system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does sleeping with a thinner blanket on you with a thicker one on top feel so much warmer than the inverse, i.e. a thick blanket with a thinner one on top?
gpt
Blankets make you feel warm by trapping air close to your body. Your body is continuously generating heat as it accesses the energy in your food, so you are continuously warming up the air that comes into contact with you.

If you have a thin blanket right against you, it is likely better able to fit against your body than a thicker blanket would be. The small volumes of air that are trapped near you warm up quickly. When you have a thicker blanket against you, it is probably not as form-fitting, so you would be having to heat up larger amounts of air.