What happens if a black hole collide with another black hole?

[RandomRyan]

Hi!

i thought about something which involves black holes and another black hole.

so i said to myself ( and my sister), ' what happens if a black hole crashes with another black hole?'

gravity anomalies could happen or they 'eat' each other or one of them eats one?

the gravity anomalies might happen.Might.

also i read an article about Magnetars. they are a special kind of neutron stars with a crazy magnetic field

and you do not want to touch a Magnetar. Link :http://www.space.com/30263-paul-sutter-on-why-magnetars-are-scary.html

Thanks in advance

Edited August 15, 2015 by RandomRyan

[ZetaX]

A lot of gravitational waves and energy in general are released when the start their death spiral. The collision of galactic black holes is actually the largest known explosion.

By the way, note that Schwarzschild radius is linear in mass, thus they "plop" together (not literally) instead of merging (as imagined with drops of water).

[Godot]

This video explains it very well:

[K^2]

By the way, note that Schwarzschild radius is linear in mass, thus they "plop" together (not literally) instead of merging (as imagined with drops of water).

Still not really a "plop", because gravity isn't linear. The event horizons do get distorted as the two black holes approach each other. Though, I honestly don't know if event horizons merge, or if a new horizon forms that encloses the two original ones.

[ZetaX]

Still not really a "plop", because gravity isn't linear. The event horizons do get distorted as the two black holes approach each other. Though, I honestly don't know if event horizons merge, or if a new horizon forms that encloses the two original ones.

I said "not literally" for a reason

I expect it to look very unexpected, at the very least for non-physcists. And lets assume no rotations at all, it's already weird enough.

If the imagined former radii touch, then the total radius would already be the sum. In the other hand, I expect them not to look too distorted when still a few radii apart. So something drastical will happen in between.

[1greywind]

I'll add few simulation videos:

Distant view of 2 BH merger:

Simulation of merger between events horizons of 2 black holes with mass ration 2:1 :

Simulated view of 2 black holes merger as seen from some distance over stars background:

http://rebrn.com/re/two-black-holes-merging-animation-120097/

[lajoswinkler]

But what about the relativity of time? All these simulations seem to ignore it.

[ZetaX]

But what about the relativity of time? All these simulations seem to ignore it.

What about it¿ The horizons don't really care and there are not many other things around.

Edit: Ah, I totally missed the first video.

[The Crusher 862]

I'd have expected that as with anything falling into a black hole, both black holes would speed up to the point where time slowed to practically 0 just before they hit each other?

[lajoswinkler]

Yeah, something like that. These simulations are nothing new, been there for ages, but I can't wrap my brain around them when I include the temporal distortion.

[ZetaX]

I'd have expected that as with anything falling into a black hole, both black holes would speed up to the point where time slowed to practically 0 just before they hit each other?

There is a huge difference between the event horizon, which is not an actual thing that experiences slowdown, and the black hole singularities in the center.

Simply put, there is no reason why the horizon itself should show a slowdown; what should that even mean if there is nothing (except space) there¿

[Aethon]

Ok. Tell me where I'm wrong here.

With time dilation and frame dragging, there hasn't been enough time in the history of the universe for even the first black hole to completely collapse into blackholdom, from our frame of reference. Or is time dilation a symptom of relativity's inability to describe what happens beyond the event horizon- ie. anything other than charge, mass, and spin?

[AngelLestat]

Ok. Tell me where I'm wrong here.

With time dilation and frame dragging, there hasn't been enough time in the history of the universe for even the first black hole to completely collapse into blackholdom, from our frame of reference. Or is time dilation a symptom of relativity's inability to describe what happens beyond the event horizon- ie. anything other than charge, mass, and spin?

But we can see the 2 horizons merge and measure the gravity waves that form comming from such dance.

This is because the event horizons are not objects, so there is not time perspective in that point with respect to us, and the singularities are already hide within their horizons.

So there is not time dilation like you imagine, we can see the merge and it would not take infinite time.

[Aethon]

But we can see the 2 horizons merge and measure the gravity waves that form comming from such dance.

Can we?

Have we?

[lajoswinkler]

We never saw or measured those things.

[AngelLestat]

:P:P:P

I was not saying that we actually did, but that we can see it or measure it in theory.

[Scotius]

When it happens, i hope we will be on the other side of the Universe Because we, squishy meatbags have no interest in being anywhere near two such monstrosities going mano-a-mano.

[GeneralVeers]

Hi!

i thought about something which involves black holes and another black hole.

so i said to myself ( and my sister), ' what happens if a black hole crashes with another black hole?'

It's been proven experimentally that time slows down in close proximity to a large mass (a clock on the surface of the Earth runs slower than one in orbit). As you drop an object towards a black hole and watch it fall, it appears to fall more and more slowly--and it never does reach the event horizon. It falls more and more slowly, never quite reaching it.

From our viewpoint, the two black holes will never actually collide. Neither will ever actually cross the event horizon of the other; from our frame of reference, that would take an infinite amount of time to happen. Probably the two masses would form a new event horizon, most likely a kind of oblong shape, and that's all we would ever see (well, aside from whatever interactions of matter would occur outside the new event horizon, anyway).

Ok. Tell me where I'm wrong here.

With time dilation and frame dragging, there hasn't been enough time in the history of the universe for even the first black hole to completely collapse into blackholdom, from our frame of reference. Or is time dilation a symptom of relativity's inability to describe what happens beyond the event horizon- ie. anything other than charge, mass, and spin?

Nothing happens beyond the event horizon. Ever. The event horizon is the point at which time comes to a stop. The real truth is, nothing that has "fallen" into a black hole, at any time in the history of the entire Universe, has ever actually fallen in! It's still falling in, still just above the event horizon, falling towards it infinitely slowly.

[K^2]

It's been proven experimentally that time slows down in close proximity to a large mass (a clock on the surface of the Earth runs slower than one in orbit).

A clock in high orbit runs faster than a clock on Earth. A clock in low orbit actually runs slower, and there is an orbit where clock runs at the same rate as on the surface. Because there is time dilation due to orbital velocity as well.

But yeah, GPS satellites actually have to take gravitational time dilation into account to get the kind of precision they gives you.