What is the size of a black hole?

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SUMMARY

The size of a black hole is a complex topic that intertwines general relativity and string theory. While general relativity suggests a singularity at the center of a black hole, many string theories propose that the black hole's center may be compressed to the Planck scale, approximately 1.6 x 10^-35 meters, rather than being a true singularity. The discussion emphasizes that the term 'singularity' indicates a lack of understanding in current mathematical frameworks, and it is widely accepted that the matter within the event horizon is smaller than the event horizon itself. A definitive answer remains elusive, necessitating advancements in quantum gravity theories.

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  • Understanding of general relativity and its implications on black hole physics
  • Familiarity with string theory concepts and the Planck scale
  • Knowledge of quantum gravity theories and their significance in modern physics
  • Basic comprehension of the structure of black holes, including event horizons and singularities
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  • Research the implications of Planck length in theoretical physics
  • Study the differences between general relativity and string theory regarding black holes
  • Explore current theories of quantum gravity and their potential to resolve black hole singularities
  • Investigate the mathematical frameworks that describe singularities and their limitations
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Astronomers, physicists, and students interested in advanced concepts of black hole physics, particularly those exploring the intersection of general relativity and quantum mechanics.

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If Planck length is the smallest size, does that mean a black hole would get compressed down to the Planck scale, but no further or can the black hole really have zero size like an electron?
 
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According to many string theories, the Planck size is the limit---and thus a BH's center would indeed be about that size, and not a true singularity (as general relativity suggests). The answer is unknown.

Side-notes:
1) Black-hole refers to the entire object, specifically the event horizon---not just the central singularity
2) Electrons have a finite (non-zero) size.
 
The term 'singularity' is math speak for 'we don't know'. It is the point where our math ceases to yield intelligible results. We know the chunk of matter hiding behind an event horizon is smaller than the event horizon [duh]. A good guess would be some multiple of Planck lengths, but, that is still just a guess. We probably need a theory of quantum gravity to get the right answer.
 

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