3 ms·

If the results are correct, it means that extreme weak field gravity laws are actually in need of modification. I'd be very surprised if any existing variant of

If the results are correct, it means that extreme weak field gravity laws are actually in need of modification. I'd be very surprised if any existing variant of MOND got it right, but it would still mean that the premise of MOND is correct, which would be a huge deal.

V1ndaar 3y ago
> premise of MOND is correct Well, typically the term MOND refers to very specific modifications of Newtonian gravity and doesn't even take into account GR. So I'm not sure I would agree with the statement in general terms (note, I haven't read the paper so far, so I don't know what they claim). There's _plenty_ of extensions of GR though that modify gravity. That in itself isn't really that surprising. Scalar-Tensor theory and the like. And there's a reason these are usually not called MOND. Some go by "MOG" for modified gravity.
- sigmoid10 3y ago
  The paper actually mentions a specific form of MOND called AQUAL [1]. The original version of MOND was a very specific, simple modification of Newton's laws, but over the decades it has become more of a synonym for all attempts at modifying gravity at long distances. Especially since all of these attempts modify the weak field regime, which is equivalent to modifying Newton's law of gravity. [1] https://en.m.wikipedia.org/wiki/AQUAL https://en.m.wikipedia.org/wiki/AQUAL
- AnimalMuppet 3y ago
  This particular proposed modification is for very weak accelerations. That's where Newtonian gravity is least corrected by GR.
naasking 3y ago
> I'd be very surprised if any existing variant of MOND got it right I'm not sure why this would be surprising, MOND has made many more successful predictions than DM.
- sigmoid10 3y ago
  That is simply not true. Like, it's literally the opposite of the truth.
  - naasking 3y ago
    Don't confuse post-hoc curve fitting with predictions: From galactic bars to the Hubble tension: weighing up the astrophysical evidence for Milgromian gravity, https://arxiv.org/abs/2110.06936 https://arxiv.org/abs/2110.06936
    - sigmoid10 3y ago
      You should read up on how DM is fitted vs how MOND is fitted. But neither preceded the data in the way you imply and DM is vastly more successful at predicting all observations with a single fit.
      - naasking 3y ago
        What I know is that MOND predicted the high redshift galaxies we're now seeing 20 years ago, and DM did not: https://tritonstation.com/2022/01/03/what-jwst-will-see/ https://tritonstation.com/2022/01/03/what-jwst-will-see/ There are many instances like this as outlined in the paper I linked.

V1ndaar 3y ago

> premise of MOND is correct Well, typically the term MOND refers to very specific modifications of Newtonian gravity and doesn't even take into account GR. So I'm not sure I would agree with the statement in general terms (note, I haven't read the paper so far, so I don't know what they claim). There's _plenty_ of extensions of GR though that modify gravity. That in itself isn't really that surprising. Scalar-Tensor theory and the like. And there's a reason these are usually not called MOND. Some go by "MOG" for modified gravity.

sigmoid10 3y ago
The paper actually mentions a specific form of MOND called AQUAL [1]. The original version of MOND was a very specific, simple modification of Newton's laws, but over the decades it has become more of a synonym for all attempts at modifying gravity at long distances. Especially since all of these attempts modify the weak field regime, which is equivalent to modifying Newton's law of gravity. [1] https://en.m.wikipedia.org/wiki/AQUAL https://en.m.wikipedia.org/wiki/AQUAL
AnimalMuppet 3y ago
This particular proposed modification is for very weak accelerations. That's where Newtonian gravity is least corrected by GR.

naasking 3y ago

> I'd be very surprised if any existing variant of MOND got it right I'm not sure why this would be surprising, MOND has made many more successful predictions than DM.

sigmoid10 3y ago
That is simply not true. Like, it's literally the opposite of the truth.
- naasking 3y ago
  Don't confuse post-hoc curve fitting with predictions: From galactic bars to the Hubble tension: weighing up the astrophysical evidence for Milgromian gravity, https://arxiv.org/abs/2110.06936 https://arxiv.org/abs/2110.06936
  - sigmoid10 3y ago
    You should read up on how DM is fitted vs how MOND is fitted. But neither preceded the data in the way you imply and DM is vastly more successful at predicting all observations with a single fit.
    - naasking 3y ago
      What I know is that MOND predicted the high redshift galaxies we're now seeing 20 years ago, and DM did not: https://tritonstation.com/2022/01/03/what-jwst-will-see/ https://tritonstation.com/2022/01/03/what-jwst-will-see/ There are many instances like this as outlined in the paper I linked.