The wierdness of gravity

You're mixing up gravity with electromagnetism. They are two seperate and distict forces of nature. The force of gravity is proportional to the mass and distance of an object. The sun is the most massive object in our solar system, which means its gravity dominates that of any other object locally. Gravity however is a very weak force. Our sun orbits the galaxy because its mass, and thus its gravitational influence is large enough to be affected by the galaxy's centre of mass/gravity. Likewise, our earth is far less massive than the sun, and thus isn't influenced nearly as much by the galaxy's gravity, but because of its proximity, is instead influenced more by the suns gravity. Now to the reason why clouds and polution appear to defy gravity is a question much simpler than it first seems. Clouds are made of water vapor, which is a gas. Like any other gas, it is a collection of elements, or in the case of water, a collection of water molecules. When anything is in a gaseous state, the elements or molecules are very spread out from each other. A single water molecule by itself has very little mass, and thus is able to maintain a state of buoyancy in the atmospere. A water molecule has just enough mass though to remain captured by the earths gravity. Think of it like a submarine maintaining buoyancy under water. It has just enough mass to maintain its position under water without gravity influencing it enough to sink to the bottom. Water in its liquid form is just the opposite. The molecules are much more tightly packed together, which gives liquid water a collective mass. The collective mass of liquid water can't overcome the force of gravity on earth, and this gives us oceans, lakes, ponds, and rivers. So what causes anything to change state from solid to liquid to gas? If you haven't already guessed it, it's temperature. Every single element known to scientists can exist in any one of these three states. Ever hear of liquid nitrogen, or see people handling the stuff on TV? It's the same stuff that we breath in the atmosphere, only in liquid form. It only exists in liquid form at extremely cold temperatures though, and is why you see vapour coming from it when handled at room temperature. Hope that answers your question.