Does a Black Hole's Event Horizon Increase with Mass?

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Discussion Overview

The discussion revolves around the relationship between a black hole's mass and its event horizon, specifically whether the event horizon increases as mass is added. Participants also explore concepts of density within black holes, including the idea of infinite density and its implications for gravitational potential and the nature of singularities.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that as a black hole gains mass, its event horizon increases, while others discuss the implications of infinite density and gravitational potential.
  • One participant asserts that the core of a black hole is infinitely small and dense, but acknowledges that mass is not infinite.
  • Another participant questions the concept of infinite density, suggesting that there may be a maximum density limit, such as the Planck density.
  • Some argue that gravitational potential is not infinite and that black holes behave similarly to other celestial objects in terms of gravitational effects.
  • There is a discussion about the role of quantum gravity and the uncertainty principle in understanding black hole singularities and density limits.
  • Participants express uncertainty about the nature of singularities and the forces that might prevent collapse to zero volume.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the nature of density within black holes or the implications of infinite density. Multiple competing views remain regarding the existence of maximum density and the behavior of gravitational forces at singularities.

Contextual Notes

Limitations include the lack of a comprehensive theory of quantum gravity, which leaves questions about the behavior of matter and forces inside black holes unresolved.

benzun_1999
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hi,
i was just wondering as the mass of the black hole keeps increasing due to increased mass getting deposited on it does its event horizon increase
because of this?

does the black hole have infinite density?

-Benzun
 
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Certainly does. And the yes, the spacetime inside a black hole is said to have infinite curvature and matter squeezed into infinite density.
 
The "core" of a black hole is infinitely small and infinitely dense. But it does have a relatively "fixed" mass, that is to say that the mass is not infinite one way or the other, such as the volume or density.
 
if infinite density exists won't its gravitationl potential be also infinite. So its evvent horizon would cover the entire space time.

i could be wrong. i am just learning so please help me.

-benzun
 
I still vote for the Planck density as the upper limit.
 
benzun_1999 said:
if infinite density exists won't its gravitationl potential be also infinite. So its evvent horizon would cover the entire space time.
i could be wrong. i am just learning so please help me.
-benzun

No, its gravitational potential is not infinite. A black hole is no different to any other celestial object one encounters in space. If a black hole has a mass of 15 solar masses, then objects gravitate around the black hole in the same manner as if they were orbiting a 15 solar mass star.

The second part about its event horizon, is all to do with escape velocity. Earth has an escape velocity of 11 kilometers a second, a black hole has an escape velocity of 300,000 kilometers a second which is also the speed of light, hence light cannot escape. Everything has an event horizon if it is compressed small enough, even the Earth has one if we were to shrink it into about the size of an atom.

Correction, the Earth would have a Schwarzschild radius of half a centimeter. (That’s the distance from the singularity in the center to its event horizon)
 
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so i believe i am correct in telling that infinite density is not possible. there is a maximum density for anything in spacetime. i am kind of working on a theory like this. i don't know how to procced i will be really happy if anyone helps me. if interested pls pm me.o:)
 
benzun_1999 said:
so i believe i am correct in telling that infinite density is not possible. there is a maximum density for anything in spacetime.

Well until we have a theory of quantum gravity, we aren’t really sure what happens inside a black hole, especially at the singularity. There’s nothing (AFAIK) in relativity to say infinite density is impossible. So if the Planck conditions are reached inside a black hole, it will be limited by quantum gravity to about 10^94 grams per cubic centimeter.
 
If the idea of infinite density, or alternatively a finite mass body collapsing down to a singularity of zero volume, seems impossible and unphysical, then ask: "What is it that prevents ordinary objects from not having zero volume? What gives objects in the physical world its geometrical structure?"

The answer is of course the strong nuclear and electro-weak forces. What happens then when the gravitational force inside an event horizon overcomes all other possible forces? What is it that prevents such a collapsing object from not collapsing to zero volume and infinite density?

Other forces stronger still will be required, so far we do not have the physics to deliver such strong replusive forces, yet.

Garth
 
  • #10
I would vote for the uncertainty principle. It insists all entities occupy a finite, albeit incredibly tiny volume - which works out to be the Planck density.
 

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