# Is it possible to distort a black hole's event horizon

• I
• dratone
In summary: You can't actually get the maximum possible spin, because that would require infinite energy, but you can get close enough that the amount of energy radiated away in GWs is close to the total mass of the initial holes. This is called a "maximally spinning" merger. It's not clear to me exactly what you mean by "half of total mass of all BH inflicted" though.In summary, the conversation discusses the possibility of retrieving a probe that has fallen into a black hole by using the mass and space-time warping of a second black hole to manipulate the event horizon of the first black hole. However, this is not possible as the event horizon of a black hole cannot be distorted. The conversation also mentions the release of
dratone
I know this is (probably) not going to work.. But I can't figure out why not :-)

So here is the theoretical situation...

Lets say we have 2 black holes that, somehow, we can perfectly control (velocity, position, rotation etc. etc.).
Now, one of my probes accidentally falls into one of the black holes and I really want it back..

Could you use the second black hole's mass (and corresponding space-time warping) to distort the first black hole's event horizon enough to get to the probe?

From what I've gathered, the reason the very-very early universe didn't collapse into a black hole is because the gravitational warping of space time was uniform enough not to collapse into a black hole - i.e., the gravitational pull was equal in all directions.

My idea would be that the above situation would be somewhat similar - the gravitational bending of space time caused by the second black hole could be used to interfere with the gravitational bending of the first black hole, causing the event horizon of the first black hole to be pushed inward. And, if so, could we use that to "uncover" the black hole and retrieve something that fell into it (very recently)? Or is there some kind of general/special relativity mechanic that I'm not taking into account here?

dratone said:
Could you use the second black hole's mass (and corresponding space-time warping) to distort the first black hole's event horizon enough to get to the probe?

No.

dratone said:
the reason the very-very early universe didn't collapse into a black hole is because the gravitational warping of space time was uniform enough not to collapse into a black hole - i.e., the gravitational pull was equal in all directions

No, that's not correct. The reason the early universe didn't collapse into a black hole was that it was expanding rapidly.

It is instead possible if we have 2 colliding black holes to get energy out of the collision in the form of GW.
It's possible that what is left of your "probe" (or at least parts of it) could have been converted into gravitational waves during the collision.

https://en.wikipedia.org/wiki/List_of_gravitational_wave_observations
https://en.wikipedia.org/wiki/Gravitational_wave

Like on 14 September 2015 from 1.3 billion light years away distant merger of two black holes,
36 solar masses and 29 solar masses, resulting in a 62 solar masses black hole with the rest of 3 solar masses = 5.4×1047 Jules "radiated" as gravitational waves.

Accurate simulations of black holes merger can help you understand what and how things evolve during such an event.

I recommend you this lecture like article http://www.ihes.fr/~damour/Conferences/Damour_2body_EHLERS2010.pdf regarding "The Two-Body Problem in General Relativity" by Thibault Damour from Institut des Hautes Etudes Scientifiques (Bures-sur-Yvette, France).

Mihai_B said:
It is instead possible if we have 2 colliding black holes to get energy out of the collision in the form of GW.

The GW radiation does not come from "distorting the event horizon", at least not if you interpret that as allowing anything that was inside the horizon to escape. Nothing that once gets inside the horizon can escape (at least not if we are talking about classical GR, which I assume we are in this discussion). The GW radiation comes from the merging of the horizons of the two holes into one; the initial merged horizon is not symmetrical, and the asymmetries are radiated away as GWs. The energy contained in the GWs was stored in spacetime curvature outside the horizon(s); it does not come from inside.

@PeterDonis : I concur.

Also using multiple collisions with what remains from previous collisions (maybe 3BP- 3body problems or why not - 5 or more - colliding BH) - aka complicated collisions between multiple spinning BH (anyways, all BHs actually do have some spin, but we approximate this in some certain conditions in order to get simpler equations) - could be "engineered" to release great amount of energy - like half of total mass of all BH inflicted (?) maybe even more (or less). Engineered aka not quite "natural" occurring or rarely occurring in nature (merging of multiple galaxies ?)...

Mihai_B said:
half of total mass of all BH inflicted

You can get close to this if you take two non-rotating holes and merge them in such a way that the final hole has close to the maximum possible spin for its mass.

Mihai_B

## 1. Can anything distort a black hole's event horizon?

Yes, there are several things that can potentially distort a black hole's event horizon, including the rotation of the black hole, the presence of nearby massive objects, and the effects of gravitational waves.

## 2. How does the rotation of a black hole affect its event horizon?

The rotation of a black hole can cause its event horizon to bulge outward, creating an oblate shape instead of a perfect sphere. This is known as the "frame-dragging" effect and is caused by the strong gravitational pull of the rotating black hole.

## 3. Can the presence of nearby massive objects distort a black hole's event horizon?

Yes, the gravitational pull of nearby massive objects can cause the event horizon of a black hole to become distorted. This is known as the "tidal effect" and is similar to the way that the moon's gravity causes tides on Earth.

## 4. How do gravitational waves affect a black hole's event horizon?

Gravitational waves are ripples in the fabric of spacetime that can be caused by the movement of massive objects. When these waves pass through a black hole, they can cause small fluctuations in the shape of its event horizon. However, these fluctuations are extremely small and are not expected to have a significant impact on the overall structure of the black hole.

## 5. Is it possible to artificially distort a black hole's event horizon?

Currently, there is no known way to artificially distort a black hole's event horizon. The extreme gravitational forces and conditions near a black hole make it difficult to manipulate in any way. However, as technology and our understanding of black holes improve, it may become possible in the future.

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