Lurking behind Einstein’s theory of gravity and our modern understanding of particle physics is the deceptively simple idea of symmetry. But physicists are beginning to question whether focusing on symmetry is still as productive as it once was.I concluded that the real intended story is that the symmetries are no longer considered as fundamental as they used to be. And I think that such a statement would be correct – although this transition wasn't really taking place in 2019 but rather in the 1990s or 1980s. However, I don't think that the body of Cole's article actually contains evidence that a rational reader could consider a justification of her subtitle.
OK, her article touches many topics related to symmetries: special relativity and the Lorentz invariance, beauty of equations according to Dirac, general relativity and its vaguely suggested connection with symmetries, Emmy Noether, global symmetries vs gauge symmetries, gauge symmetries' being redundancies, spontaneously broken symmetry as a non-symmetry of solutions when the equations are symmetric, and many other topics.
But each of these topics is sketched or mentioned so superficially (and she jumps from one topic to another so quickly) that I find it inconceivable that someone could actually understand any of these insights, even partially, after having read the article. To be more precise, I haven't been persuaded that the writer actually understands any of these things herself. Like how the Lorentz symmetry acts in special relativity. Or what the spontaneous symmetry breaking does in physics.
Or what Emmy Noether is actually famous for. Cole seems to promote partly wrong statements, such as that Noether has linked the energy conservation in GR to the symmetry exchanging reference frames. Well, the relevant symmetry transformation related to the energy conservation law is a time translation, not really something that we consider "switching between reference frames". On top of that, these coordinate-changing symmetries are just redundancies (local symmetries) in GR, so there's no general [total] energy conservation law in generic spacetimes of GR! So the sentence seems to be defective at so many levels that I concluded that it can't be a bunch of coincidences. The writer must really fail to understand how it works.
Despite this big uncertainty about the understanding of anything by the writer, the writer nevertheless feels confident enough to present the far-reaching conclusions such as "the symmetry isn't as productive as it used to be". Is that statement right, a rational reader must ask? Can the communication of such feelings – and they're really feelings, not conclusions of any rational analysis – be helpful to direct readers' searching for his own understanding? I just doubt it.
Does it make sense for a youngster interested in physics to read articles about symmetry that are written by someone who doesn't actually understand any of the stuff at a level recognizable to the experts? My answer is No.
In the past, good popular writing about science was sort of analogous to textbooks that actually try to train someone so that he really understands the stuff and may become a professional. Popular books – e.g. Martin Gardner's books about relativity – were more playful, slower, using some stories, but the basic goal was the same as the goal of the textbooks.
I think it is no longer the case. Articles such as Cole's don't actually want to teach anything to anybody and they can't even persuade the experts that the writer actually understands what she is writing about. Articles such as Cole's are communicating some feelings and some predetermined, intrinsically political conclusions that the readers are expected to parrot. The reader should simply take it as a fact – because it's written by a person widely called a "science writer" – that symmetry used to be very productive but it is no longer the case. It's too bad because it has very little to do with science and the scientific method of changing collective or individual opinions about anything. The word "science" is just being stolen for something that is no longer "science".
OK, where are the places of the body that show that practitioners no longer consider symmetry productive? Here is the first one, I think:
There has been, in particle physics, this prejudice that symmetry is at the root of our description of nature.Right. I would agree with Justin Khoury. It's been a pillar of some faith, some armchair physicists still look at the things in this way, and real experts generally believe that this complete obsession with symmetries is wrong today. And Khoury has used a relatively hostile word "prejudice" for what used to be the status quo.
Well, it may have been a prejudice. But you could also call it a "lore". I think that Khoury wouldn't protest if the word "lore" had been used instead of "prejudice". It doesn't really make any difference for a physicist – but for journalists like K.C. Cole who are obsessed with feelings, the difference between "prejudice" and "lore" could be substantial. The special relativity is built from the Poincaré symmetry, GR is built from the diffeomorphism symmetry, the Standard Model may be built from the \(SU(3)\times SU(2)\times U(1)\) gauge symmetry, and so on. That was a picture of the past – a reason why physicists tended to consider the symmetry primary.
We no longer see it in this way – because symmetries may be emergent, accidental, flexible, appearing, disappearing, and gauge symmetries aren't real physical symmetries because they're redundancies that depend on the chosen description of physics – but Cole hasn't really explained why. She doesn't really explain why the gauge symmetry is just a redundancy. She doesn't explain how the descriptions with different gauge symmetries may be dual to each other, how they may be gauge-fixed or deformed to each other on the moduli space, and so on. So the reader is just expected to mindlessly copy, without any real evidence, the opinion of K.C. Cole that "symmetry is no longer as productive as it used to be" although there is no real justification of that assertion in the article. If we don't count some negatively sounding words without sentences, such as "prejudice" in someone's quote, and indeed, we shouldn't pay attention to those.
That's bad. Whether the reader understands one thing or another about symmetry has some limited importance but there is something more important at stake. For a reader to be scientifically literate, he just shouldn't accept assertions that aren't justified by any evidence. This kind of "skepticism" or "caution" is an essential prerequisite for the scientific thinking about anything. And this article is an example where the principle fails. If the reader behaves rationally, the article won't really move him by a micron. It's a useless article. A necessary condition for the article to actually move someone's ideas somewhere is that he blindly believes what he reads. And that's a deviation from the scientific discourse that is much more devastating than a misunderstanding of one technicality involving the notion of symmetry or another.
Well, there are two more segments in the article that could be claimed to be "the evidence that the importance of symmetry has dropped":
Over the past several decades, some physicists have begun to question whether focusing on symmetry is still as productive as it used to be. New particles predicted by theories based on symmetries haven’t appeared in experiments as hoped, and the Higgs boson that was detected was far too light to fit into any known symmetrical scheme. Symmetry hasn’t yet helped to explain why gravity is so weak, why the vacuum energy is so small, or why dark matter remains transparent.The only problem is that these assertions are mostly wrong. The new particles haven't shown up in experiments so far and there has never been any universally enough accepted prediction of a whole framework – as opposed to particular competing models that make lots of assumptions – that some new particles should have shown up by now. All the predictions assuming naturalness are probabilistic predictions that have never guaranteed and could never guarantee the discovery of anything. Supersymmetric particles remain the most well-motivated possible particles in new physics.
At the same time, symmetry-based reasoning predicted a slew of things that haven’t shown up in any experiments, including the “supersymmetric” particles that could have served as the cosmos’s missing dark matter and explained why gravity is so weak compared to electromagnetism and all the other forces.
Nothing has qualitatively changed. It has always been known that supersymmetry and perhaps other symmetries relating the Higgs boson to something else etc. have to be broken. And all these qualitative things remain true and promising possibilities. In particular, it's comparably likely to the probability of the 1990s that the weakness of gravity or the smallness of the cosmological constant has an explanation in which symmetries play an important role. The lightness or stability of the dark matter probably depends on some new symmetry, too. These possibilities have not been ruled out or falsified, at least not if one uses the scientific definitions of these verbs.
Symmetries still play many roles in all of that – and they unavoidably appear in newly proposed explanations of observations in physics. Supersymmetry is a symmetry, or a Grassmannian generalization of Lie algebras. Also, symmetries surely do explain why dark matter is transparent, whatever it is. Dark matter is dark because it doesn't interact with the electromagnetic field and it doesn't interact with the electromagnetic field because its pieces are electrically neutral – i.e. invariant under the electromagnetic \(U(1)\) symmetry transformations! K.C. Cole is basically saying that the notion of symmetry is being expelled from the reasoning about all these questions but it's obviously complete nonsense. It will never be expelled because these are settled connections and explanations and the symmetry will never lose its role in those explanations. The only thing that is happening is that there may be a deeper explanation of these known things where the symmetries aren't among the most fundamental concepts.
The statement that "symmetries don't explain why dark matter is transparent" is either wrong or vacuous and no real expert would make such a statement. (I just picked an example but the same criticism applies to many other propositions in Cole's article.) But in the genre such as K.C. Cole's article, it's just fine to write such wrong statements because the political spirit is consistent with the main message she wants to convey. She wants to convey the view that symmetry has deteriorated in recent years or decades – which is really a feeling, not a fact – and she thinks that given this goal, anything "negative" may be or should be written about symmetries. Whether the statements are actually correct doesn't have to be verified.
So she isn't really teaching any physics – the primary reason is that she probably doesn't understand any. But even if I remain slightly uncertain about this proposition, there are just way too many hints in the article that it's a material written by and for "humanities" types, for people interested in feelings, grievances, entitlements, and identity politics, not for the "natural science" types who care about equations, experiments, mathematical proofs, and facts.
What are the signs that this belongs to the "humanities" genre? One of the traits that are innocent but they drive me up the wall is the permanent attribution of some elementary statements to physicists. So she has communicated with five main physicists: Stephon Alexander, Robbert Dijkgraaf, Mark Trodden, Justin Khoury, and David Kaiser (a part-time historian). Sorry if I overlooked someone.
In her article, you find 4 quotes of the type "Alexander said this or that". "Trodden said this or that" about 5 times, "Dijkgraaf said this or that" 4 times, "Khoury said something" 3 times, and "Kaiser said something" 6 times. That's 22 similar quotes in total. You know, people may have different opinions but most of science just isn't about some idiosyncratic opinions. Physics is an objective natural science. And most of the stuff she talks about really is some physics that has been settled for 50 years – and in very many cases, over 100 years.
Most of the 22 quotes end up being similar to
“If that weren’t the case [the Cosmos is uniform at cosmological scales, a manifestation of a symmetry], cosmology would be a big mess,” Khoury said.Do you understand why I am angry about that? It just doesn't matter at all that it was Khoury who said it. Every competent cosmologist could say – and has said – a sentence that is nearly equivalent. If the Universe were inhomogeneous at the cosmological scales, we couldn't design neat FRW Ansätze for the cosmological evolution and we would have to study "where we exactly live" because the phenomena we observe around the Solar System would heavily depend on our special place in the Universe. Are we close to some "center of the Universe" or far from it? Those things would matter. But there's no real "center of the real Universe" where we live so cosmology may avoid these questions and the research of cosmology is cleaner. We may study the whole Universe by observations made from the Earth and we may extrapolate most of the conclusions to the whole Universe, too. Thank God.
Khoury knows it. But I assure you that Dijkgraaf, Alexander, Trodden, your humble correspondent, maybe Kaiser, and everyone else who got a well-deserved good grade in a cosmology graduate course knows these things, too. The first problem with the attribution is that lots of laymen who read Cole's article will conclude e.g. that Justin Khoury is the guy who discovered that the Universe was uniform, or that the uniformity was important, or that it was related to symmetries. Just to be sure, he didn't discover either. To make things worse, I haven't even been persuaded that Cole herself understands that Khoury didn't discover either!
But there's a more general problem resulting from the attribution. It's about the spirit of science.
You know, technically, it may be right that Khoury said this or that, Trodden said this or that, Dijkgraaf said this or that, and Alexander said this or that. But by making these assertions that are attributed to somebody, K.C. Cole implicitly also says something else, namely that it matters who said it. But this implicit assertion is completely incorrect. In science, it doesn't matter who made one proposition or another. In physics, black lives don't matter and white lives don't matter, either. Also, men don't matter. Let alone women. Natural science isn't about humans or personal opinions. It's about objective evidence that is accessible to everybody with a sufficient intelligence, integrity, attention, background, and patience. It's just not true that everything is personal. The number of correct theories of relativity or the correct interpretations of quantum mechanics is fewer than 26, the number of genders. The only thing that is equal to the number of genders is the spacetime dimension of bosonic string theory. ;-) Even the number of genders is really lower than those people assume but I don't want to make my text controversial by suggesting that there exist men and women! ;-)
So she doesn't really explain any of the points about the importance of symmetries – or the decline of that importance – at least not quite correctly. But she does explain something that surely affects many readers. And the influence is harmful. She conveys the totally wrong lesson that it matters who made a proposition in physics. She is helping to brainwash the readers into thinking – or failing to think – in analogy with the brain-insufficient practitioners of the humanities. People who want to mindlessly parrot and who are just choosing their allies in an ad hominem way, to share the grievances with them. People who don't give a damn about evidence, logical arguments, equations, or observations. At most, they say that they care about the evidence etc., because it "sounds nice", but they're lying because in practice, they are using something completely different to decide what they should root for etc.
That's why I think that the net effect of articles such as this K.C. Cole's text is negative and because K.C. Cole's article is still one of the best popular texts about physics that are appearing in (almost) mass media these days, it seems obvious that the net contribution of the science writers as an occupation to mankind's scientific literacy is unquestionably negative. They're really helping mankind to evolve towards Idiocracy. Maybe some other journalists are even more harmful but that doesn't imply that the current science journalists have a positive sign.
You might suggest that there's a simple "legitimate" explanation why she attributes mostly elementary statements to the 5 physicists 22 times. She isn't a real authority. So it's right for her to "report what the authorities say" which is why the statements are more authoritative once the physicists endorsing them are named. But if that's so, I would like to know the name of the physicist who has recommended the far-reaching and controversial summary in the subtitle, or any of the wrong statements such as "symmetry hasn't helped to explain why dark matter is transparent". It seems she is making the text look more authoritative by attributing some (sensible) statements to physicists, but the most important statements are wrong, unattributed, and the reader is supposed to overlook it.
This mess is unavoidable in the "humanities" type of science journalism. You know, if one writes good popular science, one doesn't need to refer to the authorities. It's just good, the smart readers see it, and some experts who read the popular stuff will see it, too. Martin Gardner – to continue with an example I mentioned above – was primarily keen on recreational mathematics. He was no professional physics researcher, ever. But he just understood special relativity well. He wrote popular books about it where he didn't need to refer to "authoritative" sources because the real authority came from the arguments that made sense because he actually understood the stuff.
These days, journalists and popular writers generally understand nothing and their writing doesn't make much sense beyond the universal templates that they have learned in their journalism courses which is why they have to build on obnoxious appeals to authorities and why their texts unavoidably end up being misleading political tirades. Many of them openly disagree with the thesis that science is about the evidence, about the arguments' making sense, not about authorities (many people claiming to be science journalists are even willing to support insane clichés about the formidable 97% consensus and similar things). That's a simple way to see that the ideas and especially the methodologies they are trying to spread have very little to do with science. They're mostly abusing the word because it has earned quite some capital and they find it useful to be parasites on the good name of science. But the capital wasn't earned by these journalists or their type of "work" at all.