Welcome to How to destroy a black hole for dummies
So, are you looking for a way to eliminate the right black hole, arent' you? Well, you're reading the right guide. But before beginning, it could be useful to make some clarifications on the nature of these galactic monsters. As Sun Tzu says, to defeat your enemy, you must first know him. Let's know what a black hole is.
1) Why black holes are a so formidable opponent?
Black holes are the natural enemies of all spacefaring races. With their bottomless capacity to consume all light and matter, it’s just a few septillion years before all things in the Universe have found their way into the cavernous maw of a black hole, crushed into the infinitely dense singularity. For a black hole, any matter entering the event horizon is added to the mass. Shoot bullets at a black hole, and you just make a slightly more massive, slightly more dangerous black hole. Detonate a nuclear bomb inside the event horizon, and you only make the black hole more massive. Fire your forward phasers at the black hole, and that’ll still make it even more massive. Swap those bullets in for lasers and black holes don’t care. Within the event horizon, energy and matter are one, and those very same black holes can convert that energy into mass. So all your projectiles and energy weapons inevitably just make it more dangerous.
So the problem is that any material is introduced into a black hole (whatever is physical matter or energy) will be swallowed up and will contribute to the growth of the enemy.
What if I use an anti-matter weapon? Maybe throwing an antimatter black hole into a black hole? We'll have a nice KABOOM, and problem solved
Nice try Jimmy. The problem is that even if you manage to create and stabilize an anti-matter black hole (and it is doubly impossible, because first you have to find a way to contain antimatter, and then you have to find a way to contain an antimatter...black hole), throwing it at a black hole will surely create a huuuge explosion, but all the energy will be converted and processed by the black hole. The bottom line is: if a regular black hole and an antimatter black hole got black-hole-married in space, they wouldn’t vanish.
2) Solutions
So, what are the possibile solutions to destroy a black hole? The answer, surprisingly, lies in the enemy's very features. We must take advantage of the enemy's ability and twist them against it.
Wait
Yess...just wait. I know, it's the most boring one, but at least it's a solution. According to Stephen Hawking, black holes can actually evaporate over enormous periods of time. So, over an incomprehensible period of time, even the most supermassive of the black holes will have evaporated away into a harmless soup of particles. It turns out, in order to defeat the black hole menace, all we need to do is ignore them, and they’ll go away all on their own. But, if you asked how to destroy a black hole, I suppose you need it now. So, next solution is to...
Get rid of event horizon
Getting rid the events get two interesting results; first of all, you get what you want: you killed a black hole. In addition, once removed the horizon, you will have access to real black hole, and all its secrets. The problem is this solution is a bit complicated.
In general relativity, the mathematical condition for the existence of a black hole with an event horizon is simple. It is given by the following inequality: $$ M^2 > \left(\frac{J}{M}\right)^2 + Q^2 $$ where $M$ is the mass of the black hole, $J$ is its angular momentum and $Q$ is its charge.
Getting rid of the event horizon is simply a question of increasing the angular momentum and/or charge of this object until the inequality is reversed. When that happens the event horizon disappears and the exotic object beneath emerges.
But that hides a multitude of problems. For a start, things with angular momentum and charge also tend to have mass. And in any case, the equation above describes a steady state. Feeding a black hole creates a dynamic state and there is no guarantee that the object will settle back into a steady state again without shedding the angular momentum and charge that it has been fed.
In fact, the calculations are so fiendish that they have defied all attempts to tame them.
Use time travel device
Remember when we said that blacks holes in time dissolve? Sure, it takes eons, but what if you could speed up the time? Creates a kind of space-time bubble, and speeds up the time. The black hole will dissolve as expected, or perhaps even more quickly, failing its nourishment.
atoms, molecules, DNA, cellular organisms, multicellular organisms, buildings, streets, cities, countries, continents, planets, and even stars.
Heck, we might have the tools to destroy all of these... worldbuilding.stackexchange.com/questions/36103/… $\endgroup$