It's a solution that assumes things like a perfectly uniform sphere of gas collapsing from infinity (Schwarzschild geometry), without any angular momentum. Even

It's a solution that assumes things like a perfectly uniform sphere of gas collapsing from infinity (Schwarzschild geometry), without any angular momentum. Even then, the ERB isn't traversable. A lot of the talk around wormholes and time travel suffers from map-territory issues. For example, if you look at the maximally extended Schwarzschild geometry (the Kruskal-Szekeres extension) you see two asymptotically flat regions of spacetime connected by a "wormhole". It's probably just an artifact of the model though, and not anything physical. A lot of the, "Math allows" stuff probably falls into that category, which is why when it comes to relativistic masses and velocities, you can't ignore quantum effects either.