How to Predict the Motion of Two Objects in the Universe

physics is telling a story, and that story is always approximate. The reality never matches the approximate stories we try to use when we tell physics stories. In i there's an infinite number of bodies out there in space, and gravity works for over infinite distances. But usually you can get away with disregarding that. You don't have to care about what's happening in andromeda when you're doing the calculation of whether your satellite is going to go around the earth. So here we're talking about the scenario where you have two bodies, and everything else can be ignored without change anything,. down to tenth decimal place or something.