gen-briefly-explain-atmospheric-pressure-and-altitude-and-one-co-c56c

Briefly explain atmospheric pressure and altitude and one common misconception about it.

# Atmospheric Pressure and Altitude **The Basic Relationship:** Atmospheric pressure is the weight of air above you pressing down. As altitude increases, there's less air above you, so pressure decreases. At sea level, pressure is about 14.7 psi (101.3 kPa), but at the top of Mount Everest, it's only about one-third of that. **Common Misconception:** Many people think pressure decreases *linearly* with altitude—that if you go up twice as high, pressure drops by twice as much. **Reality:** Pressure decreases *exponentially*. About 50% of the atmosphere's mass is below 18,000 feet, even though the atmosphere extends much higher. This happens because air is compressible—the air at lower altitudes is compressed by all the air above it, making it denser. As you go higher, there's less weight compressing the air, so it becomes less dense more quickly than you might expect. This is why climbers experience severe effects above 26,000 feet (the "death zone") even though they're not yet in space—most of the breathable air is already below them.