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> Slight problem with this is that you can’t touch black holes, so there’s nothing to hold them with. A black hole isn’t really anything, it’s just strongly cur

> Slight problem with this is that you can’t touch black holes, so there’s nothing to hold them with. A black hole isn’t really anything, it’s just strongly curved space. They can be electrically charged but since they radiate they’ll shed their electric charge quickly, and then they are neutral again and electric fields won’t hold them. So some engineering challenges that remain to be solved. im not even sure how to begin there... probably the only wait contain a black hole would be... warping space-time negatively? like kind of warp bubble?

XorNot 4y ago
It's just a gravitationally attractive body: it moves towards the net gravitational force acting on it. So you could control it by trucking sufficiently large masses closer or farther away within a suitably large containment area, provided it wasn't too massive. Easiest thing to do though would be to build it in orbit.
- GlenTheMachine 4y ago
  Good way to clean up space junk
  - swayvil 4y ago
    Unlike the trash bucket in Linux. 1 time out of 20 you go back and restore that thing you trashed. And damn glad you are to have that power. Black holes, otoh, are forever.
    - platz 4y ago
      they are not forever.
      - swayvil 4y ago
    - hammyhavoc 4y ago
      How on Earth did you twist this discussion about blackholes to bring up Linux?
      - swayvil 4y ago
        The whole idea of irrevocable trash disposal vs the less irrevocable kind.
  - fennecfoxen 4y ago
    No better than any random orbiting lump with the same mass, and quite possibly worse. If you want to clean space debris put up something like a big disc of aerogel.
deleted 4y ago
[deleted]
mrfusion 4y ago
I’d imagine you could keep feeding it an electric charge to counter any charge it loses.
snarfy 4y ago
> They can be electrically charged but since they radiate they’ll shed their electric charge quickly This view is not right, e.g. electrons radiate and keep their charge. Black holes lose their electric charge when opposite charged matter falls in.
- deleted 4y ago
  [deleted]
- theptip 4y ago
  Electrons can’t lose their charge through radiation because they can’t have fractional charge. They radiate photons to lose momentum. (They can become uncharged by combining, eg e+P = N). A black hole can presumably radiate charged Hawkings radiation? I.e. if an electron-positron pair is created near the event horizon of a negatively-charged black hole then it would disproportionately capture positrons and repel electrons, thus radiating away its charge. (Could be wrong here, I’ve not looked into charged black holes before). I would assume here that charge radiates away at a different rate than mass, and by her statements it sounds like ch argue evaporates away quicker. She’s not making a general claim that “everything that radiates loses charge”, that would be silly.
magicalhippo 4y ago
I recall reading that any magnetic fields present when the black hole formed would be "frozen in place". If so, couldn't that be used? That said, I found that very surprising and expected the magnetic fields to disappear, so maybe I misunderstood something.
kevin_thibedeau 4y ago
You can put a small one in orbit around a body of mass. Or let it orbit inside and wait for the spectacle.
- blincoln 4y ago
  I skimmed over Crane and Westmoreland's paper[1] and an article that discusses specific designs[2], and I'm still unsure how one would keep the vehicle and black hole moving together while also generating thrust. It seems like there would be a conservation of energy problem, regardless of the design. I'm not a physicist, so I'm probably missing something. Most things one would use for thrust in space are inherently repulsive. The part I'm having trouble with is that it seems like even though a black hole would put out a lot of energy, it wouldn't be inherently repulsive, and so any vehicle would have to exert a station-keeping (or orbit-keeping) force equivalent to whatever the over-all black hole engine was emitting, making the engine itself useless. This seems especially true for the design in the second article, where the Dyson shell weighs 600 times as much as the singularity. But again, I'm probably missing something obvious since it's outside my areas of expertise. [1] https://arxiv.org/abs/0908.1803 https://arxiv.org/abs/0908.1803 [2] https://www.space.com/24306-interstellar-flight-black-hole-power.html https://www.space.com/24306-interstellar-flight-black-hole-p...

XorNot 4y ago

It's just a gravitationally attractive body: it moves towards the net gravitational force acting on it. So you could control it by trucking sufficiently large masses closer or farther away within a suitably large containment area, provided it wasn't too massive. Easiest thing to do though would be to build it in orbit.

GlenTheMachine 4y ago
Good way to clean up space junk
- swayvil 4y ago
  Unlike the trash bucket in Linux. 1 time out of 20 you go back and restore that thing you trashed. And damn glad you are to have that power. Black holes, otoh, are forever.
  - platz 4y ago
    they are not forever.
    - swayvil 4y ago
  - hammyhavoc 4y ago
    How on Earth did you twist this discussion about blackholes to bring up Linux?
    - swayvil 4y ago
      The whole idea of irrevocable trash disposal vs the less irrevocable kind.
- fennecfoxen 4y ago
  No better than any random orbiting lump with the same mass, and quite possibly worse. If you want to clean space debris put up something like a big disc of aerogel.

deleted 4y ago

[deleted]

mrfusion 4y ago

I’d imagine you could keep feeding it an electric charge to counter any charge it loses.

snarfy 4y ago

> They can be electrically charged but since they radiate they’ll shed their electric charge quickly This view is not right, e.g. electrons radiate and keep their charge. Black holes lose their electric charge when opposite charged matter falls in.

deleted 4y ago
[deleted]
theptip 4y ago
Electrons can’t lose their charge through radiation because they can’t have fractional charge. They radiate photons to lose momentum. (They can become uncharged by combining, eg e+P = N). A black hole can presumably radiate charged Hawkings radiation? I.e. if an electron-positron pair is created near the event horizon of a negatively-charged black hole then it would disproportionately capture positrons and repel electrons, thus radiating away its charge. (Could be wrong here, I’ve not looked into charged black holes before). I would assume here that charge radiates away at a different rate than mass, and by her statements it sounds like ch argue evaporates away quicker. She’s not making a general claim that “everything that radiates loses charge”, that would be silly.

magicalhippo 4y ago

I recall reading that any magnetic fields present when the black hole formed would be "frozen in place". If so, couldn't that be used? That said, I found that very surprising and expected the magnetic fields to disappear, so maybe I misunderstood something.

kevin_thibedeau 4y ago

You can put a small one in orbit around a body of mass. Or let it orbit inside and wait for the spectacle.

blincoln 4y ago
I skimmed over Crane and Westmoreland's paper[1] and an article that discusses specific designs[2], and I'm still unsure how one would keep the vehicle and black hole moving together while also generating thrust. It seems like there would be a conservation of energy problem, regardless of the design. I'm not a physicist, so I'm probably missing something. Most things one would use for thrust in space are inherently repulsive. The part I'm having trouble with is that it seems like even though a black hole would put out a lot of energy, it wouldn't be inherently repulsive, and so any vehicle would have to exert a station-keeping (or orbit-keeping) force equivalent to whatever the over-all black hole engine was emitting, making the engine itself useless. This seems especially true for the design in the second article, where the Dyson shell weighs 600 times as much as the singularity. But again, I'm probably missing something obvious since it's outside my areas of expertise. [1] https://arxiv.org/abs/0908.1803 https://arxiv.org/abs/0908.1803 [2] https://www.space.com/24306-interstellar-flight-black-hole-power.html https://www.space.com/24306-interstellar-flight-black-hole-p...