What is the air pressure in the atmosphere?
Air pressure is the weight of the air above a given point. This changes everyday at the surface and is different at different locations....Also, the pressure falls as you go upward into the atmosphere.
Temperature differences is why air moves in the atmosphere. Hot air rises, cold air falls. With these temperature difference comes pressure differences and these temp. and pressure differences are what keep the air moving. Theoretically, if there were no temp. or pressure differences in the atmosphere, air would not move.
When we inhale, the diaphragm increases the volume of space in the chest, and this leaves the air pressure in the lungs lower than that of the atmosphere. As the atmospheric pressure is then greater than the pressure of air in the lungs, the pressure of the atmosphere (or atmospheric pressure) will force air into the lungs.