June 1, 2005
PULL THE STRING AND IT ALL UNRAVELS:
Viewpoints on String Theory: Sheldon Glashow (The Elegant Universe, NOVA)
NOVA: When you first heard of string theory, what did you think of it?
Glashow: String theory has had a long and wonderful history. It originated as a technique to try to understand the strong force. It was a calculational mechanism, a way of approaching a mathematical problem that was too difficult, and it was a promising way, but it was only a technique. It was a mathematical technique rather than a theory in itself. Later on this primitive string theory that existed in the 1970s became combined with the theory of supersymmetry—which is another development in particle physics, a very interesting development that may have experimental consequences or not—to form superstring theory, which is very elaborate and very mathematical and founded on the principle that we must form a quantum theory that describes all of the forces of nature, including the force of gravity.
Now, the force of gravity is known to be very weak, and that means that it involves a parameter of distance that is many, many powers of ten smaller than the size of the proton or the smallest sizes that we can or will investigate in the laboratory. Conversely, it means that quantum gravity becomes apparent at energies that are simply far beyond the reach of any particle accelerator that exists or any accelerator that is ever likely to exist.
“The string theorists have a theory that appears to be consistent and is very beautiful, and I don’t understand it.”
So the nature of the quest to form a theory of all of the forces of nature, including gravity, drives on to a domain of energies and distances that is inaccessible to the experiment. No experiment can ever check up what's going on at the distances that are being studied. No observation can relate to these tiny distances or high energies. All we can do is look at the distant consequences, 10 or 20 orders of magnitude removed from these effects.
The string theorists have a theory that appears to be consistent and is very beautiful, very complex, and I don't understand it. It gives a quantum theory of gravity that appears to be consistent but doesn't make any other predictions. That is to say, there ain't no experiment that could be done nor is there any observation that could be made that would say, "You guys are wrong." The theory is safe, permanently safe. I ask you, is that a theory of physics or a philosophy?
NOVA: Is it science then, if it's not testable?
Glashow: What the string theorists do is arguably physics. It deals with the physical world. They're attempting to make a consistent theory that explains the interactions we see among particles and gravity as well. That's certainly physics, but it's a kind of physics that is not yet testable. It does not make predictions that have anything to do with experiments that can be done in the laboratory or with observations that could be made in space or from telescopes.
NOVA: If it's not testable, how useful is it?
Glashow: It leads to many interesting ideas. It is important in mathematics. String theory has had an impact on modern mathematics. They may even have a practical impact some day, these things that string theorists do. One never knows, just as number theory, the most useless of the mathematical sciences, has given us cryptography and has given us a secure way to encode information. The string theorist may also produce something equally useful. May. So it is science, it is physics, it is mathematics. It does stimulate ideas in related fields.
But in and of itself, it has failed in its primary goal, which is to incorporate what we already know into a consistent theory that explains gravity as well. The new theory must incorporate the old theory and say something more. String theory has not succeeded in this fashion. String theory has said something more, but it does not incorporate the details of the structure that preceded it, that is to say the standard theory of elementary particles. Until it does that, it is not yet physics in a conventional form. It is a perhaps promising corner of physics that may some day say things about the world. But today they're saying things about string theory to one another.
NOVA: Is there any danger in this for physics in general?
Glashow: There is today a disconnect in the world of physics. Let me put it bluntly. There are physicists, and there are string theorists. Of course the string theorists are physicists, but the string theorists in general will not attend lectures on experimental physics. They will not be terribly concerned about the results of experiments. They will talk to one another.
“We don’t listen to them, and they don’t listen to us.”
At Harvard today there's a very strong group of string theorists upstairs on the fourth floor of the Jefferson Laboratory. Each week there are visitors from around the world giving lectures. I've occasionally attempted to attend these lectures. I can't understand the titles, and I can't understand the lectures, and it's not just me. I think most theoretical physicists who are not themselves string theorists could not possibly follow these lectures. In other words, we don't listen to them, and they don't listen to us. We can't understand them, and what we do is not of any direct interest to them.
It is a new discipline. Unfortunately, many of us have nothing in common with them, and many of them have nothing in common with us, except intellectually. Just as there's a biology department that I respect and understand a little bit, there's a philosophy department that I respect and understand a little bit, so there's a string theory structure. That's a problem, I think, in physics.
NOVA: Why is it a problem?
Glashow: The physics and astronomy enterprises in this country spend a great deal of money to do experiments on Earth and in the heavens. There are orbiting observatories, there are laboratories deep underground, there are accelerators in many countries, and these guys produce a lot of data in order to lead us to construct a better and more useful theory of nature. And it turns out that the best and the brightest young theorists, instead of being concerned about the experimental enterprise, are going off among themselves and doing their thing with the doors closed. Because no one else is interested in coming, they're all making these secret signs to one another and putting incomprehensible formulas together that to them are, of course, central and simple and predictive and whatnot but to us are a little bit irrelevant.
Now, what happens if there are suddenly some major experimental discoveries? There is a big accelerator, the Large Hadron Collider, which is scheduled to be completed in another five years or so. That should make lots of discoveries. Who will be interested in trying to fit these discoveries into the theory? It will be people like me, except we may be dead by then or if not we'll be rather old. Or it will be the young theoretical physicists, but the young theoretical physicists are doing string theory, and they ain't interested in the results of the experiments. Not now, and not then. So who's going to be there to continue the role of building a better theory of particle physics? That's why it's a problem.
NOVA: What would string theory need to do to make a believer out of you?
Glashow: Well, you must understand that I don't understand string theory, so I can't describe its inner nature to any extent. But I could imagine that string theory would succeed in encompassing the standard model. It might then answer any number of outstanding questions. Why is the muon, some dumb particle, 200 times heavier than the electron? Why is the proton about 2,000 times heavier than the electron? Why is the electric charge of the electron what it is? Why are there six quarks in nature? Why not seven or eleven or five? There are many, many "why" questions. Also a number of 'how' questions. What is the mechanism that causes the weak interactions to be weak and the electromagnetic interactions not weak?
All kinds of questions remain. Many have to do with cosmology. How did the universe originate? How did the galaxies become distributed in space like the suds in the kitchen sink, as one of my colleagues has described it? Why is the cosmological constant apparently very tiny but non-zero and has a peculiar value that leads the universe to expand more rapidly?
These are some of the questions. I can give you a list of 30 or 40 questions. If they answer three or four of them, I get interested in string theory. They're answering a bunch of questions, but their questions lie completely within string theory, which has nothing to do with experiment.
Darwin's Influence on Modern Thought: This article is based on the September 23, 1999, lecture that Mayr delivered in Stockholm on receiving the Crafoord Prize from the Royal Swedish Academy of Science (Ernst Mayr)
Darwin founded a new branch of life science, evolutionary biology. Four of his contributions to evolutionary biology are especially important, as they held considerable sway beyond that discipline. The first is the non-constancy of species, or the modern conception of evolution itself. The second is the notion of branching evolution, implying the common descent of all species of living things on earth from a single unique origin. Up until 1859, all evolutionary proposals, such as that of naturalist Jean-Baptiste Lamarck, instead endorsed linear evolution, a teleological march toward greater perfection that had been in vogue since Aristotle's concept of Scala Naturae, the chain of being. Darwin further noted that evolution must be gradual, with no major breaks or discontinuities. Finally, he reasoned that the mechanism of evolution was natural selection.
These four insights served as the foundation for Darwin's founding of a new branch of the philosophy of science, a philosophy of biology. Despite the passing of a century before this new branch of philosophy fully developed, its eventual form is based on Darwinian concepts. For example, Darwin introduced historicity into science. Evolutionary biology, in contrast with physics and chemistry, is a historical science - the evolutionist attempts to explain events and processes that have already taken place. Laws and experiments are inappropriate techniques for the explication of such events and processes. Instead one constructs a historical narrative, consisting of a tentative reconstruction of the particular scenario that led to the events one is trying to explain.
-ERNST MAYR: WHAT EVOLUTION IS: Introduction by Jared Diamond (Edge, 10.31.01)
EDGE: To what extent has the study of evolutionary biology been the study of ideas about evolutionary biology? Is evolution the evolution of ideas, or is it a fact?
ERNST MAYR: That's a very good question. Because of the historically entrenched resistance to the thought of evolution, documented by modern-day creationism, evolutionists have been forced into defending evolution and trying to prove that it is a fact and not a theory. Certainly the explanation of evolution and the search for its underlying ideas has been somewhat neglected, and my new book, the title of which is What Evolution Is, is precisely attempting to rectify that situation. It attempts to explain evolution. As I say in the first section of the book, I don't need to prove it again, evolution is so clearly a fact that you need to be committed to something like a belief in the supernatural if you are at all in disagreement with evolution. It is a fact and we don't need to prove it anymore. Nonetheless we must explain why it happened and how it happens.
One of the surprising things that I discovered in my work on the philosophy of biology is that when it comes to the physical sciences, any new theory is based on a law, on a natural law. Yet as several leading philosophers have stated, and I agree with them, there are no laws in biology like those of physics. Biologists often use the word law, but for something to be a law, it has to have no exceptions. A law must be beyond space and time, and therefore it cannot be specific. Every general truth in biology though is specific. Biological "laws" are restricted to certain parts of the living world, or certain localized situations, and they are restricted in time. So we can say that their are no laws in biology, except in functional biology which, as I claim, is much closer to the physical sciences, than the historical science of evolution.
EDGE: Let's call this Mayr's Law.
MAYR: Well in that case, I've produced a number of them. Anyhow the question is, if scientific theories are based on laws and there aren't any laws in biology, well then how can you say you have theories, and how do you know that your theories are any good? That's a perfectly legitimate question. Of course our theories are based on something solid, which are concepts. If you go through the theories of evolutionary biology you find that they are all based on concepts such as natural selection, competition, the struggle for existence, female choice, male dominance, etc. There are hundreds of such concepts. In fact, ecology consists almost entirely of such basic concepts. Once again you can ask, how do you know they're true? The answer is that you can know this only provisionally by continuous testing and you have to go back to historical narratives and other non-physicalist methods to determine whether your concept and the consequences that arise from it can be confirmed.
EDGE: Is biology a narrative based of our times and how we look at the world?
MAYR: It depends entirely on when in the given age of the intellectual world you ask these questions.
The Evolution of Ernst: Interview with Ernst Mayr: The preeminent biologist, who just turned 100, reflects on his prolific career and the history, philosophy and future of his field On July 5, renowned evolutionary biologist Ernst Mayr celebrated his 100th birthday. He also recently finished writing his 25th book, What Makes Biology Unique?: Considerations on the Autonomy of a Scientific Discipline [Cambridge University Press, in press]. A symposium in Mayr's honor was held at Harvard University on May 10. Scientific American editor and columnist Steve Mirsky attended the symposium and wrote about it for the upcoming August issue. On May 15, Mirsky, Brazilian journalist Claudio Angelo and Angelo's colleague Marcelo Leite visited Mayr at his apartment in Bedford, Mass. (Scientific American, 7/06/04)
Claudio Angelo: What is the book about?Posted by Orrin Judd at June 1, 2005 11:26 PM
Ernst Mayr: What the book is about. (Laughs.) Primarily to show, and you will think that this doesn't need showing, but lots of people would disagree with you. To show that biology is an autonomous science and should not be mixed up with physics. That's my message. And I show it in about 12 chapters. And, as another fact, when people ask me what is really your field, and 50 years or 60 years ago, without hesitation I would have said I'm an ornithologist. Forty years ago I would have said, I'm an evolutionist. And a little later I would still say I'm an evolutionist, but I would also say I'm an historian of biology. And the last 20 years, I love to answer, I'm a philosopher of biology. And, as a matter of fact, and that is perhaps something I can brag about, I have gotten honorary degrees for my work in ornithology from two universities, in evolution, in systematics, in history of biology and in philosophy of biology. Two honorary degrees from philosophy departments.
Steve Mirsky: And the philosophical basis for physics versus biology is what you examine in the book?
EM: I show first in the first chapter and in some chapters that follow later on, I show that biology is as serious, honest, legitimate a science as the physical sciences. All the occult stuff that used to be mixed in with philosophy of biology, like vitalism and teleology-Kant after all, when he wanted to describe biology, he put it all on teleology, just to give an example-all this sort of funny business I show is out. Biology has exactly the same hard-nosed basis as the physical sciences, consisting of the natural laws. The natural laws apply to biology just as much as they do to the physical sciences. But the people who compare the two, or who, like some philosophers, put in biology with physical sciences, they leave out a lot of things. And the minute you include those, you can see clearly that biology is not the same sort of thing as the physical sciences. And I cannot give a long lecture now on that subject, that's what the book is for.
I'll give you an example. In principle, biology differs from the physical sciences in that in the physical sciences, all theories, I don't know exceptions so I think it's probably a safe statement, all theories are based somehow or other on natural laws. In biology, as several other people have shown, and I totally agree with them, there are no natural laws in biology corresponding to the natural laws of the physical sciences.
Now then you can say, how can you have theories in biology if you don't have laws on which to base them? Well, in biology your theories are based on something else. They're based on concepts. Like the concept of natural selection forms the basis of, practically the most important basis of, evolutionary biology. You go to ecology and you get concepts like competition or resources, ecology is just full of concepts. And those concepts are the basis of all the theories in ecology. Not the physical laws, they're not the basis. They are of course ultimately the basis, but not directly, of ecology. And so on and so forth. And so that's what I do in this book. I show that the theoretical basis, you might call it, or I prefer to call it the philosophy of biology, has a totally different basis than the theories of physics.
If I say so myself, I think this is going to be an important book. The philosophers of course will ignore it, it's bothersome, it doesn't fit into their thinking. And so the best way is to just forget it, put it under the rug. But those who take it seriously will say, well, gee, that's not something I know how to deal with. But this fellow Mayr seems to have something here, nobody else has made that so clear, nobody else has shown that, really, biology, even though it has all the other legitimate properties of a science, still is not a science like the physical sciences. And somehow or other, the somewhat more enlightened philosophers will say we really ought to deal with that. But so far they haven't.