4 ms·

I don't think it's fair to say that it's "tuned" to fit observation. It's not like several different types of DM are introduced to fit the observation. Rather t

I don't think it's fair to say that it's "tuned" to fit observation. It's not like several different types of DM are introduced to fit the observation. Rather the observations add some constraints to the DM properties. That's how it's supposed to be.

naasking 4y ago
If DM has to have a very specific initial distribution to reproduce what we see, for example, that too is a constraint but it's also fine-tuning. Another theory that is free of such parameters should be preferred. Some types of constraints really should decrease a theory's plausibility.
- sigmoid10 4y ago
  MOND needs some pretty crazy arguing to explain decoupling of gravity from baryonic matter distributions. And it also needs a varying length scale parameter to account for different galaxy types. Particle DM can explain all of these things at the same time without re-tuning the model every time.
  - naasking 4y ago
    > MOND needs some pretty crazy arguing to explain decoupling of gravity from baryonic matter distributions. And it also needs a varying length scale parameter to account for different galaxy types. You mean the theory that has received 2-3 orders of magnitude less attention than DM has some conceptual holes to patch up? Colour me shocked. The fact that DM still fails despite all of that investment should worry you more. > Particle DM can explain all of these things at the same time without re-tuning the model every time. DM has already been tweaked and fine-tuned to patch up its own endless list of holes, many of which were recently reviewed by McGaugh [1]. Many more remain despite that, like the dynamical friction discussed in this article. [1] https://tritonstation.com/2022/04/08/two-hypotheses/ https://tritonstation.com/2022/04/08/two-hypotheses/
    - sigmoid10 4y ago
      Here's an explanation why McGaugh's work is highly dubious: https://www.preposterousuniverse.com/blog/2011/02/26/dark-matter-just-fine-thanks/ https://www.preposterousuniverse.com/blog/2011/02/26/dark-ma... It also talks about the general problems with alternatives to particle DM.
      - naasking 4y ago
        Sean's breakdown is ironic, because every point he makes against MOND also applies to DM theories, particularly given new evidence. I have no problem acknowledging that MOND is inadequate given the data, but apparently it's difficult for DM supporters to similarly acknowledge that DM has been refuted. The core argument for DM rests on a theory (GR) that we already know must be incorrect due to its singularities. Finally, I'll just note that literally nothing in Sean's post suggests McGaugh's work is "dubious" in the least, so I have no idea where you got that notion.

naasking 4y ago

If DM has to have a very specific initial distribution to reproduce what we see, for example, that too is a constraint but it's also fine-tuning. Another theory that is free of such parameters should be preferred. Some types of constraints really should decrease a theory's plausibility.

sigmoid10 4y ago
MOND needs some pretty crazy arguing to explain decoupling of gravity from baryonic matter distributions. And it also needs a varying length scale parameter to account for different galaxy types. Particle DM can explain all of these things at the same time without re-tuning the model every time.
- naasking 4y ago
  > MOND needs some pretty crazy arguing to explain decoupling of gravity from baryonic matter distributions. And it also needs a varying length scale parameter to account for different galaxy types. You mean the theory that has received 2-3 orders of magnitude less attention than DM has some conceptual holes to patch up? Colour me shocked. The fact that DM still fails despite all of that investment should worry you more. > Particle DM can explain all of these things at the same time without re-tuning the model every time. DM has already been tweaked and fine-tuned to patch up its own endless list of holes, many of which were recently reviewed by McGaugh [1]. Many more remain despite that, like the dynamical friction discussed in this article. [1] https://tritonstation.com/2022/04/08/two-hypotheses/ https://tritonstation.com/2022/04/08/two-hypotheses/
  - sigmoid10 4y ago
    Here's an explanation why McGaugh's work is highly dubious: https://www.preposterousuniverse.com/blog/2011/02/26/dark-matter-just-fine-thanks/ https://www.preposterousuniverse.com/blog/2011/02/26/dark-ma... It also talks about the general problems with alternatives to particle DM.
    - naasking 4y ago
      Sean's breakdown is ironic, because every point he makes against MOND also applies to DM theories, particularly given new evidence. I have no problem acknowledging that MOND is inadequate given the data, but apparently it's difficult for DM supporters to similarly acknowledge that DM has been refuted. The core argument for DM rests on a theory (GR) that we already know must be incorrect due to its singularities. Finally, I'll just note that literally nothing in Sean's post suggests McGaugh's work is "dubious" in the least, so I have no idea where you got that notion.