So... one big thing I recall from the book is the collective collisions turn the world into an enormous ball of fire for decades. If (according to the simulation) the number of collisions tapers off after a couple years, does that mean the world would be habitable again in short order? I understand that, for the purposes of the book's arc, the planet needed to be rendered a literal hell for as long a time as possible... but perpetual burning seemed a bit far-fetched.