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Name: Jon
Status: student
Age: 16
Location: N/A
Country: N/A
Date: 2001


Question:
hello, We all know that white reflects heat while black absorbs most heat. In the desert wearing a black robe would absorb more heat than a white one (naturally), and wearing a black robe could increase temperatures inside by about 6 degrees. Why do people wear black robes in the desert?


Replies:
Some assumptions need validation:

1. Who says few/some/most/all people in the desert wear black robes -- or have we been taking "Lawrence of Arabia" too seriously?

2. "Black" and "White" apply to the absorption / reflection of visible light. It says nothing about the absorption / reflection of infrared, which might be a more important factor.

3. It is assumed that the "black" and "white" fabric are the same type material woven in the same way, etc. This point may not be correct. A black loosely knit fabric may well be "cooler" than a tightly knit white fabric. It would allow the fabric to "breathe" better.

4. Other issues than the coolest garment may be important. For example: Are there religious or cultural reasons for wearing one color vs. another? If we believe the newspaper and magazine photos, it would appear that most people in the desert wear turbans rather than loose fitting headgear. Certainly this practice is not consistent with keeping cool since most body heat is lost from the head.

5. If the color of the dress is important, then certainly the color of the skin is equally or more so. However -- although this is a generalization -- people living in hot climates tend to be dark skinned, and people who live in cold climates tend to be light skinned. This does not make sense, does it?

Need more data before any conclusions can be made about this inquiry.

Vince Calder


I am going to guess...These things are usually not just for one reason. First off some wear white , some wear black...even in the same tribe. Here are some factors that will come into play:

Availability of color fabrics
Cost
Personal preference
Custom
Thickness of the fabric...layers

I recently saw a special on desert nomads of the African desert and some wore white while other wore black. Also, I am not at all sure I would accept the 6 degree estimate...It seems possible that the color will matter much less in the multiple air layer that the robes assume. The outermost layer would certainly absorb more heat but then it would have to be conducted to through the inner layer(s). Here is a scenario. I wear a thin tee shirt on a sunny day..if it is black I notice the difference form white. If I then wear a tee shirt and a black shirt over it...it makes less of a difference.

Peter Faletra Ph.D.
Assistant Director
Science Education
Office of Science
Department of Energy



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