When a cloud forms on a rising column of moist air, why does the cloud always remain at that height and stop moving? Presumably the air, now dry, keeps on rising for a time, because I see no reason why it would stop at that height just because the moisture has condensed out. But if the air does continue to rise, why doesn't it carry the cloud up with it? I have a physics degree but I have never studied meteorology and it seems to me that clouds are odd things - almost a fourth state of matter to go with solid, liquid and gas.