Steven Weinberg’s Pointless Final Theory
In 1995, I asked Steven Weinberg if it’s too much to ask that a final theory of physics make the world intelligible. “Yes, it’s too much to ask,” he replied. Photo: U. Texas.
HOBOKEN, JANUARY 27, 2025. The time seems right to post this profile--adapted from my 1996 book The End of Science--of brutally honest physicist Steven Weinberg (1933-2021). – John Horgan
With his crabapple cheeks and silver, red-tinged hair, Steven Weinberg looks like a large, solemn elf. He would make a terrific Oberon, King of the Fairies in A Midsummer Night's Dream. And like a Fairy King, Weinberg possesses uncanny intuitions about nature.
He won a Nobel prize in 1979 for helping show that, just as electricity and magnetism are aspects of a single force, so electromagnetism and the weak nuclear force spring from a deeper electroweak force. This achievement emboldened physicists seeking a unified theory of all forces, which Weinberg calls a “final theory.”
Weinberg wrote his 1993 book Dreams of a Final Theory to convince non-physicists to care about and support—by funding particle accelerators--the quest for the ultimate explanation. The simple question Why?, he writes, has propelled scientists deeper and deeper into nature’s heart. "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 release of Dreams of a Final Theory. He was in an expansive mood, wondering what it would be like to chat with talk-show host Charlie Rose later. Eager to impress the great physicist, I mentioned that I had just interviewed White House science advisor Jack Gibbons. Gibbons had hinted that the U.S. might pull the plug on the Superconducting Supercollider, the gargantuan accelerator that was supposed to propel particle physics into the next century.
Weinberg scowled, muttering something about society's lack of appreciation for basic research. The irony is that Weinberg, because he is so brutally honest, has a hard time explaining why we should support his field.
In Dreams, Weinberg reiterates a comment he made in an earlier book: "The more the universe seems comprehensible, the more it also seems pointless." Although this line has "dogged him," Weinberg defends it. "As we have discovered more and more fundamental physical principles,” he writes, “they seem to have less and less to do with us."
All our Why's, Weinberg implies, will culminate in a Because. So why should we care again?
Two years later, Weinberg was mourning the death of the Superconducting Supercollider when I interviewed him at the University of Texas at Austin. As he spoke, he kept sighing, grimacing, rubbing his eyes, even as his deep, sonorous voice rolled forward.
It is a "terrible time for particle physics," he said. "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."
Brilliant students are still entering particle physics, Weinberg said, students "better than we deserve, probably.” With the Supercollider gone, prospects for the field are dim.
Weinberg still clung to his hope that physicists will discover a final theory. The leading candidate is string theory, which says everything springs from infinitesimal strings wriggling in 10 or more dimensions. No experiment can detect the strings and extra dimensions, Weinberg acknowledged. But if the theory accounts for all current experimental data--the masses of particles and strengths of forces--physicists will 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."
At this moment, someone might be posting a final theory on the Internet. "If she"--Weinberg added, with an emphasis on she--"got results that agreed with experiment, then you would say, 'That's it,'" even if researchers lack direct evidence; 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,” Weinberg said, “and atoms are much further away from direct perception than chairs. But I don't see any philosophical discontinuity there."
Abruptly Weinberg rose and prowled around his office. He reiterated that a final theory would represent the bedrock of all knowledge. To be sure, some complex phenomena, like turbulence, life, consciousness, require their own theories. But if you ask why those theories are true, that question takes you down toward the final theory, upon which everything rests. "That's what makes science a hierarchy,” Weinberg said. “And it is a hierarchy. It's not just a random net."
Many scientists loathe that truth, Weinberg said, but there is no escaping it. "Their final theory is what our final theory explains." If neuroscientists ever explain consciousness, 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."
Weinberg portrayed the final theory in increasingly negative terms. Science will certainly continue after a final theory, he said, perhaps forever, but it will be in some sense anti-climactic. "There will a sense of sadness" in achieving a final theory, he said, since it will bring to a close the great quest for fundamental knowledge.
Asked whether string theory could have practical applications, 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 science, but applied string theory is "hard to conceive."
He doubted the final theory would resolve the notorious paradoxes posed by quantum mechanics. "I tend to think these are just puzzles in the way we talk about quantum mechanics." One possible solution is the many-worlds hypothesis, which explains why measurement seems to force an electron to choose only one path out of the many allowed by a wave function: the electron follows all possible paths--in separate universes.
This hypothesis has troubling implications, 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 finished 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 moral guidance. "We've learned to absolutely disentangle value judgments from truth judgements," 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 has little patience for those who suggest that a final theory will reveal "the mind of God," as Stephen Hawking once put it. Quite the contrary: Weinberg hopes a final theory will 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."
In Dreams of a Final Theory, Weinberg asks, What kind of divine plan, or planner, allows the Holocaust and countless other evils to happen? Some physicists, intoxicated by the power of their mathematical models, have suggested that "God is a geometer." Weinberg retorts, in effect, that if God is a geometer, He is also callous, and Weinberg wants nothing to do with Him.
I asked what gave Weinberg 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.
To recap: Weinberg’s final theory won’t be meaningful, or even intelligible, except for a tiny, highly trained (indoctrinated?) elite. It won’t offer any consolation, or moral guidance. It won’t yield any practical benefits. Again, why should we care?
In the 30 years since I spoke to Weinberg in Austin, the quest for a final theory has lost its glamour. String theory, for a half century the leading contender for a unified theory of physics, appears to be a dead end. But in one sense, Weinberg, who died in 2021, has been vindicated: The world keeps bearing out his tragic take on the human condition.
Further Reading:
If you like this piece, see my free online profiles of physicists Edward Witten, John Wheeler, David Bohm, Mitchell Feigenbaum, Freeman Dyson and Francis Crick (trained as a physicist). And check out The End of Science, which has many more like profiles like these.
Is Ultimate Truth an Equation? Nah
Physicists Teleport Bullshit Through “Wormhole”!
Multiverses Are Pseudoscientific Bullshit
Moby Dick and Hawking’s “Ultimate Theory”
I also delve into the quest for a final theory in my free, online book My Quantum Experiment.