## What happens when two black hole singularities meet - by Gulshan Kumar Jha - Quora Question Review

This document contains a review of the answer by by Gulshan Kumar Jha on the question in Quora: "What happens when two black hole singularities meet"
• The text in italics is copied from the article.
• Immediate followed by some comments

### Reflection

What actually happens?

As the black holes get closer, they emit gravitational waves, which are ripples in spacetime

The concept spacetime requires a clear definition. IMO its is not a physical concept but a mathematical. This implies that spacetime does not exist, and are space and time two different concept. Space is a physical concept. Important is that space can be considered as empty and as not not empty.

These gravitational waves carry away energy and angular momentum, causing the black holes to spiral closer and closer together.

This is the same subject as discussed in Reflection 1 - Question Review
My simulations show different results.
If you take two objects, in empty space, this is a binary system and using Newton's Law, the result will be a stable system. This simulation is independent of the (point) mass of the objects.
If you include a third object different results are possible, depending about the initial conditions.
The results also depends about the (relatif) size of the third object.
Different results are, assuming the third object approaches the pair from a large distance:
• The third object will be ejected.
• The third object merge with one BH of the pair.
• This collision will be heavy, and influence the path of the second BH of the pair and both also will collide.

When the both black hole starts merging, their event horizons merge as well, and a single, larger event horizon is formed around the resulting a big black hole, bigger than the previous one (The supermassive black holes). The central singularities also merge in some way, but the exact nature of this process is not well understood due to the limitations of our current understanding of the fundamental physics at play near singularities

The Concept of horizons is not important in understanding what is happening. Anyway a horizon is not a physical concept.
The concept of singularity is also not important in understanding what is happening.
What is important the amount of matter of the combined object, because a certain amount of matter can be ejected in space, outside the gravitational influence of the remaining object.

The process of merging of the two black holes approaching each other is known as black hole binary inspiral and merger.

It's important to note that our understanding of what happens near black hole singularities is based on theoretical models and calculations that rely on general relativity.

It should be mentioned that a simulation of a BH using general relativity is very difficult because the parameters involved should be tuned based on real observations. With two BH"s it is even more difficult.

### Reflection 1 - Question Review

The question: "What happens when two black hole singularities meet" is wrong. First a black hole is not a singularity but a physical object identical as all objects in the universe, except that its size is very small compared to its mass, which is large.
To understand this sententence requires a clear definition of: singularity, size, and mass.
A singularity is a mathematical concept and not a physical concept.
A singularity is the result of a mathematical calculation when you divide a positif number by zero. The result is infinity.

Second how do we know that two black holes will meet each other? It is important to change this question slightly as: How do we know that two BH's meet in an else empty universe? This "else" is important.
What makes two small Blackholes different compared with two large stars of the same mass? (In an else empty universe)

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Created: 1 June 2023

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