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To: Snowshoe who wrote (82007)	2/13/2002 9:01:57 PM
From: E. Charters	Read Replies (1) \| Respond to of 116796

The foil goes on the outside, not the inside, unless your brain is generating an unusual amount of radiation, and you don't want to be spotted by them. Foil, shiny side in, keeps you warm, not cold. If foil were coated black on one side, then in a hot sun, black side in, it would keep you from heating up, if it were a few MM from your skin and convection aided heat loss. Baked potatoes demonstrate this, as they are cooked foil shiny side in. It is only recently that manufacturers of felt liners for rubber foot wear started colouring the felt and making a reflective mesh inside them for thermodynamic efficiency. Such light coloured liners may be used comfortably in temperatures up to 30 to 40 degrees farenheit colder than standard dark liners. The survival space blanket is a reflective mylar skin that can be used to keep warm in sub-zero weather at night. It reflects infra-red back to the body. This was an offshoot of NASA research in the 1960's on keeping astronauts space suits even-temperatured in boiling and freezing space where a sun heated side is 250 degrees hotter than a shaded side. If you want a perfect absorber, it must be black. This is also the perfect radiator by the theory of black-body radiation. The best trade off in a hot environment is to be a good radiator, so you pay the price in absorbance too. It depends on where the most heat is being generated. It turns out that the external generation is not so important as the internal-to-external heat rejection, as heat build-up is to be avoided. So in a hot climate it pays to be black, in general. Rejecting what you absorb, is better than retaining more than you absorb, whatever it is. The problem in a animal is to lose heat, but not too much, depending on the absolute temperature. The animal must be able to generate heat and retain it without too much energy loss, in an environment colder than its body, or lose heat without too much water loss in an environment hotter than its body. A camel adapts because it can let its average body temperature soar and not lose water or overheat its brain or organs. Literally, a camel will not sweat even at 105 degrees internal temperature. An animal adapted for hot climates will be a good radiator-absorber, so must be adapted to losing heat. Skin area must be large and pores must be numerous. Ratio of skin area to weight is best for a small animal. Finally the animal must be smart enough to stay out of the hot sun or come in out of the rain. Humans are permanently adapted to their thermodynamic environment. This cannot be co-incidental. White nordic people have 2/3's the skin area of a black person for the same body weight. They also have far fewer pores per square inch of body area. In addition they are covered abundantly with a layer of invisible fine cilia hair that keeps outer cells warm. Their white skin is black to ultraviolet light which is far more abundant than infrared in the low sun northern latitudes. In this the white skinned person can absorb low sunlight and be warmed, and not lose the heat, because of being a poor radiator of infrared. Some biologists have spoken of skin colour differences as being a phenotype instead of a genotype, which would imply that skin colour has no raison d'etre within the environment and thus is purely an accident, creating a varietal species with no reason. I doubt that nature is that capricious for any distinction. There is a reason to all things. Phenotyping is thus rejected as being a theory with no supporting evidence. These phenotype biologists ignore physics' and thermodynamics' powerful necessities as being causitive and also ignore the effects of the evident colour differences being co-incidentalwith survival in vastly different environments, which is more than co-incidental, it is a smoking thermodyamic gun. EC<:-}