How can a black hole have measurable mass if it is supposed to be an infinite singularity?

Question

First they talk about the singularity, then they say some black holes are more massive than others. If it all falls into a singularity, how can the mass be different?

Answer 1

The "singularity" is a mathematical point at the centre of a given mass (the mass of the black hole) but with zero volume.
The more massive the black hole, the same zero-volume singularity, but the larger the event horizon for the black hole (the distance from the singularity where the escape velocity is equal to the speed of light).

Answer 2

A singularity has a volume of 0. Any non-zero mass crunched down to a volume of zero will have infinite density (however, its mass is still finite).

Take a finite mass. That mass has a Schwarzchild radius. If the entire mass somehow finds itself inside this radius, then the outside world simply interprets it as a black hole. It still has the same mass (the mass does not increase simply because it went inside the event horizon).

However, we know of no mechanism that can hold up the mass against its own gravity once it has passed inside the event horizon. Plus, we figure that space and time behave differently inside. Therefore, everything behaves AS IF all the mass were in a singularity.

If dealing with a black hole, always treat your equations as if the mass was a singularity. Somehow, it always works.

Is it really ALWAYS a singularity? We had very "excited" discussions during my latest course.

Answer 3

I guess your real question is how a mathematical point can have mass. Since a mathematical point is nothing, so how could different ones have different masses? Shouldn't they all be zero mass?

Maybe I can suggest that the actual star is not a mathematical point in reality, What is probably going on is that the star is shrinking forever, going towards a singularity, but not getting there. Remember that time and space are severely distorted in this case. I suppose that time is incredibly slowing down in this process, just as when a massive object is reaching the speed of light.

Any comments on this?

Answer 4

You have the concept mixed up a bit. All the black holes we know of do not have infinite mass. The most massive that sit at the center of galaxies range from millions to billions of stars. For mathematical purposes they are described as singularities but no one really knows if one would appear as a sphere or something else.

Answer 5

The one that fall into singularity is their density, their density of a black hole will become closer to infinity over time, and the volume will become closer to zero. This is kind of zero multiplied by infinity class of limit problem, we learned in high school.
But the mass can still be calculated from its gravitational effect. Just remember that there are a lot of other methods to measure mass instead of density x volume formula.

Answer 6

countless Mass? No there's a finite mass to a 'Black hollow' countless Density? possibly, if all that mass is truthfully concentrated at a a single factor. considering there is an 'journey horizon' around the singularity, this might nicely be a remember of conjecture.

Answer 7

I believe that black holes have diameters regardless of the singularity that may exist at their centres, in my opinion the event horizon of a black hole hugs the surface of the black hole, it is beyond me to imagine an event horizon surrounding a point that has no volume.

Answer 8

How can an object have an infinite mass?
Nothing can have an infinate mass.. even objects without mass such as singularities inside blackholes seem skeptical to me..
Can someone explain this to me a little better?

Answer 9

Black Holes, like ALL things described by science, have some degree of theory in their definition and description. At one time their very existance was merely theoretical.

How can an enity that eats matter and creates anti matter be measured in terms of mass? Well put enough heads together and you are bound to get a handful of theories. One may be convincing enough to get published in a text book.....until a better one comes along and replaces it a few years down the line.

Answer 10

The mass can be easily calculated by measuring the gravitational field strength. How that matter is arranged cannot be known since we cannot get any data from within the event horizon.