system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 : How do humans feel temperature differences and how precisely can we feel it?
gpt
Your body is like a combustion engine, constantly producing heat, and you need to dissipate that in order to keep it working properly. If you are losing too much heat you feel cold, lose too little and you feel hot.

The amount of heat you dissipate through your skin depends on 2 factors, the thermal conductivity and the temperature of the material you are touching. That's why air feels comfortable at around 21°C but water or a piece of metal at the same temperature will feel cold, as they will "suck" more heat from your body due to their higher thermal conductivity.

So what you are feeling is not exactly temperature, it's heat loss. And your body is very sensitive to it because your internal "machinery" needs to be at a very specific temperature to work.