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Why is Hacker News so fixated on MOND? I mean, I guess general relativity is hard for general public, but come on... At this point MONDs look like really overf

by Svoka 5y ago

Why is Hacker News so fixated on MOND? I mean, I guess general relativity is hard for general public, but come on... At this point MONDs look like really overfit models, failing to make any observable predictions, struggling to describe what we already observe (by overfitting)

actually_a_dog 5y ago
My thoughts exactly. In particular: > The idea did not spring from any underlying theory.... It all tends to remind me of epicycles. https://en.wikipedia.org/wiki/Deferent_and_epicycle https://en.wikipedia.org/wiki/Deferent_and_epicycle
autokad 5y ago
the biggest point is: you are telling me there is something that makes up the majority of matter in the universe (27% dark matter vs 5% matter) and we still haven't observed a single iota of it, even after spending more than 3 decades and billions of dollars? 'well it fits all of our understanding of the universe and what we observe in a few things' It comes on top of things that cosmologists have been wrong for very very very long times on. Look how long they thought it was silly to consider the big bang. maybe it would be easier to accept if they were like 'well the big bang is a very interesting idea but it just doesn't fit evidence' instead of 'that's a stupid idea, my idea (static universe) is simpler so its right'. speaking of which, we really need to get off this 'simple idea is the right idea' dogma. The universe owes us no such obligation to be simple. cosmology got so many assumptions baked in them its hard to figure out where they begin and end. for example, look how much relies off the idea that the universe is the same everywhere, which we now know as wrong, but cosmologists are only slightly admitting to that fact.
- Svoka 5y ago
  There's so much wrong with this comment. > you are telling me there is something that makes up the majority of matter in the universe (27% dark matter vs 5% matter) and we still haven't observed a single iota of it, even after spending more than 3 decades and billions of dollars? Of course we observed it. In how galaxies spin. We did not observe dark matter directly. So far existence of dark matter is not questioned because it is backed by multiple predictions and observations. Question is about its composition. > well it fits all of our understanding of the universe and what we observe in a few things Not sure what it means. > It comes on top of things that cosmologists have been wrong for very very very long times on. Look how long they thought it was silly to consider the big bang. maybe it would be easier to accept if they were like 'well the big bang is a very interesting idea but it just doesn't fit evidence' instead of 'that's a stupid idea, my idea (static universe) is simpler so its right'. This is gross oversimplification to the point where it loses all meaning. I can't even begin to answer because it. > speaking of which, we really need to get off this 'simple idea is the right idea' dogma. The universe owes us no such obligation to be simple. I guess General Relativity is complex enough that most still try to drag what they learned in high school to fit reality > look how much relies off the idea that the universe is the same everywhere, which we now know as wrong, but cosmologists are only slightly admitting to that fact. Did I missed a Nobel Prize for proving cosmological principle wrong? Because so far all I seen was an overwhelming evidence for its correctness.
- garmaine 5y ago
  > for example, look how much relies off the idea that the universe is the same everywhere, which we now know as wrong What is this in reference to?
  - cinquemb 5y ago
    perhaps the topology of spacetime and usual assumptions of some kind of constant (or no) curvature everywhere as apposed to something with more complex curvature?
  - User23 5y ago
    The cosmological principle[1]. It's not an experimental result, it's just an assumption. [1] http://curious.astro.cornell.edu/about-us/101-the-universe/cosmology-and-the-big-bang/general-questions/574-what-do-homogeneity-and-isotropy-mean-intermediate http://curious.astro.cornell.edu/about-us/101-the-universe/c...
    - garmaine 5y ago
      I thought it was the strong equivalence principle in general relatively, or the (nameless?) assumption that the same laws of physics hold true everywhere. Regardless, my question was about the part of the quote which said: "which we now know as wrong." What aspect of the cosmological principle, strong equivalence principle, or the universal application of physical law do we now know to be be wrong?
      - autokad 5y ago
        Its the idea if you take one slice of the universe, it should be the same as any other slice. in this case, not talking about different physics but different makeups. then they noticed that the spin of galaxies is correlated. like one pie in the sky of galaxies tend to spin left, and the next one tends to spin right, and the next one after that left again. as far as I know, its unsolved as to why. some think it might be that the observed galaxies are spinning around something much bigger that we have yet observed, others think its an influence by the cosmic web. the idea that the universe is the same as everywhere (although an assumption) is very much baked in lots of theories, including the arguments that support dark matter.
- deleted 5y ago
  [deleted]
- burnished 5y ago
  >'simple idea is the right idea' dogma. The universe owes us no such obligation to be simple. You aren't wrong, but the simple answer is a really good heuristic. Its just, when you're wrong, you're gonna be really wrong and it'll be almost definitionally interesting and noteworthy.
dnautics 5y ago
wait, what? Are you seriously saying MOND is an overfit and LCDM isn't? MOND is gravity + 1 free parameter, and this theory adds one more free parameter. Conventional dark matter generates a "distribution of dark matter" that is set on a per-galaxy basis, so each galaxy gets its own parameter space. The classic rebuttal against the MOND is that LCDM has the freedom to explain galaxies with "too much" and "too little" dark matter, which gets to exactly that point. Whatever you think of MOND, dismissing it as an overfit model, given how LCDM works, is really strange.
- SpaceManNabs 5y ago
  And then enters Relativistic MOND so we go go back to LCDM.
- Avshalom 5y ago
  I mean conventional matter generates a distribution of matter that is set on a per galaxy basis.
SpaceManNabs 5y ago
I cant believe this MOND stuff is still going on. Perusing a few of the other comments is so frustrating. Just please take a GR class.

by Svoka 5y ago

actually_a_dog 5y ago

My thoughts exactly. In particular: > The idea did not spring from any underlying theory.... It all tends to remind me of epicycles. https://en.wikipedia.org/wiki/Deferent_and_epicycle https://en.wikipedia.org/wiki/Deferent_and_epicycle

autokad 5y ago

the biggest point is: you are telling me there is something that makes up the majority of matter in the universe (27% dark matter vs 5% matter) and we still haven't observed a single iota of it, even after spending more than 3 decades and billions of dollars? 'well it fits all of our understanding of the universe and what we observe in a few things' It comes on top of things that cosmologists have been wrong for very very very long times on. Look how long they thought it was silly to consider the big bang. maybe it would be easier to accept if they were like 'well the big bang is a very interesting idea but it just doesn't fit evidence' instead of 'that's a stupid idea, my idea (static universe) is simpler so its right'. speaking of which, we really need to get off this 'simple idea is the right idea' dogma. The universe owes us no such obligation to be simple. cosmology got so many assumptions baked in them its hard to figure out where they begin and end. for example, look how much relies off the idea that the universe is the same everywhere, which we now know as wrong, but cosmologists are only slightly admitting to that fact.

Svoka 5y ago
There's so much wrong with this comment. > you are telling me there is something that makes up the majority of matter in the universe (27% dark matter vs 5% matter) and we still haven't observed a single iota of it, even after spending more than 3 decades and billions of dollars? Of course we observed it. In how galaxies spin. We did not observe dark matter directly. So far existence of dark matter is not questioned because it is backed by multiple predictions and observations. Question is about its composition. > well it fits all of our understanding of the universe and what we observe in a few things Not sure what it means. > It comes on top of things that cosmologists have been wrong for very very very long times on. Look how long they thought it was silly to consider the big bang. maybe it would be easier to accept if they were like 'well the big bang is a very interesting idea but it just doesn't fit evidence' instead of 'that's a stupid idea, my idea (static universe) is simpler so its right'. This is gross oversimplification to the point where it loses all meaning. I can't even begin to answer because it. > speaking of which, we really need to get off this 'simple idea is the right idea' dogma. The universe owes us no such obligation to be simple. I guess General Relativity is complex enough that most still try to drag what they learned in high school to fit reality > look how much relies off the idea that the universe is the same everywhere, which we now know as wrong, but cosmologists are only slightly admitting to that fact. Did I missed a Nobel Prize for proving cosmological principle wrong? Because so far all I seen was an overwhelming evidence for its correctness.
garmaine 5y ago
> for example, look how much relies off the idea that the universe is the same everywhere, which we now know as wrong What is this in reference to?
- cinquemb 5y ago
  perhaps the topology of spacetime and usual assumptions of some kind of constant (or no) curvature everywhere as apposed to something with more complex curvature?
- User23 5y ago
  The cosmological principle[1]. It's not an experimental result, it's just an assumption. [1] http://curious.astro.cornell.edu/about-us/101-the-universe/cosmology-and-the-big-bang/general-questions/574-what-do-homogeneity-and-isotropy-mean-intermediate http://curious.astro.cornell.edu/about-us/101-the-universe/c...
  - garmaine 5y ago
    I thought it was the strong equivalence principle in general relatively, or the (nameless?) assumption that the same laws of physics hold true everywhere. Regardless, my question was about the part of the quote which said: "which we now know as wrong." What aspect of the cosmological principle, strong equivalence principle, or the universal application of physical law do we now know to be be wrong?
    - autokad 5y ago
      Its the idea if you take one slice of the universe, it should be the same as any other slice. in this case, not talking about different physics but different makeups. then they noticed that the spin of galaxies is correlated. like one pie in the sky of galaxies tend to spin left, and the next one tends to spin right, and the next one after that left again. as far as I know, its unsolved as to why. some think it might be that the observed galaxies are spinning around something much bigger that we have yet observed, others think its an influence by the cosmic web. the idea that the universe is the same as everywhere (although an assumption) is very much baked in lots of theories, including the arguments that support dark matter.
deleted 5y ago
[deleted]
burnished 5y ago
>'simple idea is the right idea' dogma. The universe owes us no such obligation to be simple. You aren't wrong, but the simple answer is a really good heuristic. Its just, when you're wrong, you're gonna be really wrong and it'll be almost definitionally interesting and noteworthy.

dnautics 5y ago

wait, what? Are you seriously saying MOND is an overfit and LCDM isn't? MOND is gravity + 1 free parameter, and this theory adds one more free parameter. Conventional dark matter generates a "distribution of dark matter" that is set on a per-galaxy basis, so each galaxy gets its own parameter space. The classic rebuttal against the MOND is that LCDM has the freedom to explain galaxies with "too much" and "too little" dark matter, which gets to exactly that point. Whatever you think of MOND, dismissing it as an overfit model, given how LCDM works, is really strange.

SpaceManNabs 5y ago
And then enters Relativistic MOND so we go go back to LCDM.
Avshalom 5y ago
I mean conventional matter generates a distribution of matter that is set on a per galaxy basis.

SpaceManNabs 5y ago

I cant believe this MOND stuff is still going on. Perusing a few of the other comments is so frustrating. Just please take a GR class.