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Wearing black in a desert

  1. Feb 10, 2012 #1
    I understand that the color black is a really good emitter of heat, but why do people in the desert (especially in the middle east) wear loose fitting black robes? Would not the black color absorb more heat than it emits during the daytime hours?
     
  2. jcsd
  3. Feb 10, 2012 #2
    It's probably a bad idea to wear black robes but there must be some reason.

    All I can say is that most of the pictures I have seen show people wearing light colors.
     
  4. Feb 11, 2012 #3
    Here is a pic
     

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  5. Feb 11, 2012 #4
    The absorbed heat sets up convection currents.Warm air rises and leaves the top of the clothing and this is replaced by cooler air which enters the bottom of the clothing.It's like a solar powered fan.
     
  6. Feb 11, 2012 #5
    If you have seen the movie 'Lawrence of Arabia' you will have noticed how cool Omar
    Shariff appears in black, while Lawrence (Peter O'toole) would look like a dork.....so in the movie he
    wore the white of the another tribe....

    Actually, the above is a weak attempt at humor....and you can see actual photos here
    where it seems Lawrence also wore black, unlike the movie:
    http://en.wikipedia.org/wiki/Lawrence_of_Arabia

    I wonder if black was considered more menacing in appearance....lots of warrier garb was based on intimidation....Or maybe that color material was more readily available? Or did that show how tough groups like the Bedouin were to their peers?

    Dadface may be right about convection, but since the clothing appears generally snug at the neck and shoulders it would seem to trap more heat than it releases. Why snugly wrap the head in black?
     
    Last edited: Feb 11, 2012
  7. Feb 11, 2012 #6
    Well, who knows...there are cold deserts around the world, too, you know? Not all are burning hot or sunny...maybe this picture is of a desert way far from the equator and high altitude...
     
  8. Feb 11, 2012 #7
    ...or early in the morning
     
  9. Feb 11, 2012 #8
    I was replying to the first post where kjamha stated that the clothing was "loose fitting".Now ,having had a look at the picture, I agree that the clothing shown appears to be "snug".My guess is that the clothing is adjustable and can be tightened up when the temperature drops.Also,extra and or different items of clothing are probably worn depending on the temperature.
     
  10. Feb 11, 2012 #9

    cepheid

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    Black things tend to emit just as much as they absorb (a good absorber is a good emitter). What effect this has on cooling the body, I do not know, but I did find this article:

    http://www.straightdope.com/columns/read/1886/does-black-clothing-keep-you-cooler

    Comments???
     
  11. Feb 11, 2012 #10

    nsaspook

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    Just think how crappy you would look wearing white after working in dirt all day. I can tell you from personal experience, the black fabric hides a lot of "smelly" dirt.
     
  12. Feb 11, 2012 #11
    cepheid, the article was great - So it seems if it is a breezy hot day, it would be better to wear black clothing vs. white. Would anyone out there refute this article? It does seem counter intuitive.
     
  13. Feb 12, 2012 #12

    BruceW

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    cepheid's right that black clothing would absorb and emit heat better than white clothing. (Hence the term 'blackbody radiation'). I'm going to go out on a limb and say that the human body will always have a greater temperature than the surroundings (since the body generates its own heat), so in this case it is good to wear black clothing because it will allow heat to flow easier, thereby cooling the person down. Just an educated guess, but who knows, it might be right :)

    But I don't know why it would be useful to wear snug clothing... I would have guessed loose-fitting is better, so that air can circulate easier, carrying away heat from the body.
     
  14. Feb 12, 2012 #13
    Bruce...where are you from? Not from any hot place, I presume. I am from the Sonoran desert and my summers included daily temperatures higher than body temperature. In celcius body temperature is 37.5; my summers included temperatures from 38 to 48...one time I even remember a 52.
     
  15. Feb 12, 2012 #14
    Sounds like the article has the answer.....

    When crossing the great Nefu (Negev)desert in the movie, the warrior group and Lawrence rested during one brutally hot section...but oddly did not loosen their garb...instead they were shown holding sticks vertically or one end stuck in the sand...... with white material 'tent's formed above their heads for shade....
     
  16. Feb 12, 2012 #15

    cepheid

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    Off topic, but I'll chime in with agreement here. I'm from a very cold place as you can see from my profile. But I do remember landing at Dubai airport at midnight one night at the end of August. The outside temperature was +36°C at that time. This rose to +42°C to +45°C during the daytime when the sun was actually out.
     
  17. Feb 12, 2012 #16

    NascentOxygen

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    It's a good question, and one to which I have never had a satisfactory answer. Too many if's, but's and maybe's.

    If you consider an open weave, like fine netting, then perhaps light (IR, visible or UV) could penetrate deeper through reflection/s off white fibres? Whereas if the fibre were black, only those rays directed through the gaps between fibres would get in to heat beneath the robe.

    Relatives of mine lived in the Sahara for a couple of years, with a community that wore black dyed robes. The dye is actually a deep blue, and a tiny amount comes out of the fibre and stains their skin. The people are referred to by others as the blue people because of this blue hue to their skin. In this community, it was the men who wore a full head covering with blue gauze to see through. In the market the men would recognize each other by the children accompanying them; the women stayed in the home.
     
  18. Feb 12, 2012 #17

    BruceW

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    Yeah, I'm from England, so we are always trying to keep warm. In fact, there is snow on the ground outside right now. I had a quick look on wikipedia (always my first point of call), and it said that when the surrounding temperature is greater than body temperature, then the only way the body can lose heat is by evaporation of fluid from the skin. (Which makes sense because net radiation and conduction is going to cause heat to flow into the body). So I would say that it would be best to wear clothing that minimises the flow of heat. This would explain why you should wear snug clothing. (But on the other hand, this might restrict evaporation). And I would guess it would be best to wear reflective clothing, so I'd say white clothing would be better. Maybe black clothing is worn because of tradition or because its the easiest colour to dye, or some reason not related to keeping people cool!
     
  19. Feb 12, 2012 #18
    That really is quite warm!! I think i've experienced. 35*C before....touching (or exceeding 50 though would be crazy).


    Not sure about an answer. How often peeps in how many deserts wear dark robes? It wouldn't be very effective to wear tight fitting clothes. Imagine wearing dark denim jeans when it's 39*C!!
     
  20. Feb 12, 2012 #19
    Sounds like no one here has been to the Mideast. When I lived in the UAE, which is incredibly hot in the summer, the traditionally clothed men wore white. The women wore black and were veiled, on the occasions when they left the house and went into public. Considering that men call the shots in that culture, I'd conclude that in a very hot sunny climate, white is better than black.
     
  21. Feb 12, 2012 #20

    cepheid

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    Way to NOT read the thread carefully. :tongue2:

    Yes, it is a patriarchal society, and yes, women in many ways are oppressed there. But I do not think that that oppression extends to deliberately trying to make women suffer discomfort for no good reason (which would be sadism). There's just nothing to justify that assertion. The motivation for the burka has to do with the extreme notion that exists in that society of what modesty is. Assuming that the difference in colouration is motivated by practical knowledge of heating and cooling, rather than just being simply cultural (which is a much more likely explanation) is just silly. I think that the Burka is just traditionally dark coloured, and the stereotypical "Arab dude" costume is just traditionally white. There is no explanation other than simply, "that's the way it has always been."

    Besides, we haven't yet established conclusively whether the black, loose flowing burka isn't *better* than the white, loose flowing Arab dude outfit. So using your own tenuous assumptions about another culture to come to some sort of conclusion about physics seems even more unsound.
     
  22. Feb 13, 2012 #21
    You must have across like - Bedouins or Arabs wearing loose black ropes and loose black clothes in deserts.

    This is because this clothing acts like poor man's air conditioner. How ?

    Here is the answer :
    Firstly cloths (black or white) are itself poor conductor of heat. But this reason is negligible though.

    Main reason : The cloths being loose traps air inside them. As we know that air is poor conductor of heat , it prevents the heat to be gained by the body. In other words , it insulates the body. Now the loose cloths are black because black is a good absorber and radiator of heat. When black cloth absorbs heat , it sets up convectional current in the air being trapped inside. Air then becomes lighter but why do you think that there will be one directional movement ? It will expand in all directions. It displaces heavier and cooler air to move in interior thus giving cooling effect to desert traveler. At night also , it does not allow the body heat to be lost. Similarly , what if there were white clothing ?

    It reflects heat and does not develop convectional current and hence will not be of greater cooling effect. During night , the black cloth which has absorbed heat dissipates it in body via air trap. It protects the body from cold breeze.
    Moreover it causes windy air to enter during day , which causes evaporation of sweat faster !
     
    Last edited: Feb 13, 2012
  23. Feb 13, 2012 #22

    NascentOxygen

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    So why do most middle eastern men wear white?

    I was sort of in agreement with you, up until this about black cloth:
    Being black, it will absorb the night chill more quickly than does white.
     
  24. Feb 13, 2012 #23
    Careful with the terms !
    No object absorbs night chill or coldness ! Its about gain or loss of heat which causes sensation of hotness or coldness. When wind strikes the cloth it will be conducted by black and white cloth equally. Nothing is being radiated. From day (when there is radiation) , black has absorbed more heat and will dissipate more heat in air trapped as well at night.

    Is it desert in middle east ? In India and at normal places except deserts , people wear loose and light coloured clothes in summer and dark and tight clothes in winter. That's it.
    :smile:
     
  25. Feb 14, 2012 #24
    Before the days of store-bought clothing, Bedouin men and women wore black because the mohair that they used to weave cloth came from black goats--and still does. I refer you to a verse from the Song of Solomon, "Thy hair is like a flock of goats on the mountainside".

    Today, most Bedouin wear cotton store-bought clothing, and white has become the standard. Black is still the traditional, conservative color and is the color of respectable married women even today.

    White reflects more visible light, but its infrared albedp is usually no different than black colored fabrics. When it comes to reflecting or absorbing body heat, there will be little difference. The loose robes of the Bedouin do circulate air as they move.

    Mohair or wool is still preferred for desert excursions in very hot weather because of its insulating ability. I remember a Bedouin guide remarking that, "If I had known it was going to be this hot, I would have worn my thicker robe!"
     
  26. Feb 14, 2012 #25

    NascentOxygen

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    The heat in the cloth is being radiated into space. Black radiates heat better, so black becomes chilly more quickly. Alpine climbers and arctic explorers seem to prefer white clothing, not dark, even though I think dark would be safer by being more visible if they become partly buried.
    On winter nights, does the interior of a black car chill noticeably faster, when it is parked on the street, compared with a white car?
     
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