This is a question I have been pondering for quite some time. I haven't done much research on the matter but I can't find any theories, hypotheses, or explanations of this matter. So I calculate that the best route to take would be to ask those who know about the topic better than myself. I am a student a Full Sail University and I'm getting a degree in Game Design; knowing that 99% of all games do not use true physical systems, I am wanting to keep my game as realistic as possible. I'm developing a game that takes place in outer space in a parallel universe to our own, where our Earth is instead orbiting our moon. Now I know this doesn't seem practical in any way because the Earth's mass relative to the moon's would not allow it to orbit the moon. This is just a big what if type thing and I have made it work by creating a new Earth with the same size but with less density. My question is, what would happen to the Earth in our present universe if our Earth was to switch places with the moon. What would happen if our moon had a moon 1/8 it's size? 1/4 it's size?