(I'm not a theoretical physicist).
20 years ago, I read "The Elegant Universe" by Brian Greene, as an introduction to string theory. I was initially impressed by the brilliance of the theories it presented. What really threw me for a loop, though, was realizing (as far as I understood or remember) that string theory isn't one neatly packaged theory. Instead, it's this colossal family of theories, with so many parameters that it's hard to make predictions, and to justify "why this one and not the other ones?".
Then, over the last 20 years, I read the 3 following books, which confirmed my initial impression.
- "Not Even Wrong" by Peter Woit, a deep-dive critique of string theory for the mathematically inclined. Woit's basically saying, "If we can't test it, can we even call it science?"
- "The Trouble With Physics" by Lee Smolin, which zooms out a bit. Smolin's beef with string theory isn't just about the science; it's about how this obsession is hogging resources and blocking other potentially groundbreaking ideas (including, but not limited to, his own). Think of it as a mix of a science critique and an insider's look at the politics and sociology of physics.
- "Lost in Math" by Sabine Hossenfelder, which asks if physicists' quest for beauty in equations and theories is leading them astray. This one's the most accessible, mixing in history, interviews, personal stories, and a bit of philosophy.
All three books are good, so if you have to chose one:
- Woit's book is for the math geeks.
- Smolin's is for those who like a side of sociology with their science.
- Hossenfelder's is for folks intrigued by the blend of science, philosophy, and human bias.
Also worthwhile, IMHO, is Sabine's most recent take on string theory, as a youtube video: http://backreaction.blogspot.com/2024/03/whatever-happened-t... / https://www.youtube.com/watch?v=eRzQDyw5C3M
Keep in mind that a string theorist would probably just flip all of this on its head by pointing at the total lack of progress from their detractors.
That's entirely true, but the problem is ST gobbled up a large share of resources and personnel in theoretical physics for decades. Smolin in particular is arguing that other ideas should get a fair shake.
Disclaimer: I’m a total outsider, not in physics or even academia, so what do I know? But threads like these make me think that some entire branches of science are less and less about the search for truth, and more and more about establishing a “personal brand” made up of a bundle of research and papers, recruiting supporters, and defending that bundle from detractors. It sounds exhausting and not what comes to mind when I think “science.”
Same as it ever was, I think. It's just that when you look back in retrospect, you spend all the time talking about the paths that turned out to be successful. The history of science is littered with now-forgotten theories that, in their day, dominated their fields.
Textbooks and encyclopedias on physics that I'm familiar with do go there, though. I distinctly recall reading a lot about the fight between proponents of light-as-particles vs light-as-waves (and various experiments along the way that moved consensus), including various aether theories. Or, say, how the model of the atom evolved from simplistic solar-system-like stuff to probabilistic electron clouds etc. Even in middle school textbooks there was discussion of the originally dominant theories of gravity ("heavier things fall faster" etc) and how they were disproven. I'm not a science historian, and it may well be that various important details there were wrong, but nevertheless you did get a very clear impression that scientific progress involves a lot of loops, detours, and dead-ends.
Broader sociological problems aside for a second (academia does have issues for sure), one should keep in mind here that string theory is just a small subfield of physics and is not at all representative of physics as whole (or even theoretical physics). So don't let the pathologies that have developed there colour your view of physics or science generally.
I'd like to push back on this sort of gently but in a few ways.
1. Scientists are entirely human. Sometimes I think people expect more from both science and scientists. In the end, getting knowledge is hard. I have a copy of the Oxford Handbook of Epistemology which I keep on my night stand and every once and awhile it amuses me to read the first few chapters the upshot of which is "Fuck, we don't know how we know anything, really." Science works by having lots of unfruitfrul research programs. I won't say that research programs don't get "pathological" from time to time, in the sense that more energy is invested in them than it should be, but this is often only really discernible in retrospect. Even if a naysayer turns out to be right after a program has been explored, it doesn't mean that the naysayer was justified before the cards were all on the table.
2. Whether we like it or not, the search for truth is a practical matter, involving courting reputation, earning research money, winning war of ideas. This isn't so much new as it is profoundly more democratic than it used to be. Newton was famous for aggressively defending his reputation, to the point of arguably claiming to have invented things that he did not. Now we just have many, many, many more humans involved in science.
I think you've accurately described academia in general, and (if abstracted slightly further) the human condition. It's astonishing we've made any progress at all.
"A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die and a new generation grows up that is familiar with it" - Max Planck
Indeed, this is exhausting and many scientists do hate this, but in the existing system, if you don't play by these rules, you will have difficulties collecting funding and/or a tenured position.
The difference between good science and bad science is contingent on whether the search for funding aligns with the search for truth.
I like Loop Quantum Gravity, if only because I really enjoy reading Carlo Rovelli's stuff and listening to his talks, but it's really not going any better than String Theory is. Smolin's not wrong in ST getting too many resources, but every indication we have is that the competitors seem to have all of the exact same issues. We have no idea how to test them, their predictions are often wrong and require bolting on revisions, etc. If anything, that grant money and brainpower should likely be redirected to totally different fields where we can actually make progress.
Particle physics is in a really weird place. I'm a layperson, but it seems to me we're in a position where either our technology is extremely far off from being able to collect the data we need, or we've missed something very fundamental in our approach, and it's going to take a major rethinking to figure anything out. I am not optimistic that we're going to make any significant headway here in my lifetime.
Though, as a layperson my opinion on all of this isn't worth the electricity used by my computer when writing it.
This is just the Politician's Syllogism[0], though:
We must do something.
This is something.
Therefore we must do this.
[0] https://en.wikipedia.org/wiki/Politician's_syllogism
This "something" at very least works on some level — its a self-consistent theory that fits existing data, its competitors apparently cant.
Are the detractors of string theory saying we should stop doing fundamental physics entirely? I don't think so
> its a self-consistent theory
Nobody knows this since there is no exact mathematical formulation of "the theory" to begin with.
> that fits existing data
Nobody knows this either since nobody has derived either General Relativity or the Standard Model of particle physics as an approximation to any string theory model.
General Relativity is a straightforward consequence of basically any form of string theory.
My understanding of string theory is that there isn't even a proper string theory variant of the Standard Model, and that most of the models people are trying out are basically toy models that kinda resemble, say, QED. This means it's not even coherent enough to ask the question if it fits existing data, which is part of the premise of it being "not even wrong."
...which means nothing, especially since string theory didn't solve physics either.
AFAIK part of the problem is that the experiments needed to provide evidence for these theories either require insane energies, particle accelerators the size of Earth's circumference or even larger, or convenient access to a black hole.
This seems like a fundamental problem. If data is out of reach, we're left with nothing but noodling around with mathematics and simulation.
From the outside, this seems to rhyme with epicycles. You’re missing a core concept, so you pile on complexity to paper over the failed predictions.
The industrial organization failure is understandable. It’s all well and good to say “they should have recognized it wasn’t working and stopped” … but even if that’s true at the macro level, it’s very hard on an individual level.
An established physicist working on string theory has every incentive to keep building on that line of research. They have no competitive advantage switching to a new line. The specifics about how much expertise translate how far is beyond me, but it seems that nearby better ideas would have been found given the resources poured into this.
This is exactly The Innovator’s Dilemma. It’s even worse in academia than industry because the whole sector is so insular. I look forward to the reinvention of higher education and theoretical research…
Well, and add to that the fact that it's probably not clear what all these expensively-trained and equipped physicists should be working on. That may not be totally fair but you essentially have a large subset of scientific academia that has very little idea of how to go forward.
These physicists aren't that expensive, in the grand scheme.
True. And at least some of them would probably be doing pure math if they weren't doing physics. Some of their toys are, but again probably not that much really in the grand scheme. I think there's just a generalized frustration that a cadre of mostly very bright people seem to have largely spun their wheels for 20 years.
Oh man, what a shame all these people spent 20 years building tools in math, don't they know they could have been building advertising systems instead, and made a few people enormously wealthy!
I think it actually runs the other way. Because Physics is in the doldrums, intelligent people trained in Physics show themselves out and start building those advertising systems.
Personally I know many people who abandoned Physics to reinvent themselves as data scientists. Good for them that they were able to re-purpose their training; that doesn’t mean physics training is the best way to become a data scientist. My bias is that quantitative social science is a better route, although some of what it gains from focusing on people is often lost through less rigorous mathematics and software development requirements.
Otoh: very possible their work produced spin-offs that were useful in other fields (math advances, thought experiments, practical research tools & equipment, people in other fields having a look at their work from a different angle, etc)
AND having bright people chew on a subject for decades & come up (mostly) empty, is a good hint there's nothing there. 'Unknown' vs. 'we've tried hard & not found much' is a useful result by itself. Think of it as reducing the search space.
The problem with this argument is that it's very hard to quantify or even to test in general. And, of course, the obvious next question then is: if they were working on something else, could that have produced a lot more useful spin-offs?
The opportunity cost of wasting exceptionally intelligent people on unproductive and useless intellectual labor is substantial.
The opportunity cost of those individuals educating exceptionally intelligent students to specialize in this particular blind alley is even greater.
I think you might overestimate how fungible people exceptionally talented at physics might be towards other ends. I was an exceptional physics student and I've frankly never been all that productive at more prosaic tasks.
The fact is there just aren't that many people out there interested in string theory for you to get up in arms about. People don't complain nearly as much about mathematicians, who spend their time on much less practical areas of endeavor.
Frankly, the fact that some people get to make their living working on marginally-productive things that they like makes me feel a bit warm and fuzzy inside, in a way not unlike the experience I get giving my cat cat food and a place to sleep.
Is it? The world only needs a handful of physics every year. However the world needs a large number of people who are trained in the things you need to be good at complex tasks - they type of training you get when working on string theory.
Well noted physicist Dr. Sheldon Cooper did eventually give up on string theory and switch to another line of research.
https://www.imdb.com/title/tt3554854/
I went back for another degree a few years ago and from my perspective there's a "here's what the old people think" line drawn in conversations the old people aren't invited to. I don't know if a reinvention is in the cards but there are a lot of folks on their way up who don't seem to be particularly impressed with the current state of affairs.
I've read a couple of those. My favorite more recent video that I think also provides some good context is a rant by Angela Collier that I found to be really interesting and more condensed than a book. It is called:
"string theory lied to us and now science communication is hard"
It does a good job talking about the collateral damage to the public. An entire generation read Michio Kaku and Brian Greene and many others and believed this was all legit when it seems like it's been a dud for a LONG time. If you couple that with the reproducibility crisis, you have a public that is far more skeptical of what scientists say now than in years prior.
IMO public is generally critical of science unless they get some shiny toys out of it (and the causation is fairly immediate and obvious).
And, honestly, can you blame them? Nerdy places such as HN have a fascination of fundamental science that is nearly religious in some aspects - not in a sense of dogmaticism, but in a sense that pursuit of abstract knowledge is seen as noble and desirable in and of itself, with any justifications distinctly secondary. But from the perspective of your average person on the street, today, scientists are those people who ask for a lot of money, and use it to build those giant things that run some incomprehensible experiments which occasionally translate to some equally incomprehensible headlines in the news. And that person can think of many ways in which said money could be used to make their lives better instead.
Now, you can reasonably argue that long term, benefits are there regardless, even if they are not obvious, and thus the people actually in charge of allocation resources should disregard such simplistic takes and focus on that long term. But, either way, one cannot be surprised at the discontent.
Someone commented in the Economist a few years back that the last subatomic particle to have commercial applications was the neutron.
Ehhh, that's a poor take. The indirect benefits of fundamental research like particle physics are massive.
We all know about how the web — which turned out to have a few commercial applications — was invented by Tim Berners-Lee at CERN in order to facilitate better collaboration and data sharing among researchers.
There's the advances in high-performance computing and data processing, medical imaging innovations like PET scans, fundamental tech for touchscreens, and so on.
And don't get me started on the motivational and inspirational value of science and how it encourages people to pursue engineering and other technical endeavors. Hard to measure, sure, but it's damn important. There's a reason the moon landing was the most watched event in the history of television.
It's difficult to overstate these indirect impacts.
Reminds me of N. David Mermin's famous saying that perhaps the greatest contribution of String theorists to science was creation of arXiv :-)
I think there are many layers between the people who read Brian Greene's books and watched the reproducibility crisis unfold, and the public that has "lost faith in science". When I hear the latter, I think of vaccine skepticism and flat earth theories, not students who decided to switch to engineering. I think clickbait headlines and internet bubbles are, relatively speaking, a much bigger problem than string theory and bad statistics.
Off-topic, but I think we should stop calling them bubbles as they are getting larger and longer-lasting. It's more like they are domes, which don't pop easily. You've got people lying to poll-takers, rage-bait videos of people pretending to believe things they don't, trolling as a lifestyle, shared culture based off of weird beliefs... people can get away with avoiding truth and reality for longer than they used to. They can have happy lives doing it. It's a huge societal shift that I don't think has been properly analyzed yet.
Do you believe this to be a high quality style of thinking, if you consider it from a disconnected, disinterested 3rd person perspective?
You can argue that science "worked" in the case of string theory in so far as it (eventually) came to be seen as a lot of untestable mathematical games with zero experimental evidence to support it.
Of course, "follow the science" is more commonly interpreted as the scientific community consensus ~= the truth. So having a generation of physics that essentially ended up as "never mind" doesn't instill a lot of public faith that scientists know what they're talking about in general.
Its all very messy. The scientific method is about the best system we have. But the scientific method and academia are not the same thing. I've yet to find anyone besides some weird philosophers and contrarians who actually doubt the scientific method. But I find more and more people every day who doubt academia. And yeah. Its and industry made up of fallible people with incentives that are not aligned with the stated goals of said industry. We've had scandals. We've had falsified data. We've had falsified careers. And then there's the replication crisis where its possible an entire discipline is built on a foundation of slop. And then you have people who aren't technical themselves but chant trust the science as some kind of religious mantra. Which helps nothing frankly. And this mess leaves plenty of room for bad actors who take advantage of the situation and push their own warped agendas.
I just wanted to second this recommendation - while the video is nearly an hour long, it feels much shorter and is well worth watching: https://www.youtube.com/watch?v=kya_LXa_y1E
I’d wager most people don’t think about physical models of the universe at all
My understanding was that a unique virtue of string theory was that (for better or worse) it was playing out with pencils and paper, and not demanding billion dollar funding projects for particle colliders or other such infrastructure and thus was relatively harmless as far as competition for resources is concerned.
Not requiring billion dollar funding projects could be good or bad, depending on the reason.
If the reason is that the theory is making experimental predictions that can be tested more cheaply (as in a number of areas in condensed matter physics, where you can do tabletop experiments to test things), that's good.
If the reason is that the theory makes no predictions that are testable at all by any experiments that are doable now or in the foreseeable future, as with string theory, that's bad.
Totally agree. I tried to account for this by saying "for better or worse." But what are its actual, real-world claims on our major experimental infrastructure in the present?
> what are its actual, real-world claims on our major experimental infrastructure in the present?
At present, now that the LHC has failed to show any of the evidence for supersymmetry that string theorists were confidently predicting it would show, string theorists appear to be pushing for the next more energetic collider, confidently predicting that it will show evidence of supersymmetry.
I accept this as at least somewhat responsive. But (1) it's pretty vague and speculative as a statement about how resources have in fact been allocated thus far. And (2) it seems like no matter how much I try to clarify, you just can't resist making this into a matter of how bad string theory is, which is all well and good but is not the point of my question.
I was hoping for something along the lines of "Yeah, check out chapter 4 of Peter Woit's book where he gets into the crazy things he witnessed at his campus during the 2010s" or something like that.
I guess I'll just try Peter Woit's book and peruse his blog a bit to see what he means.
> is not the point of my question
Um, you specifically gave "not demanding billion dollar funding projects" as an advantage of string theory. So pointing out that string theory is in fact demanding such projects is exactly to the point. And it's not just right now; as my comment should have made clear, string theorists were promoting the LHC for the same reasons they are now promoting the next collider.
One resource could be the minds of brilliant scientists.
They may be brilliant, but if they're string theorists, they aren't scientists.
Or at least that's Woit's point.
Agreed, I think this is the strongest counterpoint. But it effectively requires restating the point to clarify that it's tying up minds, time, energy, which are non-trivial things; but not infrastructure.
Not remotely true. The predictions theoreticians make guide what experiments are made. If the predictions are of low quality the experiments are unlikely to give us any valuable data.
Let's say I agree to that. How does that translate into an argument that string theory is hogging resources (e.g. funds, infrastructure, colliders, space telescopes) that are now no longer available to alternative projects?
Yours sounds like an argument that it's not making good or testable predictions, certainly an indictment but not (so far as I can tell) responsive to my Q.
Given the lack of testable predictions and failure in experiments so far, string theory should be called string hypothesis.
(I'm also not a theoretical physicist). Not entirely true, I was looking at proton decay recently and one model of string theory model apparently predicts 10^36 yr lifetime [1] which is within experimental reach.
[1]: Igor R Klebanov, Edward Witten, Proton decay in intersecting D-brane models, Nuclear Physics B, Volume 664, Issues 1–2, 2003, Pages 3-20, ISSN 0550-3213, https://doi.org/10.1016/S0550-3213(03)00410-3. (https://www.sciencedirect.com/science/article/pii/S055032130...)
One model? So there may be models where it doesn't happen. Or perhaps that very same model makes other, verifiably wrong predictions.
For this might want to assume that for each proton its lifetime is a random variable that obeys a Poisson process.
That's asking a LOT, might be seen as putting some severe constraints on what is going on with a proton and its internals.
If there are an infinite family of parameterized string theory models, it's basically guaranteed that you can pick one that predicts anomalous data. In other sciences you would adjust the P value for the probability that you can reject the null hypothesis given the number of experiments you're performing, which in the case of infinity is going to drop the probability of rejecting the null to zero.
If there are no testable predictions it is not a hypothesis, it's a religion.
Well, String Phenomenology is a thing [1]... although more recently they appear to have to switched away from studying the frankly gargantuan set of viable vacua in favour of examining the even larger set of non-viable models [2]. And the choice to take research in that direction is just somehow just so quintessentially string theorist.
[1] https://en.wikipedia.org/wiki/String_phenomenology
[2] https://en.wikipedia.org/wiki/Swampland_(physics)
Given the sociological aspects how about: String game theory?
I think it's funny that Woit manages to this day sound exactly like he's some sort of underdog fighting the big corp despite having lived to see the death of string theory.
Is it in fact dead?
Mostly yes, in fact a fair number of people will tell you the killing blow was years ago. The corpse hasn't rotted away yet.
This would be news to every Department I know of. So dead and rotting in favor of what exactly?
Just because grandpa is dead doesn't mean anyone has filled his job position. Nothing useful has come from string theory in a very long time. Or are you still stuck in infinite tiny dimensions that can predict anything and everything, except something testable?
Oh don't misunderstand I am fully against String Theory. I just was not aware anyone considered it dead as in literally no longer controlling the Theory field. I'd challenge you to find good postdocs in High Energy Theory that aren't String related as a gauge of what the field is still focused on.
Thanks for above. As Woit mentioned, the video format is great and for guys like me.
PBS Spacetime is where I go for a lot of "layman-with-the-lightest-touch-of-math"[0].
[0] https://www.youtube.com/c/pbsspacetime
[EDIT]
Phewww reading those 2004 comments on those posts. Professors getting really heated for sure.
I just tried that: Right away he was talking about the possibility of the universe being "infinite".
Yup, in physics courses, that one word was time to lose respect for the course, f'get about it, think about some of the pretty girls on campus, and get back to math, e.g., my paper on group representations, apparently of some interest in physics.
PBS Space Time is great but you can't just drop in with a random video, they often build on top of or expand on concepts explained in earlier videos. And that's just fine.
If that's the book I'm thinking of I was also initially impressed until like chapter 6 when, after spending the book talking about how simple and elegant this theory was, it opens with "what if there wasn't just one string but lots of strings, and they were n-dimensional etc etc..." and threw it all out the window. I put the book down.
For those who have seen these critiques of string theory (and other issues in modern physics) and are wondering why so many physicists have bought into string theory, Sean Carroll recently presented a pretty full throated defense of the physics "orthodoxy":
https://youtu.be/MTM-8memDHs
I found it a really useful overview of what led people to the current state of physics.
I took undergrad quantum physics with Prof Greene and it was a great time. I definitely could have chosen a better professor for the math, but the theory and his banter was fun.
Yes. Basically you can track how physics went astray very easily. Physicists were grappling with the philosophical ramifications of some of their discoveries at the same time that experimental data was starting to get much much more expensive to generate and the success of QCD and the standard model created a culture of "shut up and calculate" where physicists put on horse blinders and just tried to make the math work without any real consideration for anything beyond fitting the data. That was fine for a while but now physics is at a crisis point where our models are elegantly accurate to a point but clearly wrong, and physicists as a group have mostly forgotten how to imagine, so the only tool left in their box is pushing numbers around.