5 ms·

How To Destroy A Black Hole

28 points by cwan 16y ago

chc 16y ago
Such a melodramatic way of describing it. It's like going out to get a haircut and telling people, "I'm destroying my head!" because you feel so attached to the hairdo. A better way to put it would be: They want to look behind the black hole's even horizon. They they that if they spin a black hole fast enough, its event horizon will contract and eventually disappear, revealing the singularity (whatever that means in real-world terms). Nothing is actually being destroyed — they're just changing the way the singularity's gravity behaves.
- Groxx 16y ago
  Well yeah, if getting a haircut let people peer into your brain and possibly even see what's going on and how the whole thing works. If that were the case, the first person to get a haircut would become the center of massive scientific interest. Even someone considering it / how to do it would be worth discussing.
sliverstorm 16y ago
When I read the title, I thought "sweet! They are going to make 2 black holes collide! The universe will probably end, but it will be awesome" When I read the article, I decided you probably can't add charge to a black hole in any meaningful amount, so you need to add angular velocity. What's the only way to indirectly add angular velocity to an object you can't touch or get close to? With gravity. With another black hole. They are going to make 2 black holes collide. And it will be awesome.
- j_baker 16y ago
  That happens all the time (in astronomical terms). For instance, when two galaxies collide.
ars 16y ago
It's called a http://en.wikipedia.org/wiki/Naked_singularity http://en.wikipedia.org/wiki/Naked_singularity
mpk 16y ago
"[..] removing the event horizon around a black hole[..]" If somebody could take the time to explain this I would very much appreciate it.
- stretchwithme 16y ago
  not sure exactly what you need to have explained, but wikipedia say the event horizon is "an event horizon is a boundary in spacetime, most often an area surrounding a black hole, beyond which events cannot affect an outside observer." so if you could remove the event horizon somehow, you could see what's going on with the black hole. It would look smaller too, because light from behind the black hole could get here, rather than being pulled in to the hole.
  - mpk 16y ago
    I understand what an event horizon is. What I don't understand is how you could remove one.
    - joeyo 16y ago
      From the article: M^2 >= (J/M)^2 + Q^2 M is the mass of the black hole, J is its angular momentum, and Q is its charge. If the inequality is satisfied, that is it has sufficiently more mass than angular momentum and charge, then the black hole has an event horizon. However if the inequality is violated, either because of additional charge, or angular momentum, or both, then the black hole would have no event horizon and would exist as a naked singularity. This is generally regarded as a nonphysical solution-- large charged bodies tend not to exist in nature, and presumably any body that had sufficient angular momentum to push the black hole into violating the inequality would also have sufficient angular momentum to avoid falling into the back hole as well, but the authors of the paper have apparently devised some situation where the blackhole can be pushed into such a regime.
- keefe 16y ago
  I found this kind of a very odd statement. Isn't the event horizon a consequence of the stuff going on underneath? The image I have in my mind is of water draining out of the tub and wanting to strip off the top layer of water to see what's "going on" inside the whirlpool, when of course stripping off one top only reveals another and so forth.
Jach 16y ago
I thought we already knew how to destroy black holes by evaporating them... Anyway, now seems like a good time to submit this: http://news.ycombinator.com/item?id=1425544 http://news.ycombinator.com/item?id=1425544 He claims the mathematical basis for black holes from general relativity is false; I don't possess the math skills to really go over his claims.
- keefe 16y ago
  my understanding is they naturally evaporate over time, a process we can't really impact but which is significant because... if a black hole that has sucked in M units of mass evaporates, where does the mass go?
  - hammerdr 16y ago
    We can theoretically impact it. Antimatter slowly falls into the black hole and decreases its mass until there isn't enough gravity to maintain a black hole (and then you have a massive explosion). So, in theory, if we could somehow acquire antimatter and throw it at a black hole, we could 'evaporate' the black hole faster. We better run fast though :) It's fascinating how this actually happens. There are twin particles of matter/anti-matter appearing and disappearing throughout the universe. They exist for only a fraction of a second. However, at the edge of a black hole, the matter is pushed away and the antimatter is sucked in. The matter is what creates the 'glow' of the black hole and the antimatter is just decreasing the mass of the black hole. So, evaporation is a bit of a misnomer because nothing is escaping.
    - ars 16y ago
      That is completely wrong. > Antimatter slowly falls into the black hole and decreases its mass If you dropped anti matter in a black hole, it just gets heavier. Matter is energy, anti matter is also energy. Energy has mass. It makes no difference what kind it was. > there isn't enough gravity to maintain a black hole (and then you have a massive explosion). No. The black hole simply gets smaller - at no point does it ever stop being a black hole. > There are twin particles of matter/anti-matter appearing and disappearing throughout the universe. They exist for only a fraction of a second. However, at the edge of a black hole, the matter is pushed away and the antimatter is sucked in. No. The idea with virtual particles is that one of them escapes. You create two particles at once, one escapes, the other falls in. These particles are created by the black hole. Twin particles do not constantly appear and disappear through the universe. That would violate conservation of momentum. And it could just as easily be reversed, with the matter falling in, and the anti matter escaping. And anyway, most of the time it's photons that escape, and they are not matter or anti matter. > The matter is what creates the 'glow' of the black hole and the antimatter is just decreasing the mass of the black hole. No. The glow is photons. And the antimatter is not decreasing the mass - the escaping photons are what decreases the mass. You can think of it as a small chuck of the mass of the black hole appears at the edge. Half falls back in, half escapes. > So, evaporation is a bit of a misnomer because nothing is escaping. Not correct. Energy is escaping.
ck2 16y ago
I've always had a theory you can make a black hole visible again by "simply" increasing it's surface area enough. Eventually there will be enough area to reduce gravity just enough for light to escape.
- RevRal 16y ago
  Doesn't a black hole already have a huge surface area in space-time?
  - ck2 16y ago
    No, that's the problem, it has immense mass with no surface. increasing surface area overcomes gravity of the overall mass Basically you'd have to make it less dense to make it visible. Maybe changing it from a sphere into a flat surface somehow like the difference between a golf ball and a sheet of paper. The density of a pinhead area on a golf ball is higher than a pinhead of surface area on a sheet of paper, even if they theoretically were made to have the same mass overall.
- eru 16y ago
  How should this work?
- pontifier 16y ago
  There is no surface to a black hole. The event horizon is an imaginary shell around the singularity that symbolises the place where the escape velocity = the speed of light. If you have a body that does not have an event horizon, you have a body with no singularity similar to a regular star or even the earth.
Tycho 16y ago
Imagine if the contents turned out simply to be the last thing that went in, ie. the universe could no longer resize that particular array so just had to overwrite the contents each time.

28 points by cwan 16y ago

chc 16y ago

Such a melodramatic way of describing it. It's like going out to get a haircut and telling people, "I'm destroying my head!" because you feel so attached to the hairdo. A better way to put it would be: They want to look behind the black hole's even horizon. They they that if they spin a black hole fast enough, its event horizon will contract and eventually disappear, revealing the singularity (whatever that means in real-world terms). Nothing is actually being destroyed — they're just changing the way the singularity's gravity behaves.

Groxx 16y ago
Well yeah, if getting a haircut let people peer into your brain and possibly even see what's going on and how the whole thing works. If that were the case, the first person to get a haircut would become the center of massive scientific interest. Even someone considering it / how to do it would be worth discussing.

sliverstorm 16y ago

When I read the title, I thought "sweet! They are going to make 2 black holes collide! The universe will probably end, but it will be awesome" When I read the article, I decided you probably can't add charge to a black hole in any meaningful amount, so you need to add angular velocity. What's the only way to indirectly add angular velocity to an object you can't touch or get close to? With gravity. With another black hole. They are going to make 2 black holes collide. And it will be awesome.

j_baker 16y ago
That happens all the time (in astronomical terms). For instance, when two galaxies collide.

ars 16y ago

It's called a http://en.wikipedia.org/wiki/Naked_singularity http://en.wikipedia.org/wiki/Naked_singularity

mpk 16y ago

"[..] removing the event horizon around a black hole[..]" If somebody could take the time to explain this I would very much appreciate it.

stretchwithme 16y ago
not sure exactly what you need to have explained, but wikipedia say the event horizon is "an event horizon is a boundary in spacetime, most often an area surrounding a black hole, beyond which events cannot affect an outside observer." so if you could remove the event horizon somehow, you could see what's going on with the black hole. It would look smaller too, because light from behind the black hole could get here, rather than being pulled in to the hole.
- mpk 16y ago
  I understand what an event horizon is. What I don't understand is how you could remove one.
  - joeyo 16y ago
    From the article: M^2 >= (J/M)^2 + Q^2 M is the mass of the black hole, J is its angular momentum, and Q is its charge. If the inequality is satisfied, that is it has sufficiently more mass than angular momentum and charge, then the black hole has an event horizon. However if the inequality is violated, either because of additional charge, or angular momentum, or both, then the black hole would have no event horizon and would exist as a naked singularity. This is generally regarded as a nonphysical solution-- large charged bodies tend not to exist in nature, and presumably any body that had sufficient angular momentum to push the black hole into violating the inequality would also have sufficient angular momentum to avoid falling into the back hole as well, but the authors of the paper have apparently devised some situation where the blackhole can be pushed into such a regime.
keefe 16y ago
I found this kind of a very odd statement. Isn't the event horizon a consequence of the stuff going on underneath? The image I have in my mind is of water draining out of the tub and wanting to strip off the top layer of water to see what's "going on" inside the whirlpool, when of course stripping off one top only reveals another and so forth.

Jach 16y ago

I thought we already knew how to destroy black holes by evaporating them... Anyway, now seems like a good time to submit this: http://news.ycombinator.com/item?id=1425544 http://news.ycombinator.com/item?id=1425544 He claims the mathematical basis for black holes from general relativity is false; I don't possess the math skills to really go over his claims.

keefe 16y ago
my understanding is they naturally evaporate over time, a process we can't really impact but which is significant because... if a black hole that has sucked in M units of mass evaporates, where does the mass go?
- hammerdr 16y ago
  We can theoretically impact it. Antimatter slowly falls into the black hole and decreases its mass until there isn't enough gravity to maintain a black hole (and then you have a massive explosion). So, in theory, if we could somehow acquire antimatter and throw it at a black hole, we could 'evaporate' the black hole faster. We better run fast though :) It's fascinating how this actually happens. There are twin particles of matter/anti-matter appearing and disappearing throughout the universe. They exist for only a fraction of a second. However, at the edge of a black hole, the matter is pushed away and the antimatter is sucked in. The matter is what creates the 'glow' of the black hole and the antimatter is just decreasing the mass of the black hole. So, evaporation is a bit of a misnomer because nothing is escaping.
  - ars 16y ago
    That is completely wrong. > Antimatter slowly falls into the black hole and decreases its mass If you dropped anti matter in a black hole, it just gets heavier. Matter is energy, anti matter is also energy. Energy has mass. It makes no difference what kind it was. > there isn't enough gravity to maintain a black hole (and then you have a massive explosion). No. The black hole simply gets smaller - at no point does it ever stop being a black hole. > There are twin particles of matter/anti-matter appearing and disappearing throughout the universe. They exist for only a fraction of a second. However, at the edge of a black hole, the matter is pushed away and the antimatter is sucked in. No. The idea with virtual particles is that one of them escapes. You create two particles at once, one escapes, the other falls in. These particles are created by the black hole. Twin particles do not constantly appear and disappear through the universe. That would violate conservation of momentum. And it could just as easily be reversed, with the matter falling in, and the anti matter escaping. And anyway, most of the time it's photons that escape, and they are not matter or anti matter. > The matter is what creates the 'glow' of the black hole and the antimatter is just decreasing the mass of the black hole. No. The glow is photons. And the antimatter is not decreasing the mass - the escaping photons are what decreases the mass. You can think of it as a small chuck of the mass of the black hole appears at the edge. Half falls back in, half escapes. > So, evaporation is a bit of a misnomer because nothing is escaping. Not correct. Energy is escaping.

ck2 16y ago

I've always had a theory you can make a black hole visible again by "simply" increasing it's surface area enough. Eventually there will be enough area to reduce gravity just enough for light to escape.

RevRal 16y ago
Doesn't a black hole already have a huge surface area in space-time?
- ck2 16y ago
  No, that's the problem, it has immense mass with no surface. increasing surface area overcomes gravity of the overall mass Basically you'd have to make it less dense to make it visible. Maybe changing it from a sphere into a flat surface somehow like the difference between a golf ball and a sheet of paper. The density of a pinhead area on a golf ball is higher than a pinhead of surface area on a sheet of paper, even if they theoretically were made to have the same mass overall.
eru 16y ago
How should this work?
pontifier 16y ago
There is no surface to a black hole. The event horizon is an imaginary shell around the singularity that symbolises the place where the escape velocity = the speed of light. If you have a body that does not have an event horizon, you have a body with no singularity similar to a regular star or even the earth.

Tycho 16y ago

Imagine if the contents turned out simply to be the last thing that went in, ie. the universe could no longer resize that particular array so just had to overwrite the contents each time.