Weinstein says that in the recent 40 years, we've made a big progress in "mathematics of field theory" which was good for quantum field theory and general relativity. OK, one could perhaps summarize the progress in this way although I wouldn't. But in the following sentence, he complains that
we ended up geometrizing the quantum rather than quantizing gravity which we had wantedand that's supposed to be "disappointing" because physicists only got a "golden age of mathematics of theoretical physics" rather than "golden age of theoretical physics". Wait a minute, this is quite a statement that deserves some commentary.
First of all, the opinion that "what we want is to quantize geometry" is a naive view of a mediocre undergraduate student or a crackpot who was told by his instructor: Sit down, be quiet, be obedient, and simply mechanically place a hat above every classical degree of freedom. If you place the hat really nicely and symmetrically, you will arrive at the quantum theory of gravity which is obtained from the classical theory by this straightforward procedure of "quantization".
"If you place the hat really nicely," the instructor continued, "you may not only earn an A but also become a professional theoretical physicist and maybe a new Einstein."
As Weinstein has correctly observed, this is not what happened. The people who have this idea about quantum gravity – who believe that this should have happened and it would have been better – are unimaginative, misguided, unimpressive individuals who have misunderstood basically all the important lessons about the relationship between gravity and the quantum that we have learned in recent decades, indeed. They belong to the broader community of loop quantum gravity, spin foam, causal dynamical triangulation, and Garrett Lisi cranks who simply aren't good physicists – they just love to star as them in front of the totally misinformed laymen reading the low-quality contemporary mainstream media.
Some quantum theories may be obtained by the process of quantization. For example, the quantum harmonic oscillator, hydrogen atom, other atoms, and most perturbative quantum field theories are more or less "uniquely" obtained from the combination of their classical limit and the universal principles of quantum mechanics. In some sense, the special information needed to define the particular quantum theory is already obtained in the classical theory. The quantum theory is an appendix, a derivative of its classical counterpart.
But that's only good for the situations from undergraduate textbooks.
Quantum theory isn't just some decoration of a classical theory. A quantum mechanical theory is "the main" player, the standalone and self-sufficient entity, and the right way to describe the relationship between the corresponding classical and quantum mechanical theory is that
the classical theory is a classical, \(\hbar\to 0\) limit, of the quantum theory.The quantum mechanical theory is the main theory and, by the way, you may sometimes find the \(\hbar\to 0\) classical limit in the parameter space of the quantum mechanical theory – and/or the situations that it describes. I said sometimes because it's not even true that every quantum mechanical theory has a classical limit. Also, a quantum mechanical theory may have several classical limits. QED may be said to have the classical limit in the form of classical electrodynamics; but it also has a classical limit of mechanics of high-energy photons (that no longer exhibit the interference phenomena in practice because their wavelength is too tiny).
The (2,0) theory in six dimensions is an example of a theory that can't be obtained as a quantization of a classical theory, at least not in a known way that would know about all the properties of the (2,0) theory that have been established. In the realm of quantum gravity, 11-dimensional M-theory is the most far-reaching example of a theory that isn't any "quantization of a classical theory". Also, the Seiberg-Witten treatment of \(\NNN=2\) supersymmetric gauge theories in four dimensions involves monodromies on the moduli space that don't exist in the classical theory. Because weakly coupled regimes are exchanged with others under the monodromy, one may say that it's impossible to take any universal \(g\to 0\) classical limit of the quantum theory.
And this is just the beginning. The actual insights about the role of quantum mechanics in many theories that have been uncovered in recent 40 years are much deeper, more diverse, and more numerous. The idea that a quantum mechanical theory is just an appendix of a classical theory, and the task for a theoretical physicist is just to "place hats" i.e. "quantize" a classical theory in a nice way, has been proven to be utterly childish. I insist that everyone who still imagines the relationship between classical and quantum theories in this way hasn't gotten beyond basic undergraduate courses that depend on quantum mechanics and he has misunderstood the profound lessons of theoretical physics of recent 40 years completely and entirely.
Now, Weinstein has complained that we learned something I described above – instead of learning what he had wanted to learn, namely that it's enough to place hats on some heads and you may consider yourself a genius. It's "disappointing", we hear from Weinstein. Whom is it disappointing for? It's surely disappointing for mediocre physics students who just believed that their narrow-minded undergraduate ideas "what is enough to pass a course" are also enough to learn about the deepest secrets of the Universe. Sorry, Eric, but those aren't enough.
More generally, the very idea that "one should have learned exactly what he had wanted to learn from the beginning, otherwise he is disappointed" shows Weinstein's fundamentally anti-scientific approach to the truth. It's the whole point of the research, especially scientific research, that the researchers don't know the answers to start with. If they had already known the answers to all the deep questions, the research would be a meaningless and worthless waste of time. Researchers not only often learn something else than they have expected and they figure out that they were way too naive or overlooked something; true physicists are really happy whenever that happens. Weinstein has neither the brain nor the heart of a physicist because he feels disappointed in these situations when something profoundly new and game-changing is actually learned.
What we have learned about the roles that quantum mechanics plays within particular quantum mechanical theories is amazing. And every person who has both talent and heart for theoretical physics is absolutely stunned by these advances and realizes that they have changed our view of the Universe forever and irreversibly. It's too bad that Eric Weinstein doesn't belong among these natural talents but there's no easy fix here.
To focus on another sentence by Weinstein, he says that it's "disappointing" that the progress occurred "only in mathematics" and "not in physics". I am sorry but by such propositions, and Weinstein has repeated them many times, he shows that he's very close to pseudointellectual garbage like Sabine Hossenfelder's "lost in math". In fact, the main point – of Ms Hossenfelder, Mr Horgan, Mr Weinstein, and even Mr Smolin, and probably others – seems to be exactly the same. Mathematics cannot be deep and it cannot matter for the truly important questions. Those must be decided and settled by some philosophical powers that transcend mathematics. So it's right to sling mud on everything that requires quasi-rigorous, careful, mathematical thinking. Hossenfelder, Horgan, Weinstein, Smolin, and others don't like it. Mathematics cannot become a king. It's at most a slave whose duty is to design hats of the nice shape for the real bosses who don't even have to know the relevant mathematics well.
I am sorry but this is complete hogwash. Mathematics is absolutely essential in theoretical physics. It's been essential since the very beginning – when Isaac Newton established physics as we know it and had to invent some branches of mathematics, especially calculus, to make it possible. And the importance of mathematics has only increased since the times of Isaac Newton. Of course mathematics plays an even more decisive role in theoretical physics than it did during Newton's life. It is the real king of the occupation – mathematics is both the creative and bold genius that looks for new ideas and fresh ways to organize them and connect them; as well as the final impartial arbiter that decides which ideas have to be eliminated.
If you want to look for important ideas in theoretical physics without mathematics, you're guaranteed to fail, Eric. If you want to separate the right ideas from the wrong ones without mathematics, you're bound to be a failed, unfair judge whose verdicts are uncorrelated to the truth – or worse. Equally importantly, the "progress in theoretical physics" and the "progress in the understanding what mathematics means for theoretical physics" are really exactly the same thing. If you don't get it, you're simply trying to do some theoretical physics that has nothing to do with mathematics – i.e. nothing to do with the careful thinking and the sophisticated delicate structures that have dominated theoretical physics for a very long time. You simply cannot get anywhere with this layman's attitude.
Mathematics is ultimately a vital language in theoretical physics that only expresses some principles, ideas, or laws in a rigorous and reliable way. But the principles, ideas, or laws have to be there in physics – so they are physical in character. Mathematics is needed to say what those exactly are; and it's needed to decide whether they're right, too. But as long as we talk about principles, ideas, and laws of physics, they are physical even if we need an arbitrary hardcore mathematical language for them to be described, commented upon, or predicted.
A simple example. The \(\NNN=4\) gauge theory in four dimensions has the \(SL(2,\ZZ)\) S-duality group. I chose this example because it uses some mathematical objects and notation such as the symbol \(SL(2,\ZZ)\) for a discrete group. So this duality group – found almost exactly 40 years ago – is an example of the progress in "mathematics of field theory" that Weinstein has acknowledged at the very beginning. But at the same moment, this group does immensely physical things with physical objects. It exchanges electrically charged particles with magnetic monopoles. Or it adds a multiple of the electric charge to the magnetic charge in order to redefine the latter. It maps limiting situations – simplified ways to discuss real situations – on each other, and so on.
The whole idea that there is a gap between mathematics and physics within theoretical physics and if you're on the mathematical side of this gap, you should be disappointed, is utterly idiotic. There is absolutely no gap at all. There cannot be any such gap in physics. A discipline with such a gap separating mathematics from the rest couldn't be physics and shouldn't be called physics. Mathematics is penetrating theoretical physics – it's absolutely everywhere. Mathematics is what the veins of theoretical physics are made of, and the blood that circulates through these veins of theoretical physics is made of mathematics, too. What other veins and bloods inside theoretical physics would you prefer, Mr Weinstein? Some P.R. blood? It surely looks so. Weinstein apparently prefers the role of mathematics that it plays in junk sciences (like the climate hysteria): authors of junk science paper love to include some mathematical symbols and jargon to make their paper look more scientific in the eyes of those who have no chance to understand anything, but this mathematical masturbation and related jargon has actually no impact on any of the key conclusions. This is not science.
Everything else that Weinstein says in the portion I have watched is wrong, too. At 2:10, we learn that the infinities in quantum field theory of the 1940s etc. were just a technical problem and led to no revolution. Sorry but this is also a delusion. The infinities were a proof that physicists really didn't understand what the theory was – and Eric Weinstein still misunderstands it, as I mentioned. In the 1970s, it was realized that the infinite terms are artifacts of some short-distance physics that may be undetermined but whose long-distance limit may be universal or determined by several parameters. This understanding of the so-called "Renormalization Group" was a revolution. It was a revolution showing the urgent need to think deeply about the mathematical objects and operations we do in physics, a revolution showing the inseparability of mathematics of physics. It was a revolution both in "mathematics of theoretical physics" and in "theoretical physics" itself – I have already mentioned that those are really the same – and Ken Wilson got a well-deserved 1982 Nobel prize for the Renormalization Group that has deeply affected both statistical physics (and thermodynamics) as well as quantum field theory, and showed their kinship, too. Many deep physicists quote the Renormalization Group as the most revolutionary insight of physics of the last 50 years. Weinstein's claim that "this was just a technicality and nothing revolutionary was there to learn" is both immensely ignorant and unbelievably arrogant. It's wrong and profoundly unethical for people who are this clueless about modern physics to pretend that they know something about modern physics.
The bulk of the actual value of theoretical physics as we know it today is composed of such profound principles and he seems to dismiss as well as misunderstand every single one of them.
Around 3:00, he suggests that string theory (and related insights) is "more sociological than physics". Holy cow, your brain is just a pile of šit. You're exactly on par of Ms Hossenfelder now. She got her physics PhD for her vagina and one is tempted to believe that Peter Thiel has teamed up with you for an analogous reason (believe me, this theory passes the first consistency check because two minuses give you a plus). Sorry but by saying something like that, you are falling to the deepest cesspools out there. If you believe that string theorists have been a secret cabal that actually doesn't do any solid physics and instead is playing P.R. games, you get it upside down. It's probably more comfortable for the likes of Mr Weinstein to believe such brutal conspiracy theories instead of accepting that he wouldn't have a chance to make it among the top theoretical physicists today – because not only he can't do research on string theory; he doesn't have a sufficient IQ to figure out whether the theory exists or is just a fairy-tale. I don't really believe you believe that conspiracy theory, Mr Weinstein, because you can't be that dumb. You know that it's complete nonsense – and on the contrary, it is šitty physics haters like you who are just doing cheap P.R. and impressing lots of extremely stupid people. This abuse of Big Think is an example of that.
Šit about contacts with experimental reality. String theory has understood everything we have experimentally observed – the GR and gauge theory limits of any viable stringy vacuum are enough for that. To go deeper, one simply needs to discuss things that cannot be reasonably expected to be observed in a foreseeable future. This fact is absolutely obvious – at least I had no doubts about it already when I was 15 or so – and if you have a psychological problem with the understanding of this trivial fact, you are the same kind of a moron as all those Horgans and others. I just hate when morons like that pretend to be smart.
I won't finish watching the last 70% of his rant because the first 30% has been more than enough for my adrenaline level. According to the headline in the HTML page at Big Think, I guess he must be saying that he's a new Einstein who finds a theory of everything by emitting these toxic, hostile, and idiotic lies for the moronic viewers, and I just don't have any duty to deal with this trash in its entirety. You suck, Eric.
We live in the era of the post-truth. I may know and every competent theoretical physicist probably knows that Eric Weinstein is just a clueless P.R. figure who is completely clueless about everything he comments upon – summary of last 40 years in physics and conceptual foundations of modern theoretical physics. But I can't change the fact that whole powerful corporations keep on brainwashing millions of people with anti-scientific vitriol by fake physicists such as Mr Weinstein. And I think that because the theoretical physics big shots have been so decoupled from these wars, they became almost completely incapable to influence the discourse, too – I guess that their influence is even well below that of my blog.