What Is Air Pressure?

What Is Air Pressure?

Air is all around us—even though we can’t see it. The air that fills our atmosphere is made of billions of tiny molecules. Each molecule is so small, we can’t see it with our eyes. But together, these air molecules have weight. The weight of all this air creates something called air pressure. Air pressure is the force of air pushing down and around us from every direction.

Even though air feels like nothing, it’s actually pressing on everything all the time. Imagine living at the bottom of an invisible ocean of air. That’s what it’s like! The air above you pushes down because of gravity, and all the air around you pushes in from the sides too. But we don’t feel crushed. This is because the air inside our bodies pushes back, so the pressure is balanced.

You might have noticed air pressure in your daily life. For example, when you ride in an airplane or drive up a mountain, your ears might pop. That’s because the air pressure gets lower as you go up higher—there is less air above you pressing down. When you drink through a straw, you suck air out of the straw, lowering the pressure inside. The higher outside air pressure then pushes your drink up into your mouth. Balloons stay inflated because the air inside pushes outward against the balloon, while air outside pushes in.

Air pressure is important for weather, too. A barometer is a tool that measures air pressure. If the air pressure is high, it usually means sunny and clear weather. If the air pressure is low, clouds and storms may be coming. That’s why weather scientists pay close attention to air pressure every day.

You can see air pressure in action with fun experiments. Try crushing a can by heating it with a little water inside, then quickly cooling it in ice water. The sudden drop in air pressure inside the can lets the stronger outside air pressure crush it! Suction cups also work because air pressure outside the cup holds it tight to the wall.

Interesting Fact:
Mount Everest is so high that the air pressure at the top is only about a third as strong as at sea level!