Not homework here but merely curiosity. I was reading that on Titan there are rivers of methane, and that at least one is 400km long. Now I was thinking about the earth and moon; imagine that the moon becomes a copy of earth exactly, keeps all of it's features and becomes the diameter of the moon, so it has the same mountains/ocean trenches in proportion to the diameter in the moon, water to the same depth. Now the moon rotates like earth and is tilted on its axis, and the earth moves around the moon like the moon around earth. Would the water stay in the duplicate oceans and rivers/lakes with more pronounced tides, or would it get pulled to one pole of the planet? And on the Titan's methane rivers, when rotating around such a big planet as Saturn, how do the rivers form a river bed with such strong tidal forces? I'm asking this because my assumptions about tidal forces are possibly, completely wrong. Thanks!