Two Black Holes' collision thought experiment

In summary, according to the black hole has no hair theorem, any result to a BH collision is only based on their mass, charge, and angular momentum (assuming GR). Whether one formed from antimatter is wholly irrelevant. So your final answer is correct, for a more fundamental reason. As to what happens inside, it obviously depends on how much you trust GR in the interior.
  • #1
28
1
Once, someone had asked two interesting (though absolutely hypothetical) questions:

1) What should happen during the collision of two BHs, one consisting of matter (BH+) and the other consisting of antimatter (BH-)? Should they form a larger BH or should they be annihilated?


My personal opinion is that -probably- the EH of the new BH is formed before the singularities (of the original BHs) will meet each other. So, as the mass of a BH is concentrated on its center (i.e. on its singularity), the annihilation of their masses will take place after the formation of the new EH (and the vast amount of photons that will be produced from the annihilation will never manage to escape). As a 2nd thought, we cannot really know what will happen when the two singularities will meet each other, as we don't know the "form" of the mass on a singularity or even the laws of Physics that govern it. What's your opinion?

2) Suppose that there are two neutron stars (NS), one consisting of matter (NS+) and the other consisting of antimatter (NS-), and each of them having a mass somewhat lower than the critical mass for the formation of a BH. What should happen during their collision? Should they form a BH or should they be annihilated?

My personal opinion is that -probably- there will be an annihilation right on the contact point and this will lead to the gradual annihilation of the whole mass of the two objects before an EH has the chance to be formed. What's your opinion?
 
Astronomy news on Phys.org
  • #2
Your guesses seem reasonable, but as you point out they are only guesses. The neutron star description is well within theory, but the black situation is fairly speculative, since the inside of a black hole is unknown physics (quantum theory meets general relativity).
 
  • #3
1) Per the black hole has no hair theorem, any result to a BH collision is only based on their mass, charge, and angular momentum (assuming GR). Whether one formed from antimatter is wholly irrelevant. So your final answer is correct, for a more fundamental reason. As to what happens inside, it obviously depends on how much you trust GR in the interior. If you do, then for 'old' BH, there is only vacuum on the inside with a singularity, so no interaction to occur. For new BHs, where not all matter has collapsed, your suggestion of annihilation with everything continuing to collapse anyway, is what would be expected.

2) It all depends. For example, if the neutron and anti-neutron star were approaching each other at exceeding close to the speed of light, their combined COM energy could be large enough that they are inside their SC radius before they are touching (note: total energy/c2 is the M to use for computing the combined SC radius). Then, if the hoop conjecture is true, they would inevitably form a BH. A minimum energy collision would be difficult to compute. I don't think they could possibly meed the criteria of the hoop conjecture, so detailed dynamics would have to be modeled. I wouldn't even venture a guess as to the outcome.
 
Last edited:

1. What is the Two Black Holes' collision thought experiment?

The Two Black Holes' collision thought experiment is a theoretical scenario in which two black holes of equal mass are on a collision course towards each other. It is used to study the behavior and consequences of such an event in the context of Einstein's theory of general relativity.

2. Why is the Two Black Holes' collision thought experiment important?

This thought experiment allows scientists to better understand the physics of black holes and how they interact with each other. It also provides insights into the nature of gravity and the predictions of general relativity in extreme conditions.

3. How is the Two Black Holes' collision thought experiment conducted?

The thought experiment is conducted through computer simulations that use complex mathematical equations and models to simulate the behavior of black holes in a collision. These simulations help scientists make predictions and observations about the event.

4. What happens when two black holes collide?

When two black holes collide, they merge together to form a single, larger black hole. This process releases a tremendous amount of energy in the form of gravitational waves, which can be detected by specialized instruments on Earth.

5. What can we learn from the Two Black Holes' collision thought experiment?

The thought experiment can provide insights into the behavior of matter and energy in extremely strong gravitational fields, as well as the properties of black holes such as their mass, spin, and event horizon. It can also help us understand the formation and evolution of galaxies and the universe as a whole.

Suggested for: Two Black Holes' collision thought experiment

2
Replies
63
Views
2K
Replies
11
Views
1K
Replies
23
Views
1K
Replies
12
Views
1K
Replies
2
Views
838
Replies
5
Views
1K
Replies
13
Views
1K
Replies
3
Views
827
Back
Top