When we turn our face towards the sun on a day with clear skies: Is the heat we feel on our skin actual heat radiation from the surface of the sun or do we just feel the warmth of the molecules in our atmosphere which have been “warmed” by radiation from the upper atmosphere?
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The confusion stems from the fact that “heat” has multiple scientific meanings, but people use them interchangeably in regular speech.
We feel “heat” from molecules in our skin gaining kinetic (movement) energy and jiggling around. But there’s a few ways to make the molecules in your skin jiggle around like that.
When you touch a hot stove, the molecules in the stove are already jiggling around very fast. When they bump into the molecules in your skin, it directly kicks them into moving very fast too, which you feel as heat.
However, you can also make molecules move by transfering energy into them in other ways. Electromagnetic / thermal radiation, for example, carries energy directly. There are almost no molecules in space for the sun to transfer energy to your skin the same way a hot stove does, but radiation can travel through the nothingness of space just fine.
When that radiation travels through the atmosphere and hits the molecules on your skin, some of that energy is absorbed by them, and causes the skin molecules to start jiggling around. And then you feel that as heat.
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