Heat Transfer, Temperature and Human Senses

Humans cannot sense temperature.

When you think you are noticing that something is cold or hot is actually just the direction that heat is moving and the speed at which it is moving.

So, if heat is moving into you, you sense that something is warm, and if the heat is coming in quickly you sense that it is hot. If heat is leaving you, you sense that something is cool. If the heat is leaving you quickly, you sense cold.

You can see this easily. Touch the metal leg of your school desk with one hand and the top of the desk with the other. The leg of the desk will feel cooler. You know that they must be at the same temperature. After all they’ve been together in the same room for a long time. They feel different because metals are better at taking heat from your hand. So, the hand touching the metal leg is losing heat faster, so it feels colder.


You can see the same thing if you have been out playing in the snow. If you have been outside for a while and then come inside to have lunch, when you wash your hands it can feel like the water is burning off your skin. Of course, you know that it isn’t but the nerves in your hands don’t. That’s because they have gotten cold while outside, so the water which normally would only be a little warmer than your hands is MUCH warmer than your hands. As a result, heat is transferred into your hands very quickly which your brain interprets as HOT.


Perhaps one of the best ways to see this is the get three bowls of water: ice water, room temperature water and hot water. Place one hand in the ice water and one hand in the hot water. After several minutes, move both hands to the room temperature water.

The hand that was in the hot water will have warmed up and will be warmer than room temperature. Heat will move from this hand into the water and your brain will sense that the water is cold.

The hand that was in the ice water will have gotten colder than room temperature. Heat will move from the water into this had and your brain will sense that the water is hot.

In simplest terms, your hands will be disagreeing about the temperature of the room temperature water.