# B How to annihilate black holes?

Tags:
1. Dec 5, 2018

### Tree Universe

Hi Everyone,

I'm interested in how to annihilate black holes (they are like blenders separating all the things apart and agglomerate like "tumors/cancers" in the universe). However, I'm new to this field and need some clarifications on some of the basic concepts like "annihilation" and "negative energy".

The first assumption is that black holes have three main characteristics: 1) mass/energy, 2) the angular momentum, 3) electric charge.

The second assumption is that Hawking Radiation (Black Hole Evaporation) exists that virtual particles are separated to real particle-antiparticle pairs at the event horizon (or wall of a black hole), then the antiparticle is trapped (which causes the mass of the BH to increase) and the particle is ejected (which causes the Hawking Radiation) - so the BH continues to use antiparticle to annihilate particles or matters outside itself. The annihilation leads to massive energy which in turn increases the angular momentum of the BH, which increases the gravitational well of the BH (electrical antimatter is its medium) and further increases the area of the event horizon and accelerates the annihilation speed. The worst scenario is that a BH will grow ever bigger.

Does anyone know any observation studies published showing that any BH is shrinking?

I assume that If the BH is small enough, the antiparticles will be used out - since there are plenty of matter outside with the opposite angular momentum and the opposite electrical charge and the speed of its annihilation rate is less than the speed of matter it encounters and traps. If the BH is large, the annihilation rate by the BH will be greater than the speed of the matters it encounters and traps while the separation of virtual particles still going on. So the BH would be a black sphere filled with antiparticles/antimatter, located at the center of the event horizon.

I also want to conjecture an optimal method to counteract the growing of a BH by sending a very strong beam of matter charged with the opposite electricity and with the opposite angular momentum to the center of the BH. I want to know what you fellows think about this - is this contradictory to any existing physics law?

I am also confused about the concept of "annihilation". Does it mean particle and antiparticle meet and transform into pure energy, or they meet and transform into energy and other particles? And what does "negative energy" mean?

Thank you!

2. Dec 6, 2018

### Staff: Mentor

The explanation of Hawking radiation in terms of virtual particle/antiparticle pairs is very misleading. It may be an OK math-free explanation for laypeople, but it leaves so much out that you can't use it as a base for new ideas or a deeper understanding. (If you are interested in seeing what the real thing looks like, you can read Hawking's paper here).
But in any case, you have it backwards here. Hawking radiation causes a decrease in the mass of the black hole and the area of the event horizon.
There are no such observations because the rate of energy loss through Hawking radiation is inversely proportional to the size of the black hole and all known black holes are large enough that they lose less energy from Hawking radiation than they gain from the cosmic microwave back ground. It will be a very long time before the universe has expanded and cooled enough that these black holes are expected to start losing energy and shrinking.
No, doesn't work. Dumping anything into a black hole, whether matter or antimatter, charged or not, increases the mass and size of the black hole.

Anytime that two particles meet, the interaction may produce other particles and release energy. The word "annihilation" is generally used for the special case in which only energy is released, no particles come out of the interaction, and these interaction are generally between a particle and its antiparticle.

For negative energy, you could give http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/hawking.html a try.

3. Dec 6, 2018

### Staff: Mentor

There is no such process. Where would the energy be without particles? You might get photons out of it, but baryons meeting antibaryons are also considered annihilations, and the reactions typically produce a couple of pions.
You can reduce the electric charge (which is negligible anyway for realistic black holes) and the spin, but doing so increases the mass of the black hole.

4. Dec 6, 2018

### m4r35n357

Are you serious?

5. Dec 6, 2018

### Tree Universe

Thank you all for clarifying some concepts, answering my questions, and directing to other readings!

There are some analog researches on simulating black hole mechanism using acoustic/sonic methods and superfluids or Bose–Einstein condensate (with the temperature very close to absolute zero) - these are a great start and progress on how to counteract black holes!

@Nugatory I'm still a bit confused about "negative energy", does the "negative frequency solutions (depending on the sign of ω) of Maxwell's equations" in the linked article stand for "negative energy"?

@m4r35n357 Yes, maybe someday when we have capability, we need to vanish black holes just like what we do on tumors to prevent small black holes from growing big or totally clean big ones. That could be meaningful for the universe.

Hope to discuss with you more!

6. Dec 6, 2018

### Staff: Mentor

You still have it backwards - because Hawking radiation is inversely proportional to the mass, small black holes do not grow (as long as we don't drop anything into them), they shrink all by themselves. In fact, there is much doubt as to whether such small back holes even exist - no known or imagined physical process can create one today, and any created by the more intense conditions shortly after the big bang (also a speculative idea) will have evaporated long ago.

A stellar mass or larger black hole is no more dangerous or likely to need cleaning than a star of comparable mass.

7. Dec 6, 2018

### Staff: Mentor

No.
No. Black holes are not dangerous unless you get very close and they won't grow unless you throw in additional mass. In the very distant future they will shrink.