Replace the uninflated balloon with the the one you just blew up. Write down what happened. The balance would always tip toward the inflated balloon. The weight of Earth's atmosphere is always pushing down on us with its weight. We define this weight pushing in on us as atmospheric pressure .
Pressure is defined as force acting on a unit area .
Scientists have calculated that the Earth's atmosphere exerts a force on our bodies equal to 14.7 pounds per square inch . Another way to think of it is that a one inch column of air as tall as the atmosphere would weigh 14.7 pounds. This measurement, of atmospheric pressure at sea level, is also known as 1 Atmosphere of Pressure, or 1 ATM . Now, we know water definitely has weight, and weighs much more than air and thus exerts a greater pressure. A one inch column of water 33 feet tall weighs 14.7 pounds.