Three weeks ago, Natalie Wolchover interviewed Edward Witten and one of the weird changes that happened after the publication was the demotion of M-theory to "a" candidate for a theory of everything. Previously, Edward Witten was implicitly persuading Wolchover that string/M-theory was the candidate but a Sabine Hossenfelder was more influential and easily convinced Wolchover to basically assume that Witten doesn't know what he's talking about, to change the classification of string theory, and to thank Hossenfelder for this change.
Now, Natalie Wolchover wrote a short article
What about the article? I don't actually understand what is meant to be their answer to the question in the title. And in between the lines, I feel that Wolchover didn't enjoy writing this text. It repeats several of the usual things. String theories were perturbative and the gravity is too weak in the perturbative description. That's why this description doesn't remain controllable when (many) gravitons collide with (very) high energy to form black holes. In perturbative string theory, they "can't". (I am trying to make more concise yet more accurate claims than the article.)
Witten didn't have any definition of M-theory in 1995 but he was able to argue in favor of its existence and derive its properties, his colleagues at the USC Strings 1995 were stunned. AdS/CFT exploded 2+ years later, got 16,000 followups, and none of the proposed "competitors" to string/M-theory has achieved these things, especially the leading quantum correction to the graviton scattering, which is why string/M-theory is the leading candidate, she writes.
Obviously, if the article really matches this template, it's way too sketchy, inaccurate, doesn't really answer the question from the title, and much of the skepticism that readers may preserve after they read this article is absolutely understandable. Concerning the graviton scattering corrections, the one-loop corrections vanish for various reasons (or conventions may be picked so that they vanish) and one starts with the two-loops corrections. But the fate of the two-loop corrections involves new physics in string/M-theory, it's rather complicated, and while the story is consistent in all string/M-vacua, I don't think that such a sketch may be used as a good "proof of M-theory" – I don't know what exact proof like that the authors would have in mind.
Many subtleties in her formulation of things unmask her actual misunderstanding of these issues, even the basics. For example, she describes the relationship between string theory and M-theory by a sentence talking about "String theory (or, more technically, M-theory)...".
Well, I don't think that M-theory may be described as a "technical name for string theory". String theory and M-theory are equally technical, both names are equally quasi-poetic, they are really connected to one theory, but these two terms are used to emphasize two (classes of) limits of the theory. String theory is either used for the whole theory including M-theory; or especially for its vacua or situations that boil down to the five perturbative string theories in 9+1 dimensions – type I, IIA, IIB, heterotic-E, heterotic-O string theories. On the other hand, M-theory is a limit without strings whose simplest vacuum is 10+1-dimensional.
If you combine my criticism with the knowledge about the morons' anti-string populist movement, you can't be surprised that the (modest) feedback is dominated by negative responses. Most prominently, Peter W*it misinterprets the statement about "having no equations defining M-theory in 1995" as "M-theory doesn't exist", as he did many times. Sorry, we have had full definitions of M-theory for over 20 years, starting with the BFSS matrix model and continuing with the AdS/CFT in AdS4 x S7 and AdS7 x S4.
He also quotes Lisa Randall who has mocked M-theory as being "quantum gravity but only in 11 dimensions". Needless to say, this statement is both wrong and it would be irrelevant if it were right, too. M-theory isn't a theory in 11 dimensions only. The vacua with a lower number of large dimensions are exactly as kosher and obey the laws of M-theory as much as the 11-dimensional vacuum. On top of that, we really have lots of evidence that the extra dimensions are needed to explain the relative complexity of particle physics (the Standard Model) in our Universe. Even if you didn't see it, all the evidence suggests that the truly deep problems in quantum gravity etc. are "qualitatively the same" in 4 dimensions as in 11 dimensions (and in the dimensions in between).
I don't want to go to technicalities because this blog post of mine would have to outshine the piece in the Quanta Magazine by orders of magntitude. Instead, I want to say something about psychology and sociology.
David Simmons-Duffin's heart could be applauded for helping articles of this kind to be written. But at the same moment, I feel it's a waste of time today. First of all, the influence of the Quanta Magazine is extremely limited because this outlet has never fit into the populist, somewhat anti-science and politicized narrative of the pop science media. Second, in the recent decade, everyone in the public who cared has been bombarded by such an incredible amount of lies and idiotic malicious slogans that you just can't fix the problems by one sketchy article in the Quanta Magazine, not even by several articles.
At N*t Even Wr*ng, Peter W*it's notorious anti-science website, the blog posts have ID and the newest one has almost 10,000. Not all the numbers have been used. But the number of blog posts could be comparable to 1,000. Most of them contain some lies and vitriol about modern theoretical physics, usually 1,000 times repeated lies, some basic misunderstanding of what science is, what physics is, what it means to have evidence, what is actually being computed and why, what are the actual problems in quantum gravity, and why all the slogans involving Popper are just ideological garbage for dimwits. The hurdle isn't ignorance of some obscure technical feature of M-theory. The obstacles are much more fundamental – most of the readers of the Quanta Magazine have unlearned what science is (at least according to theoretical physics).
Nevertheless, the amount of people in "adjacent disciplines and cultures" outside high energy physics who have read this garbage e.g at W*it's website and in the frequently equivalent pop science press has been large. I have repeatedly asked these people: Do you realize that only malicious, intellectually worthless subhuman filth visits that website? Some of them didn't even know that. And the number of times when this weblog (and indirectly I) was brutally insulted and placed on par with Peter Woit's hateful idiotic website was huge, too. You can't really build on such prerequisites, you can't pretend that these thousands of people haven't been downgraded to mental cripples. They have been. You have ignored some 1,000 moves that have led to this outcome and you can't fix it by one or several introductory articles.