Multiverses Are Pseudoscientific Bullshit
I dig fictional depictions of multiverses, like “Everything Everywhere All at Once,” but I don’t dig multiverse theories, which are escapist pseudoscience.
February 21, 2024. Way back in 1990 I tossed off a fluffy item for Scientific American, “Here a Universe, There a Universe,” about whether our cosmos might be just one in an “infinitude,” as several theories of physics implied. I kept the tone light, because I didn’t want readers to take these cosmic conjectures too seriously. After all, there was no way to prove or disprove the existence of other universes.
Today, physicists still lack evidence of other universes, or even good ideas for obtaining evidence. Many nonetheless insist our cosmos is just a bubble in an oceanic “multiverse.” Physicist Sean Carroll is an especially passionate multiverse advocate. His faith in the multiverse stems from his faith in quantum mechanics, which he sees as our best account of reality.
“As far as we currently know,” Carroll writes In his book Something Deeply Hidden, “quantum mechanics isn’t just an approximation to the truth; it is the truth.” And the multiverse, however seemingly preposterous, it is an inescapable consequence of quantum mechanics.
Making this case, Carroll takes us deep into the surreal quantum world. The basic quantum equation, called a wave function, shows a particle—an electron, say—inhabiting many possible positions, with different probabilities assigned to each one. Aim an instrument at the electron to determine where it is, and you’ll find it in just one place.
You might reasonably assume that the wave function is just a statistical approximation of the electron’s behavior, which can’t be more precise because electrons are tiny and our instruments crude. But that assumption, Carroll says, is wrong; the electron exists as a kind of probabilistic blur until you observe it, whereupon it “collapses,” in physics lingo, into a single position.
Physicists and philosophers have been arguing about this “measurement problem” for almost a century now. Various explanations have been proposed, but most are either implausible, making consciousness a necessary component of reality; or kludgy, requiring ad hoc tweaks of the wave function.
The only solution that makes sense to Carroll—because it preserves quantum mechanics in its purest form—was proposed in 1957 by a Princeton graduate student, Hugh Everett III. He conjectured that the electron inhabits all the positions allowed by the wave function, but in different universes.
This hypothesis, which came to be called the many-worlds theory, has been refined over the decades. It no longer entails acts of measurement, or conscious observation. The universe supposedly splits, or branches, whenever one quantum thing jostles against another, making their wave functions collapse.
This process, called “decoherence,” is happening everywhere all at once. It is happening to you right now. And now. And now. Yes, zillions of your doppelgangers are out there at this very moment, probably having more fun than you. Asked why we don’t feel ourselves splitting, Everett replied, “Do you feel the motion of the earth?”
Carroll addresses the problem of evidence, or lack thereof, in a weird, backhanded way. He cites philosopher Karl Popper, who popularized the notion that scientific theories should be precise enough to be testable, or falsifiable. Unfalsifiable theories, Popper decreed, are pseudoscientific.
Carroll insists that because quantum mechanics is falsifiable, and has in fact withstood countless tests, the many-worlds hypothesis is falsifiable too; in fact, it is “the most falsifiable theory ever invented”—even if we can never directly observe any of those many worlds. The term “many,” by the way, is a bit understated. The number of universes created since the big bang, Carroll estimates, is 2 to the power of 10 to the power of 112.
And that’s just the many-worlds multiverse. Physicists have proposed other even more speculative multiverses, which science writer Tom Siegfried touts in his book The Number of the Heavens. String theory, which posits that all the forces of nature stem from stringy thingies wriggling in nine or more dimensions, implies that our cosmos is just a hillock in a sprawling “landscape” of universes, some with radically different laws and dimensions than ours. Chaotic inflation, a supercharged version of the big bang theory, suggests that our universe is a teeny bubble in a boundless, frothy sea.
Early on, Siegfried professes neutrality on the existence of other universes, acknowledging that “nobody can say for sure” whether they exist. But he goes on to construct an almost comically partisan defense of the multiverse, declaring that “it makes much more sense for a multiverse to exist than not."
Siegfried traces resistance to the concept of other worlds back to Aristotle, who “argued with Vulcan-like assuredness” that earth is the only world. Because Aristotle was wrong about that, Siegfried implies, maybe modern multiverse skeptics are wrong too. After all, the known universe has expanded enormously since Aristotle’s era. We learned only a century ago that the Milky Way is just one of many galaxies.
The logical next step, Siegfried contends, would be for us to discover that our entire cosmos is one of many. Rebutting skeptics who call multiverse theories “unscientific” because they are untestable, Siegfried retorts that skeptics are unscientific, because they are “pre-supposing a definition of science that rules out multiverses to begin with.” He calls skeptics “deniers”—a term usually linked to doubts about very real things, like vaccines, climate change and the Holocaust.
I am not a multiverse denier, any more than I am a God denier. Science cannot resolve the existence of either God or the multiverse, making agnosticism the only sensible position. I see some value in multiverse theories. Particularly when extolled by a writer as gifted as Sean Carroll, they goad our imaginations, they give us intimations of infinity, they make us feel really, really small—in a good way.
But I’m less titallated by multiverse theories than I once was, for a couple of reasons. First, science is in a slump, and its credibility has taken a beating lately. Science is ill-served when prominent scientists tout ideas that cannot be tested and hence are, it must be said, pseudoscientific. Multiverses based on string theory and chaotic inflation, which are themselves unfalsifiable, are doubly pseudoscientific.
Moreover, at a time when our world, the real world, faces serious problems, dwelling on multiverses strikes me as escapism—akin to billionaires fantasizing about colonizing Mars. Shouldn’t scientists do something more productive with their time?
Maybe in another universe Sean Carroll and Tom Siegfried have convinced me to take multiverses seriously, but I doubt it.
Further Reading:
Is the Schrodinger Equation True?
Physicist John Wheeler and the “It from Bit”
Physicists Teleport Bullshit Through “Wormhole”!
The Big Bang Theory Is True. Deal With It
My Controversial Diatribe Against “Skeptics”
My Quantum Experiment (free online book)
I also critique multiverses, string theory, inflation and other pseudoscientific theories in The End of Science.
Self-plagiarism Alert: This is an updated, un-paywalled version of a review I wrote for The Wall Street Journal. My words yearn to be free!
Physicist Frank Tipler emailed me the following rebuttal of this column and of “Is the Schrodinger Equation True?”
John, The scientific approach is to accept as true the consequences of a well-tested theory — no matter how crazy these consequences appear to be — until an experiment shows the theory to have limited validity, or the theory is shown to be mathematically inconsistent. Given Newtonian gravity theory, one has to accept that the Earth is moving around the Sun and rotating on its axis, no matter how crazy it seems to be that so massive as the Earth could be in motion. The mathematics of quantum mechanics, in particular Schrodinger's equation, shows that quantum mechanics is necessarily a multiverse theory. Since quantum mechanics is well-tested, one must accept the multiverse of quantum mechanics. The multiverse nature of quantum mechanics has been discovered independently many times, by no fewer than three physics Nobel Prize winners. That Many-Worlds is the ONLY mathematically consistent interpretation of quantum mechanics has also been pointed out many times, for example by David Deutsch in his book THE BEGINNING OF INFINITY. As to the question of whether Schrodinger's equation was discovered or invented, it was discovered. In my 2014 PNAS paper, I derived the equation by requiring that classical mechanics be mathematically consistent. Do you have any experimental evidence that quantum mechanics is wrong? If not, then by rejecting the Multiverse of quantum mechanics, you have embraced pseudo-science! Best, Frank