Question

Why does the atmosphere become thinner with altitude?

Answer 1

The atmosphere becomes thinner with altitude mainly because of the decreasing air pressure and density as you go higher above the Earth’s surface.

1. Air pressure is the force exerted by the weight of air above a given point. At sea level, the atmospheric pressure is highest because the entire column of air above presses down due to gravity.
2. As altitude increases, there is less air above that level, so the weight of the overlying air decreases. Consequently, air pressure decreases.
3. The pull of Earth’s gravity is weaker at higher altitudes, so fewer gas molecules are held close together, resulting in lower air density.
4. With fewer gas molecules in a given volume of air at higher elevations, the atmosphere becomes less dense, and pressure is lower, making the air “thinner.”
5. This reduction in air density at higher altitudes means there are fewer oxygen molecules available per unit volume, which is why breathing becomes more difficult as one ascends.
6. The atmosphere is compressible, so the overlying layers press down more on the lower layers, contributing to higher pressure near the surface and lower pressure aloft.