How does the Earth and its various spheres lose heat?
This has stumped me since high school physics. I have an elementary understanding of how my coffee cup for radiates heat. However, I’ve always imagined that the vacuum of space would insulate the planet, or anything, like an invisible Yeti cup.
So, where does the heat go, and how does it get there?
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Heat can be transferred through conduction, convection (which is just conduction with extra steps) or radiation.
Conduction is when the atoms are wobbling (because being warm means they have more energy) and bump into other atoms, making them wobble too. That’s why when you touch things it warms you up. Despite the name, radiators are mostly doing this.
Radiation is when the atoms release that energy by throwing out photons (light), (specifically but not only in the infra red variety). Instead of the atoms bumping into you and making you move, they yeet tiny tennis balls at you, a d that makes you move.
Conduction is WAY more efficient than radiation. That warmth you feel what you step into sunlight is because the sun puts out A LOT of radiation. And the reason you cool down so quick when a cloud goes over is because the colder air is touching you and it sucks all the heat out of you much more efficiently.
In space it’s a vacuum so a planet can only lose heat by radiation.
You are right though that atmospheres do insulate. Air isn’t all that good at being warmed up by *sunlight*, but some of it (say, greenhouse gases) are great at abosrbing (and thus blocking) infra red.
What happens there is the sunlight (which is partly infra red, but also lots of other visible light) radiates from the sun towards the earth. Some of that gets caught by the atmosphere but most hits the planet itself, which warms up. But as we just said, things that are warm then start throwing infra red tennis balls right back out again to shed that excess energy. Or in science terms the ground absorbs sunlight and re radiates infrared light. THAT heat is what gets blocked by a thick atmosphere.
So an airless rock like the moon will heat up in sunlight, and then cool down a lot because even though it’s only radiating heat, there’s nothing to absorb that radiation and keep it around. So objects in space tend to be cold +unless in direct sunlight) but space itself doesn’t cool you down.
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