Talk:Modified Newtonian dynamics

I removed the following part:

Spiral galaxies offer compelling evidence that this is more than an observational artifact. M51, for example, has two main arms (see fig. 1), each of which has an exterior end approximately 180° behind the interior end connected to the bulge. It thus appears that the edge completes an orbit in almost the same time as the interior. However, if Newton's universal law of gravitation holds for galaxies (as it should), stars at the edge should move much slower, and the spiral arms should be stretched around the bulge a hundred times, which would make the two arms completely indistinguishable.

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The existence of spiral galaxies alone does not provide compelling evidence for the flattening of the rotation curve, since the galaxy's arms do not consist of stars; they are pressure waves rotating around the galaxy's center independently of the matter comprising the galaxy. AxelBoldt 11:20 Aug 15, 2002 (PDT)

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For comparison purpose, the same curve for the Solar system -- (properly scaled) -- is provided (curve C in fig. 2).

Am I missing something? I see the letter C but no associated curve. --Nate 21:14 Nov 27, 2002 (UTC)

I can't see curve C in Fig. 2 either. [Feb 5, 2004 Wes Hughes]

Galaxy rotation problem

Does it make sense to essentially copy all of Galaxy rotation problem into this article?

Aragorn2 15:07, 25 Sep 2003 (UTC)

I just ran into this article, the first paragraph is indeed copied (but it is allowed under Wiki GNU Free Documentation License. Anyway, the majority of the article is dedicated to the solution of the problem by Milgrom's MOND. A descripition of the problem is neccesary. MathKnight 22:21, 28 Aug 2004 (UTC)

Rotation curves are not evidence

"Since MOND was specifically designed to produce flat rotation curves, these do not constitute evidence for the theory."

I don't agree with this formulation. Any theory aims to match its predictions with already known observations. By the same principle the standard model of particle physics would be useless, because it "depends on 19 parameters, whose numerical values are established by experiment".

Only data that has been used to produce $a_{0}$ should be dismissed as evidence.

References

New study suggests local evidence for MOND

Turns out we don't need to go far to potentially find evidence supporting MOND at low accelerations. The evidence just may be coming to a solar system near you ;)

https://phys.org/news/2023-10-plot-thickens-ninth-planet.html

Nope, me neither. Didn't see that one coming.

Cadar (talk) 14:41, 10 October 2023 (UTC)