Atmospheric pressure is the force exerted by the weight of the atmosphere at any given altitude. Because air molecules are constantly falling and colliding, they exert a measurable pressure on all surfaces, with the magnitude of this pressure decreasing significantly as altitude increases due to the reduction in overlying air mass. This pressure is measured in various units, including Pascals (Pa), millibars (mb), or atmospheres (atm). Variations in atmospheric pressure are critical in meteorology, often correlating with changes in weather systems and air density. Furthermore, atmospheric pressure significantly impacts physical systems, notably the human body, as rapid changes in pressure, such as those experienced during deep diving or ascending in an aircraft, require physiological adaptation to prevent adverse effects on gases dissolved in the bodily fluids.