What happens if one black hole collides with another?

[Lee]

One for all the science fans:

I was just listening to a song by Fightstar and at one point a bloke states "Well what happens if I want to drop one black hole on another?".

What would happen, GTP?

 

[Kent]

A big bang.

No really, first off, to establish a simple fact... This isn't a spam fest so let's not let it end up that way fellas (this is an edit and I can see my initial comments set the standard low).

That said...
I don't think it is possible for 2 black holes to collide. I believe they are stationary, so it's really a matter of if a black hole can grow.
In the case that it can, I imagine a blackhole will simple swallow another once it has grown to the point of invading the area.
However, since I don't know much about blackholes I will just say this- Interesting thought.

 

[Danny]

A black entity.

 

[Keichi Tsuchiya]

A black UNhole?!

 

[Omnis]

Maybe the gravity becomes neutral and everything gets regurgitated. Perhaps the collision is what keeps the universe from being sucked in.

 

[Kelvari]

I'd suspect that if two black holes were to collide like this....

{black hole A} ----><----{black hole B}

then they'd create a super black hole, similar to what happens if two tornadoes meet (see the movie "The Day After Tomorrow" to see this in action )

If their gravitational wells were what met, instead of the black holes themselves, then I could see it becoming a wormhole, as was mentioned previously

 

[Boundary Layer]

I think the dominant black hole would win out.
I realize gravitational force is dependent on the distance an object is from the source of the gravitational force. But, if one were strong enough shoudln't it be able to suck out whatever the lesser black hole sucked in? You'd effectively create a temporary white hole of the lesser black hole.

 

[Lee]

Trust me to ask the damn question whilst Famine is recharging..

 

[dylansan]

I'm pretty sure they just merge. SInce when does something with high gravity + something with high gravity cancel out? You'd need to have negative gravity...

BL: It would only look like a white hole from the black hole's perspective... It's not emitting matter from one, just pulling it toward another.

 

[Omnis]

Well, with all of these negative mass and black hole questions, let's try keep in mind that this is Ask GTPlanet, not Ask Stephen Hawking.

 

[Kelvari]

And how do you know he's not watching us right now?

 

[Wolfe]

Would it ruin everyone's fun if I posted a link that contains the actual answer?

"Supercomputer simulates black hole collision"

Earlier trials failed since the equations based on Einstein's general relativity theory were so complicated that they made supercomputers crash; the enormous gravity of black holes cause disturbances in time and space, making time stop and space shrink and expand.

NASA researchers have managed to transform the theory into mathematical algorithms and run through it through Columbia, the fourth most powerful supercomputer in the world. Its 2,032 interconnected 512 Intel Itanium 2 processors ran for 80 hours, in an operation that would have taken 18 years for a single processor to perform.

My first thought was something along the lines of a Gamma Ray Burst, but it turns out that the real deal is much greater, and probably much less common...

 

[Famine]

That said...
I don't think it is possible for 2 black holes to collide. I believe they are stationary, so it's really a matter of if a black hole can grow.
In the case that it can, I imagine a blackhole will simple swallow another once it has grown to the point of invading the area.
However, since I don't know much about blackholes I will just say this- Interesting thought.

No - they move. They're just like any other body in that respect - just a hell of a lot stranger.

When two black holes intersect each other, they merge. But I haven't got even the first clue about how this is even possible (each has an event horizon which, once crossed, nothing can escape from - which should include other black holes. So they should both suck the other one in). They also evaporate over time but again I have no clue how this is possible.

Suffice to say that black holes have some of the weirdest physics evAr.

 

[crimson_menace]

Suffice to say that black holes have some of the weirdest physics evAr.

The types of information involved with the outcome of two colliding blackholes is absolutely fascinating.

Chalk up another win for the great one, Famine.

 

[Touring Mars]

I'd suspect that if two black holes were to collide like this....

{black hole A} ----><----{black hole B}

then they'd create a super black hole

If a black hole has infinite density, then I would have thought that if two black holes collided and merged, they would simply become just one black hole, a single entity exactly the same as either one of the original black holes, i.e. 1+1=1...

 

[Keichi Tsuchiya]

Or Maybe, the both join to become ONE infinitely flat region of space. That has infinite gravity... Or maybe, they cancel each other out or even suck each other up as in: <----> <---> <--> <-> <> >< >-< >---<
I don't know... A very interesting question however.

 

[dylansan]

I have no clue.

Sorry, I just had to quote this...

Do black holes have infinite desity? I thought they were strange because they have a lot of gravity (not infinite) and it was enough to suck light in, so it seemed strange. I didn't think anything about them was infinite.

 

[Famine]

The point at the middle of a black hole - the singularity - has no real size but a measurable mass. So yes, it is effectively infinitely dense - and with infinite gravity.

 

[Dave A]

Sorry, I just had to quote this...

Do black holes have infinite desity? I thought they were strange because they have a lot of gravity (not infinite) and it was enough to suck light in, so it seemed strange. I didn't think anything about them was infinite.

They don't have infinite gravity, if they did then nothing would be out of reach from it's gravitational pull.

 

[Famine]

They don't have infinite gravity, if they did then nothing would be out of reach from it's gravitational pull.

But this is true of everything - the Earth's gravitational influence can be felt at the edge of the universe, however faintly...

The singularity at the centre of a black hole does have infinite gravity (probably). It's only once you've moved to the distance of the event horizon (gravity being a function of mass and distance) is it weak enough to not quite capture everything.

 

[Dave A]

Hmmm, ok then but would something having infinite gravity have an infinitly large pull no matter how far away something was. In other words, it's pull would not only be the greatest gravitational pull possible. The pull would be so large, it would never trail off beyond the event horizon. Though then that would create a paradox, if the universe is constanly expanding, the universe is never a set size, so at some point it's inevitable that the event horizon would be reached. i'm either thinking too hard, or not hard enough, the question is which .

 

[Famine]

Hmmm, ok then but would something having infinite gravity have an infinitly large pull no matter how far away something was.

No, because gravity is a function of mass and distance. Black holes have a definite mass, but the black hole itself - the singularity - has no size, thus no distance. As you approach the centre of mass, gravity increases in proportion to the square of the distance from it, so that escape velocity exceeds c as you cross the event horizon, eventually reaching infinite when you reach the centre of mass - but you can't ever reach it as it has no size.

Black hole physics = teh weird.

 

[3-Wheel Drive]

Maybe the two black holes will vanish in a puff of logic.

 

[dylansan]

I don't think a black hole could ever become or emit anything logical, even if two collided...
Edit: Make that "especially" if two collided.

 

[Sage]

3WD wasn&#8217;t being serious &#8211; he was alluding to a Douglas Adams quote (and a very good one at that).

 

[dylansan]

...and I was stating that black holes don't make any sense. Everybody's right!

 

[Philly]

No, because gravity is a function of mass and distance. Black holes have a definite mass, but the black hole itself - the singularity - has no size, thus no distance. As you approach the centre of mass, gravity increases in proportion to the square of the distance from it, so that escape velocity exceeds c as you cross the event horizon, eventually reaching infinite when you reach the centre of mass - but you can't ever reach it as it has no size.

Yes. Gravity is a function of distance and mass. As mass increases while you are the same distance from an object, gravity increases. As you get closer to an object, your gravitational attraction increases too.

How does an object with mass have a size of zero? That seems a bit wierd, but then again, we don't understand these phenomena well.

Because it has a size of 0, if I get trapped in a black hole, i will be approaching something that doesn't exist, right? So that is why I will never get there? Could it be likened to the limit as X->0 of 1/x; seeing as how it approaches infinity but never gets there because infinity does not exist? So, is the center of a black hole an idea, like infinity?

 

[Boundary Layer]

As you approach the centre of mass, gravity increases in proportion to the square of the distance from it

I believe you mean in proportion to the inverse square of the distance - otherwise it'd have no gravitational force at the center of mass.

How does an object with mass have a size of zero? That seems a bit wierd, but then again, we don't understand these phenomena well.

A compressive force of infinite magnitude will compress matter to an infinitely small size.

Could it be likened to the limit as X->0 of 1/x; seeing as how it approaches infinity but never gets there because infinity does not exist? So, is the center of a black hole an idea, like infinity?

That's exactly how I was thinking of it. X being the displacement between the body and the blackhole's center of mass, and the gravitational force being some function that approaches infinity as X becomes infinitely small. As Famine no doubt meant, if you assume the blackhole has a constant mass, the gravitational force is approximately G(X)=C(X^-2), where C is some constant for god knows what (and I say approximately because I have no idea if/how electromagnetism factors in to this).

I believe the key to understanding the concept is not to think about continuously decreasing the distance between the center of mass and some body pulled towards it by some exact amount, but by a fraction of the remaining displacement. It's like the paradox about the man travelling from city A to B by only moving half the remaining distance at a time. First he travels 1/2 the distance, then finds himself at 3/4, then 7/8ths, 15/16ths, etc... He never makes it to city B. I think this is the same idea.

 

[Famine]

I believe you mean in proportion to the inverse square of the distance - otherwise it'd have no gravitational force at the center of mass.

Well, I chose not to make it more complex than it already is. You're right in that the increase is proportional to the inverse square of the change in distance - I just chose to simplify it. There's enough bafflement in here as it is!


1/2 the distance, 4 times the gravity.
1/3 the distance, 9 times the gravity.

 

[Bram Turismo]

They also evaporate over time but again I have no clue how this is possible.

I think that rather depends on the mass of the black hole. Black holes evaporate due to energy loss but I don't see a supermassive black hole evaporating as it swallows more energy then it loses...


As I've read...