If all black holes are made up of an infinitely small point with infinite density, why are there “big” black holes and “small” black holes?

Question

If all black holes are made up of an infinitely small point with infinite density, why are there “big” black holes and “small” black holes?

In: 2

Answer 1

Black holes do not have an infinitely small point with infinite density in the middle. It’s just the mathematical model giving up. We need quantum gravity to understand better what’s inside them. But from the outside, it doesn’t matter much, everything behave just the same as infinite density at a 0D point, so it remains a useful approximation.

Black holes are heavy enough that they wrap spacetime around them so much not even light can escape.

The size of a black hole depends on its mass, angular momentum (rotating speed), and charge. But basically, the heavier they are, the bigger the region of spacetime that is extremely wrapped. And that’s usually what we talk about when talking about their size.