> I understand the definition of a wormhole is the entrance is a black hole, the exit is a white hole, that's what I read once. Means one way journey. This is

> I understand the definition of a wormhole is the entrance is a black hole, the exit is a white hole, that's what I read once. Means one way journey. This is not the definition. The source of your confusion might be that the simplest solution to the Einstein field equations that contains a black hole (called Schwarzschild solution[0]), also contains a white hole and a separate, let's say, "universe" when considering its so-called maximally extended[1] solution. The two universes (region I and III in the diagram in [1]) are separated by the black hole and the white hole (region II and IV in the diagram in [1]) and there's only an "infinitesimally small" connection between them, called an Einstein-Rosen bridge[2], which is usually considered to be the simplest example of a (non-traversable) wormhole. People have speculated that on the "other side" of a black hole there's a white hole ejecting the matter swallowed by the black hole into another universe (which would kinda be a wormhole) but this is pure speculation. [0]: https://en.wikipedia.org/wiki/Schwarzschild_metric https://en.wikipedia.org/wiki/Schwarzschild_metric [1]: https://en.wikipedia.org/wiki/Kruskal%E2%80%93Szekeres_coordinates https://en.wikipedia.org/wiki/Kruskal%E2%80%93Szekeres_coord... [2]: https://en.wikipedia.org/wiki/Wormhole#Einstein%E2%80%93Rosen_bridges https://en.wikipedia.org/wiki/Wormhole#Einstein%E2%80%93Rose...