Is a black hole's density what drives it's gravity?

Question

Is the density of a black hole what's responsible for it's gravity and pull?

Answer 1

No, it is the mass that is reponsible for its pull.
All black holes have infinite density, but they do not all have the same mass. Neither do they all have the same amount of attraction (gravity).
I'll try to demonstrate. Let's say there is a black hole with a mass the equivalent of 10 suns. Not a particularly massive black hole. However, this black hole would have infinite density, because all black holes have zero volume.
Density = mass / volume. If dividing by zero, the answer is infinity. Therfore, all black holes have infinite density.
Now look at a supermassive black hole. It may have the mass of 1,000,000 suns. It would have much more attraction (gravity) than the first black hole. But it would have the same density. Zero.
Nevertheless, the infinite density does contribute to a black hole's incredible pull. I'm just saying it is not the only factor.
edit: you are right about the Swartzchild radius but that is not truly the volume of a black hole. The black hole itself has no volume, but anything within the Swartzchild radius is invisible as light won't escape from there. The greater the mass of the singularity, the larger volume within the shwartzchild radius. (not sure about spelling on that sorry.)

Answer 2

I'm not sure it makes sense to talk of the density or volume of a black hole. it's not possible for a signal to originate within the a certain (Schwartzchild?) radius and escape ... so its not meaningful to talk about any size or shape inside that region .. you simply can't know.

what drives its gravity is its mass, and its gravity causes the catastrophic compression, so the "density" (which must be at least be as great as mass / 4/3pi S^3 ) is a sympton rather than a cause

Answer 3

There's no such thing as density for a black hole. Density implies volume and a black hole is thought to be a singularity which implies no volume. The mass is what drives the gravity.

Answer 4

Actually........

It's the Black Holes (or any other objects) Mass that is directly related to it's gravitational pull. Volume and density have no real bearing on the situation.

Let me put it to you this way Two objects of the same MASS will have the same gravitational pull. Even if one is densly packed into the volume of the Earth and one is less dense and has twice the volume.

Answer 5

It's mass is responsible for it's gravity. That's a little different than saying it's density is. It's density is what allows it to have an event horizon.

Answer 6

Yes.

Picture the universe as one gigantic rubber sheet. Normally the universe is flat, and there is no gravity.

Now put a bowling ball on the sheet. It sags. The bowling ball represents the black hole, and gravity is represented by the amount of the sag - the more mass present, the higher the localized gravity. You can represent smaller masses with different size balls - golf, baseball, softball, etc.

The sheet represents what's known as "the fabric of space-time". The distortions in this fabric (the ones caused by masses) are what's known as 'gravity wells'.

Hope this helps.

Answer 7

You can make mini holes by making things dense. You could take a can of beans and squash it so much it makes a black hole.

There is a singularity inside a black hole, as nature abhours a 'naked singularity' we have something called the 'even horizon', beyond which nothing can escape.

Answer 8

Yes the super matter is extremely dense which allows for a large mass in a small volume and given the large volume and immense density of a blackhole, it has a lot of gravitational force.
GF = G*M1*M2/r^2
so as we increase M1(blackhole) mass the GF increases.

Answer 9

yeah thats what they say

gravity so strong that even light can't escape

Answer 10

yea