Bad Physics takes
Physics is not in a rut – but people writing about physics might be
I spend too much time reading opinions on Medium. In particular, I spend too much time reading bad opinions on Medium. I cannot say I mind it exactly. In fact, I really do enjoy hate-reading other writer’s insipid takes on the topic de jour. The armchairs are often too deep for many writers to notice the limitations of their offered analyses.
However, I was triggered the other day by a particular piece about physics being “stuck.”
The gist of the post is clear: modern physics is “stuck in a rut”. We really seem to have just stopped making big discoveries. The great recent observations, e.g. discovery of gravitational waves, measuring the mass of the Higgs boson, were all predicted half a century ago, and no real breakthroughs have happened since then. Apparently, all of us working in physics are just bad at our jobs.
That last sentence is mostly mine. The piece itself actually is fairly genteel, though the latter two of the three reasons I do take a little exception to. In any event, the author clearly does think there is something wrong with physics as a field.
It is not a particularly unique take. Versions of this story have been discussed publicly in all sorts of publications beyond Medium, and since social media has turned us all into publishers, copies of these discussions have metastasized in the last decade. The result of which is that these hot physics takes have been consistently annoying me to the point where the author’s piece had me audibly lecturing the app on my phone.
So, this post is partly for my own catharsis, but I hope I can convince you why this is not a good representation of physics as a field, and that the perspective is actually a myopic view of how science progresses.
A brief tour of modern physics
I feel there is some background needed to help understand how this hot take of physics has come to be so popularly discussed. To write ‘modern physics’ is to encompass a lot more than I think most readers are realizing. To see that it helps to know how physics is organized.
You have probably heard that modern physics is built on two fundamental theories: Einstein’s general relativity, and quantum mechanics (also by Einstein). This is somewhat true, but as an aside I personally never liked it. One might take the statement to imply that classical physics (mechanics and electrodynamics more specifically) is bad somehow, which, I cannot emphasize enough, is not the case. Also I think to sum up modern physics in terms of two prominent theories obscures important classical physics developments that were made in the last century, like deterministic chaos. And mostly I feel it just does not tell you much about physics itself. We are scientists studying a natural science after all, and we study real natural phenomena, not just mathematical theories.
In any event, physicists do not organize themselves either in camp quantum or camp relatively. Like any other discipline we are grouped by what we study.
Take a look at this chart. It is an infographic from the American Institute of Physics. If you have not heard of them, they are mostly known as the publishers of some prominent journals, e.g. Applied Physics Letters, Journal of Chemical Physics, but also of the popular Physics Today magazine. But they also regularly gather data on physics PhDs granted each year. This chart shows the breakdown of physics PhDs awarded by field of study, for 2010 and 2011 combined.
There are some names that might be unfamiliar: “Condensed matter” is modern term for what used to be called “solid-state physics,” which may not be any more illuminating, but it refers to physics of hard (hence, ‘solid-state’) stuff, like metals and semiconductors. You might ask if that is similar to “materials science?” Yes, it is, but the latter term is more favored by the engineers working on these topics, so we need to call it something different for the sake of the poor college deans.
Other names might seem weird and redundant: is “optics” really different from “photonics”? (Sort of yes), and isn’t “nuclear” part of “atomic” physics? (Yes and no). And what exactly falls under “applied physics”?
So the names are arbitrary, and the categories are not always well defined. It is very common for physicists to span at least a few of these. But the point I want to make is the relative prominence of the number of PhDs awarded in particle physics (sometimes called high-energy physics) compared to physics as a whole. It’s only one subcategory of the whole of physics, and not even the largest one.
The “rut”
How is this relevant to the rut that modern physics is currently in? Because this is the field that is implicitly invoked when people discuss the crisis or rut in physics. And here is where there is grain of truth to the idea.
When you hear the title “standard model” they are referring to the modern theory of particle physics. Roughly speaking, the Standard Model is a theoretical model where all the particles that we know to exist that interact according to the rules of quantum mechanics and special relativity. The main elements of theory were finalized in the ’70s and it since then proved to be incredibly successful, most especially in describing the electromagnetic interactions. The Higgs boson in 2012 was the big deal it was, because it was the “last piece” missing. As of now there are no experimental results that contradict the Standard Model, which would point to new physics, and at least for three of the four fundamental forces, it looks like the Standard Model is “complete.”
Despite its success it is a common opinion that the Standard Model can’t be the final word. It is just too “ugly”, usually in reference to the many free parameters that must be set by experiment. There should be a deeper theory than sets the value of most of these parameters based on deeper principals. Moreover, the model does not include gravity. Whether or not it should is more of an aesthetic point than a scientific one, but still a lot physicists think that there should be a deeper theory that treats gravity on the same footing as the other three forces.
Theories that do this are the “theories of everything” that are very popular topics of discussion these days in the blogosphere. But so far, all of them are only mathematical speculations. Still, the lack of a quantum theory of gravity is certainly the most famous problem in modern physics.
Forgetting the rest of physics
Because it deals with the fundamental interactions, particle physics does have a privileged position in the discipline, at least in the minds of science writers but even for many physicists. This I think leads to the myopia I mentioned above: particle is thought of as the real physics, whereas the rest of us (i.e. the majority of physicists) are just applied, and any progress made is just better application.
I got a few things to say about that sentiment.
First about the gravity problem: the quest to develop a quantum theory of gravity is no doubt riddled with a lot of failure (so far). There is a lot of popular science content around the quest to find one. Keep in mind however that so far, all the efforts have been purely theoretical guesses on what the theory might be. As a force, gravity is so -damn- weak that, until recently (refs), it has been near impossible to measure gravity anywhere close to a quantum scale. Without data to explain, there is little to guide theory, and I do not think we should be too surprised that a lot of the guesses end up being wrong.
Moreover, it is far from the case that particle physicists, at least on the experimental side, have no idea what to do next. The LHC is getting an upgrade, and there are yet more active experiments in areas like dark matter detection, observations of the cosmic microwave background. Where there is controversy is on the topic of building bigger and, yet, more expensive particle colliders. Not being a particle physicist, I do not have much to say whether to spend twenty billion dollars on a bigger LHC is worth the investment. But given how good governments are at wasting money (see any national news right now), I would submit that it is not the worst thing to blow tens of billions on.
Secondly, about the other fields being “applied”. Apart from being a snobbish perspective and generalization of the other domains, not to mention chemistry and biology, it is not true that you cannot fundamentally work in domains. Most of the action in quantum physics happening right now is taking place in optics laboratories with experiments that fit on table tops, not at particle accelerators, including experiments that are specifically looking for the effects of forces outside of the standard model.
Also, there is the phenomenon of “emergence,” where interactions among many smaller things leads to a collective behavior that cannot be predicted from the properties of the things themselves. For instance, you cannot infer fluid properties of water from a single H2O molecule. In the same way the states of many particle quantum systems (condensed matter physicists study this), cannot be understood with a better theory of the four fundamental forces. This point was argued much more completely by the physicist P. W. Anderson in 1972 as “more is different.” The tools you need to study emergent properties are not the same as the properties of the components, and studying them can require fundamentally different approaches.
The media factor
I am not the first to get annoyed by the doom-saying of physics. A blogpost on Forbes by Chad Orzel made much of the same points back in 2019.
One thing I appreciate about his take is how much of this is driven by people trying to sell books. The most recent is Lost in Math by Sabine Hossenfelder, but there are others, e.g. Not Even Wrong by Peter Woit, and Lee Smolin’s the Trouble with Physics.
To be clear: I got nothing against scientists or their books. As physicists they are way more accomplished than I will ever be. Each of them when asked has been pretty clear that when they are talking about the “crisis” they are talking about theoretical physics of things like the Standard Model and string theory, not condensed matter or any other physics field.
But in appearances on various podcasts and TV shows and speaking about the trouble with physics they invariably just say physics, instead of theoretical particle physics. Imprecise language, combined with the great pedigree of the authors, I think leads to an impression that if all these heavy hitters are saying physics is in crisis, it must mean that the whole thing must be in crisis.
As another aside, if you do consume a lot of physics popular media, be aware that most of the talking physics heads are going to be theorists. Sean Carroll, Lawrence Krauss, Michio Kaku, Brian Greene, Roger Penrose, Leonard Susskind, the late Stephen Hawking, all theorists, all cosmologists, string theorists, or do theory about foundations of quantum physics. All extremely smart scientists, but, just like anyone, their interests are going to be biased to what they know. The only exception I know of is Brian Keating from UCSD (who I briefly met once when I was deciding what grad school to go to), but even his podcast is highly focused on topics close to his kind of experimental cosmology.
Why do theorists tend to become the popularizers of physics? I cannot say I know. But it does lead me to wonder that when theorists get more senior in their careers, they just have more time on their hands. Maybe because they do not have to manage laboratories? Or have to actually put their theories to test in an experimental setting?
Misunderstanding scientific progress
The last thing I think contributes to this false impression of a crisis is a misunderstanding of how science progresses. There is no one source to this. Futurists imagining a singularity occurring because of the feedback between new technology applied to make new discoveries (forgetting the discoveries also get much harder to make) play some part in this. But you could also say that movies like Back to the Future 2 which imagined flying cars and hover-boards all over the place by 2015, or Terminator 2 with a self-aware AI destroying the world in 1997. We are well past both those dates and none of those technologies are especially close to being reality.
If I had to pick something most responsible, it would be the incomplete story that is told about the development of quantum mechanics. This is partially related to the abundance of theorists who are popular physics talkers, but even a humble experimentalist will mostly just know the theoretical history, with only a few famous experiments known. Because that is what we learn in a university class: theory. Experimental courses do exist, but they are very expensive for a university to run, so a typical degree program will only have a few on offer. All the rest will be pure theory.
Thus, when studying quantum mechanics we tend to start with the theoretical insights by Plank and Einstein, then move on to Pauli, Schrodinger, Heisenberg, and Dirac, and then maybe you’ll get to Feynman, Schwinger, and Tomonoga. But even with all that, you probably will not hear much about what experiments were motivating the theoretical developments, let alone the physicists who conducted them.
There is a refrain for this phenomena, sometimes uttered in physics departments, that goes “Experimentalists do all the work. Theorists get all the credit.” It is a joke, but like most good jokes there is a grain of truth.
Why do I think the lack of popular attention to historical experiments leads to general misunderstanding of scientific progress? Because inevitably it leads to a focus only on the big “eureka” moments in the vein of Einstein’s quantization of light, or inventing the concept of spacetime. These eureka moments however, only come after a lot of “boring” incremental work, which is how most scientific progress happens. What do I mean by that? Well, you might like learning about quantum physics, but how much do you like learning about diffraction gratings, or laser gain mediums, piezoelectronics? No shame if you are not that interested. All three of those topics can be very dense, and not always very interesting, but they are all critical technical foundations that enable modern experiments in quantum mechanics.
A little knowledge…
A little knowledge is a dangerous thing, but only if you forget that there’s a lot you don’t know, and that’s also a lot you don’t know that you don’t know. I think on balance it is a positive thing that books by Smolin, Woit, and Hossenfelder have all this popular attention. Ditto that physicists like Krauss and Greene having the huge public profiles that they do. The content they put out is generally of excellent quality. Hossenfelder’s YouTube channel is one of the best popular physics channels on the site, and is growing. Certainly there are some who have entered the field that otherwise wouldn’t have. Even if that number is vanishingly few, that is still an achievement worth the effort.
My hope is that the rest of physics can share some of the love. Not to mention chemistry, electrical and mechanical engineering, and biology which, at the scale of atoms, really are the same thing as physics. More awareness of the public of what we actually, theorists and experimentalists, do can only go for us, especially since nearly all of funding is from the taxpayer, which currently is very limited, and the lack of funding is a primary reason that many promising projects get dropped.
But I also think the public at large would really find the topics outside of the particle realm really interesting, e.g. unconventional superconductivity, PT — optics, or meta-materials to pick a few from areas I have worked around. Quantum computing is all the rage, but a lot of the physics interest is using them less as a computer and more as an emulator. In other words, physicists want to use quantum mechanics to simulate quantum mechanics. I do not know how anyone can not be interested in that.
If you’re not, fair enough. At least now you know about it, and thanks for enduring this rant.
