https://news.ycombinator.com/item?id=46336655

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.

> 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.

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.

   In a meritocracy,

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.

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.