The Principles of Levels
So, the principle is that lighter objects are higher than the heavier ones, and the heavier the objects, the lower they remain. As an example, when clouds are formed and following atomic reactions, heat is created in them due to the creation of kinetic energy and small particles within the steam. Then, gases mix, and their hydrogen and oxygen turn into water and fall like drops of rain. In other words, they are revolutionized, and as soon as they turn into rain, they cannot stay at a high altitude because they are heavy, and therefore, fall towards the earth. In short, they get lighter and go up, they get heavier and they come down.