80 years? I would date its birth as 1968-9 (Veneziano), it’s hard for me to imagine calling prior work than that as “string theory”. But never mind that—the bigger problem with this (quite common) argument is that everything about quantum gravity, not just string theory, has avoided testability because our other theories are too good, and because we’re limited to doing experiments on Earth with equipment built on human scales with human budgets, and that’s just not where quantum gravity would naturally make itself known. So really this argument just suggests we shouldn’t study quantum gravity at all. Maybe that’s your actual opinion—it’s a waste of time if we can’t access the Planck scale, we should table it all and sit on our hands until we can. But string theory really is quite interesting to study, stuff like AdS/CFT is just really surprising and magical when you get what it’s about, and it would be a real pity to not pay the meager salaries of theoretical physics just because of pessimism. String theory is so far from fully understood! It’s actually…really hard!
BtW I think you got this 80 years number from looking at the earliest date on the Wikipedia page. You might want to read it more carefully. Not everything leading up to string theory is string theory.
The kind of supersymmetry you’re referring to (global spacetime supersymmetry) is not required by string theory; this is a common misconception. Looking for super partners in a collider is actually only telling you about global supersymmetry, which unlike local supersymmetry is not a universal feature of string theory at low energy, in fact the opposite, it is probably non-generic. It so happens that a class of appealingly simple vacua do have this property, which led to some inappropriate optimism among string theorists that has entirely abated with more experiments. Unfortunately this has been widely misunderstood to rule out the whole enterprise of string theory, which is unreasonable for the reason stated above, it is much more likely to not see SUSY below the Planck scale. [0] (Unless you just like to mock string theorists for hoping that the universe would be kind to them.)
Also global supersymmetry has not been experimentally disproved (how would you do this, even?) but it is true that current or even near-term experiments are not nearly sensitive enough to get close enough to answering this definitively, which is obviously upsetting.
I mean the people and land area governed by the United States Constitution, a document that provides explicit protections against the kind of ethnostate policies you are so worried about.
America has a long history of successful integration of racial groups. Once upon a time, the Irish were extremely unwelcome in Boston, simply for being Catholics. Dozens of examples like this abound in American history. America is stronger than the countries you’ve listed because of the melting pot, not in spite of it. That’s because the selfishness you alluded to is contrary to a core American value: that a person is not defined by their ancestors’ virtues or sins, but by the content of their character. All the immigrants I know are fierce defenders of this principle.
It’s a pity some people can’t think of politics as possibly more than zero sum. A good policy should actually lift all boats. Middle America simply will not survive without more people and more economic activity, period. If native born children choose to move to the coasts, and no immigrants fill in the gaps, you’re not going to have the long-term prosperity you’re imagining.
Okay, I’ll tell you about my own research. From studying the way that geometric surfaces work in AdS, we conjectured a relationship between the stress tensor of QFT and entanglement entropy. This is because those quantities translate into geometrical analogs in the quantum gravity theory. We then proved this same relationship holds in some simple field theories and then other physicists proved it in the general case. So we learned something about non gravitational physics from gravitational physics. We study a specific, tractable case (AdS, mapping onto CFT) and then use it to learn about the general case (every QFT). That’s how physics works! You study the spherical cows. Eventually you learn something universal. All this is because I started with an open mind, and pursued the full consequences of AdS/CFT.
Your complaint about supersymmetry is like saying that Newtonian physics can’t work because objects are not rigid, continuous solid bodies. And yeah, that’s true, there are none of those in nature. Does that mean Newtonian physics is not useful? NO! It’s a model that’s useful. Is it wrong? Kinda. And the models that have unbroken SUSY are “wrong” too, in the same way. But the point is—-it’s obviously useful!
Please try to be open minded about string theory, especially if you wish to lecture about small-mindedness around MOND. Diminishing the real accomplishments of physicists doesn’t make other fields more likely to get funded—it makes it more likely that bureaucrats defund everyone. That’s the lesson of the SSC.
No, this is a shallow understanding of AdS/CFT. If you want to study quantum gravity when it is weakly coupled to matter, you can use AdS/CFT regardless of whether the background space is asymptotically AdS by embedding a brane near the boundary and working in a perturbative expansion. If you want to study the physics of quantum de Sitter space with a field theory dual, you can study any of the recent work on TTbar deformations. And anyway, surely you aren’t arguing that conformal field theories are irrelevant for physics? Because that would obviously be an untenable position, and the whole point is that quantum gravity AdS (basically) is CFT (it’s an equality! It goes both ways), just in different variables. You can actually study non-gravitational physics with it, using a gravitational language. That’s awesome stuff! Please don’t dismiss this fascinating field too quickly.
By the way, I know Oppenheim personally. He gets funding from string grants. Nobody is angry about that. Anybody can do this. I don’t think his theory is going to pass any experimental validation (it requires a really severe violation of a physical principle we have tested over and over) but the entire community has always supported and listened. He gives talks at major universities. He’s not an outcast or renegade or something.
There are in fact exceptionally strong incentives to discover alternatives to quantum gravity which could be tested in experiments. These are the same incentives that always drive the scientific process, and new theories cost next to zero to produce. The reason string theory is popular is not because string theorists somehow prevent funding of other directions. It is because string theory has given us tools like AdS/CFT that are useful in other contexts to understand real physics—-and the alternatives have not (yet). There are many physicists who spend their lives studying alternatives to string theory with 100% of their time. I hope for their sake that there is a similar pot of gold at the end of their rainbows. It has not yet materialized.
Is your preferred remedy that quantum gravity be entirely defunded, or instead that more funding be redirected to any of the other programs to study quantum gravity? If the latter, which ones in your opinion are more likely to be productive than string theory?
You would probably learn more by listening to Cumrun Vafa [0] than anything I could say. It’s hard to say much about string theory without space time supersymmetry not because it doesn’t exist (we know it does) but because it’s so hard to calculate anything…physicists are very reliant on a few tools, supersymmetry is a big one, and without it it’s really hard to say anything concrete, yet.
You mean, if string theory does not turn out to describe the universe, how could it be useful? Well, by giving extraordinarily powerful tools for understanding things that are well established to be useful, like quantum field theory. AdS/CFT gives us the only tool we have to analytically understand quantum field theories in the so-called “strong coupling regime”. This is useful for discovering new properties of quantum matter in systems where you would otherwise need simulations. You can think of it intuitively as string theory providing a glue between two descriptions of the quantum matter, like a “type cast” in programming where you start with one kind of object but reinterpret it as another. The thing that is incomprehensible in one representation is simple in the other. This was discovered by studying limits of string theory in interesting geometries.
To whom? To other branches of physics? Look up AdS/CFT. To the general public? Dunno, I guess the pursuit of understanding the universe is its own reward for some.
There are exactly zero free parameters in string theory [0]. The details of why string phenomenology is hard is a difficult subject, but the characterization you've given of it is not correct. If you have a proof that string theory is not self-consistent, you should publish it, because there is no such proof in the scientific literature today. (Source: my PhD in physics.)
Unfortunately, there is a ton of misinformation about this topic on the web. For example, people love to say that string theory predicts anything and everything. But it predicts (and rejects) a lot; it’s just that all of the known predictions happen to fall into the categories of (1) predicting things that are very hard for humans to measure (behavior of black holes at long time scales, graviton scattering, etc) or (2) retrodicting things we already know are true (e.g. gravity, Lorentz invariance, etc.). This state of things isn’t by design of nefarious string theorists designing their theory to be untestable, it’s just cruel fate of what comes out of the math. Hopefully someday we can find some other type of prediction, but string theory isn’t easy.
Most quantum computer experts think that this is not the case, that it is very unlikely that quantum computers can solve NP-complete problems like travelling salesman more efficiently than classical computers. (In particular, the popular intuition that quantum computers “try a lot of solutions in parallel” is basically totally wrong, at least from the perspective of making a useful heuristic for what quantum computers are good for.) This is an older article, but its conclusions are still about right: https://www.cs.virginia.edu/~robins/The_Limits_of_Quantum_Co...
This is one of those things that laymen often misunderstand, actually. (I don’t blame you, it’s often not well explained.) General relativity is easy to make into a QFT. There’s an action and you can easily derive amplitudes from it. And it works well, as long as you don’t ask questions of what happens at arbitrarily high energies. That’s what “nonrenormalizable” actually means: it only answers questions up to some energy scale, after which it stops being predictive. But believe it or not, physics has been here before, so we’re not totally clueless what to do! Fermi’s theory of beta decay [0] had the exact same problem. And the moral there was that there was something new that had been missed in Fermi’s theory that was only important at high enough energy. The theory was correctly predicting its own limitations. In fact we figured out what was missing. Fermi didn’t know about the W boson, and at the energy where W boson exchange becomes important, that’s where the old theory breaks down!
But Fermi’s theory works well up to that scale. It’s like how Einstein’s relativity didn’t mean that everything in Newtonian physics was totally wrong, but just that you need it if you want to think about really fast moving objects. Newton’s theory is still an outstandingly good approximation.
So if history is any guide, we don’t need to change the low energy theory of GR (at least not much), that works just fine. We just have to find out what’s the high energy phenomenon that we’re missing. That’s stuff that comes into play with black holes and very high energy collisions. Anyway we have some guesses here, too. In string theory, that’s the stringyness of the strings, their 2D nature, that fixes the problems automatically. (This was not by design, it was completely unexpected! You start playing with dimensions and it just falls out.) In LQG it’s about the fuzziness or discretization of space (which sounds appealing, although it’s really tough in practice to make this work).
I think it proves my point that AdS/CFT is hard to talk about :) I’ve still got mixed feelings about the lamp/shadow analogy but thanks for the clarification.