Once you enter the event horizon of a black hole, you will never leave it. There is no speed you can pick up, not even the speed of light, to get you out. But in general relativity, space is curved in the presence of mass and energy, and black hole merging is one of the most extreme scenarios for such curvature. Is there some way to get into a black hole, cross the event horizon and then leave when the event horizon is curved by a massive merger?
When two black holes merge, can matter within the event horizon of one black hole escape? Can they pick up and migrate to another (more massive black hole)? How about going beyond both horizons?
This idea is definitely crazy. But is she crazy enough to work? Physicist Ethan Siegel will help us answer this question.
When a sufficiently massive star ceases to exist, or when two sufficiently massive stellar remnants merge, a black hole can form with an event horizon proportional to its mass and an accretion disk in which the matter surrounding the black hole swirls.
A black hole, as a rule, forms during the collapse of the core of a massive star, either after a supernova explosion, or a merger of neutron stars, or during a direct collapse. As far as we know, every black hole is formed from matter that has ever been part of a star, so in many ways, black holes are the ultimate remnants of stars. Some black holes form in isolation; others become part of a dual system. Over time, black holes can not only spiral and coalesce, but also absorb other matter that falls into the event horizon.
In a Schwarzschild black hole, falling inward leads to singularity and darkness. No matter which direction you are traveling, how you accelerate, and so on, crossing the event horizon means an inevitable collision with a singularity.
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When anything crosses the black hole event horizon from the outside, it is doomed. In a matter of seconds, the object will reach a singularity at the center of the black hole: points for a non-rotating black hole and rings for a rotating one. The black hole itself does not remember which particles fell into it or what their quantum state is. Instead, all that remains, in terms of information, is the total mass, charge, and angular momentum of the black hole.
In the final stage, prior to the merger, the spacetime surrounding the black hole will be disrupted as matter continues to fall into both black holes from the environment. Under no circumstances should you assume that something can escape from within the event horizon.
Thus, one can imagine a scenario in which matter falls into a black hole during the final stages of a merger, when one black hole is about to merge with another. Since black holes must always have accretion disks, and matter is constantly flying in the interstellar medium, particles will constantly cross the event horizon. Everything is simple here, so let's consider a particle that fell into the event horizon before the final moments of the merge.
Could she theoretically escape? Can you "jump" from one black hole to another? Let's look at the situation in terms of space-time.
Computer simulation of two merging black holes and the curvature of space-time caused by them. Although gravitational waves are emitted constantly, matter itself cannot escape.
When two black holes merge, they do so after a long period of spiraling, during which energy is emitted in the form of gravitational waves. Until the very final moments before the merger, the energy is emitted and flies away. But this cannot cause the event horizon or even the black hole to contract; instead, energy comes from space-time at the center of mass, which deforms more and more. With such success it would be possible to steal energy from the planet Mercury; it would rotate closer to the Sun, but its properties (or properties of the Sun) would not change in any way.
However, when the last moments of the merger arrive, the event horizons of the two black holes are deformed by the gravitational presence of each other. Fortunately, relativists have already numerically calculated how merging affects event horizons, and it's impressively informative.
Despite the fact that up to 5% of the total mass of black holes before merging can be emitted in the form of gravitational waves, the event horizon never contracts. The important thing is that if you take two black holes of equal mass, their event horizons will occupy a certain amount of space. When combined to create a double-mass black hole, the volume of space occupied by the horizon would be four times the original volume of the combined black holes. The mass of black holes is directly proportional to their radius, but the volume is proportional to the cube of the radius.
Although we have found many black holes, the radius of each event horizon is directly proportional to the mass of the hole, and this is always the case. Double the mass, double the radius, but the area will quadruple and the volume will quadruple.
It turns out that even if you keep the particle in the most motionless state inside the black hole and it falls as slowly as possible towards the singularity, there is no way for it to get out. The total volume of co-located event horizons increases during black hole mergers, and no matter what the trajectory of a particle crossing the event horizon is, it is doomed to be swallowed by the combined singularity of both black holes.
In many scenarios of astrophysics, ejections appear when matter escapes from an object during a cataclysm. But in the case of black holes merging, everything inside remains inside; most of what was outside is sucked in, and only a little of what was outside can escape. Falling into a black hole, you are doomed. And another black hole will not change the balance of power.
Ilya Khel