Can black holes make wormhole?

Question

Before you read I want you to know that here I'm a layman and I was just wondering.

It is often visualized, how wormhole works using a curved paper like C, and making a short cut through there:

But I don't understand, how this shortcut is made by itself. I mean why spacetime is supposed to be like C in first place?

But I can speculate. If there is a large enough black hole at top of the C, it can make its path through bottom of C, thus making a wormhole? (But probably it would still be a black hole, visible at two sides of spacetime.)

Answer 1

Yes, they can. The metric of the charged (Reissner-Nordström) or/and rotating (Kerr) Black Holes seems like one of the sides of a wormhole.

There is nothing what would "curve" the spacetime into such a C-like form, only the diagram has to explain something. There is no internal measurement which could differentiate such a C-shaped spacetime from a planar one. An essential point of the General Relativity, that it operates exclusively with intrinsic properties.

The idea of the wormholes is coming that rotating/charged black holes seem to have such a geometry, like if they would bind multiple Minkowski-universes together (or the different points of the same one). But all of this is purely hypothetical.

No one could see a black hole event horizon until now - they are too small, and too far away. The proof behind that black holes even exist is coming from the spectrum of the interstellar gases falling into them. Without this proof, even the existence of the black holes would be only a hypothesis.