Why do certain metals feel colder to the touch compared to other materials, even when they are at the same temperature?
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Most of the counterintuitive things about how temperature “feels” comes down to two facts.
The first fact is that heat energy flows from hotter things to colder things, that is to say, from a higher temperature to alower temperature. And a key detail of this fact is that some materials are more conductive, so heat flows *faster.*
The second fact, and this is the counterintuitive one, is that nether a thermometer or your body can actually sense the temperature of the outside. They can only sense the temperature of themselves.
Your body has nerve sensors for heat and cold, but these cannot tell how hot something is outside the body. They can only tell how hot or cold your fingertip is when you touch something. Did your finger go below expected temperature or did it go above it?
But unlike a thermometer, your body can’t actually let itself reach the temperature of what it’s touching. Pick up an ice cube and your fingertips might drop a few degrees. Your body is immediately working to warm your fingers back up, because blood from the rest of your body is coming in at body temperature. Your body isn’t telling you what the temperature of the ice cube is, it’s actually telling you “we’re losing heat from our fingertips.”
So when you touch something, it’s not so much a measure of what the temperature of the object is, but rather how much heat is entering or exiting your body. And you can see why this is so – if your body wanted until the fingers were frozen to say “yeah that’s actually pretty cold” or waited until they cooked to say “oh that’s hot” it would be a pretty useless alarm. Something feels hot when it’s transferring a lot of heat into you. Something feels cold when it’s transferring a lot of cold away.
How the rate of heat transfer is proportional to the difference in temperature. If something is 10 degrees colder than your skin, it will transfer heat away at twice the rate of something 5 degrees colder than your skin. But something which is 5 degrees colder and twice as conductive as something 10 degrees colder will transfer at the same rate, and thus feel the same.
Metal feels colder than other materials when it’s cooler than your body, because heat leaves your body faster.
But metal also feels *hotter* than other materials when its warmer than your body, because heat *enters* your body faster.
Metal at exactly your skin temperature doesn’t feel like anything, but this is a rare situation.
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