How are some black holes’ event horizons bigger than others?

Question

If their mass is always contained in a singularity and their density is infinite, how are some black holes supermassive and others are not?

In: 5

Answer 1

Density and mass are not the same thing. The radius of the event horizon is proportional to the black hole’s mass, not its density. Remember that density is just an object’s mass divided by its volume, so the density of any object approaches infinity as the volume approaches zero, regardless of how much mass there is. The singularity’s density may be infinite, but its mass is not.