Monday, October 17, 2005

Laughlin vs. reductionism

A review of "A different [not too elegant] Universe".

Robert Laughlin is a great physicist who has found some truly important insights about condensed matter physics in general and the fractional quantum Hall effect in particular, and he deserves his 1998 physics Nobel prize.

But his attempts to say something profound about fundamental physics and particle physics seem far less serious. Be sure that my opinion is shared not only by a huge majority of "fundamental physicists" but even by many colleagues of Laughlin in condensed matter physics. The main problem with his reasoning is that he has obviously no solutions for the problems he tries to address.

All of us agree that some important features of physical phenomena do not depend on the details of underlying physics; many of these phenomena are emergent in character; it is not too important or useful to know quarks or strings in order to study most of the crucial concepts in biology, climate, physics of water, or quantum computing. If Laughlin thinks that other physicists do not realize this fact, then he is fighting a strawman. Most physicists realize these things - and many fundamental physicists actually use very similar mathematical techniques as Laughlin does in his "emergent" approach.

But at the same moment, there are contexts - and particle physics and/or fundamental physics is a textbook example - where we simply do need to ask different questions. We need to know what natural laws underlie the phenomena we observe at longer distances. We need to find more fundamental, more elementary, and usually smaller constituents of the matter and the interactions that control their dynamics. We need to get closer to the "theory of everything", regardless of the question whether the destination is a finite or infinite distance away. (And yes, the path should not be infinitely long because there is no physics "below" the Planck length.)

We need to study these questions whenever we want to determine physics more accurately; we also need to study these questions because we want to acquire a deeper knowledge that is necessary for future constructions of emergent theories; we need to investigate the underlying physics in order to illuminate some features and parameters of the effective theories that the effective theories themselves simply don't explain and can't explain. People have been looking for more fundamental theories of the real world for quite some time, they have made a tremendous progress in this reductionist quest, and the reductionist approach is responsible for many of the achievements of the modern era. If there were no reductionists in the 19th and 20th centuries, electrons would not have been discovered and Laughlin could probably never construct the wavefunction for which he was awarded by the Swedish Academy of Sciences.

And as Kasper Olsen points out in the comments, without the search for more elementary and unified laws of physics we would have to deal with separate "laws of Hydrogen", "laws of Helium", "laws of tigers", "laws of labs that measure the fractional Hall effect", and billions of other laws. I personally prefer many insights that follow from - or at least agree with - the Standard Model or string theory.

Laughlin seems to misunderstand these points. He thinks that his dislike for particle physics is a valuable idea by itself. It's not. He has nothing to say about these issues, and therefore silence would be better for him and for everyone else. The same conclusion holds for Laughlin's opinions about the black holes and other issues in the realm of fundamental physics.

Laughlin seems to believe that the condensed matter physics way of thinking is very rare among particle physicists, string theorists, and general relativists, and therefore it is very important for him to present conjectures that the black holes are made of plastic or something very similar. But such conjectures are not too useful because fundamental physics simply does not work in this way. If physics of polymers were important for the research of black holes, it is very likely that the black hole physicists would be forced to figure out how to apply these rules even without the help of Prof. Laughlin.

The book uses many metaphors from the everyday life. The author usually offers ten sentences even though his simple and shallow idea is completely clear already from the sentence number one. Several chapters at the end of the book are redundant as wholes.

You don't need to read this book. The main ideas can be summarized as follows: Prof. Laughlin believes that we should always be satisfied with a superficial description of physical phenomena and we should never try to look "inside" in order to identify more elementary components. Prof. Laughlin is wrong, he has nothing to say about the important questions that Laughlin believes are unimportant, he actually says nothing about most of the important questions in the reductionist vs. emergent debate, and you better save your money and time.


  1. Lubos:

    Your link leads me to other reviews you have written on Amazon. What interests me is the one on "Population Bomb"

    I have to disagree with you completely on that review. Population Bomb is real, but how and when it happens and in what way is any one's guess. But the fact remains that the earth simply can not support 6.5 billion people in any sustainable way, not to meantion that the population is still increasing exponentially.

    Your intelligence should allow you to do this simple arithmatics exercise. Starting with a group of our ancestors, not one million years ago, but a mere ten thousand years ago, and assume the population grows at a very modest ratio of 1% increase per year steadily. What could the world's population be today?

    The answer is if the population has been growing at 1% unchecked for 10 thousand years, then we would have much more people than the number of atoms in the whole earth today!!!

    Clearly that's an impossible scenary. Regardless how many more children each woman may have, the nature has a way of keeping the population in check and never reach any where close to the count of atoms on the earth. Famines, diseases, disasters, wars, you name it.

    Malthus was right. If you look through the whole history of humanity, not just these recent few decades after WW II, then you see that disasters were the norm and peace and prosperity were rare.

    Any way you put it, there is not a physics law that would allow the population to grow beyond what the limited natural resources can support on this small planet. It simply will not happen by definition.

    You may think that the progress of technology could one day allow us to go beyond the earth and migrate to other parts of the universe, and hence no longer restricted by the limit of the earth. But if this is possible, then it may have happened on countless extra-terristrial civilizations a long time ago. And they would have been so advanced and spread and colonized the whole of the universe already by now, including our own earth. The fact that we exist as free people instead of being slaves of aliens means that's highly unlikely.

    The so called green revolution will soon be proven as the green disaster. The material basis of the green revolution: fertilizers and pesticides, are based on a precious and none-renewable resource: petroleum, which has now start to run short, because we have used about half of what we can have. Once the massive production of fertilizers and pesticides are no longer possible, we will not be able to produce enough food to feed all 6.5 billion people, and a massive famine will be assured.

    I wish you can read and comment on this book, too.


  2. And sure enough the main stream media is starting to talk about Peak Oil louder and louder, see this on USA Today


  3. Having read Laughlin's book, I would disagree with your review. Far from saying that reductionism is bad, Laughlin instead implies that we have chased reductionism too far without allowing our understanding of emergent behavior to catch up. He mentions, for instance, that even though we understand very precisely the principles of quantum mechanics governing the atoms in complicated proteins, we still cannot predict which of them will crystallize easily and which will not. No doubt, with each layer of understanding that we have uncovered, amazing new insights into the universe have resulted; Laughlin in fact argues that the entire point of reductionism is to be able to explain and predict physical phenomena in progressively clearer and simpler terms. However, he makes the point that our infatuation with knowledge about the inner workings of quarks and leptons is hardly an excuse for still knowing so little about the larger-scale interactions of atoms, which, in my view, is an entirely legitimate criticism of modern physics that you do not address in your review.