[SOLVED] Moon's future rotation 1. The problem statement, all variables and given/known data COnsider the earth and moon as if they formed an isolated system. The length of the day increases every year, a feature attributed to tidal effects. At some distant time in the future the earth moon system will be orbiting such that the same face of the earth will be pointed at the same face of the moon and the distance between the earth and moon will reach a final value. Assuming that the earth and moon can be treated as uniformly dense spheres and that the masses will be what they are at present, what will be the final distance between the earth and moon? 2. Relevant equations 3. The attempt at a solution According to conservation laws, energy and angular momentum should be conserved since according to the problem there is no external force to provide a torque. From the question, at the final distance, the orbital period of the earth will = the orbital period of the moon. I'm not quite sure where to go from there though. A push in the right direction would be appreciated.