Everyone knows air contains water.....in the form of water vapor, it forms our beautiful (and sometimes, deadly) clouds. Only so much water can be held by the air, and when that limit is exceeded, the water spills out, in liquid form, as rain. The amount of water air contains at any time and location is called "relative humidity". Our Desert area often has relative humidity nearly zero, no water in the air. Humid areas like the Southeast often have huge amounts of water in the air. When relative humidity approaches 100%, the water begins to "leak out" of the air. Often as rain. As I grew up in the Midwest, I knew full-well about "humid": we sweated profusely often, clothing sticking to pour bodies. Where I live now, "sweat" is more intangible: we sweat, but no liquid pervades our clothing: the water "sweated out" evaporates so quickly no evidence of it's presence is left (except possibly the "stink"). This brings the conclusion: Which air is "heavier"? Dry air or wet air? Frank