I've spent the past month or so immersed in Penrose diagrams. Some of the implications of the math and diagrams include white holes (opposite of black holes - spew matter outwards), infinite universes contained within one another other, anti-gravity universes, and things like this. You can also fall into a black hole and make it out into another universe instead of meeting the singularity (at least, an idealized, rotating black hole). Anyway, cool stuff.