Air Pressure

The air around us is held to the earth by gravity. This invisible force pulls down air molecules giving them weight. Although we may not even feel it, the weight of these air molecules is an awesome 14.7 pounds of pressure per square inch! It is this force on any given surface which is known as air pressure.

Air pressure is constantly changing due to the heating and cooling of the earth's surface. As air warms it expands. Because it is less dense, or lighter, it rises allowing heavier cooler air to flow in underneath. In turn, the warm air cools as it rises and begins to sink. This variation of air pressure and movement of air molecules leads to the development of winds and affects our daily weather.

We can measure changes in air pressure using a barometer.

This activity will help demonstrate how air pressure affects you.