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

In summary, the experts in this conversation discuss the concept of infinite density in relation to black holes. They explain that while a black hole has a relatively fixed mass, its gravitational potential is not infinite. The event horizon is determined by the escape velocity, and even objects like Earth would have an event horizon if compressed small enough. The experts also discuss the possibility of infinite density being limited by quantum gravity and the uncertainty principle.
  • #1
benzun_1999
260
0
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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  • #2
Certainly does. And the yes, the spacetime inside a black hole is said to have infinite curvature and matter squeezed into infinite density.
 
  • #3
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.
 
  • #4
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
 
  • #5
I still vote for the Planck density as the upper limit.
 
  • #6
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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  • #7
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:)
 
  • #8
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.
 
  • #9
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.
 

1. What is a black hole's event horizon?

The event horizon of a black hole is the point of no return, where the gravitational pull is so strong that even light cannot escape. It marks the boundary of the black hole, beyond which nothing, including matter and information, can escape.

2. Does a black hole's event horizon increase with mass?

Yes, the event horizon of a black hole is directly proportional to its mass. As the mass of a black hole increases, its event horizon also increases in size.

3. How does the size of a black hole's event horizon affect its gravitational pull?

The size of the event horizon is directly related to the strength of a black hole's gravitational pull. The larger the event horizon, the stronger the gravitational pull will be. This is because the event horizon is the point at which the escape velocity exceeds the speed of light, making it impossible for anything to escape the black hole's gravitational pull.

4. Can a black hole's event horizon shrink or expand?

No, a black hole's event horizon cannot shrink or expand. It is a fixed boundary that marks the point of no return for anything that gets too close to the black hole's center of mass.

5. How is the event horizon of a black hole calculated?

The event horizon of a black hole can be calculated using a formula known as the Schwarzschild radius, which takes into account the mass of the black hole and the speed of light. The formula is 2GM/c^2, where G is the gravitational constant, M is the mass of the black hole, and c is the speed of light. This calculation gives the radius of the event horizon, beyond which the black hole's gravitational pull is too strong for anything to escape.

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