Now my question. Assuming that (1) the Moon-like body is not going to break up from the planet's gravity (I know, I know, it probably would, but call it creative license), and (2) the Moon is not going to actually impact the planet, what would the geophysical/environmental effects on the planet be as a result of this near-miss? Weird gravitational fluxes? Major seismic events? What and why?
Thanks for any help. I've been trying to get deeper into the real science for this particular setting, but this is the kind of question that doesn't turn up very often in the "world-building" books and web pages. Any help is appreciated!