Why does atmospheric pressure decrease as you go higher in altitude on earth?

When you go higher in altitude, the air pressure around you decreases. This is because the air is thinner at higher altitudes and there is less air above you pressing down.

The atmospheric pressure on Earth is caused by the weight of the air above us. The air is constantly pressing down on us from all sides. But the pressure is not the same everywhere. It is higher at lower altitudes where the air is thicker. And it is lower at higher altitudes where the air is thinner. The atmospheric pressure decreases with altitude because the air is thinner at higher altitudes. There are fewer molecules of air per unit of volume at higher altitudes. So, there is less air above you pressing down. The decrease in atmospheric pressure with altitude is not linear. It decreases more rapidly at lower altitudes than it does at higher altitudes. For example, the atmospheric pressure decreases about 1% for every 100 meters you go up in altitude near the Earth's surface. But it only decreases about 0.1% for every 100 meters you go up in altitude above 5,000 meters. The decrease in atmospheric pressure with altitude has important consequences for aircraft. Pilots must be aware of the effects of altitude on air pressure. They use this knowledge to fly their aircraft safely. Atmospheric pressure also affects the weather. Low-pressure systems are usually associated with bad weather. High-pressure systems are usually associated with good weather.