Physics Asked by Pong Lenis on May 13, 2021
Okay I saw all these people saying that new studies show black is better to wear in the heat. They say it’s cause “black clothes absorb the heat emitted by the body while white clothes reflect it back to the body”.
Here’s what I don’t get: These people are talking about heat and light as if they’re both the same thing. Light and heat are two different things. To my knowledge color doesn’t absorb/reflect heat, it absorbs/reflects light. A black color absorbs all the light it gets and then transforms it into heat. A white color reflects all the light so it doesn’t produce any heat.
So if they’re saying black clothes “absorb heat emitted by the body” are they saying that a human body emits light like the sun and then that light is absorbed by the inner part of our black shirts and transformed into heat? Or what?
The term "light" is a little ambiguous, because for some it means visible light, and for others it means any form of electromagnetic radiation. But I agree with you, that black and white should be more about visible light than infrared radiation. If we are right, then it's better to wear white, because white will reflect the incident visible sunlight, while not doing anything different with the infrared radiation from our bodies. I suspect the conventional wisdom may have got this one right, and the "correction" to it might be in err. Perhaps it needs to be an episode on "Mythbusters."
Correct answer by Ken G on May 13, 2021
Black is not the right color to be wearing in Summer. I don't have to know thermodynamics or to have studied Physics to know this. Just experience alone is enough. When I was younger, I used to wear dark colors all the time, even in Summer. I wasn't into Gothic stuff, though. When I did that, my black jeans that I'd been wearing and my dark grey shirt was burning on my skin. It was only when I'd decided to change my clothes to light blue jeans and a light colored shirt that I found relief, and when I did that, I didn't feel any of my clothes burning on my skin no matter how long I stayed out in the Sun. This experience is proof enough that the sources that say wearing black keeps you cool is wrong. Even in shade, black keeps you feeling hot for a longer period of time than light clothes, which almost immediately let you feel cool.
Answered by Zeletra on May 13, 2021
It depends whether you expect to be in sunlight, i.e. whether the ambient light and heat in your environment is more radiative than your body.
If your summer environment is to be shut in a dark room, then black would be marginally better than white - I suspect it would be a such a small difference as to not be noticeable to the wearer.
If however, you expect to be in sunlight in summer, in almost all conceivable circumstances sunlight radiates more than your body radiates (perhaps with the exception of sunrise / sunset), so you want to reflect the sunlight with highly reflective (i.e. white) clothing in order to avoid gaining unwanted heat. This is by far the most likely scenario!
In the extreme, a material white on the outside and black on the inside would be better from purely a radiative point of view - but would be thicker and so worse from an tranmissive / insulation point of view.
Answered by TopCat on May 13, 2021
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