Does a black hole have infinite density?

Question

I'm confused. Some people say that black holes have infinite density, but wikipedia says that a supermassive black hole is 10^36KG. HELP!

Answer 1

In theory, black holes DO have infinite density. But they do not have infinite MASS. Mass is measured in kilograms, so that 10^36KG number is a mass and not a density. Density is mass divided by volume. In theory, a black hole has ZERO volume, so the DENSITY for your 10^36KG black hole is 10^36KG / 0, which is infinity.

Now the size of the black hole should not be confused with the size of the event horizon. The event horizon is the size of the area where the escape velocity is higher than the speed of light. But the black hole itself is the actual mass in the middle of that volume, and that mass, in theory, is crushed by its own gravity all the way down to a mathematical point, with no size at all. In mathematics, it is called a singularity. It is where all the math breaks down and none of the rules work. The rules of math do not allow you to divide by zero, but that is exactly what you would have to do to get the density, or even the gravitational acceleration at the surface of a black hole.

Answer 2

Its average density is certainly not infinite. You have to define what you mean by the extent of the black hole, but if you take the event horizon, this can be very, very large for massive black holes.

However, at the heart of the black hole there is a singularity where spacetime curves infinitely. The volums of this is zero, so any mass it happens to contain is at infinite density.

Answer 3

A singularity, the heart of a black hole, is defined as a point in space with infinite density and zero volume. It's a theoretical value that is obtained mathematically. We have no way of actually knowing what is in a black hole.

Answer 4

Mathematically, a black hole's density is infinite, because at its heart is a point in spacetime that is infinitely compressed. This point also has no size. No one really understands what this really means, however, because it is clear that some black holes are much more massive than others. The discrepancy is a result of our incomplete understanding of that realm where general relativity and quantum mechanics overlap. Essentially, the statements "Black holes are infinitely dense." and "A black hole has a mass of x." are both true, even though they seem mutually exclusive.

Answer 5

The black hole itself is a singularity, which effectively has zero volume and therefore infinite density even if its mass is finite.

And 10^36kg is, for most intents and purposes, infinite mass.

Answer 6

You have confused mass with density. Density is the amount of mass within a volume. Mathematically this is expressed as:

Density = mass / volume

As volume decrease, and mass increases, the density increases. Black holes have an infinite density because their volume is zero.