Could a Black Hole destroy a whole galaxy?

[Newtype_A]

Pretty much ANYTHING could destroy a whole galaxy, given enough time. The better question is, could a black whole destroy a whole galaxy before every star in that entire galaxy completely burned out and the universe as we know it fizzled out like a firecracker?

No, it couldn't. Even if you found a black hole that was big enough to plausibly cause that kind of destruction (remember, galaxies are So Big, So Absolutely Huge...) the more likely result would be that most of the galaxy would end up in orbit of the black hole; wouldn't destroy it, just change shape.

 

[Newtype_A]

Neopeius said:
The event horizon of a sun is 3km. The event horizon the only applicable way to measure the *size* of black hole, as opposed to its mass. Because a black hole is always in the act of contracting, it does not have a measurable radius.

Not really. The sun would still be a black hole even if the Borg came along and crushed it down to a mass 2.9 kilometers wide. The only thing that MAKES it a black hole in the first place is the fact that you can't see it, because it's smaller than it's own Swartzchild Radius. All that would mean is that there's a region 100 meters thick where the acceleration due to gravity is equal to or slightly greater than the speed of light.

No reason why it would be constantly collapsing, and since physicists don't really have any idea how (or if) the laws of physics work under those conditions, there plenty of speculation but very little fact.

 

[Neopeius]

Newtype_A said:

Neopeius said:
The event horizon of a sun is 3km. The event horizon the only applicable way to measure the *size* of black hole, as opposed to its mass. Because a black hole is always in the act of contracting, it does not have a measurable radius.

Not really. The sun would still be a black hole even if the Borg came along and crushed it down to a mass 2.9 kilometers wide. The only thing that MAKES it a black hole in the first place is the fact that you can't see it, because it's smaller than it's own Swartzchild Radius. All that would mean is that there's a region 100 meters thick where the acceleration due to gravity is equal to or slightly greater than the speed of light.

No reason why it would be constantly collapsing, and since physicists don't really have any idea how (or if) the laws of physics work under those conditions, there plenty of speculation but very little fact.

I thought the whole point was that it takes an infinite amount of time to get from the event horizon to the center because of the relativistic differential involved. A black hole is a very specific condition, a sort of funnel-shaped piece of energy. No matter can withstand that kind of density.

So it's meaningless to talk of diameters or shapes of a black hole. They don't really have one. All they have is an event horizon.

 

[Chaos Descending]

Neopeius said:
So it's meaningless to talk of diameters or shapes of a black hole. They don't really have one. All they have is an event horizon.

Well, when it comes right down to it, it's not exactly wrong to refer to the surface of the event horizon as the "surface" of the black hole itself.

 

[Neopeius]

Chaos Descending said:

Neopeius said:
So it's meaningless to talk of diameters or shapes of a black hole. They don't really have one. All they have is an event horizon.

Well, when it comes right down to it, it's not exactly wrong to refer to the surface of the event horizon as the "surface" of the black hole itself.

It's certainly true that the event horizon is the only meaningful boundary to a black hole.

 

[Hippokrene]

Johnny Rico said:

Secondly, not all black holes, massive or not, are always active. Active, as in actually sucking things in. They go dormant just like volcanoes go dormant.

Could you elaborate on this? Are you saying the gravitational field of a black hole sometimes turns off?

 

[iguana_tonante]

^Of course not. It just happens that there are moments in a black hole's life where there are not available matter to suck in, so it sucks nothing. When matter passes by, the black hole sucks it, and if the conditions are right, the super-heated matter it will emit X-ray radiation during its fall.

 

[splodenode]

why dont the x-rays get sucked in too?

 

[iguana_tonante]

^Because they are emitted outside of the event horizon.