We don't know for sure that black holes are singularities. In fact, there is some evidence that suggests they may not be. However, the theory of general relativity predicts that black holes should be singularities.

The theory of general relativity is a theory of gravity that was developed by Albert Einstein in the early 20th century. It is based on the idea that gravity is not a force, but rather a curvature of spacetime. The more massive an object is, the more it curves spacetime.

When an object becomes so massive that it curves spacetime to the point where it creates a singularity, it is called a black hole. A singularity is a point in spacetime where the curvature of spacetime is infinite. This means that the laws of physics, as we currently understand them, break down at a singularity.

Why do we believe that things fall through black holes?

The theory of general relativity predicts that anything that falls into a black hole will eventually reach the singularity. This is because the gravitational pull of a black hole is so strong that nothing can escape it, not even light.

There are a number of observations that support the theory that black holes are real. For example, astronomers have observed stars that orbit around invisible objects that are thought to be black holes. They have also observed jets of gas that are ejected from black holes.

Is it possible that black holes are only balls with enormous mass or gravity?

It is possible that black holes are only balls with enormous mass or gravity. However, the theory of general relativity predicts that black holes should be singularities. If the theory of general relativity is correct, then black holes must be singularities.