Dont know if I asked the question right but here goes…. There are times where the temperature is 75F and it’s cloudy and feels cool. There are other times where it’s 75F and sunny and I’m sweating outside. Obviously the sun right? But the temperature is the same? Does the sun not affect the temperature all the time. Also I’ve been in 50 degrees in a humid climate and it feels a lot colder than 30 in a dry climate. I always thought temperature was hot or cold but I feel like sometimes there’s more to it than that. Also I’m well aware of humidity and heat and also wind chill. I’m not referring to those things
In: Planetary Science
The air temperature is how fast the molecules in the air are vibrating – you can think of it as the reading you’d get if you trapped some air in a sealed test tube with a thermometer.
As you’ve noticed, it doesn’t exactly measure “how will I feel if I go outside”. That depends on the solar heating, how much humidity is in the air (which affects how much your sweat cools you), whether there’s any water droplets in the air (which affect whether your clothes/skin stay dry) and how much wind there is (which affects how effective your sweat is, *and* how much heat gets blown away from your skin).
If your weather service talks about wind chill factor, that’s a better reading of how it feels outside, but it doesn’t cover sun or humidity effects. There’s a reading called the ‘wet bulb’ temperature that factors in humidity, but you don’t see it much anymore.
One way to think of temperature is that if two objects have the same temperature and they are in contact with each other, neither temperatures will change. In contrast, if an object with a higher temperature is in contact with something with lower temperature, the high temperature object gets cooler and the low temperature object gets hotter. The rest boils down to what number you assign to what level of hotness.
What you feel depends on how quickly heat leaves your body. On a hot day, or when you’re under a blanket, or in the sun, or standing on hot pavement, you will feel hotter than other days because for one reason or another heat is having trouble flowing out of your body.
Even something as simple as blood flow to your skin, or what you ate, can influence how hot you feel because they influence the way your body produces and moves heat around.
Temperature is how fast the molecules in an object are moving.
Your skin is not a thermometer, though, at least not a good one. When you touch something and it feels hot or cold, you are actually feeling the *flow* of heat.
Say you have a piece of iron at 75°F and a piece of wool at 75°F. The iron will *feel* much colder than the wool because iron is conductive and heat from your body is quicky flowing into the iron.
There are two main things to consider: 1. Your “feeling” or “sensation” of temperature is different than actual temperature. 2. Your body has an internal furnace creating a lot of heat that needs to be constantly cooled down so your body doesn’t overheat.The surface of your skin is where your “temperature sensing” is located but it’s also where you need to shed heat into the environment from your core. Your feeling of temperature is therefore related to how well or unwell you can shed that heat. So in a 75F environment that is being warmed up to that temperature, you yourself are being warmed up so it feels warmer. Otherwise a 75F environment that is cooled down to that temperature, you are being cooled down so it “feels” cooler.
Veritasium has a great old video that addresses this. In short he interviews people on a cold Australian day and has them feel a book and a hard drive and asks them what temperature they “feel”. The book feels warmer, whereas the hard drive feels colder. He then uses an infrared thermometer to show that they are both the same temperature and asks them how that changes their reasoning. Objectively it makes sense that two inert inanimate objects on a cold day would be the same temperature of the environment. The difference they realize that it’s the conduction of heat from their hand to the object that is different despite being the same temperature. Their hand warms up the surface of the book so it feels the same temperature and that heat stays on the surface in contact with their hand, whereas the hard drive conducts heat away from where their hand is touching so it continually feels colder.
Temperature is just how fast the air molecules are vibrating. You don’t feel temperature, you feel heat transfer, which is related but not equal. It depends on other things like humidity and how sunny and windy it is.
What you are asking is “what is the sensation my skin feels that makes me feel hot or cold”
1. Your body is a heat engine that wants to stay at 98.5°. This is most easily done when your environment is below 98.5°, around 70°. This is why you feel “hot” when it’s above 80°.
2. What does your body feel. The “temperature” of an object is not the same as its rate of transmission. A cold spoon feels much colder than a cold book, both kept in the fridge. Air is not very dense, so any change to that fluid will affect the temperature you feel.
3. Humidity adds a ton of water to the air. Typically, more humidity makes air warmer and less makes it colder. This is why dry frigid air is worse than snowfall air, and why 110° dessert heat isn’t as bad as muggy 80°. This mostly has to do with evaporation, the main form of cooling the human body. The more water in the air, the more heat needed to evaporate your sweat. More evaporation in dry air = cooler, less in humid air = hotter.
4. The sun heats the earth, which heats the air. If the sun hits you, you will get warmer. When it hits the water, it evaporates, when it hits the ground, the ground gets hot, cold air gets close to the ground and the hot air rises. When it gets away from the earth, it gets cold. The sun does not heat the air in any meaningful way.
I like to think of *felt* temperature as how well/fast what you are touching (whether it’s solid or a gas like air) can conduct heat to you or from you.
That in turns depends on the property of that material. That’s why you can stick your hands in to the oven to grab the tray of chicken, but burn your hands if you grab the tray with your bare hands. Even though the air and metal inside the oven are at the same temperature.
As for the sun, it radiates heat directly. You can absorbs that heat and feel it. But it doesn’t make sense to measure temperature of air in sun because a temperature sensor will react to both the ambient temperature of the air and the heat the sun radiates and hits the temp sensor with directly, and how much the sensor reacts to the latter depends on the material and the surface color of the sensor.
Therefore, the only temperature of any outside that can be compared and referenced and quoted is the ambient temperature of the air, which has to be measured in sun shadow.
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