What about the pressure developed on Earth’s surface due to the force of attraction between the atmosphere and Earth? For all practical purposes we live at the bottom o a huge sea of air , which extends hundreds of miles above us. Equation (2-9) cannot be used to find this pressure because of the compressibility of air. As a result the density of the air is not constant throughout the atmosphere. The density is greatest at Earth’s surface and diminishes as the distance from Earth increases.