If the air is moving faster that means it has higher energy and is hotter, right? If it hits my skin with a higher velocity it is transferring more energy than if it were moving slower. Both of these reasons suggest faster winds should feel hotter but they don’t, the stronger the breeze the cooler it feels. Why?
In: Physics
Oooh a common question with an interesting take. No one really brings up the added energy from momentum.
Well to address that part first: even “still” air is moving. The air molecules are bouncing around like crazy at around 1000mph (although to be more accurate, it’s a distribution of speeds). A small breeze doesn’t really change much in that regard, since a 5mph breeze is barely anything in comparison. Plus molecules don’t really have to move any faster to travel in a direction, they just have to be moving more in that direction than in other directions.
As for why moving air feels cooler, let’s talk about why *anything* feels cool. When something is cold to the touch, it means heat is transferring from your body to the substance. What youre feeling isn’t temperature, it’s heat flow. The faster heat flows out of your body, the colder it feels. Metals conduct heat really well, so they feel colder than wood, even when both are at the same temperature.
So one factor that affects heat flow is material, but the other is temperature difference. The rate of heat transfer is linearly proportional to the difference in temperature, which means heat flows twice as fast when the temperature difference is twice as high.
So all this comes together to mean that in still air, your body is warming the air around it, and that air doesn’t move very quickly, so the air right next to your skin is significantly warmer than the air in the rest of the room. If there’s a breeze, that warm layer gets blown away and replaced with cooler air from the environment. Because the air is colder, heat flows out from your body faster and it *feels* colder.
There’s also a component of this that has to do with water and evaporation that explains why moving air feels extra cold when you’re wet or sweating. I can go into that if you want.
Measuring things at stasis is surprisingly hard for nerve cells, so we in general sense and feel the DIFFERENCE between conditions.
Lets say your skin is 80F, breeze comes by and it’s only 70F; You feel it as cold since your skin is losing heat to try to heat up the air its in contact with to also be 80F.
Now… lets say it’s hot out, and both the air and your skin are 80F, what about the water in the air? Your skin is hot and sweaty… but the air isn’t as humid as your skin yet! Water is going to evaporate, which takes heat out of your skin, and the warm water vapor goes away leaving your skin colder than it used to be as the breeze goes by. You feel that as a nice cool breeze. 🙂
Now… if you live in hell, and it gets both hot and humid… breezes always suck since you never loose heat or sweat.
In your post, you seem to treat kinetic velocity, and heat as interchangeable which isn’t the case here.
You’re shedding body heat faster as the wind speed increases, thus making you feel cooler. That’s why a hot wind can still feel cool because it’s blowing that heat off of our bodies when we’re hot.
Temperature wise, wind is technically warmer than still air, but almost imperceptibly so. A very strong gust has something like 1.001x the amount of energy from motion compared to still air at room temperature.
However, what you feel on your skin isn’t really temperature. We can really only feel changes in temperature. For example, if you feel a metal object that conducts heat well, your hands cool quickly to pass the heat to the metal, and so your hands feel cold, compared to touching styrofoam.
Still air doesn’t dissipate heat that well, your hands are constantly surrounded by close to body temperature air from the heat you give off. When the wind blows, you’re exposed to the room temperature air, which is cooler than the air around you normally is. It also cools you down faster.
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