People often say that the problem with string theory is that it doesn't make any prediction, but that's not quite right: the problem is that it can make almost any prediction you want it to make. It is really less of a "theory" in its own right and more of a mathematical framework for constructing theories.
One day some unusual observation will come along from somewhere, and that will be the loose end that allows someone to start pulling at the whole ball of yarn. Will this happen in our lifetimes? Unlikely, I think.
The problem is that once, a long time ago, String Theory was something that made concrete predictions that people just couldn't calculate.
Then people managed to calculate those predictions, and they were wrong. So the people working that theory up relaxed some constraints and tried again, and again, and again. So today it's that framework that you can use to write any theory you want.
That original theory was a good theory. Very compelling and just a small adjustment away from mainstream physics. The current framework is just not a good framework, it's incredibly hard to write any theory in it, understand what somebody else created, and calculate the predictions of the theories you create.
I am old enough to remember when string theory was expected to explain and unify all forces and predict everything. Sadly, it failed to deliver on that promise.
And there is no known single real world experiment that can rule out string theory while keeping general relativity and quantum mechanics intact.
More accurately, string theory is not wrong (because it just cannot be wrong). Because it does not predict anything and cannot invalidate anything, it does not help to advance our understanding of how to integrate general relativity and quantum mechanics.
It should not be called theory - maybe set of mathematical tools or whatever.
You can't really show it's wrong because there are dozens of different theories but using the Wikipedia definition "point-like particles of particle physics are replaced by one-dimensional objects called strings" it's possible that particles are not strings. I guess it would then be like fairies at the end of the garden theory. Good from a literary fiction point of view but not reality.
I was planning to make a similar comment. Conjecturing that some theory in the string theory landscape [0] gives a theory of quantum gravity consistent with experiments that are possible but beyond what humans may ever be capable of isn't as strong of a claim as it may first appear. The intuition I used to have was that string theory is making ridiculously specific claims about things that may remain always unobservable to humans. But the idea is not that experiments of unimaginable scale and complexity might reveal that the universe is made up of strings or something, it's just that it may turn out that string theory makes up such a rich and flexible family of theories that it could be tuned to the observed physics of some unimaginably advanced civilization. My impression is that string theory is not so flexible that its uninteresting though. There's some interesting theoretical work along these lines around exploring the swampland [1].
Or, that day will never come, because string theory isn't reflective of the actual world, or because there are so many theories possible under the string theory rubric that we can never find the right one, or because the energies involved to see any effect are far beyond what could be reached in experiment.
It isn't completely implausible that a future civilisation could perform the experiments to gather that data, somehow; but it is hard to envisage how we do it here on Earth.
Your implicit point is a good one. Is it sensible to have a huge chunk of the entire theoretical physics community working endlessly on a theory that could well end up being basically useless? Probably not.
There is not a "huge chunk" of the theoretical physics community working on string theory, and their never was. For one, it is far less common a topic of research now then it was earlier when it was more popular, but even then "huge" was really "a lot of universities had a grant for string theory investigation because it looked promising".
It mostly hasn't worked out and now people are moving on to other things.
The single worst thing that happened though was the populism: a small group of people with credentials started putting out pop-sci books and doing interviews, well in excess of what their accomplishments should mean. People are like "so many people are working on this" because there were like, 3 to 5 guys who always said "yes" to an interview and talked authoritatively.
Huge is a subjective term, but go and count the number of participants at Strings 2025 [1]. Then realise that is just one of many conferences [2]. It's still a very big field.
A meaningless statement if you aren't going to introduce any points of comparison. But I would hardly call 735 conference participants a huge conference. Like, that's big but there are lot more then 735 theoretical physicists.
Claude tells me that there are about ~5000 theoretical high energy physicists actively publishing as tracked by INSPIRE-HEP (the de facto search engine in that field). If we estimate that about a third or half of string theorists take part in Strings in a given year -- because there are other big conferences like String Pheno that will be more relevant for many -- then we have something like 30-50% of high energy theorists working on string theory.
I agree that people should be "moving on to other things," but I'm not seeing the evidence that they actually are.
> the problem is that it can make almost any prediction you want it to make
In logic this is either the principle of "contradiction elimination" or a "vacuous truth". Depending on how you look at it. i.e. given sufficiently bad premises, you can prove anything.
The Planck scale where string theory's distinctive physics should appear is around 10^19 GeV. The LHC operates at about 10^4 GeV. That's a factor of 10^15 which is a million billion times too weak. No foreseeable accelerator technology can bridge this gap. The proposed Future Circular Collider (FCC) would reach maybe 10^5 GeV. Still 14 orders of magnitude short.
Non-Euclidean geometry (geometric axioms in which one postulate is rejected such that the 3 angles of a triangle are not exactly 180 degrees) was considered a meaningless word game and fundamental mistruth.
Later, non-Euclidean geometry was actually essential to modern physics.
It's intellectually sketchy to judge future value by the present.
Might as well fund someone researching whether quantum theory run on little gnomes, if there is no serious path to verification after 50 years, why not quantum gnomes?
On this topic (parallel postulate), it took ~2000 years from Euclid and then 3 people all came to the same conclusion independently within ~10-20 years.
Is it so weird? See Multiple discovery https://en.wikipedia.org/wiki/Multiple_discovery and Zeitgeist https://en.wikipedia.org/wiki/Zeitgeist namely that there might, or might not, be objective knowledge out there describing properly an objective World but we as a specie do chip at it with itself over time. When a new discovery in any field is made it propagates through our social network and tools we have for it, e.g. cafes, scientific journal, Web. As soon as something is discovered most of us connected enough get the new tool or perspective, update our Worldview and chip it at it again. IMHO this way it seems pretty normal that things hitherto unknown, no matter for how long, become knowable to seemingly independent discovers.
> We should stop funding research into prime numbers. They're stupid and useless. Who cares about them, if they will never be used for anything? Number theory should be stopped, you may as well research gnomes.
I imagine this is what you would have sounded like 100 years ago.
You may be understating how much 15 orders of magnitude are.
The only truly exponential technological progress we’ve ever had, transistors, only scaled by ~5 orders of magnitude in feature size. Thermal engines went from maybe 0.1% to ~50%, less than 3 orders of magnitude, in about 200 years. There’s very fundamental physical laws that suggest that engines are done, and transistor scaling as we have known it for 30 years is also done. Perhaps very clever things might give us 5 more orders of magnitude? E.g. truly 3D integration somehow? Then we’re still 5 orders of magnitude off from our target. I can’t think of any technology that ever improved by more than 10^6, perhaps 10^9 if you count some derivative number (like “number of transistors on chip”, rather than actual size), and that’s from literally zero to today. Not from already-pretty-advanced to Death Star scale.
Another perspective is that, to get to those kinetic energies, we need accelerators as large as the solar system. Possibly the galaxy, I can’t quite remember. Will you concede that galaxy-wide objects are so far from current reality that there’s no point seriously talking about them?
Are you seriously insinuating that string physics are asking for this collider you alone entirely made up? As if people who actually do study string theory are too stupid to know primary school math and this criticism is somehow high-brow and novel?
Not to mention you entirely missed the point of what I said. There is research into the most niche, useless fields imaginable, because not every endeavor taken by every human being needs to be profitable or applicable. Sometimes people are just really good at making jigsaws or want to make a stinky chemical or get fascinated with properties of prime numbers.
And then, sometimes, those turn out to be the fundamental underpinnings of an entire generation of economic and military strategy. You can't often know what spurs what in that sense.
I didn’t make it up, it’s a well known talking point around string theory. I think it was first mentioned by a practicing string theorist. Of course it’s not a novel critique, but I’ve read about putting data centers in space on this website, so I think it’s worth trying to teach people how to do these sort of Fermi problems quickly.
I did indeed miss your point, it was well hidden under a lot of sarcasm. I think it is of course completely valid. People should be free to research what they want, and I’m sure string theory must be beautiful mathematics.
But if your goal is unifying QM and GR, and/or achieving a theory of everything (as is for most theoretical physicists), then me and a growing fraction of physicists think that it’s not a promising avenue. I’m not advocating for only working on “useful” things, because such a theory is not likely to yield much profit to anyone in the foreseeable future anyway. But if you state that a unifying theory is your goal and seek funding for that goal, then string theory should move to the backstage. The mathematics department would rightfully be happy to house you otherwise.
>Non-Euclidean geometry (geometric axioms in which one postulate is rejected such that the 3 angles of a triangle are not exactly 180 degrees) was considered a meaningless word game and fundamental mistruth.
This is just a lie though. Non-Euclidean geometry is a mathematical model of how distances behave on non-linear spaces. Nobody ever believed it to be a "fundamental mistruth", even suggesting it would look ridiculous. It would be akin to denying linear algebra, even the meaning is unclear.
That the physical reality of space is not linear was a shocking revelation, since all human experience and basically every experiment done up until that point indicated otherwise.
"Lobachevsky [mathematician contemporary of Gauss, who claimed parallel postulate was unnecessary] was relentlessly criticized, mocked, and rejected by the academic world. His new “imaginary” geometry represented the “shamelessness of false new inventions”"
Further, many claimed premature success in finding logical contridictions in geometry lacking parallel (Euclid's 5th) postulate; which meant they believed a 4-postulate geometry to be fundamentally false.
you are mixing up gambling spend vs whole industry spend. If string theory was a small handful of people making up a small m*nority of physics departments like non-euclidea geometry research was that would be fine. Its huge swaths of most physics departments and a huge suck on research funding. For that kind of spend you better show results because you are in production phase at that point not lotto ticket moonshit phase. If we are buying lotto tickets with the money bey lots of different lotto tickets not a whole bunch of one lotto ticket
As a percentage of theoretical physicists it is probably significant though. A Better question is how much love/money/attention is going into rival theories ?
It is basically this. People arguing for string theory have no concept of how to maximize return with uncertainty. The thing had 50 years of substantial funding and substantial mindshare and pushed us nowhere. Any rational person with basic risk understanding would know at this point its a fail and we are in the not knowing what to pursue phase so we should be supporting small investments in dicerse options &ntil something promising happens then we can concentrate funding there &ntil that times out or gices us the understanding to achieve something new and great. The lifecycle of increasingly aupporting string theory s=ould have turned 2 to 3 decades ago instead of just recently. We lost atleast 20 and more like 30 years of progress we didnt have because a bunch of very smart people captured the physics funding aparatus to enrich thselves.
Is this a typo? I see a lot of words being censored these days and I assumed it's because of some algorithms and visibility. That shouldn't be the case here tho..
Yeah, even just trying chart a course on a ship across a reasonable distance will cause you to need to reevaluate some "obvious" things (like "what path is the shortest between these two ports" being a curve rather than a line).
Thanks for posting that; as soon as I saw the title here I was going to look that up if no one else had already. Sabine Hossenfelder too, though there's far too much content from her on this to put a list, but anyone interested might like some of her takes.
A few debates between Brian and other notables; Hossenfelder, Eric Weinstein, and Roger Penrose to name a few; have popped up in my youtube feed lately which are typically also engaging.
Hossenfelder is not really comparable to Collier. Collier's video is critical of string theory as a testable framework but she ultimately still supports people who do research in string theory. Most of her criticism is with media coverage of string theory, not the research or the researchers.
Hossenfelder has gone off the "the physics establishment is all idiots and they are suppressing the real physics" deep end and has converted specific complaints into trashing the entire field.
I'm not a fan of Hossenfelder, especially for casting quacks like Weinstein, but AFAICT she isn't about "suppressing the real physics" but more of a "establishment physics is wasting money and time, and a lot is equally bad/good as some alternative physics."
She proves my theory that people who are successful on social media will lose their minds over time. It’s too easy to fall into the contrarian or cheerleading trap because there is too much money and fame in it. Being nuanced is boring and doesn’t sell
A year ago that might have been the case. Her more recent stuff is fairly dire. I believe that the algorithm encourages her and channels like hers to become more and more conspiratorial and less and less nuanced.
Don't agree, she spreads misinformation, she's disrespectful to other scientists and basically has resorted to just claiming that everything in academics is wrong. YouTube fame has completely radicalized her.
> Most of her criticism is with media coverage of string theory, not the research or the researchers.
I pretty strongly disagree with that categorization of Collier's video, as it makes it sound like string theorists were innocent bystanders and "the big bad media" just ran overboard.
I think she puts the blame squarely on string theorists (e.g. "celebrity string theorists who wrote all these books") as constantly hyping up the field with promises of "in a decade it will be amazing" - a phrase she uses to great dramatic effect throughout the video - despite never acknowledging the fact that it fails miserably at making testable predictions.
When she says "they lied to us", the "they" she's clearly talking about are specific researchers in the field (which she names), and the string research community more broadly, who are hyping up their field, not just "the media".
The problem with sabine is that she's become the worst person to make a correct point for the wrong reasons
If you do research it becomes pretty apparent that a high number papers are not great. There's varying issues, but a big one is that the funding model incentivises pumping out papers which are often of low quality, researching whatever happens to be in vogue at the moment
Literally everyone I've ever talked to in research as a frank conversation knows that this is a massive problem, but nobody wants to talk about it publicly. Research funding is already completely screwed as it is, and researchers are incredibly aware of how fragile their livelihoods are
Its clearly leading to a big reduction in the quality of the literature. I went on a replication spree recently and found that a pretty decent chunk of the field I was working in was completely unreplicable by me, with a few papers that I strongly suspect 'massaged' their results for various reasons
I wish someone would talk about this who wasn't also in bed with right wing grifters, and was actually credible. We need someone more like ben goldacre for physics
Sabine's most interesting content is the paper reviews, and where she sticks to actually examining the evidence - but it makes up a tiny fraction of what she produces these days, and her support for some truly grim figures is just gross
Your paragraphs two, three and four are exactly what Sabine is communicating. So much so that it almost sounds like you pulled a transcript from one of her videos.
I don't think you're describing "the" problem with Sabine. She's not what you want her to be but that's a you problem. You're describing your particular problem with Sabine.
I appreciate that she's doing a lot to bring attention to the real issue despite your claim that she is supporting grim figures. I know about the problem because of her work, but I have no idea who Ben goldacre is.
Also no idea what you mean by supporting grim figures. I checked to see if she has come out in support of Jeffrey Epstein or something crazy like that, but no.
> I checked to see if she has come out in support of Jeffrey Epstein or something crazy like that, but no.
Bro she blurbed "The War on Science," a book stuffed with racists and sex pests complaining that they lost their jobs for falling in love with their graduate students, writing them love poetry on tumblr, and then kicking them out of their research group because they could stand to be near them. Or for saying that they "don't shy away from the word superior" when discussing white people being better at running societies and lying about the GPAs of black students. Or for taking joking photographs with human remains.
And yes, the authors of the book include people who provided support in the legal defense of jeffrey epstein.
And its not something that's just a 'you' problem - if you want the actual underlying issues in physics to be fixed, its a massive issue that the spokesperson for fixing those problem currently may be a bigot, or at the very least endorses bigots and sex pests. Beyond just being generally completely unacceptable, it allows everyone to completely dismiss whatever is being said very easily
For the other poster, ben goldacre is someone that's become very well known for making effectively the same points as sabine, but within the pharmaceutical industry. They sat down and basically wrote for decades about how the testing was absolutely broken, multiple books, a column, and producing lots of work on how broken studies were in medicine and talking to anyone that would listen - and as a result, they were actual able to enact effective change. It was a huge win for evidence based science!
Sabine is not someone who can achieve that in physics - her videos would be much more effective if they contained actionable content and concrete analyses of the issues. I'd have a tonne of respect for her if what she did was publish papers or videos showing the degree to which the literature was broken, analysing funding, conducting interviews (even if anonymous) with researchers, looking through examples of bad papers and explaining the problems to a lay audience. Producing a mixture of for-scientist and for-lay person material to break the figures down, in a way that produces a compelling argument
Instead we at best get specific examples plucked out of the air. I know she isn't massively overgeneralising the issue from my own personal experience, but she presents a terribly uncompelling argument as to why there are problems. Where's the data? Why are you writing book blurbs for sex offenders instead of writing papers?
That's why I've come around increasingly to the idea that she's a grifter, even though I used to enjoy her content (before it went out of the window) and think that she does likely genuinely care about the underlying problem to some degree. Its closer to ragebait than anything that feels productive now unfortunately. I don't think its even necessarily on purpose on her end - the right wing has a way of sucking in anyone on the fringes and giving them a home even without them knowing, but also why give her the benefit of the doubt?
I agree with a part of Sabine's overall output, but she's increasingly misidentifying some of the problems and the solutions because she's drifted too far towards the grifters
To a large degree if you're trying to successfully trying to push for change, it really matters that the person pushing for it is credible. Someone like ben goldacre is able to credibly make a strong push for change within medicine because they've maintained credibility, someone like sabine makes the situation worse because they've chucked it away
Sabine's has a day job as a Youtuber, and she makes her videos from that perspective. She speaks her mind, makes a decent living, and educates some science nerds on the way. Seems pretty nice.
From the perspective of accomplishing institutional change in the academic physics world, this is does nothing. The institutional powers don't react at all to a complaining influencer with an Einstein doll.
And I suspect she's perfectly fine with that. Overturning the Physics establishment is a near impossible task. I would leave that for those mad enough to try.
_totally_ off topic, but what sort of brain must Ms Collier have that she can play a game at the same time as giving a cogent lecture on String Theory with very few hesitations? I could hardly concentrate on the lecture because of the game being shown in an inset window. Truly impressive
Yesss! I had an ex complain/advise that, if I could just stop thinking for a moment, I'd enjoy life more. In my mind, that's what Ms. Collier is doing: distracting her hyperresponsive brain parts so she can present a longer speech on the topic.
I definitely don't walk away from any of Brian Greene's content thinking that String Theory is anything close to a confirmed fact at all.
It's been some times since I read his earlier books, possibly his tone has changed?
I'll also say, I'm far from a professional physicist. I'm reading and watching for fun and intellectual curiosity, not to learn physics with the goal of doing my own research. I always thought of String Theory as being more of a study of math where many people have unsuccessfully tried to apply it to physics. And, that it's lead to some really interesting ideas. I just find him and his work really enjoyable.
> It's been some times since I read his earlier books, possibly his tone has changed?
I think her point is more that his tone hasn't changed. If you're curious I would just watch the video. Angela comes with the perspective of also having read his earlier books and having liked them.
I have a PhD in high energy theoretical physics (hep-th for short) and I've written a paper on string theory, so I'd like to comment on some things:
1. I think there are two reasons why string theory is cool (other people may have different opinions). Please note that none of these two reasons are directly related to the extension of Standard Model.
1.1. String theory is the only theory so far that can mix gravity and quantum mechanics, and it can be even used to derive Hawking entropy of a black hole from "first principles" (see paper by Strominger and Vafa). The obvious trouble is that the black hole in question lives in five-dimensional space and is unrelated to the real-world black holes, but this is way better than what one can get from Standard Model physics (which is, no gravitons for you).
1.2. Through AdS/CFT correspondence, string theory can be used to describe quantum field theories that are not related to string theory by themselves. This gives a very strong tool to study these quantum field theories, and the paper by Maldacena that discovered this correspondence is one of the most important papers in the field.
2. It is true string theory is unusable as of now to derive the Standard Model physics (and provide extensions for it). Unfortunately, I would say that hardly any papers in high energy _theoretical_ physics currently address Standard Model physics. Roughly speaking, in late 1970s, after quantum chromodynamics was established and the asymptotic freedom was discovered, it turned out that it is extremely hard to compute many things we are generally interested in. At this point, high energy theoretical physics split in two sub-areas: phenomenology (which tries to extend the Standard Model to derive things like neutrino mass) and theory (which is a more formal theory and tries to answer questions like "how to quantize gravity"). One can argue that this makes hep-th an area of mathematics, and I would agree with that (eg in Cambridge theoretical physicists are in the same department with applied mathematicians).
2.1. The things theoretical physicists study tend to pop up in various places, even if the original motivation is misplaced. Even the string theory itself originated as a way to explain the Regge trajectories (which were explained with quantum chromodynaics afterwards), and not to quantize gravity. For a more practical example, Witten introduced topological quantum field theories long before anyone understood how to apply them to real-world physics.
3. I do not agree that string theory dominates the hep-th field. I would say that its popularity changes with the time, going up and down. While the main conference in the hep-th field is called "Strings", the talks at it are not necessarily related to strings theory, and at the 2025 conference I'd say that only 1/3 of the talks were anyhow related to the strings theory. Moreover, there is no hard division between people working on string theory and people working on other hep-th subjects, so that e.g. Witten made many contributions to hep-th which are not anyhow related to string theory.
3.1. As for the push to do string theory that eg Sabine Hossenfelder alludes to, I'd say that I experienced no such push during my MSc and PhD studies. I've written four papers, and worked on a couple of projects that did not become a paper, and out of those, only one was dedicated to string theory.
3.2. On the other hand, the more fringe theories that can provide alternative to string theory are also more high-risk endeavors (as you are quite likely to fail to produce anything coherent within a typical timeframe you allot to write a paper). Hep-th is strongly underfunded, and I believe, that with greater funding (and less need to publish-or-perish) some people would also pursue the more fringe directions in hep-th.
3.3. A comment on the naming: hep-th is a field which is very hard to name. The name I use is the traditional one (and is used as eg a name for the field on arXiv). However, many things derived by the physicists in the field are not anyhow related to the high energy in the literal meaning of the words "high energy". When talking to people at a party, I say that I studied string theory, because the name is catchy and it rings a bell, but this way of referring to the field is definitely a misnomer.
Thanks for the comment that exposes the nuances. As a non physicist who is interested in physics, I would say that the predicament is that we simply don't have enough data to tell how to improve our physics theory, but we have too many physicist working in the field, so ideas just get staled.
Not exactly, I'd put it as follows:
1. In phenomenology (the science that looks into extending Standard Model) we'd definitely benefit from more data (with most viable data sources, in my opinion, being not the colliders but the detectors of extraterrestrial particles such as PandaX or Fermi-LAT). However, this doesn't stop us from getting new results, narrowing the window of possibilities for the properties of the Standard Model extensions. This "sorting a haystack in search of a needle" approach may not sound too cool, but this is exactly how we discovered the Higgs boson, for which we looked for more than twenty years.
2. In hep-th we currently lack either enough data (which we can't really collect now), or an ideological breakthrough in solving one of the hard problems. Unfortunately, the problems are indeed very hard, so that one of them (Yang-Mills existence) is a Millenium Prize problem. This caused the de-facto shift of hep-th into applied math, so now hep-th is not constrained by the data problem, and is developing as actively as an area of applied math can.
Here is my question to string theorists: suppose some physicists came up with an alternative theory of everything and were able to use it to make unique empirical predictions. Would you accept it as true and abandon string theory?
What experiment(s) would we have to run to see deviations from the Standard Model and be able to come up with newer models (maybe String Theory maybe not)?
Is it just about higher energy particle collisions? Or does it involve things like doing experiments next to a black hole?
String theory has always seemed intuitively wrong to me. From Wikipedia:
>In theories of particle physics based on string theory, the characteristic length scale of strings is assumed to be on the order of the Planck length, or 10E−35 meters
Yet electrons repel each other over distances of many meters by I think the virtual exchange of photons. How on earth would that work? How does your photo string know to head to an electron string trillions and trillions of times it's length away?
As far as I can tell the field became popular for sociological reasons that you could get grants for it and the like rather than any connection to reality(?)
You're being somewhat unfairly voted down, it's a legitimate questions because the popular media so grossly misrepresents what string theory is, especially in their visuals.
It's hard to visualise in 3D, but if you cut down the spatial dimensions to just 1D (a line), then theories like string theory just turn the infinitely thin mathematical line into a tube. You can picture a tube that vibrates, or has waves in its cross-section. Don't think of the the "strings" as actual little loops moving around in space, they're a modification of what space is.
You can even do the same kind of line->tube extension of a space with even more extra "loop" dimensions than the number of base dimensions. AFAIK the current theories have 10 total, of which 3 are the usual "large" dimensions of space, the rest are "small" and rolled up like the tube example.
Even so I don't get how electrons a meter apart interact through that stuff, as opposed to the electrical fields which spread out through space and so interact with other electrons as featured in quantum field theory which is what physicists use to actually calculate physical results, as opposed to string theory which fails to calculate actual physical results.
"if you cut down the spatial dimensions to just 1D" doesn't sound very physical to me.
I'm maybe being downvoted fairly. I studied physics and it don't think it's a misunderstanding of popularisation or that string theory is untestable, I just think it's straight wrong and not how the physical universe works.
> Even so I don't get how electrons a meter apart interact through that stuff
Very roughly: It's possible for point-like (or tiny looped) particles to interact as long as they take every possible path instead of just the one path that would cause a collision. How you interpret this is... up for debate. I prefer the many-world interpretation (MWI), but not everyone agrees.
> "if you cut down the spatial dimensions to just 1D" doesn't sound very physical to me
That's just a simplification to aid understanding, it's now how the theory actually works.
Yeah maybe. My flatmate of some years was doing a PhD in string theory at UT Austin along the lines of "if you cut down the spatial dimensions to just 1D" but he was a mathematician, not really a physicist and was ok with that if it produced interesting mathematics. For real physical things like wiring the lighting system I'd do it because he wasn't so good with that.
I think he went into string research because he was good at maths and there was grant money available for that rather than a deep belief that that was the nature of reality, which is kind of what I mean by sociological factors.
I think much string theory may be like that. Interesting maths but not good at figuring where electrons go.
Except this is how electrons actually go, and it has real testable consequences. The question I'm aware of (because it related to my degree in nanotechnology) was: are metals conductive at different dimensionalities?
Because at the nanoscale, you in fact can have 1D, 2D and 3D metals. 3D metals are bulk solids - like we're familiar with. 2D metals are planes of single (or very few) atoms. 1D metals are lines - think placing individual metal atoms down in a row - nanotubes are a practical example.
All real, possible structures to build.
When you do measurements on all these structures you get...weird answers. Like is a nanotube a superconductor? And the answer is...yes, but also no. Yes because you'll in fact view superconductivity like behavior, but no because actually it's a ballistic electron conductor - at the right energy level an electron bounces through the thing without hitting it, but not all electrons can do that at all energy levels, so you still measure a voltage across a nanotube between two conductors.
But a nanotube is 1D - we only have 1 dimension things move in (from one end to the other). So - conductive, not a superconductor, but you can kind of use it like one sometimes. And we know 3D metals are conductors - that's obvious right...so what are 2D metals? Presumably conductors right...?
And the answer is...nope, insulators - at least sometimes. And the reason is because the sum of all possible electron paths in a 2D metal is the electron always returns back to where it started - and those grow much faster mathematically then paths where the electron ends up somewhere else.
But only in 2D: in the 1D case most paths take you out of the conductor. And in the 3D case, the number of paths which land you somewhere else grows much faster then those which loop back, due to the extra dimension of freedom. But 2D metals are constrained - for any given path elsewhere, there are mathematically far more that land back where you started. This is observable, measurable behavior which is a topic of research for future semiconductors. Yet it's almost entirely quantum probability based behavior.
The string theory model is structured from the start to reproduce existing theories as a consequence, so the problem here is a lack of understanding on your part rather than a mistake in the theory. I do suspect that most people who are working on this stuff (or any stuff for that matter) don't think very hard about the basic phenomenological claims to the point where they can explain them well.
In particular your model of electric fields isn't very good. An electric field's flux around a volume reveals the presence of a particle in that volume. That's not because the field, a bunch of vectors in space, "happens" to integrate to something nonzero if there's a particle in that volume: it's because in some sense the presence of a field with a nonzero flux and the presence of a charged particle are the same thing; the particle is the existence of a divergence in the field within that volume.
Moreover in QFT (and this part is handwavey as I only learned enough to vaguely understand this, but it's better than nothing) the presence of the "field" ends up looking like the sum of what you get if you integrate over every possible way of a emitting or receiving a photon at that point; the accumulated integrals destructively interfere in such a way as to produce a value which reflects where the particles are. So very roughly idea of a field existing at a point and having a "value" is like saying: there are a bunch of things out there that I (a charged particle) can detect by exchanging photons, and the accumulated effect, when you consider all the different quantum superpositions of ways of doing that, is a single vector which induces a force on me. Other fields add up to more complicated objects than vectors.
Once you look at things like that, there should be no objection to how strings and electrons might interact. Whatever's going on at that string level averages out over larger timespans to just look like electron field. Not dissimilar from how all the individual charges in an atom average out to look like a single charge (but are perhaps detectable if you get up really close, in dipole and higher moments, or in how the atom deforms / reacts to nearby charges).
It might help to be aware of the concept of a topological defect (https://en.wikipedia.org/wiki/Topological_defect; there's a great explainer article somewhere that I can't seem to find) as a reductive picture of what a particle "is". I've heard this doesn't work for fermions for some technical reason, but in any case it's very useful as an illustration of the sort of thing that a particle "can be": a vortex in a material can act like a particle and even exhibit attractive/repulsive forces. So I picture the string theory model as answering the question: what kind of substrate could produce vortexes and other "defects" that act like the particles we see? Dunno if that's accurate but it seems like a natural question to me, anyway.
I can definitely buy a lack of understanding on my part - my understanding of all this is quite fuzzy. But I'm not sure string theories reproduce existing theories so much a say this is compatible with the other stuff in a handwavy way? I don't think there's any "we assume strings and thus can deduce quantum mechanics and general relativity" stuff? I don't think anyone can deduce quantum mechanics and Einstein's deductions with relativity are based on simple observations like the speed of light being observed to be constant and acceleration seeming similar to gravity?
It's not "we assume strings and deduce QM" it's "strings are a model which is defined so as to produce QM and also...". It is, by design, a theory of QM and GR. That's the point. It's a claim about what lies "below" the level of the individual fields in QFT which gives rise to them (and also gravity).
whether or not string theory is at this point grifty and weird, the theoretical basis for it is far stronger than you would think based only on reading critics / pop sci explainers. It is not like, missing any obvious physical facts in its foundation. Rather it is trying to say: look, we have this zoo of particles with seemingly random masses and properties; is there same lower-level framework which can produce the zoo that we see according to a simpler list of rules? The obvious choice for this, especially given some of the "hierarchies" of particles that are observed, is that they are in some way resonant modes of some kind of underlying object. Which is where you get the strings from. (Which might sound like a weird justification if you are not aware of all the other aspects of physics which get explained as resonances of fields; this is a standard sort of justification which there's a lot of good reasons to be interested in, at least initially.)
30 years ago in college, at a physics club talk, I got my first intro to string theory. I didn't understand it but was intrigued enough to go to a small one-off seminar led by Prof. Greene. About 15 people around a table while he spoke. I kept thinking I was too ignorant of the subject matter to be able to ask a question. But nobody asked any questions.
I think that's not quite right: it is reasonably certain that string theory can produce both the standard model and most extensions people have dreamt up, so the problem is rather that all the obviously "stringy" predictions are currently unavailable, while the string theory derived predictions for achievable experiments look like what we get from other theories we already have.
To make this valuable, it should produce a limited set including standard model. If you produce pretty much everything one can dream of, that does not carry predictive power.
What does string theory predict that (1) is within experimental reach in, say, 5 years (2) if not found, would prove it wrong. Was there ever anything satisfying these two simultaneously? AFAIK,the answer is "no".
No, I am simply stating what is expected of a good scientific theory in physics. Such a theory should have power to explain things as well as make new, testable predictions. It is valuable to collect our present information under one umbrella, but if everything falls under that umbrella, it may as well not exist. String theory does not have predictive power (mostly because of energy scales mentioned elsewhere in this discussion, unless someone comes up with an ingenious way to probe its domain with low energy experiments), and its explanatory power is not very useful since it explains both reality and things out of reality, indiscriminately.
Everyone is free to pursue what they want. I did not comment on that at all. You click on whatever part of the tech tree you want. However, my expectation is that the string theory does not have the qualities of a scientific theory that improves one's knowledge about universe.
But we've discovered a number of useful tools and techniques that are applicable to other areas of research have we not? The billions of dollars spent on string theory hype might have unlocked a strategy or technique that ends up being useful in a civilization changing way that we just don't know about yet. Maybe string theory and the hype it was able to generate was just the catalyst that we needed.
Compared to all the other useless endeavors we send our brightest minds to work on (optimizing ad sales, high frequency trading, crypto) I'd say physics research has the highest chance of being useful
Physicist here. My PhD is in an area that was spawned into existence due to inspiration coming from string theory, not string theory proper.
I've made some comments here [1] to discuss how I see the situation. It's difficult to be thorought in the world of research, and even more so in an HN comment. I'll be writing more as the subject pops up in HN.
The legit criticism with a legit recommended change is even better.
A time and technological gap always exists between theory and a plan for experimental confirmation. Some gaps are fairly short. String theory's gap is undoubtedly long, not for lack of resources.
This gap justifies tapering the allocation of attention and research resources (funding, students, etc), which got lopsided following the strong marketing campaign driven by Greene.
I tend to agree. Science funding is unfortunately a limited resource, and I would like to see different approaches explored in more detail, which unfortunately would imply less (but not zero) funding to string theory. Not zero, because we also don’t want the competence built up in string theory groups to die out completely, in case that remains our best lead.
To borrow a compsci analogy, we tried the depth-first search going in the string theory direction, maybe it’s time to switch to breadth-first for a while, to see if there are any viable and useful theories with less distance from the ones we have today. Maybe it doesn’t have to be a "theory of everything" either, we can initially settle for a "theory of more".
I'm legit interested in hearing more about this, like YouTube series, popsci books, magazines - I've been meaning to read Zwiebach's A first course, but I keep getting distracted with background reading and then never get back to it.
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I don't entirely understand where that comes from. The Standard Model and General Relativity are both tested to extreme precision. Any experiment unifying them will have to involve insane energies. It's not as if there is some other model with easy tests that we've agreed to ignore.
As far as I can tell, it seems to come from the developers of Loop Quantum Gravity, who feel left out of funding. And maybe that's true. But their theory doesn't offer practical tests, either. It would be weird if it did.
> I don't entirely understand where that comes from. The Standard Model and General Relativity are both tested to extreme precision. Any experiment unifying them will have to involve insane energies. It's not as if there is some other model with easy tests that we've agreed to ignore.
You're absolutely right in everything you said, thank you.
Like another commenter posted, the planck scale is 10^19 GeV and we're about 10^15 short. Therefore it follows we won't be testing anything at planck scale for many generations, if ever. Therefore the argument of "I can't test it therefore the theory is useless" is just being defeatist. The fact that such theory isn't testable might be a feature of our Universe, not the theory. As in, these people don't normally make the distinction between something that "could be tested in principle, we just don't have the technology" (like string theory) vs something that "couldn't be tested even in principle" (like how many angels can dance on the head of a pin). They're basically playing with semantics when they say "it's not testable".
> As far as I can tell, it seems to come from the developers of Loop Quantum Gravity, who feel left out of funding. And maybe that's true. But their theory doesn't offer practical tests, either. It would be weird if it did.
Again, correct on all points. However, I'll add the following. Yes, LQG makes as many directly-testable predictions at the planck scale as string theory, which is to say none, because we don't have the technology to test anything directly at that scale.
I keep repeating these things on HNs, but people here fundamentally don't understand how research in theoretical physics is done. I'll try a little exposition:
Physics is: make experiments, and try to infer which laws/rules/formulas are common to all experiments or sets of similar experiments, and their domain of applicability. These are called theories.
Theoretical physics is: think about theories, and try to observe which laws/rules/formulas are common to all theories or sets of similar theories, and their domain of applicability. These are more general theories from which your directly-experimented theories can be derived. You can keep interacting constructing ever more general theories from an ever smaller set of principles.
So a lot of theoretical physics is about arguing which of the principles that you know are true because you've experimentally tested them will hold in circumstances where you can't directly test. As it turns out there's a lot that you can infer about things you've never seem because often times mathematics puts constraints on how different ideas work together.
The string theory/LQG thing is that LQG start from the guess that Lorentz invariance doesn't hold at planck scale. The reason why LQG is less appealing to a lot of physicists is that if you follow this through you can never quite make it mathematically self consistent. In string theory what happens in certain sub-domains is that you start with a lot of arbitrary possibilities, but then you demand certain types of mathematical self-consistency and magically it points out that there's only one or a small number possibilities. A classic example is: "how many dimensions does the universe has?" which no theory really gives as answer, but string theory at least points in a direction: "if you assume such and such, the the allowed answers are such and such". This happens a lot in string theory, and it's what drives people to keep digging. String theory on the other hand concludes that Lorentz invariance must hold at all scales "in some string-like theories" if you demand cancellation of divergences, which you must have for your theory to be renormalizable and therefore mathematically self-consistence. So in a sense this is a prediction of string theory. Not that LQG doesn't predict the opposite, that Lorentz invariance doesn't hold. Instead it assumes that it doesn't. String theory instead predicts that it does. The latter is much more impressive; anybody can start from an arbitrarily picked assumption that noone can prove wrong.
Perhaps you could elevate the discussion by providing an actual argument against this view of string theory, which has indeed percolated through social media?
For my part, I know a little bit more than "shit" about physics but I know very little about string theory and know better than to have strongly held opinions about things I don't understand. I've heard quite a lot about the criticisms and would like to hear a defense of it.
Ive been told my multiple High Energy Physicists that String Theory was suspect because it makes no predictions. Being able to make predictions that are testable is a foundation of theoretical science. Not everything is because of influences.
Eh... mainstream physics by numbers is not HEP and definitely not HEP Th, and there are plenty of serious physicists somewhat critical of the field, and more so of the way it presented itself over the last decades.
And while I disagree with some of the criticisms and some of the style of the crtics, it's not like you get an honest appraisal from Greene (and Witten).
i dont think it has anything to do with threats to way of life. It has everything to do with public subsidy of physics that has pushed peripherary mathematics forward without much to show for actual physics advancements. New observations cause changes to string theory not validation of string theory. String theorists can keep do*ng their string theory but its time to subsidize something(so else and see if that leads to actual advancement. I think sabbine hossenfelder is largely correct about this
Theoretical physics is subsidizing a handful of people sitting at white boards.
Even accepting the premise that string theory is wrong I can list hundreds of ways the US budget spews money down black holes orders of magnitude bigger. The spending on string theory isn’t even a rounding error compared to the way my tax dollars are allocated to special interest pork.
But only string theory impinges on a generation of cranks who are convinced they alone have the insight into the true ToE and would be recognized as the new Einstein were it not for some entrenched cabal. Maybe I shouldn’t reflexively trust “big science” or something but it’s also not great to evaluate science by who is more charismatically narcissistic on a podcast.
Again, I don’t have a big axe to grind on the merits here. But it’s hilarious that folks with zero science background past middle school hear some of these cranks on YouTube and feel worthy to decry Witten as an enemy of the people. Between the podcast bro who was just told his ToE was right by ChatGPT and Witten I’ll take Witten.
I know absolutely nothing about string theory, or the culture of high-energy physics, but I don't buy the pecuniary argument you are making. You aren't considering the downwind effects of allowing academic rot. The Bourbaki—and their acolytes—also sponged up only a tiny amount of academic funding, but a fever in the pulpit can spread out into the pews; we've seen the "New Math" paradigm damage a generation of primary-and-secondary-school students. Even today, we have issues with engineers not understanding that a derivative is a slope and an integral is an area—due in no small part to a cartel of bad actors in mathematical research. Allowing bad behavior in high-value and influential positions has consequences beyond a waste of government expenditure; a president could turn a democracy into a banana republic, and we would have issues beyond his salary of a few hundred thousand dollars being wasted.
How many primary school students can't add fractions because string theory may be a less promising approach to a ToE versus loop quantum gravity or geometric unity? I know nothing about this stuff. You know nothing about this stuff. Since we both do know about the Bourbaki school of mathematics despite having different opinions on the value of building mathematics upward from foundational principles I'd say we are in the top .5% of the planet re general mathematical/scientific literacy. So I don't buy that even if string theory is wrong there is some massive spillover effect.
No, its subsidizing a handful of people sitting at whiteboards at the expense of different camps of people sitting at whiteboards and the result is nefarious because you dont see what could have been if we minimized string theory funding after a decade or two of poor performance instead of going all in on it for five decades. We gave up decades of potentially actually figuring something new out by going harder on string theory instead of diversifying physics spend as performance failed to show up.
how the government wastes money elsewhere is irrelevant to the conversation. Its about proper management of research funding and how string theorists managed tp trick us into funding failure for whole academic careers.
Since I sadly must return to the real world (but thank you everyone for the well spirited debate) -- string theory is funny to me because its a bit of a Rorschach test as such a tiny number of people who follow the subject can actually evaluate string theory vs. alternative models. It's just an abstract blob people can project their worldview onto. To the extent someone reading this is in the group who does understand the topic, this isn't about you--
As a society we can't place excess faith in the orthodox positions of institutions. We all know they can be rigid, wrong, and lock out dissenting views. But society today seems to embrace heterodoxy for its own sake the way perhaps in the past orthodoxy was just accepted on pure faith and there is a vast media ecosystem happy to promote (ie monetize) this worldview. Just because something is heterodox doesn't make it right.
Again, I'll accept your premise for the sake of debate (which I welcome, and sincerely thank you for doing so respectfully).
Let me try to rephrase where I am coming from. I'm going to accept there is a good argument that some science funding should be redirected towards theoretical physicists pursuing alternate approaches.
1. The focus towards this matter in online media circles is vastly disproportionate to the relative impact this has on anyone's life compared to the multitude of other intra-silo disputes across the federal budget. It's not irrelevant to the conversation or at least my subsection of the conversation. It is interesting to me what debates burst through the noise and get traction outside of their own little world. Maybe 1% of the people debating string theory online actually understand a micro-fraction of this stuff. To be clear, I don't claim to be in that 1%. I'm interested in how that happened and the cultural+platform reasons for it. I'm interested in why alongside those genuinely interested in alternative approaches to theoretical physics this topic attracts tons of people who just lump it in with their "they are all lying to you" worldview. Nothing this obscure, incomprehensible, and yes irrelevant to most peoples lives should have organically reached such breakout status. I can ask some of the 22 year old bros at my jiu jitsu gym what they think of string theory and they will tell me it's all part of the omni-conspiracy. It's literally the only science thing they know. It's not like they understand a word of the debate or know of/care about a single other intra-discipline debate about the allocation of resources.
2. No small part of this is the unfortunate emergence of the online narcissist huckster and nothing plays better in online circles than "they" don't want you to know the truth that "I" have the true answer but "Big X" won't admit it. This clown show distracts from the real merits of the relative positions. But it does get the charismatic narcissist a slot on general interest "they are all always lying to you" podcasts.
3. Obviously this doesn't apply to legit physicists and good faith normies who simply disagree with the existing dogma. That's not who I'm talking about. That said, theoretical physics is bargain basement cheap. I don't need to build a supercollider the size of Mars. I don't need to sequence a trillion genomes. I need a laptop, a whiteboard, some time to think, and a bit of ancillary budget. Surely there are enough allied tech/crypto heterodox rich dudes at this point to fund a Center for Heterodox ToEs and staff it with 50 bright people to prove they have something to add. I can't pretend to have the chops to analyze Eric Weinstein's Geometric Unity vs String Theory. I do know if I really thought I had the answer to the universe and his bankroll/connections I'd just fund a real research effort to prove it vs. doing the podcast circuit ad infinitum.
If it is irrelevant to my life then it is easy, i shouldnt be funding it. I actually disagree. Physics progressing is very relevant to my life because physics progress drives huge positive societal change. That physics is stuck on string theory and that string theory has gotten us nowhere is why i dont have much cheaper energy, much faster computers, much faster travel, paradigm shifting medical options, etc. that a bunch of wankers captured a whole class of cuahy university job for whole careers has directly harmed me through lack of progress. I dont have to understand the theory to know whats going on. I only have to ser thr lack of progress for decades to know the right way to spend my money is to diversify until something moves forward.
Honestly that kind of straw man is about equally as grating as the "string theory critics" that watched 1 Sabine Hossenfelder video. And just as uninteresting.
People often say that the problem with string theory is that it doesn't make any prediction, but that's not quite right: the problem is that it can make almost any prediction you want it to make. It is really less of a "theory" in its own right and more of a mathematical framework for constructing theories.
One day some unusual observation will come along from somewhere, and that will be the loose end that allows someone to start pulling at the whole ball of yarn. Will this happen in our lifetimes? Unlikely, I think.
The problem is that once, a long time ago, String Theory was something that made concrete predictions that people just couldn't calculate.
Then people managed to calculate those predictions, and they were wrong. So the people working that theory up relaxed some constraints and tried again, and again, and again. So today it's that framework that you can use to write any theory you want.
That original theory was a good theory. Very compelling and just a small adjustment away from mainstream physics. The current framework is just not a good framework, it's incredibly hard to write any theory in it, understand what somebody else created, and calculate the predictions of the theories you create.
I am old enough to remember when string theory was expected to explain and unify all forces and predict everything. Sadly, it failed to deliver on that promise.
And there is no known single real world experiment that can rule out string theory while keeping general relativity and quantum mechanics intact.
More accurately, string theory is not wrong (because it just cannot be wrong). Because it does not predict anything and cannot invalidate anything, it does not help to advance our understanding of how to integrate general relativity and quantum mechanics.
It should not be called theory - maybe set of mathematical tools or whatever.
You can't really show it's wrong because there are dozens of different theories but using the Wikipedia definition "point-like particles of particle physics are replaced by one-dimensional objects called strings" it's possible that particles are not strings. I guess it would then be like fairies at the end of the garden theory. Good from a literary fiction point of view but not reality.
string boot framework
I was planning to make a similar comment. Conjecturing that some theory in the string theory landscape [0] gives a theory of quantum gravity consistent with experiments that are possible but beyond what humans may ever be capable of isn't as strong of a claim as it may first appear. The intuition I used to have was that string theory is making ridiculously specific claims about things that may remain always unobservable to humans. But the idea is not that experiments of unimaginable scale and complexity might reveal that the universe is made up of strings or something, it's just that it may turn out that string theory makes up such a rich and flexible family of theories that it could be tuned to the observed physics of some unimaginably advanced civilization. My impression is that string theory is not so flexible that its uninteresting though. There's some interesting theoretical work along these lines around exploring the swampland [1].
[0] https://en.wikipedia.org/wiki/String_theory_landscape
[1] https://en.wikipedia.org/wiki/Swampland_(physics)
Or, that day will never come, because string theory isn't reflective of the actual world, or because there are so many theories possible under the string theory rubric that we can never find the right one, or because the energies involved to see any effect are far beyond what could be reached in experiment.
It isn't completely implausible that a future civilisation could perform the experiments to gather that data, somehow; but it is hard to envisage how we do it here on Earth.
Your implicit point is a good one. Is it sensible to have a huge chunk of the entire theoretical physics community working endlessly on a theory that could well end up being basically useless? Probably not.
There is not a "huge chunk" of the theoretical physics community working on string theory, and their never was. For one, it is far less common a topic of research now then it was earlier when it was more popular, but even then "huge" was really "a lot of universities had a grant for string theory investigation because it looked promising".
It mostly hasn't worked out and now people are moving on to other things.
The single worst thing that happened though was the populism: a small group of people with credentials started putting out pop-sci books and doing interviews, well in excess of what their accomplishments should mean. People are like "so many people are working on this" because there were like, 3 to 5 guys who always said "yes" to an interview and talked authoritatively.
Huge is a subjective term, but go and count the number of participants at Strings 2025 [1]. Then realise that is just one of many conferences [2]. It's still a very big field.
[1] https://nyuad.shorthandstories.com/strings-conference-abu-dh...
[2] https://www.stringwiki.org/wiki/Conferences
A meaningless statement if you aren't going to introduce any points of comparison. But I would hardly call 735 conference participants a huge conference. Like, that's big but there are lot more then 735 theoretical physicists.
Claude tells me that there are about ~5000 theoretical high energy physicists actively publishing as tracked by INSPIRE-HEP (the de facto search engine in that field). If we estimate that about a third or half of string theorists take part in Strings in a given year -- because there are other big conferences like String Pheno that will be more relevant for many -- then we have something like 30-50% of high energy theorists working on string theory.
I agree that people should be "moving on to other things," but I'm not seeing the evidence that they actually are.
Are all the attendees of a Linux conference Linux developers? Are all the people who attend CCC penetration testers?
> the problem is that it can make almost any prediction you want it to make
In logic this is either the principle of "contradiction elimination" or a "vacuous truth". Depending on how you look at it. i.e. given sufficiently bad premises, you can prove anything.
> less of a "theory" in its own right and more of a mathematical framework for constructing theories.
so it's javascript?
A bit like LISP then ...
Theorists are real good at bending around experimental data, unusual or not
The Planck scale where string theory's distinctive physics should appear is around 10^19 GeV. The LHC operates at about 10^4 GeV. That's a factor of 10^15 which is a million billion times too weak. No foreseeable accelerator technology can bridge this gap. The proposed Future Circular Collider (FCC) would reach maybe 10^5 GeV. Still 14 orders of magnitude short.
So the grift can continue
Non-Euclidean geometry (geometric axioms in which one postulate is rejected such that the 3 angles of a triangle are not exactly 180 degrees) was considered a meaningless word game and fundamental mistruth.
Later, non-Euclidean geometry was actually essential to modern physics.
It's intellectually sketchy to judge future value by the present.
Might as well fund someone researching whether quantum theory run on little gnomes, if there is no serious path to verification after 50 years, why not quantum gnomes?
On this topic (parallel postulate), it took ~2000 years from Euclid and then 3 people all came to the same conclusion independently within ~10-20 years.
Progress is weird.
Is it so weird? See Multiple discovery https://en.wikipedia.org/wiki/Multiple_discovery and Zeitgeist https://en.wikipedia.org/wiki/Zeitgeist namely that there might, or might not, be objective knowledge out there describing properly an objective World but we as a specie do chip at it with itself over time. When a new discovery in any field is made it propagates through our social network and tools we have for it, e.g. cafes, scientific journal, Web. As soon as something is discovered most of us connected enough get the new tool or perspective, update our Worldview and chip it at it again. IMHO this way it seems pretty normal that things hitherto unknown, no matter for how long, become knowable to seemingly independent discovers.
Ideally, one should explore all possibilities. It is remarkable how far "merely" predicting the next word has taken us.
That was constant progress with measurable goals, not "big things are coming decade from now" every decade.
> We should stop funding research into prime numbers. They're stupid and useless. Who cares about them, if they will never be used for anything? Number theory should be stopped, you may as well research gnomes.
I imagine this is what you would have sounded like 100 years ago.
You may be understating how much 15 orders of magnitude are.
The only truly exponential technological progress we’ve ever had, transistors, only scaled by ~5 orders of magnitude in feature size. Thermal engines went from maybe 0.1% to ~50%, less than 3 orders of magnitude, in about 200 years. There’s very fundamental physical laws that suggest that engines are done, and transistor scaling as we have known it for 30 years is also done. Perhaps very clever things might give us 5 more orders of magnitude? E.g. truly 3D integration somehow? Then we’re still 5 orders of magnitude off from our target. I can’t think of any technology that ever improved by more than 10^6, perhaps 10^9 if you count some derivative number (like “number of transistors on chip”, rather than actual size), and that’s from literally zero to today. Not from already-pretty-advanced to Death Star scale.
Another perspective is that, to get to those kinetic energies, we need accelerators as large as the solar system. Possibly the galaxy, I can’t quite remember. Will you concede that galaxy-wide objects are so far from current reality that there’s no point seriously talking about them?
Are you seriously insinuating that string physics are asking for this collider you alone entirely made up? As if people who actually do study string theory are too stupid to know primary school math and this criticism is somehow high-brow and novel?
Not to mention you entirely missed the point of what I said. There is research into the most niche, useless fields imaginable, because not every endeavor taken by every human being needs to be profitable or applicable. Sometimes people are just really good at making jigsaws or want to make a stinky chemical or get fascinated with properties of prime numbers.
And then, sometimes, those turn out to be the fundamental underpinnings of an entire generation of economic and military strategy. You can't often know what spurs what in that sense.
I didn’t make it up, it’s a well known talking point around string theory. I think it was first mentioned by a practicing string theorist. Of course it’s not a novel critique, but I’ve read about putting data centers in space on this website, so I think it’s worth trying to teach people how to do these sort of Fermi problems quickly.
I did indeed miss your point, it was well hidden under a lot of sarcasm. I think it is of course completely valid. People should be free to research what they want, and I’m sure string theory must be beautiful mathematics.
But if your goal is unifying QM and GR, and/or achieving a theory of everything (as is for most theoretical physicists), then me and a growing fraction of physicists think that it’s not a promising avenue. I’m not advocating for only working on “useful” things, because such a theory is not likely to yield much profit to anyone in the foreseeable future anyway. But if you state that a unifying theory is your goal and seek funding for that goal, then string theory should move to the backstage. The mathematics department would rightfully be happy to house you otherwise.
>Non-Euclidean geometry (geometric axioms in which one postulate is rejected such that the 3 angles of a triangle are not exactly 180 degrees) was considered a meaningless word game and fundamental mistruth.
This is just a lie though. Non-Euclidean geometry is a mathematical model of how distances behave on non-linear spaces. Nobody ever believed it to be a "fundamental mistruth", even suggesting it would look ridiculous. It would be akin to denying linear algebra, even the meaning is unclear.
That the physical reality of space is not linear was a shocking revelation, since all human experience and basically every experiment done up until that point indicated otherwise.
This is a generally known part of the history of mathematics.
> Nobody ever believed it to be a "fundamental mistruth"
https://math.libretexts.org/Courses/College_of_the_Canyons/M...
"Lobachevsky [mathematician contemporary of Gauss, who claimed parallel postulate was unnecessary] was relentlessly criticized, mocked, and rejected by the academic world. His new “imaginary” geometry represented the “shamelessness of false new inventions”"
Further, many claimed premature success in finding logical contridictions in geometry lacking parallel (Euclid's 5th) postulate; which meant they believed a 4-postulate geometry to be fundamentally false.
you are mixing up gambling spend vs whole industry spend. If string theory was a small handful of people making up a small m*nority of physics departments like non-euclidea geometry research was that would be fine. Its huge swaths of most physics departments and a huge suck on research funding. For that kind of spend you better show results because you are in production phase at that point not lotto ticket moonshit phase. If we are buying lotto tickets with the money bey lots of different lotto tickets not a whole bunch of one lotto ticket
I think you are vastly overestimating the number of string physicists and how much their non-experimental research costs.
There's maybe a couple or few hundred-ish in the whole world that focus on it. And they don't need much money because it's pretty much all math.
As a percentage of theoretical physicists it is probably significant though. A Better question is how much love/money/attention is going into rival theories ?
It is basically this. People arguing for string theory have no concept of how to maximize return with uncertainty. The thing had 50 years of substantial funding and substantial mindshare and pushed us nowhere. Any rational person with basic risk understanding would know at this point its a fail and we are in the not knowing what to pursue phase so we should be supporting small investments in dicerse options &ntil something promising happens then we can concentrate funding there &ntil that times out or gices us the understanding to achieve something new and great. The lifecycle of increasingly aupporting string theory s=ould have turned 2 to 3 decades ago instead of just recently. We lost atleast 20 and more like 30 years of progress we didnt have because a bunch of very smart people captured the physics funding aparatus to enrich thselves.
> m*nority
Is this a typo? I see a lot of words being censored these days and I assumed it's because of some algorithms and visibility. That shouldn't be the case here tho..
Its a spelling mistake from responding from my phone because my life is busy...
They do the same thing with the i in “doing” in another post. It seems like just a typo this person sometimes makes.
I imagine that elliptic geometry had some use before modern physics.
Yeah, even just trying chart a course on a ship across a reasonable distance will cause you to need to reevaluate some "obvious" things (like "what path is the shortest between these two ports" being a curve rather than a line).
The specific controversy was whether without the parallel/5th postulate, there existed a logical contradiction, i.e. proving the parallel postulate
In the 1700s, perhaps. But we have come a long way since that.
Yet, OP is repeating the same logical fallacy: the absence of a result is not a result of absence.
Planck energy: ~10^19 GeV is approx 2 GJ per collision
Energy to vaporize Earth's oceans: ~4 x 10^27 J
For a Planck-scale linear collider at LHC-like collision rates (~10^8/sec):
Beam power requirement: ~2 x 10^17 W
With realistic wall-plug efficiency of ~1%: ~2 x 10^19 W
Annual energy consumption: ~6 x 10^26 J
At 1% efficiency, one year of operation would:
Vaporize about 15% of Earth's oceans
Or vaporize the Mediterranean Sea roughly 50 times
Or boil Lake Superior every 5 hours
Or one complete ocean vaporization every 6-7 years of operation
It's about 1 million times current global power consumption
Or about 50,000 Suns running continuously
Or 170 billion Large Hadron Colliders operating simultaneously
Or about 50,000 Suns running continuously
I seriously read that and first thought it was a dig at SPARC chips running hot ...
I thought Brian Greene did a great job interviewing Edward Witten (Fields Medal winner) on the World Science Festival Youtube channel [1].
I also just really enjoy Brian Greene, his books, and the World Science Festival Youtube channel.
[1] https://www.youtube.com/watch?v=sAbP0magTVY
You might not like Angela Collier's video on string theory[1].
[1]: https://m.youtube.com/watch?v=kya_LXa_y1E
Thanks for posting that; as soon as I saw the title here I was going to look that up if no one else had already. Sabine Hossenfelder too, though there's far too much content from her on this to put a list, but anyone interested might like some of her takes.
A few debates between Brian and other notables; Hossenfelder, Eric Weinstein, and Roger Penrose to name a few; have popped up in my youtube feed lately which are typically also engaging.
Hossenfelder is not really comparable to Collier. Collier's video is critical of string theory as a testable framework but she ultimately still supports people who do research in string theory. Most of her criticism is with media coverage of string theory, not the research or the researchers.
Hossenfelder has gone off the "the physics establishment is all idiots and they are suppressing the real physics" deep end and has converted specific complaints into trashing the entire field.
I'm not a fan of Hossenfelder, especially for casting quacks like Weinstein, but AFAICT she isn't about "suppressing the real physics" but more of a "establishment physics is wasting money and time, and a lot is equally bad/good as some alternative physics."
I think here more recent takes are not nearly as nuanced.
She proves my theory that people who are successful on social media will lose their minds over time. It’s too easy to fall into the contrarian or cheerleading trap because there is too much money and fame in it. Being nuanced is boring and doesn’t sell
A year ago that might have been the case. Her more recent stuff is fairly dire. I believe that the algorithm encourages her and channels like hers to become more and more conspiratorial and less and less nuanced.
Yeah I think most of what (negative) people attribute to her is mostly her being hopelessly German.
Most, but not all
Don't agree, she spreads misinformation, she's disrespectful to other scientists and basically has resorted to just claiming that everything in academics is wrong. YouTube fame has completely radicalized her.
I am German and I don’t think so. She is just another influencer who is living in her little social media bubble.
Collier made a video fairly recently where she showed disappointment that her videos are watched by people who also watch Hossenfelder.
https://youtu.be/miJbW3i9qQc
> Most of her criticism is with media coverage of string theory, not the research or the researchers.
I pretty strongly disagree with that categorization of Collier's video, as it makes it sound like string theorists were innocent bystanders and "the big bad media" just ran overboard.
I think she puts the blame squarely on string theorists (e.g. "celebrity string theorists who wrote all these books") as constantly hyping up the field with promises of "in a decade it will be amazing" - a phrase she uses to great dramatic effect throughout the video - despite never acknowledging the fact that it fails miserably at making testable predictions.
When she says "they lied to us", the "they" she's clearly talking about are specific researchers in the field (which she names), and the string research community more broadly, who are hyping up their field, not just "the media".
I thought her rant about bullshit papers was pretty convincing and poignant.
The problem with sabine is that she's become the worst person to make a correct point for the wrong reasons
If you do research it becomes pretty apparent that a high number papers are not great. There's varying issues, but a big one is that the funding model incentivises pumping out papers which are often of low quality, researching whatever happens to be in vogue at the moment
Literally everyone I've ever talked to in research as a frank conversation knows that this is a massive problem, but nobody wants to talk about it publicly. Research funding is already completely screwed as it is, and researchers are incredibly aware of how fragile their livelihoods are
Its clearly leading to a big reduction in the quality of the literature. I went on a replication spree recently and found that a pretty decent chunk of the field I was working in was completely unreplicable by me, with a few papers that I strongly suspect 'massaged' their results for various reasons
I wish someone would talk about this who wasn't also in bed with right wing grifters, and was actually credible. We need someone more like ben goldacre for physics
Sabine's most interesting content is the paper reviews, and where she sticks to actually examining the evidence - but it makes up a tiny fraction of what she produces these days, and her support for some truly grim figures is just gross
Your paragraphs two, three and four are exactly what Sabine is communicating. So much so that it almost sounds like you pulled a transcript from one of her videos.
I don't think you're describing "the" problem with Sabine. She's not what you want her to be but that's a you problem. You're describing your particular problem with Sabine.
I appreciate that she's doing a lot to bring attention to the real issue despite your claim that she is supporting grim figures. I know about the problem because of her work, but I have no idea who Ben goldacre is.
Also no idea what you mean by supporting grim figures. I checked to see if she has come out in support of Jeffrey Epstein or something crazy like that, but no.
> I checked to see if she has come out in support of Jeffrey Epstein or something crazy like that, but no.
Bro she blurbed "The War on Science," a book stuffed with racists and sex pests complaining that they lost their jobs for falling in love with their graduate students, writing them love poetry on tumblr, and then kicking them out of their research group because they could stand to be near them. Or for saying that they "don't shy away from the word superior" when discussing white people being better at running societies and lying about the GPAs of black students. Or for taking joking photographs with human remains.
And yes, the authors of the book include people who provided support in the legal defense of jeffrey epstein.
Yep, this exactly. Its completely unacceptable
And its not something that's just a 'you' problem - if you want the actual underlying issues in physics to be fixed, its a massive issue that the spokesperson for fixing those problem currently may be a bigot, or at the very least endorses bigots and sex pests. Beyond just being generally completely unacceptable, it allows everyone to completely dismiss whatever is being said very easily
For the other poster, ben goldacre is someone that's become very well known for making effectively the same points as sabine, but within the pharmaceutical industry. They sat down and basically wrote for decades about how the testing was absolutely broken, multiple books, a column, and producing lots of work on how broken studies were in medicine and talking to anyone that would listen - and as a result, they were actual able to enact effective change. It was a huge win for evidence based science!
Sabine is not someone who can achieve that in physics - her videos would be much more effective if they contained actionable content and concrete analyses of the issues. I'd have a tonne of respect for her if what she did was publish papers or videos showing the degree to which the literature was broken, analysing funding, conducting interviews (even if anonymous) with researchers, looking through examples of bad papers and explaining the problems to a lay audience. Producing a mixture of for-scientist and for-lay person material to break the figures down, in a way that produces a compelling argument
Instead we at best get specific examples plucked out of the air. I know she isn't massively overgeneralising the issue from my own personal experience, but she presents a terribly uncompelling argument as to why there are problems. Where's the data? Why are you writing book blurbs for sex offenders instead of writing papers?
That's why I've come around increasingly to the idea that she's a grifter, even though I used to enjoy her content (before it went out of the window) and think that she does likely genuinely care about the underlying problem to some degree. Its closer to ragebait than anything that feels productive now unfortunately. I don't think its even necessarily on purpose on her end - the right wing has a way of sucking in anyone on the fringes and giving them a home even without them knowing, but also why give her the benefit of the doubt?
If I understood this, you agree with Sabine, but since she's "in bed with right wing grifters" she should not be listened to?
This is not very persuasive.
I agree with a part of Sabine's overall output, but she's increasingly misidentifying some of the problems and the solutions because she's drifted too far towards the grifters
To a large degree if you're trying to successfully trying to push for change, it really matters that the person pushing for it is credible. Someone like ben goldacre is able to credibly make a strong push for change within medicine because they've maintained credibility, someone like sabine makes the situation worse because they've chucked it away
Maybe it's like this:
Sabine's has a day job as a Youtuber, and she makes her videos from that perspective. She speaks her mind, makes a decent living, and educates some science nerds on the way. Seems pretty nice.
From the perspective of accomplishing institutional change in the academic physics world, this is does nothing. The institutional powers don't react at all to a complaining influencer with an Einstein doll.
And I suspect she's perfectly fine with that. Overturning the Physics establishment is a near impossible task. I would leave that for those mad enough to try.
_totally_ off topic, but what sort of brain must Ms Collier have that she can play a game at the same time as giving a cogent lecture on String Theory with very few hesitations? I could hardly concentrate on the lecture because of the game being shown in an inset window. Truly impressive
Yesss! I had an ex complain/advise that, if I could just stop thinking for a moment, I'd enjoy life more. In my mind, that's what Ms. Collier is doing: distracting her hyperresponsive brain parts so she can present a longer speech on the topic.
Interesting, thanks for sharing!
I definitely don't walk away from any of Brian Greene's content thinking that String Theory is anything close to a confirmed fact at all.
It's been some times since I read his earlier books, possibly his tone has changed?
I'll also say, I'm far from a professional physicist. I'm reading and watching for fun and intellectual curiosity, not to learn physics with the goal of doing my own research. I always thought of String Theory as being more of a study of math where many people have unsuccessfully tried to apply it to physics. And, that it's lead to some really interesting ideas. I just find him and his work really enjoyable.
> It's been some times since I read his earlier books, possibly his tone has changed?
I think her point is more that his tone hasn't changed. If you're curious I would just watch the video. Angela comes with the perspective of also having read his earlier books and having liked them.
The OP is about that video, though one wouldn't know it from a web page that won't download. I've put an archive.org link in the toptext now.
I have a PhD in high energy theoretical physics (hep-th for short) and I've written a paper on string theory, so I'd like to comment on some things:
1. I think there are two reasons why string theory is cool (other people may have different opinions). Please note that none of these two reasons are directly related to the extension of Standard Model. 1.1. String theory is the only theory so far that can mix gravity and quantum mechanics, and it can be even used to derive Hawking entropy of a black hole from "first principles" (see paper by Strominger and Vafa). The obvious trouble is that the black hole in question lives in five-dimensional space and is unrelated to the real-world black holes, but this is way better than what one can get from Standard Model physics (which is, no gravitons for you).
1.2. Through AdS/CFT correspondence, string theory can be used to describe quantum field theories that are not related to string theory by themselves. This gives a very strong tool to study these quantum field theories, and the paper by Maldacena that discovered this correspondence is one of the most important papers in the field.
2. It is true string theory is unusable as of now to derive the Standard Model physics (and provide extensions for it). Unfortunately, I would say that hardly any papers in high energy _theoretical_ physics currently address Standard Model physics. Roughly speaking, in late 1970s, after quantum chromodynamics was established and the asymptotic freedom was discovered, it turned out that it is extremely hard to compute many things we are generally interested in. At this point, high energy theoretical physics split in two sub-areas: phenomenology (which tries to extend the Standard Model to derive things like neutrino mass) and theory (which is a more formal theory and tries to answer questions like "how to quantize gravity"). One can argue that this makes hep-th an area of mathematics, and I would agree with that (eg in Cambridge theoretical physicists are in the same department with applied mathematicians).
2.1. The things theoretical physicists study tend to pop up in various places, even if the original motivation is misplaced. Even the string theory itself originated as a way to explain the Regge trajectories (which were explained with quantum chromodynaics afterwards), and not to quantize gravity. For a more practical example, Witten introduced topological quantum field theories long before anyone understood how to apply them to real-world physics.
3. I do not agree that string theory dominates the hep-th field. I would say that its popularity changes with the time, going up and down. While the main conference in the hep-th field is called "Strings", the talks at it are not necessarily related to strings theory, and at the 2025 conference I'd say that only 1/3 of the talks were anyhow related to the strings theory. Moreover, there is no hard division between people working on string theory and people working on other hep-th subjects, so that e.g. Witten made many contributions to hep-th which are not anyhow related to string theory.
3.1. As for the push to do string theory that eg Sabine Hossenfelder alludes to, I'd say that I experienced no such push during my MSc and PhD studies. I've written four papers, and worked on a couple of projects that did not become a paper, and out of those, only one was dedicated to string theory.
3.2. On the other hand, the more fringe theories that can provide alternative to string theory are also more high-risk endeavors (as you are quite likely to fail to produce anything coherent within a typical timeframe you allot to write a paper). Hep-th is strongly underfunded, and I believe, that with greater funding (and less need to publish-or-perish) some people would also pursue the more fringe directions in hep-th.
3.3. A comment on the naming: hep-th is a field which is very hard to name. The name I use is the traditional one (and is used as eg a name for the field on arXiv). However, many things derived by the physicists in the field are not anyhow related to the high energy in the literal meaning of the words "high energy". When talking to people at a party, I say that I studied string theory, because the name is catchy and it rings a bell, but this way of referring to the field is definitely a misnomer.
Thanks for the comment that exposes the nuances. As a non physicist who is interested in physics, I would say that the predicament is that we simply don't have enough data to tell how to improve our physics theory, but we have too many physicist working in the field, so ideas just get staled.
Is that a correct assessment?
Not exactly, I'd put it as follows: 1. In phenomenology (the science that looks into extending Standard Model) we'd definitely benefit from more data (with most viable data sources, in my opinion, being not the colliders but the detectors of extraterrestrial particles such as PandaX or Fermi-LAT). However, this doesn't stop us from getting new results, narrowing the window of possibilities for the properties of the Standard Model extensions. This "sorting a haystack in search of a needle" approach may not sound too cool, but this is exactly how we discovered the Higgs boson, for which we looked for more than twenty years. 2. In hep-th we currently lack either enough data (which we can't really collect now), or an ideological breakthrough in solving one of the hard problems. Unfortunately, the problems are indeed very hard, so that one of them (Yang-Mills existence) is a Millenium Prize problem. This caused the de-facto shift of hep-th into applied math, so now hep-th is not constrained by the data problem, and is developing as actively as an area of applied math can.
Here is my question to string theorists: suppose some physicists came up with an alternative theory of everything and were able to use it to make unique empirical predictions. Would you accept it as true and abandon string theory?
What experiment(s) would we have to run to see deviations from the Standard Model and be able to come up with newer models (maybe String Theory maybe not)?
Is it just about higher energy particle collisions? Or does it involve things like doing experiments next to a black hole?
we already have experimental data for deviations from the standard model: neutrino mass for example
or dark matter
String theory has always seemed intuitively wrong to me. From Wikipedia:
>In theories of particle physics based on string theory, the characteristic length scale of strings is assumed to be on the order of the Planck length, or 10E−35 meters
Yet electrons repel each other over distances of many meters by I think the virtual exchange of photons. How on earth would that work? How does your photo string know to head to an electron string trillions and trillions of times it's length away?
As far as I can tell the field became popular for sociological reasons that you could get grants for it and the like rather than any connection to reality(?)
You're being somewhat unfairly voted down, it's a legitimate questions because the popular media so grossly misrepresents what string theory is, especially in their visuals.
It's hard to visualise in 3D, but if you cut down the spatial dimensions to just 1D (a line), then theories like string theory just turn the infinitely thin mathematical line into a tube. You can picture a tube that vibrates, or has waves in its cross-section. Don't think of the the "strings" as actual little loops moving around in space, they're a modification of what space is.
You can even do the same kind of line->tube extension of a space with even more extra "loop" dimensions than the number of base dimensions. AFAIK the current theories have 10 total, of which 3 are the usual "large" dimensions of space, the rest are "small" and rolled up like the tube example.
Even so I don't get how electrons a meter apart interact through that stuff, as opposed to the electrical fields which spread out through space and so interact with other electrons as featured in quantum field theory which is what physicists use to actually calculate physical results, as opposed to string theory which fails to calculate actual physical results.
"if you cut down the spatial dimensions to just 1D" doesn't sound very physical to me.
I'm maybe being downvoted fairly. I studied physics and it don't think it's a misunderstanding of popularisation or that string theory is untestable, I just think it's straight wrong and not how the physical universe works.
> Even so I don't get how electrons a meter apart interact through that stuff
Very roughly: It's possible for point-like (or tiny looped) particles to interact as long as they take every possible path instead of just the one path that would cause a collision. How you interpret this is... up for debate. I prefer the many-world interpretation (MWI), but not everyone agrees.
> "if you cut down the spatial dimensions to just 1D" doesn't sound very physical to me
That's just a simplification to aid understanding, it's now how the theory actually works.
Yeah maybe. My flatmate of some years was doing a PhD in string theory at UT Austin along the lines of "if you cut down the spatial dimensions to just 1D" but he was a mathematician, not really a physicist and was ok with that if it produced interesting mathematics. For real physical things like wiring the lighting system I'd do it because he wasn't so good with that.
I think he went into string research because he was good at maths and there was grant money available for that rather than a deep belief that that was the nature of reality, which is kind of what I mean by sociological factors.
I think much string theory may be like that. Interesting maths but not good at figuring where electrons go.
Except this is how electrons actually go, and it has real testable consequences. The question I'm aware of (because it related to my degree in nanotechnology) was: are metals conductive at different dimensionalities?
Because at the nanoscale, you in fact can have 1D, 2D and 3D metals. 3D metals are bulk solids - like we're familiar with. 2D metals are planes of single (or very few) atoms. 1D metals are lines - think placing individual metal atoms down in a row - nanotubes are a practical example.
All real, possible structures to build.
When you do measurements on all these structures you get...weird answers. Like is a nanotube a superconductor? And the answer is...yes, but also no. Yes because you'll in fact view superconductivity like behavior, but no because actually it's a ballistic electron conductor - at the right energy level an electron bounces through the thing without hitting it, but not all electrons can do that at all energy levels, so you still measure a voltage across a nanotube between two conductors.
But a nanotube is 1D - we only have 1 dimension things move in (from one end to the other). So - conductive, not a superconductor, but you can kind of use it like one sometimes. And we know 3D metals are conductors - that's obvious right...so what are 2D metals? Presumably conductors right...?
And the answer is...nope, insulators - at least sometimes. And the reason is because the sum of all possible electron paths in a 2D metal is the electron always returns back to where it started - and those grow much faster mathematically then paths where the electron ends up somewhere else.
But only in 2D: in the 1D case most paths take you out of the conductor. And in the 3D case, the number of paths which land you somewhere else grows much faster then those which loop back, due to the extra dimension of freedom. But 2D metals are constrained - for any given path elsewhere, there are mathematically far more that land back where you started. This is observable, measurable behavior which is a topic of research for future semiconductors. Yet it's almost entirely quantum probability based behavior.
I think the 1D mentioned in jiggawatts comment is a different thing to a confining electrons to a nanotube type of setup.
The string theory model is structured from the start to reproduce existing theories as a consequence, so the problem here is a lack of understanding on your part rather than a mistake in the theory. I do suspect that most people who are working on this stuff (or any stuff for that matter) don't think very hard about the basic phenomenological claims to the point where they can explain them well.
In particular your model of electric fields isn't very good. An electric field's flux around a volume reveals the presence of a particle in that volume. That's not because the field, a bunch of vectors in space, "happens" to integrate to something nonzero if there's a particle in that volume: it's because in some sense the presence of a field with a nonzero flux and the presence of a charged particle are the same thing; the particle is the existence of a divergence in the field within that volume.
Moreover in QFT (and this part is handwavey as I only learned enough to vaguely understand this, but it's better than nothing) the presence of the "field" ends up looking like the sum of what you get if you integrate over every possible way of a emitting or receiving a photon at that point; the accumulated integrals destructively interfere in such a way as to produce a value which reflects where the particles are. So very roughly idea of a field existing at a point and having a "value" is like saying: there are a bunch of things out there that I (a charged particle) can detect by exchanging photons, and the accumulated effect, when you consider all the different quantum superpositions of ways of doing that, is a single vector which induces a force on me. Other fields add up to more complicated objects than vectors.
Once you look at things like that, there should be no objection to how strings and electrons might interact. Whatever's going on at that string level averages out over larger timespans to just look like electron field. Not dissimilar from how all the individual charges in an atom average out to look like a single charge (but are perhaps detectable if you get up really close, in dipole and higher moments, or in how the atom deforms / reacts to nearby charges).
It might help to be aware of the concept of a topological defect (https://en.wikipedia.org/wiki/Topological_defect; there's a great explainer article somewhere that I can't seem to find) as a reductive picture of what a particle "is". I've heard this doesn't work for fermions for some technical reason, but in any case it's very useful as an illustration of the sort of thing that a particle "can be": a vortex in a material can act like a particle and even exhibit attractive/repulsive forces. So I picture the string theory model as answering the question: what kind of substrate could produce vortexes and other "defects" that act like the particles we see? Dunno if that's accurate but it seems like a natural question to me, anyway.
I can definitely buy a lack of understanding on my part - my understanding of all this is quite fuzzy. But I'm not sure string theories reproduce existing theories so much a say this is compatible with the other stuff in a handwavy way? I don't think there's any "we assume strings and thus can deduce quantum mechanics and general relativity" stuff? I don't think anyone can deduce quantum mechanics and Einstein's deductions with relativity are based on simple observations like the speed of light being observed to be constant and acceleration seeming similar to gravity?
It's not "we assume strings and deduce QM" it's "strings are a model which is defined so as to produce QM and also...". It is, by design, a theory of QM and GR. That's the point. It's a claim about what lies "below" the level of the individual fields in QFT which gives rise to them (and also gravity).
whether or not string theory is at this point grifty and weird, the theoretical basis for it is far stronger than you would think based only on reading critics / pop sci explainers. It is not like, missing any obvious physical facts in its foundation. Rather it is trying to say: look, we have this zoo of particles with seemingly random masses and properties; is there same lower-level framework which can produce the zoo that we see according to a simpler list of rules? The obvious choice for this, especially given some of the "hierarchies" of particles that are observed, is that they are in some way resonant modes of some kind of underlying object. Which is where you get the strings from. (Which might sound like a weird justification if you are not aware of all the other aspects of physics which get explained as resonances of fields; this is a standard sort of justification which there's a lot of good reasons to be interested in, at least initially.)
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Wasting two generations of some of the most brilliant physics minds isn’t exactly a good thing
What would Imre Lakatos say? Is it degenerating or not?
30 years ago in college, at a physics club talk, I got my first intro to string theory. I didn't understand it but was intrigued enough to go to a small one-off seminar led by Prof. Greene. About 15 people around a table while he spoke. I kept thinking I was too ignorant of the subject matter to be able to ask a question. But nobody asked any questions.
I wonder what Ed Witten would have accomplished if he had gone into another field instead of choosing to dedicate his life to mathematical physics.
Not sure if you're making a joke about this, but Ed Witten tried a number of fields before settling on theoretical physics.
You reminded me about this Abstruse Goose comic: https://web.archive.org/web/20230202225744/https://abstruseg...
M for Magic
An in half a century we still haven't found a single actually testable prediction.
I think that's not quite right: it is reasonably certain that string theory can produce both the standard model and most extensions people have dreamt up, so the problem is rather that all the obviously "stringy" predictions are currently unavailable, while the string theory derived predictions for achievable experiments look like what we get from other theories we already have.
To make this valuable, it should produce a limited set including standard model. If you produce pretty much everything one can dream of, that does not carry predictive power.
What does string theory predict that (1) is within experimental reach in, say, 5 years (2) if not found, would prove it wrong. Was there ever anything satisfying these two simultaneously? AFAIK,the answer is "no".
You write this as though reality is a 4X game and we're obviously wasting time not clicking on the other item in the tech tree to optimize the build.
No, I am simply stating what is expected of a good scientific theory in physics. Such a theory should have power to explain things as well as make new, testable predictions. It is valuable to collect our present information under one umbrella, but if everything falls under that umbrella, it may as well not exist. String theory does not have predictive power (mostly because of energy scales mentioned elsewhere in this discussion, unless someone comes up with an ingenious way to probe its domain with low energy experiments), and its explanatory power is not very useful since it explains both reality and things out of reality, indiscriminately.
Everyone is free to pursue what they want. I did not comment on that at all. You click on whatever part of the tech tree you want. However, my expectation is that the string theory does not have the qualities of a scientific theory that improves one's knowledge about universe.
Making a hard, arbitrary deadline is a pretty extreme thing to do. ie Higgs Boson was a lot longer between theory and experiment than this.
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But we've discovered a number of useful tools and techniques that are applicable to other areas of research have we not? The billions of dollars spent on string theory hype might have unlocked a strategy or technique that ends up being useful in a civilization changing way that we just don't know about yet. Maybe string theory and the hype it was able to generate was just the catalyst that we needed.
what didn't se develop because those people were working on string theory? That is an unanswerable question. It is also the important question.
Compared to all the other useless endeavors we send our brightest minds to work on (optimizing ad sales, high frequency trading, crypto) I'd say physics research has the highest chance of being useful
Hasn't ChatGPT solved string theory yet?
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Physicist here. Would you like to enrich our world view by linking to counter-examples?
My understanding was that string theory being more "hypothetical physics" than "theoretical physics" at this point is still a pretty legit criticism.
Physicist here. My PhD is in an area that was spawned into existence due to inspiration coming from string theory, not string theory proper.
I've made some comments here [1] to discuss how I see the situation. It's difficult to be thorought in the world of research, and even more so in an HN comment. I'll be writing more as the subject pops up in HN.
[1] https://news.ycombinator.com/item?id=46336655
The legit criticism with a legit recommended change is even better.
A time and technological gap always exists between theory and a plan for experimental confirmation. Some gaps are fairly short. String theory's gap is undoubtedly long, not for lack of resources.
This gap justifies tapering the allocation of attention and research resources (funding, students, etc), which got lopsided following the strong marketing campaign driven by Greene.
I tend to agree. Science funding is unfortunately a limited resource, and I would like to see different approaches explored in more detail, which unfortunately would imply less (but not zero) funding to string theory. Not zero, because we also don’t want the competence built up in string theory groups to die out completely, in case that remains our best lead.
To borrow a compsci analogy, we tried the depth-first search going in the string theory direction, maybe it’s time to switch to breadth-first for a while, to see if there are any viable and useful theories with less distance from the ones we have today. Maybe it doesn’t have to be a "theory of everything" either, we can initially settle for a "theory of more".
I'm legit interested in hearing more about this, like YouTube series, popsci books, magazines - I've been meaning to read Zwiebach's A first course, but I keep getting distracted with background reading and then never get back to it.
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Wow their comment history isn’t much better, is there downside or anything that repeat low-value commenters face?
I've had dang on my case, threatening to ban me if I kept it up.
Rather than inb4, you'll make a stronger case by rebutting any of those comments you see come up in the thread.
Not really a rebuttal, but a discussion of how I see the situation: https://news.ycombinator.com/item?id=46336655
I don't entirely understand where that comes from. The Standard Model and General Relativity are both tested to extreme precision. Any experiment unifying them will have to involve insane energies. It's not as if there is some other model with easy tests that we've agreed to ignore.
As far as I can tell, it seems to come from the developers of Loop Quantum Gravity, who feel left out of funding. And maybe that's true. But their theory doesn't offer practical tests, either. It would be weird if it did.
> I don't entirely understand where that comes from. The Standard Model and General Relativity are both tested to extreme precision. Any experiment unifying them will have to involve insane energies. It's not as if there is some other model with easy tests that we've agreed to ignore.
You're absolutely right in everything you said, thank you.
Like another commenter posted, the planck scale is 10^19 GeV and we're about 10^15 short. Therefore it follows we won't be testing anything at planck scale for many generations, if ever. Therefore the argument of "I can't test it therefore the theory is useless" is just being defeatist. The fact that such theory isn't testable might be a feature of our Universe, not the theory. As in, these people don't normally make the distinction between something that "could be tested in principle, we just don't have the technology" (like string theory) vs something that "couldn't be tested even in principle" (like how many angels can dance on the head of a pin). They're basically playing with semantics when they say "it's not testable".
> As far as I can tell, it seems to come from the developers of Loop Quantum Gravity, who feel left out of funding. And maybe that's true. But their theory doesn't offer practical tests, either. It would be weird if it did.
Again, correct on all points. However, I'll add the following. Yes, LQG makes as many directly-testable predictions at the planck scale as string theory, which is to say none, because we don't have the technology to test anything directly at that scale.
I keep repeating these things on HNs, but people here fundamentally don't understand how research in theoretical physics is done. I'll try a little exposition:
Physics is: make experiments, and try to infer which laws/rules/formulas are common to all experiments or sets of similar experiments, and their domain of applicability. These are called theories.
Theoretical physics is: think about theories, and try to observe which laws/rules/formulas are common to all theories or sets of similar theories, and their domain of applicability. These are more general theories from which your directly-experimented theories can be derived. You can keep interacting constructing ever more general theories from an ever smaller set of principles.
So a lot of theoretical physics is about arguing which of the principles that you know are true because you've experimentally tested them will hold in circumstances where you can't directly test. As it turns out there's a lot that you can infer about things you've never seem because often times mathematics puts constraints on how different ideas work together.
The string theory/LQG thing is that LQG start from the guess that Lorentz invariance doesn't hold at planck scale. The reason why LQG is less appealing to a lot of physicists is that if you follow this through you can never quite make it mathematically self consistent. In string theory what happens in certain sub-domains is that you start with a lot of arbitrary possibilities, but then you demand certain types of mathematical self-consistency and magically it points out that there's only one or a small number possibilities. A classic example is: "how many dimensions does the universe has?" which no theory really gives as answer, but string theory at least points in a direction: "if you assume such and such, the the allowed answers are such and such". This happens a lot in string theory, and it's what drives people to keep digging. String theory on the other hand concludes that Lorentz invariance must hold at all scales "in some string-like theories" if you demand cancellation of divergences, which you must have for your theory to be renormalizable and therefore mathematically self-consistence. So in a sense this is a prediction of string theory. Not that LQG doesn't predict the opposite, that Lorentz invariance doesn't hold. Instead it assumes that it doesn't. String theory instead predicts that it does. The latter is much more impressive; anybody can start from an arbitrarily picked assumption that noone can prove wrong.
Perhaps you could elevate the discussion by providing an actual argument against this view of string theory, which has indeed percolated through social media?
For my part, I know a little bit more than "shit" about physics but I know very little about string theory and know better than to have strongly held opinions about things I don't understand. I've heard quite a lot about the criticisms and would like to hear a defense of it.
I have a lot more to say, but I wrote a little bit here: https://news.ycombinator.com/item?id=46336655
Ive been told my multiple High Energy Physicists that String Theory was suspect because it makes no predictions. Being able to make predictions that are testable is a foundation of theoretical science. Not everything is because of influences.
Eh... mainstream physics by numbers is not HEP and definitely not HEP Th, and there are plenty of serious physicists somewhat critical of the field, and more so of the way it presented itself over the last decades.
And while I disagree with some of the criticisms and some of the style of the crtics, it's not like you get an honest appraisal from Greene (and Witten).
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i dont think it has anything to do with threats to way of life. It has everything to do with public subsidy of physics that has pushed peripherary mathematics forward without much to show for actual physics advancements. New observations cause changes to string theory not validation of string theory. String theorists can keep do*ng their string theory but its time to subsidize something(so else and see if that leads to actual advancement. I think sabbine hossenfelder is largely correct about this
Theoretical physics is subsidizing a handful of people sitting at white boards.
Even accepting the premise that string theory is wrong I can list hundreds of ways the US budget spews money down black holes orders of magnitude bigger. The spending on string theory isn’t even a rounding error compared to the way my tax dollars are allocated to special interest pork.
But only string theory impinges on a generation of cranks who are convinced they alone have the insight into the true ToE and would be recognized as the new Einstein were it not for some entrenched cabal. Maybe I shouldn’t reflexively trust “big science” or something but it’s also not great to evaluate science by who is more charismatically narcissistic on a podcast.
Again, I don’t have a big axe to grind on the merits here. But it’s hilarious that folks with zero science background past middle school hear some of these cranks on YouTube and feel worthy to decry Witten as an enemy of the people. Between the podcast bro who was just told his ToE was right by ChatGPT and Witten I’ll take Witten.
I know absolutely nothing about string theory, or the culture of high-energy physics, but I don't buy the pecuniary argument you are making. You aren't considering the downwind effects of allowing academic rot. The Bourbaki—and their acolytes—also sponged up only a tiny amount of academic funding, but a fever in the pulpit can spread out into the pews; we've seen the "New Math" paradigm damage a generation of primary-and-secondary-school students. Even today, we have issues with engineers not understanding that a derivative is a slope and an integral is an area—due in no small part to a cartel of bad actors in mathematical research. Allowing bad behavior in high-value and influential positions has consequences beyond a waste of government expenditure; a president could turn a democracy into a banana republic, and we would have issues beyond his salary of a few hundred thousand dollars being wasted.
How many primary school students can't add fractions because string theory may be a less promising approach to a ToE versus loop quantum gravity or geometric unity? I know nothing about this stuff. You know nothing about this stuff. Since we both do know about the Bourbaki school of mathematics despite having different opinions on the value of building mathematics upward from foundational principles I'd say we are in the top .5% of the planet re general mathematical/scientific literacy. So I don't buy that even if string theory is wrong there is some massive spillover effect.
No, its subsidizing a handful of people sitting at whiteboards at the expense of different camps of people sitting at whiteboards and the result is nefarious because you dont see what could have been if we minimized string theory funding after a decade or two of poor performance instead of going all in on it for five decades. We gave up decades of potentially actually figuring something new out by going harder on string theory instead of diversifying physics spend as performance failed to show up.
how the government wastes money elsewhere is irrelevant to the conversation. Its about proper management of research funding and how string theorists managed tp trick us into funding failure for whole academic careers.
Since I sadly must return to the real world (but thank you everyone for the well spirited debate) -- string theory is funny to me because its a bit of a Rorschach test as such a tiny number of people who follow the subject can actually evaluate string theory vs. alternative models. It's just an abstract blob people can project their worldview onto. To the extent someone reading this is in the group who does understand the topic, this isn't about you--
As a society we can't place excess faith in the orthodox positions of institutions. We all know they can be rigid, wrong, and lock out dissenting views. But society today seems to embrace heterodoxy for its own sake the way perhaps in the past orthodoxy was just accepted on pure faith and there is a vast media ecosystem happy to promote (ie monetize) this worldview. Just because something is heterodox doesn't make it right.
Have a wonderful weekend all.
Again, I'll accept your premise for the sake of debate (which I welcome, and sincerely thank you for doing so respectfully).
Let me try to rephrase where I am coming from. I'm going to accept there is a good argument that some science funding should be redirected towards theoretical physicists pursuing alternate approaches.
1. The focus towards this matter in online media circles is vastly disproportionate to the relative impact this has on anyone's life compared to the multitude of other intra-silo disputes across the federal budget. It's not irrelevant to the conversation or at least my subsection of the conversation. It is interesting to me what debates burst through the noise and get traction outside of their own little world. Maybe 1% of the people debating string theory online actually understand a micro-fraction of this stuff. To be clear, I don't claim to be in that 1%. I'm interested in how that happened and the cultural+platform reasons for it. I'm interested in why alongside those genuinely interested in alternative approaches to theoretical physics this topic attracts tons of people who just lump it in with their "they are all lying to you" worldview. Nothing this obscure, incomprehensible, and yes irrelevant to most peoples lives should have organically reached such breakout status. I can ask some of the 22 year old bros at my jiu jitsu gym what they think of string theory and they will tell me it's all part of the omni-conspiracy. It's literally the only science thing they know. It's not like they understand a word of the debate or know of/care about a single other intra-discipline debate about the allocation of resources. 2. No small part of this is the unfortunate emergence of the online narcissist huckster and nothing plays better in online circles than "they" don't want you to know the truth that "I" have the true answer but "Big X" won't admit it. This clown show distracts from the real merits of the relative positions. But it does get the charismatic narcissist a slot on general interest "they are all always lying to you" podcasts. 3. Obviously this doesn't apply to legit physicists and good faith normies who simply disagree with the existing dogma. That's not who I'm talking about. That said, theoretical physics is bargain basement cheap. I don't need to build a supercollider the size of Mars. I don't need to sequence a trillion genomes. I need a laptop, a whiteboard, some time to think, and a bit of ancillary budget. Surely there are enough allied tech/crypto heterodox rich dudes at this point to fund a Center for Heterodox ToEs and staff it with 50 bright people to prove they have something to add. I can't pretend to have the chops to analyze Eric Weinstein's Geometric Unity vs String Theory. I do know if I really thought I had the answer to the universe and his bankroll/connections I'd just fund a real research effort to prove it vs. doing the podcast circuit ad infinitum.
If it is irrelevant to my life then it is easy, i shouldnt be funding it. I actually disagree. Physics progressing is very relevant to my life because physics progress drives huge positive societal change. That physics is stuck on string theory and that string theory has gotten us nowhere is why i dont have much cheaper energy, much faster computers, much faster travel, paradigm shifting medical options, etc. that a bunch of wankers captured a whole class of cuahy university job for whole careers has directly harmed me through lack of progress. I dont have to understand the theory to know whats going on. I only have to ser thr lack of progress for decades to know the right way to spend my money is to diversify until something moves forward.
Honestly that kind of straw man is about equally as grating as the "string theory critics" that watched 1 Sabine Hossenfelder video. And just as uninteresting.
Basically a framework Ed Witten invented for job security