Separating Overlapping Event Horizons: Theory

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Discussion Overview

The discussion revolves around the theoretical implications of overlapping event horizons of black holes and whether it is possible to separate them into distinct event horizons through external forces. The scope includes theoretical physics and conceptual understanding of black hole dynamics.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions whether two black holes with slightly overlapping event horizons can theoretically be separated into two distinct event horizons with the application of extreme forces.
  • Another participant asserts that overlapping event horizons do not exist, as merging black holes result in a single event horizon.
  • A participant acknowledges that while merging leads to one event horizon, the singularities of the black holes remain separate and inquires about the theoretical possibility of applying external forces to separate these singularities.
  • Another participant challenges the notion of separate singularities, explaining that singularities are not spatial locations but rather instants in time, and emphasizes the need to conceptualize black holes in terms of spacetime.
  • It is reiterated that after merging, there is only one singularity, thus negating the possibility of separating singularities through external forces.

Areas of Agreement / Disagreement

Participants express disagreement regarding the existence of overlapping event horizons and the nature of singularities, with some asserting that merging results in a single event horizon and singularity, while others explore the theoretical implications of separation.

Contextual Notes

The discussion highlights the complexity of black hole physics, particularly in terms of spacetime concepts and the nature of singularities, which may not be fully resolved within the current exchanges.

anubodh
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If 2 black holes have event horizons slightly overlapping,can they ever be separated "theoretically" into 2 separate event horizons given we can apply extremely high forces to pull them apart or will it keep stretching and overlapping even if they are pulled apart?
 
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anubodh said:
If 2 black holes have event horizons slightly overlapping

This doesn't happen. What happens is the 2 black holes merge into one. When that happens there is only one event horizon, not two. There is no such thing as "overlapping event horizons".

anubodh said:
given we can apply extremely high forces to pull them apart

How would you "apply g forces" to a black hole?
 
@PeterDonis I get that after overlapping you get just 1 event horizon but the singularities inside are still separated.So,what i wanted to know was can we apply external forces in opposite directions so that these singularities start separating.I know it's practically not possible but i want to know whether it's theoretically possible or not.
 
anubodh said:
the singularities inside are still separated

No, they aren't. The singularities are not places in space; they are instants of time, which are to the future of all other instants inside the horizon. If two black holes merge, then there is only one singularity, not two, because there is only one "inside the horizon".

This is an area where you have to really train yourself to think in terms of spacetime, not space. A single black hole's horizon is not a 2-sphere; it's a 3-cylinder in spacetime, which you can imagine as a cylinder if you suppress one spatial dimension. The singularity is at the future endpoint of the interior of the cylinder.

When two black holes merge, in spacetime, there is really only one horizon, and always was--it's just shaped like a pair of trousers instead of a cylinder. The region where there are two "legs" of the trousers corresponds to the period of time before the holes merged, and the region where there is just one "trunk" of the trousers corresponds to the period of time after they merge. So there is only one "interior" and therefore only one singularity, at the future endpoint of the trunk of the trousers.

anubodh said:
can we apply external forces in opposite directions so that these singularities start separating.

No, because there is only one singularity. See above.
 
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