciated Bak's creative use of simple models to introduce new ways of thinking about a wide range of phenomena.

In spite of its many faults: failure to acknowledge Prigogine's conclusions that foreshadowed most of Bak's; petty sniping at others, incredibly hit and miss editing, and some outright silly passages (such as the idea that people living somewhere where there haven't been earthquakes for a long time would want to buy earthquake insurance), Bak has something important to say, and at times says it well and eloquently.The fact that he has found a substantial number of natural systems that create a spoor of commmon properties, and has nailed some of them is important. But: he says he insisted on the title of his book, not the editors (permit me to doubt this)and then says not one word about how he came to the conclusion that power curves, fractals, 1/f distributions and Zipf's law apply to ALL of nature. Has he any evidence of natural processes that don't? Is anyone working this side of the problem? He has a refreshing view of what good science consists of, but does not display a scientist's attitude of disinterested pursuit of truth. This may be editorial inspiration to avoid qualifications in order to make stronger statements. I hope so, because I genuinely like the way he thinks, and find his ideas stimulating. But his claim to be the "discoverer" of self-organized criticality is close to fatuous.

Per Bak has made a glitzy try at explaining a number of natural phenomena. The idea of "self-organized criticality" is one that many disciplines grom geology to taxonomy to economics have had as a "dance partner."

Unfortunately, the idea of spontaneous order requires rigorous argument, not just clever analogy. For an elegant statement of the relations among the processes and components of the Universe that interact to give us stability and instability, basic arguments and a history of ideas can be found in Prigogine and Stengers' "Order Out of Chaos: Man's New Dialog with Nature." In collaboration with Stengers, Prigogine has updated his arguments for the role of the structures and behaviors in Nature in "The End of Certainty: Time, Chaos and the New Laws of Nature." Incidentally, the Nobel Laureate work of Ilya Prigogine seems not to have been discussed in Bak's cute little book. Even though this book is clearly written, there are enough omissions and errors to make a reader nervous.

For two instances of many problems. 1-Many examples are drawn from paleontological and evolutionary phenomena. Data on life spans of fossil genera (a Sepkowski compilation of data) are the source for one of histograms and are incorrectly transferred to Bak's book as a "kill curve." Kill curves are an important part of evolutionary/extinction theory. Bak might also have cited Van Valen's mechanism for disappearance by predation: the Red Queen's Hypothesis (roughly put, predators snarf up the most convenient meal, not always the slowest member of a species). This is an interesting variation on natural selection and one which Bak's cleverness could discuss to good effect. 2-Linear log-log plots appear without error bars and might have been done by the old Mark One Eyeball Method. How is a reader to know if the data reflected in the points were sloppy or tight fits? This is a crucial point in pattern matching. A shaky pattern makes a less convincing argument than a rel! iable one. Why aren't major intellectual contributions to the idea of self organization and critical conditions from Van Valen (1973), G. U. Yule (1987), D. Raup (1991) and Prigogine (1984, 1996) given some discussion?

I mention the above examples because argument by analogy is centered on Pattern Matching. Pattern can be defined for mathematical purposes as "a template, motif, design which may be repeated" (see Grünbaum and Shephard, "Tilings and Patterns"). But Bak does not say WHY pattern in mathematics (created by mathematical rules) should match pattern in Nature (created by rules which we are still working out). A quick answer would be that the pattern/analogy is only as good as the elements of the items being compared are comparable. Clearly, mechanisms of creation of the compared patterns are different. Use of analogy is a creative, useful way to probe the unknown by the known, but Bak does not lay even this foundation for the arguments in the book.

Because mathematical pattern (as survival curves, radioactive decay and the like appears in nature does not mean that the pattern match alone is "proof" for general a natural process as explanation for diverse observations. Bak's "avalanche behavior in sandpiles" is only as good as a master pattern if the transfer of data and mathematical information from other sources is impeccable. For an example of careful argument using understandable mathematics to understand processes in nature I recommend David Raup's witty "Extinction: Bad Luck or Bad Genes?."

In closing, I cannot recommend this book in spite of its occasional cleverness and clear writing. In the spirit of the Red Queen's Hypothesis, it is not quite quick enough to avoid the predator/critic.

Per Bak claimed to have invented a fundamentally new way of looking at nature by ascribing an almost mystical significance to ``power-law'' distributions (for the non-technical reader, that simply means one quantity is proportional to another quantity raised to some power; the power, typically a number like 1.8, is a constant). There are two things wrong with this claim:

1. There is no deep significance to a power law distribution. All it means is that there is no natural scale of the phenomenon. (No power law runs from zero to infinity, so at best it means that there is no natural scale in the range in which the distribution is a power law.)

2. There is nothing new about this conclusion. It was understood in the 1940's by Kolmogorov in his theory of turbulence and Fermi in his theory of cosmic ray acceleration. The only thing Bak added was the application of these old ideas to the artificial and uninteresting problem of sandpiles.

There is nothing wrong with taking old ideas and applying them to new problems. However, Bak never admitted where the ideas came from. He never cited this earlier work. For example, models identical to his ``Self Organized Criticality'' were published by scientists working on earthquakes (Journal of Geophysical Research 90, 1894 [1985] and 91, 10412 [1986], building on earlier ideas by Knopoff). Although Bak was aware of this work, published before he ever began working on ``SOC'', he didn't acknowledge it. To a scientist this is an unpardonable sin, equivalent to a banker cooking the books.

There is a striking resemblence between Bak's How Nature Works and Wolfram's A New Kind of Science. Each author claimed to have made profound and original insights which explain not just one phenomenon, but almost every aspect of the world around us. In each case these supposed insights are essentially mathematical, based on models which ignore the actual physical, chemical or biological processes involved. And in each case closer examination shows that the work is almost trivial, and irrelevant to real scientific problems. You get out what you put in, and when you don't put any science in you, don't get any science out.

Each of these authors has also claimed credit to which he is not entitled by failing to acknowledge the prior work of others. They suffer from a would-be-genius syndrome, in which someone is so infatuated with his own supposed brilliance that he both exaggerates the slight significance of his work and fails to give credit to those who actually did it earlier....

One of the most original concepts of modern times is pulled together in this book. The named a whole new science because of Per Bak and his many friends: complexity theory. I think he hasn't grasped the whole of it yet, but this book gives an overview of where he has gone following fractal and chaos down the road to practal physics. From entropy and Zipf's law to piles of sand that fall when overloaded, a picture of a differential physical geometry that influence the great and the small is set forth in terms that are understandable. Self-organization of a critical nature is the clock work of a Godless universe with a purpose.

This book is a great attempt at finding some universality based on systems in a "critical" state, with departures from such state taking place in a manner that follows power laws. The sandpile is a great baby model for that.
Some people are critical of Bak's approach, some even suggesting that we may not get power laws in these "sandpile" effects, but something less scalable in the tails. The point is :so what? The man has vision.
I looked at the reviews of this book. Clearly a few narrow-minded scientists do not seem to like it (many did not like Per Bak's ego). But the book is remarkably intuitive and the presentation is so clear that he takes you by the hand. It is even entertaining. If you are looking to find flaws in his argument his pedagogy allows it (it is immediately obvious to us who dabble with simulations of these processes that you need an infinite sandpile to get a pure power law).
Another problem. I have been ordering the book on Amazon for ages. Copernicus books does not respond to emails. I got my copy at the NYU library. Bak passed away 2 years ago and nobody seems to be pushing for his interest and that of us his readers (for used books to sell for 99 implies some demand). This convinces me NEVER to publish with Springer.

Per Bak's ideas (and ideas of others that are occasionally presented without quoting the original sources) are remarkably interesting, but the book itself seems to be a product of an uncontrolled avalanche in author's brain. Too low rigor and signal-to-noise to be interesting scientifically, too poorly written to be read as fiction - sorry, two stars. A 10-page summary could have done much better.