The following seem likely to me: (1) Consciousness exists, and is not an illusion that doesn't need explaining (a la Daniel Dennett), nor does it drop out of some magical part of physical theory we've somehow overlooked until now; (2) Mind-matter interactions do not exist, that is, purely physical phenomena can be perfectly explained by appeals to purely physical theories.
Such are the stakes of "naturalistic dualist" thinkers like David Chalmers. But if this is the case, it implies that the physics of matter and the physics of consciousness are orthogonal to each other. Much like it would be a nightmare to stipulate that dark matter is a purely gravitational interaction and that's that, it would be a nightmare to stipulate that consciousness and qualia arise noninteractionally from certain physical processes just because. And if there is at least one materially noninteracting orthogonal component to our universe, what if there are more that we can't even perceive?
I think every tick is predictable from previous state. Inevitable. Therefore I really like how you put it: mind is just spectating.
If a rock starts moving in one tick, it affects other things in the next tick. Despite being deterministic, that rock is not a spectator.
So if the mind is a spectator, it's not for that reason, it's some other reason.
The "spectator mode" thing you replied to was a totally different concept, where the "mind" is some weird parasite to your brain and you'd walk and talk the same even if you didn't have a "mind". Which is quite a weird idea in my opinion.
Our brain needs to sense our "inner talk" so we can let it guide our decision-making and actions. If we couldn't remember sentences, we couldn't remember "facts" and would be much worse for that. And talking with our "inner voice" and hearing it, isn't that what most people would call consciousness?
I agree with the poster (and Daniel Dennet and others) that there isn’t anything that needs explaining. It’s just a question framing problem, much like the measurement problem in quantum mechanics.
If it’s completely impossible to even imagine what the answer to a question is, as is the case here, it’s probably the wrong question to pose. Is there any answer you’d be satisfied by?
To me the hard problem is more or less akin to looking for the true boundaries of a cloud: a seemingly valid quest, but one that can’t really be answered in a satisfactory sense, because it’s not the right one to pose to make sense of clouds.
I would be very satisfied to have an answer, or even just convincing heuristic arguments, for the following:
(1) What systems experience consciousness? For example, is a computer as conscious as a rock, as conscious as a human, or somewhere in between? (2) What are the fundamental symmetries and invariants of consciousness? Does it impact consciousness whether a system is flipped in spacetime, skewed in spacetime, isomorphically recast in different physical media, etc.? (3) What aspects of a system's organization give rise to different qualia? What does the possible parameter space (or set of possible dynamical traces, or what have you) of qualia look like? (4) Is a consciousness a distinct entity, like some phase transition with a sharp boundary, or is there no fundamentally rigorous sense in which we can distinguish each and every consciousness in the universe? (5) What explains the nature of phenomena like blindsight or split brain patients, where seemingly high-level recognition, coordination, and/or intent occurs in the absence of any conscious awareness? Generally, what behavior-affecting processes in our brains do and do not affect our conscious experience?
And so on. I imagine you'll take issue with all of these questions, perhaps saying that "consciousness" isn't well defined, or that an "explanation" can only refer to functional descriptions of physical matter, but I figured I would at least answer your question honestly.
(1) is perhaps more of a question requiring a strict definition of consciousness in the first place, making it mostly circular. (2) and especially (3) are the most interesting, but they seem part of the easy problem instead. And I’d say we already have indications that the latter option of (4) is true, given your examples from (5) and things like sleep (the most common reason for humans to be unconscious) being in distinct phases with different wake up speed (pun partially intended). And if you assume animals to be conscious, then some sleep with only one hemisphere at a time. Are they equally as conscious during that?
My imaginary timeline of the future has scientific advancements would lead to us noticing what’s different between a person’s brain in their conscious and unconscious states, then somehow generalize it to a more abstract model of cognition decoupled from our biological implementation, and then eventually tackle all your questions from there. But I suspect the person I originally replied to would dismiss them as part of the easy problem instead, i.e. completely useless for tackling the hard problem! As far as I’m concerned, it’s the hard problem that I take issue with, and the one that I claim isn’t real.
Animals are clearly conscious in that they observe the world and react to it and even try to proactively manipulate it.
The next level of consciousness, and what most people probably mean when they use the word is human ability to "think in language". That opens up a whole new level, of consciousness, because now we can be conscious of our inner voice. We are conscious of ourselves, apart from the world. Our inner voice can say things about the thing which seems to be the thing uttering the words in our mind. Me.
Is there anything more to consciousness than us being aware that we are conscious? It is truly a wondrous experience which may seem like a hard problem to explain, hence the "Hard Problem of Consciousness", right? But it's not so mysterious if we think of it in terms of being able to use and hear and understand language. Without language our consciousness would be on the level of most animals I assume. Of course it seems that many animals use some kind of language. But, do they hear their "inner voice"? Hard to say. I would guess not.
And so again, in simple terms, what is the question?
The average person may not know the word qualia, but “is your red the same as my red” is a popular question among kids and adults. Seems to be a topic we are all intrinsically curious about. But from a physical point of view, the qualia of red is necessarily some collection of neurons firing in some pattern, highly dependent on the network topology. Knowing this, then the question (as it was originally posed) is immediately meaningless. Mutatis mutandis, same exact argument for consciousness itself.
Evolution just had to give us some way to "feel", to be conscious, about some things causing us pain while other things cause us pleasure. We are conscious of them, and I don't think there's any "hard question" about why we feel them :-)
And when your fingers type that you experience qualia, are they bullshitting because your fingers have never actually received any signals from your consciousness in any direct or indirect way?
Imagine trying to figure out what is happening on someone's computer screen with only physical access to their hardware minus the screen, and an MRI scanner. And that's a system we built! We've come exceedingly far with brains and minds considering the tools we have to peer inside.
deepak chopra may interest you
There's a more straightforward problem, which is that all of science is limited by our ability to generate and test mental models, and there's been no research into the accuracy and reliability of our modelling processes.
Everything gets filtered through human consciousness - math, experiment, all of it. And our definition of "objective" is literally just "we cross-check with other educated humans and the most reliable and consistent experience wins, for now."
How likely is it that human consciousness is the most perfect of all possible lenses, doesn't introduce distortions, and has no limits, questionable habits, or blind spots?
But this might be easier to read: https://www.space.com/astronomy/black-holes/did-astronomers-...
It really fits well with the OP comments. Nothing really contradicts the theory but there's no deeper theory beyond it. Another comment mentioned as "nightmare" of dark matter only have gravitational interaction with other matter. That would be very unsatisfying for physicists but wouldn't something that really disprove any given theory.
You'd expect that at the bottom, the smallest objects would be extremely simple and would follow some single physical law.
But the smallest objects we know of still have pretty complex behavior! So there's probably another layer underneath that we don't know about yet, maybe more than one.
For a historical analogy, classical physics was and is sufficient for most practical purposes, and we didn't need relativity or quantum mechanics until we had instruments that could manipulate them, or that at least experienced them. While I guess that there were still macroscopic quantum phenomena, perhaps they could have just been treated as empirical material properties without a systematic universal theory accounting for them, when instruments would not have been precise enough to explore and exploit predictions of a systematic theory.
This allowed experiments where the frequency of light was varied continuously, by rotating the prism.
Moreover, already during the first half of the 19th century, it became known that using gas-discharge lamps with various gases or by heating certain substances in a flame you can obtain monochromatic light corresponding to certain spectral lines specific to each substance. This allowed experiments where the wavelength of the light used in them was known with high accuracy.
Already in 1827, Jacques Babinet proposed the replacement of the platinum meter standard with the wavelength of some spectral line, as the base for the unit of length. This proposal has been developed and refined later by Maxwell, in 1870, who proposed to use both the wavelength and the period of some spectral line for the units of length and time. The proposal of Babinet has been adopted in SI in 1960, 133 years later, while the proposal of Maxwell has been adopted in SI in 1983, 113 years later.
So there were no serious difficulties in the 19th century for using monochromatic light. The most important difficulty was that their sources of monochromatic light had very low intensities, in comparison with the lasers that are available today. The low intensity problem was aggravated when coherent light was needed, as that could be obtained only by splitting the already weak light beam that was available. Lasers also provide coherent light, not only light with high intensity, thus they greatly simplify experiments.
Incompleteness is inherent to our understanding as the universe is too vast and endless for us to ever capture a holistic model of all the variables.
Gödel says something specific about human axiomatic systems, akin to a special relativity, but it generalizes to physical reality too. A written system is made physical writing it out, and never complete. Demonstrates that our grasp of physical systems themselves is always incomplete.
An environment living in Conway’s Game of Life could be quite capable of hypothesizing that it is implemented in Conway’s Game of Life.
Systems can hypothesize about themselves but they cannot determine why the rules they can learn exist in the first place. Prior states are no longer observable so there is always incomplete history.
Conway's Game of Life can't explain its own origins just itself. Because the origins are no longer observable after they occur.
What are the origins of our universe? We can only guess without the specificity of direct observation. Understanding is incomplete with only simulation and theory.
So the comment is right. We would expect to be able to define what is now but not completely know what came before.
"The universe is not required to appeal to your aesthetic tastes."
That presupposes that there's a bottom, and that each subsequent layer gets simpler. Neither proposition is guaranteed, indeed the latter seems incorrect since quantum chromodynamics governing the internal structure of the proton is much more complex than the interactions governing its external behavior.
"in the specific regime covering the particles and forces that make up human beings and their environments, we have good reason to think that all of the ingredients and their dynamics are understood to extremely high precision"[0]
Sean Carroll's own favorite topics (emergent gravity, and the many worlds interpretation) are also things that we don't have any clue about.
Yes there is stuff we can calculate to very high precision. Being able to calculate it, and understanding it, are not necessarily the same thing.
Part of the problem is that building bigger colliders, telescopes, and gravitational wave detectors requires huge resources and very powerful computers to store and crunch all the data.
We're cutting research instead of funding it right now and sending our brightest researchers to Europe and China...
For just about anything else, Newton has us covered.
The argument is that these kind of distinctions between how "classical" and "quantum" physics affects our lives is just a pointless endeavor that even academics don't waste their time with.
Nothing major.
We are finding local maximums(induction) but the establishment cannot handle deduction.
Everything is an overly complex bandaid. At some point someone will find something elegant that can predict 70% as good, and at some point we will realize: 'Oh that's great, the sun is actually at the center of the solar system, Copernicious was slightly wrong thinking planets make circular rotations. We just needed to use ellipses!'
But with particles.
This sounds like a distinction without consequence, but I think that's wrong. The sun is not special. It just has a lot of mass. If somebody learns: The earth orbits the sun-- They don't understand how two black holes can orbit each other. If somebody learns: The sun and the earth orbit their CM -- They will be able to understand that.
There isn't even a general physical theory of window glass -- i.e. of how to resolve the Kauzmann paradox and define the nature of the glass transition. Glass is one of man's oldest materials, and yet it's still not understood.
There's also, famously, no general theory for superconducting materials, so superconductors are found via alchemical trial-and-error processes. (Quite famously a couple of years ago, if you remember that circus.)
Solid-state physics has a lot of big holes.
The point being it's not at all clear what we might be missing without these impractical little mysteries that so far are very distant from every day life.
There exists a huge number of fundamental quantities that should be calculated from the parameters of the "standard model", but we cannot compute them, we can only measure them experimentally.
For instance, the masses and magnetic moments of the proton, of the neutron and of all other hadrons, the masses and magnetic moments of the nuclei, the energy spectra of nuclei, of atoms, of ions, of molecules, and so on.
The "standard model" can compute only things of negligible practical importance, like the statistical properties of the particle collisions that are performed at LHC.
It cannot compute anything of value for practical engineering. All semiconductor devices, lasers and any other devices where quantum physics matters are not designed using any consistent theory of quantum physics, but they are designed using models based on a great number of empirical parameters determined by measurement, for which quantum physics is only an inspiration for how the model should look like and not a base from which the model can be derived rigorously.
This is of course a brute-force approach. We currently lack, in all fields, theory for emergent properties. And the mass of the proton definitely is such.
Nevertheless, until now I have not seen anything that qualifies as "computing the masses".
Research papers like that do not contain any information that would allow someone to verify their claims. Moreover, such papers are much more accurately described as "fitting the parameters of the Standard Model, such as quark masses, to approximately match the measured masses", and not as actually computing the masses.
The published results of hadron masses are not much more accurate than you could compute mentally, without using any QCD, much less Lattice QCD, by estimating approximate quark masses from the composition in quarks of the hadrons and summing them. What complicates the mass computations is that while the heavy quarks have masses that do not vary much, the effective masses of the light quarks (especially u and d, which compose the protons and neutrons) vary a lot between different particles. Because of this, there is a very long way between a vague estimate of the mass and an accurate value.
The fundamental laws of chemistry have not been changed much by quantum physics, they just became better understood and less mysterious. Quantum mechanics has explained various cases of unusual chemical bonds that appeared to contradict the simpler rules that were believed to be true before the development of quantum physics, but not much else has practical importance.
Solid-state physics is a much better example, because little of it existed before quantum physics.
Nevertheless, solid-state physics is also the most obvious example that the current quantum physics cannot be used to compute anything of practical value from first principles.
All solid-state physics is based on experimentally-measured parameters, which cannot be computed. All mathematical models that are used in solid-state physics are based on guesses about how the solutions could behave, e.g. by introducing various fictitious averaged potentials in equations, like the Schroedinger equation, and they are not based on computations that use primary laws, without guesses that do not have any other justification, except that when the model is completed with the experimentally-measured values for its parameters, it can make reasonably accurate predictions.
Using empirical mathematical models of semiconductor materials, e.g. for designing transistors, is perfectly fine and entire industries have been developed with such empirical models.
However, the fact that one must develop custom empirical models for every kind of application, instead of being able to derive them from what are believed to be the universal laws of quantum physics, demonstrates that these are not good enough.
We can live and progress very well with what we have, but if someone would discover a better theory or a mathematical strategy for obtaining solutions, that could be used to compute the parameters that we must now measure and which could be used to model everything that we need in a way for which there would be guarantees that the model is adequate, then that would be a great advance in physics.
We use spectra to test QED calculations to something like 14 digits.
The spectrum of hydrogen (ignoring the fine structure) could be computed with the empirical rules of Rydberg before the existence of quantum physics. Quantum physics has just explained it in terms of simpler assumptions.
Quantum physics explains a great number of features of the atomic spectra, but it is unable to compute anything for complex atoms with an accuracy comparable with the experimental measurements.
The QED calculations with "14 digits" of precision are for things that are far simpler than atomic spectra, e.g. for the gyromagnetic ratio of the electron, and even for such things the computations are extremely difficult and error-prone.
Rather: there is no known closed-form solution (and there likely won't be any).
There’s an intrinsic physical limit to which you can resolve a spectrum, so arbitrarily many digits of precision aren’t exactly a worthy pursuit anyway.
Um, false? The fundamentals of chemistry are about electron orbitals (especially the valence ones) and their interactions between atoms to form molecules. All of my college chemistry courses delved somewhat into quantum mechanics, with the biggest helping being in organic chemistry. And modern computational chemistry is basically modeling the QED as applied to atoms.
The way we construct Hamiltonians is indeed somewhat ad hoc sometimes, but that’s not because of lack of fundamental knowledge. In fact, the only things you need are the mass of the electron/proton and the quantum of charge. Everything else is fully derived and justified, as far as I can think of. There’s really nothing other than the extremely low energy limit of QED in solid state devices, then it’s about scaling it up to many body systems which are computationally intractable but fully justified.
We don’t even use relativistic QM 95% of the time. Spin-orbit terms require it, but once you’ve derived the right coefficients (only needed once) you can drop the Dirac equation and go back to Schrödinger. The need for empirical models has nothing to do with fundamental physics, and all to do with the exorbitant complexity of many-body systems. We don’t use QFT and the standard model just because, as far as I can tell, the computation would never scale. Not really a fault of the standard model.
It's also kind of interesting how causality allegedly has a speed limit and it's rather slow all things considered.
Anyway, in 150 years we absolutely came a long way, we'll figure it that out eventually, but as always, figuring it out might lead even bigger questions and mysteries...
Why is quantization necessary for information storage? If you're speculating about a storage device external to our universe, it need not be constrained by any of our physical laws and their consequences, such as by being made up of finitely many atoms or whatever. It might have components like arbitrary precision real number registers.
And if you're speculating about a storage device that lives within our universe, you have a contradiction because it's maximum information capacity can't exceed the information content of its own description.
This is getting tiresome...
Consider e.g. neutrino masses. We have plenty of experimental data indicating that neutrinos oscillate and therefore have mass. This poses a problem for the standard model (because there are problems unless the mass comes from the Higgs mechanism, but in the standard model neutrinos can't participate in the Higgs mechanism due to always being left-handed). But whenever we do experiments to attempt to verify one of the ways of fixing this problem -- are there separate right-handed neutrinos we didn't know about, or maybe instead the right-handed neutrinos were just antineutrinos all along? -- we turn up nothing.
This again? It's only true if you insist on sticking with the original form of Weinberg's "model of leptons" from 1967 [1], which was written when massless neutrinos were consistent with available experimental data. Adding quark-style (i.e. Dirac) neutrino mass terms to the Standard Model is a trivial exercise. If doing so offends some prejudice of yours that right-handed neutrino can not exist because they have no electric and weak charge (in which case you must really hate photons too, not to mention gravity) you can resort to a Majorana mass term [2] instead.
That question (are neutrinos Dirac or Majorana?) is not a "contradiction", it's an uncertainty caused by how difficult it is to experimentally rule out either option. It is most certainly not "a problem for the standard model".
[1] https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.19.1264
[2] https://en.wikipedia.org/wiki/Majorana_equation#Mass_term
That is not a trivial problem at all. It certainly has not been solved, and it's possible experiments will say "Both the current ideas are wrong."
The matrix you are thinking of is presumably the PMNS matrix [1]. It's equivalent to the CKM matrix for quarks [2]. The purpose of both is to parametrize the mismatch between flavor [3] and mass eigenstates, not "to account for neutrino masses" or "explain their origin".
As far as the standard model is concerned, neutrino masses and quark masses all originate from Yukawa couplings [4] with the Higgs field. Adding such terms to Weinberg's original model of leptons is very much a trivial exercise, and was done already well before there was solid evidence for non-zero neutrino masses.
> it's possible experiments will say "Both the current ideas are wrong."
Assuming that by "Both current ideas" you mean Dirac vs Majorana mass, those are the only available relativistic invariants. For both to be wrong, special relativity would have to be wrong. Hopefully I don't need to explain how extraordinarily unlikely that is.
[1] https://en.wikipedia.org/wiki/Pontecorvo%E2%80%93Maki%E2%80%...
[2] https://en.wikipedia.org/wiki/Cabibbo%E2%80%93Kobayashi%E2%8...
[3] https://en.wikipedia.org/wiki/Flavour_(particle_physics)
https://arxiv.org/abs/2106.16033
That aside, a distinction should be made between
1) claiming that physics is pretty much done (what he's often accused of) and
2) pointing out factual errors in claims about the current state of knowledge (what I am doing).
If you absolutely must make flattering comparisons, may I suggest Feynman instead, especially on lying to laymen?
https://calteches.library.caltech.edu/51/2/CargoCult.htm
I should add that I am not in complete agreement with what he said in that speech: calling it "not essential to the science" strikes me as naive. Once you start juggling two standards of communication, you are on a slippery slope. If it's OK to lie to the funding public at large, what about politicians, funding bodies, colleagues in other disciplines competing for the same funding, journal editors asking you to review a rival's work in your own field? Where do you draw the line? Do you draw a line, or do you descend into a state of generalized charlatanry?
Edit: Doing some quick searching seems to indicate that giving neutrinos a bare mass term would violate electroweak gauge invariance? I don't know enough to evaluate that claim, or TBH really even to understand it. But I believe that's what I was thinking of, so maybe you can say how true and/or pertinent that is.
Giving any standard model fermion a bare mass term would violate electroweak gauge invariance. That was one of the problems with Glashow's electroweak model from 1961 [1]: he had the right symmetry group, but all particles had to be massless in order not to break it. Weinberg's contribution was to combine Glashow's proposal with Higgs' mass generation mechanism. It is done exactly the same way for any electroweak doublet, whether it's up quark and down quark or neutrino and electron.
[1] https://www2.physik.uni-muenchen.de/lehre/vorlesungen/sose_2...
But if that's correct then I'm confused what your objection is to what I said earlier. If a bare mass would violate electroweak gauge invariance, then instead the mass should come from the Higgs mechanism, but that has the problem of, where are all the right-handed neutrinos, then? Am I missing something here? If you can't just give the neutrinos a bare mass and call it a day (at least not w/o causing significant problems), but do in fact have to make a more significant modification like inventing sterile neutrinos or making them Majorana particles, I'd call that a "contradiction" rather than merely a "question", because no hypothesis so far is a good fit for all of what we see (searches for sterile neutrinos have come up empty, neutrinoless double beta decay remains undetected, and I assume nobody's ever observed violations of electroweak gauge invariance!). Or I guess there are more out-there hypotheses that are consistent with what we see in that they've yet to really be tested, but, y'know, nothing that's been really tested AFAIK.
Correct. That's the pattern we see in quarks, and also applying it to leptons works just fine. In practice, if you are a particle physicist doing calculations which happen to involve neutrinos, and you are not explicitly analyzing the effects of alternative mass generation mechanisms, you use Dirac masses for all fermions.
> but that has the problem of, where are all the right-handed neutrinos, then?
One of the patterns of the standard model is that only left-handed fermions have weak isospin [1] (the charge of the "weak" nuclear force). Their right-handed counterparts have all the same properties but zero weak isospin; they do not interact via the weak nuclear force.
If you take a left-handed neutrino, which only interacts via the weak nuclear force (and gravity), and apply that pattern to get the properties of a right-handed neutrino, what you're left with is a particle with the same mass and no other interactions than gravity. That makes it pretty hard to detect.
This is not a "significant modification" of the standard model: it's what you get if you apply the pattern followed by all other fermions.
It is sometimes argued that making neutrinos Majorana is more minimalistic, since it reduces the number of particles by eliminating right-handed neutrinos, but that ignores the cost of deviating from the default pattern. In information terms, it would take more bits to encode "use Dirac masses for all fermions except neutrinos, those are Majorana and there are no right-handed ones" than just "use Dirac masses for all fermions".
> searches for sterile neutrinos have come up empty
Those would be heavy neutrinos which get their mass from physics beyond the standard model. Plain vanilla standard model fermions have the same mass whether they are left- or right-handed, so quite small for neutrinos [2].
> neutrinoless double beta decay remains undetected
Those would be a signature of Majorana neutrinos.
Both your "contradictions" support the plain vanilla standard model, with all fermions following the same pattern.
[1] https://en.wikipedia.org/wiki/Weak_isospin
[2] https://en.wikipedia.org/wiki/Neutrino#Properties_and_reacti...
But that doesn't exactly seem like something it makes a lot of sense to argue over, now that we've identified the disagreement.
> Those would be heavy neutrinos which get their mass from physics beyond the standard model. Plain vanilla standard model fermions have the same mass whether they are left- or right-handed, so quite small for neutrinos [2].
Hm, is that true? I know these experiments can only detect certain mass ranges and IIRC you're right that they were looking for heavier ones, but my understanding was that they were not getting it from physics beyond "standard model plus right-handed neutrinos" (technically beyond the standard model but only a way that is necessary to even discuss the subject!), rather they were just getting it via the ordinary Higgs mechanism? (The bit you linked regarding this doesn't appear to contradict this?) Unless by "beyond the standard model" you just mean that the right-handed mass is different from the left-handed mass, in which case, well, see above, now we're just talking about what "the standard model" normally means.
I mean you say you're a particle physicist, so I guess you'd know -- when you talk to your colleagues, what do they think "the standard model" means with regard to neutrinos? That right-handed ones don't exist? Or that they do exist and have the same mass as their left-handed counterparts? At the very least all the popularizations I've seen (generally written by particle physicists) have said it means the former... you're really sure other particle physicists mean the latter? This may sound a little silly, but have you tried taking like a quick poll or anything to make sure?
I disagree. That has been the working definition of Standard Model for decades. All quarks and all charged leptons are known to have Dirac masses, which require both left- and right-handed components, so once it became clear that neutrinos have mass too, extending that pattern to them too was the obvious thing to do.
> in the history of physics that actually happened, "no right-handed neutrinos" got codified as the baseline
Again, I disagree. Weinberg introduced what you insist on calling "standard model" in a three-page letter, at a time when there was no evidence for neutrino masses. He correctly designed it as a minimal proof of concept, knowing full well that extending it would be trivial. For the same reason, his "model of leptons" did not even mention quarks; those were also not an established thing in 1967.
I can't imagine anyone seriously claiming that quarks are not part of the standard model. And yet, here I am having to explain for the umpteenth time that neutrinos working like all other standard model particles are part of what everybody competent means by standard model.
>> Plain vanilla standard model fermions have the same mass whether they are left- or right-handed, so quite small for neutrinos > > Hm, is that true?
Yes. A Dirac fermion has a left-handed component and a right-handed one. The Dirac mass term is what binds them together and makes them behave like a single particle with one mass. Set that mass to zero and you have two massless Weyl fermions. [1]
> Unless by "beyond the standard model" you just mean that the right-handed mass is different from the left-handed mass
Of course. Different masses for left- and right-handed components of a Dirac fermion is a contradiction in terms.
> I mean you say you're a particle physicist
Do I?
> the popularizations I've seen (generally written by particle physicists) have said it means the former
There is an unfortunate tendency in popularization to blur the lines between established knowledge and speculation (see Feynman's "Cargo cult science", linked elsewhere in this thread), and an understandable desire to make one's own subject look particularly exciting. If you are neutrino physicist (an intrinsically soporific activity which mainly involves staring for years or decades on end at large quantities of a transparent mass hoping to see a rare interesting event [2]) your best bet to achieve that is to push the "window into Beyond the Standard Model (BSM) physics" narrative. So you bring up the fact that neutrino masses are very small, point to the seesaw mechanism [3] as a possible explanation, and emphasize that massive right-handed neutrinos could be cold dark matter [4]. That's fine, although it's getting old and not looking as promising as it once did. What is not fine is stretching the truth to the point of breaking it by claiming that right-handed neutrinos are, by themselves, BSM. That is abject nonsense.
[1] https://en.wikipedia.org/wiki/Dirac_equation#Weyl_and_Majora...
[2] https://en.wikipedia.org/wiki/List_of_neutrino_experiments
I did physics at uni and kind of dropped out when it got too hard.
I've long guessed the incompatibility is because the maths is just too hard for human brains, though I'm probably biased there, and we'll get a breakthrough when AI can handle much more complex maths than us. Probably not so long till we find out on that one.
I once tried to write a simplified explanation for why a spin-2 quantum theory naturally results in something like general relativity and totally failed - man that stuff's hard.
I think that even if AI were to find a good unification of GR and QM, we wouldn't be able to test it. We might accept it without additional confirmation if it were sufficiently natural-feeling (the way we accepted Newtonian gravity long before we could measure G), but there's no guarantee that we'd ever be able to meaningfully test it.
We could get lucky -- such a theory might point at a solution to some of the few loose threads we get out of existing collider and cosmological measurements -- but we might not. We could be stuck wishing we had a galaxy-sized collider.
Back then, we thought our theory was more or less complete while having experimental data which disproved it (Michelson-Morley experiment, Mercury perihelion, I am sure there are others).
Right now, we know our theories are incomplete (since GR and QFT are incompatible) while having no experimental data which contradicts them.