A Rare Physics Op-Ed

The Guardian Newspaper has a rare opinion-editorial article about the value of certain kinds of theoretical and phenomenological physics research headlined:

No one in physics dares say so, but the race to invent new particles is pointless: In private, many physicists admit they do not believe the particles they are paid to search for exist – they do it because their colleagues are doing it. 

It was written by Sabine Hossenfelder who, as usual, is spot on in challenging the practice she describes not as entirely invalid, but as having minimal value. It begins playfully:

Imagine you go to a zoology conference. The first speaker talks about her 3D model of a 12-legged purple spider that lives in the Arctic. There’s no evidence it exists, she admits, but it’s a testable hypothesis, and she argues that a mission should be sent off to search the Arctic for spiders.

The second speaker has a model for a flying earthworm, but it flies only in caves. There’s no evidence for that either, but he petitions to search the world’s caves. The third one has a model for octopuses on Mars. It’s testable, he stresses.

She continues:

Almost every particle physics conference has sessions just like this, except they do it with more maths. It has become common among physicists to invent new particles for which there is no evidence, publish papers about them, write more papers about these particles’ properties, and demand the hypothesis be experimentally tested. Many of these tests have actually been done, and more are being commissioned as we speak. It is wasting time and money.

Since the 1980s, physicists have invented an entire particle zoo, whose inhabitants carry names like preons, sfermions, dyons, magnetic monopoles, simps, wimps, wimpzillas, axions, flaxions, erebons, accelerons, cornucopions, giant magnons, maximons, macros, wisps, fips, branons, skyrmions, chameleons, cuscutons, planckons and sterile neutrinos, to mention just a few. We even had a (luckily short-lived) fad of “unparticles”.

All experiments looking for those particles have come back empty-handed, in particular those that have looked for particles that make up dark matter, a type of matter that supposedly fills the universe and makes itself noticeable by its gravitational pull. However, we do not know that dark matter is indeed made of particles; and even if it is, to explain astrophysical observations one does not need to know details of the particles’ behaviour. The Large Hadron Collider (LHC) hasn’t seen any of those particles either, even though, before its launch, many theoretical physicists were confident it would see at least a few.

Talk to particle physicists in private, and many of them will admit they do not actually believe those particles exist. . . .  

[T]he biggest contributor to this trend is a misunderstanding of Karl Popper’s philosophy of science, which, to make a long story short, demands that a good scientific idea has to be falsifiable. Particle physicists seem to have misconstrued this to mean that any falsifiable idea is also good science.

In the past, predictions for new particles were correct only when adding them solved a problem with the existing theories. For example, the currently accepted theory of elementary particles – the Standard Model – doesn’t require new particles; it works just fine the way it is. The Higgs boson, on the other hand, was required to solve a problem. The antiparticles that Paul Dirac predicted were likewise necessary to solve a problem, and so were the neutrinos that were predicted by Wolfgang Pauli. The modern new particles don’t solve any problems.

In some cases, the new particles’ task is to make a theory more aesthetically appealing, but in many cases their purpose is to fit statistical anomalies. Each time an anomaly is reported, particle physicists will quickly write hundreds of papers about how new particles allegedly explain the observation. . . . 

Ambulance-chasing is a good strategy to further one’s career in particle physics. . . . since ambulance-chasers cite each other’s papers, they can each rack up hundreds of citations quickly. But it’s a bad strategy for scientific progress. . . .  

I believe there are breakthroughs waiting to be made in the foundations of physics; the world needs technological advances more than ever before, and now is not the time to idle around inventing particles, arguing that even a blind chicken sometimes finds a grain. As a former particle physicist, it saddens me to see that the field has become a factory for useless academic papers.

Also, note that criticism of physics scholarship really has two parts: 

(1) particles "to make a theory more aesthetically appealing", which aren't actually needed (like axions, see-saw mechanism neutrinos, supersymmetric particles and extra Higgs bosons), and 

(2) particles to explain statistical anomalies (often from one or two recent experiments) which have not adequately exhausted explanations that don't require new physics (like the X17 particle, leptoquarks to explain lepton universality violations in semi-leptonic B meson decays, sterile neutrinos, and new particles proposed to explain a W boson mass measurement out of step with other recent W boson mass measurements).

But, both are out of hand and a waste of time and money that would be better spent focusing on more well motivated proposals.

The author further discusses the Op-Ed at her blog.