Are Larger Black Holes Less Dense Than Smaller Ones?

In summary: So a very small black hole has a very large event horizon. This is why black holes can have very low densities.
  • #1
Will Langas
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What has a higher density? Black Holes or Singularities?

I looked online and all I saw was that they both have infinite densities.
 
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  • #2
The density of a black hole would be computed as its mass over its volume - the volume within the event horizon. So that would be far from infinite.

A black hole with zero angular momentum should have an embedded singularity where almost all of the black hole's mass will be accumulated. I'm not sure if makes sense to talk about its volume at all, but if it has one perhaps it is zero. Of course, if it is zero, that would give it "infinite density".
 
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  • #3
I heard that a black hole can have a extremely low density. Also I heard that the bigger the black hole the lower the density. This does not make much sense to me, is it true? And if so can someone explain why?
 
  • #4
Hoophy said:
I heard that a black hole can have a extremely low density. Also I heard that the bigger the black hole the lower the density. This does not make much sense to me, is it true? And if so can someone explain why?
As I said in the previous post the "size of a black hole" is generally taken to be the diameter of its event horizon. The actual geometry of the black hole is pretty involved - but as a simplification, imagine that all of the mass of the black hole is concentrated in a singularity, a point, at the center. The size of the event horizon is the sphere around that point where light cannot escape. If you double the mass at the center, the distance to the event horizon increases so the total volume of the black hole increases. That total volume will more than double. So, heavier black holes are less dense because they can enclose more empty space.

Interestingly, it is the surface area of the black hole (the event horizon) that increases proportionately to the mass.
 
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1. What is the difference between a singularity and a black hole?

A singularity is a point in space where the laws of physics break down and become infinite, while a black hole is an object with a singularity at its center, surrounded by an event horizon that marks the point of no return for any matter or light that enters it. Essentially, a black hole is a region of space that contains a singularity.

2. Can a singularity exist without a black hole?

No, a singularity cannot exist without a black hole. Singularity refers to the point of infinite density and gravity at the center of a black hole, so the two are inherently linked.

3. What happens at the singularity of a black hole?

At the singularity, the laws of physics as we know them break down and become unpredictable. The gravitational pull is so strong that it warps space and time, and all matter is crushed into an infinitely small point.

4. Is the singularity of a black hole the same as the Big Bang singularity?

No, they are not the same. The Big Bang singularity refers to the initial point of the universe, while the singularity of a black hole is the result of a collapsed star.

5. Can the singularity of a black hole be observed or studied?

No, the singularity of a black hole cannot be observed or studied directly. The event horizon of a black hole prevents any information from escaping, so we can only study the effects of a black hole on its surroundings.

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