Eli5 why the upper atmosphere is cold

Question

Mostly I’m wondering why it gets colder when you go higher if heat rises? Does it, like, dissipate?

In: 5

Answer 1

In order to measure heat, we need to measure the thing that is hot. The upper atmosphere is a lot less dense than the lower atmosphere, so *in a sense*, yes, it does dissipate, but only because the things that are hot (the air molecules) are more spread out.