Fine-Tuning Denialism Can Lead to Largely Wasted Careers in Science

It seems that throughout his career, cosmologist Ethan Siegel has been the epitome of an "old guard" scientist -- someone dedicated to defending old speculative theories of physicists and cosmologists, mostly theories that have never been well-supported by observations. Year after year, Siegel keeps making the case for theories that somehow got popular among little cliques of physicists or cosmologists, but which never got any good evidence in their favor: theories such as supersymmetry (SUSY), primordial cosmic inflation, and dark matter. Don't be fooled by the hype of the latest "dark matter map" claim, discussed here; we still have the situation that no one has seen dark matter. 

Reading Siegel's posts is rather like reading some old monk argue for the old dogmas of some old organized religion, very much a kind of "you must keep believing as they taught me in college four decades ago" affair. A 2024 post by Siegel tries to explain why scientists have not given up on a theory they spent decades on, but which was never supported by any observations: the theory of supersymmetry (SUSY). For quite a few years around 2010, physicists were publishing about 1500 papers per year on this theory. 

The post by Siegel begins with a silly-sounding statement: "One of the greatest ideas in all of physics, regardless of whether it turns out to be a true idea that reflects reality or not, is that of supersymmetry, or SUSY for short." How unwise to think that a theory is "one of the greatest ideas in all of physics" regardless of whether such an idea is true or false. 

Although having a title of "The one reason that physicists won’t give up on supersymmetry," Siegel's post fails to explain what that reason is, in any way that the average reader will be able to follow.  I can explain more clearly the real reason why some physicists have not given up on the theory of supersymmetry, despite the lack of any evidence for it: it is that such a theory serves as an atheist analgesic pill, helping slightly to relieve the pain that atheist physicists feel when encountering the enormous fine-tuning within the universe's physics and biology. 

The supersymmetry theory arose as a speculative attempt to explain away (or kind of sweep under the rug) a case of cosmic fine-tuning that bothered scientists. The issue of the fine-tuning of the Higgs mass (the mass of the Higgs boson) was skillfully explained by physicist Ben Allanach in an  article at the Aeon site: 

"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."

In an article in Symmetry magazine, we have a similar explanation:

"To understand what’s fishy about the observable Higgs mass being so low, first you must know that it is actually the sum of two inputs: the bare Higgs mass (which we don’t know) plus contributions from all the other Standard Model particles, contributions collectively known as 'quantum corrections.' The second number in the equation is an enormous negative, coming in around minus 10¹⁸ GeV. Compared to that, the result of the equation, 125 GeV, is extremely small, close to zero. That means the first number, the bare Higgs mass, must be almost the opposite, to so nearly cancel it out. To some physicists, this is an unacceptably strange coincidence."

How big a coincidence? The Symmetry article later quotes physicist Lawrence Lee Jr. as saying “the conundrum with the Higgs mass, which would require fine-tuning on the order of 1-in-10³⁴,” which is a coincidence like the coincidence of you correctly guessing the full phone numbers of three consecutive strangers. 

Scientists should have just accepted this case of very precise fine-tuning in nature.  But instead, many of them made a long, quixotic, futile attempt to overthrow it (like someone trying to overthrow the observation that the sun is hot, with some elaborate theory trying to explain how the sun isn't really hot).  Why did they do that? Because they had a motivation, an ideological motivation rather than the motivation of simply discovering truth. Their ideological motivation was related to a belief that the universe should not be anything that looked like a product of design. This ideological motivation is clearly stated in a Symmetry article by physicist Lee, who states it as follows: “In general, what we want from our theories—and in some way, our universe—is that nothing seems too contrived.” If you want for the universe to not "seem too contrived," then you may twist yourself into knots trying to explain away cases of apparent fine-tuning in the universe. 

An article makes it rather clear that the supersymmetry theory was mainly motivated by a desire to get rid of a case of fine-tuning, and make the universe look like it was a little less lucky, a little less  providentially blessed. We read this:

"For example, the small mass of the Higgs boson is notoriously difficult to explain—its calculation requires subtracting two very large numbers that just happen to be slightly different from each other. 'But if you add supersymmetry, this takes care of all these cancellations such that you can get a light Higgs mass without needing to have such luck,' says Elodie Resseguie, a postdoc at the US Department of Energy’s Lawrence Berkeley National Laboratory."

The small mass of the Higgs boson is one of only very many cases of fine-tuning in nature.  There are many very precise examples of fine-tuning needed for our universe to be habitable, such as the very precise matching of the absolute value of the proton charge and the electron charge needed for planets and stars to be able to hold together (explained by the astronomer Greenstein here).  There are many times more cases of fine-tuning in biology, such as the endless thousands or millions of different types of very precisely fine-tuned protein molecules, with functional thresholds so high they cannot be credibly explained by Darwinian evolution.  A functional threshold is a particular amount of arrangement of parts that must exist for something to have any functional value.  With protein molecules, the functional threshold is typically so high it involves thousands of very well-arranged atoms. 

The visual below depicts a scientist who clings to some old, failing theory trying to explain some of this fine-tuning:  

The old theory serves as an atheist analgesic, helping slightly to relieve the irritation the scientist feels when encountering the endless examples of fine-tuning in nature:

Below is an interesting graph I got after using the Google Ngram viewer to search for references in Google Books for the terms "supersymmetry" and "fine-tuning."  We see that supersymmetry theory had its peak around 1980, and has been in decline since then. But we have ever-more references to fine-tuning, very many of them references to fine-tuning in physics and biology.  It seems that the efforts of scientists to sweep under the rug fine-tuning are not succeeding. 
 

Siegel's 2024 post that I discussed above is entitled "The one reason that physicists won’t give up on supersymmetry." But a recent article in Quanta Magazine does not tell any such "sticking to their creed" story. That article instead rather has a kind of "hubris has been humbled" ring to it, with kind of a "they're fumbling around and losing their confidence" sound to it. The article is entitled "Is Particle Physics Dead, Dying, or Just Hard?" We have a quote from one guy saying, "I think that it’s kind of irrelevant what we plan on a 10-year timescale, because if we’re building a collider in 10 years, AI will be building the collider; humans won’t be building it." Anyone familiar with how utterly enormous is the physical work involved in the building of a giant particle collider may realize how inane this statement is.