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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 sha

by ajkjk 5y ago

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.

chasil 5y ago
This article says several times: "...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?
- ajkjk 5y ago
  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.
  - chasil 5y ago
    Is a massless neutrino an axiom of the standard model, or is this somehow a simplifying assumption?
    - ajkjk 5y ago
      It's an assumption. You can skim the details here: https://en.wikipedia.org/wiki/Mathematical_formulation_of_the_Standard_Model#Neutrino_masses https://en.wikipedia.org/wiki/Mathematical_formulation_of_th... 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.
      - denton-scratch 5y ago
        I will have to find out what "Lagrangian" means. It seems to be important in SM.
        ajkjk 5y ago
denton-scratch 5y ago
> 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.

by ajkjk 5y ago

chasil 5y ago

This article says several times: "...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?

ajkjk 5y ago
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.
- chasil 5y ago
  Is a massless neutrino an axiom of the standard model, or is this somehow a simplifying assumption?
  - ajkjk 5y ago
    It's an assumption. You can skim the details here: https://en.wikipedia.org/wiki/Mathematical_formulation_of_the_Standard_Model#Neutrino_masses https://en.wikipedia.org/wiki/Mathematical_formulation_of_th... 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.
    - denton-scratch 5y ago
      I will have to find out what "Lagrangian" means. It seems to be important in SM.
      - ajkjk 5y ago

denton-scratch 5y ago

> 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.