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String Theory Does Not Win a Nobel, and I Win a Long Bet (scientificamerican.com)
298 points by Osiris30 7 days ago | hide | past | web | favorite | 155 comments





It's important to avoid conflating string theorists with all theoretical physicists. Plenty of people in particle physics either don't believe in string theory or don't think it can make useful predictions any time soon, even if it were assumed true. Furthermore, the vast majority of people called "string theorists" don't even work on traditional string theory day to day, but on more concrete ideas that have been partly inspired by it, such as holography and amplitudes.

This needs to be pointed out because there is a huge narrative bias out there. Science popularizers will endlessly frame things like "this whole field has no idea what they're doing, and only I, the brave contrarian outsider, can see through the fraud", even though they're only pointing out things that are already well known in the field. These narratives are completely wrong, but uncritically eaten up by people who think of themselves as contrarians.

Despite what the current top comment claims, you're not reading this article about Horgan because he was the first to think string theory would have trouble making predictions. Physicists have made this criticism since the beginning. Feynman pointed it out continually, and Glashow, one of the architects of the Standard Model, tried to bar string theorists from Harvard for the same reason.

You're reading Horgan's take, and not Feynman's or Glashow's, because Horgan is popular, and that's because he puts all his energy into expanding his popular reach. Only nonphysicists can do that, because physicists spend the majority of their time doing, well, physics.


String theory has completely dominated the field of theoretical high energy physics for decades. There have been some notable contrarians, e.g., Smolin and Woit with their books. But those haven't changed the fact that it has been very hard to get a faculty position in theoretical hep for decades without being a string theorist. It is only the last few years that has changed. In other words, it's not a biased view that string theory has completely dominated the field for more than 30 years.

Btw, the reason we aren't reading Feynman's take is that he died in 1988, not that he's too busy doing physics. He was very successful in doing both high quality physics and expanding his popular reach.


That's just not true. Look at the statistics for hiring faculty in theoretical high energy physics [1]. String theory was never more than half, and usually much less than that. (It is true, though, that for a while they had a near monopoly on pop physics. But that's totally different from physics.)

[1] http://www.particle.physics.ucdavis.edu/rumor/doku.php?id=st...


His statement can be true if you restrict it to "quantum gravity" jobs (of which string theory is one of many approaches, abeit the overwhelmingly most popular one). The other jobs you're talking about just don't try to answer the questions that string theory purports to addresses.

That is like understanding programming jobs as embedded Erlang. The thing is, that journalists really like to write about quantum gravity, but almost all theoretical physicist work on something else. (Roughly in the same sense that most lawyers don't work at the White House.)

I'm well aware of the distribution of theory jobs and what journalists like to write about. The point is that phenomenologists (and relativists, etc.) are necessary regardless of how dominant strings is. "All theory jobs" was simply a mistaken choice of category.

Despite its drawbacks string theory may actually be our best theory of quantum gravity, perhaps even enough to justify its hiring ratio relative to other quantum gravity theories. Maybe string theory has been treated in a balanced way all along.

Maybe, or maybe not. My personal opinion is that even thirty years ago it seemed stupid to bet almost all resources on a theory that was too complex for anyone to even produce any testable predictions. And I think it is even more stupid now, when the main result of the theory seems to be that it's not possible to use it for any prediction (10^500 possible universes, it's not possible to say which one).

Unless you mean "almost all PBS physics documentary budget dollars," I don't think almost all resources were bet on it.

From the money available for fundamental questions like quantum gravity and beyond standard model physics, almost all resources were bet on it.

It's kind of cute how some people now are trying to rewrite history when it is more and more obvious that it was a dead end.


There has to be a couple of orders of magnitude difference between "funders thought it was the best bet for quantum gravity," and "it was all physicists did for thirty years, full stop."

I, nor anyone else I saw (I haven't read all comments), have claimed that that was what physics did for thirty years. If you read my comments you'll see that I have been quite careful to qualify my statements when it hasn't been blaringly obvious from context.

Im a physicist, and whilst Im an experimentalist, I work in the same departments as theorists and I don't know a single string theorist. I heard of one, once. A friend od a friend, but I never met them. Most high energy physicists seem to be working on supersymmetry.

I am not a physicist, but I listen to a lot of technical lectures from the institute of advanced study and other universities that post their colloquia on youtube, and the impression I've gotten is that string theory has pretty much fused with quantum field theory. A lot of the people in the string theory discussions identify themselves simply as field theorists, with string theories being just another set of concepts in their model-building tool box.

I've been hearing good things about the super-asymmetry research from CalTech that was confirmed by Fermilab.

A good rule of thumb is that if you hear ”confirmed” and ”symmetry” together, the conversation isn’t about supersymmetry.

In this case, I believe that when someone talks about super asymmetry they're probably referencing this:

https://www.livescience.com/64557-the-big-bang-theory-super-...


So one person got the joke at least.

But we've already found half the particles!

> [Horgan] puts all his energy into expanding his popular reach.

I would not say 'all', but this bet fits the claim. If he had lost, his position as a prescient naysayer would be gone anyway, while a win could be used to boost it, even though, as it happens, no decisive case against string theory (or for an alternative) has emerged in the interim. In a sense, this bet is a columnist's hedge against there being no news.

For any counterparty, however, a win would have been completely overshadowed by the science itself. A person might be happy to accept the bet as a form of harmless entertainment, but for Horgan, it was more than that.


The advantage of being a mathematician is that the unifying theories for QM and GR just that, mathematical techniques to unify QM and GR. Unfortunatly, if you are a physicist, I assume your grants at some point will have the words "predictions" or "experiments" in them.

But for someone focused on mathematics, string theory, quantum loop gravity (if that is what it's called) and all the others become tools and objects of study on their own that have a unique perspective to offer in their own right. Whether you study one or the other then becomes a personality inspired preference. Just because I don't study number theory, doesn't by default scorn the field (or perhaps I just can't do number theory).


In quite a few countries, string theorists (and usually GR people too) are far more likely to be in mathematics departments than in physics. Pretty much for the reasons you describe -- GR was seen in the 60s as an exotic mathematical playground, not quite real physics.

This is also true of QM (not just because of QM computational sciences). My MSc thesis has application to quantum mechanics. I wrote a short summary of the generalisation that I made here [1], which generalises what the Nijmegen group calls quotient comprehension chains to sets. The authors of the latter QC-chains did not seem much interested when I emailed them.

In any case, ideally the framework should touch on geometry eventually as well, but I am not aware of concrete ways to do it. Toposes are considered geometric, but I don't know whether geometric in the sense of GR. The eventual or at least, hopeful, end point is something like [2] where your mathematical framework should ideally in the language of categorical or functorial duality express physical dualities. I don't know how to get to GR, as I say, and should read maybe this [3] but there are many ways to get to QM. One example is through entropy: the generalised abstract set subobjects are partitions and partitions encode entropy through "distinctions", i.e, elements in separate equivalence classes of the partition. The category of sets itself is a model for QM theories via it's inspiration for (symmetric) monoidal categories so perhaps one would want to express in the self-dual language that as well. It's one thing to point to multiple uses of category theory in physics, but it is another to keep track of it in your personal, internal intuition strategy.

[1] https://arxiv.org/abs/1808.01350

[2] https://en.wikipedia.org/wiki/AdS/CFT_correspondence

[3] https://ncatlab.org/nlab/show/duality+in+string+theory


I recently got my hands on a book about the career of a esteemed professor and his students. One of the life lessons of one of his students was: "If you want to be called a mathematician prepare to be funded like a mathematician"

Pure theoretical physicist might be in a comparable budget, but I think it is true that the lower expectations on math research is partly due to how cheap it is to fund.


What was the book?

"would have trouble making predictions. Physicists have made this criticism since the beginning."

You can go one step further. If you regard string theory as an attempt to answer questions about quantum gravity, then this criticism applies to the whole question, not just to any particular school of thought about answering it. This was known since approximately the time when physicists first had access to Planck's constant, Newton's constant, and a spare envelope to write on.

But, as you say, this is far from all that people who get called string theorists work on. A great pile of mathematical tools have been developed, to the point where deliberate ignorance of all of them would be a very strange position. Not for all fields of theory, obviously, but for quite a few.


Well I’m not reading Feynman’s take because he is dead right now.

I like the "right now" there. Like, fingers crossed, that could change...

It's not impossible, just isn't very probable.

Obligatory xkcd: https://xkcd.com/397/

All string theorists are theoretical physicists, noz all theoretical physicists are string theorists. Many string theorists contribute in other fields.

How is holography any more concrete than string theory? It is just as untestable.

You use it as a tool to compute what happens in real things, such as quark-gluon plasma or certain condensed matter systems.

You should be careful to not overstate it's rigorous application to QGP or condensed matter systems though.

For example, for QGP, holography can paint a nice picture, but we don't know a holographic dual for Nc=3 QCD.


We must not be discussing the same thing.

EDIT: yup, I am not knowledgable enough to be in this conversation.


It should really be called String Hypothesis. Theories in science are generally for something that's near 100% proven.

The difference between hypotheses and theories isn't about whether one is more likely true, they are different kinds of structures with different roles.

A hypothesis is ideally 'atomic': it's making a single assertion that should be falsifiable by experiment.

A theory provides a specific way of modeling the elements of some field of study, and how those elements interact with one another.

It should be structured in such a way that it can describe the components of any experiment that might be set up to confirm/reject a hypothesis in this field.

And once an experiment is described in the terms of some theory, the theory should provide a systematic way of calculating what the result of the experiment should be.

That's where the connection between hypotheses and theory comes in: actually conducting experiments assigns either Acceptance or Rejection to a set of hypothesis; ideally, the theory assigns the same Accept/Reject values to the same hypotheses in its predictions (this is probably never 100% the case in practice though—esp. not in an active field of study).

The structure of String Theory is much closer to theory than hypothesis. (It may have limitations in how much it models physical 'experiments,' but it's at least much more of a 'system description' than an atomic assertion.)


That's a trope made up on the spot to defend Darwinism from "it's just a theory/teach the controversy".

Whether in science or police work, etc. a theory is a holistic framework, while a hypothesis is truth-valued.

We should also complicate this idea that something can be 100% proven, but baby steps.


Physicists and philosophers of science give those terms different meanings. E.g. what a philosopher of science would call a theory is called model by physicists. What physicists call a theory is more a broad framework in which more concrete models can be build.

From the view of a philosopher of science string theory isn’t even a hypothesis as a hypothesis needs to be testable


FWIIW, Horgan is a well known science writer and author of a 1996 book called "the end of science" which pointed out that science in general and physics in particular has reached a point where there is no appreciable forward progress and is obsessed with non falsifiable woo like string theory. It's a provocative book; and people have raised the issue that Kelvin said something similar 120 years ago, but it's really worth reading.

He was 100% on the money that Noodle Theory was a lot of non-scientific mathematical baloney; a super unpopular position at the time (1996); pretty much the only prominent person in agreement with him was Nobel Prize Winner Phil Warren Anderson, who disagrees with him in many other respects. Ultimately many other writers came out in agreement on this issue at least; Woit and Smolin most notably, though others agreed. At this point I'm pretty sure even the physics establishment is a little nervous about hiring new noodle theorists. He's basically right about stuff like "complexity theory" as well.

I had a couple buddies who were prominent string theorists; some involved in its inception. One in particular retired a very disappointed man.


> a super unpopular position at the time (1996); pretty much the only prominent person in agreement with him was Nobel Prize Winner Phil Warren Anderson, who disagrees with him in many other respects. Ultimately many other writers came out in agreement on this issue at least; Woit and Smolin most notably, though others agreed.

Ugh, almost everything about this narrative is wrong; see my other comment. Science writers didn't invent skepticism of string theory, that was in good supply among physicists even 50 years ago. You only think they did because, well, you rely on them to tell you what happened, and they puff up their own roles. They turn it into "me vs. the establishment" while cribbing off conversations that are already happening within the field.

For example, Glashow, one of the architects of the Standard Model, tried to bar string theorists from ever being hired at Harvard, but you never hear about that.


Thousands of grad student careers, faculty appointments, glowing documentaries and ruined lives later and "oh, we knew that all along." They sure didn't act like they knew it at the time. Horgan deserves credit for making the right call. Even more credit because he wasn't even a physicist.

Credit to Glashow, and apologies for forgetting him, but Horgan deserves his victory lap.


I mean, do you think literally everybody was doing string theory? There have always been plenty of theorists focused on more concrete things -- string theorists are not and have not been the majority.

Grad students entering even in the 90s knew they had to make a choice between concrete, more easily testable physics and a long-shot approach to quantum gravity. String theorists have stories of faculty going out of their way, back in grad school, to discourage them from going into it. (It wasn't just Glashow, either, it was most of the Harvard physics department.)

To say that string theory comprises all of theoretical physics is to uncritically accept the "me vs. the establishment" narrative some pop scientists put out. I think it does real damage inside the field, too, because it distorts the perspectives people have coming in.


They weren't discouraged to do string theory in particular, they were discouraged from getting into the whole "trying to find something better than the standard model." If they anyway went into th hep, they would have slim chances of having any career if they didn't do string theory.

They were encouraged to do things like condensed matter physics, not trying to find some alternative to string theory.


So as long as there is one physicist on the right side of the fence the “field” is somehow in the know...? Would you be willing to extend that kind of reasoning to the “pop scientists”?

I often wish Feynman (or anyone of his kind really) was still here. Science nowadays seems more and more like one big appeal to authority...


Something that most people don't understand is that most physicists won't talk to the public. What you hear as a layman is usually the few people who have a public axe to grind and bears no resemblance to the majority of the field.

When I was in physics in the early 2000's, the general feeling was that it's a probably nonsense, but having someone out at the far end of the mathematical spectrum like that in your theory group was a good investment. And even if they were doing string theory, there's a good chance they were using it as a vehicle, a kind of generalized, more flexible version of field theory, to poke at some mathematical rabbit hole.

The majority of physicists are not in HEP. The majority of HEP physicists are experimentalists. The majority of HEP theorists are phenomenologists. But phenomenologists aren't generally good fodder for science journalists because statements like, "I'm calculating scattering cross sections in the kaon sector for CP violation measurements" isn't going to get clicks. And the experimentalists are even worse: "I've been working eight hour night shifts for the past two years. I'll probably go back to my home university and spend another couple years processing data to get an estimate for this parameter in this scattering calculation. It might be a fraction of a percent off what we expected!" Faced with that, "I'm playing with a high dimensional extension of quantum field theory to see if I can generate a spin 2 field in an expanding spacetime" sounds really sexy.


Honestly, I think physicists can't win here. Tommaso Dorigo (an HEP experimentalist) likes to talk to the public, so he has a blog. If you look right now his Plot of the Week is about how ATLAS "produced an improved bound on the rate at which Higgs bosons may decay to electron-positron pairs". This is the kind of thing that inspires people to write about how academic writing is inaccessible. Alternatively, physicists can write something more exciting, which is almost certainly highly speculative, and then they get dinged when the speculation turns out to be wrong.

I don’t pay much attention to the popular science depictions. Many of my friends are academic physicists (while I got out after my masters).

I think what I’m objecting to is that as the discoveries within physics become less and less impactful, the “field” seems to turn more and more inwards. Also, egos seem to expand approximately proportionally to the inverse of the utility of their work...


Why does he get more credit for not being a physicist?? So he made an uninformed conjecture that turned out to be true? (whether it is true also seems up in the air right now?)

I don't understand why that deserves kudos. I would very much prefer top scientists to listen to people who know what they're talking about, instead of paying heed to the less informed on the off chance their wild speculation bears fruit.


That's biased.

I will only accept the correct answer from people I choose. Experts in the field should provide the most insight overtime but don't ignore non-experts. That's foolish and limiting.


It’s difficult to know what kind of politicking led to this though.

It preposterous to think that all the physicists were on board with string theory. Do you really think the experts in the field didn’t have doubts and it took an non physicist to work it out?


I like Horgan a lot, but it's notable he also made a very wrong prediction that traditional proofs in math would start losing out to less rigorous means of collecting evidence for correctness.

https://blogs.scientificamerican.com/cross-check/okay-maybe-...

Although being a string theory skeptic was certainly a minority position in both academia and journalism in 1996, I think it's somewhat of an exaggeration to characterize it as a "super unpopular position" and Horgan and Anderson as the only prominent holders.


There are still a lot of prominent, respectable theoretical physicists who work on string theory. Leonard Susskind, for example. While no evidence of it has been found so far, is calling it "Noodle Theory" and a bunch of baloney really fair? There are plenty of big theories for which there's no evidence, but that doesn't necessarily mean we're certain yet that they're pseudoscience or unfalsifiable. Supersymmetry, Many Worlds, etc.

IMO calling it "noodle theory" is just a juvenile means to make fun of people who study it. If you want to tell people something is wrong, tell them why; don't invent childish names to put other people down by association.

I don't think Susskind works on string theory proper at all anymore. He works on the AdS/CFT stuff, which is compatible with and motivated by stringy approaches, but is logically quite independent. Related: https://www.math.columbia.edu/~woit/wordpress/?p=6252

There seems to be lots of forward progress in physics, e.g. in condensed matter physics, quantum computing, etc. Grand unified theories are sort of irrelevant so long as there are not measurable phenomena that cannot be explained without them.

> There seems to be lots of forward progress in physics, e.g. in condensed matter physics, quantum computing

The theory of quantum computing is based on real physics, unlike string theory. But we have no idea if or when we will be able to build a quantum computer that actually calculates something useful. So far the progress has been only in theory.

Edit: To downvoters, let's make a bet: In the next 18 years, no one will have used a quantum computer to break any encryption that hasn't also been broken by traditional computers?


Breaking a cryptosystem is not a good metric for whether quantum computers have become useful. Calculating energy levels of molecules, for example, is a much easier problem in the near term, and is of benefit to humanity. Breaking a cryptosystem takes vastly more and higher-quality qubits, and the end result is just that everyone upgrades to different math.

As a computational chemist, I assign 50% probability to the idea that quantum computers will be able to do useful molecular calculations cheaper than classical computers (for large batches) within 18 years. For small batches, classical computers will remain cheapest much longer because of overhead.


Progress does not mean "Commercial success". Your bet is like hearing "my kid seems to be making lots of progress on their bike", and responding with "I bet he'll never cycle around the world in 18 years".

The bet in the posted news was also about winning the Nobel prize, not about making just lots of progress.

String theory is 100% based on real physics, and it’s very difficult to make a theory like it which agrees with all known physics — that it doesn’t create any new falsifiable results is certainly a problem, but it could very easily be falsified by making nonsensical predictions about everyday phenomena, which it doesn’t do.

If anyone by the name of Crown Sterling takes your bet, don't trust 'em. They've got unified merrygorithms and kwuantum top hats.

What’s wrong with complexity theory? I remember seeing a talk about it a long time ago and the concepts were super interesting, but I didn’t (I don’t) have the mathematical maturity to understand it in depth.

It hasn't become concrete enough to make sharp, striking, correct predictions. It turns out the real world is extremely messy. Complexity theory can produce specific predictions ("disease spread will follow a power law with a critical exponent of...") but they won't be quantitatively correct. Or it can produce correct predictions ("airplanes increase disease spread because they increase the global network's connectivity") but they're generally obvious, and certainly don't require the full formalism of complexity theory to get.

I don't think it ever congealed into a coherent field, say, with an established canon of techniques and a heirarchy of results that built on itself.

Thank you for mentioning the book, it sounds interesting!

> noodle theorists

Lovely name


oh, I wonder if this is fitting with my current obsession with truth and lies.

Not only are we increasing the number of lies in the world, using lies to get what we want has become more and more acceptable through social media, politics, capitalism, etc...

But we are increasing the number of things you can't prove are lies. You can't falsify me, therefore I am right.

OMG, this is very religious. This is all because of postmodernism! Prior to today, you couldn't prove that my religion was wrong. The more people I could get to believe my lie about the origins of the universe, the more powerful I was.

Tribalism requires agreed upon unfalsifiable lies. I am with you because I believe the same thing you do.

Postmodernism has done this to us. With religion and an omniscient being watching us, heaven for the good, hell for the bad, we had a -- conscience.

Now, it's the internet. The internet is omniscient. Facebook is watching us. Google is watching us. The CIA and FBI are watching us through the internet.

We've replaced god with ... the internet. The internet is the new god. And thus, we are evolving toward the biblical God that created us in his image. We are walking down the path to omniscience via the internet.


I wonder if you might try the subtler word myths instead of lies.

Reality is formless, and we reason about it through what Foucault called grids I think, where every structure that we impose on it to bring something new into view necessarily obscures something else.

This is a bit like what Alan Watts talks about when saying that stories are like music, in which it wouldn’t have any form unless there were notes left out.

I think of a fact as a compressed statement of experience in service to some story. This is like the surprising observation that bits of information seem to always have some color that cannot be captured[1].

And there is the type of myth I like to call Fruith, as opposed to Truth. Most myths comprising culture might be these—in that we pretend things are true in the belief that it brings something more important to fruition, and that is the truth which overrides the seminal “lie”.

I see your despair, but I think it’s bigger than what you may be suggesting.

[1] https://ansuz.sooke.bc.ca/entry/23


When you say, "... it's bigger than what you may be suggesting."

What is ... "it"? My despair?

I understand your point about lies vs myths. If I substitute the two words in my mind according to your explanation of myths and their purpose, then everything actually does seem to make more sense and is more acceptable in my mind.

If someone tells a lie the connotation is that it's meant to harm others to their own benefit. If it's a myth, then they need that ... not accurate portrayal of the world in order to keep going... to survive, perhaps as an individual or group.


> "If someone tells a lie the connotation is that it's meant to harm others to their own benefit."

Who's connotation? I think that's a very myopic take on lying. Insofar as people care for others, people frequently lie to benefit those they care about. Some people believe the truth is more important than sparing the feelings of somebody you care about, and that's totally fine. But that point of view is not universal to humans and many people believe lying for the benefit of others to be reasonable or even obligatory.

I won't bore you with examples of such lies; I think you can probably imagine a few. Some are trivial, and others far more substantial. Whether or not those lies are justifiable under your personal system of ethics (or my own) is beyond the point; the point is that to some people those lies are justifiable and for those people, lying is motivated by a desire to benefit others.


“It” being what I understand about your philosophy of truth and what you mean by “accurate”. It’s hard to describe directly, since I’ve thought about this from a bunch of different sources that I struggle to synthesize, but I recommend this short story by Ted Chiang, The Truth of Fact, the Truth of Feeling[1], which I think does a great job of capturing that ineffable, paradoxical nature of truth.

[1] https://web.archive.org/web/20140222103103/http://subterrane...


The problem is that strongly-held myths can still cause a lot of harm to others. While it may be understandable for people to cling to some myths, we should still work to stamp them out, but compassionately.

Not sure if you got it, but it’s myths all the way down. It’s only by the values of one myth that another should be “stamped out.”

The book Sapiens covers this well, that you cannot escape the prison of a myth without being contained by one larger.


That's a matter of philosophy and opinion, not established fact.

> That's a matter of philosophy and opinion, not established fact.

If one takes “myth” to mean something that is itself believed without being falsifiable, it is true by necessity of any belief system with any content beyond statements about the subjective experience of the believer


Michio Kaku has long been my least favourite of the celebrity talking head scientists. And he has some good competition for that label. His pop-science books tend to read more like coming from a Hollywood screenwriter than a careful and thoughtful scientific mind.

Kaku is the Deepak Chopra of physics.

Harsh...

I have a copy of Kaku's Quantum Field Theory book on my shelf, but no Chopra (thank god)


Remember when he literally sued to block the launch of the Cassini probe?

For others reading, this appears to be because he believed that in an accident the radio-thermal isotope generator on board Cassini would spread radioactive material all over the place.

...all over the place

A small, but possible chance of Pu-238 spreading over Florida. I just read that 238 (half-life 87 years) emits mostly alpha, which is said to be easily blocked, even by paper. In FL, many go about half naked, so I'm not sure if this matters. I wonder how thoroughly Kaku considered everything.

Seems his concern was based partially on NASA's (small but not null) history of failures. I don't know, but doubt he was being deliberately unreasonable. Maybe his Japanese (distant) ancestry was a factor? Publicity would be a surprising motive. So would general ignorance.


Actually, alpha emitters are very dangerous when ingested, for the same reason they are readily blocked by paper - your body will absorb all the radiation. This is why Polonium 210 is one of the most toxic material known to us.

(Not agreeing with Michio Kaku, by the way.)


> Maybe his Japanese (distant) ancestry was a factor?

Why would it be?


Both atomic bombings, the Daigo Fukuryū Maru, and the Fukushima disaster come to mind. Perhaps a better question is why wouldn't people with a personal connection to Japan be wary of nuclear contamination? Or 'why don't the rest of us?'

Certainly there are some people in/from Japan who are enthusiastic about the future of nuclear energy. But I think it's fair and reasonable to say that cultural trends exist and a randomly chosen person with a personal connection to Japan is more likely to be critical of nuclear energy than a randomly chosen person from the rest of the general population.


Cassini was launched more than a decade before the Fukushima disaster.

As the only nation attacked by nuclear weapons, Japan tends to be anti-nuclear.

Nonsense. Few countries rely more on nuclear energy than Japan. Even Fukushima didn't manage to change that.

However he is not japanese.

"It would culminate the ancient human quest for knowledge, which began when the first of our ancestors asked, "Why?""

I'm always baffled when I read these kind of quotes, especially coming from such smart people. Do they just forget that our theories are models of reality? I personally believe that there are no wave functions or vibrating membranes out there, as there are no "triangles". These are just names for our mental models on which we map reality the best we can. Fitting models are very useful, but they certainly don't answer the big "Why?" and are doomed to be superseded by more accurate ones, when progress is made. Is it just me thinking this?


It’s a controversial topic in the philosophy of science. Your position is called anti-realism and has decent support but there’s no clear consensus either way.

>> "It would culminate the ancient human quest for knowledge, which began when the first of our ancestors asked, "Why?""

> I'm always baffled when I read these kind of quotes, especially coming from such smart people. Do they just forget that our theories are models of reality?

Some people have a relationship with "science" that bears a strong resemblance relationship some other people have with various religions and/or religious concepts. I get a strong vibe of that from the quote you cited.

> Is it just me thinking this?

No, it isn't. I agree and generally think of science is basically a kind tool-making activity. Mathematical wrenches, so to speak.


Suppose we are able to formulate a very neat, parsimonious mathematical model and it happens to extremely accurately describe every physical phenomenon, so accurately that we cannot find even the tiniest violation. Now, that does not mean the model is 'correct', it might be that we have just not measured precisely enough to detect its failures. But there does seem to be a mysterious tendency for very neat mathematical models to very accurately describe physics, and so maybe it is not unreasonable to conclude that this model is at least probably true (i.e., that it is never violated). Would this not then tell us something pretty profound? Even if the way we understand the math (in terms of ideal shapes, in terms of symbols) is inherently human, we would still have possibly discovered a full description of the behavior of the universe, and even if that in itself doesn't tell us why the universe exists or what it is, it would surely help us to answer those questions.

> "It would culminate the ancient human quest for knowledge, which began when the first of our ancestors asked, "Why?""

This is historical nonsense. There's an interesting book called Curiosity by Philip Ball that looks at the history of curiosity going from being a vice to being an epistemic virtue.


Your perspective is a popular one, but a lot of people also think there is a "true" theory that will perfectly explain how the universe evolves.

>a lot of people also think there is a "true" theory that will perfectly explain how the universe evolves

Doesn't Godel's incompleteness theorems make this doubtful? Logic was not my area of focus but I thought the basic idea was that there is always going to be some un-answerable question(s) or un-provable answers in any consistent theory[1]? I'm pretty sure there is not significant work using non-axiomatic math, I'm honestly not even sure what that looks like. I'd actually be quite interested to find out about some theoretical physics work that did not fall under the auspices of the incompleteness theorem.

[1] There are certainly caveats to "theory" but I believe all those caveats are satisfied by any version of String Theory be actively researched.


No, for instance you can perfectly describe the rules of Conway's Game of Life, and if you were an artificial intelligence living in the Game of Life you could presumably figure out the rules quite easily through experimentation. You wouldn't be able to prove those are the rules though, you'd have to make some assumptions that the rules didn't change in space and time, and that they weren't a manifestation of some more complex rules.

> you can perfectly describe the rules of Conway's Game of Life, and if you were an artificial intelligence living in the Game of Life you could presumably figure out the rules quite easily

I'm not so sure about this. It reminds me of the quote "If our brains were simple enough for us to understand them, we'd be so simple that we couldn't".


Conway's Game of Life is Turing complete, so if it is possible to build an artificial intelligence in a regular computer then it is possible to build one within the Game of Life. Also, understanding the basic rules of the game of life is not the same as understanding how an artificial intelligence within it functions. The rules that determine how patterns of pixels change in the game can be written down on a single sheet of paper, a description of an artificial intelligence built within the game would probably be absurdly complex.

>No

I asked multiple questions, I'm not sure which one you are responding to.


Presburger arithmetic is a decidable theory. "This means it is possible to algorithmically determine, for any sentence in the language of Presburger arithmetic, whether that sentence is provable from the axioms of Presburger arithmetic."

If you don't understand what the incompleteness theorems say, be wary of citing them.


Not sure why I should be "wary." I was asking a question. If one should be wary of asking questions about something how could they ever learn?

Sorry, yes, good point

[flagged]


I wasn’t suggesting that they would. I was warning against over-application/interpretation by giving an example of something one might not expect if one interprets the theorems too broadly.

In the context of the incompleteness theorem a 'theory' consists of a formal language to describe theorems, some primitive axioms and some rules that can be used to prove theorems from the axioms. Godel's incompleteness theorem states (loosely speaking) that if a theory is rich enough to describe the arithmetic of the natural numbers, is consistent and is 'effectively axiomatized', then there are statements that can be expressed within the theory and that are true, but that cannot be proven using the rules of deduction in the theory. In short, this is a totally different meaning of the word 'theory' to the one you are thinking of.

Sure, I'm not saying the "theory" in String Theory is the same "theory" in the incompleteness theorems but is there any mathematics or logic that are employed by string theorists that do not fall under the auspices of the incompleteness theorems?

A lot of people think that but a lot of people think that at any given time in human history.

There will - let there be no doubt - be a final theory of physics (Humanity will end at some point), but determining whether that theory is truly "perfect" is probably impossible within the bounds of measurements known to us at the moment.


Models (mental or not) work by analogy, and analogies can be very convincing in general and in answering the question “why” in particular. That is all that is normally needed; unfortunately, some people are hard to satisfy.

The human quest for knowledge started which "how...?"

> here are no wave functions or vibrating membranes out there, as there are no "triangles".

I wish you'd added "There is no spoon" here. Opportunity missed.


Haha, indeed, missed opportunity :)

Two weeks ago I heard a very interesting EconTalk podcast[1] by Sabine Hossenfelder on Physics, Reality, and Lost in Math.

Hossenfelder herself is a theoretical physicist, and researches quantum gravity. And a Research Fellow at the Frankfurt Institute for Advanced Studies. She has a refreshing tone and frankness, and I appreciated learning about her work.

Quoting the podcast's abstract:

"Hossenfelder argues that the latest theories in physics have failed to find empirical confirmation. Particles that were predicted to be discovered by the mathematics have failed to show up. Whether or not there is a multiverse has no observable consequences. Hossenfelder argues that physicists have become overly enamored with the elegance and aesthetics of their theories and that using beauty to evaluate a model is unscientific. The conversation includes a discussion of similar challenges in economics."

[1] https://www.econtalk.org/sabine-hossenfelder-on-physics-real...


It's very likely a unified theory will win a prize maybe even the Nobel Prize but it isn't going to happen anytime soon. FWIW I'm about as convinced of the truth of string theory as I am of the truth of General Relativity. Sure a better version of M-theory or something else is sure to be discovered but it will be an outgrowth of the current enterprise. The problem is even if we had the correct theory right now it probably would not do us much good at all. It would be a puzzle box we couldn't even open or get answers from it. People underestimated the difficulties involved and the theory was over hyped. Now begins the long "string theory winter". Decades from now, some diehard whose career is foundering will make a significant breakthrough, enough to compel everyone's attention. Until then, there's plenty of interesting physics problems to work on that have been unjustly neglected for too long.

Einstein's theory of GR could end up being "wrong" but it would live on as a very good approximation to a more fundamental theory.

String theory could very well turn out to be completely wrong but it would fail in a very different manner. If ST is wrong, it's no longer useful. If GR is "wrong" people will still use it.

For various reasons which are by no means proof or even evidence I think ST is basically correct but we're simply unable to make proper sense of it.

Anyway, we're here at the string theory winter. Careers are ruined, people disappointed etc. That's just how it goes. Sometimes, things work out and sometimes they just don't. We didn't exactly walk away from all of this with ZERO but we're very far from the ultimate PRIZE or GOAL. In hindsight we'll probably look back on this and realize we were hopelessly unable to succeed given the tools and ideas of the day. Expert systems were simply unable to deliver and people were crushed. Careers were ruined. Hopes dashed. Naysayers vindicated then along comes this crazy guy who just won't give up on neural networks.

I think the future looks much brighter for unified physics now that string theory as we knew it has clearly failed. I don't want to leave these guys out too so let me add that loop quantum gravity has failed too, much more gracefully I might add. I think these guys were on to something and their ideas aren't going to completely disappear.

I've thrown away about 10,000 hours of my life on this stuff. Thanks for spending 3 minutes on my meager insights.


This can happen in academia. I went through Stanford CS, finishing in 1985. That was about when it was clear that "expert systems" were not going to lead to Strong AI Real Soon Now, or, indeed, much of anywhere. But many faculty were in deep denial about that. The "AI Winter" followed. There was little progress until machine learning finally took off about two decades later.

I still remember reading an article about Doug Lenat and Cyc a long time ago in some pop sci publication and thinking, surely you can't be serious...

I don't understand how people ever thought such things could become equivalent to human minds, but I don't think that's my insight, but that others' thinking was blinkered for some reason.


Makes you think about what we think today that will be seen likewise by future people.

You're being downvoted, but we' re basically drunk on these amazing successes in Computer Vision and apply at least some magical thinking when expecting them to extend to general (e.g. reinforcement learning) domains.

AI is doing a lot better now than in the 1980s. AI back then was groups at MIT, Stanford, and CMU, and a few small groups elsewhere. Almost all the 1980s AI startups went bust.

This time, there's enough success that the field is self-funding. Cynically, because mediocre machine learning is good enough for ad targeting.


You mean AI planning and stuff?

I’m bearish on reinforcement learning right now. Is there good stuff happening in a comparable front? (Will a blocks world solver ever play Super Mario?)


"The Nobel prize judges have always been sticklers for experimental proof."

One of the big challenges of devising a grand-unifying theory of everything is that, if it doesn't make different predictions than existing theories do in any context, it's experimentally unverifiable. We can hope for a unifying theory that makes everything simpler, but it's far more likely that a theory that deals with all things at once will makes dealing with special cases harder. If such a theory is harder to work with and does not differ from special case theories that are easier to apply, why bother?

Of course, a unifying theory probably will differ from existing theories in at least some contexts. They may be extremely high energy, gravity, etc. contexts that are beyond our current technology to test. String theory likely falls into this category. The question is, how much resources should we pour into developing a theory before demanding that its differences with currently accepted theories become testable?

Quite frankly, answering this question is above my pay-grade. Scientific history is full of both dead-ends and things that were initially thought to be useless that have since become the foundations of entire fields. How do we know which string theory is? If we cut funding to string theory development, are we cutting off a field that will one day be essential? By continuing to pour funds into string theory, are we funding a dead end and starving several other things that might have been revelations?


> One of the big challenges of devising a grand-unifying theory of everything is that, if it doesn't make different predictions than existing theories do in any context, it's experimentally unverifiable.

Yea, but then it isn't a unifying theory it's basically just a giant case statement of "if relativistic motion, use relativistic motion equation". That isn't a unifying theory, that's more like a programming library that does everything.

A unifying theory would have to allow one to unify all of the existing equations we have as well as synthesize new ones; not just the ones we already have. It probably doesn't exist. It smacks too much of an NP-hard compression problem, where if we have enough output of the function we can find the minimal representation of it, but applied to everything in the universe.


> if it doesn't make different predictions than existing theories do in any context, it's experimentally unverifiable

Given the number of holes in and between our theories, this seems unlikely. And there are still a lot of experiments yielding surprising results in fundamental physics.


Whether you get it right or wrong, I really appreciate people making verifiable predictions about the future publicly.

On the other hand, I am less and less interested in post hoc analysis done by journalists and academics judging after the fact, what should've happened.


Other than for fun and to donate to a good cause, I'm not sure why anyone would ever take the other side of a bet like this or the follow up one for the case of wine. The author is basically betting against an unlikely outcome and the challenger is betting on it, with no adjustment for the likelihood. This would be like offering a bet that a particular college football team won't win a national championship and getting even money that they will.

I realize this is outside the scope of the article, but I think it's worth noting because the author gets outsized credit for being correct despite not really offering an alternative. To be fair the author should have had to bet an alternate area that would win a Nobel prize before 2020, otherwise it's a push and each person's stake goes to charity.


>Gaining access to the infinitesimal microscales where superstrings supposedly wriggle would require an accelerator 1,000 light years around.

Has anyone ever proven that there aren't any better accelerator technologies left to be discovered? What about natural accelerators like the charges that build up and produce cosmic rays?


This is a common suggestion and it is used more and more. The problem is the data rate: with LHC you have a flood of interesting events to record in a very controlled environment. On the other hand, super-high-energy cosmic rays are very rare and frequently you do not know many of the initial parameters necessary to interpret the measurement.

Cosmological measurements seem to be promising (akin to looking for footprints in the cosmic background from extremely high-energy phenomena from the early universe).

And excitingly, extreme precision "table top" experiments are also promising. Check stuff like the recent work on measuring the (nonexistent) dipole moment of the electron.


> What about natural accelerators like the charges that build up and produce cosmic rays?

As mentioned the benefit of artificial accelerators are that you can make the collisions happen right in the middle of the detectors, which is quite nice. You can also generate a lot of collisions, which is good because statistics require it.

That said, there are projects, such as this[1], utilizing natural accelerators. There's a technical talk about their results here[2]. The first part explains the system in more detail.

[1]: https://www.auger.org/index.php/cosmic-rays/detection

[2]: http://pirsa.org/17120007


Thanks for posting that reference to the (Pierre) Auger Observatory with links and all. We loved to point out that at current accelerator tech, our high energy events would need a ring with about the same radius as the Earth's distance from the sun. What also blows my mind is that there aren't really credible/supported theories about what process or effect may be able to put as much energy into a single particle. Whatever it is, my money is on that is a process that happens at large scales (just like Fermi acceleration), so the "giant accelerator" bit remains somewhat true, except we don't have to build it. :)

As a long-time antagonist of Kaku and string theory / supersymmetry, Peter Woit naturally has a blog entry[1] on this that's worth a look.

He points out Prof Gordon Kane upped[2] the ante:

> By 2020 there will be a Nobel Prize for a string- or unification- or supersymmetry-based theory or explanation or experimental discovery.

And goes on to give us some insight into Kaku's current point of view. Spoiler: he thinks string theory will give us the "God Equation" when it reaches its final form!

1: http://www.math.columbia.edu/~woit/wordpress/

2: http://longbets.org/12/#comment-166313625


Correct me if I am wrong. i think string theory is searched not just because of its beauty, but also because of existing problems in general relativity. For example, the center of black hole is predicted to be `infinite` in terms of many metrics . But the center is also part of the spacetime, it should bear some measurable values. The answer might require quantum physics since it is microscopic. Therefore, the unifying of general relativity and quantum mechanics is asked for.

Yes, quantum gravity is searched for. String theory is not quantum gravity, it is a specific approach to quantum gravity that has not been very fruitful.

Ah, thanks for pointing that out!

String theory is probably the one scientific topic I spend the most of my free time learning about. It is fascinating. I have read Brian Greene's 'The Hidden Reality' over five times, I think.

I recently watched his conversation with Sam Harris and was intrigued by a point Brian made, albeit about quantum mechanics and the 'many worlds' theory.

Brian claims that he doesn't think the many worlds theory holds water because it makes an assumption about what happens before some object is measured (A) and after that same object is measured (A'): while many worlds claims that all possibilities are indeed realized, Brian claims that we just don't know for sure what happens between events (A) and (A'); he claims that a unified theory would explain what happens between those events.

In any case, that's just me rambling about it. Thanks for the post :)


Sadly, popular discussions about topics like these are usually not worth spending any time on. There is no shortcut for digging into the math.

> while many worlds claims that all possibilities are indeed realized

That's...a problematic statement since you have to define "realized" without resorting to any classical concepts. Once you manage to excise the classical concepts you end up with something that is perfectly reasonable.

> Brian claims that we just don't know for sure what happens between events (A) and (A'); he claims that a unified theory would explain what happens between those events.

I suspect that this was a communications breakdown. It's hard to imagine a quantum physicist today postulating this in the face of the last few decades of experimental and theoretical work on the foundations of quantum mechanics.


> characteristic radiation from black holes and Creation

Wait, did the author just refer to the Big Bang as "Creation" with a capital 'C'? Since when did Judeo-Christian mythology (or whatever mythology you think "Creation with a capital 'C'" means in the author's culture, inferring some creative agent in the "beginnings" of the known universe) become relevant in this article's context?


I also noticed that.

So is all this about the fact that String Theory just didn't turn out to be practically useful? Or is the theory no longer believer to hold weight given current observations?

It is not about being useful, it is about there being zero experimental evidence for string theory.

I'm really a commoner when it comes to physics, so indulge me if I don't make sense.

As I gather then, there's been no experiment showing evidence to String Theory, but all experimental result are also not contradicting it and fitting inside its models?

If so, I don't really understand how both these thing can be true at the same time. Is it that people criticize String Theory for kinda being too broad, so in a way, it allows too many things to be possible, but that also renders it useless for prediction, because it's not close enough to exactly what happens?

Like saying that the weather on any day must be between -100 and 100 celcius. It will be hard to find evidence to the contrary, but it's so broad that it's useless for any valuable predictions?


Is there a clear boundary where string theory ends and Standard Model starts?

the whole time I just kept thinking, "but... when they put up their money in 2002 it was invested right?? The charity got something more like $2880? why aren't they telling us!?"

Can it even win a Nobel? I thought the Nobel is not awarded for math, and string theory is just math, with no verifiable real-world side effects or consequences that I'm aware of.

Nobel prizes skew heavily towards experimental physics and theory prizes require experimental verification. That's why Higgs had to wait until 2013 even though absolutely everyone was convinced that a Higgs boson existed for decades before that.

Even Einstein didn't win the Nobel for GR, but for the photoelectric effect. Back in the day when high energy physicists kept discovering new particles and there was a short delay between theory and experiment, there were more Nobels awarded to theorists for this, and I think that golden age of grand unification progress created a false impression that theory work is expected to win Nobel prizes just for being good theory work.

But if you look at the last dozen or so Nobels, they are all for describing observable phenomena or conducting novel experiments: (lasers, discovering exoplanets, detecting gravity waves, theoretical descriptions of phase transitions of matter, LEDs, mass of the Neutrino, etc.) It would take very convincing experimental confirmation before String theory wins a Nobel, but there are lots of other prizes awarded to string theorists, and Witten even won a Fields medal, which is more prestigious than a Nobel to the math community.


My history of physics is probably simplified, but I think Einstein got it for (mainly) the photoelectric effect in part because relativity was still (despite having been verified to some extent already) too weird.

Yes, it was given for the photoelectric effect and other work (which was nudge nudge, wink wink, relativity). Everyone forgets just how much physics Einstein did besides relativity. Brownian motion, for example.

Turns out that the photoelectric effect as described by Einstein was possible to get out of classical physics, though, so it took a few more iterations in the later 20th century to really nail that one down again. See 'The Quantum Challenge' by Zajonc.


Kaku also incorrectly predicted HEVs.

Mandatory string theory introduction for the novice https://xkcd.com/171/

This guy really hates the search for grand unified theory, wow. What a miserable fellow.

I don't think he hates it so much as being pessimistic about finding it in a hurry.

I can't wait until String Theory dies. As a couch scientist it seems to very clearly be a dead end.

They keep massaging it to make it fit any new objective discoveries but an accurate theory matches new data, it doesn't need to be forced to fit with it constantly.


Quantum computers might be able to perform simulations which will be indistinguishable from reality. Many theories can be tested that way once we have a sufficiently powerful quantum computer.

While I agree on the promise of quantum computing, the way you phrased it is somewhat misleading (hides plenty of complications (even theoretical ones) under the rug). Moreover, even if we can simulate a theory efficiently, we can not use that simulation to learn the value of a (hyper)parameter, without being able to make an observation.

And this is the main problem: it is infeasible to make observations in the parameter regime of interest. The difficulty of simulating the theory is borderline inconsequential in this case.


Is observing a parameter not allowed by quantum mechanics or a current fundamental law?

I am aware of the difficulty involved but an optimistic view is that anything is possible until fundamentally proven otherwise. As far as I’m aware, quantum computers would be able to simulate an entire universe in theory.

Sorry if my initials comment seemed to disregard the enormity of the problem. I realize we might be decades/centuries before any of this is testable. Not unlike how Newton was compared to our current understanding of physics.


The parameter regime of interest is monumentally out of reach to experiments. We can already derive things on paper about that regime, and with better computers we would indeed be able to make more complicated calculations about that regime. But to get something useful we also need to "fit" these calculations to observations. We do not have observations not because of a fundamental constraint, rather because it is engineeringly impossible to reach these energy scales with anything we can imagine. So the roadblock is experimental and a quantum computer would not be particularly helpful with it.

You can't test string theory with a quantum computer.



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