# Destroying A Black Hole

1. Jan 30, 2013

### Staff: Mentor

So we know that Alice can free fall through the event horizon of a black hole and not notice anything. Yet Passing the event horizon is a one way event; no thing and no information can ever exit. (Except Hawking radiation).

As a thought experiment, suppose we bombard the black hole with antimatter thus annihilating the mass? Could that make the black hole white again? At the very least could it make the radius of the event horizon decrease putting Alice outside the horizon once again?

There could be a couple of flaws.

The radiation produced by annihilation might gravitate as much as the mass did. Then the radius of the event horizon would increase.

It could also be true that a particle falling into a black hole can never catch up with another particle that fell in earlier. In that case the antimatter would never meet the matter. No annihilation would occur and the radius of the event horizon would increase.

2. Jan 30, 2013

### PAllen

Antimatter has positive mass energy, just like matter. You would just increase the size of the BH.

Note, it is possible for a later infaller to catch an earlier infaller, depending on their trajectories outside the horizon. For example, suppose earlier infaller was resisting infall a meter from the horizon until they ran out of fuel. Suppose a later, suicidal infaller was firing thrust at their maximum speeding up their approach, up through and past the horizon. If the suicidal infaller isn't too much behind the unwilling infaller, they will catch up.

3. Jan 31, 2013

### Sayajin

The only thing that could destroy black hole is something with negative mass which has never been observed(all the things we know have positive mass). The BH sucks up everything. No matter what you put whenever something passes the event horizon there is no way back.
And the other thing is that you can't describe the black hole like compilation of particles.
The event horizon is just part of spacetime. And the real matter that came into the black hole is contained in the singularity. At that point ordinary particles can't exist. There is not even clear definition of what spacetime is at this scale.