The string theory hype machine will never die
math.columbia.edu
math.columbia.edu
It has exactly none of the problems of string theory, and I am not sure why it's clumped with a physics paper in the blog. How is it a problem to say "hey they used string theory tools!" in a press release? If anything it might get other people to look at the math and get something good out of it...
String theory came into the public consciousness about two decades ago, followed by a backlash from a relatively small but persistent set of professors. String theory has largely dropped out of the public focus, but those researchers continue to hammer at it.
Woit is one of those. He's known primarily for his objections to string theory. His own work is just fine, but nobody outside of his discipline knows it.
> with string theorists now virtually unemployable unless they can figure out how to rebrand as machine learning experts.
Their issue is (seemingly) not with the paper, but with the claim that these headlines feed a hype that attribute to string theory capabilities it doesn't have.
To be clear this is OP's argument, not mine. I am not sure I buy it, except perhaps for the fact that every other academic is expected to rebrand as an ML expert nowadays. It has more to do with ML hype than with string theory hype.
It would be helpful to have more clearly targeted and titrated criticism, because you’ve mentioned press releases, a sciam article, the paper, and Sabine all without differentiation.
I hope it’s clear enough the paper itself is legit and doesn’t seem to make any inappropriate claims. Beyond that, the PRs seem to be the real offenders here, the sciam article less so (could be argued that’s healthy popsci), and I’m not sure what comment you’re making about Sabine. The title of her video may be click baity but the content itself seems to appropriately demarcate string theory from the paper.
I think it's largely uncontroversial that the math in string theory could be useful in other areas. But if that's your argument for the legitimacy of string theory then the question arises what string theory is and if it is still part of physics. Because physics has, of course, the goal of describing the real world, and, my understanding is, string theory failed to do that, despite what many people have hoped.
If string theory is "just a way of developing math that can be useful in totally unrelated areas", it's, well, part of mathematics. But I don't think that's how the field sees itself.
“My nervousness was perhaps at its greatest because the illustrative area that I had elected to discuss, namely string theory and some of its various descendants, had been developed to its heights in Princeton probably more than anywhere else in the world.”
“Moreover, that subject is a distinctly technical one, and I cannot claim competence over many of its important ingredients, my familiarity with these technicalities being somewhat limited, particularly in view of my status as an outsider.”
“Yet, if only the insiders are considered competent to make critical comments about the subject, then the criticisms are likely to be limited to relatively technical issues, some of the broader aspects of criticism being, no doubt, significantly neglected.”
The fact that Penrose felt nervous criticizing string theory has made me think less of string theory (or rather, the humans behind it) ever since.
That's from 2003, when the string theory theorists were riding high and attacking string theory was bad for a physicist's career. Now, "with string theorists now virtually unemployable unless they can figure out how to rebrand as machine learning experts...", the situation has reversed.
String theorists understand high-dimensional math, so maybe they can do something for machine learning theory. Probably not, but we can hope. It's frustrating how much of a black box machine learning systems are.
Yet, no one knows how to turn it into an actual theory in physics. It feels like we had QFT but weren't able to create the Standard Model.
It is, obviously, possible that the String Theory framework is just too broad. Or that it is in principle true, but we reached a level where it is too hard. Or it is just a step in the right direction, but we are missing something.
Given the effort of the smartest minds and still no progress (I do not think there is any hype left), it is possible that we need to wait for something more. Like the revival of artificial neural networks in the 2010s, after decades of slumber.
How would I advance from this point, what should I read to get a grip on string theory, including the concepts and maths involved? Could you recommend some resources?
Like why did they come up with the concepts they came up with, how does that help explain established theories and experimental phenomena on a deeper level, etc.
Also I've noticed there are several competing theories in this domain (like Quantum Gravity, String Theory, hope I'm not wrong), what are the odds that these theories end up being equivalent?
As others have pointed out, compared to classical physics, quantum mechanics describes the world of tiny distances and energies in greater detail while relativity becomes useful at the opposite end.
How would one construct an experiment whose results depend on both phenomena?
String theory aims to explain all physics as manifestations of a mathematical concept best understood as a vibrating string.
Initially, the hope was that string theory could predict the particle masses we observe, but that hasn’t worked as it turns out there were many different predictions possible. String theory has also struggled to develop a version of the theory that does not contradict known properties of our actual universe.
Loop quantum gravity is not equivalent to string theory, except that it also tries to unify gravity and quantum physics.
As things stand, string theory is not falsifiable, while that is the case, you could argue it does not count as physics.
But, by multiple accounts, it is interesting math, which can be worth doing for its own sake, and it’s happened often enough that interesting math turned out to be useful somewhere. Just not for explaining physics.
I think the main thing is, even if string theory turns out not to describe reality, it shows that quantum mechanics and general relativity can be reconciled within a single, mathematically consistent framework. The tension between the two is gone and it's actually needed for physical correctness. Simply knowing that such a reconciliation is possible is already a meaningful result.
String theory emerged from attempts to quantize gravity. I think the most interesting thing is that when a relativistic string is quantized, a massless spin-2 particle inevitably appears in the spectrum. This particle behaves exactly like a graviton, meaning that gravity is not introduced by hand but instead arises naturally from the theory.
Competing approaches may possibly be all compatible, much like different interpretations of Quantum Physics.
The main difficulty with experimental tests is that the relevant energy scales and distances are far beyond what we can currently probe in the laboratory. This is not a weakness unique to string theory, but a general problem for any theory of quantum gravity. The Planck scale is simply too extreme to access directly with present technology.
As for experiments that depend on both quantum mechanics and general relativity, in principle these would involve situations where quantum coherence and strong gravitational effects are both important. Examples include black hole evaporation, aspects of early-universe cosmology, and possible quantum effects in curved spacetime. These are extraordinarily difficult to study experimentally, but they are what motivates the search for a theory of quantum gravity in the first place.
It does not presuppose a background in QFT. It does require you to know quantum mechanics. Mind you, it's not as deep as the standard texts (Polchinski et al. or Kaku's work prior to going off the rails) or my favourite which is the two-volume "Quantum Fields and Strings: A Course for Mathematicians". But it makes reading the others possible.
https://www.youtube.com/watch?v=sAbP0magTVY
I think it is a great watch for anyone with an interest in the field.
I knew a someone who was a temp visitor at the Institute for Advanced Studies who was given temp office next to Witten. And he said he wouldn't hear a noise, and the one day he starts typing and doesn't stop until 100 pages of paper are written, like he has it finished in his mind before he starts typing. Somehow I'm inclined to believe it can't be far from truth.
I guess what I want to convey is how sad your comment makes me. What went wrong that makes you, and anyone really, trust that man's opinion on physics?
Here is a cynical but overall rather accurate takedown of Mr. Weinstein:
Has it been rigorously shown that it can never be tested? Or is that your prediction?
But yes, not rigorous.
People talk about this as though it's an attempt at deception, whereas two people notionally working in string theory could in fact be proposing highly incompatible models which would be conclusively ruled out (and a lot of them have been in so far as that can be done - i.e. experimentation has put tight bounds on their possible parameters).
Yeah... except that hasn't been proven. That's just your belief, right?
I don't think anyone has proven that string theory can yield no testable predictions. I think if someone had, that'd be a big deal.
And I don't think we should pretend that an open problem is closed just because we don't like it.
The TLDR is that you can never expect the same level of certainty when you don't have direct experiments, but you can still rule out _some_ hypothesis, and see how far other hypothesis take you. This is called theoretical physics. Just because you can't make an experiment doesn't mean you can't do anything.
Certainly internal self-consistency will take you a long way if you don't have experiments. Some people find beauty in this :-)
The other things you refer to are still Occam's razor: symmetry is handy because it eliminates symmetry-breaking entities even though we know they can happen in the standard model (Higgs) and "beauty" is really just another way of saying Occam's razor - you'd prefer your theory to not be full of dozens of free parameters because it starts to fit any possible outputs and be less predictive.
At all points the issue is that unless you've fully explored a simpler space with less entities, don't start adding them because you can always keep adding them to solve any problem but predict nothing (ala epicycles keeping geocentric solar models alive. You could probably run a space program assuming the Earth is the center of the universe, but it would be fiendishly difficult to model).
I think it's better to think of most real world models as being low dimensional-ish, where there is a decaying power law of eigenvalues, and most are quite small, though not zero. You can get quite far by looking at the largest modes and ignoring small ones, but you're not exact, so you're not seeing The Truth, or whatever. Forcing your self to use fewer parameters is a way of denoising, however, that is quite effective.
- Albert Einstein
Because you can write a lot of mathematics with no practical applications for generations (then whoops: number theory and cryptography!)
Of course physicists sometimes do make wrong predictions and it can take some time to figure out the hypothesis is wrong. However the goal is always to make something they can test to prove the hypothesis holds, which string theory has so far failed to do.
as long we have to do with a consistent string like theory.
Is my understanding correct?
Meanwhile, there's interesting experimental action in low-energy physics, down near absolute zero. Many of the weirder predictions of quantum mechanics have now been observed directly. Look at the list of Nobel laureates in physics since 1990. A big fraction of them involve experiments with very low energy states, where thermal noise is small enough that quantum effects dominate. Some of that work led to useful technology. That's forward progress.
Astronomers can observe extremely energetic environments from a great distance.
It's not a controlled experiment, but sometimes they get lucky and see something that suggests new physics.
I have no idea what might be needed to provide astronomical evidence for string theory.
Even when we are able to operate at higher resolution sometimes the model makers still operate on their own scales. For example, I believe political science and economics ought to be studied from a biological perspective if they are to be fully understood, since gene by environment interaction determines so much. However, there seems to be little interest among political scientists and economists to study the nitty gritty of molecular and population genetics, and little interest among the molecular and population geneticists to study political science and economic theory. And because of this, seems to me such models will always fall short compared to models that operated on a perhaps more appropriate scale of inputs.
In a meritocracy,
“string theory lied to us and now science communication is hard.
People need to get fired
Even if string theory cannot explain the universe, there may still be some value in it.