The Earth is rotating because of constant angular momentum, right? Would I be correct in interpreting that this is because the Earth's tilt is at an angle of 23.5 degrees, and so this angle is what causes it to keep spinning? Is it possible to replicate constant angular momentum? And, to put it into comparison, would a good way of putting it be to think about a swing in a park that swings 360 degrees around the bar, then continues to swing 360 degrees forever? If constant angular momentum holds true for the Earth, does that mean that the Earth will ALWAYS orbit at its velocity? Thanks EDIT: I just read that the axial tilt of Mercury is 0 degrees (no tilt). So how does the constant angular momentum work?