Eli5 why the upper atmosphere is cold

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

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Light travels to earth from the sun. Our atmosphere or rather air doesn’t absorb visible light as it’s transparent. The earth absorbs the light, causing it to heat up. Conductive heat is the process of something hot heating up something else by directly touching it (like you grabbing a hot pan). So the hot earth directly touches the air molecules above it heating it up. Those molecules heat up the air molecules above them and so forth. So the hottest air is on bottom and gets cooler as it rises. Though air is turbulent (chaotic and moves around) so it’s not perfectly measurable that easily. But as a system, air is typically hotter the closer it is to earth.

Notes: this conductive heat transfer isn’t the only thing responsible for heating you up. You also absorb radiation, aka the sunlight, like the earth does, which heats you up. So you get conductive heat from the air and radiation directly from the sun.

The thermosphere is also hot. Its chemical makeup makes it a protective layer for our earth. Meaning it absorbs uv rays (invisible light). This causes the thermosphere to heat up, similar to how the earth absorbing light causes it to heat up.

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