Air pressure and height — Earth science, 11–13 years
Air has weight. The higher you go, the less air is above you, so the pressure becomes lower.
What air pressure is
Air may feel light, but the atmosphere is a huge column of gas pressing in every direction. At sea level, the air above us presses more strongly because there is a longer column above each square metre. Pressure is this push spread over an area, not simply the amount of air in one breath.
Why it explains height
People needed to understand why ears pop on mountains and why climbers need extra oxygen. The idea of air pressure connects both effects: there is less pressure to push air into the body, and each breath contains fewer oxygen molecules. Pressure measurements also let scientists compare places and predict weather changes.
A simple pressure model
Put a card over a glass filled with water, hold it firmly, turn the glass upside down and release the card carefully. The water’s weight pulls down, but air pressure pushes up on the card from below. If the card seals the rim, the upward push can support the water for a moment. A small gap lets air in and breaks the effect.
The common mix-up
A reasonable guess is that high places have no air, since breathing becomes harder there. They do still have air; it is simply thinner, with lower pressure and fewer oxygen molecules in each litre. Temperature and weather also change pressure, so altitude is not the only cause of a reading on a barometer.
Where it appears
Barometers measure air pressure, and weather stations watch how it changes. A falling pressure often accompanies unsettled weather, while a rising pressure often comes with more stable conditions, though it is not a perfect forecast. Aircraft, hikers and doctors also account for pressure when working at high altitude.
Keep exploring
Other languages
Loading MyLeoNes™…