Temperature is the amount of kinetic energy in a system. Are we feeling the force of the molecules hitting our skin when we detect something as being hot? Do we feel the kinetic energy in our skin decreasing when something feels cold? What do we actually feel when we detect temperature differences between our bodies and the objects with which we come into contact?
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What we feel is the transfer of heat energy between our skin and the object we are touching. If energy is transferring from the object to our skin out body interprets it as feeling hot, while if energy is transferring from our skin to the object our body interprets it as feeling cold.
The questions “what is “temperature” and how do we measure it” and “how do humans feel temperature” are two different issues, one is physics, the other biology.
Since you appear to be asking about human sense – we don’t feel temperature we feel *changes in temperature* and sometimes our senses are cheated by the presence of chemicals that interact with our nerve endings.
This is why being in 70F air feels so different from being in 70F water. Both are the same temperature but what we are feeling is the flow of heat outwards from our skin into our surroundings. Air is a great thermal insulator so it pulls heat out slowly, so we feel ‘comfortable’ in 70F air. But water sucks up heat like Greta Van Sustern goes through hotdogs so we feel a huge outflow of heat into 70F and it’s chilly to be in.
Now human thermal comfort is also tied to our ability to sweat, so 80F air on a dry fall day feels nice where as 80F in 100% humidity could very well be life threateningly hot (a “wet bulb” event)
Finally, some of our temperature sensors can be fooled by chemicals. Capsaicin (from hot peppers) and menthol (from mint-family plants) both trick our hot and cold nerve ends respectively. That’s why ‘hot’ peppers feel ‘hot’ (even though they might actually be cold) and why mint gum or soothing chest rubs might feel cold, even though you are actually hot.
The thermoreceptors in the skin are nerve endings that respond to changes in temperature – some to warming, and some to cooling. (The exact mechanism isn’t fully understood.) But it is primarily change in temperature that triggers them, not absolute temperature. So if you grab a cold can from the fridge it will feel a lot colder than the (actually equal temperature) plastic bottle because the aluminum conducts heat energy away from your skin a lot faster than the plastic does. When you detect something as hot I guess it is sort of correct to say that you are feeling the force of the molecules hitting your skin, but only in a very roundabout way – the energetic vibration of those molecules is what heat is, and a hot thing will transfer some heat energy into your skin, changing the temperature of your skin, which is what activates the warming thermoreceptors. It’s sort of like saying that when you hear the sound of a motor running, that sound is the kinetic energy of the motor being detected by your body – which of course, it is, but in a roundabout way
You pretty much got it from a physics perspective. A couple of things to note. Temperature measures the average kinetic energy of a system, not the total. How hot/cold something feels is ordinarily determined by the rate of the kinetic energy being transfered. The rate of heat transfer will be based on the materials’ thermal conductivity.
The actual “feeling” of hot and cold is more of a biological question. Biology could give an explanation involving nerves, the brain, and whatever else may be involved. However, your post seems more targeted to the physics of what’s happening.
We are feeling the increased temperature of our skin/body, and more specifically we are feeling the rate of heat flow into/out of our body.