I'm working on a potential sci-fi story that takes place on a post-apocalyptic Earth. The idea is Something Horrible 1A happens, then, 15-20 years later, Something Horrible 1B comes to finish us off. In a perfect world, the Moon is gone after 1A. Initial possibilities included a long orbit double comet (first hits the moon, destroying both and partially wrecking Earth), then the twin comes around (follows-up) a couple decades later to hit Earth and finish the job. Then I started wondering what would happen if a wormhole experiment on the Moon went awry, wormholed the Moon through Earth to the other side? Would the energy/radiation of the event wreck Earth enough for 1A? Basically, what would happen to Earth? Then, would it make "more sense" (in this completely science fiction scenario) for the Moon to return 20 years later near enough to the Earth to crash into it, or to reappear immediately in a 2 decade slow degrading orbit?