Why does the Earth keep spinning?

[PaulR]

The difference is .....

A black hole has an inside and outside, you can pass one way across the event horizon.

The universe has nothing outside it, that's why it's the universe.

How do you KNOW there's nothing there?

a black hole has an event horizon over which it is not possible to pass any information. If one is already inside the black hole then you can never have any knowledge of what is on the other side, in fact you don't even know there is another side because you can never get near to the event horizon.

Which sounds like our universe to me.

 

[spiney]

The physics of black holes is well understood (that's why they're called "black holes", the term coined by John Wheeler!).

We don't know what would happen at the singularity, where physical laws break down, but we do know all the consequences.

However, as I keep saying, the universe does not have an outside. There's no surface, no boundary. There is no "outside".

(if u want to speculate about possible "other universes", ok, but it doesn't change this!).