The original post: /r/askscience by /u/OkraHeavy on 2025-02-19 03:22:46.

Convection as I understand it is the term for how warmer, less dense air rises, whereas colder, denser air, sinks. Shouldn’t the highest parts of earths atmosphere be hot? If this is the case, how come the higher in elevation you go, the colder it gets? Like how mountain tops have much colder temperatures compared to surrounding areas? Does it have something to do with the sun warming things up, and the lack thereof in the higher atmosphere? Like how there is very little air the higher you go?