They Wanted an Accidental Universe, Not a Beautiful One

An article in the New York Times discusses the failure of attempts to find evidence for the physics theory called supersymmetry:

“These are difficult times for the theorists,” Gian Giudice, the head of CERN’s theory department, said. “Our hopes seem to have been shattered. We have not found what we wanted.” What the world’s physicists have wanted for almost 30 years is any sign of phenomena called supersymmetry, which has hovered just out of reach like a golden apple, a promise of a hidden mathematical beauty at the core of reality.

Physicist Sabine Hossenfelder (who blogs at the Backreaction blog) has written a recently published book entitled Lost in Math: How Beauty Leads Physics Astray. In the book she pushes the same claim she has advanced on her blog, that physicists have gone astray because they've been so interested in pushing theories describing some undiscovered underlying beauty in nature. The short summary of the book at the site offering it for sale includes this statement: “The belief in beauty has become so dogmatic that it now conflicts with scientific objectivity: observation has been unable to confirm mindboggling theories, like supersymmetry or grand unification, invented by physicists based on aesthetic criteria.” You can read an excerpt from the book here. In that excerpt she states “Lost in Math is the story of how aesthetic judgment drives contemporary research.” She quotes a physicist to back up this claim:

“We cannot give exact mathematical rules that define if a theory is attractive or not,” says Gian Francesco Giudice. “However, it is surprising how the beauty and elegance of a theory are universally recognized by people from different cultures. When I tell you, ‘Look, I have a new paper and my theory is beautiful,’ I don’t have to tell you the details of my theory; you will get why I’m excited. Right?” ….“Most of the time it’s a gut feeling,” he says, “nothing that you can measure in mathematical terms: it is what one calls physical intuition. There is an important difference between how physicists and mathematicians see beauty. It’s the right combination between explaining empirical facts and using fundamental principles that makes a physical theory successful and beautiful.”

But though this particular quote might seem to back up her thesis, Hossenfelder's “quest for beauty” thesis seems to be a dubious one in the sense that it does not accurately describe why physicists spent so much time on unsuccessful efforts such as the theory of supersymmetry. I think the real story is: they wanted an accidental universe, not a beautiful one. 

You can get a better feel for the motivation for a theory such as supersymmetry by reading a recent glum essay at the Aeon site, one entitled “Going nowhere fast.” The essay states the following:

Behind the question of mass, an even bigger and uglier problem was lurking in the background of the Standard Model: why is the Higgs boson so light? In experiments it weighed in at 125 times the mass of a proton. But calculations using the theory implied that it should be much bigger – roughly ten million billion times bigger, in fact....Quantum fluctuations of ultra-heavy particle pairs should have a profound effect on the Higgs boson, whose mass is very sensitive to them....One logical option is that nature has chosen the initial value of the Higgs boson mass to precisely offset these quantum fluctuations, to an accuracy of one in 10¹⁶. However, that possibility seems remote at best, because the initial value and the quantum fluctuation have nothing to do with each other. It would be akin to dropping a sharp pencil onto a table and having it land exactly upright, balanced on its point. In physics terms, the configuration of the pencil is unnatural or fine-tuned. Just as the movement of air or tiny vibrations should make the pencil fall over, the mass of the Higgs shouldn’t be so perfectly calibrated that it has the ability to cancel out quantum fluctuations. However, instead of an uncanny correspondence, maybe the naturalness problem with the Higgs boson could be explained away by a new, more foundational theory: supersymmetry.

This illuminating excerpt gives you the real scoop on supersymmetry. It was a theory designed to “explain away” a case of fine-tuning in nature, something that seemed as precise as a pencil balancing on its tip. Why would someone want to explain away such fine-tuning? It wouldn't be because they wanted to make things “more beautiful,” for by removing such an elegant case of fine-tuning it would be like robbing nature of something impressive and beautiful. But people might wish to get rid of such a case of fine-tuning if they wanted the universe to seem more accidental, and less like some product of deliberate purpose.

The motivation of wanting to make the universe seem more accidental is something that can be called an ideological preference. Hossenfelder's book would have a more accurate subtitle if its subtitle was “How Ideological Preferences Lead Physics Astray” rather than “How Beauty Leads Physics Astray.” The same ideological preferences have led countless physicists and cosmologists to write thousands of speculative papers writing about inflation theories designed to explain away fine-tuning at the universe's very beginning, fine-tuning that seems more precise than that involving the Higgs boson.

None of these attempts to explain away fine-tuning in nature has been empirically substantiated by confirming evidence. Another problem is that such theories do not actually reduce the amount of fine-tuning in nature – they merely “rob Peter to pay Paul” by reducing fine-tuning in one place at the cost of adding lots of fine-tuning in other places. For example, supersymmetry postulates lots of “superpartner” particles that happen to have masses and charges exactly the same as known particles, but if such coincidences happened in nature, each such coincidence would be an additional case of fine-tuning. Similarly, the "cosmic inflation" theories of exponential expansion in the universe's first second get rid of some cases of fine-tuning, but require just as much or more fine-tuning in the form of lots of postulated parameters that have to be fine-tuned. 

Another problem with any such attempt is that it will merely address one case of fine-tuning, when there is fine-tuning all over the place in both physics and biology. As the previously cited Aeon piece tells us:

Perhaps the bleakest sign of a flaw in present approaches to particle physics is that the naturalness problem isn’t confined to the Higgs boson. Calculations tell us that the energy of empty space (inferred from cosmological measurements to be tiny) should be huge. This would make the outer reaches of the universe decelerate away from us, when in fact observations of certain distant supernovae suggest that the outer reaches of our universe are accelerating. Supersymmetry doesn’t fix this conflict.

The writer fails to mention that this “huge” energy of empty space should also be sufficient to prevent our very existence, so we have in this matter one of the many “why are things so well-arranged so that we can exist” issues. There are countless other such fine-tuning issues in physics, as well as countless cases of fine-tuning in biology that are poorly explained by existing theories.

We may therefore compare the supersymmetry theorist to a person underneath a UFO swarm above him, who tries unsuccessfully to explain one UFO in the sky as being a swarm of bees that happened to have a disk shape, while failing to mention forty other UFO's in the same sky, some larger than the ones he tried to explain.

The author of the Aeon essay notes the effort he has put into chasing the "superpartners" of supersymmetry theory. He states:

For the first 20 years of my scientific career, I cut my teeth on figuring out ways to detect the presence of superpartners in LHC data. Now I’ve all but dropped it as a research topic.

Since undiscovered physics might take any of 1,000,000,000,000 different configurations, the scientist who assumes that the one unobserved configuration he dreamed up is actually going to appear is rather like some interstellar astronaut who makes a drawing of an extraterrestrial life form that he might see on a planet, and who then expects to see exactly that life form in front of him when he opens up the door of his landing craft.