Physicist Murray Gell-Mann, one of the greatest physicists of the second half of the 20th century, died on Friday, May 24 at the age of 89. This post was written in 2013, on the 50th anniversary of his first paper on quarks, which he proposed in 1963.
To commemorate the 50th anniversary of Murray Gell-Mann's first paper on quarks, Gell-Mann biographer George Johnson has written several terrific posts about one of the truly great theorists—and characters—of modern physics. See here, here and here.
I had the good fortune (and Gell-Mann, perhaps, the bad) to interview Gell-Mann twice: in 1991, for a profile in Scientific American; and in 1995, when I was researching an article on "chaoplexity" (my term for complexity and its antecedent, chaos). The latter interview took place at the Santa Fe Institute, a leading center of complexity studies, which Gell-Mann helped found. To my surprise, Gell-Mann disparaged the hope that complexity research would yield profound new laws of nature, such as a force that counters the tendency of all systems to become more disordered.
In my 1996 book The End of Science, I cited Gell-Mann's views to advance my thesis that science would not yield insights into nature comparable to natural selection, the double helix, quantum mechanics, relativity. Gell-Mann was not amused. Last summer, he suggested that I receive an Ig Nobel Award for advancing the "ridiculous theory that science is mined out." But his main beef with me is my criticism of string theory, not of complexity.
Read George Johnson's posts on Gell-Mann. Then, if you'd like a different perspective, take a look at what follows, an edited version of my profile of Gell-Mann in The End of Science:
Murray Gell-Mann is a master reductionist. He won a Nobel Prize in 1969 for finding a unifying order beneath the alarmingly diverse particles streaming from accelerators in the 1950s. He called his particle-classification system the Eight-fold way, after the Buddhist road to wisdom. (The name was meant to be a joke, he emphasized; he is not one of these flakey New Age types who thinks physics and Eastern mysticism have something in common.)
He showed the same flair for discerning unity in complexity--and for coining terms--when he proposed that neutrons, protons and a host of other shorter-lived particles consist of triplets of more fundamental entities, which he dubbed "quarks." Gell-Mann's quark theory has been amply demonstrated in accelerators, and it remains a cornerstone of the standard model of particle physics.
Gell-Mann is fond of recalling how he stumbled on the neologism quark while perusing James Joyce's gobbledygookian masterpiece Finnegans Wake. (The passage reads, "Three quarks for Muster Mark!") This anecdote serves notice that Gell-Mann's intellect is far too powerful and restless to be satisfied by particle physics alone.
According to a "personal statement" that he distributes to reporters, his interests include not only physics and modernist literature but also nuclear arm-control, natural history, human history, population growth, sustainable human development, archaeology and linguistics. Gell-Mann has at least some familiarity with all the world's major languages, and he enjoys telling people about the etymology and correct native pronunciation of their names.
Gell-Mann is unquestionably one of this century's most brilliant scientists. (His literary agent, John Brockman, once said that Gell-Mann "has five brains, and every one is smarter than yours.") He is also one of the most annoying, because of his fondness for dwelling on his own talents and belittling those of others.
Gell-Mann displayed this trait almost immediately after we met in 1991, when I interviewed him in a New York City restaurant. I had barely sat down when Gell-Mann began to tell me—as I set out my tape recorder and yellow pad—that science writers are "ignoramuses" and a "terrible breed," who invariably get things wrong; only scientists are qualified to present their work to the masses.
As time went on, I felt less offended, since Gell-Mann obviously held many of his scientific peers in contempt as well. After a series of demeaning comments about other physicists, Gell-Mann said, "I don't want to be quoted insulting people. It's not nice. Some of these people are my friends." [*See the end of this post for a story about how our meeting ended.]
I interviewed Gell-Mann again in 1995 at the Santa Fe Institute, a small but influential research center dedicated to the study of complex systems. Gell-Mann was one of the first major scientists to climb aboard the complexity bandwagon. He helped found the Santa Fe Institute and became its first full-time professor in 1993, after decades of teaching at Caltech.
For a putative leader of chaoplexity, Gell-Mann espoused a worldview remarkably similar to that of the arch-reductionist Steven Weinberg--although Gell-Mann did not see the convergence. "I have no idea what Weinberg said in his book," Gell-Mann replied when I asked if he agreed with Weinberg's comments on reductionism in his 1992 book Dreams of a Final Theory. "But if you read mine you saw what I said about it."
Gell-Mann then reiterated themes of his 1994 book The Quark and the Jaguar. (See George Johnson's discussion of the book's tortuous genesis.) Gell-Mann (like Weinberg) views science as a hierarchy. At the top are theories that apply everywhere in the known universe, such as the second law of thermodynamics and his own quark theory. Other theories, such as those related to genetic transmission, apply only here on earth, and the phenomena they describe entail a great deal of randomness and historical circumstance.
"With biological evolution we see a gigantic amount of history enters," he said, "huge numbers of accidents that could have gone different ways and produced different life forms than we have on the earth, constrained of course by selection pressures. Then we get to human beings, and the characteristics of human beings are determined by huge amounts of history. But still, there's clear determination from the fundamental laws and from history, or fundamental laws and specific circumstances."
Gell-Mann's reductionist predilections can be seen in his attempts to substitute his own neologism, plectics, for complexity. Plectics "is based on the Indo-European word plec, which is the basis of both simplicity and complexity. So in plectics we try to understand the relation between the simple and the complex, and in particular how we get from the simple fundamental laws that govern the behavior of all matter to the complex fabric that we see around us," he said. (Unlike quark, plectics has not caught on. I have never heard anyone besides Gell-Mann use the term—except to deride Gell-Mann's fondness for it.)
I asked if Gell-Mann agreed with what his Santa Fe colleague and fellow Nobel laureate Phil Anderson said in his famous 1972 essay "More Is Different." "I have no idea what he said," Gell-Mann replied disdainfully. (Gell-Mann liked to call Anderson's field "squalid-state physics.") I explained Anderson's idea that complex phenomena such as life and consciousness require their own theories; you cannot reduce them to physics.
"You can! You can!" Gell-Mann cried. "Did you read what I wrote about this? I devoted two or three chapters to this!" Biological phenomena, he acknowledged, obviously cannot be easily deduced from fundamental physical principles, but that does not mean organisms are ruled by their own laws operating independently of the laws of physics. "I founded a whole institute to try to react against excessive reductionism," Gell-Mann said, "but reductionism in principle hasn't been proved wrong."
Gell-Mann rejected the possibility--raised by Stuart Kauffman and others--that there might be a still-undiscovered force of nature that organizes matter into ever-more complex forms in spite of the supposedly inexorable increase of entropy. This issue, too, is settled, Gell-Mann said. The universe began in a "wound-up" state far from thermal equilibrium. As it winds down, disorder increases, on average, throughout the system, but there can be local violations of that tendency.
"It's a tendency, and there are lots and lot of eddies in that process," said. "That's very different from saying complexity increases. The envelope of complexity grows, expands. It's obvious from these other considerations it doesn't need another new law, however!"
The universe creates what Gell-Mann calls "frozen accidents"--stars, galaxies, planets, stones, trees, humans--complex structures that serve as a foundation for the emergence of still more complex structures.
"As a general rule, more complex life forms emerge, more complex computer programs, more complex astronomical objects emerge in the course of non-adaptive stellar and galactic evolution and so on. But! If we look very, very, very far into the future, maybe it won't be true any more!" Eons from now the era of complexity could end, and the universe could degenerate into "photons and neutrinos and junk like that and not a lot of individuality." Entropy will get us after all.
"What I'm trying to oppose is a certain tendency toward obscurantism and mystification," Gell-Mann continued. He emphasized that there is still much to be understood about complex systems. "There's a huge amount of wonderful research going on. What I say is that there is no evidence that we need some--I don't know how else to say it--something else!"
Gell-Mann, as he said "something else," wore a huge sardonic grin, as if he could scarcely contain his amusement at the foolishness of those who might disagree with him.
Gell-Mann noted that "the last refuge of the obscurantists and mystifiers is self-awareness, consciousness." Humans are obviously more intelligent and self-aware than other animals, but they are not qualitatively different. "Again, it's a phenomenon that appears at a certain level of complexity and presumably is emergent from the fundamental laws plus an awful lot of historical circumstances. Roger Penrose has written two foolish books based on the long discredited fallacy that Godel's theorem has something to do with consciousness requiring"--pause--"something else."
Particle physics, Gell-Mann said, still represents science's best hope of discovering profound new principles of nature. Gell-Mann believed superstring theory would probably be confirmed as a unified theory of all fundamental forces early in the next millennium.
But would such a far-fetched theory--with its extra dimensions and infinitesimal stringy particles--ever really be accepted? After I asked this question, Gell-Mann stared at me, as if I'd just confessed to belief in angels. "You're looking at science in this weird way, as if it were a matter of an opinion poll," Gell-Mann said. "The world is a certain way, and opinion polls have nothing to do with it! They do exert pressures on the scientific enterprise, but the ultimate selection pressure comes from comparison with the world." He urged me to ignore "crazy criticisms of superstring theory."
Gell-Mann also had no problem with theories that posit the existence of other universes; in fact, he is a proponent of the many-worlds interpretation of quantum mechanics. The goal of physics, he said, should be to determine whether our particular cosmos is probable or improbable. "If it turns out that we're in a very improbable universe," Gell-Mann admitted, "it'll look funny." But physicists can always fall back on the anthropic principle, he said, to explain why we happen to find ourselves in this particular universe.
Is science finite or infinite? For once, Gell-Mann did not have a pre-packaged answer. "That's a very difficult question," he replied soberly. "I can't say." His view of how complexity emerges from fundamental laws, he said, "still leaves open the question of whether the whole scientific enterprise is open-ended. After all, the scientific enterprise can also concern itself with all sorts of details."
One reason why Gell-Mann is so insufferable is that he is almost always right. His assertion that research on complex systems will not yield something else—a profound new principle of nature—will probably prove to be correct. Gell-Mann errs—dare one say it?—only in his judgment of string theory, which will never be as empirically validated and hence accepted as, say, quark theory.
*One final story about Gell-Mann: After our meal together in New York in 1991, I hired a limousine to take us to the airport, where Gell-Mann was catching a plane. Before we parted, he fretted that he did not have enough money for a taxi after his plane landed; if I could give him $40 in cash, he'd write me a check. As Gell-Mann handed me the check, he suggested that I not cash it, since his signature would probably be quite valuable. I cashed the check but kept a photocopy.
Photo: Wikimedia Commons, http://commons.wikimedia.org/wiki/File:Murray_Gell-Mann_at_Lection.JPG.