Aerostatics is the study of gases that are not in motion. The corresponding study of gases in motion is called aerodynamics. It is a subfield of fluid statics that focuses on gases. Aerostatics studies density allocation, especially in air. One of the applications of this is the barometric formula. A balloon or airship, which uses the principles of aerostatics to float, is known as an aerostat. Fields of study, Fields of study include: The kinetic theory of gases, Gas pressure, Pressure measurement, Gas density, Gas diffusion in soil, Partial pressures in gas mixtures, Atmospheric pressure fluctuation, Composition of mountain air, Cross-section of the atmosphere