"Please don't post shallow dismissals, especially of other people's work. A good critical comment teaches us something."
"When disagreeing, please reply to the argument instead of calling names. 'That is idiotic; 1 + 1 is 2, not 3' can be shortened to '1 + 1 is 2, not 3."
I have a revulsion for the Dark Matter/Dark Energy thing, that seems to have become conventional thinking in recent decades. Those theories look to me like a tangled beard, just waiting for Occam's Razor.
FWIW, I'm also not enchanted by the theory of "cosmic inflation". I wonder if sterile neutrinos might eventually offer an alternative explanation for the unexpected smoothness of the MBR.
I don't understand why people think dark matter is "hairy." It's the simplest explanation imaginable - only one new particle. We used to discover particles all the time, and this idea that we somehow must have already found them all is a recent product of the end of accelerator growth.
I think it's "hairy" because it's not an explanation - the proposed particle is defined (more-or-less) as the error-factor in an equation. Show me the particle, I'll reconsider my views.
I know it sounds like a fudge factor that can be made to do anything, but the truth is that particle models of weakly interacting dark matter can only be made to do a few things. If any distribution of matter imaginable could be created through dark matter, you're right, that would be an empirical fudge factor, but only a few distributions of matter can be created this way, and it's noteworthy that one of them matches the one in real life.
An example of a limitless fudge factor is epicycles. They could be made to do anything - now through our understanding of the Fourier transform, we can make them draw elephants. That's not what CDM is like because it can't be made to draw elephants.
I didn't know that epicycles had the creative expressiveness to generate elephants, I'm impressed, and I'll have to dig into that - sounds interesting.
I thought that Ptolemy's epicyle ideas were defeated precisely because they were not able to explain observations.
[Edit] Hang on - so why can't you use epicycles to draw the actual orbits of planets? (modulo the n-body problem) If epicyles is equivalent to fourier, and can model any "ordinary" function, then I'm surprised someone hansn't made an epicycle model that's equivalent to the Newtonian model.
You can use epicycles to draw the actual orbits of planets. That's what "epicycles" are, or were: a fairly accurate model of the observed orbits of planets relative to Earth built through a composition of circular motions.
One way to think about it is that you start by modeling the motion as a simple circular orbit. You then look at how the observed data differs from your circular model and add an epicycle whose parameters minimize the difference between your new model and your observations. Repeat this process until you get as close as you want to get.
The success of heliocentric elliptic-orbit model isn't that it's able to represent something impossible with epicycles, but that it's dramatically simpler. Kepler's three laws are:
1) The orbit of a planet is an ellipse with the Sun at one of the two foci.
2) A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.
3) The square of a planet's orbital period is proportional to the cube of the length of the semi-major axis of its orbit.
In contrast, the epicycle models had 40-80 cycles with parameters tuned to match the observed data.
Kepler rule #2 never sunk in for me; the other two rules seemed fairly intuitive.
Kepler was Tycho Brahe's lab assistant, I think. Tycho was a curious chap. In addition to his brass nose, I believe he also had a "person of restricted stature" as a servant; that doesn't seem to be mentioned in his wikipedia article.
Epicycles were originally considered a good idea because it takes exactly two circles to make an ellipse, and Kepler's laws were satisfied by such an ellipse. They were "falsified,", in the two-cycle form, when closer observations revealed that Kepler's laws were not obeyed exactly. At that point, the choice was to either add more epicycles (working your way up to an elephant), or for Newton to discover universal gravitation.
The neutrino was discovered the same way. Conservation of momentum appeared to be violated, so we invented a new particle to save the conservation law.
Ironically, neutrinos are one type of dark matter. Hot dark matter.
I'm not saying that it's not a problem that we haven't seen cold dark matter in the lab yet. But the fact that dark matter sceptics are almost always not astrophysicists should tell you something.
Ah. No white lab-coat in the wardrobe. And I'm not an astrophysicist, might as well just flag me.
Look, I'm not a "sceptic"; that's like climate sceptic, i.e. non-believer zealot. I don't have a conviction about DM; I'm just waiting to be convinced.
I think most of us are waiting to be convinced. Current models don’t explain everything but the standard model and DM explain more than any competing theory so far. That’s why we keep investigating and theorizing to see if we can come up with something better. Eventually the current models are likely to be replaced by something else. We just don’t know yet if that something else is an extension of the current models or something out of the blue.
What would you prefer? For scientists to throw up their hands and say there’s a discrepancy whose cause is unknown but it sure looks like a weakly interacting particle?
Perhaps the problem with some people is in semantics. If that's the definition of dark matter, why not use a better term that means "something that influences things on galactic scales that we can't yet explain".
Calling it 'dark matter', implies or assumes that it must be only be what constitutes as 'matter' that's behind the cause. It closes many minds to considering the possibility that something that has no mass or volume could be behind the cause. You know something 'non-mattery'? And that begs the question, if has 'non-mattery' attributes in behavior, perhaps calling it 'matter' in definition is a bit misleading?
They'd prefer a bunch of particle experiments be constructed to approach the problem from a laboratory perspective, which frankly no reasonable person would mind. :)
I think it's because we aren't talking about some exotic, rare, or weakly interacting particle. We are talking about either an extremely common or extremely strongly interacting (or both) variant of matter which we somehow can't observe or produce in a lab despite observing much less common phenomena. It reeks of failures in other models.
Non-interacting means non-interacting with detection equipment, but it also means non-interacting with production equipment. Quantum mechanics is time-reversible, so "can't detect (absorb) it" = "can't produce (emit, i.e. absorption in reverse) it." It's a very parsimonious thing.
Yeah, but if dark matter exists, it clearly is NOT non-interacting. It should certainly be easier to detect than a massless neutrino (which we can detect convincingly now).
In particle physics, interaction with forces make roughly independent parameters. For example in a world with only electromagnetism, we would think neutrons were undetectable. The idea that there is a particle that only interactions gravitationally is hardly at odds with all of the other neutral particles we know.
Your point is correct, but the example is not good, because neutrons interact electromagnetically, due to having a non-null magnetic moment.
While the total electric charge of the quarks composing the neutron sums to 0, their movements are such that the magnetic effects do not sum to 0.
The particles that we know do not have a random collection of properties, they all belong to a consistent system.
For example in the set of 8 particles containing the 6 kinds of u and d quarks, the electron and the neutrino, the sum over the 8 particles of all the kinds of quantum numbers, e.g. spin, electric charge, color charge is null.
If some new particle interacting only gravitationally will be discovered, it will not fit in any way between the known particles so it must belong to some class of particles totally different from anything we know about until now.
Moreover, while it seems natural to assume that the dark matter if it exists must be composed of particles, like the matter we know, there is no evidence for this, so the dark matter might be some sort of continuous gravitational ether, for all we know.
I think you must have missed the conditional "would" in your parent comment's second sentence. Whatshisface was not writing about our world with our universe's physics. The "only" in his same second sentence is doing work there too, removing beta decay.
You could object that such a hypothetical world might not say something useful about our world, of course. I would not automatically agree with that assessment, however. It depends on whether "only" also ousts gravitation of free neutrons (or isotopes, if they exist in that world) or other means of testing the masses of bulk collections of matter with different neutron enrichment.
At the very least, we all seem to agree it was illustrative of a point about very weak interactions.
A gravity wave only interacts gravitionally right? And the energy it contains exerts a pull of its own? Say could you prevent one from escaping to infinity? Standing wave? Make it orbit something?
And I suppose even if it does escape to infinity it would be interesting to know if there is an analogue of the cosmic microwave background.
> I have a revulsion for the Dark Matter/Dark Energy thing, that seems to have become conventional thinking in recent decades. Those theories look to me like a tangled beard, just waiting for Occam's Razor.
IMHO, that's sort of what the end of science (or at least particle physics) will look like: detectable inconsistencies or anomalies with no means to probe further to resolve them, but new theories will keep getting produced and maybe even taught.
This might be one of the areas were probing further may not be possible:
> These possibilities make the dark sector “not just a bedtime story,” said Weiner. However, even if the dark sector exists and the familiar neutrinos act as intermediaries, there’s no guarantee that their link is strong enough to reveal what’s hidden. “It is possible that heavy [neutrinos] may be completely inaccessible to any reasonable experiment,” said Josh Spitz of the University of Michigan.
>This might be one of the areas were probing further may not be possible
I like this way of thinking. As a kid, I thought that everything could be figured out, eventually, in principle. Now I'm resigned to the prospect that there are things that can't ever be figured out.
I've already said that physics and cosmology are not my game. I'm just interested.
But perhaps it's worth noting: a cosmologist that wants to argue against e.g. DM is putting his career at risk.
If your career is cosmology or physics, and you want to rock the boat, you had better have some pretty surprising research, or you're going to have trouble. Look at the trouble Roger Pensose stirred up for himself; he's a big fish, but got seriously trashed over OR.
An interested bystander like me doesn't face those problems (except here).
> a cosmologist that wants to argue against e.g. DM is putting his career at risk
Academia doesn't work like that in all countries, at the very least.
Putting together a single-author or maybe two-author theoretical paper in gravitation or cosmology is commonplace, and getting it published is usually a lot easier than stopping oneself from throwing it out because of unsolved problems that almost inevitably creep up when one sets out to write down a non-trivial theory.
You don't really have to take my word for it. Start here: https://arxiv.org/list/gr-qc/new and observe the large number of one-and-two-author papers.
Then let's try https://arxiv.org/search/?query=mond&searchtype=all which by default sorts newest-first. The first four digits of the identifers are YYMM. You can see for yourself whether there are only few papers dealing with Milgromian/Modified-Newtonian-Dynamics gravitation, and work out some median author count.
If you do an in-browser search on that second results page you'll see "Famaey" a lot. Benoît Famaey's career in academia has hardly come to a dead end because of his many explorations of MOND over the past fifteen years or so; he's a Belgian working in Germany and France and indeed has grad students and a research team (cf. https://jobregister.aas.org/ad/deebea0f ), although not just for MOND to the exclusion of other areas of galaxy astrophysics. I think Famaey in his mid-50s or so, but I am not an especially good judge of people's ages.
Whether he could have had this sort of career in private universities in the U.S.A. is a sociological or political question that I decline to speculate about.
With minor effort at searching, you can certainly follow the publication lists and careers of his many collaborators, if you are tempted to argue that he is an especially rare or lucky individual to have avoided "hav[ing] trouble" or being "seriously trashed".
I would not read too much (bearing in mind I did not search deeply) into his recent coauthors being almost all from European universities, even if tempted into speculating about cross-juridictional comparative academy.
Finally, I'll end by pointing to Stacy McGaugh, an American at a U.S. university https://astronomy.case.edu/faculty/stacy-mcgaugh/ , has coauthored specifically about MOND alternatives to General Relativity and Dark Matter with Famaey and it does not seem to have wrecked his career, and neither have his rather forceful blog statements at https://tritonstation.com/ .
OK, too bad. I still think there are seriously-hard problems in cosmology that are not explained: DM, DE, and inflation. I'm not convinced by the explanations that are on the table.
Nobody has to convince me of anything, of course; I'm just some old dude with a laptop, and a long interest in cosmology. I just think there's something wrong: those three proposed mechanisms are very hairy, in Occam's Razor terms. It would be deliciously sweet, if the observations they purport to explain could in fact be explained by a single, simple theory.
My experience is that there is always something wrong with current theories, no matter what field or what time. We linger on the theories we find useful, but we never know how deep the rabbit hole goes, really, and there is always another surprise waiting to be revealed.
Good, let's start with that expression of interest and run with it.
Here's my high level challenge to let you reflect for yourself (privately) on how interested you really are.
> those three proposed mechanisms are very hairy, in Occam's Razor terms
Write down a standard gravitation-containing effective Lagrangian or the action on the one hand, and an alternative (see e.g. Famaey & McGaugh 2012 in Living Reviews in Relativity, 15, 10, §§6-7) and run it through your favourite character-counting tool.
Then try an analytical or numerical solution for a simple toy model in either of them.
Then tell us which one you think is hairy and why, and whether your idea about how to assess hairiness has differed during this little study programme.
There is local help available for you in doing this at a local community college or small state-funded university (or local equivalents) in the physics department. It won't take long to walk you through it at a STEM undergraduate level (I would start with the Einstein-Hilbert action with the cosmological constant and proceed to perturb that in small steps [1]), go deeper if you can follow the mathematics, and aim you at further resources if you are honestly interested in them).
I think this will be more satisfying for your intellectual curiosity than making self-admittedly uninformed negative comments on Internet forums (even this one).
I'm pretty sure that if you asked in the comments here you'd have several people offering to help put you in touch with someone local to wherever it is you are. Satisfying honest intellectual curiosity is catnip to academics.
> seriously-hard problems in cosmology that are not explained
Yes, you're right. Cosmologists collectively are working towards a consistent and complete and explanatory model, but are not done, despite the "corpses" of many many ruled-out possibilities. (It is easy to dream up a possibility, hard to write it down consistently, and almost always really easy to kill it on first contact with real astronomical data; Einstein went through this many times including on papers he sought to have published).
However, I think you can get closer to understanding what those problems are, and why they're hard, and what we know can't solve them, assuming you retain your interest.
> [DE] ... could in fact be explained by a single simple, theory.
The Cosmological Constant is literally just a scalar multiplier on the curvature. Practically the only way to make it simpler is to zero it out, which is exactly what had been done before the discovery of the apparent acceleration of the expansion of the universe. Dark energy research (on the theoretical side) is principally, "in order to improve the accuracy of our modelling compared to data from various observatories, do we need to change the Cosm.Const., which is the \Lambda in the \Lambda-CDM model, into a more complicated function? If we do so, what observables are generated (especially if they would appear in already-gathered data (e.g. DES)?". [See the parenthetical three paragraphs up...]
- --
[1] An actual lecture for grad students (and some undergraduates) at McGill University in Montréal has this section: https://www.youtube.com/watch?v=pjn_wZ-1ne0 (from https://www.mcgill.ca/study/2021-2022/courses/phys-514 ETA: n.b. at the 41min58sec mark re my approach above) Please feel free to reply in the comments about whether this is interesting but too difficult to follow, and I will try to aim you at something more suitable for you. (You also will probably find lots of HN commenters directing you at e.g. PBS Spacetime and similar, but I think that's not really a path to understanding what hairy even is). Really I'm guessing you'd be better off with an informal tutorial session, which might cost you a coffee and a decent sandwich brought to some physics teacher's office, and some diplomacy beforehand (don't start with "I want you to show me how to argue on the Internet about physical cosmology's failings", for instance, much less "give me a devastating 240-character slogan I can repeat until all the relevant physicists get different jobs or mute me").
> someone local to wherever it is you are. Satisfying honest intellectual curiosity is catnip to academics.
I live about a mile or two from Roger Penrose; I have wanted for years to ask him out for a beer. I believe he has views that are very interesting to me, that he hasn't published on (not his field). I know someone who knows him. But I'm terrified.
> what hairy even is
Several people have picked up on me using that word, and run with it. I was only using the word casually, to refer to something that looks like it could be cut with a Razor. I'm beginning to get the impression that it's sort of a technical term with an established meaning.
[Edit] I'm not sure if any such established meaning might be related to the observation that "black holes have no hair". I'm not using it that way, TTBOMK.
I didn't do maths past 18, so I'm not doing your math exercises (and you're rather obviously bandying jargon around for purposes of belittling). Doesn't matter.
Your opening remark hooked me; I thought you were going to tell me something interesting. Disappointment ensued.
Ok. I thought your comments were even more patronising, since you repeatedly discounted the work of many thousands of cosmologists around the world who did not stop maths at 18, and was provoked by them.
(Apart from writing this neat book, Wheeler is also the coauthor of one of the standard graduate-level textbooks on General Relativity.)
Unfortunately the book is fairly rare, but there are usually purchase options and a public library might have a copy, or could get one via inter-library lending.
I cannot gauge your level of interest other than that you expressed some; I also did not know until now, in spite of your disclaimer about not being a physicist (and being "an armchair cosmologist"), how little maths you have.
I'll end with a Feynman quote that seems relevant when gauging one's own interest in and ability to talk about a topic that one does not know well: "The first principle is that you must not fool yourself and you are the easiest person to fool."
I do not have an ebook reader. However I am working my way through Penrose's "The Road To Reality". I'm halfway though, it's taken me a couple of years so far.
I'm not up for doing graduate maths! Are people saying that you can't think about this kind of stuff, if you don't have graduate maths?
If one doesn’t understand a topic, what value is there in what one says about it?
That sounds like a mere dismissal, but let’s try to formulate an answer to it as an actual question.
For one thing, if a field is full of intentionally confusing/obfuscated nonsense, then hopefully one could legitimately refute it without understanding the nonsense. For example, if some variant of astrology, or some theory of literary criticism, is intentionally so difficult to grasp, that none but it’s advocates have taken the time to understand it, that should not prevent the field from being dismissed as pointless nonsense.
But what is the grounds on which such a dismissal should be based?
Well, in the case of astrology, you can find that whatever predictions it makes are not better than chance. You don’t have to understand how the theory works to evaluate this, you just need the predictions made by the practitioners.
In the case of a nonsensical theory of literary criticism, either it does not make any claims which have a meaning that can be evaluated outside of itself, in which case it can be dismissed as not saying anything that any non-practitioner would care about, or it does, in which case its merit can be judged, in part, based on those claims.
But suppose there is a theory (or related family of theories) which one finds too complicated to understand, but which the community around it(/around them) uses to make accurate predictions.
Can one then potentially offer useful criticism? In some cases, yes! If there is another theory which can be seen to make predictions or judgements which are just as good, or better, and such that one can give a strong argument that it is simpler, then one can put that forth as a good criticism.
But, note, one should have a clear idea of what one means by simpler, or at least, of the basis by which one concludes that the other thing is simpler.
Are there other cases that work? I think so, but suspect they are all, fairly limited in scope.
If a community is able to make predictions well using a theory which has few parameters (in an appropriate way of counting parameters. E.g. no splitting the digits up to turn two parameters into one.) and no community has another theory which makes comparably good predictions, I think that without understanding the theory, or at least without understanding some part of it well, one wouldn’t have many compelling avenues of criticism.
(If one is able to understand some small part of it well, one can potentially demonstrate that that small part of it seems to be e.g. obscurantism around a trivial point, or other issues with that small part. If one does this with a handful of very small parts this could be a quite compelling criticism, especially if no one is able to give a good justification for why it is said like that.)
Of course, one can think all one wants about whatever topic. There is nothing objectionable about anyone thinking about a topic.
But in presenting one’s thoughts, one should express an appropriate level of confidence based on how what one knows compared to what others know, about it.
When people (not like you. I’m not talking about you here. I’m thinking of comments I see on youtube videos) with no math background think that “quantum mechanics is too complicated. It must, therefore, be wrong.”, they are making a mistake.
I'm not trying to make a contribution to a scientific conference; I'm just some dude, trying to have a conversation with smart people, and so become better-informed.
I probably seem rather defensive; I'm no expert, and I know there are experts around here. I'm OK with being slammed down by experts. I can take the punches, I have nothing to prove. But I am sorry that those experts might be hurt by my remarks - I'm just some inquisitive dude on the internet, raising questions.
OK, so I do a new degree (so that I can talk to clever people). I'm 65 - not as nimble mentally as most mathematicians and cosmologists. I'll probably be dead in 10 years, so I'm not going to be doing interesting research.
I would like to be able to understand what experts think is how the Universe works. I think it's a duty on people to try to understand the world they live in; same as I think a citizen has a duty to try to understand government policy, even if they are not experts in political economy or whatever.
So I live in a town with a couple of good universities. I have an batchelor's degree in Philosophy. I did maths and advanced maths at 16, but bailed out after that. Surprisingly I got top grade in advanved maths, and bottom (pass) grade in regular maths. I doubt I'd get a place on a postgrad course in anything but Philosophy, and I got a poor grade in that (I think partly because of my option choices).
Which degree course should I sign-up for? I'm interested in number theory, logic, and cosmology. I'd particularly like to be able to talk to people about cosmology.
I don't need a first or anything; I'd only be doing it to educate myself.
Amusingly (I think), in my youth I took some astrology training. I read quite a bit on the subject, and attended a few classes. Obviously I had some pretty mad notions.
I'd like to think that the notions I have now are not bonkers; but past form says that I've been wildly wrong before, so the notions I have now are probably wrong too.
to be clear, I didn't mean to criticize anyone by comparing things to astrology (... except kinda some forms of literary criticism, but I shouldn't have done that, both because it was rude, and also because it was not a good comparison).
I was just giving cases of where something could make sense to really criticize without understanding it,
trying to get closer to a characterization of the situations in which that would make sense.
I certainly didn't mean to suggest that your current notions are "bonkers". I apologize if it came off that way. And, I mean that sincerely, not just in a "sorry if you were offended" way, but like, in a "if that was the way it came across (and it seems it was), then I am at fault, and I am sorry." way.
Even if you didn't take it that way, the way I wrote my comment was probably a bit harsh, and it shouldn't have been.
Certainly I don't have a good enough understanding of cosmology to defend any models of it on at the object level, and it seems to me that there are some that do, who have reasons they prefer non dark-matter (or, ... sorta-non-dark-matter?) explanations?
And I guess, some people from the people-who-understand-cosmology-well community will give simplified accounts for people without the math background for why they suspect their view (either for dark matter or not) will turn out to be the one that is right, and it makes sense that some people in the audience would be convinced one way or the other by some of these explanations.
So, now I realize something I am confused about:
If two experts (who, say, are both generally respected in a field, and who respect one-another) give for-popular-audience simplifications of their reasons for believing their opposing positions regarding a particular question in the field,
and if one of their positions is the more common, almost "standard", view in the field (but where the question isn't considered really settled, and basically everyone in the field agrees that neither is strictly ruled out)
but one finds the for-outsiders explanation of the less common position to be convincing, and the for-outsiders explanation of the more common position to be unconvincing,
what should one believe?
How should one weigh how convincing one finds the simplified versions of the arguments, against the fact that a substantial majority of the field finds the other view more likely?
I am genuinely unsure!
Maybe it depends on, the reason for the differences in how convincing one finds the simplified arguments?
> But suppose there is a theory (or related family of theories) which one finds too complicated to understand, but which the community around it(/around them) uses to make accurate predictions.
Whether there is a community is neither here nor there. What matters is the predictions. Quantum theory is incomprehensible, but makes super-precise predictions, that have been tested and confirmed. These three theories aren't like that, are they?
Good lord, you think that's jargon? No, that's table stakes for a discussion. What you're doing here is the equivalent of mouthing off about combustion engines and then admitting you don't know what a piston is.
You patronized the entire community of thousands of cosmologists who have trained their entire lives to think about this. They have had every thought you've had, but with much more knowledge and context. Do you not realize that?
If you are a professional science researcher, I think your job includes explaining to the rest of us what you have learned.
I don't think you are supposed to mock the rest of us, because we don't know as much as you know. I've never pretended to be anything other than an interested layman. I'm pretty surprised at the downvotes and hostility I've met.
I mean, I knew my opinions were unpopular; I expected downvotes, but not hostility.
If you don’t want that kind of reaction, phrase your point of view in a way that’s more curious and less with the tone and perspective of “those guys are clueless and wrong.”
I’m not a cosmologist. I don’t have a degree in physics. But when I read your comment, I was as upset as any of them would’ve been.
Alright, so perhaps my tone was ill-considered. I certainly don't think “those guys are clueless and wrong” - those guys are the people who worked out the stuff I think I know about the cosmos - not me. I'm dazzled by what they've done.
When I were a lad, the Big Bang theory was treated with scepticism; the orthodoxy was Hoyle's steady state. Big Bang is now orthodoxy, steady state is dead, and Penrose is out in the weeds. Similarly the idea of a black hole was considered pretty left-field. It's now more-or-less proved. These changes have happened in my lifetime.
My point is that what is considered orthodox can change in just a couple of decades; it's not insane to question whether an orthodoxy that's been in place for just a couple of decades (and is itself pretty speculative) should have the status of scientific fact.
I'd be a fool to think that modern cosmological theory is in any way a final answer. Sure, I wouldn't recognise a Lagrange equation if it slapped me in the face. Similarly, I'm not an economist; I can't prove that Friedman had the wrong end of the stick. But I can still make reasonable judgements about a government's economic policies, and my judgements are sometimes more right than those of experts.
> My point is that what is considered orthodox can change in
just a couple of decades;
There will clearly be more revolutions in physics over time. We know the Standard Model is are wrong. Dark Matter and Dark Energy may be right or wrong. We need more experimental evidence to help us decide. This is not a new insight that you've had. Literally every physicist knows this.
> it's not insane to question whether an orthodoxy that's been in place for just a couple of decades (and is itself pretty speculative) should have the status of scientific fact.
What makes you think that physicists think that anything that's been discussed is scientific "fact"?
More importantly, there is no value in you, me, or any layman without an even undergraduate-level understanding of math and physics questioning anything that you don't know a single thing about. You don't even know what you don't know, and despite your claims of humility, your earlier writings clearly demonstrated either incredible arrogance, naivety, or both.
> Similarly, I'm not an economist; I can't prove that Friedman had the wrong end of the stick. But I can still make reasonable judgements about a government's economic policies, and my judgements are sometimes more right than those of experts.
This analogy is wrong. I could go into why you probably didn't even understand why the experts believed what they believed, but I don't have time for that. Even a broken clock is right twice a day. And even if someone is wrong, their thought process could have been better and more informed than yours.
Your analogy breaks down because none of that has any bearing to cosmology. You don't understand any foundational knowledge required to even begin to have an elementary conversation. Saying "I don't buy these existing theories" is actually making a very strong statement, because it implies that you understand what the current theories are, why they are what they are, and all of the other theories that have been ruled out for various reasons. And if you don't know any of this, then your opinion is literally worthless in the epistemological sense.
When I was an undergraduate studying computer science, I met a graduate mathematics student at a programming competition. I asked him if he could explain his research to me. He said "no". I wasn't upset, nor did I tell him that his theories were wrong. Rather, I was enlightened. I realized that there was no way he could possibly explain the abstract concepts that he was studying to a person who barely understood linear algebra. It would have taken me years of hard studying to begin to be able to grasp the kinds of problems that he was tackling, the approaches that he was taking, and why. This is no different.
> More importantly, there is no value in you, me, or any layman without an even undergraduate-level understanding of math and physics questioning anything that you don't know a single thing about.
It's not something "I don't know a single thing about". I know some things about it. Perhaps I could observe (since we're on the topic of what people don't know) that you don't actually know what I do and don't know.
> You don't even know what you don't know,
I cheerfully concede that the number of things I don't know is infinite.
> and despite your claims of humility, your earlier writings clearly demonstrated either incredible arrogance, naivety, or both.
If it's "incredible", then you would appear to have a problem; it seems that you are convinced by my demonstration of arrogance and naivety, even though it's not believable to you. Make up your mind.
I've not insulted anyone; all I've done is to question certain ideas. You, on the other hand, have written a long comment that consists of nothing but personal insults, and contains no information.
Back in the Usenet days, one would have said <plonk>.
I know that there are only a few thousand professional cosmologists in the world - maybe only a few hundred.
I don't know why a professional cosmologist should feel patronised by some twat like me. Some people up-thread have had a go at explaining things; I've learned, and I have some study leads. I don't learn from patronising insults.
My understanding from following reports on these experiments (including this article) is that the simplest version of sterile neutrinos, where instead of three kinds of neutrinos there are four, and one interacts only gravitationally, has been ruled out, but maybe some more complex version is still possible.
Fortunately it is not up to armchair science enthusiasts to determine whether the evidence for dark matter or dark energy (which are unrelated concepts that share similar names) is sufficient to validate those theories. That would truly be a disaster.
Every time fundamental physics articles are posted on HN there's some commenters who say something like "I dunno about this dark matter stuff, even though I know basically nothing about it". It's the physics equivalent of being an anti-vaxxer: you have only a superficial idea of where ideas come from or why they're considered credible and you naively assume that the experts are in the same boat, and therefore it's you against them and you both have equally valid stances. The newsflash is: the experts on these subjects know _so_ much more about what they're talking about than you can possibly imagine in your armchair, and you have no idea the depths of the analysis they've done, or how comprehensive and repeatable the measurements were that led to these theories being taken seriously.
"...the Standard Model of particle physics, the well-tested set of equations describing the known elementary particles and forces, unequivocally deems neutrinos massless.
"Even scientists who backed the idea that neutrinos oscillate and have mass distrusted LSND’s numbers, because the inferred oscillation rate overshot the rate implied by solar and atmospheric neutrinos.
"Ever since the discovery in the 1990s that neutrinos have mass, theorists have wondered if neutrinos could account for the enormous amount of dark matter that seems to engulf galaxies. They soon concluded that the three known neutrinos don’t have anywhere near the mass needed to do so. But if a larger family of neutrinos exists — including some heavy ones — they might.
"The Standard Model predicts that electron, muon and tau neutrinos are massless — except they aren’t."
Is it not reasonable to express interest and hope for new discoveries when fundamental axioms are proven incorrect?
Interest and hope is fine. I was responding to the parent poster's stated revulsion for these theories -- and not just any of them but all of them, as though they have a blanket distrust in any unproven theory in physics, uncorrelated with the experimental evidence for it.
> fundamental axioms are proven incorrect
It's not that fundamental axioms are disproven so much as simplifying assumptions are invalidated. The standard model models the particles we understand well, and has obvious extension points for new physics (like new Lagrangian terms / new gauge fields). Nobody thinks that it models all of physics as written; it clearly doesn't account for lots of things.
True. I do have a revulsion; not like a vomit reflex, just that I don't like them.
It's not a "blanket distrust" - rather, it's that cosmologists are proposing three distinct ideas, each with very strong implications, none supported by more than what amounts to circumstantial evidence.
I just have an instinct that those three ideas might not be as distinct as they look.
My point in, uh, scolding you for that take is that the circumstantial evidence is _massive_ for each of them, and I ... have a feeling... that you do not appreciate that fact. (well! not for dark energy, but also nobody would disagree with you that dark energy isn't much of a theory. It's the other two that are well-founded in detailed experimental evidence).
For my part I don't think the evidence for dark matter is any more 'circumstantial' than the evidence for massive neutrinos or the Higgs. Both are well indicated in extensive data .. by their byproducts and effects on other matter. But neither has been 'seen directly'; indeed it's not even clear what it would mean to see them directly, given that they apparently don't interact via the forces we can directly detect.
> feeling... that you do not appreciate that fact.
Actually, I do; at least, I think that galaxies rotations are peculiar, but can be explained by the addition of unobserved matter. And I think inflation is a plausible candidate explation for the smoothness of the CMB. And I note the evidence that the universe's expansion appears to be accellerating, but I wonder is that is an observational error (rewally, I don't know - nobody I know is a physicist, or even interested in cosmology).
So I'm an armchair cosmologist; same as I used to be an amateur astronomer. We serve a purpose: amateur astronomers are usually the first to spot new comets, because they have a wide perspective.
I'd consume more material about cosmology, but it's generally either dumbed-down mass-media crap, or something about Lagrangians. I'm not a maths graduate, I did Philosophy. None of that invalidates my viewpoint.
Yeah, that pretty much confirms what I was getting at: you believe you understand the theory-scape here, and you think that unobserved matter could be a valid explanation, because you know nothing about this why it in't. You're not wrong to doubt them for yourself, or to have fun thinking about it, or whatever, but casting it as some kind of ossified 'conventional thinking' that we should all be distrusting of isn't okay, and sounds a lot like other types of weird science distrust that happen a lot these days.
Not entirely your fault, though; physics does a really bad job of, as, you say, educating people at a level more sophisticated than dumb-downed "because we said so" crap. But there know there are a lot of good youtubers and blogging filling in 'educated layperson' level of explanation.
> Actually, I do; at least, I think that galaxies rotations are peculiar, but can be explained by the addition of unobserved matter.
That was the original hypothesis. It's literally the first thing the theorists came up with. There's an anomaly -- the simplest explanation is there's more ordinary matter there that we can't see. But why can't we see it? Well, we see stars because they emit light, we see gas clouds because the reflect light, so there's gotta be more matter there that doesn't give off light. What do we call it? Well, it's matter, and it's dark, so let's call it dark matter.
Hypothesis 1.0, there's additional ordinary matter that is unobserved, was invalidated. It's one of the things that we know for certain is false. At this point, honestly, additional unobserved ordinary matter theory is about as credible as luminiferous aether theory for explaining the propagation of light. It's not a dumb idea -- "There's more stuff" is the simplest explanation, as is "Waves travel through a medium, so there must be a medium". But after more and more observations start piling up that are incompatible with the hypothesis, it's time to move on. Ordinary matter as an explanation for galactic rotation curves has been dead for about 40 years.
> Ordinary matter as an explanation for galactic rotation curves has been dead for about 40 years.
I wasn't aware of that; I didn't know that galactic rotation had been known to be peculiar for such a long time.
I also wasn't aware that DM isn't just an example of "more stuff". I mean, I realise that DM can't be like other stuff; from what I've heard, it doesn't block light like other cosmic dust, and it doesn't seem to obey the same gravitational rules as other galactic stuff.
I have no standing to tell experts they're wrong! But every lawyer knows that once the person you're talking to knows you're a lawyer, they'll start arguing with you about law. Lawyers often keep schtum about their trade, for that reason. So here I am, in a forum where there are people that know stuff, and I don't think it's wrong to ask questions.
The standard model in its normal form assumes neutrinos to be massless (and that right-handed neutrinos don't exist). Neutrino oscillation implies that they have mass (because to oscillate, they must have an 'internal clock', meaning that they experience proper time, thus are not massless). In light of the fact that they are not massless, some sort of additional term needs to be added to the standard model, but experiment has not provided a way to distinguish between (or invalidate) the candidate theories... yet.
The standard model has two parts -- a general schema for theory building (Lagrangians with terms corresponding to each symmetry field and each coupling between fields, plus symmetry breaking and the Higgs mechanism for conferring mass to (some of) the gauge bosons) -- and a particular set of choices within this schema, which is the specific Lagrangian + choices of constants that predict essentially all of the physics we've seen in particle colliders.
As far as I know, massive Neutrinos can be solved 'within' the SM schema, although additional Lagrangian terms are required. What's unclear is whether dark matter, gravity, fermionic masses, etc can be resolved within the same framework. But massive neutrinos don't _necessarily_ challenge it (although if the existing theories are ruled out, they might start to). Everyone is pretty much on board that the exact choice of Lagrangian terms can't completely describe reality, and needing to add terms doesn't mean invalidating the theory.
I have a puzzle for you. How would you distinguish, in hackernews-level informal (but still reasonably accurate) prose, flavour-changing oscillation and wave frequency in the sense of E=hf? Doesn't the latter frequency imply an internal clock even for photons?
(For fun we could attribute an extremely tiny mass to photons and repeat the question, bearing in mind this necessarily ousts the photon from its (affinely-parametrizable but not proper-time-parametrizable) null worldline.)
I don't know much about this off the top of my head, but roughly, the idea is that a neutrino we observe with a definite mass is a mixture of the three flavors, and a neutrino with a definite lepton flavor is a mixture of those with different masses.
The different masses mean that as a neutrino of a certain flavor travels its different constituent states evolve at different speeds, so what it is measured at have different chances of being measured based on when the measurement takes place.
Photons have no effect like this because they are not mixtures of different particles and have no concept of 'flavor'. Massive photons would be the same.
Unfortunately it is very hard to find a lucid explanation of the idea .. anywhere.. that isn't a bunch of 'just so' explanations.
The 'short version' is that a Lagrangian is a device for book-keeping the interactions in a physical theory. It consists of terms like aBa, where 'a' is some physical quantity, and (Ba) is the 'cost' to change it. B in general is an operator that can depend on all of the other physical quantities around, possibly including derivatives. So you end up with something like:
L = aBa + cDc + eFe + gHg + ...
Derivatives of this function with respect to a given variable -- for instance, a particular value `a` or `c` -- tell you the 'physical law' for that field. The simplest example in classical mechanics is L = 1/2mv^2 - V(x), and the derivative rule is dL/dx - d/dt dL/dv = - V_x - m dv/dt = (F - ma) = 0.
In general including a term like ... + cD(a)c +... causes the c field to couple to the a field, which is how interactions between different fields (represented by the lower-case variables a, c, etc here) are encoded in field theory.
I haven't found out a cogent explanation of why the terms have the form aBa, though, or why this is the 'simplest' way to express the concepts that it encodes, but it seems to be. But it works well in part because of it expresses physical laws in terms of scalar functions (instead of a vector-equality like F=ma, which becomes a complicated differential equation in practice), which somehow means it is more naturally encoding the underlying symmetries of the system (because, I guess, one equation is simpler than three).
I'm grateful for your attempt at explaining! I've read it twice, and I'll read it again.
Your explanation relies on calculus; at school, I grokked differentiation, but I got a huge mental block on integration. My maths teacher was very good, he wrote famous maths textbooks, but he had no insight into my difficulties. He couldn't teach me, because he was too clever. That's why I never tackled graduate-level maths. I resent that old maths teacher; he meant well, but being super-clever wasn't his job. His job was to teach me.
It's not going to be useful to understand Lagrangians in detail unless you're actually doing the physics yourself -- especially because the whole framework is super problematic, pedagogically (I hope it gets 'refactored' someday into something more intuitive).
The important part is: a Lagrangian is a function that encodes the relationship between all of objects in a physical model, in such a way that you can 'add terms' to the function to add new interactions in your model. That much, at least, is quite elegant, and it's kinda miraculous that such a thing exists at all.
For what it's worth, integration is really not that tricky. If I had to guess what really deterred you was the obsession with annoying proofs about dividing functions into little rectangles and summing them up and taking their limit. That stuff is totally unnecessary, imo.
It's easier to think of integration as the inverse of differentiation. If differentiation tells you how fast a function is changing, then differentiating your position gives your velocity. Integration is the opposite: integrating your velocity over a length of time tells you how the position changes. That's a pretty intuitive idea: if I told you the velocity vector for the whole duration of a road trip, you can probably figure out where I ended up, if I also tell you where I started. That's all integration is.
What annoyed me about integral calculus was that it all seemed to be a bunch of heuristic rules. They showed me how to differentiate "from scratch", as it were, like from first principles; but integration seemed to be working backwards from the results of differentiation (which is roughly what you just said).
That is, it didn't look like maths to me. It didn't seem to have the rigour of, say, trig.
I expected maths to be deterministic, and I hated having heuristics in there. It was a gut reaction, it happened when I was about 17, and I'm sure that integration isn't heuristic in that way; I wonder if my mental block might not have ocurred if it had been presented to me differently.
> It's the physics equivalent of being an anti-vaxxer
I think that's really unfair.
"Anti-vaxxer" is a glib put-down. I'm actually double-vaccinated, but I think there are rational arguments for avoiding vaccination. I just don't happen to agree with them. The term "anti-vaxxer" is used to refer to anyone that you think doesn't listen to reason. It's used to dismiss ill-educated gun-toting wing-nuts.
I had a 20-minute conversation with my physician, before I took the vaccine. He took me seriously. He didn't tell me I was a wing-nut.
So maybe I have some nutty notions. But let's be honest: black holes, the Big Bang, and supernova explosions, are all pretty fruity ideas. Let's not get into String Theory. I'm not suggesting these ideas are wrong; just that they seem at first glance to be about as fruity as astrology. When I first heard of supernovas, nobody had ever observed one.
Thanks for the HC link. I seem to be in agreement with the unpopular people.
By the time this is all sorted out, I'll be dead. My girlfriend doesn't care about physics or cosmology, so it doesn't really matter if my opinions are unpopular with her. Maybe having unpopular views on science would explain why I have so few friends, though! :-)
[1] "Elementary Particles Result from Space-Time Quantization" by A.Meessen https://www.scirp.org/journal/paperinformation.aspx?paperid=...