Scientists confirm that the first black hole ever imaged is actually spinning::The first black hole humanity has ever imaged has also provided us with what researchers are calling “unequivocal evidence” that black holes spin.

  • hotdaniel
    link
    fedilink
    English
    arrow-up
    7
    arrow-down
    2
    ·
    1 year ago

    Does the black hole spin? Or does the stuff outside the black hole spin? 🤔

    • AbouBenAdhem@lemmy.world
      link
      fedilink
      English
      arrow-up
      20
      ·
      1 year ago

      The black hole and the stuff outside it constitute a single system, and within that system, angular momentum is conserved. So as objects cross the event horizon, their angular momentum is transferred to the black hole.

      • hotdaniel
        link
        fedilink
        English
        arrow-up
        3
        arrow-down
        2
        ·
        1 year ago

        Well… does it? If all the stuff falls in and only the volume remains, who could say that it’s spinning? How could you detect it?

        • AbouBenAdhem@lemmy.world
          link
          fedilink
          English
          arrow-up
          12
          ·
          edit-2
          1 year ago

          For one thing, the size and shape of the event horizon change depending on the black hole’s spin.

          • hotdaniel
            link
            fedilink
            English
            arrow-up
            2
            arrow-down
            1
            ·
            1 year ago

            I see. Thank you. So, you can use light to infer the mass, and then the volume information to infer the spin? Easy enough.

            • AbouBenAdhem@lemmy.world
              link
              fedilink
              English
              arrow-up
              3
              ·
              edit-2
              1 year ago

              That would be a general method, if we were close enough to observe the shape of the event horizon (which we aren’t).

              The article is describing another way, which only works in this case because the black hole is precessing so extremely that the changing axis of rotation is frame-dragging the polar jets along with it.

        • Fungah@lemmy.world
          link
          fedilink
          English
          arrow-up
          1
          ·
          1 year ago

          I thought nothing actually crossed the event horizon and was essentially frozen approaching a complete stop in time in a kind of 2f representation of 3d reality until it slowly leaked out trillions of years later as hawking radiation?

          • hotdaniel
            link
            fedilink
            English
            arrow-up
            1
            arrow-down
            1
            ·
            1 year ago

            From an outsider’s perspective, you would see an object approach and then freeze. It would red-shift dimmer until it disappeared. From an in-falling perspective, I don’t think you’d notice anything at all.

    • scarabic@lemmy.world
      link
      fedilink
      English
      arrow-up
      6
      ·
      1 year ago

      Isn’t most everything spinning? Seems like having zero angular momentum would be rare and remarkable. I’m not even sure how exactly to define zero momentum in terms of reference frames.

    • DreamButt@lemmy.world
      link
      fedilink
      English
      arrow-up
      2
      ·
      1 year ago

      If you’re asking that then you first need to ask what the distinction between the two is. and further does it even make sense for one to spin and not the other

      • NewNewAccount@lemmy.world
        link
        fedilink
        English
        arrow-up
        1
        ·
        1 year ago

        Is there not a distinction? I assume the singularity at its center has different properties than the matter outside of that point.

        Note: I have a rudimentary understanding of what black holes and their components are.

        • Telodzrum@lemmy.world
          link
          fedilink
          English
          arrow-up
          1
          ·
          1 year ago

          Even if there is heterogeneity inside the system, that does not indicate severability or that the whole system is made up of smaller constituent systems.

    • KidsTryThisAtHome@lemm.ee
      link
      fedilink
      English
      arrow-up
      1
      ·
      1 year ago

      It’s in space and everything is relative, how do we know *everything else" isn’t just spinning around the black hole? 🤔

      • Devion@feddit.nl
        link
        fedilink
        English
        arrow-up
        1
        arrow-down
        1
        ·
        1 year ago

        Because that would require a centripetal force on everything else, which obviously isn’t the case.