Aerostatics

Aerostatics is the science of balloons that can float in the air. Hot air balloons use aerostatic principles to stay in the air because hot air is lighter than the cool air around it. Hot air balloons are filled with hot air and when the hot air is lighter than the cool air outside, the hot air balloon rises up and floats in the air. The cooler air pushes the balloon up, and the heavier air below the balloon keeps it from sinking down.