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Armchairing here, but what exactly about Einstein's theory doesn't correspond with this so called "current cosmological model"? This article doesn't really stat

Armchairing here, but what exactly about Einstein's theory doesn't correspond with this so called "current cosmological model"? This article doesn't really state what, exactly, needs to be "revised". Because, as someone said farther up in the comments, as far as I know, Einstein's theory has been confirmed against every experiement ever done.

colechristensen 4y ago
On galactic and larger scales galaxies move and form as though there is a lot more mass out there than we can see. I forget the exact figure but something like 20x as much. Either you have to patch your gravity theory or assume there’s a bunch of stuff which interacts gravitationally but barely or not at all with electromagnetism.
- lumost 4y ago
  Has this observation been tested against frame dragging? What if supermassive black holes rotate much faster than we except?
  - colechristensen 4y ago
    I'm sure that every iteration of "have you tried X" has been tried, which is why the most popular theory is "there's a bunch of stuff we can only see through its gravitational effect".
  - raattgift 4y ago
    Central black holes' spins don't drive their host galaxies' rotation. * Elliptical galaxies exist where the rotation curve almost exclusively measures radial motion of blobs of gas (radiating specific wavelengths, whose redshift we can compare with other parts of the same galaxy), and sometimes other bright objects with characteristic spectra, which move outwards and inwards on an elliptical orbit; these galaxies may not spin around an axis, and may not even have anything like an equator. The anomaly is that the difference in these rising-and-falling orbits' is not as large as expected -- the outer reaches are dimmer, less dusty, and less gassy than the denser inner reaches, so there is less ordinary mass out there, but this reduction in mass density is not reflected in the orbital speeds; * In discoid galaxies (spirals, etc.), the spin-axis of the central black hole may point at any angle relative to an axis through the galaxy centre, perpendicular to the thin disc; the polar jets of black holes can even blast mostly into the thin disc, rather than mostly out of it; the polar jets are indicative of the spin-axis of the central black hole; * Galaxies may have more than one central black hole, especially the larger ellipticals. These central black holes typically do not have their spin axes point in the same direction, and where the spin axes are remotely close to perpendicular the black holes might not all spin in the same direction; * Some central black holes are gargantuan, some are petite (ours is small, especially compared to the number of stars in the Milky Way), and some are apparently absent, but the rotation-curve anomalies appear to be very similar nevertheless. That said, active central black holes -- "Active Galactic Nuclei" (AGN), of which quasars are a species -- can blow tremendous amounts of matter out of the central regions of their host galaxies, and that can alter the orbital speeds of gas and dust clouds in those galaxies generally, and much more so the behaviours of X-ray-bright gas and dust they shoot outwards into extragalactic space. AGNs can switch from very bright to essentially off, and as far as we can tell the switch-off of AGNs does not cause the rotation curve anomalies to relax. (Our extremely quiet central black hole may have been an AGN perhaps as recently as millions of years ago. <https://en.wikipedia.org/wiki/Galactic_Center#Gamma-_and_X-ray_emitting_Fermi_bubbles https://en.wikipedia.org/wiki/Galactic_Center#Gamma-_and_X-r...>). Frame dragging by the rotation of central black holes in AGNs may be seen in the corkscrewing of their jet emissions: Galaxy 3C 348 shows this clearly <https://duckduckgo.com/?q=3C+348+galaxy&iax=images&ia=images&iai=https%3A%2F%2Fwww.physicsforums.com%2Fattachments%2Fherc-a-jpg.243430%2F https://duckduckgo.com/?q=3C+348+galaxy&iax=images&ia=images...> as does the more popular M87 <https://apod.nasa.gov/apod/ap011101.html https://apod.nasa.gov/apod/ap011101.html> These jets are very bright in some characteristic wavelengths (radio in 3C 348, X-Rays in M87), but they're much sparser than the starry regions of their respective galaxies. These two galaxies are large ellipticals, and their jets do not align with anything like a central rotational axis as in a spiral galaxy. The screw displacement related to frame dragging happens in the near region to the source black holes. Anomalous gas-cloud rotation curves are found in the far region, at the outer edges of galaxies.
jovial_cavalier 4y ago
Also armchair, but this is how I understand it: if you take gravitation as it is typically understood, it implies motion of stars around galaxies which we don't see. The discrepancy can be accounted for if you assume there is 33% more mass than we can traditionally observe, roughly suffusing each galaxy. Since we can't observe it, it's believed to not interact with any normal matter other than through the gravitational field. edit: 33% is definitely wrong, but I don't know the actual number...
potamic 4y ago
Confirmed against every experiment, but not observation. We do not know why galaxies rotate at the speed they do. Apparently we have a pretty good idea of their visible mass, but should result in much slower galaxies than what we observe.
- xigency 4y ago
  And then how do we know we have an accurate estimation of a stellar object’s mass if the observations don’t match our predictions? This is a big question for me.
  - TremendousJudge 4y ago
    Isn't that question why they felt the need to add "dark matter" to the equation? "Our mass estimation must be wrong, therefore there's all this mass we're not seeing"
    - saberdancer 4y ago
      They had to add more matter in some places and less in others. Estimation would have wrong numbers all around.
  - potamic 4y ago
    Ok, I wasn't being very accurate. More correctly, we do not know why outer stars in the galaxy rotate at the same speed as inner stars. As per gravitation laws, the farther the star is, the slower it should rotate. But they all rotate at the same speed, which only adds up if you assume there is some "dark matter" around the outside of the galaxy. I honestly do not know how they estimate stellar masses. I suspect they just look at density of stars and have perhaps established that stars are more or less distributed randomly, but I'm armchairing here. Maybe an expert can chime in.
    - trhway 4y ago
      >As per gravitation laws, the farther the star is, the slower it should rotate. That depends. The 1/R orbital speed relationship is valid only in cases of spherically symmetric mass distribution or when the radiuses of the interacting masses being much smaller than the distance between them. Neither of these is true for a star inside a galaxy disk. Correctly accounting for the disk shape gives you expected orbital speed much closer to the "outer stars in the galaxy rotate at the same speed as inner stars", though not exactly equal. The remaining difference is explained by the seond factor. That second factor is that "rotate" i suppose means orbiting around galaxy center. The stars in the disk aren't really orbiting, ie. they are actually flying away like in a fireworks wheel as the galaxy disk becomes larger and thinner - exactly because the stars' speed is still somewhat higher than the orbital speed as calculated above. Thus no need for DM here.

colechristensen 4y ago

On galactic and larger scales galaxies move and form as though there is a lot more mass out there than we can see. I forget the exact figure but something like 20x as much. Either you have to patch your gravity theory or assume there’s a bunch of stuff which interacts gravitationally but barely or not at all with electromagnetism.

lumost 4y ago
Has this observation been tested against frame dragging? What if supermassive black holes rotate much faster than we except?
- colechristensen 4y ago
  I'm sure that every iteration of "have you tried X" has been tried, which is why the most popular theory is "there's a bunch of stuff we can only see through its gravitational effect".
- raattgift 4y ago
  Central black holes' spins don't drive their host galaxies' rotation. * Elliptical galaxies exist where the rotation curve almost exclusively measures radial motion of blobs of gas (radiating specific wavelengths, whose redshift we can compare with other parts of the same galaxy), and sometimes other bright objects with characteristic spectra, which move outwards and inwards on an elliptical orbit; these galaxies may not spin around an axis, and may not even have anything like an equator. The anomaly is that the difference in these rising-and-falling orbits' is not as large as expected -- the outer reaches are dimmer, less dusty, and less gassy than the denser inner reaches, so there is less ordinary mass out there, but this reduction in mass density is not reflected in the orbital speeds; * In discoid galaxies (spirals, etc.), the spin-axis of the central black hole may point at any angle relative to an axis through the galaxy centre, perpendicular to the thin disc; the polar jets of black holes can even blast mostly into the thin disc, rather than mostly out of it; the polar jets are indicative of the spin-axis of the central black hole; * Galaxies may have more than one central black hole, especially the larger ellipticals. These central black holes typically do not have their spin axes point in the same direction, and where the spin axes are remotely close to perpendicular the black holes might not all spin in the same direction; * Some central black holes are gargantuan, some are petite (ours is small, especially compared to the number of stars in the Milky Way), and some are apparently absent, but the rotation-curve anomalies appear to be very similar nevertheless. That said, active central black holes -- "Active Galactic Nuclei" (AGN), of which quasars are a species -- can blow tremendous amounts of matter out of the central regions of their host galaxies, and that can alter the orbital speeds of gas and dust clouds in those galaxies generally, and much more so the behaviours of X-ray-bright gas and dust they shoot outwards into extragalactic space. AGNs can switch from very bright to essentially off, and as far as we can tell the switch-off of AGNs does not cause the rotation curve anomalies to relax. (Our extremely quiet central black hole may have been an AGN perhaps as recently as millions of years ago. <https://en.wikipedia.org/wiki/Galactic_Center#Gamma-_and_X-ray_emitting_Fermi_bubbles https://en.wikipedia.org/wiki/Galactic_Center#Gamma-_and_X-r...>). Frame dragging by the rotation of central black holes in AGNs may be seen in the corkscrewing of their jet emissions: Galaxy 3C 348 shows this clearly <https://duckduckgo.com/?q=3C+348+galaxy&iax=images&ia=images&iai=https%3A%2F%2Fwww.physicsforums.com%2Fattachments%2Fherc-a-jpg.243430%2F https://duckduckgo.com/?q=3C+348+galaxy&iax=images&ia=images...> as does the more popular M87 <https://apod.nasa.gov/apod/ap011101.html https://apod.nasa.gov/apod/ap011101.html> These jets are very bright in some characteristic wavelengths (radio in 3C 348, X-Rays in M87), but they're much sparser than the starry regions of their respective galaxies. These two galaxies are large ellipticals, and their jets do not align with anything like a central rotational axis as in a spiral galaxy. The screw displacement related to frame dragging happens in the near region to the source black holes. Anomalous gas-cloud rotation curves are found in the far region, at the outer edges of galaxies.

jovial_cavalier 4y ago

Also armchair, but this is how I understand it: if you take gravitation as it is typically understood, it implies motion of stars around galaxies which we don't see. The discrepancy can be accounted for if you assume there is 33% more mass than we can traditionally observe, roughly suffusing each galaxy. Since we can't observe it, it's believed to not interact with any normal matter other than through the gravitational field. edit: 33% is definitely wrong, but I don't know the actual number...

potamic 4y ago

Confirmed against every experiment, but not observation. We do not know why galaxies rotate at the speed they do. Apparently we have a pretty good idea of their visible mass, but should result in much slower galaxies than what we observe.

xigency 4y ago
And then how do we know we have an accurate estimation of a stellar object’s mass if the observations don’t match our predictions? This is a big question for me.
- TremendousJudge 4y ago
  Isn't that question why they felt the need to add "dark matter" to the equation? "Our mass estimation must be wrong, therefore there's all this mass we're not seeing"
  - saberdancer 4y ago
    They had to add more matter in some places and less in others. Estimation would have wrong numbers all around.
- potamic 4y ago
  Ok, I wasn't being very accurate. More correctly, we do not know why outer stars in the galaxy rotate at the same speed as inner stars. As per gravitation laws, the farther the star is, the slower it should rotate. But they all rotate at the same speed, which only adds up if you assume there is some "dark matter" around the outside of the galaxy. I honestly do not know how they estimate stellar masses. I suspect they just look at density of stars and have perhaps established that stars are more or less distributed randomly, but I'm armchairing here. Maybe an expert can chime in.
  - trhway 4y ago
    >As per gravitation laws, the farther the star is, the slower it should rotate. That depends. The 1/R orbital speed relationship is valid only in cases of spherically symmetric mass distribution or when the radiuses of the interacting masses being much smaller than the distance between them. Neither of these is true for a star inside a galaxy disk. Correctly accounting for the disk shape gives you expected orbital speed much closer to the "outer stars in the galaxy rotate at the same speed as inner stars", though not exactly equal. The remaining difference is explained by the seond factor. That second factor is that "rotate" i suppose means orbiting around galaxy center. The stars in the disk aren't really orbiting, ie. they are actually flying away like in a fireworks wheel as the galaxy disk becomes larger and thinner - exactly because the stars' speed is still somewhat higher than the orbital speed as calculated above. Thus no need for DM here.