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Why does MOND keep showing up on HN? Pretty odd considering it's not particularly popular elsewhere and fails to explain a lot of observations of dark matter (b

by xanzi2048 2y ago

Why does MOND keep showing up on HN? Pretty odd considering it's not particularly popular elsewhere and fails to explain a lot of observations of dark matter (bullet cluster, CMB). It's worth noting these rotation curves are not all the same curve, and we've discovered galaxies with varying quantities of implied dark matter (eg https://www.aanda.org/articles/aa/full_html/2023/07/aa46291-23/aa46291-23.html https://www.aanda.org/articles/aa/full_html/2023/07/aa46291-...) - so is MOND different for every galaxy?

deleted 2y ago
[deleted]
MattPalmer1086 2y ago
No. MOND is the same everywhere, with basically no free parameters.
- xanzi2048 2y ago
  but... how is that compatible with the article I linked here? Some galaxies look like they have very little dark matter, a MOND with no free parameters can't explain why different galaxies have different inconsistencies in their rotation curves.
  - throwawaymaths 2y ago
    You actually have to do the math, it's not just a "no dark matter hurr durr" thing. MOND predicts "no dark matter" if the acceleration regime is high. Most galaxies that havd "very little dark matter" are in the high acceleration regime. Most of the others seem to be susceptible to observational error (e.g. ultra diffuses). Galaxy rotation curves measurements are highly sensitive to orientation of the rotational axis and distance to us (you're gonna have a hard time measuring it if the galaxy is face on)
  - MattPalmer1086 2y ago
    Correct. MOND cannot explain why some galaxies don't fit it's predicted rotation curve. However, the vast majority do, and the linked paper says that the ones they are describing are extremely rare.
ttpphd 2y ago
Because HN loves Sabine H.
- stoperaticless 2y ago
  I do. Just please don’t mention that to my wife. Worth noting that recently (when couple of months is considered recent), she mentioned that she had falling out with MOND (due to some new study coming to ger attention).
- mrguyorama 2y ago
  And they specifically love her because she is extremely contrarian. HN has a massive problem with contrarian bias.
deleted 2y ago
[deleted]
ansible 2y ago
I also don't know why MOND remains so popular. Angela Collier talks about Dark Matter here: https://www.youtube.com/watch?v=PbmJkMhmrVI https://www.youtube.com/watch?v=PbmJkMhmrVI And talks more about how often MOND is brought up in comments on her own video: https://www.youtube.com/watch?v=qS34oV-jv_A https://www.youtube.com/watch?v=qS34oV-jv_A
- roywiggins 2y ago
  It's easy to be a MOND enthusiast without a physics PhD, it's a lot harder to be an axion or WIMP enthusiast. "Just tweak the laws of physics, bozos!" is a really easy idea for laymen to latch on to, which is why you see so much interest in it among science enthusiasts.
  - deleted 2y ago
    [deleted]
  - mrguyorama 2y ago
    "The experts are wrong because they are overcomplicating things" is also just a rhetorical trick that has pretty much always worked on some segment of the population.
- naasking 2y ago
  MOND remains popular because it's made so many successful a priori predictions that DM failed to do. At the risk of being too reductive: DM is popular among maths-oriented astrophysicists because as physicists they like particles and deep theories, and MOND by contrast, doesn't have a full theory justifying the adjustments to gravity and they don't like that; MOND tends to be more popular among astronomers than astrophysicists because they like effective theories that make successful predictions using few parameters, and MOND is somehow better at that (as with this paper).
- Sevii 2y ago
  It's because people don't like the idea of matter that you can't interact with especially if it makes up a double digit percentage of all mass in the universe.
notfed 2y ago
Maybe we need both?
naasking 2y ago
> Why does MOND keep showing up on HN? Pretty odd considering it's not particularly popular elsewhere and fails to explain a lot of observations of dark matter (bullet cluster, CMB). And DM fails to explain flat rotation curves out to 1000 parsecs, or how MOND was able to make so many successful a priori predictions where DM has to be curve fitted after the fact. This paper is just the latest to refute LCDM, but no doubt proponents will add yet more parameters to correct for this failure, as they have done many times in the past when observations refuted DM predictions. Honestly, you and many others have fallen for the DM propaganda. Both DM and MOND are problematic and fail in various ways. DM is not nearly as successful a scientific theory as most think, and MOND is not nearly as problematic: From Galactic Bars to the Hubble Tension: Weighing Up the Astrophysical Evidence for Milgromian Gravity, https://www.mdpi.com/2073-8994/14/7/1331 https://www.mdpi.com/2073-8994/14/7/1331
- canjobear 2y ago
  What would cause the large majority of a scientific field to fall for propaganda? If MOND is predictively superior then why is it not accepted?
  - deleted 2y ago
    [deleted]
  - naasking 2y ago
    The simple answer is 1) because physicists don't want to muck with general relativity which has had many successes across sub-galactic scales, so they are trying as hard as possible to jam a particle into the hole that's been observed when extending GR/Newton to galactic scales, 2) MOND is just an "effective theory" that seems to fit observations but doesn't really have a fully fleshed out theory explaining why this change to gravity happens; this "inelegance" rubs math-oriented physicsts the wrong way. I've mentioned elsewhere here that astrophysicsts tend to prefer DM because they like particles and mathematical elegance, and astronomers are more open to MOND because they like theories with few parameters that make successful predictions (a reductive generalization, but broadly true I think). JWST has validated many MOND predictions, so I hope people open their minds a little more now, but as I said, neither theory is fully satisfactory in the end. Edit: the author of this post is an astronomer that has been working in this field for a long time and he posted another article that reviews MOND and LCDM with some history: https://tritonstation.com/2023/01/05/question-of-the-year-and-a-challenge/ https://tritonstation.com/2023/01/05/question-of-the-year-an...
nonameiguess 2y ago
Hacker News is just a part of the larger web. It's the same reason you see so many people arguing over lab leak, ketogenic diets, barefoot running. Anything whatsoever that is vaguely heterodox and hints that you might have some knowledge that either the "establishment" doesn't know or is lying about is a tremendous ego boost. If your default position epistemically is you don't really have the expertise or time to investigate everything out there, which is more or less true for everyone no matter how intelligent you are or how much expertise you have on one specific topic, then if you're going to throw darts anyway, you may as well throw them at the target that, if correct, makes you look and feel just a little bit more special than the unwashed masses being spoonfed that food pyramid. I can't remember where at this point, but decades ago I heard this kind of thing called "insight porn" and have myself been guilty of it for much of my life. It's endemic to web communities composed of relatively smart people, at least if we take "smart" to mean something like intellectually curious and having right tail levels of raw cognitive ability, rather than meaning anything you believe is more likely to be true.
- roywiggins 2y ago
  MOND is also just a lot easier to feel like you understand than the zoo of proposed dark matter particles, so it sticks in the layman mind.
  - TheBlight 2y ago
    Which best satisfies Occam's Razor? 1) The vast majority of matter in the Universe is invisible. We've tried looking for it in a variety of ways for decades but we can't find it but we're sure it's there. 2) Our model of the Universe is slightly incorrect. It works in many many cases but not in interesting outlier situations. eg. at very low accelerations.
    - roywiggins 2y ago
      MOND doesn't explain all of the missing mass, it just reduces it to a fifth of what it was. So you need MOND and something else, which is two things, which Occam's Razor disfavors anyway.
cratermoon 2y ago
Marketing. https://www.youtube.com/watch?v=qS34oV-jv_A https://www.youtube.com/watch?v=qS34oV-jv_A

deleted 2y ago

[deleted]

MattPalmer1086 2y ago

No. MOND is the same everywhere, with basically no free parameters.

xanzi2048 2y ago
but... how is that compatible with the article I linked here? Some galaxies look like they have very little dark matter, a MOND with no free parameters can't explain why different galaxies have different inconsistencies in their rotation curves.
- throwawaymaths 2y ago
  You actually have to do the math, it's not just a "no dark matter hurr durr" thing. MOND predicts "no dark matter" if the acceleration regime is high. Most galaxies that havd "very little dark matter" are in the high acceleration regime. Most of the others seem to be susceptible to observational error (e.g. ultra diffuses). Galaxy rotation curves measurements are highly sensitive to orientation of the rotational axis and distance to us (you're gonna have a hard time measuring it if the galaxy is face on)
- MattPalmer1086 2y ago
  Correct. MOND cannot explain why some galaxies don't fit it's predicted rotation curve. However, the vast majority do, and the linked paper says that the ones they are describing are extremely rare.

ttpphd 2y ago

Because HN loves Sabine H.

stoperaticless 2y ago
I do. Just please don’t mention that to my wife. Worth noting that recently (when couple of months is considered recent), she mentioned that she had falling out with MOND (due to some new study coming to ger attention).
mrguyorama 2y ago
And they specifically love her because she is extremely contrarian. HN has a massive problem with contrarian bias.

deleted 2y ago

[deleted]

ansible 2y ago

I also don't know why MOND remains so popular. Angela Collier talks about Dark Matter here: https://www.youtube.com/watch?v=PbmJkMhmrVI https://www.youtube.com/watch?v=PbmJkMhmrVI And talks more about how often MOND is brought up in comments on her own video: https://www.youtube.com/watch?v=qS34oV-jv_A https://www.youtube.com/watch?v=qS34oV-jv_A

roywiggins 2y ago
It's easy to be a MOND enthusiast without a physics PhD, it's a lot harder to be an axion or WIMP enthusiast. "Just tweak the laws of physics, bozos!" is a really easy idea for laymen to latch on to, which is why you see so much interest in it among science enthusiasts.
- deleted 2y ago
  [deleted]
- mrguyorama 2y ago
  "The experts are wrong because they are overcomplicating things" is also just a rhetorical trick that has pretty much always worked on some segment of the population.
naasking 2y ago
MOND remains popular because it's made so many successful a priori predictions that DM failed to do. At the risk of being too reductive: DM is popular among maths-oriented astrophysicists because as physicists they like particles and deep theories, and MOND by contrast, doesn't have a full theory justifying the adjustments to gravity and they don't like that; MOND tends to be more popular among astronomers than astrophysicists because they like effective theories that make successful predictions using few parameters, and MOND is somehow better at that (as with this paper).
Sevii 2y ago
It's because people don't like the idea of matter that you can't interact with especially if it makes up a double digit percentage of all mass in the universe.

notfed 2y ago

Maybe we need both?

naasking 2y ago

> Why does MOND keep showing up on HN? Pretty odd considering it's not particularly popular elsewhere and fails to explain a lot of observations of dark matter (bullet cluster, CMB). And DM fails to explain flat rotation curves out to 1000 parsecs, or how MOND was able to make so many successful a priori predictions where DM has to be curve fitted after the fact. This paper is just the latest to refute LCDM, but no doubt proponents will add yet more parameters to correct for this failure, as they have done many times in the past when observations refuted DM predictions. Honestly, you and many others have fallen for the DM propaganda. Both DM and MOND are problematic and fail in various ways. DM is not nearly as successful a scientific theory as most think, and MOND is not nearly as problematic: From Galactic Bars to the Hubble Tension: Weighing Up the Astrophysical Evidence for Milgromian Gravity, https://www.mdpi.com/2073-8994/14/7/1331 https://www.mdpi.com/2073-8994/14/7/1331

canjobear 2y ago
What would cause the large majority of a scientific field to fall for propaganda? If MOND is predictively superior then why is it not accepted?
- deleted 2y ago
  [deleted]
- naasking 2y ago
  The simple answer is 1) because physicists don't want to muck with general relativity which has had many successes across sub-galactic scales, so they are trying as hard as possible to jam a particle into the hole that's been observed when extending GR/Newton to galactic scales, 2) MOND is just an "effective theory" that seems to fit observations but doesn't really have a fully fleshed out theory explaining why this change to gravity happens; this "inelegance" rubs math-oriented physicsts the wrong way. I've mentioned elsewhere here that astrophysicsts tend to prefer DM because they like particles and mathematical elegance, and astronomers are more open to MOND because they like theories with few parameters that make successful predictions (a reductive generalization, but broadly true I think). JWST has validated many MOND predictions, so I hope people open their minds a little more now, but as I said, neither theory is fully satisfactory in the end. Edit: the author of this post is an astronomer that has been working in this field for a long time and he posted another article that reviews MOND and LCDM with some history: https://tritonstation.com/2023/01/05/question-of-the-year-and-a-challenge/ https://tritonstation.com/2023/01/05/question-of-the-year-an...

nonameiguess 2y ago

Hacker News is just a part of the larger web. It's the same reason you see so many people arguing over lab leak, ketogenic diets, barefoot running. Anything whatsoever that is vaguely heterodox and hints that you might have some knowledge that either the "establishment" doesn't know or is lying about is a tremendous ego boost. If your default position epistemically is you don't really have the expertise or time to investigate everything out there, which is more or less true for everyone no matter how intelligent you are or how much expertise you have on one specific topic, then if you're going to throw darts anyway, you may as well throw them at the target that, if correct, makes you look and feel just a little bit more special than the unwashed masses being spoonfed that food pyramid. I can't remember where at this point, but decades ago I heard this kind of thing called "insight porn" and have myself been guilty of it for much of my life. It's endemic to web communities composed of relatively smart people, at least if we take "smart" to mean something like intellectually curious and having right tail levels of raw cognitive ability, rather than meaning anything you believe is more likely to be true.

roywiggins 2y ago
MOND is also just a lot easier to feel like you understand than the zoo of proposed dark matter particles, so it sticks in the layman mind.
- TheBlight 2y ago
  Which best satisfies Occam's Razor? 1) The vast majority of matter in the Universe is invisible. We've tried looking for it in a variety of ways for decades but we can't find it but we're sure it's there. 2) Our model of the Universe is slightly incorrect. It works in many many cases but not in interesting outlier situations. eg. at very low accelerations.
  - roywiggins 2y ago
    MOND doesn't explain all of the missing mass, it just reduces it to a fifth of what it was. So you need MOND and something else, which is two things, which Occam's Razor disfavors anyway.

cratermoon 2y ago

Marketing. https://www.youtube.com/watch?v=qS34oV-jv_A https://www.youtube.com/watch?v=qS34oV-jv_A