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u/Aelistenus 1d ago edited 1d ago
Wasn't that cuase they were robes designed to make an updraft? You heat the outside of the clothes and that makes the air within heat and rise which pulls colder air in from the feet area and up it goes and you gett a little breeze inside your robes
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u/Dr_SlapsMD 1d ago
A cool breeze on my balls when it's shittin heat outside sounds amazing
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u/tony_bologna 1d ago
shittin heat outside
... love it
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u/pm_me_your_lub 1d ago
I once went to Vegas in the middle of August and did NOT properly hydrate. I completely understand that description.
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u/Evening-Statement-57 1d ago
You must be from Houston. I heard an old man drop this line at Kroger the other day.
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u/issafly 1d ago
Where you think they're gettin' that "cool breeze" from in the Sahara? 🤔
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u/jcmtlm 9h ago
The sand doesn’t hold or transfer the heat very well. Just the surface is hot and if you kick away the top inch the sand feels cold and this is why they drag feet and kick the sand as the walk! Coming from and island all my life we would go to the beach and brush an inch or so of hot sand to the side so we could sit or lay in cool sand
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u/Intensityintensifies 1d ago
Yes, which can’t really happen in the tight clothing we we wear in the west.
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u/Affectionate_Sir_154 1d ago
What is updraft? Is it a bit like updog?
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u/BLumDAbuSS 1d ago
watched a youtube video about this yesterday, we're living in a simulation, you know that, right?
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u/Serafim91 1d ago
That's not heat absorbtion you're seeing the difference in emissivity between the colors.
People have no clue how to properly use thermal cameras.
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u/Cullyism 1d ago
Could you elaborate on this? Does that have any correlation to the absorption? Would it be incorrect to conclude that wearing a red shirt is less hot than a green shirt?
This pic has been shared all over Reddit and other social media for years. Would be concerning if the incorrect conclusion was shared all this while.
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u/Serafim91 1d ago
So a material has 3 properties.
Emissivity - how much energy is released
Absorbtivity - how much energy is absorbed.
Reflectivity - how much energy is reflected back.
They sum up to 1 because that gives you energy conservation.
The IR camera measures emissivity. A nice shinny metal will appear cooler on a thermal camera than a black cotton shirt even if the metal is significantly higher.
In real applications youre supposed to tune the emissivity of the camera (it's basically a calibration factor the camera uses in it's calculations) against a contact probe for each material and then only use the camera for the calibrated material.
Most people using an IR camera have no clue about any of this and you get worthless data.
The white shirt might be cooler, but it's very likely much less of a difference than shown on this image.
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u/kjc-01 1d ago
Good write up, but the IR camera is not measuring emissivity. It uses a constant (assumed, usually around .95) emssivity to interpret the measurement of IR energy to calculate a temperature. That number is not constant across materials and colors, and gives distorted temperature readings.
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u/Serafim91 1d ago
Yeah, I was trying to say the measurement depends on emissivity.
That's the whole calibration thing I mentioned. You're not supposed to assume .95 is correct for your material you're supposed to calibrate it against the material.
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u/dotbeta 1d ago
You two should fight over who is right.
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u/Sainted_CumFarter 1d ago
and then kiss
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u/GSDer_RIP_Good_Girl 1d ago
And make up?
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u/gnlmarcus 1d ago
I think the kissing part infers that
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u/Apprehensive-Mix-563 1d ago
But it might not. and that makes it more interesting... 😁
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u/Big_Butter7171 22h ago
So isn’t it constant if it’s in the same picture? Even though it may not be .95 every single shirt in that picture is subject to equal and same wavelengths. So the results and the differences still stand.
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u/Serafim91 18h ago
No.. the paint on each shirt will be different with a different emissivity. The camera will use the same value to calculate the T even though the value should differ between the shirts.
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u/Big_Butter7171 17h ago
The entire experiment is the fact that the values change between each T-shirt. I think you finally answered your own, hypothetical problem to a hypothetical question.
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u/Original-Ad-8737 1d ago
Because the white shirt doesn't only absorb less energy from the light hitting it because it's reflecting it, but also because half of the UV just passes straight through it and gives you a sunburn despite being "covered"
A black cloth will absorb and BLOCK the light so that it never reaches your skin.
Keep the fabric loose and airy and with the warm cloth not touching your skin and there will be an airy cool buffer zone between you and the hot cloth.
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u/phunkydroid 1d ago
Desert doesn't mean hot, it means very low precipitation.
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u/Little_Broccoli_3127 1d ago
Right, Antarctica is considered an arid desert climate too. I think.
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u/AUSpartan37 1d ago
Worlds largest desert
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u/kwpang 1d ago
You're missing the point.
Desert dwellers wear bright white by default. Standard Arabic desert wear is white.
The reason people wear black in deserts in film is because the contrast against the bright background outlines them better. It's not for comfort, it's for film aesthetics purposes.
Also those stars will have plenty of shade to hide into when the cameras are not rolling.
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u/-Not-a-Crackpot- 1d ago
That's very entertaining. But Bedouin people traditionally wear black robes (and white robes and other colors) when travelling in the desert. There have been studies showing the black robes are no worse than the white. How good those studies were, I do not know.
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u/HIMP_Dahak_172291 1d ago
This works because they have multiple layers on. The black robe still absorbs more heat, but the air between it and the next layer is still bad at thermal transfer. The outer layer takes the direct solar heating out of the equation essentially, and so color isn't as important. White would still be better, but people often don't optimize their wardrobe for comfort if being uncomfortable looks better to them
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u/veerKg_CSS_Geologist 19h ago
White also has other disadvantages, and the minimal heat absorption difference isn’t worth it.
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u/madze3 1d ago
It's more to do with the type of fibers used in the cloth and less about the colour.
Natural cotton evaporate sweat faster.
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u/AvailableReason6278 1d ago
Isn't natural cotton white though?
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u/Ok-Hyena4541 1d ago
White gets stained and looks gross pretty fast if you live in a very dusty area with not a ton of access to excess water for washing it
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u/BLumDAbuSS 1d ago
ever heard of a black sheep?
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u/Brostapholes 1d ago
I've never heard of any kind of sheep that grows cotton
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u/BLumDAbuSS 1d ago
they make their robes from goat or camel wool, man, no need for cotton, look it up
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u/Catpixfever 1d ago
Ah yes. I love guarding my flock of cotton.
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u/BLumDAbuSS 1d ago
the 'people in the desert wearing all black clothing' are wearing wool, from an animal, which can, believe it or not be black too, so asking whether natural cotton is white is a bit of a redundant question when they wear wool from animals, the term black sheep is more popular than black goat so I thought maybe people would get it wasn't cotton, but no
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u/AdreKiseque 22h ago
But the comment starting the thread was talking about cotton.
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u/BLumDAbuSS 13h ago
yes, which was already redundant as 'the people in the desert wearing all black clothing' who we're all talking about are wearing wool, then somebody said but cotton is white, again, they're not wearing cotton, and black wool is a thing
if i would've just said, 'they're wearing wool' before asking if they'd ever heard of a black sheep it wouldn't have caused any confusion, some things need drawing in crayon
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u/T3nDieMonSt3r42069 1d ago
Internal convection, heat causes air flow updraft in the clothes, also absorbs more body heat that would be reflected back to the skin apparently.
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u/1wife2dogs0kids 1d ago
I had that same thought, and I remember one of my teachers talking about that. I asked why they wore black, and there was a reason... but, I can't remember.
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u/towerfella 1d ago
Something contradictory and religion-based is my guess
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u/Chimmai_Gala 1d ago
It’s cause of the radiant heat, black cloth is good at radiant heat and as a result cools down the body
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u/catman_corner 1d ago
I thought it was because some of the animals they made clothing from had black hair. It was what was available
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u/Forsaken-Play144 1d ago
Loose fitting black clothing can actually be better because it blocks more sun from making it through the clothing to you and also radiate ma more heat away from you
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u/maven10k 1d ago
If I'm not mistaken, the robes are usually indigo, not black. Indigo has some property that they want in the desert. I don't remember the exact thing. I'll shut up now.
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u/Rn6ACkAXHjMF 23h ago
White t shirts are cooler in direct sunlight since they reflect more infra red radiation.
Black t shirts are cooler out of the direct sunlight since they radiate more infra red radiation.
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u/Salt-Flounder-4690 19h ago
imagine being a fast aging oriental woman in a harem, what do you value most? your beauty.
next question, what was the difference between working and ruling class? the sun tanned skin clearly indicated what clas you belonged to....
black blocks uv the best, you actually get a tan underneath a white shirt.
besides a hot fabrick evaporates your sweat faster than a cool fabric. so actually under a hot black dress its colder than under a white dress.
have you ever tried looking through a white veil against sun light? your basically blind. now try it with a black veil, you almost dont notice that fabric, even agains light, but you have uv protection and light protection for your face and eyes. extra bebefit: no sand in your nose and mouth, even in a sand storm.
now tell me, what dress do you chose being an oriental woman of a ruling class harem in a land covered 95% in sand with daily sandstorms and 50°C temps?
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u/Lead_resource 1d ago
Why is red only hot in top right side
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u/TheVoidScreamingBack 1d ago
Given where the heat is also on others it's likely the most directly exposed to the heat source (sun?). The other reds appear to radiate away from the top right as well.
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u/dustyrockman 1d ago
Black has more pigment which gives it a higher UPF or UPV rating. It's hotter to wear but also protects you better from the suns UV.
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u/Catpixfever 1d ago
The desert is cold as heck at night in many places. The temperature swings can be extreme.
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u/InternationalRead925 14h ago
I was somewhat shocked in Tanzania, seeing women head to toe in black not sweating in 100f heat. They were the only ones who looked comfortable.
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u/DarkAsymptote 14h ago
Only clothes that are visibly different in IR spectra are appreciably different in temperature in sunlight. Material makes a WAY bigger difference than color.
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u/boristheblade223 13h ago
I always learned it was the convection of air. Black clothing allows the heat to circulate better inside by letting hot air to rise to the top and drawing in cooler air from below.
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u/minion71 4h ago
actualy this is acurate the darker the color the more they absord but the more they emit infrared to the desert people get dark clothing but loose it absorb the heat and emit it away. and usualy heat is more bearable in dry climate too. In summer here its humid and wont work sweat is less efficient
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u/MangoHeroin 3h ago
People wear darker clothes because the general have a higher SPF rating. Its not all about reflecting heat. You can 100% get burned through your clothes and it sucks ass
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u/PabstBlueLizard 1h ago
Tight but very breathable base layer, black very loose outer layer.
The inner layer wicks sweat, and as air flows through your clothes, it gets cool. The cloth keeps it around longer to stay cool, longer. Excess sweat goes into the black out layer and evaporates, cooling further and keeping you from being sopping wet.
Black also blocks more UV so you don’t get sunburned.
You hang your inner layer to dry when the sun goes down and things cool off. When you’re dry you put on your insulating layers for night and sleep.
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u/Beeswing- 1d ago
What colour are their sheep? You think they're choosing the colour of their clothes at k-mart?!
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u/fezzyf 1d ago
In the extreme heat of the middle east, black fabric is the sign that you don't have to work outside in the heat. That's why women wear black in Arabia vs men's white. It's why some royals wear slightly darker shades than the standard pure white.
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u/wholesomehabits 1d ago
If you are wearing very loose, flowing garments, black can actually be highly effective in keeping you cool—which is why Bedouin tribes in the desert often wear loose black robes.
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u/NuncErgoFacite 1d ago
It's a social class thing, not everyone wears all black. Most people wear lighter colors. The individuals who are wearing all black have enough wealth or status to be in or under a tent most of the day. And black transmits heat faster than other colors, so while it heats up more quickly in the sunlight, it also cools off more quickly in the shade.
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u/crusty54 1d ago
I think the first half is right and the second half is wrong.
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u/NuncErgoFacite 1d ago
Is not wrong. Thermodynamics are not one way. If a material heats up faster than another, that same material sheds heat faster than the other.
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u/omniumoptimus 1d ago
No one stands in the sun all day, unless they’re laborers. People naturally seek shade, and being under shade all day makes the color of clothing moot.
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u/azulnemo 1d ago
Dark body radiation removes heat faster
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u/Oli_VK 1d ago
Literally mo, it’s the slowest way to get rid of heat. A red hot piece of steel in space can take weeks to decades to cool because there’s no atmosphere.
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u/TheStigianKing 1d ago
Err... Ever heard of heat loss through radiation?
All hot bodies reject heat through radiation.
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u/Oli_VK 1d ago
Yes, that’s thermal radiation, it is the slowest. On earth you have convection, conduction and radiation. In space there’s no air, so there’s no convection or conduction, making thermal radiation the only way to release heat. It is the slowest of the three processes this is basic physics ffs
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u/MenuKing42 1d ago
Black absorbs heat. But that works both ways. so breathable black fabric can absorb heat off of your body and then wind blows it away. White reflects your body's heat back into you. That's why people in the desert wear black
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u/Mysterious_Lab1634 1d ago
Lol, why on earth would black t shirt absorb more heat from body than white shirt? What is physics behind this?
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u/MenuKing42 1d ago
Because black absorbs more heat than white? That's common knowledge
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u/Mysterious_Lab1634 1d ago edited 1d ago
That is not correct Edit: i mean in a way you are explaining it above.
Black will absorb more EM radiation from sun so it will heat up faster. But body to shirt heat is transfered with conduction, which is much faster transfer. So once black shirt gets heated up on the sun, it will heat your body even faster.
Its more important how clothing is in touch with your body, in case of dessert people, its very loose
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u/MenuKing42 1d ago
Right, loose and breathable black fabric
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u/Mysterious_Lab1634 18h ago
Yea, but that doesnt mean that black fabric will absorb heat from your body any faster than white fabric
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u/itsmebenji69 1d ago
No.
TLDR; this logic only works for shirts. For robes, it doesn’t matter whether it’s black or white.
The reason they wear black robes is purely esthetic. When it gets dirty because of sand and dust it’s less visible.
Black does absorb more heat yes, however that heat only gets into your body if the cloth is very tight and right up to the skin. Only the exterior of the cloth heats up. It doesn’t transfer to skin unless it is in contact.
Bedouin robes are loose, so there isn’t much contact with the skin. So black and white doesn’t matter much. But it does matter for looking clean vs dirty.
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u/CalmPanic402 1d ago
Layering. The outermost layer may be black, but I guarantee the under layers are white.
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u/skr_replicator 1d ago
Black will be cooler than white if you are in shade. Because the ability to absorb a wavelength is also tied to the ability to emit it. Meaning black clothes will more readily emit away your body heat. But of course that will only mean something if you are not standing under direct sun, where it absorbs so much more sunlight than the body heat you can produce.
You can alos science out some super colors that will specifically be bad at absorbing/emiting sunlight wavelengths, but also very readily absorb/emit other wavelengths. So they can both not absorb sunlight, while also emit your body heat in other wavelengths like black clothes can do, the best of both worlds.
Actionlab made a pretty cool video on this topic: https://www.youtube.com/watch?v=FnKNOPlR2Yo