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The third explanation for the problem is that we use wrong approximations of equations of the General Relativity. Even Wikipedia entry on the rotational curves

The third explanation for the problem is that we use wrong approximations of equations of the General Relativity. Even Wikipedia entry on the rotational curves site a paper that shows that properly accounting for General Relativity is enough to explain the rotational curves of our Galaxy. Then there is very interesting take on the equations in [1] that also explains the rotational curves and few more observed effects again without any extra particles or fields. [1] https://link.springer.com/article/10.1140/epjc/s10052-021-08967-3 https://link.springer.com/article/10.1140/epjc/s10052-021-08...

forgotpwd16 5y ago
The galactic rotation curves isn't the only reason for requiring dark matter. And gravitomagnetism is a known effect. I don't think for decades being studied everyone was doing it wrong.
- fpoling 5y ago
  The problem of rotational curves and few other effects attributed to the dark matter appears if one applies Newtonian mechanics on a galaxy or intergalactic scales. Yet to this day there is no proof that this is a sound approximation even for small galaxies. It is just assumed that is a valid approximation without justification. And the reason for that is that accounting for General Relativity is hard even if one consider just next order approximation after Newtonian gravity. So yes, it could be that almost everybody was doing it wrong.
nicklecompte 5y ago
Has there been any updates from the astrophysics community about this “gravitational magnetism” explanation[1]? GR/cosmology is not my area of expertise, but if astrophysicists were indeed neglecting the impact of rotating masses on gravitation that seems like a major oversight that needs to be investigated. [1] A static charge generates an electric field and a moving charge generates a magnetic field. There is a similar effect for gravity: the Einstein equations have a sort of symmetry to the Maxwell equations.
- fpoling 5y ago
  The article cited from Wikipedia, https://arxiv.org/abs/1810.04445 https://arxiv.org/abs/1810.04445 , also pointed out that accounting for terms in the metric tensor related to rotation was essential to explain the rotational curves and not using them is simply unsound approximation.
- Sniffnoy 5y ago
  Yes -- the paper is just wrong, lots of other people have also done this calculation and shown that it's off by multiple orders of magnitude. Robin Hanson claims the particular error is the paper's assumption of zero pressure: https://www.overcomingbias.com/2021/03/what-holds-up-a-north-pole-of-dust.html https://www.overcomingbias.com/2021/03/what-holds-up-a-north... Note that what the paper refers to as "gravitomagnetism" is more commonly referred to as "frame-dragging": https://en.wikipedia.org/wiki/Frame-dragging https://en.wikipedia.org/wiki/Frame-dragging
Sniffnoy 5y ago
This paper is just wrong, lots of other people have also done this calculation and shown that it's off by multiple orders of magnitude. Robin Hanson claims the particular error is the paper's assumption of zero pressure: https://www.overcomingbias.com/2021/03/what-holds-up-a-north-pole-of-dust.html https://www.overcomingbias.com/2021/03/what-holds-up-a-north...

forgotpwd16 5y ago

The galactic rotation curves isn't the only reason for requiring dark matter. And gravitomagnetism is a known effect. I don't think for decades being studied everyone was doing it wrong.

fpoling 5y ago
The problem of rotational curves and few other effects attributed to the dark matter appears if one applies Newtonian mechanics on a galaxy or intergalactic scales. Yet to this day there is no proof that this is a sound approximation even for small galaxies. It is just assumed that is a valid approximation without justification. And the reason for that is that accounting for General Relativity is hard even if one consider just next order approximation after Newtonian gravity. So yes, it could be that almost everybody was doing it wrong.

nicklecompte 5y ago

Has there been any updates from the astrophysics community about this “gravitational magnetism” explanation[1]? GR/cosmology is not my area of expertise, but if astrophysicists were indeed neglecting the impact of rotating masses on gravitation that seems like a major oversight that needs to be investigated. [1] A static charge generates an electric field and a moving charge generates a magnetic field. There is a similar effect for gravity: the Einstein equations have a sort of symmetry to the Maxwell equations.

fpoling 5y ago
The article cited from Wikipedia, https://arxiv.org/abs/1810.04445 https://arxiv.org/abs/1810.04445 , also pointed out that accounting for terms in the metric tensor related to rotation was essential to explain the rotational curves and not using them is simply unsound approximation.
Sniffnoy 5y ago
Yes -- the paper is just wrong, lots of other people have also done this calculation and shown that it's off by multiple orders of magnitude. Robin Hanson claims the particular error is the paper's assumption of zero pressure: https://www.overcomingbias.com/2021/03/what-holds-up-a-north-pole-of-dust.html https://www.overcomingbias.com/2021/03/what-holds-up-a-north... Note that what the paper refers to as "gravitomagnetism" is more commonly referred to as "frame-dragging": https://en.wikipedia.org/wiki/Frame-dragging https://en.wikipedia.org/wiki/Frame-dragging

Sniffnoy 5y ago

This paper is just wrong, lots of other people have also done this calculation and shown that it's off by multiple orders of magnitude. Robin Hanson claims the particular error is the paper's assumption of zero pressure: https://www.overcomingbias.com/2021/03/what-holds-up-a-north-pole-of-dust.html https://www.overcomingbias.com/2021/03/what-holds-up-a-north...