Why is the temperature lower at higher altitudes?
As you go higher and higher, the number of molecules above any given population of molecules at a given altitude grows to be less and less. And since these guys are all moving around randomly, a greater number are more likely to move away from the denser area because they aren’t being pushed down by as many of their neighbors; and as they leave, they take their energy (“heat”) away with them. And that is why it’s cooler at higher altitudes.
