accdd
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Is it possible that galaxies are spinning faster than expected due to a particular configuration of the moving mass and not due to dark matter?
Rotation of Galaxies: Mass vs Dark Matter?
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No.accdd said:
If that were possible then we wouldn't have an unsolved problem, we'd have observational data telling us how matter is distributed within galaxies.
(Unless some other unknown physics is at work, and in the absence of any plausible candidate theory that's just idle speculation).
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Well, you could put rocket engines on all the stars.Nugatory said:
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Arguably, Deur's idea that we've failed to properly account for the GR effects of rotating matter fits the question.
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I thought Deur's idea was about GR effects of non-spherical configurations of matter, not about GR effects of rotating matter. His basic idea, as I understand it, is that the GR effects of a flat disk are significantly different from those of a sphere, and the standard method of calculating galaxy rotation curves is basically assuming that they're not, and using the simpler calculations for a sphere.Ibix said:
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You're more likely to be right than I am. Either way, he's explaining galaxy rotation curves using the visible matter and vanilla GR so he doesn't need dark matter. (Or so he says, anyway.)PeterDonis said:
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Yes, that's correct. But since the topic of this thread is particularly the effects of rotation, I don't think Deur's proposal is relevant to this particular thread.Ibix said:
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The initial post is too vague to really discuss. "A particular configuration of moving mass" that we cannot see? How does that differ from Dark Matter?
I am not an expert, but the problem I have with Deur-like theories is that the effect we are ascribing to Dark Matter is comparable to (actually, larger than) the Newtonian components. GR effects are usually smaller - the one exception I am immediately aware of goes as β, which is tiny for galactic rotation curves.
I am not an expert, but the problem I have with Deur-like theories is that the effect we are ascribing to Dark Matter is comparable to (actually, larger than) the Newtonian components. GR effects are usually smaller - the one exception I am immediately aware of goes as β, which is tiny for galactic rotation curves.