What causes air pressure?
Air has pressure because it has weight. At sea level and at 32 degrees F a column of air one square inch in size and 600 miles high weighs 14.7 pounds. Because we are immersed in it the weight we feel comes not only from above but from all sides as well. We don’t notice air pressure until a difference is produced, such as expanding your diaphragm and causing air to rush into your lungs to equalize the difference. Imagine a cardboard box one square foot on a side. That’s 5184 pounds of air pressure acting on the box since one side is 144 square inches and there’s 14.7 pounds on each square inch. Now evacuate the air from inside the box and it will be instantly crushed because of the difference in pressure. Temperature will cause a change in pressure since warm air is thinner. Pressure decreases with altitude since there’s less air above and around you. Humans can’t live much above 10,000 feet high.
