Chapter 30, Problem 4RQ

Why doesn’t gravity flatten the atmosphere against Earth’s surface?

To determine

The reason behind gravity does not flatten the atmosphere against the Earth’s surface.

Answer to Problem 4RQ

The reason behind gravity does not flatten the atmosphere against the Earth’s surface is due to the density of the air.

Explanation of Solution

The force of gravity pulls down the atmosphere, because of which the density of air varies as the altitude changes. The greatest density of the atmosphere is on the surface of the Earth due to gravity, and the density gets thinner with increasing elevation.

The density of the air is like the density of a deep pile of feathers, which is greatest at the bottom and least at the top. But, unlike the pile of feathers, the atmosphere does not have a distinct top. It gradually becomes thinner to the near-vacuum of outer space. More than half of the mass of atmosphere lies below the altitude of $5.6\text{km}$ and remaining lies below an altitude of $30\text{km}$.

Conclusion:

Therefore, the reason behind gravity does not flatten the atmosphere against the Earth’s surface is due to the density of the air.