Question

why does the density of air become lower in the upper part of the atmosphere?​

Answer 1

Explanation:

because at the upper part of the atmosphere, there is less weight on the air molecules, making them less compressed. The air at lower altitudes is denser because it is pressed down by the weight of all the air molecules above.

Answer 2

because at the upper part of the atmosphere, there is less weight on the air molecules, making them less compressed. The air at lower altitudes is denser because it is pressed down by the weight of all the air molecules above.