This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
In my last post Steven Weinberg, one of history’s greatest physicists, answers questions about progress—or the lack thereof–in particle physics, cosmology and politics. He comments on, among other topics, strings, multiverses, the anthropic principle, religion, evil, nuclear weapons and human progress. To give readers more background on Weinberg, I’m reproducing here the profile of him in my 1996 book The End of Science, just republished by Basic Books with a new preface. The Weinberg section of my book came right after my profile of string theorist Edward Witten. I called Witten a “naive realist” and argued that string theory was untestable; physicists would need a particle accelerator 1,000 light years around to probe the Planck scale, where strings supposedly shimmy and shake. The headline for the Weinberg profile was “Nightmares of a Final Theory.” Here it is, lightly edited:
If Edward Witten is a naive realist, Steven Weinberg is an extremely sophisticated one–too sophisticated, perhaps, for the good of his own field. Weinberg, like Edward Witten and almost all particle physicists, believes in the universality–the absoluteness–of theories such as quantum mechanics and general relativity. But what makes Weinberg such an interesting spokesman for his tribe is that he, unlike Witten, is acutely aware that his belief is just that, a belief; Weinberg knows that he is speaking with a philosophical accent.
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With his crabapple cheeks, vaguely Asian eyes and silver hair still tinged with red, Weinberg resembles an elf, a large, dignified elf. He would make an excellent Oberon, King of the Fairies in A Midsummer Night’s Dream. And like a Fairy King, Weinberg has demonstrated a powerful affinity for the mysteries of nature, an ability to discern subtle patterns within the froth of data streaming from particle accelerators. Weinberg received a Nobel prize in 1979 for his role in developing electroweak theory.
In his 1993 book Dreams of a Final Theory, he managed to make reductionism sound romantic. Particle physics is the culmination of an epic quest, “the ancient search for those principles that cannot be explained in terms of deeper principles.” The force compelling science, he pointed out, is the simple question “Why?” That question has led physicists deeper and deeper into the heart of nature. “It seems likely that if we keep this up,” he wrote, “the convergence of explanations down to simpler and simpler principles will eventually come to an end in a final theory.”
I first met Weinberg in 1993 at a dinner held in New York to celebrate the publication of Dreams of a Final Theory. He was in an expansive mood, dispensing jokes and anecdotes about famous colleagues and wondering what it would be like to chat with the talk-show host Charlie Rose later that night. Eager to impress the great physicist, I began name-dropping. I mentioned that Freeman Dyson had recently told me the whole notion of a final theory is a pipe dream.
Weinberg smiled. The majority of his colleagues, he assured me, believed in a final theory, although many of them preferred to keep that belief private; Dyson is a notorious contrarian. I dropped another name: Jack Gibbons, whom the newly elected Bill Clinton had just named science advisor. I had just interviewed Gibbons, I said, and Gibbons had hinted that the U.S. alone might not be able to afford the Superconducting Supercollider, the gargantuan particle accelerator that was supposed to propel particle physics into the next century. Weinberg scowled and shook his head, muttering something about society’s disturbing lack of appreciation for the intellectual benefits of basic research.
The irony was that Weinberg himself, in Dreams of a Final Theory, offered little or no reason why society should support further research in particle physics. He was careful to acknowledge that neither the Superconducting Supercollider nor any other earthly accelerator could provide direct confirmation of a final theory; physicists would eventually have to rely on mathematical elegance and consistency as guides. Moreover, a final theory might have no practical value.
Weinberg’s most extraordinary admission was that a final theory might not be meaningful, in human terms. Quite the contrary. He reiterated an infamous comment he had made in an earlier book: “The more the universe seems comprehensible, the more it also seems pointless.” Although the comment had “dogged him ever since,” Weinberg refused to back away from it. In fact, he elaborated on the remark: “As we have discovered more and more fundamental physical principles they seem to have less and less to do with us.”
Weinberg seemed to be acknowledging that all our Why’s would eventually culminate in a Because. His vision of the final theory evoked The Hitchhiker’s Guide to the Universe by Douglas Adams. In this science-fiction comedy, scientists finally discover the answer to the riddle of the universe, and the answer is…42.
The Superconducting Supercollider was dead and buried when I met Weinberg two years later at the University of Texas at Austin. His spacious office was cluttered with periodicals, including Foreign Affairs, Isis, The Skeptical Inquirer and American History Review as well as physics journals. Along one wall ran a blackboard laced with the obligatory mathematical scribbles. Weinberg spoke with what seemed to be considerable effort. He kept sighing, grimacing, squeezing his eyes shut, rubbing them, even as his deep, sonorous voice rolled forward. He had just eaten lunch, and was probably experiencing post-prandial fatigue. But I preferred to think he was brooding over the tragic dilemma of particle physicists: they are damned if they achieve a final theory and damned if they don’t.
It is a “terrible time for particle physics,” Weinberg admitted. “There’s never been a time when there’s been so little excitement in the sense of experiments suggesting really new ideas or theories being able to make new and qualitatively different kinds of predictions that are then borne out by experiments.” With the Supercollider dead and plans for other new accelerators in the U.S. stalled for lack of funding, the prospects for the field were gloomy. Oddly enough, brilliant students were still entering the field, students “better than we deserve, probably,” Weinberg added.
Weinberg shared Edward Witten’s belief in the absolute truth of physics, and his faith that intelligent aliens elsewhere in the universe would discover the same theories. But Weinberg was acutely aware of the philosophical indefensibility of this position. He recognized that “the techniques by which we decide on the acceptance of physical theories are extremely subjective.” It would always be possible for clever philosophers to make a case that the particle physicists “are just making it up as they go along.”
On the other hand, Weinberg told me, the standard model of particle physics, “whatever the aesthetics were, [has] by now been tested as few theories have been, and it really works. If in fact it was just a social construct it would have fallen apart long before this.”
Weinberg realized that physicists would never be able to prove a theory is final, in the same way that mathematicians prove theorems; but if the theory accounted for all experimental data–the masses of all particles, the strengths of all forces–physicists would eventually cease questioning it.
“I don’t feel I was put here to be sure of anything,” Weinberg said. “It seems to me a lot of philosophy of science going back to the Greeks has been poisoned by the search for certainty, which seems to me a false search. Science is too much fun to sit around wringing our hands because we’re not certain about things.”
Even as we spoke, Weinberg suggested, someone might be posting a final theory of physics on the Internet. “If she,”–Weinberg added, with the slightest pause and emphasis on she–”got results that agreed with experiment, then you would say, ‘That’s it,’” even if researchers could never provide direct evidence of the strings themselves or the extra dimensions they supposedly inhabit; after all, the atomic theory of matter was accepted because it worked, not because experimenters could make pictures of atoms.
“I agree strings are much farther away from direct perception than atoms, and atoms are much further away from direct perception than chairs, but I don’t see any philosophical discontinuity there.”
There was little conviction in Weinberg’s voice. Abruptly, he rose and began prowling around the room. He picked up odd objects, fondled them distractedly, put them down, while continuing to speak. He reiterated his belief that a final theory of physics would represent the most fundamental possible achievement of science–the bedrock of all other knowledge. To be sure, some complex phenomena, such as turbulence, or economics, or life, require their own special laws and generalizations. But if you ask why those principles are true, Weinberg added, that question takes you down toward the final theory of physics, upon which everything rests. “That’s what makes science a hierarchy. And it is a hierarchy. It’s not just a random net.”
Many scientists cannot abide hearing that truth, Weinberg said, but there is no escaping it. “Their final theory is what our final theory explains.” If neuroscientists ever explain consciousness, for example, they will explain it in terms of the brain, “and the brain is what it is because of historical accidents and because of universal principles of chemistry and physics.” Science will certainly continue after a final theory, perhaps forever, but it will be in some sense anti-climactic. “There will a sense of sadness” about the achievement of a final theory, Weinberg said, since it will bring to a close the great quest for fundamental knowledge.
As Weinberg continued speaking, he seemed to portray the final theory in increasingly negative terms. Asked whether there will ever be such a thing as applied string theory, as some enthusiasts have suggested, Weinberg grimaced. He cautioned that “the sands of scientific history are white with the bones of people” who failed to foresee applications of developments in science, but applied string theory was “hard to conceive.”
He also doubted that the final theory would resolve all the notorious paradoxes posed by quantum mechanics. “I tend to think these are just puzzles in the way we talk about quantum mechanics,” Weinberg said.
One way to eliminate these puzzles, he added, is to adopt the many-worlds interpretation of quantum mechanics, which was first proposed in the 1950′s. It attempts to explain why the act of observation by a physicist seems to force a particle such as an electron to choose only one path out of the many allowed by quantum mechanics; according to the many-worlds interpretation, the electron actually follows all possible paths, but in separate universes.
This explanation does have its troubling aspects, Weinberg conceded. “There may be another parallel time track where John Wilkes Booth missed Lincoln and…” Weinberg paused. “I sort of hope that whole problem will go away, but it may not. That may be just the way the world is.”
Is it too much to ask that a final theory make the world intelligible? Before I could finish the question, Weinberg was nodding. “Yes, it’s too much to ask,” he replied. The proper language of science is mathematics, he reminded me. A final theory “has to make the universe appear plausible and somehow or other recognizably logical to people who are trained in that language of mathematics, but it may be a long time before that makes sense to other people.”
Nor will a final theory provide humanity with any guidance in conducting its affairs. “We’ve learned to absolutely disentangle value judgments from truth judgments,” Weinberg said. “I don’t see us going back to reconnect them.” Science “can certainly help you find out what the consequences of your actions are, but it can’t tell you what consequences you ought to wish for. And that seems to me to be an absolute distinction.”
Weinberg had little patience for those who suggest that a final theory will reveal the purpose of the universe, or “the mind of God,” as Stephen Hawking once put it. Quite the contrary: Weinberg hoped that a final theory would eliminate the wishful thinking, mysticism and superstition that pervades much of human thought, and even physics.
“As long as we don’t know the fundamental rules,” he said, “we can hope that we’ll find something like a concern for human beings, say, or some guiding divine plan built into the fundamental rules. But when we find out that the fundamental rules of quantum mechanics and some symmetry principles are very impersonal and cold, then it’ll have a very demystifying effect. At least that’s what I’d like to see.”
His face hardening, Weinberg continued: “I certainly would not disagree with people who say that physics in my style or the Newtonian style has produced a certain disenchantment. But if that’s the way the world is, it’s better we find out. I see it as part of the growing up of our species, just like the child finding out there is no tooth fairy. It’s better to find out there is no tooth fairy, even though a world with tooth fairies in it is somehow more delightful.”
Weinberg was well aware that many people hungered for a different message from physics. In fact, earlier that day he had read in The New York Times that the physicist Paul Davies had received a million-dollar prize for work “advancing public understanding of God or spirituality.” Davies had written numerous books, notably The Mind of God, published in 1992, suggesting that the laws of physics reveal a plan underlying nature, a plan in which human consciousness may play a central role.
After telling me about Davies’s prize, Weinberg chuckled mirthlessly. “I was thinking of cabling Davies and saying, ‘Do you know of any organization that is willing to offer a million dollar prize for work showing that there is no divine plan?’”
In Dreams of a Final Theory, Weinberg had dealt rather harshly with all this talk of divine plans. He raised the embarrassing issue of human evil and suffering. What kind of plan is it that allows the Holocaust, and countless other evils, to happen? What kind of planner?
Many physicists, intoxicated by the power of their mathematical theories, have suggested that “God is a geometer.” Weinberg retorted, in effect, that if God is a geometer, then He is a cruel or callous geometer, and Weinberg wanted nothing to do with Him.
I asked Weinberg what gave him the fortitude to sustain such a bleak vision of the human condition. “I sort of enjoy my tragic view,” he replied with a little smile. “After all, which would you rather see, a tragedy or–” He hesitated, his smile fading. “Well, some people would prefer to see a comedy. But… I think the tragic view adds a certain dimension to life. Anyway, it’s the best we have.” He stared out his office window, brooding.
Fortunately, perhaps, for Weinberg, his view did not include the infamous tower from which a deranged University of Texas student, Charles Whitman, had shot 14 people to death in 1966. Weinberg’s office overlooks a graceful, Gothic church that serves as the university’s theological seminary. But Weinberg did not seem to be looking at the church–or, for that matter, at anything else in the material world.
Further Reading:
“Was I Wrong about ‘The End of Science’?”
See also my Q&As with physicists George Ellis, Carlo Rovelli, Edward Witten, Garrett Lisi, Paul Steinhardt and Lee Smolin.
Photo (date unspecified): Larry Murphy, University of Texas, http://web2.ph.utexas.edu/utphysicshistory/UTexas_Physics_History/Steven_Weinberg.html