Air Pressure

Air pressure is the weight of air molecules pressing down on the Earth. The pressure of the air molecules changes as you move upward from sea level into the atmosphere. The highest pressure is at sea level where the density of the air molecules is the greatest.

At sea level, the air that surrounds us presses down on our bodies at 14.5 pounds per square inch. You don't feel it because the fluids in your body are pushing outward with the same force.

Barometers measure air pressure

Meteorologists use barometers to measure the pressure of the air when making weather forecasts and studying weather patterns. Barometric pressure given in weather reports is giving the barometric reading in either inches of centimeters. Pressure on the barometer moves the column of mercury in a cylinder upward or downward. Readings of barometric pressure are taken by looking at the markings on the outside of the glass cylinder. Barometers are calibrated with inches or centimeters.

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