What is the size of the black hole?

In normal cases, when we discuss the size of a black hole we say that the black hole's size is the Schwarzschild-radius. That is the distance of the event horizon, and that is the point where escaping velocity turns faster than light. That means the black hole is an extremely dense gravitational field that surrounds the extremely dense object. 

The mass of the object that forms the black hole can be normal. But its density is so high that it can form an extremely dense gravitational field. So that means that every single object in the universe can turn into a black hole if it gets enough energy. When a particle or object turns into a black hole all its quantum states will turn into one. 

So the black hole doesn't destroy information or material. It just connects them to one entirety. So that means quantum states of material are unified into one entirety called a singularity. Sometimes that term is used also meaning the area inside the event horizon. But it means the state of material where all subatomic particles and quantum fields are connected as an extremely small and dense entirety. 

The event horizon is the extremely high-energy area around the black hole. At that point, the escaping velocity turns the same as the speed of light. And in that point photons are orbiting the center of a black hole. The event horizon has stages. The most out stage is the point, where ions are orbiting the black hole. Then the electrons and finally photons are orbiting that monster. When electrons are orbiting the event horizon, they are transmitting energy out from the black hole. 

Or actually, photons are the first particles that store gravitational energy, and then they impact those electrons. When kinetic energy is stored in a particle. It must get it from somewhere. In black holes, the thing that forms the energy is the gravitational field. 

The energy is not forming from emptiness. The particles that are orbiting black holes are transforming gravitational energy to another form.  The process is similar to the cases, where the hydro plant's turbine transforms the water flow that travels through it into kinetic energy. And then the generator turns kinetic energy into electricity. Near the black hole energy that impacts the particles increases their energy. 

So the particles near black holes are also transmitting energy outside. But does that energy come in or out of the black hole? When a transition disk around a black hole orbits it, there is friction between those particles, but that material disk also captures energy from interstellar space. When those particles hit electrons and photons. That increases the energy level in the transition disk. And that is the thing that feeds black holes. And as you might see the interactions around the black hole and its transition disk are quite complicated. 

During that process, electrons behave like always. They are curving closer to the event horizon. And when they jump back they send photons. But the event horizon itself is the place, where the photon cloud orbits the extremely strong gravitational field. And at that point, everything disappears in the black hole. So the information that falls into the black hole remains. But there is no way to reach it. The photon is the last particle that can escape from the black hole. 

One of the reasons why nobody and nothing can escape from inside the event horizon is that the energy travels into the center of the black hole. And the thing is the reason, why physicists believe in the existence of wormholes and white holes. When something falls into a black hole it increases its mass and energy level. That means the black hole should expand forever. But somehow black holes seem to lose their mass. That means something still escape from those monsters. Another interesting thing is the gravitational waves that black holes are sending. 

There is the possibility, that those gravitational wave's sources are the extremely small black holes or so-called parasite black holes that are orbiting larger black holes. In that model, the black holes form a large group of atom-size black holes around them. The gravitational fields of those small black holes can stretch the event horizon outwards. 

And there is a possibility that just in the middle of those small black holes. The gravitational field is stronger than just below the larger black hole's event horizon. So the parasite black hole steals material and energy from the larger black holes. And when they impact the event horizon of the larger black holes they send gamma rays. 

Because part of the energy that is released in that reaction is stored in the smaller black hole it transfers that energy out from the larger black hole. The idea is that when energy is transferred to the smaller black hole before it impacts the larger black hole, that smaller black hole can conduct energy out from the larger black hole. 

The idea is similar to putting water from a large tank into a drinking glass. If we drop that glass it just takes water out of the tank. And sooner or later the large tank will turn empty. 

https://skyandtelescope.org/astronomy-resources/how-big-is-a-black-hole/

https://bigthink.com/starts-with-a-bang/black-hole-actual-size/

https://en.wikipedia.org/wiki/Schwarzschild_radius