Saturday, September 21, 2019

gravity - what is the difference between a blackhole and a point particle


Theoretically, What is the difference between a black hole and a point particle of certain nonzero mass. Of-course the former exists while its not clear whether the later exists or not, but both have infinite density.



Answer



We should probably distinguish between a particle being "point-like" and a particle being "structure-less". In classical mechanics we talk of "point-like" particles, objects with no extension. It is the case that in general relativity any "point-like" mass would be inside of its event horizon and so would be a black hole.


In quantum-mechanics even a "structure-less" particle - a particle with no consitituent parts - is wave-like and has extension, though not a fixed size, and it can never be come exactly point-like since that would take an infinite amount of energy. I do not believe it to be the case, therefore, that quantum-mechanically all particles are black holes in any sense.


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